The semiconductor industry is converging on 3.5D as the next best option in advanced packaging, a hybrid approach that includes stacking logic chiplets and bonding them separately to a substrate shared by other components.

This assembly model satisfies the need for big increases in performance while sidestepping some of the thorniest issues in heterogeneous integration. It establishes a middle ground between 2.5D, which already is in widespread use inside of data centers, and full 3D-ICs, which the chip industry has been struggling to commercialize for the better part of a decade.

A 3.5D architecture offers several key advantages:

• It creates enough physical separation to effectively address thermal dissipation and noise.
• It provides a way to add more SRAM into high-speed designs. SRAM has been the go-to choice for processor cache since the mid-1960s, and remains an essential element for faster processing. But SRAM no longer scales at the same rate as digital transistors, so it is consuming more real estate (in percentage terms) at each new node. And because the size of a reticle is fixed, the best available option is to add area by stacking chiplets vertically.
• By thinning the interface between processing elements and memory, a 3.5D approach also can shorten the distances that signals need to travel and greatly improve processing speeds well beyond a planar implementation. This is essential with large language models and AI/ML, where the amount of data that needs to be processed quickly is exploding.

Chipmakers still point to fully integrated 3D-ICs as the best performing alternative to a planar SoC, but packing everything into a 3D configuration makes it harder to deal with physical effects. Thermal dissipation is probably the most difficult to contend with. Workloads can vary significantly, creating dynamic thermal gradients and trapping heat in unexpected places, which in turn reduce the lifespan and reliability of chips. On top of that, power and substrate noise become more problematic at each new node, as do concerns about electromagnetic interference.

“What the market has adopted first is high-performance chips, and those produce a lot of heat,” said Marc Swinnen, director of product marketing at Ansys. “They have gone for expensive cooling systems with a huge number of fans and heat sinks, and they have opted for silicon interposers, which arguably are some of the most expensive technologies for connecting chips together. But it also gives the highest performance and is very good for thermal because it matches the coefficient of thermal expansion. Thermal is one of the big reasons that’s been successful. In addition to that, you may want bigger systems with more stuff that you can’t fit on one chip. That’s just a reticle-size limitation. Another is heterogeneous integration, where you want multiple different processes, like an RF process or the I/O, which don’t need to be in 5nm.”

A 3.5D assembly also provides more flexibility to add additional processor cores, and higher yield because known good die can be manufactured and tested separately, a concept first pioneered by Xilinx in 2011 at 28nm.

3.5D is a loose amalgamation of all these approaches. It can include two to three chiplets stacked on top of each other, or even multiple stacks laid out horizontally.

“It’s limited vertical, and not just for thermal reasons,” said Bill Chen, fellow and senior technical advisor at ASE Group. “It’s also for performance reasons. But thermal is the limiting factor, and we’ve talked about many different materials to help with that — diamond and graphene — but that limitation is still there.”

This is why the most likely combination, at least initially, will be processors stacked on SRAM, which simplifies the cooling. The heat generated by high utilization of different processing elements can be removed with heat sinks or liquid cooling. And with one or more thinned out substrates, signals will travel shorter distances, which in turn uses less power to move data back and forth between processors and memory.

“Most likely, this is going to be logic over memory on a logic process,” said Javier DeLaCruz, fellow and senior director of Silicon Ops Engineering at Arm. “These are all contained within an SoC normally, but a portion of that is going to be SRAM, which does not scale very well from node to node. So having logic over memory and a logic process is really the winning solution, and that’s one of the better use cases for 3D because that’s what really shortens your connectivity. A processor generally doesn’t talk to another processor. They talk to each other through memory, so having the memory on a different floor with no latency between them is pretty attractive.”

The SRAM doesn’t necessarily have to be at the same node as the processors advanced node, which also helps with yield, and reliability. At a recent Samsung Foundry event, Taejoong Song, the company’s vice president of foundry business development, showed a roadmap of a 3.5D configuration using a 2nm chiplet stacked on a 4nm chiplet next year, and a 1.4nm chiplet on top of a 2nm chiplet in 2027.

Fig. 1: Samsung’s heterogeneous integration roadmap showing stacked DRAM (HBM), chiplets and co-packaged optics. Source: Samsung Foundry

Intel Foundry’s approach is similar in many ways. “Our 3.5D technology is implemented on a substrate with silicon bridges,” said Kevin O’Buckley, senior vice president and general manager of Foundry Services at Intel. “This is not an incredibly costly, low-yielding, multi-reticle form-factor silicon, or even RDL. We’re using thin silicon slices in a much more cost-efficient fashion to enable that die-to-die connectivity — even stacked die-to-die connectivity — through a silicon bridge. So you get the same advantages of silicon density, the same SI (signal integrity) performance of that bridge without having to put a giant monolithic interposer underneath the whole thing, which is both cost- and capacity-prohibitive. It’s working. It’s in the lab and it’s running.”

Fig. 2: Intel’s 3.5D model. Source: Intel

The strategy here is partly evolutionary — 3.5D has been in R&D for at least several years — and part revolutionary, because thinning out the interconnect layer, figuring out a way to handle these thinner interconnect layers, and how to bond them is still a work in progress. There is a potential for warping, cracking, or other latent defects, and dynamically configuring data paths to maximize throughput is an ongoing challenge. But there have been significant advances in thermal management on two- and three-chiplet stacks.

“There will be multiple solutions,” said C.P. Hung, vice president of corporate R&D at ASE. “For example, besides the device itself and an external heat sink, a lot of people will be adding immersion cooling or local liquid cooling. So for the packaging, you can probably also expect to see the implementation of a vapor chamber, which will add a good interface from the device itself to an external heat sink. With all these challenges, we also need to target a different pitch. For example, nowadays you see mass production with a 45 to 40 pitch. That is a typical bumping solution. We expect the industry to move to a 25 to 20 micron bump pitch. Then, to go further, we need hybrid bonding, which is a less than 10 micron pitch.”

Fig. 3: Today’s interposers support more than 100,000 I/Os at a 45m pitch. Source: ASE

Hybrid bonding solves another thorny problem, which is co-planarity across thousands of micro-bumps. “People are starting to realize that the densities we’re interconnecting require a level of flatness, which the guys who make traditional things to be bonded are having a hard time meeting with reasonable yield,” David Fromm, COO at Promex Industries. “That makes it hard to build them, and the thinking is, ‘So maybe we’ve got to do something else.’ You’re starting to see some of that.”

Taming the Hydra
Managing heat remains a challenge, even with all the latest advances and a 3.5D assembly, but the ability to isolate the thermal effects from other components is the best option available today, and possibly well into the future. Still, there are other issues to contend with. Even 2.5D isn’t easy, and a large percentage of the 2.5D implementations have been bespoke designs by large systems companies with very deep pockets.

One of the big remaining challenges is closing timing so that signals arrive at the right place at the right fraction of a second. This becomes harder as more elements are added into chips, and in a 3.5D or 3D-IC, this can be incredibly complex.

“Timing ultimately is the key,” said Sutirtha Kabir, R&D director at Synopsys. “It’s not guaranteed that at whatever your temperature is, you can use the same library for timing. So the question is how much thermal- and IR-aware timing do you have to do? These are big systems. You have to make sure your sign-off is converging. There are two things coming out. There are a bunch of multi-physics effects that are all clumped together. And yes, you could traditionally do one at a time as sign-off, but that isn’t going to work very well. You need to figure out how to solve these problems simultaneously. Ultimately, you’re doing one design. It’s not one for thermal, one for IR, one for timing. The second thing is the data is exploding. How do you efficiently handle the data, because you cannot wait for days and days of runtime and simulation and analysis?”

Physically assembling these devices isn’t easy, either. “The challenge here is really in the thermal, electrical, and mechanical connection of all these various die with different thicknesses and different coefficients of thermal expansion,” said Intel’s O’Buckley. “So with three die, you’ve got the die and an active base, and those are substantially thinned to enable them to come together. And then EMIB is in the substrate. There’s always intense thermal-mechanical qualification work done to manage not just the assembly, but to ensure in the final assembly — the second-level assembly when this is going through system-level card attach — that this thing stays together.”

And depending upon demands for speed, the interconnects and interconnect materials can change. “Hybrid bonding gives you, by far, the best signal and power density,” said Arm’s DeLaCruz. “And it gives you the best thermal conductivity, because you don’t have that underfill that you would otherwise have to put in between the die, which is a pretty significant barrier. This is likely where the industry will go. It’s just a matter of having the production base.”

Hybrid bonding has been used for years for image sensors using wafer-on-wafer connections. “The tricky part is going into the logic space, where you’re moving from wafer-on-wafer to a die-on-wafer process, which is more complex,” DeLaCruz said. “While it currently would cost more, that’s a temporary problem because there’s not much of an installed base to support it and drive down the cost. There’s really no expensive material or equipment costs.”

Toward mass customization
All of this is leading toward the goal of choosing chiplets from a menu and then rapidly connecting them into some sort of architecture that is proven to work. That may not materialize for years. But commercial chiplets will show up in advanced designs over the next couple years, most likely in high-bandwidth memory with a customized processor in the stack, with more following that path in the future.

At least part of this will depend on how standardized the processes for designing, manufacturing, and testing become. “We’re seeing a lot of 2.5D from customers able to secure silicon interposers,” said Ruben Fuentes, vice president for the Design Center at Amkor Technology. “These customers want to place their chiplets on an interposer, then the full module is placed on a flip-chip substrate package. We also have customers who say they either don’t want to use a silicon interposer or cannot secure them. They prefer an RDL interconnect with S-SWIFT or with S-Connect, which serves as an interposer in very dense areas.”

But with at least a third of these leading designs only for internal use, and the remainder confined to large processor vendors, the rest of the market hasn’t caught up yet. Once it does, that will drive economies of scale and open the door to more complete assembly design kits, commercial chiplets, and more options for customization.

“Everybody is generally going in the same direction,” said Fuentes. “But not everything is the same height. HBMs are pre-packaged and are taller than ICs. HBMs could have 12 or 16 ICs stacked inside. It makes a difference from a co-planarity and thermal standpoint, and metal balancing on different layers. So now vendors are having a hard time processing all this data because suddenly you have these huge databases that are a lot bigger than the standard packaging databases. We’re seeing bridges, S-Connect, SWIFT, and then S-SWIFT. This is new territory, and we’re seeing a performance gap in the packaging tools. There’s work that needs to be done here, but software vendors have been very proactive in finding solutions. Additionally, these packages need to be routed. There is limited automated routing, so a good amount of interactive routing is still required, so it takes a lot of time.”

Fig. 4: Packaging roadmap showing bridge and hybrid bonding connections for modules and chiplets, respectively. Source: Amkor Technology

What’s missing
The key challenges ahead for 3.5D are proven reliability and customizability — requirements that are seemingly contradictory, and which are beyond the control of any single company. There are four major pieces to making all of this work.

EDA is the first important piece of the puzzle, and the challenge extends just beyond a single chip. “The IC designers have to think about a lot of things concurrently, like thermal, signal integrity, and power integrity,” said Keith Lanier, technical product management director at Synopsys. “But even beyond that, there’s a new paradigm in terms of how people need to work. Traditional packaging folks and IC designers need to work closely together to make these 3.5D designs successful.”

It’s not just about doing more with the same or fewer people. It’s doing more with different people, too. “It’s understanding the architecture definition, the functional requirements, constraints, and having those well-defined,” Lanier said. “But then it’s also feasibility, which includes partitioning and technology selection, and then prototyping and floor-planning. This is lots and lots of data that is required to be generated, and you need analysis-driven exploration, design, and implementation. And AI will be required to help designers and system design teams manage the sheer complexity of these 3.5D designs.”

Process/assembly design kits are a second critical piece, and this is likely to be split between the foundries and the OSATs. “If the customer wants a silicon interposer for a 2.5D package, it would be up to the foundry that’s going to manufacture the interposer to provide the PDK. We would provide the PDK for all of our products, such as S-SWIFT and S-Connect,” said Amkor’s Fuentes.

Setting realistic parameters is the third piece of the puzzle. While the type of processing elements and some of the analog functions may change — particularly those involving power and communication — most of the components will remain the same. That determines what can be pre-built and pre-tested, and the speed and ease of assembly.

“A lot of the standards that are being deployed, like UCIe interfaces and HBM interfaces are heading to where 20% is customization and 80% is on the shelf,” said Intel’s O’Buckley. “But we aren’t there today. At the scale that our customers are deploying these products, the economics of spending that extra time to optimize an implementation is a decimal point. It’s not leveraging 80/20 standards. We’ll get there. But most of these designs you can count on your fingers and toes because of the cost and scale required to do them. And until the infrastructure for standards-based chiplets gets mature, the barrier of entry for companies that want to do this without that scale is just too high. Still, it is going to happen.”

Ensuring processes are consistent is the fourth piece of the puzzle. The tools and the individual processes don’t need to change. “The customer has a ‘target’ for the outcome they want for a particular tool, which typically is a critical dimension measured by a metrology tool,” said David Park, vice president of marketing at Tignis. “As long as there is some ‘measurement’ that determines the goodness of some outcome, which typically is the result of a process step, we can either predict the bad outcome — and engineers have to take some corrective or preventive action — or we can optimize the recipe of that tool in real time to keep the result in the range they want.”

Park noted there is a recipe that controls the inputs. “The tool does whatever it is supposed to do,” he said. “Then you measure the output to see how far you deviated from the acceptable output.”

The challenge is that inside of a 3.5D system, what is considered acceptable output is still being defined. There are many processes with different tolerances. Defining what is consistent enough will require a broad understanding of how all the pieces work together under specific workloads, and where the potential weaknesses are that need to be adjusted.

“One of the problems here is as these densities get higher and the copper pillars get smaller, the amount of space you need between the pillar and the substrate have to be highly controlled,” said Dick Otte, president and CEO of Promex. “There’s a conflict — not so much with how you fabricate the chip, because it usually has the copper pillars on it — but with the substrate. A lot of the substrate technologies are not inherently flat. It’s the same issue with glass. You’ve got a really nice flat piece of glass. The first thing you’re going to do is put down a layer of metal and you’re going to pattern it. And then you put down a layer of dielectric, and suddenly you’ve got a lump where the conductor goes. And now, where do you put the contact points? So you always have the one plan which is going to be the contact point where all the pillars come in. But what if I only need one layer and I don’t need three?”

Conclusion
For the past decade, the chip industry has been trying to figure out a way to balance faster processing, domain-specific designs, limited reticle size, and the enormous cost of scaling an SoC. After investigating nearly every possible packaging approach, interconnect, power delivery method, substrate and dielectric material, 3.5D has emerged as the front runner — at least for now.

This approach provides the chip industry with a common thread on which to begin developing assembly design kits, commercial chiplets, and to fill in the missing tools and services throughout the supply chain. Whether this ultimately becomes a springboard for full 3D-ICs, or a platform on which to use 3D stacking more effectively, remains to be seen. But for the foreseeable future, large chipmakers have converged on a path forward to provide orders of magnitude performance improvements and a way to contain costs. The rest of the industry will be working to smooth out that path for years to come.

Related Reading
Intel Vs. Samsung Vs. TSMC
Foundry competition heats up in three dimensions and with novel technologies as planar scaling benefits diminish.
3D Metrology Meets Its Match In 3D Chips And Packages
Next-generation tools take on precision challenges in three dimensions.
Design Flow Challenged By 3D-IC Process, Thermal Variation
Rethinking traditional workflows by shifting left can help solve persistent problems caused by process and thermal variations.
Floor-Planning Evolves Into The Chiplet Era
Automatically mitigating thermal issues becomes a top priority in heterogeneous designs.

The post 3.5D: The Great Compromise appeared first on Semiconductor Engineering.

Gallium nitride is starting to make broader inroads in the lower-end of the high-voltage, wide-bandgap power FET market, where silicon carbide has been the technology of choice. This shift is driven by lower costs and processes that are more compatible with bulk silicon.

Efficiency, power density (size), and cost are the three major concerns in power electronics, and GaN can meet all three criteria. However, to satisfy all of those criteria consistently, the semiconductor ecosystem needs to develop best practices for test, inspection, and metrology, determining what works best for which applications and under varying conditions.

Power ICs play an essential role in stepping up and down voltage levels from one power source to another. GaN is used extensively today in smart phone and laptop adapters, but market opportunities are beginning to widen for this technology. GaN likely will play a significant role in both data centers and automotive applications [1]. Data centers are expanding rapidly due to the focus on AI and a build-out at the edge. And automotive is keen to use GaN power ICs for inverter modules because they will be cheaper than SiC, as well as for onboard battery chargers (OBCs) and various DC-DC conversions from the battery to different applications in the vehicle.

Fig. 1: Current and future fields of interest for GaN and SiC power devices. Source A. Meixner/Semiconductor Engineering

But to enter new markets, GaN device manufactures need to more quickly ramp up new processes and their associated products. Because GaN for power transistors is a developing process technology, measurement data is critical to qualify both the manufacturing process and the reliability of the new semiconductor technology and resulting product.

Much of GaN’s success will depend on metrology and inspection solutions that offer high throughput, as well as non-destructive testing methods such as optical and X-ray. Electron microscopy is useful for drilling down into key device parameters and defect mechanisms. And electrical tests provide complementary data that assists with product/process validation, reliability and qualification, system-level validation, as well as being used for production screening.

Silicon carbide (SiC) remains the material of choice for very high-voltage applications. It offers better performance and higher efficiency than silicon. But SiC is expensive. It requires different equipment than silicon, it’s difficult to grow SiC ingots, and today there is limited wafer capacity.

In contrast, GaN offers some of the same desirable characteristics as SiC and can operate at even higher switching speeds. GaN wafer production is cheaper because it can be created on a silicon substrate utilizing typical silicon processing equipment other than the GaN epitaxial deposition tool. That enables a fab/foundry with a silicon CMOS process to ramp a GaN process with an engineering team experienced in GaN.

The cost comparison isn’t entirely apples-to-apples, of course. The highest-voltage GaN on the market today uses silicon on sapphire (SoS) or other engineered substrates, which are more expensive. But below those voltages, GaN typically has a cost advantage, and that has sparked renewed interest in this technology.

“GaN-based products increase the performance envelopes relative to the incumbent and mature silicon-based technologies,” said Vineet Pancholi, senior director of test technology at Amkor. “Switching speeds with GaN enable the application in ways never possible with silicon. But as the GaN production volumes ramp, these products have extreme economic pressures. The production test list includes static attributes. However, the transient and dynamic attributes are the primary benefit of GaN in the end application.”

Others agree. “The world needs cheaper material, and GaN is easy to build,” said Frank Heidemann, vice president and technology leader of SET at NI/Emerson Test & Measurement. “Gallium nitride has a huge success in the lower voltages ranges — anything up to 500V. This is where the GaN process is very well under control. The problem now is building in higher voltages is a challenge. In the near future there will be products at even higher voltage levels.”

Those higher-voltage applications require new process recipes, new power IC designs, and subsequently product/process validation and qualification.

GaN HEMT properties
Improving the processes needed to create GaN high-electron-mobility transistors (HEMTs) requires a deep understanding of the material properties and the manufacturing consequences of layering these materials.

The underlying physics and structure of wide-bandgap devices significantly differs from silicon high-voltage transistors. Silicon transistors rely on doping of p and n materials. When voltage is applied at the gate, it creates a channel for current to flow from source to drain. In contrast, wide-bandgap transistors are built by layering thin films of different materials, which differ in their bandgap energy. [2] Applying a voltage to the gate enables an electron exchange between the two materials, driving those electrons along the channel between source and drain.

Fig. 2. Cross-sectional animation of e-mode GaN HEMT device. Source: Zeiss Microscopy

“GaN devices rely on two-dimensional electron gas (2DEG) created at the GaN and AlGaN interface to conduct current at high speed,” said Jiangtao Hu, senior director of product marketing at Onto Innovation. “To enable high electron mobility, the epitaxy process creating complex multi-layer crystalline films must be carefully monitored and controlled, ensuring critical film properties such as thickness, composition, and interface roughness are within a tight spec. The ongoing trend of expanding wafer sizes further requires the measurement to be on-product and non-destructive for uniformity control.”

Fig. 3: SEM cross-section of enhancement-mode GaN HEMT built on silicon which requires a superlattice. Source: Zeiss Microscopy

Furthermore, each layer’s electrical properties need to be understood. “It is of utmost importance to determine, as early as possible in the manufacturing process, the electrical characteristics of the structures, the sheet resistance of the 2DEG, the carrier concentration, and the mobility of carriers in the channel, preferably at the wafer level in a non-destructive assessment,” said Christophe Maleville, CTO and senior executive vice president of innovation at Soitec.

Developing process recipes for GaN HEMT devices at higher operating ranges require measurements taken during wafer manufacturing and device testing, both for qualification of a process/product and production manufacturing. Inspection, metrology, and electrical tests focus on process anomalies and defects, which impact the device performance.

“Crystal defects such as dislocations and stacking faults, which can form during deposition and subsequently be grown over and buried, can create long-term reliability concerns even if the devices pass initial testing,” said David Taraci, business development manager of electronics strategic accounts at ZEISS Research Microscopy Solutions. “Gate oxides can pinch off during deposition, creating voids which may not manifest as an issue immediately.”

The quality of the buffer layer is critical because it affects the breakdown voltage. “The maximum breakdown voltage of the devices will be ultimately limited by the breakdown of the buffer layer grown in between the Si substrate and the GaN channel,” said Soitec’s Maleville. “An electrical assessment (IV at high voltage) requires destructive measurements as well as device isolation. This is performed on a sample basis only.”

One way to raise the voltage limit of a GaN device is to add a ‘gate driver’ which keeps it reliable at higher voltages. But to further expand GaN technology’s performance envelope to higher voltage operation engineers need to comprehend a new GaN device reliability properties.

“We are supporting GaN lifetime validation, which is the prediction of a mission characteristic of lifetime for gallium nitride power devices,” said Emerson’s Heidemann. “Engineers build physics-based failure models of these devices. Next, they investigate the acceleration factors. How can we really make tests and verification properly so that we can assess lifetime health?”

The qualification procedures necessitate life-stressing testing, which duplicates predicated mission profile usage, as well as electrical testing, after each life-stress period. That allows engineers to determine shifts in transistor characteristics and outright failures. For example, life stress periods could start with 4,000 hours and increase in 1,000-hour increments to 12,000 hours, during which time the device is turned on/off with specific durations of ‘on’ times.

“Reliability predictions are based upon application mission profiles,” said Stephanie Watts Butler, independent consultant and vice president of industry and standards in the IEEE Power Electronics Society. “In some cases, GaN is going into a new application, or being used differently than silicon, and the mission profile needs to be elucidated. This is one area that the industry is focused upon together.”

As an example of this effort, Butler pointed to JEDEC JEP186 spec [3], which provides guidelines for specifying the breakdown voltage for GaN HEMT devices. “JEDEC and IEC both are issuing guideline documents for methods for test and characterization of wide-bandgap devices, as well as reliability and qualification procedures, and datasheet parameters to enable wide bandgap devices, including GaN, to ramp faster with higher quality in the marketplace,” she said.

Electrical tests remain essential to screening for both time-zero and reliability-associated defects (e.g. infant mortality and reduced lifetime). This holds true for screening wafers, singulated die, and packaged devices. And test content includes tests specific to GaN HEMT power devices performance specifications and tests more directed at defect detection.

Due to inherent device differences, the GaN test list varies in some significant ways from Si and SiC power ICs. Assessing GaN health for qualification and manufacturing purposes requires both static and dynamic tests (SiC DC and AC). A partial list includes zero gate voltage drain leakage current, rise time, fall time, dynamic RDS_on, and dielectric integrity tests.

“These are very time-intensive measurement techniques for GaN devices,” said Tom Tran, product manager for power discrete test products at Teradyne. “On top of the static measurement techniques is the concern about trapped charge — both for functionality and efficiency — revealed through dynamic RDS_on testing.”

Transient tests are necessary for qualification and production purposes due to the high electron mobility, which is what gives GaN HEMT its high switching speed. “From a test standpoint, static test failures indicate basic processing failures, while transient switching failures indicate marginal or process excursions,” said Amkor’s Vineet Pancholi. “Both tests continue to be important to our customers until process maturity is achieved. With the extended range of voltage, current, and switching operations, mainstream test equipment suppliers have been adding complementary instrumentation capabilities.”

And ATE suppliers look to reduce test time, which reduces cost. “Both static and dynamic test requirements drive very high test times,” said Teradyne’s Tran. “But the GaN of today is very different than GaN from a decade ago. We’re able to accelerate this testing just due to the core nature of our ATE architecture. We think there is the possibility further reducing the cost of test for our customers.”

Tools for process control and quality management
GaN HEMT devices’ reliance on thin-film processes highlights the need to understand the material properties and the nature of the interfaces between each layer. That requires tools for process control, yield management, and failure analysis.

“GaN device performance is highly reflective of the film characteristics used in its manufacture,” said Mike McIntyre, director of software product management at Onto Innovation. “The smallest process variations when it comes to film thickness, film stress, line width or even crystalline make-up, can have a dramatic impact on how the device performs, or even if it is usable in its target market. This lack of tolerance to any variation places a greater burden on engineers to understand the factors that correlate to device performance and its profitability.”

Inspection methods that are non-destructive vary in throughput time and in the level of detail provided for engineers to make decisions. While optical methods are fast and provide full wafer coverage, they cannot accurately classify chemical or structural defects for engineers/technicians to review. In contrast, destructive methods provide the information that’s needed to truly understand the nature of the defects. For example, conductive atomic force microscopy (AFM) probing remains slow, but it can identify electrical nature of a defect. And to truly comprehend crystallographic defects and the chemical nature of impurities, engineers can turn to electron microscopy based methods.

One way to assess thin films is with X-rays. “High resolution X-ray measurements are useful to provide production control of the wafer crystalline quality and defects in the buffer, said Soitec’s Maleville. “Minor changes in composition of the buffer, barrier, or capping layer, as well as their layer thickness, can result in significant deviations in device performance. Thickness of the layers, in particular the top cap, barrier, and spacer layers, are typically measured by XRD. However, the throughput of XRD systems is low. Alternatively, ellipsometry offers a reasonably good throughput measurement with more data points for both development and production mode scenarios.”

Optical techniques have been the standard for thin film assessment in the semiconductor industry. Inspection equipment providers have long been on the continuation improvement always evolving journey to improve accuracy, precision and throughput. Providing better metrology tools helps device makers with process control and yield management.

“Recently, we successfully developed a non-destructive on product measurement capability for GaN epi process monitoring,” said Onto’s Hu. “It takes advantage of our advanced optical film experience and our modeling software to simultaneously measure multi-layer epi film thickness, composition, and interface roughness on product wafers.”

Fig. 4: Metrology measurements on GaN for roughness and for Al concentration. Source: Onto Innovation

Assessing the electrical characteristics — 2DEG sheet resistance, channel carrier mobility, and concentration are required for controlling the manufacturing process. A non-destructive assessment would be an improvement over currently used destructive techniques (e.g. SEM). The solutions used for other power ICs do not work for GaN HEMT. As of today, no one has come up with a commercial solution.

Inspection looks for yield impacting defects, as well as defects that affect wafer acceptance in the case of companies that provide engineered substrates.

“Defect inspection for incoming silicon wafers looks for particles, scratches, and other anomalies that might seed imperfections in the subsequent buffer and crystal growth,” said Antonio Mani, business development manager at Thermo Fisher Scientific. “After the growth of the buffer and termination layers, followed by the growth of the doped GaN layers, another set of inspections is carried out. In this case, it is more focused on the detection of cracks, other macroscopic defects (micropipes, carrots), and looking for micro-pits, which are associated to threading dislocations that have survived the buffer layer and are surfacing at the top GaN surface.”

Mani noted that follow-up inspection methods for Si and GaN devices are similar. The difference is the importance in connecting observations back to post-epi results.

More accurate defect libraries would shorten inspection time. “The lack of standardization of surface defect analysis impedes progress,” said Soitec’s Maleville. “Different tools are available on the market, while defect libraries are still being developed essentially by the different user. This lack of globally accepted method and standard defect library for surface defect analysis is slowing down the GaN surface qualification process.”

Whether it involves a manufacturing test failure or a field return, the necessary steps for determining root cause on a problematic packaged part begins with fault isolation. “Given the direct nature of the bandgap of GaN and its operating window in terms of voltage/frequency/power density, classical methods of fault isolation (e.g. optical emission spectroscopy) are forced to focus on different wavelengths and different ranges of excitation of the typical electrical defects,” said Thermo Fisher’s Mani. “Hot carrier pairs are just one example, which highlights the radical difference between GaN and silicon devices.”

In addition to fault isolation there are challenges in creating a device cross-section with focused-ion beam milling methods.

“Several challenges exist in FA for GaN power ICs,” said Zeiss’ Taraci. “In any completed device, in particular, there are numerous materials and layers present for stress mitigation/relaxation and thermal management, depending on whether we are talking enhancement- or depletion-mode devices. Length-scale can be difficult to manage as you are working with these samples, because they have structures of varying dimension present in close proximity. Many of the structures are quite unique to power GaN and can pose challenges themselves in cross-section and analyses. Beam-milling approaches have to be tailored to prevent heavy re-deposition and masking, and are dependent on material, lattice orientation, current, geometry, etc.”

Conclusion
To be successful in bringing new GaN power ICs to new application space engineers and their equipment suppliers need faster process development and a reduction in overall costs. For HEMT devices, it’s understanding the resulting layers and their material properties. This requires a host of metrology, inspection, test, and failure analysis steps to comprehend the issues, and to provide feedback data from experiments and qualifications for process and design improvements.

References

[1] M. Buffolo et al., “Review and Outlook on GaN and SiC Power Devices: Industrial State-of-the-Art, Applications, and Perspectives,” in IEEE Transactions on Electron Devices, March 2024, open access, https://ieeexplore.ieee.org/document/10388225

[2] High electron mobility transistor (HEMT) https://en.wikipedia.org/wiki/High-electron-mobility_transistor

[3] Guideline to specify a transient off-state withstand voltage robustness indicated in datasheets for lateral GaN power conversion devices, JEP186, version 1.0, December 2021. https://www.jedec.org/standards-documents/docs/jep186

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The post Driving Cost Lower and Power Higher With GaN appeared first on Semiconductor Engineering.

Okinawa Institute of Science and Technology proposed a new EUV litho technology using only four reflective mirrors and a new method of illumination optics that it claims will use 1/10 the power and cost half as much as existing EUV technology from ASML.

Applied Materials may not receive expected U.S. funding to build a $4 billion research facility in Sunnyvale, CA, due to internal government disagreements over how to fund chip R&D, according to Bloomberg.

SEMI published a position paper this week cautioning the European Union against imposing additional export controls to allow companies, encouraging them to  be “as free as possible in their investment decisions to avoid losing their agility and relevance across global markets.” SEMI’s recommendations on outbound investments are in response to the European Economic Security Strategy and emphasize the need for a transparent and predictable regulatory framework.

The U.S. may restrict China’s access to HBM chips and the equipment needed to make them, reports Bloomberg. Today those chips are manufactured by two Korean-based companies, Samsung and SK hynix, but U.S.-based Micron expects to begin shipping 12-high stacks of HBM3E in 2025, and is currently working on HBM4.

Synopsys executive chair and founder Dr. Aart de Geus was named the winner of the Semiconductor Industry Association’s Robert N. Noyce Award. De Geus was selected due to his contributions to EDA technology over a career spanning more than four decades.

The top three foundries plan to implement high-NA EUV lithography as early as 2025 for the 18 angstrom generation, but the replacement of single exposure high-NA (0.55) over double patterning with standard EUV (NA = 0.33) depends on whether it provides better results at a reasonable cost per wafer.

Quick links to more news:

Global
In-Depth
Market Reports and Earnings
Education and Training
Security
Product News
Research
Events and Further Reading

Global

Belgium-based Imec released part 2 of its chiplets series, addressing testing strategies and standardization efforts, as well as guidelines and research “towards efficient ESD protection strategies for advanced 3D systems-on-chip.”

Also in Belgium, BelGan, maker of GaN chips, filed for bankruptcy according to the Brussels Times.

TSMC‘s Dresden, Germany, plant will break ground this month.

The UK will dole out more than £100 million (~US $128 million) in funding to develop five new quantum research hubs in Glasgow, Edinburgh, Birmingham, Oxford, and London.

MassPhoton is opening Hong Kong‘s first ultra-high vacuum GaN epitaxial wafer pilot line and will establish a GaN research center.

Infineon completed the sale of its manufacturing sites in the Philippines and South Korea to ASE.

Israel-based RAAAM Memory Technologies received a €5.25 million grant from the European Innovation Council (EIC) to support the development and commercialization of its innovative memory solutions. This funding will enable RAAAM to advance its research in high-performance and energy-efficient memory technologies, accelerating their integration into various applications and markets.

In-Depth

Semiconductor Engineering published its Automotive, Security and Pervasive Computing newsletter this week, featuring these top stories and video:

• Chip Security Now Depends On Widening Supply Chain
• Defining Chip Threat Models To Determining Security Risks
• Post-Quantum Computing Threatens Fundamental Transport Protocols

And:

• Where Power Savings Really Count
• Making Electronics More Efficient (video)

Market Reports and Earnings

The semiconductor equipment industry is on a positive trajectory in 2024, with moderate revenue growth observed in Q2 after a subdued Q1, according to a new report from Yole Group. Wafer Fab Equipment revenue is projected to grow by 1.3% year-on-year, despite a 12% drop in Q1. Test equipment lead times are normalizing, improving order conditions. Key areas driving growth include memory and logic capital expenditures and high-bandwidth memory demand.

Worldwide silicon wafer shipments increased by 7% in Q2 2024, according to SEMI‘s latest report. This growth is attributed to robust demand from multiple semiconductor sectors, driven by advancements in AI, 5G, and automotive technologies.

The RF GaN market is projected to grow to US $2 billion by 2029, a 10% CAGR, according to Yole Group.

Counterpoint released their Q2 smartphone top 10 report.

Renesas completed their acquisition of EDA firm Altium, best known for its EDA platform and freeware CircuitMaker package.

It’s earnings season and here are recently released financials in the chip industry:

AMD  Advantest   Amkor   Ansys  Arteris   Arm   ASE   ASM   ASML
Cadence  IBM   Intel   Lam Research   Lattice   Nordson   NXP   Onsemi 
Qualcomm   Rambus  Samsung    SK Hynix   STMicro   Teradyne    TI  
Tower  TSMC    UMC  Western Digital

Industry stock price impacts are here.

Education and Training

Rochester Institute of Technology is leading a new pilot program to prepare community college students in areas such as cleanroom operations, new materials, simulation, and testing processes, with the intent of eventual transfer into RIT’s microelectronic engineering program.

Purdue University inked a deal with three research institutions — University of Piraeus, Technical University of Crete, and King’s College London —to develop joint research programs for semiconductors, AI and other critical technology fields.

The European Chips Skills Academy formed the Educational Leaders Board to help bridge the talent gap in Europe’s microelectronics sector.  The Board includes representatives from universities, vocational training providers, educators and research institutions who collaborate on strategic initiatives to strengthen university networks and build academic expertise through ECSA training programs.

Security

The Cybersecurity and Infrastructure Security Agency (CISA) is encouraging Apple users to review and apply this week’s recent security updates.

Microsoft Azure experienced a nearly 10 hour DDoS attack this week, leading to global service disruption for many customers.  “While the initial trigger event was a Distributed Denial-of-Service (DDoS) attack, which activated our DDoS protection mechanisms, initial investigations suggest that an error in the implementation of our defenses amplified the impact of the attack rather than mitigating it,” stated Microsoft in a release.

NIST published:

• “Recommendations For Increasing U.S. Participation and Leadership in Standards Development,” a report outlining cybersecurity recommendations and mitigation strategies.
• Final guidance documents and software to help improve the “safety, security and trustworthiness of AI systems.”
• Cloud Computing Forensic Reference Architecture guide.

Delta Air Lines plans to seek damages after losing $500 million in lost revenue due to security company CrowdStrike‘s software update debacle.  And shareholders are also angry.

Recent security research:

• Physically Secure Logic Locking With Nanomagnet Logic (UT Dallas)
• WBP: Training-time Backdoor Attacks through HW-based Weight Bit Poisoning (UCF)
• S-Tune: SOT-MTJ Manufacturing Parameters Tuning for Secure Next Generation of Computing ( U. of Arizona, UCF)
• Diffie Hellman Picture Show: Key Exchange Stories from Commercial VoWiFi Deployments (CISPA, SBA Research, U. of Vienna)

Product News

Lam Research introduced a new version of its cryogenic etch technology designed to enhance the manufacturing of 3D NAND for AI applications. This technology allows for the precise etching of high aspect ratio features, crucial for creating 1,000-layer 3D NAND.

Fig.1: 3D NAND etch. Source: Lam Research

Alphawave Semi launched its Universal Chiplet Interconnect Express Die-to-Die IP. The subsystem offers 8 Tbps/mm bandwidth density and supports operation at 24 Gbps for D2D connectivity.

Infineon introduced a new MCU series for industrial and consumer motor controls, as well as power conversion system applications. The company also unveiled its new GoolGaN Drive product family of integrated single switches and half-bridges with integrated drivers.

Rambus released its DDR5 Client Clock Driver for next-gen, high-performance desktops and notebooks. The chips include Gen1 to Gen4 RCDs, power management ICs, Serial Presence Detect Hubs, and temperature sensors for leading-edge servers.

SK hynix introduced its new GDDR7 graphics DRAM. The product has an operating speed of 32Gbps, can process 1.5TB of data per second and has a 50% power efficiency improvement compared to the previous generation.

Intel launched its new Lunar Lake Ultra processors. The long awaited chips will be included in more than 80 laptop designs and has more than 40 NPU tera operations per second as well as over 60 GPU TOPS delivering more than 100 platform TOPS.

Brewer Science achieved recertification as a Certified B Corporation, reaffirming its commitment to sustainable and ethical business practices.

Panasonic adopted Siemens’ Teamcenter X cloud product lifecycle management solution, citing Teamcenter X’s Mendix low-code platform, improved operational efficiency and flexibility for its choice.

Keysight validated its 5G NR FR1 1024-QAM demodulation test cases for the first time. The 5G NR radio access technology supports eMBB and was validated on the 3GPP TS 38.521-4 test specification.

Research

In a 47-page deep-dive report, the Center for Security and Emerging Technology delved into all of the scientific breakthroughs from 1980 to present that brought EUV lithography to commercialization, including lessons learned for the next emerging technologies.

Researchers at the Paul Scherrer Institute developed a high-performance X-ray tomography technique using burst ptychography, achieving a resolution of 4nm. This method allows for non-destructive imaging of integrated circuits, providing detailed views of nanostructures in materials like silicon and metals.

MIT signed a four-year agreement with the Novo Nordisk Foundation Quantum Computing Programme at University of Copenhagen, focused on accelerating quantum computing hardware research.

MIT’s Research Laboratory of Electronics (RLE) developed a mechanically flexible wafer-scale integrated photonics fabrication platform. This enables the creation of flexible photonic circuits that maintain high performance while being bendable and stretchable. It offers significant potential for integrating photonic circuits into various flexible substrate applications in wearable technology, medical devices, and flexible electronics.

The Naval Research Lab identified a new class of semiconductor nanocrystals with bright ground-state excitons, emphasizing an important advancement in optoelectronics.

Researchers from National University of Singapore developed a novel method, known as tension-driven CHARM3D,  to fabricate 3D self-healing circuits, enabling the 3D printing of free-standing metallic structures without the need for support materials and external pressure.

Find more research in our Technical Papers library.

Events and Further Reading

Find upcoming chip industry events here, including:

Upcoming webinars are here, including topics such as quantum safe cryptography, analytics for high-volume manufacturing, and mastering EMC simulations for electronic design.

Find Semiconductor Engineering’s latest newsletters here:

Automotive, Security and Pervasive Computing
Systems and Design
Low Power-High Performance
Test, Measurement and Analytics
Manufacturing, Packaging and Materials

The post Chip Industry Week in Review appeared first on Semiconductor Engineering.

Okinawa Institute of Science and Technology proposed a new EUV litho technology using only four reflective mirrors and a new method of illumination optics that it claims will use 1/10 the power and cost half as much as existing EUV technology from ASML.

Applied Materials may not receive expected U.S. funding to build a $4 billion research facility in Sunnyvale, CA, due to internal government disagreements over how to fund chip R&D, according to Bloomberg.

SEMI published a position paper this week cautioning the European Union against imposing additional export controls to allow companies, encouraging them to  be “as free as possible in their investment decisions to avoid losing their agility and relevance across global markets.” SEMI’s recommendations on outbound investments are in response to the European Economic Security Strategy and emphasize the need for a transparent and predictable regulatory framework.

The U.S. may restrict China’s access to HBM chips and the equipment needed to make them, reports Bloomberg. Today those chips are manufactured by two Korean-based companies, Samsung and SK hynix, but U.S.-based Micron expects to begin shipping 12-high stacks of HBM3E in 2025, and is currently working on HBM4.

Synopsys executive chair and founder Dr. Aart de Geus was named the winner of the Semiconductor Industry Association’s Robert N. Noyce Award. De Geus was selected due to his contributions to EDA technology over a career spanning more than four decades.

The top three foundries plan to implement high-NA EUV lithography as early as 2025 for the 18 angstrom generation, but the replacement of single exposure high-NA (0.55) over double patterning with standard EUV (NA = 0.33) depends on whether it provides better results at a reasonable cost per wafer.

Quick links to more news:

Global
In-Depth
Market Reports and Earnings
Education and Training
Security
Product News
Research
Events and Further Reading

Global

Belgium-based Imec released part 2 of its chiplets series, addressing testing strategies and standardization efforts, as well as guidelines and research “towards efficient ESD protection strategies for advanced 3D systems-on-chip.”

Also in Belgium, BelGan, maker of GaN chips, filed for bankruptcy according to the Brussels Times.

TSMC‘s Dresden, Germany, plant will break ground this month.

The UK will dole out more than £100 million (~US $128 million) in funding to develop five new quantum research hubs in Glasgow, Edinburgh, Birmingham, Oxford, and London.

MassPhoton is opening Hong Kong‘s first ultra-high vacuum GaN epitaxial wafer pilot line and will establish a GaN research center.

Infineon completed the sale of its manufacturing sites in the Philippines and South Korea to ASE.

Israel-based RAAAM Memory Technologies received a €5.25 million grant from the European Innovation Council (EIC) to support the development and commercialization of its innovative memory solutions. This funding will enable RAAAM to advance its research in high-performance and energy-efficient memory technologies, accelerating their integration into various applications and markets.

In-Depth

Semiconductor Engineering published its Automotive, Security and Pervasive Computing newsletter this week, featuring these top stories and video:

• Chip Security Now Depends On Widening Supply Chain
• Defining Chip Threat Models To Determining Security Risks
• Post-Quantum Computing Threatens Fundamental Transport Protocols

And:

• Where Power Savings Really Count
• Making Electronics More Efficient (video)

Market Reports and Earnings

The semiconductor equipment industry is on a positive trajectory in 2024, with moderate revenue growth observed in Q2 after a subdued Q1, according to a new report from Yole Group. Wafer Fab Equipment revenue is projected to grow by 1.3% year-on-year, despite a 12% drop in Q1. Test equipment lead times are normalizing, improving order conditions. Key areas driving growth include memory and logic capital expenditures and high-bandwidth memory demand.

Worldwide silicon wafer shipments increased by 7% in Q2 2024, according to SEMI‘s latest report. This growth is attributed to robust demand from multiple semiconductor sectors, driven by advancements in AI, 5G, and automotive technologies.

The RF GaN market is projected to grow to US $2 billion by 2029, a 10% CAGR, according to Yole Group.

Counterpoint released their Q2 smartphone top 10 report.

Renesas completed their acquisition of EDA firm Altium, best known for its EDA platform and freeware CircuitMaker package.

It’s earnings season and here are recently released financials in the chip industry:

AMD  Advantest   Amkor   Ansys  Arteris   Arm   ASE   ASM   ASML
Cadence  IBM   Intel   Lam Research   Lattice   Nordson   NXP   Onsemi 
Qualcomm   Rambus  Samsung    SK Hynix   STMicro   Teradyne    TI  
Tower  TSMC    UMC  Western Digital

Industry stock price impacts are here.

Education and Training

Rochester Institute of Technology is leading a new pilot program to prepare community college students in areas such as cleanroom operations, new materials, simulation, and testing processes, with the intent of eventual transfer into RIT’s microelectronic engineering program.

Purdue University inked a deal with three research institutions — University of Piraeus, Technical University of Crete, and King’s College London —to develop joint research programs for semiconductors, AI and other critical technology fields.

The European Chips Skills Academy formed the Educational Leaders Board to help bridge the talent gap in Europe’s microelectronics sector.  The Board includes representatives from universities, vocational training providers, educators and research institutions who collaborate on strategic initiatives to strengthen university networks and build academic expertise through ECSA training programs.

Security

The Cybersecurity and Infrastructure Security Agency (CISA) is encouraging Apple users to review and apply this week’s recent security updates.

Microsoft Azure experienced a nearly 10 hour DDoS attack this week, leading to global service disruption for many customers.  “While the initial trigger event was a Distributed Denial-of-Service (DDoS) attack, which activated our DDoS protection mechanisms, initial investigations suggest that an error in the implementation of our defenses amplified the impact of the attack rather than mitigating it,” stated Microsoft in a release.

NIST published:

• “Recommendations For Increasing U.S. Participation and Leadership in Standards Development,” a report outlining cybersecurity recommendations and mitigation strategies.
• Final guidance documents and software to help improve the “safety, security and trustworthiness of AI systems.”
• Cloud Computing Forensic Reference Architecture guide.

Delta Air Lines plans to seek damages after losing $500 million in lost revenue due to security company CrowdStrike‘s software update debacle.  And shareholders are also angry.

Recent security research:

• Physically Secure Logic Locking With Nanomagnet Logic (UT Dallas)
• WBP: Training-time Backdoor Attacks through HW-based Weight Bit Poisoning (UCF)
• S-Tune: SOT-MTJ Manufacturing Parameters Tuning for Secure Next Generation of Computing ( U. of Arizona, UCF)
• Diffie Hellman Picture Show: Key Exchange Stories from Commercial VoWiFi Deployments (CISPA, SBA Research, U. of Vienna)

Product News

Lam Research introduced a new version of its cryogenic etch technology designed to enhance the manufacturing of 3D NAND for AI applications. This technology allows for the precise etching of high aspect ratio features, crucial for creating 1,000-layer 3D NAND.

Fig.1: 3D NAND etch. Source: Lam Research

Alphawave Semi launched its Universal Chiplet Interconnect Express Die-toDie IP. The subsystem offers 8 Tbps/mm bandwidth density and supports operation at 24 Gbps for D2D connectivity.

Infineon introduced a new MCU series for industrial and consumer motor controls, as well as power conversion system applications. The company also unveiled its new GoolGaN Drive product family of integrated single switches and half-bridges with integrated drivers.

Rambus released its DDR5 Client Clock Driver for next-gen, high-performance desktops and notebooks. The chips include Gen1 to Gen4 RCDs, power management ICs, Serial Presence Detect Hubs, and temperature sensors for leading-edge servers.

SK hynix introduced its new GDDR7 graphics DRAM. The product has an operating speed of 32Gbps, can process 1.5TB of data per second and has a 50% power efficiency improvement compared to the previous generation.

Intel launched its new Lunar Lake Ultra processors. The long awaited chips will be included in more than 80 laptop designs and has more than 40 NPU tera operations per second as well as over 60 GPU TOPS delivering more than 100 platform TOPS.

Brewer Science achieved recertification as a Certified B Corporation, reaffirming its commitment to sustainable and ethical business practices.

Panasonic adopted Siemens’ Teamcenter X cloud product lifecycle management solution, citing Teamcenter X’s Mendix low-code platform, improved operational efficiency and flexibility for its choice.

Keysight validated its 5G NR FR1 1024-QAM demodulation test cases for the first time. The 5G NR radio access technology supports eMBB and was validated on the 3GPP TS 38.521-4 test specification.

Research

In a 47-page deep-dive report, the Center for Security and Emerging Technology delved into all of the scientific breakthroughs from 1980 to present that brought EUV lithography to commercialization, including lessons learned for the next emerging technologies.

Researchers at the Paul Scherrer Institute developed a high-performance X-ray tomography technique using burst ptychography, achieving a resolution of 4nm. This method allows for non-destructive imaging of integrated circuits, providing detailed views of nanostructures in materials like silicon and metals.

MIT signed a four-year agreement with the Novo Nordisk Foundation Quantum Computing Programme at University of Copenhagen, focused on accelerating quantum computing hardware research.

MIT’s Research Laboratory of Electronics (RLE) developed a mechanically flexible wafer-scale integrated photonics fabrication platform. This enables the creation of flexible photonic circuits that maintain high performance while being bendable and stretchable. It offers significant potential for integrating photonic circuits into various flexible substrate applications in wearable technology, medical devices, and flexible electronics.

The Naval Research Lab identified a new class of semiconductor nanocrystals with bright ground-state excitons, emphasizing an important advancement in optoelectronics.

Researchers from National University of Singapore developed a novel method, known as tension-driven CHARM3D,  to fabricate 3D self-healing circuits, enabling the 3D printing of free-standing metallic structures without the need for support materials and external pressure.

Find more research in our Technical Papers library.

Events and Further Reading

Find upcoming chip industry events here, including:

Upcoming webinars are here, including topics such as quantum safe cryptography, analytics for high-volume manufacturing, and mastering EMC simulations for electronic design.

Find Semiconductor Engineering’s latest newsletters here:

Automotive, Security and Pervasive Computing
Systems and Design
Low Power-High Performance
Test, Measurement and Analytics
Manufacturing, Packaging and Materials

The post Chip Industry Week in Review appeared first on Semiconductor Engineering.

Warpage is becoming a serious concern in advanced packaging, where a heterogeneous mix of materials can cause uneven stress points during assembly and packaging, and under real workloads in the field.

Warpage plays a critical role in determining whether an advanced package can be assembled successfully and meet long-term reliability targets. New advances, such as molding compounds with improved thermal properties, advanced modeling techniques, and creative architectures involving two molding steps are enabling greater control over package warpage, while also providing more flexibility to optimize a robust multi-chiplet system.

Warpage is the inevitable result of the mismatch in coefficients of thermal expansion (CTEs) between the silicon chip, molding compound, copper, polyimide, and other materials. It changes throughout the assembly process, and can cause cracking or delamination failures. The most vulnerable spots include low-k cores, which are subject to cracking and shorts, or non-wet failures in micro-bumps.

“One thing that’s very hot these days is the discussion around warpage and stress of the package,” said Kenneth Larsen, senior director of product management at Synopsys. “This is not only when you’re going through the manufacturing process, where you change temperatures. That can cause warpage. But it’s also when the device you’re building needs to be inserted into a socket. You can have issues around warpage there, as well.”

Even when warpage is effectively addressed during assembly and packaging, a device still may warp under heavy usage in the field. This is particularly true with heterogeneous designs, where chiplets are developed using different materials or processes, and where logic is concentrated in specific areas of an asymmetrical package.

The transition to multi-chiplet packaging is accelerating rapidly due to demands for ever-higher processing speeds and low latency, especially in mobile, automotive and high-performance compute/AI applications. Engineers increasingly are turning to modeling and simulation to understand temperature-dependent warpage, which can vary depending on die thickness, mold-to-silicon ratio, and substrate type. Organic substrates are very attractive because they are inexpensive and can be customized to any size, but they are much more flexible and susceptible to warpage than silicon substrates.

All these considerations point to the need for thermal and structural models of complex heterogeneous assemblies and packages. “Advanced modeling allows companies to simulate the behavior of different materials, thermal dynamics, and mechanical stresses during the assembly process,” said Mike Kelly, vice president of chiplets/FCBGA integration at Amkor. “Through this virtual experimentation, one can predict and mitigate potential challenges, ensuring that the final product meets stringent quality and reliability standards.”

How warpage happens
The assembly process includes multiple heating and cooling steps, which induce a certain amount of deformation between adjacent materials with different thermal and mechanical properties. In advanced packaging, warpage in the 100 micron range is not unheard of.

One of the reasons warpage is such a problem today is the large size of chiplets and the very tight process windows for chiplets, redistribution layers (RDLs), substrates, and bumps of various sizes. The relative expansion and contraction of neighboring materials depends on differences in the material’s CTE, which spells out the increase in size with each degree change of temperature (ppm/°C).

“Chiplets are typically relatively large die,” said Dick Otte, CEO of Promex Industries. “In the iPad, it’s 20 x 30 millimeters, with as many as 10,000 I/Os — usually copper pillar. Just simply taking a single die and putting it down on a substrate can be quite a challenge because the pitches are so small. So what’s critical for these assemblies is controlling warpage and planarity. It needs to stay planar through the whole reflow solder process to bridge that gap between the copper pillar and the contact on the circuit board without warping.”

Warpage can either happen upward, bending at the edges (smiling), or downward (crying), depending on the relative CTEs of the materials in the stack. Silicon, for example, is 2.8; copper is 17; FR4 PCB is 14 to 17 ppm/°C. The worst CTE mismatch is between a silicon interposer and an organic substrate.

It helps to envision stacks in packaging as groups of materials. “You have to look at the CTE of the materials and their reaction at temperatures, so you’ve got relatively low expansion copper on the top and solder at the bottom,” Otte said. “They’re kind of equal with a high expansion dielectric in the middle, so that when you heat this thing up, it kind of expands by the same amount. If you just put all the copper on the top, that thing is going to warp toward the copper side when you heat it up. Copper is 15 ppm per degree C. The organics are more like twice that, at 25 to 30 ppm/°C.

Other key metrics are the modulus, or the elasticity of a material, and the glass transition temperature (Tg), the temperature at which a material begins to flow. These values are related, too. For example, when it comes to the thermal behavior of polymers like epoxy molding compound (EMC), the modulus tends to plummet above its glass transition temperature. That happens because polymer chains tend to slide freely in the liquid state, whereas they are stiffer in a solid form.

In addition to solder reflow, warpage tends to occur at the post-molding curing step. Hung-Chun Yang and colleagues at ASE recently determined that die thickness substantially influences warpage levels measured at multiple steps in an existing process for chip-first fan-out chip on substrate package. [1] They noted that “severe wafer warpage occurred after curing, resulting in misalignment and difficulty in handling in the subsequent process.” To reduce package warpage, the team replaced a metal carrier/thin film approach with a glass carrier. The team also determined that a 3D finite element method (FEM) captures the warpage behavior and agreed well with actual test vehicle data.

Fig. 1: The glass carrier in the improved flow (right) induced less warpage than the original flow. Increasing the die thickness also dramatically reduced warpage. Source: ASE

The chip-first process begins with probing the fabricated wafers, thinning and then electroplating copper studs prior to sawing and placement of known good die in two schemes. The initial process used a metal carrier that is removed after molding and replaced with a thin film. The improved process uses a glass carrier that remained through molding, curing, mold grinding, RDL, and copper pillar processes, and then wass de-bonded.

Warpage reaches its maximum level during post-mold curing, and it changes most dramatically at the curing step and after glass carrier debonding. The glass carrier flow reduces warpage overall. In addition, the ASE engineers determined they can reduce warpage an additional 35% by increasing the wafer thickness from 0.54mm to 0.7mm.

A second strategy for reducing warpage involves using EMCs with different thermal properties, especially when the process calls for two molding steps. Amkor engineers recently evaluated the reliability performance of two high-performance multi-chiplet packages by modeling and fabricating two high-performance test vehicles. One used a module approximately the size of one reticle, containing 1 ASIC, 2 HBMs and 2 bridge die (33 x 26mm). The second module was 3 reticles in size, with 2 ASICs, 8 HBMs and 10 bridge dies (54 x 46mm). [2] Heejun Jang and colleagues at Amkor Technology Korea carried out modeling and simulation using the Ansys Parametric Design Language (APDL) version 16.1 simulator and compared results with test vehicles containing dummy dies.

Amkor’s die-last S-Connect process starts with a carrier wafer, on which copper studs for the bridge die and copper pillars are fabricated (see figure 2). The integrated passives and bridge die are embedded in the first mold, which is cured and then ground back. RDL is deposited on the mold and solder capture pads and dies attached to the pads using micro-bumps. Then, the solder is reflowed and underfilled. The second mold around the face-up die is cured and ground back, followed by C4 bumping on the bottom for flip-chip connect to the substrate. The simulation analyzes warpage with 9 combinations of 3 different EMCs with high, medium, and low CTEs (7 to 12 ppm below Tg, 22 to 46 ppm above Tg) and high-to-low glass transition temperatures (145°C to 175°C). [2]

Fig. 2: Process flow for S-Connect Package. Source: Amkor

Warpage as a function of EMC choice showed all materials followed the same smile pattern at room temperature, and cry pattern at high temperature (250°C). The EMCs with the lower CTEs caused less warpage. And in cases where the mold occupies more area relative to chip area, the warpage level is more pronounced. More importantly, the warpage levels were roughly 50% higher for 450µm die relative to 650µm-thick die. Interestingly, the thicker silicon die was 3X more effective in controlling warpage relative to EMC material selection on overall module warpage, so die thickness is the biggest lever in reducing warpage in cases where it can be increased.

Reliability testing is paramount once the package configuration is chosen. Amkor ran its advanced packaging test vehicles through moisture resistance testing, highly accelerated stress testing, thermal cycling condition B, and high temperature storage tests. These are needed to root out infant mortality issues, and cross-sectional analysis can reveal any cracks or latent defects that could precipitate into failures in field use.

While the above example may constitute a large multi-chiplet package today, package sizes are growing larger still, which means even more attention to warpage will be needed. More and more this will drive assembly lines toward digital twin or virtual representations to enable process and package optimization.

“By creating virtual representations of the semiconductor assembly line, one can identify potential areas of concern and optimize control strategies,” said Amkor’s Kelly. “Virtual fabrication in package assembly enables companies to assess the impact of design changes on manufacturing processes before physical prototypes are even created. This not only accelerates the product development cycle, but also minimizes the risk of costly errors.”

The early identification of potential bottlenecks further shortens cycle times, and enhances overall efficiency.

Conclusion
Going forward, even greater attention to mechanical and thermal properties will be required by teams comprised of designers and packaging engineers. “Tight tolerances in new packaging design require an accurate analysis of mechanical and electrical tolerances during stack up,” said Curtis Zwenger, vice president of engineering and technical marketing at Amkor. “Increasingly higher levels of process capability are required, with common metrics like CpK. Identification of these critical interactions in the design can be accomplished early in process development with this type of modeling. In turn, these analyses guide the investment of advanced process control to ensure process capability is maintained.”

References

1. C. Yang, et al, “Investigation of Wafer Warpage Evolution Based on Fan-out Chip-first Process,” 2024 International Conference on Electronics Packaging (ICEP), Toyama, Japan, 2024, pp. 151-152, doi: 10.23919/ICEP61562.2024.10535572.
2. H. Jang et al., “Reliability Performance of S-Connect Module (Bridge Technology) for Heterogeneous Integration Packaging,” 2023 IEEE 73rd Electronic Components and Technology Conference (ECTC), Orlando, FL, USA, 2023, pp. 1027-1031, doi: 10.1109/ECTC51909.2023.00175.

Related Reading
What Works Best For Chiplets
Not all chiplets are interchangeable, and options will be limited.

The post Controlling Warpage In Advanced Packages appeared first on Semiconductor Engineering.

SK hynix and TSMC plan to collaborate on HBM4 development and next-generation packaging technology, with plans to mass produce HBM4 chips in 2026. The agreement is an early indicator for just how competitive, and potentially lucrative, the HBM market is becoming. SK hynix said the collaboration will enable breakthroughs in memory performance with increased density of the memory controller at the base of the HBM stack.

Intel assembled the industry’s first high-NA EUV lithography system. “Compared to 0.33NA EUV, high-NA EUV (or 0.55NA EUV) can deliver higher imaging contrast for similar features, which enables less light per exposure, thereby reducing the time required to print each layer and increasing wafer output,” Intel said.

Fig. 1: Bigger iron — Intel’s brand new high-NA EUV machinery. Source: Intel

Samsung is slated to receive $6.4 billion in CHIPS ACT funding from the U.S. Department of Commerce (DoC) as part of a $40 billion expansion of its Austin, Texas, manufacturing facility, along with an R&D fab, a pair of leading-edge logic fabs, and an advanced packaging plant in nearby Taylor, Texas.

Micron and the U.S. government next week will announce $6.1 billion in CHIPS Act funding for the development of advanced memory chips in New York and Idaho, according to AP News.

Cadence unveiled its Palladium Z3 Emulation and Protium X3 FPGA Prototyping systems, targeted at multi-billion-gate designs with 2X increase in capacity and a 1.5X performance increase compared to previous-generation systems. Cadence also teamed up with MemVerge to enable seamless support for AWS Spot instances for long-running high-memory EDA jobs, and extended its hybrid cloud environment solutions through a collaboration with NetApp.

Fig. 2: At CadenceLive Silicon Valley, NVIDIA CEO Jensen Huang (r.) discussed accelerated computing and generative AI with Cadence CEO Anirudh Devgan. Source: Semiconductor Engineering

Quick links to more news:

Global
Markets and Money
In-Depth
Security
Education and Workforce
Product and Standards
Research
Quantum
Events
Further Reading

Global

After Taiwan’s recent 7.2 magnitude earthquake, TSMC reached more the 70% tool recovery in its fabs within the first 10 hours and full recovery by the end of the third day, according to this week’s earnings call. Some wafers in process were scrapped but the company expects the lost production to be recovered in the second quarter.  Also in the call, TSMC said they expect their “customers to share some of the higher cost” of the overseas fabs and higher electricity costs.

Advantest‘s regional headquarters in Taiwan donated $2.2 million New Taiwan dollars ($680,000 US) for aid to victims and reconstruction efforts related to the Taiwan earthquake that struck on April 3.

Japan’s exports grew by more than 7% YoY in March, driven by an 11.3% increase in shipments of electronics and semiconductor manufacturing equipment, much of it to China, according to NikkeiAsia.

China‘s IC output grew 40% in the first quarter, primarily driven by EVs and smartphones, according to the South China Morning Post.

In the U.S., the Biden Administration released a notice of funding opportunity of $50 million targeted at small businesses pursuing advances in metrology research and technology. Also, the U.S. Department of Energy announced a $33 million funding opportunity for smart manufacturing technologies.

Germany‘s Fraunhofer IIS launched its On-Board Processor (FOBP) for the German Space Agency’s Heinrich Hertz communication satellite. FOBP can be controlled and reprogrammed from Earth and will be used to investigate creation of hybrid communication networks.

Markets and Money

RISC-V startup Rivos raised more than $250 million in capital investments to tape out its first power-optimized chips for data analytics and generative AI applications.

Silvaco filed to go public on Nasdaq. The company also received a $5 million convertible note investment from Microchip.

Microchip acquired Neuronix AI Labs to provide AI-enabled FPGA solutions for large-scale, high-performance edge applications.

The advanced packaging market saw a modest 4% increase in revenues in Q4 2023 versus the previous quarter, with a projected decline of 13% QoQ in the first quarter of 2024, reports Yole. Overall, the market is expected to increase from $38 billion in 2023 to $69.5 billion in 2029 with a CAGR of 10.7%.

TSMC’s CoWoS total capacity will increase by 150% in 2024 due to demand for NVIDIA’s Blackwell Platform, reports TrendForce.

ASML saw a nearly 40% drop in new litho equipment sales QoQ in Q1 2024 and a 61% drop in net bookings as manufacturers reduced investments in new capital equipment during the recent semiconductor market slump.

Global PC shipments rose about 3% YoY in Q1 2024, and that same growth is expected for full year 2024, reports Counterpoint. Manufacturers are predicted to promote AI PCs as semiconductor companies prepare to launch SoCs featuring higher TOPS.

The GenAI smartphone market share is predicted to reach 11% by 2024 and 43% by 2027, reports Counterpoint. Samsung likely will lead in 2024, but Apple may overtake it in 2025.

The RF GaN market is expected to exceed $2 billion by 2029, fueled by the defense and telecom infrastructure sectors, reports Yole.

In-Depth

Semiconductor Engineering published its Manufacturing, Packaging & Materials newsletter this week. Top articles include:

• Electromigration Concerns Grow In Advanced Packages
• What Works Best For Chiplets
• Enabling Advanced Devices With Atomic Layer Processes

Plus, check out these new stories and tech talks:

• Architecting Chips For High-Performance Computing
• Future-Proofing Automotive V2X
• Secure Movement Of Data In Test
• Challenges With Chiplets and Power Delivery

Security

In security research:

• Seoul National University, Sandia National Laboratories, Texas A&M University, and Applied Materials demonstrated a memristor crossbar architecture for encryption and decryption.
• Robert Bosch, Forschungszentrum Julich, and Newcastle University investigated techniques for error detection and correction in in-memory computing.
• The University of Florida introduced an automated framework that can help identify security assets for a design at the register-transfer level (RTL).

DARPA conducted successful in-air tests of AI flying an F-16 autonomously versus a human-piloted F-16 in visual-range combat scenarios.

The National Security Agency’s Artificial Intelligence Security Center (NSA AISC) published joint guidance on deploying AI systems securely with the Cybersecurity and Infrastructure Security Agency (CISA), the Federal Bureau of Investigation (FBI), and international partners. CISA also issued other alerts.

Products and Standards

Samsung uncorked LPDDR5X DRAM built on a 12nm process that supports up to 10.7 Gbps and expands the single package capacity of mobile DRAM up to 32 GB.

Keysight revealed its next-generation RF circuit simulation tool that supports multi-physics co-design of circuit, electromagnetic, and electrothermal simulations across Cadence, Synopsys, and Keysight platforms.

Renesas released its FemtoClock family of ultra-low jitter clock generators and jitter attenuators with 8 and 12 outputs, enabling clock tree designs for high-speed interconnect systems in telecom and data center switches, routers, medical imaging, and more.

Movellus expanded its droop response solutions with Aeonic Generate AWM3, which responds to voltage droops within 1 to 2 clock cycles while providing enhanced observability for droop profiling and enabling fine-grained dynamic frequency scaling.

Efabless announced the second version of its Python-based open-source EDA software for construction of customizable flows using proprietary or open-source tools.

Faraday Technology licensed Arm’s Cortex-A720AE IP to use in the development of AI-enabled vehicle ASICs. Also, Untether AI teamed up with Arm to enable its inference acceleration technology to be implemented alongside the latest-generation Automotive Enhanced technology from Arm for ADAS and autonomous vehicle applications.

FOXESS used Infineon’s 1,200V CoolSiC MOSFETs and EiceDRIVER gate drivers for industrial energy storage applications, aiming to promote green energy.

Emotors adopted Siemens’ Simcenter solutions for NVH testing of next-gen automotive e-drives.

SiTime debuted a family of clock generators for AI datacenter applications with clock, oscillator, and resonator in an integrated chip.

JEDEC published the JESD79-5C DDR5 SDRAM standard, which includes a DRAM data integrity improvement called Per-Row Activation Counting (PRAC) that precisely counts DRAM activations on a wordline granularity and alerts the system to pause traffic and designate time for mitigation measures when an excessive number of activations are detected.

The LoRa Alliance launched its roadmap for the development of the LoRaWAN open standard for IoT communications, referring to long-range radio (LoRa) low-power wide-area networks (LPWANs).

Education and Workforce

Texas A&M introduced a new Master of Science program for microelectronics and semiconductors, which will begin in fall 2025.

The Cornell NanoScale Science and Technology Facility (CNF) is partnering with Tompkins Cortland Community College and Penn State to offer a free Microelectronics and Nanomanufacturing Certificate Program to veterans and their dependents.

Eindhoven University of Technology (TU/e) has more than 700 researchers and 25 research group focused on the chip industry, but the number is projected to grow significantly due to the Dutch government’s recent investment.

Research

Intel announced a large-scale neuromorphic system based on its Loihi 2 processor. Initially deployed at Sandia National Laboratories, it aims to support research for future brain-inspired AI. Intel is also collaborating with Seekr on next-gen LLM and foundation models.

Los Alamos National Lab, HPE, and NVIDIA collaborated on the design and installation of Venado, the Lab’s new supercomputer. “Venado adds to our cutting-edge supercomputing that advances national security and basic research, and it will accelerate how we integrate artificial intelligence into meeting those challenges,” said Thom Mason, director of Los Alamos National Laboratory in a release.

Penn State is partnering with Morgan Advanced Materials on a five-year, multi-million-dollar research project to advance silicon carbide (SiC) technology. Morgan will become a founding member of the Penn State Silicon Carbide Innovation Alliance. Also, Coherent secured CHIPS Act funding of $15 million for research into high-voltage, high-power silicon carbide and single-crystal diamond semiconductors.

Oak Ridge National Laboratory (ORNL) researchers found a more efficient way to extract lithium from waste liquids leached from mining sites, oil fields, and used batteries.

Quantum

Quantinuum said it reached an inherent 99.9% 2-qubit gate fidelity in its commercial quantum computer, a point at which quantum error correction protocols can be used to greatly reduce error rates.

D-Wave Quantum uncorked a fast-anneal feature to speed up computations on its quantum processing units, which reduces the impact of external disturbances.

MIT researchers outlined a new conceptual model for a quantum computer that aims to make writing code for them easier.

SLAC National Accelerator Laboratory, Stanford University, Max Planck Institute of Quantum Optics, Ludwig-Maximilians-Universitat Munich, and Instituto de Ciencia de Materiales de Madrid researchers proposed a method that harnesses the structure of light to tweak the properties of quantum materials.

Events

Find upcoming chip industry events here, including:

Upcoming webinars are here.

Further Reading

Read the latest special reports and top stories, or check out the latest newsletters:

Systems and Design
Low Power-High Performance
Test, Measurement and Analytics
Manufacturing, Packaging and Materials
Automotive, Security and Pervasive Computing

The post Chip Industry Week In Review appeared first on Semiconductor Engineering.

The semiconductor industry is preparing for the migration from proprietary chiplet-based systems to a more open chiplet ecosystem, in which chiplets fabricated by different companies of various technologies and device nodes can be integrated in a single package with acceptable yield.

To make this work as expected, the chip industry will have to solve a variety of well-documented technical and business issues, and it will have to rein in some of the grander visions of what’s possible — at least initially. The basic challenge is aligning domain-specific performance demands of end systems, which contain a growing number of chiplets, with the assembly and packaging capabilities and methodologies of IDMs, foundries, and OSATs. This includes the creation of assembly development kits (ADKs) that are roughly the equivalent of process development kits (PDKs), which today are codified with manufacturing specifications.

A PDK provides the appropriate level of detail needed to develop planar chips, marrying design tools with fab processes to achieve a predictable outcome. But making this work for an ADK with heterogeneous chiplets is many times more complex. Design and assembly teams need to manage thermal, mechanical, and electrical co-dependencies that cause electrical and mechanical stress, resulting in warpage, reduced yield, and reliability issues under real-world workloads. Layered on top of this the business and legal issues related to packaging of different devices from different manufacturers.

“Chiplets are a growing trend, especially in the HPC and networking segments, with potential to scale to other applications,” said Gabriela Pereira, technology and market analyst for semiconductor packaging at Yole Intelligence. “The industry has understood that high-end advanced packaging technologies are needed to connect them — but that’s much more complex than it seems. Connecting chiplets requires the design of high-bandwidth interconnections at the package level, which can take different forms — e.g., 2D, 2.5D or 3D — while ensuring that the thermal and power requirements are fulfilled.”

Commercial chiplet-based devices generally are domain-specific, and sometimes developed for a specific workload. So despite a big industry push to create a LEGO-like mix-and-match ecosystem for chiplets — which today includes multiple IP and EDA vendors, foundries, memory suppliers, OSATs, substrate suppliers, etc. — making this work as planned will require time and a massive amount of work.

Fig. 1: System assembly requires tighter coupling between chipmakers and OSATs. Source: ASE

In creating heterogeneous integrated designs, it’s essential to have much tighter collaboration between foundries, IDMs, OSATs, and PCB manufacturers. And because each chiplet-based system will be customized, the number of assembly processes will grow substantially. For example, one OSAT noted that among its ~5,000 customers, there are ~1,000 different assembly processes.

That diversity in products and processes makes it difficult to achieve predictable results by choosing chiplets from a large menu of options.

“We’ve already encountered a lot of limitations including not only the silicon, but also integration and the ecosystem,” said Lihong Cao, senior director at ASE Group, at MEPTEC’s Road to Chiplets forum. She stressed that customers continue to push for a low-cost chiplet assembly process, which is creating constructive tension between developing a sophisticated assembly process and the economic realities of different industry sectors. Computing devices for automotive have a higher cost sensitivity than for data centers, for example, but their chips operate in a harsher environment over a longer lifetime.

What’s needed is a defined set of assembly process recipes — basically, a highly limited menu of choices — that are specific to the end application (HPC, automotive, RF telecommunications) in order to lower the cost of chiplet-based systems. OSATs and foundries already are moving in that direction for high-performance computing. For example, at its 2024 Direct Connect event, Intel shared its six different package processes for chiplets. TSMC and Samsung also offer defined sets of chiplet processes. But the success of these assembly processes requires engineering teams to co-optimize the flows, processes, and materials to best match the system requirements.

Fig. 2: Integrated platform development requires tightly coupled architectural analysis that co-optimizes the system design to architecture to assembly process and packaging material selections. Source: Applied Materials

“Previously, when we designed a system we only had to be worried about the system requirements. Once we start segregating into dies and reassembling them, we have to start looking at other things. We have to worry about putting them together while considering signal integrity between dies, reliability, thermals, etc.,” said Itai Leshniak, director of AI systems solutions at Applied Materials, at the MEPTEC forum. “If we take the case of AI-based computer vision, we can break it down layer by layer — on the hardware side, determining which computer vision processors, sensors, filters are needed to break it down into the architecture at layer. Then we begin to go through how to package all these chiplets, and then which materials to use and how to take advantage of those materials.”

Materials and assembly processes
Conceptually, design engineers will use chiplets to design a system. However, the co-design and integration is far more complicated than assembling a set of LEGO blocks, because the chiplets, interposers, and package substrates come from different design houses and manufacturing facilities. The advanced packaging technologies used to connect chiplets vary with an alphabet soup of names — FOWLP, FOPLP, CoWoS, etc., each of which poses additional design and material choices along with certain process limitations.

Fig. 3: There are a multitude of choices in multi-die packaging from the high-level layout to substrates, materials, bonding methods, and cooling materials. Source: Synopsys

Currently engineering teams determine the tradeoffs among the different packaging options to select materials, derive a process recipe, and determine design rules.

Materials are a good starting point. “Materials are very important because they enable new products and packaging technologies,” Tanja Braun, deputy group manager at the Fraunhofer Institute for Reliability and Microintegration IZM. “As you move into more advanced packaging, process is getting much more complex because you are putting more things together. In the end, it’s a combination of equipment, materials, and process development.”

There are three thermal parameters that are critical in package assembly processes — coefficients of thermal expansion (CTE), glass transition temperature (T_g), and thermal conductivity. These factors affect how a material behaves in manufacturing to packaging processes, as well as how it behaves in the field.

“Challenges for our materials include temperature limitations of different die,” said Rama Puligadda, CTO at Brewer Science. “We have to ensure that the temperatures used for bonding materials don’t exceed the thermal limitations of any of the chips that are being integrated into the package. Additionally, there may be some subsequent processes like redistribution layer (RDL) formation or molding. Our materials have to survive those processes. They have to survive the chemicals they come in contact with throughout the packaging process scheme. Mechanical stresses in the package add additional challenges for bonding materials.”

Within a stack of chiplets-on-substrate with an optional interposer, their material attributes affect the thermal-mechanical stresses between neighboring materials, as well. This directly impacts interconnect dimensional control over a large area substrate area.

“If you go work the numbers, you will find that the level of tolerance and control required is frightening,” said Dick Otte, CEO of Promex Industries. “You’re talking about controlling dimensions equivalent to the width of a grass blade over the length of a football field, so that’s roughly 1 in 100,000.”

The goal is uniform heating of the structure in reflow in order to attain the best process results and to avoid cracking. “When you’re taking it through a 250 degrees centigrade temperature change, then you need to heat up slowly so that the top doesn’t get hot before the bottom does,” said Otte.

Multi-physics to comprehend co-optimization
Multi-physics modeling has become the go-to method for co-optimizing packaging design and assembly process development. That affects both permanent and temporary materials, as well the placement of processors, memories, and other components.

“You always looking to what the customer needs electrically, because that’s going to help define the material set. The material set is broadly applicable to a bunch of speed ranges. As long as you don’t step outside of those electrical specifications, theoretically you should be okay,” said Mike Kelly, vice president of advanced package and technology integration at Amkor Technology.

To save many iterations of empirically based development, engineers can use physics-based simulations to understand the impact of a material set’s properties impact on the assembly process, power/thermals, and mechanical vibrations.

Consider that HPC chiplet products can consume ~1,000 watts at peak performance so the power and thermal interactions need to be fully understood.

“We’ve struggled, as everybody has, with this blizzard of complexity in the different techniques. Not only do they vary across different vendors, but they’re also varying over time,” said Marc Swinnen, director of product marketing at Ansys. “Our approach has been to identify the essentials that need to be worked on. We work jointly with customers to develop a simulation flow that actually achieves what is needed now.”

Materials are just one piece of the puzzle. “Then there’s the assembly stresses that need to be modeled to know whether you can correctly assemble this device. The third one is mechanical vibration,” Swinnen said. “Can your device withstand those regular vibrations? Modeling these attributes ties directly into our mechanical analysis tools — acoustic, thermal, vibration, etc. In the end, you’re going to have to do physics simulation. We’re trying to make it accessible to people in many different forms. But the bedrock of our tool offerings is that we have the meshing simulation and analysis. It’s a question of getting the data in the right format in a way that’s practical and usable.”

Evolving assembly design kits
For conventional packages, OSATs provide design rules for each packaging technology. These need to consider electrical, mechanical and thermal design requirements and manufacturing process limitations. In effect this is a multi-dimensional bounding box. Suppliers perform iterations with the customer to create a product specific process recipe.

Rules cover the macro-level attributes. “At a minimum, what you see from design rules is maximum package size, maximum silicon size, and whether silicon can be [mounted] on both sides of the substrate, such that when you follow these constructions the final product will have a lifetime of 1,000 thermal cycles, for example,” said Fraunhofer’s Braun.

In addition, design rules need to describe routing constraints for the interposer and/or redistribution layer, such as RDL line widths and spaces, ball-grid/pillar/pad size and pitches, and the maximum number of interconnections.

Breaking up a monolithic HPC device into multiple dies shifts some of the semiconductor design/process complexity into the packaging space. That makes things much more complicated. Consider that to connect 10 dies requires on order of 100,000 traces within the interposer’s or substrate’s redistribution layer.

To cope with the complexity at the chip level, the IC industry has long relied upon process design kits (PDKs) to capture design rules in an electronic file that can be imported into EDA tools. Their counterparts, assembly design kits (ADKs), are relatively immature.

“We call it Smart Package,” said Amkor’s Kelly. “It’s an ADK that we give to every customer who’s doing their own design. It is a set of macros, and a customization of a database tailored to a customer’s particular design. For chiplets, it is a high-density fan-out package technology. And it’s cognizant of the limitations for metal density and metal spacing, etc. This makes it easier for us to do design rule checks (DRCs).”

But right now, with the level of customization still required, how an ADK is derived and what it entails is in flux. Partnerships between EDA tool vendors, OSATs, and semiconductor device providers are required.

“We come from the IC world where everything is very rigid,” said Kenneth Larsen, director of 3D-IC product management in Synopsys‘ EDA Group. “On the OSAT side, and maybe this is because it’s so custom, design rules seem like a data sheet. Then you build and optimize the products over time or in collaboration with the OSAT. It’s not an electronic exchange. In the IC world, this would be totally unheard of. While it is possible to tweak a few things, you have a qualification process. And it seems like that’s not there yet for packaging.”

Materials and associated assembly recipes ultimately drive what’s possible for a chiplet-substrate stack in terms of pillar pitch, RDL line widths and spaces, bonding processes, and chiplet placement tolerances. But within a handful of ADKs, there are many possible interactions to consider.

The current focus is on co-optimizing the system design with the chiplet assembly process, leading to an assembly process development flow (see figure 4). This flow considers the needs of customization of an assembly process, and it creates the necessary design rules to be used by package designers.

Fig. 4: Chip-package hybrid flow. Source: ASE

“First you need to define your structure using chiplets. Are you using substrate RDL, 2.5D RDL, or a bridge? After that you need to consider your structure’s materials. What kind of material do you choose to fulfill your electrical performance and the mechanical stress requirements,” said Cao. “After that, you do pre-analysis to ensure all the structures and materials you use are workable in terms of electrical, warpage and mechanical stress.”

The design planning flow also includes the evaluation of die-to-die interconnects through the documents for co-design sign-off.

Conclusion
Before chiplet-based designs can be enabled outside the IDM model, the industry needs to complete the ecosystem that bridges the manufacturing and design complexity. This is because the need to co-optimize the system architecture based on materials, process, and integration capabilities is essential. While this would be easier with a set of well-defined products for the chiplet ecosystem to drive forward on, that has not happened yet.

Engineering teams across the design and manufacturing stack will need to collaborate to choose the appropriate materials, architectures, processes, etc., to develop a final chiplet-based product that is designable. As ASE group’s Cao noted, “An integrated design and manufacturing ecosystem is important. It is very critical to have collaboration among IDM, vendors, materials suppliers. Everyone needs to work together to really enable integration for the real applications.”

Related stories
Fan-Out Packaging Gets Competitive
Manufacturability reaches sufficient level to compete with flip-chip BGA and 2.5D.

Inside Panel-Level Fan-Out Technology
Fraunhofer’s panel experts dig into why this approach is needed and where the challenges are to making it work.

Next Steps For Panel-Level Packaging
Where it’s working, and what challenges remain for even broader adoption.

Mini-Consortia Forming Around Chiplets
Commercial chiplet marketplaces are still on the distant horizon, but companies are getting an early start with more limited partnerships.

What Can Go Wrong In Heterogeneous Integration
Workflows and tools are disconnected, mechanical stress is ill-defined, and complete co-planarity is nearly impossible. But there are solutions on the horizon.

Mechanical Challenges Rise With Heterogeneous Integration
But gaps in tools make it difficult to address warpage, structural issues, and new materials in multi-die/multi-chiplet designs.

Chiplets: 2023 (EBook)
What chiplets are, what they are being used for today, and what they will be used for in the future.

The post What Works Best For Chiplets appeared first on Semiconductor Engineering.

Automotive processors are rapidly adopting advanced process nodes. NXP announced the development of 5 nm automotive processors in 2020 [1], Mobileye announced EyeQ Ultra using 5 nm technology during CES 2022 [2], and TSMC announced its “Auto Early” 3 nm processes in 2023 [3]. In the past, the automotive industry was slow to adopt the latest semiconductor technologies due to reliability concerns and lack of a compelling need. Not anymore.

The use of advanced processes necessitates the use of advanced packaging as seen in high performance computing (HPC) and mobile applications because [4][5]:

1. While transistor density has skyrocketed, I/O density has not increased proportionally and is holding back chip size reductions.
2. Processors have heterogeneous, specialized blocks to support today’s workloads.
3. Maximum chip sizes are limited by the slowdown of transistor scaling, photo reticle limits and lower yields.
4. Cost per transistor improvements have slowed down with advanced nodes.
5. Off-package dynamic random-access memory (DRAM) throttles memory bandwidth.

These have been drivers for the use of advanced packages like fan-out in mobile and 2.5D/3D in HPC. In addition, these drivers are slowly but surely showing up in automotive compute units in a variety of automotive architectures as well (see figure 1).

Fig. 1: Vehicle E/E architectures. (Image courtesy of Amkor Technology)

Vehicle electrical/electronic (E/E) architectures have evolved from 100+ distributed electronic control units (ECUs) to 10+ domain control units (DCUs) [6]. The most recent architecture introduces zonal or zone ECUs that are clustered in physical locations in cars and connect to powerful central computing units for processing. These newer architectures improve scalability, cost, and reliability of software-defined vehicles (SDVs) [7]. The processors in each of these architectures are more complex than those in the previous generation.

Multiple cameras, radar, lidar and ultrasonic sensors and more feed data into the compute units. Processing and inferencing this data require specialized functional blocks on the processor. For example, the Tesla Full Self-Driving (FSD) HW 3.0 system on chip (SoC) has central processing units (CPUs), graphic processing units (GPUs), neural network processing units, Low-Power Double Data Rate 4 (LPDDR4) controllers and other functional blocks – all integrated on a single piece of silicon [8]. Similarly, Mobileye EyeQ6 has functional blocks of CPU clusters, accelerator clusters, GPUs and an LPDDR5 interface [9]. As more functional blocks are introduced, the chip size and complexity will continue to increase. Instead of a single, monolithic silicon chip, a chiplet approach with separate functional blocks allows intellectual property (IP) reuse along with optimal process nodes for each functional block [10]. Additionally, large, monolithic pieces of silicon built on advanced processes tend to have yield challenges, which can also be overcome using chiplets.

Current advanced driver-assistance systems (ADAS) applications require a DRAM bandwidth of less than 60GB/s, which can be supported with standard double data rate (DDR) and LPDDR solutions. However, ADAS Level 4 and Level 5 will need up to 1024 GB/s memory bandwidth, which will require the use of solutions such as Graphic DDR (GDDR) or High Bandwidth Memory (HBM) [11][12].

Fig. 2: Automotive compute package roadmap. (Image courtesy of Amkor Technology)

Automotive processors have been using Flip Chip BGA (FCBGA) packages since 2010. FCBGA has become the mainstay of several automotive SoCs, such as EyeQ from Mobileye, Tesla FSD and NVIDIA Drive. Consumer applications of FCBGA packaging started around 1995 [13], so it took more than 15 years for this package to be adopted by the automotive industry. Computing units in the form of multichip modules (MCMs) or System-in-Package (SiP) have also been in automotive use since the early 2010s for infotainment processors. The use of MCMs is likely to increase in automotive compute to enable components like the SoC, DRAM and power management integrated circuit (PMIC) to communicate with each other without sending signals off-package.

As cars move to a central computing architecture, the SoCs will become more complex and run into size and cost challenges. Splitting these SoCs into chiplets becomes a logical solution and packaging these chiplets using fan-out or 2.5D packages becomes necessary. Just as FCBGA and MCMs transitioned into automotive from non-automotive applications, so will fan-out and 2.5D packaging for automotive compute processors (see figure 2). The automotive industry is cautious but the abovementioned architecture changes are pushing faster adoption of advanced packages. Materials, processes, and factory controls are key considerations for successful qualification of these packages in automotive compute applications.

In summary, the automotive industry is adopting advanced semiconductor technologies, such as 5 nm and 3 nm processes, which require the use of advanced packaging due to limitations in I/O density, chip size reductions, and memory bandwidth. Processors in the latest vehicle E/E architectures are more complex and require specialized functional blocks to process data from multiple sensors. As cars move to the central computing architecture, the SoCs will become more complex and run into size and cost challenges. Splitting these SoCs into chiplets becomes a logical solution and packaging these chiplets using fan-out or 2.5D technology becomes necessary.

Sources

1. NXP. “NXP Selects TSMC 5nm Process for Next-Generation High-Performance Automotive Platform.” NXP, https://www.nxp.com/company/about-nxp/nxp-selects-tsmc-5nm-process-for-next-generation-high-performance-automotive-platform:NW-TSMC-5NM-HIGH-PERFORMANCE.
2. Mobileye. “Mobileye at CES 2022.” Mobileye, https://www.mobileye.com/news/mobileye-ces-2022-tech-news/.
3. Business Wire. “TSMC Showcases New Technology Developments at 2023 Technology Symposium.” Business Wire, https://www.businesswire.com/news/home/20230426005359/en/TSMC-Showcases-New-Technology-Developments-at-2023-Technology-Symposium.
4. Swaminathan, Raja. “Advanced Packaging: Enabling Moore’s Law’s Next Frontier Through Heterogeneous Integration.” HotChips33, https://hc33.hotchips.org/assets/program/tutorials/2021%20Hot%20Chips%20AMD%20Advanced%20Packaging%20Swaminathan%20Final%20%2020210820.pdf
5. SemiAnalysis. “Advanced Packaging Part 1” SemiAnalysis, https://www.semianalysis.com/p/advanced-packaging-part-1-pad-limited?utm_source=%2Fsearch%2Fadvanced%2520packaging&utm_medium=reader2.
6. McKinsey & Company. “Getting Ready for Next-Generation EE Architecture with Zonal Compute.” McKinsey & Company, https://www.mckinsey.com/industries/semiconductors/our-insights/getting-ready-for-next-generation-ee-architecture-with-zonal-compute.
7. NXP. “How Zonal E/E Architectures with Ethernet are Enabling Software-Defined Vehicles.” NXP, https://www.nxp.com/company/blog/how-zonal-e-e-architectures-with-ethernet-are-enabling-software-defined-vehicles:BL-HOW-ZONAL-EE-ARCHITECTURES.
8. WikiChip. “Tesla (Car Company)/FSD Chip.” WikiChip, https://en.wikichip.org/wiki/tesla_(car_company)/fsd_chip.
9. Mobileye. “EyeQ Chip.” Mobileye, https://www.mobileye.com/technology/eyeq-chip/.
10. Ziadeh, Bassam. “Driving Adoption of Advanced IC Packaging in Automotive Applications.” Presentation at IMAPS DPC, March 2023. General Motors, Fountain Hills AZ, March 16, 2023.
11. K Matthias Jung and Norbert Wehn. “Driving Against the Memory Wall: The Role of Memory for Autonomous Driving.” Fraunhofer IESE, Kaiserslautern, Germany, and Microelectronic Systems Design Research Group, University of Kaiserslautern, Kaiserslautern, Germany. Kluedo, https://kluedo.ub.rptu.de/frontdoor/deliver/index/docId/5286/file/_memory.pdf.
12. Micron. “Cinco de Play: Memory – Is That Critical to Autonomous Driving?” Micron, https://www.micron.com/about/blog/2017/october/cinco-play-memory-is-that-critical-to-autonomous-driving.
13. McKinsey & Company. “Advanced Chip Packaging: How Manufacturers Can Play to Win.” McKinsey & Company, https://www.mckinsey.com/industries/semiconductors/our-insights/advanced-chip-packaging-how-manufacturers-can-play-to-win.

The post Powering The Automotive Revolution: Advanced Packaging For Next-Generation Vehicle Computing appeared first on Semiconductor Engineering.

SK hynix and TSMC plan to collaborate on HBM4 development and next-generation packaging technology, with plans to mass produce HBM4 chips in 2026. The agreement is an early indicator for just how competitive, and potentially lucrative, the HBM market is becoming. SK hynix said the collaboration will enable breakthroughs in memory performance with increased density of the memory controller at the base of the HBM stack.

Intel assembled the industry’s first high-NA EUV lithography system. “Compared to 0.33NA EUV, high-NA EUV (or 0.55NA EUV) can deliver higher imaging contrast for similar features, which enables less light per exposure, thereby reducing the time required to print each layer and increasing wafer output,” Intel said.

Fig. 1: Bigger iron — Intel’s brand new high-NA EUV machinery. Source: Intel

Samsung is slated to receive $6.4 billion in CHIPS ACT funding from the U.S. Department of Commerce (DoC) as part of a $40 billion expansion of its Austin, Texas, manufacturing facility, along with an R&D fab, a pair of leading-edge logic fabs, and an advanced packaging plant in nearby Taylor, Texas.

Micron and the U.S. government next week will announce $6.1 billion in CHIPS Act funding for the development of advanced memory chips in New York and Idaho, according to AP News.

Cadence unveiled its Palladium Z3 Emulation and Protium X3 FPGA Prototyping systems, targeted at multi-billion-gate designs with 2X increase in capacity and a 1.5X performance increase compared to previous-generation systems. Cadence also teamed up with MemVerge to enable seamless support for AWS Spot instances for long-running high-memory EDA jobs, and extended its hybrid cloud environment solutions through a collaboration with NetApp.

Fig. 2: At CadenceLive Silicon Valley, NVIDIA CEO Jensen Huang (r.) discussed accelerated computing and generative AI with Cadence CEO Anirudh Devgan. Source: Semiconductor Engineering

Quick links to more news:

Global
Markets and Money
In-Depth
Security
Education and Workforce
Product and Standards
Research
Quantum
Events
Further Reading

Global

After Taiwan’s recent 7.2 magnitude earthquake, TSMC reached more the 70% tool recovery in its fabs within the first 10 hours and full recovery by the end of the third day, according to this week’s earnings call. Some wafers in process were scrapped but the company expects the lost production to be recovered in the second quarter.  Also in the call, TSMC said they expect their “customers to share some of the higher cost” of the overseas fabs and higher electricity costs.

Advantest‘s regional headquarters in Taiwan donated $2.2 million New Taiwan dollars ($680,000 US) for aid to victims and reconstruction efforts related to the Taiwan earthquake that struck on April 3.

Japan’s exports grew by more than 7% YoY in March, driven by an 11.3% increase in shipments of electronics and semiconductor manufacturing equipment, much of it to China, according to NikkeiAsia.

China‘s IC output grew 40% in the first quarter, primarily driven by EVs and smartphones, according to the South China Morning Post.

In the U.S., the Biden Administration released a notice of funding opportunity of $50 million targeted at small businesses pursuing advances in metrology research and technology. Also, the U.S. Department of Energy announced a $33 million funding opportunity for smart manufacturing technologies.

Germany‘s Fraunhofer IIS launched its On-Board Processor (FOBP) for the German Space Agency’s Heinrich Hertz communication satellite. FOBP can be controlled and reprogrammed from Earth and will be used to investigate creation of hybrid communication networks.

Markets and Money

RISC-V startup Rivos raised more than $250 million in capital investments to tape out its first power-optimized chips for data analytics and generative AI applications.

Silvaco filed to go public on Nasdaq. The company also received a $5 million convertible note investment from Microchip.

Microchip acquired Neuronix AI Labs to provide AI-enabled FPGA solutions for large-scale, high-performance edge applications.

The advanced packaging market saw a modest 4% increase in revenues in Q4 2023 versus the previous quarter, with a projected decline of 13% QoQ in the first quarter of 2024, reports Yole. Overall, the market is expected to increase from $38 billion in 2023 to $69.5 billion in 2029 with a CAGR of 10.7%.

TSMC’s CoWoS total capacity will increase by 150% in 2024 due to demand for NVIDIA’s Blackwell Platform, reports TrendForce.

ASML saw a nearly 40% drop in new litho equipment sales QoQ in Q1 2024 and a 61% drop in net bookings as manufacturers reduced investments in new capital equipment during the recent semiconductor market slump.

Global PC shipments rose about 3% YoY in Q1 2024, and that same growth is expected for full year 2024, reports Counterpoint. Manufacturers are predicted to promote AI PCs as semiconductor companies prepare to launch SoCs featuring higher TOPS.

The GenAI smartphone market share is predicted to reach 11% by 2024 and 43% by 2027, reports Counterpoint. Samsung likely will lead in 2024, but Apple may overtake it in 2025.

The RF GaN market is expected to exceed $2 billion by 2029, fueled by the defense and telecom infrastructure sectors, reports Yole.

In-Depth

Semiconductor Engineering published its Manufacturing, Packaging & Materials newsletter this week. Top articles include:

• Electromigration Concerns Grow In Advanced Packages
• What Works Best For Chiplets
• Enabling Advanced Devices With Atomic Layer Processes

Plus, check out these new stories and tech talks:

• Architecting Chips For High-Performance Computing
• Future-Proofing Automotive V2X
• Secure Movement Of Data In Test
• Challenges With Chiplets and Power Delivery

Security

In security research:

• Seoul National University, Sandia National Laboratories, Texas A&M University, and Applied Materials demonstrated a memristor crossbar architecture for encryption and decryption.
• Robert Bosch, Forschungszentrum Julich, and Newcastle University investigated techniques for error detection and correction in in-memory computing.
• The University of Florida introduced an automated framework that can help identify security assets for a design at the register-transfer level (RTL).

DARPA conducted successful in-air tests of AI flying an F-16 autonomously versus a human-piloted F-16 in visual-range combat scenarios.

The National Security Agency’s Artificial Intelligence Security Center (NSA AISC) published joint guidance on deploying AI systems securely with the Cybersecurity and Infrastructure Security Agency (CISA), the Federal Bureau of Investigation (FBI), and international partners. CISA also issued other alerts.

Products and Standards

Samsung uncorked LPDDR5X DRAM built on a 12nm process that supports up to 10.7 Gbps and expands the single package capacity of mobile DRAM up to 32 GB.

Keysight revealed its next-generation RF circuit simulation tool that supports multi-physics co-design of circuit, electromagnetic, and electrothermal simulations across Cadence, Synopsys, and Keysight platforms.

Renesas released its FemtoClock family of ultra-low jitter clock generators and jitter attenuators with 8 and 12 outputs, enabling clock tree designs for high-speed interconnect systems in telecom and data center switches, routers, medical imaging, and more.

Movellus expanded its droop response solutions with Aeonic Generate AWM3, which responds to voltage droops within 1 to 2 clock cycles while providing enhanced observability for droop profiling and enabling fine-grained dynamic frequency scaling.

Efabless announced the second version of its Python-based open-source EDA software for construction of customizable flows using proprietary or open-source tools.

Faraday Technology licensed Arm’s Cortex-A720AE IP to use in the development of AI-enabled vehicle ASICs. Also, Untether AI teamed up with Arm to enable its inference acceleration technology to be implemented alongside the latest-generation Automotive Enhanced technology from Arm for ADAS and autonomous vehicle applications.

FOXESS used Infineon’s 1,200V CoolSiC MOSFETs and EiceDRIVER gate drivers for industrial energy storage applications, aiming to promote green energy.

Emotors adopted Siemens’ Simcenter solutions for NVH testing of next-gen automotive e-drives.

SiTime debuted a family of clock generators for AI datacenter applications with clock, oscillator, and resonator in an integrated chip.

JEDEC published the JESD79-5C DDR5 SDRAM standard, which includes a DRAM data integrity improvement called Per-Row Activation Counting (PRAC) that precisely counts DRAM activations on a wordline granularity and alerts the system to pause traffic and designate time for mitigation measures when an excessive number of activations are detected.

The LoRa Alliance launched its roadmap for the development of the LoRaWAN open standard for IoT communications, referring to long-range radio (LoRa) low-power wide-area networks (LPWANs).

Education and Workforce

Texas A&M introduced a new Master of Science program for microelectronics and semiconductors, which will begin in fall 2025.

The Cornell NanoScale Science and Technology Facility (CNF) is partnering with Tompkins Cortland Community College and Penn State to offer a free Microelectronics and Nanomanufacturing Certificate Program to veterans and their dependents.

Eindhoven University of Technology (TU/e) has more than 700 researchers and 25 research group focused on the chip industry, but the number is projected to grow significantly due to the Dutch government’s recent investment.

Research

Intel announced a large-scale neuromorphic system based on its Loihi 2 processor. Initially deployed at Sandia National Laboratories, it aims to support research for future brain-inspired AI. Intel is also collaborating with Seekr on next-gen LLM and foundation models.

Los Alamos National Lab, HPE, and NVIDIA collaborated on the design and installation of Venado, the Lab’s new supercomputer. “Venado adds to our cutting-edge supercomputing that advances national security and basic research, and it will accelerate how we integrate artificial intelligence into meeting those challenges,” said Thom Mason, director of Los Alamos National Laboratory in a release.

Penn State is partnering with Morgan Advanced Materials on a five-year, multi-million-dollar research project to advance silicon carbide (SiC) technology. Morgan will become a founding member of the Penn State Silicon Carbide Innovation Alliance. Also, Coherent secured CHIPS Act funding of $15 million for research into high-voltage, high-power silicon carbide and single-crystal diamond semiconductors.

Oak Ridge National Laboratory (ORNL) researchers found a more efficient way to extract lithium from waste liquids leached from mining sites, oil fields, and used batteries.

Quantum

Quantinuum said it reached an inherent 99.9% 2-qubit gate fidelity in its commercial quantum computer, a point at which quantum error correction protocols can be used to greatly reduce error rates.

D-Wave Quantum uncorked a fast-anneal feature to speed up computations on its quantum processing units, which reduces the impact of external disturbances.

MIT researchers outlined a new conceptual model for a quantum computer that aims to make writing code for them easier.

SLAC National Accelerator Laboratory, Stanford University, Max Planck Institute of Quantum Optics, Ludwig-Maximilians-Universitat Munich, and Instituto de Ciencia de Materiales de Madrid researchers proposed a method that harnesses the structure of light to tweak the properties of quantum materials.

Events

Find upcoming chip industry events here, including:

Upcoming webinars are here.

Further Reading

Read the latest special reports and top stories, or check out the latest newsletters:

Systems and Design
Low Power-High Performance
Test, Measurement and Analytics
Manufacturing, Packaging and Materials
Automotive, Security and Pervasive Computing

The post Chip Industry Week In Review appeared first on Semiconductor Engineering.

The semiconductor industry is preparing for the migration from proprietary chiplet-based systems to a more open chiplet ecosystem, in which chiplets fabricated by different companies of various technologies and device nodes can be integrated in a single package with acceptable yield.

To make this work as expected, the chip industry will have to solve a variety of well-documented technical and business issues, and it will have to rein in some of the grander visions of what’s possible — at least initially. The basic challenge is aligning domain-specific performance demands of end systems, which contain a growing number of chiplets, with the assembly and packaging capabilities and methodologies of IDMs, foundries, and OSATs. This includes the creation of assembly development kits (ADKs) that are roughly the equivalent of process development kits (PDKs), which today are codified with manufacturing specifications.

A PDK provides the appropriate level of detail needed to develop planar chips, marrying design tools with fab processes to achieve a predictable outcome. But making this work for an ADK with heterogeneous chiplets is many times more complex. Design and assembly teams need to manage thermal, mechanical, and electrical co-dependencies that cause electrical and mechanical stress, resulting in warpage, reduced yield, and reliability issues under real-world workloads. Layered on top of this the business and legal issues related to packaging of different devices from different manufacturers.

“Chiplets are a growing trend, especially in the HPC and networking segments, with potential to scale to other applications,” said Gabriela Pereira, technology and market analyst for semiconductor packaging at Yole Intelligence. “The industry has understood that high-end advanced packaging technologies are needed to connect them — but that’s much more complex than it seems. Connecting chiplets requires the design of high-bandwidth interconnections at the package level, which can take different forms — e.g., 2D, 2.5D or 3D — while ensuring that the thermal and power requirements are fulfilled.”

Commercial chiplet-based devices generally are domain-specific, and sometimes developed for a specific workload. So despite a big industry push to create a LEGO-like mix-and-match ecosystem for chiplets — which today includes multiple IP and EDA vendors, foundries, memory suppliers, OSATs, substrate suppliers, etc. — making this work as planned will require time and a massive amount of work.

Fig. 1: System assembly requires tighter coupling between chipmakers and OSATs. Source: ASE

In creating heterogeneous integrated designs, it’s essential to have much tighter collaboration between foundries, IDMs, OSATs, and PCB manufacturers. And because each chiplet-based system will be customized, the number of assembly processes will grow substantially. For example, one OSAT noted that among its ~5,000 customers, there are ~1,000 different assembly processes.

That diversity in products and processes makes it difficult to achieve predictable results by choosing chiplets from a large menu of options.

“We’ve already encountered a lot of limitations including not only the silicon, but also integration and the ecosystem,” said Lihong Cao, senior director at ASE Group, at MEPTEC’s Road to Chiplets forum. She stressed that customers continue to push for a low-cost chiplet assembly process, which is creating constructive tension between developing a sophisticated assembly process and the economic realities of different industry sectors. Computing devices for automotive have a higher cost sensitivity than for data centers, for example, but their chips operate in a harsher environment over a longer lifetime.

What’s needed is a defined set of assembly process recipes — basically, a highly limited menu of choices — that are specific to the end application (HPC, automotive, RF telecommunications) in order to lower the cost of chiplet-based systems. OSATs and foundries already are moving in that direction for high-performance computing. For example, at its 2024 Direct Connect event, Intel shared its six different package processes for chiplets. TSMC and Samsung also offer defined sets of chiplet processes. But the success of these assembly processes requires engineering teams to co-optimize the flows, processes, and materials to best match the system requirements.

Fig. 2: Integrated platform development requires tightly coupled architectural analysis that co-optimizes the system design to architecture to assembly process and packaging material selections. Source: Applied Materials

“Previously, when we designed a system we only had to be worried about the system requirements. Once we start segregating into dies and reassembling them, we have to start looking at other things. We have to worry about putting them together while considering signal integrity between dies, reliability, thermals, etc.,” said Itai Leshniak, director of AI systems solutions at Applied Materials, at the MEPTEC forum. “If we take the case of AI-based computer vision, we can break it down layer by layer — on the hardware side, determining which computer vision processors, sensors, filters are needed to break it down into the architecture at layer. Then we begin to go through how to package all these chiplets, and then which materials to use and how to take advantage of those materials.”

Materials and assembly processes
Conceptually, design engineers will use chiplets to design a system. However, the co-design and integration is far more complicated than assembling a set of LEGO blocks, because the chiplets, interposers, and package substrates come from different design houses and manufacturing facilities. The advanced packaging technologies used to connect chiplets vary with an alphabet soup of names — FOWLP, FOPLP, CoWoS, etc., each of which poses additional design and material choices along with certain process limitations.

Fig. 3: There are a multitude of choices in multi-die packaging from the high-level layout to substrates, materials, bonding methods, and cooling materials. Source: Synopsys

Currently engineering teams determine the tradeoffs among the different packaging options to select materials, derive a process recipe, and determine design rules.

Materials are a good starting point. “Materials are very important because they enable new products and packaging technologies,” Tanja Braun, deputy group manager at the Fraunhofer Institute for Reliability and Microintegration IZM. “As you move into more advanced packaging, process is getting much more complex because you are putting more things together. In the end, it’s a combination of equipment, materials, and process development.”

There are three thermal parameters that are critical in package assembly processes — coefficients of thermal expansion (CTE), glass transition temperature (T_g), and thermal conductivity. These factors affect how a material behaves in manufacturing to packaging processes, as well as how it behaves in the field.

“Challenges for our materials include temperature limitations of different die,” said Rama Puligadda, CTO at Brewer Science. “We have to ensure that the temperatures used for bonding materials don’t exceed the thermal limitations of any of the chips that are being integrated into the package. Additionally, there may be some subsequent processes like redistribution layer (RDL) formation or molding. Our materials have to survive those processes. They have to survive the chemicals they come in contact with throughout the packaging process scheme. Mechanical stresses in the package add additional challenges for bonding materials.”

Within a stack of chiplets-on-substrate with an optional interposer, their material attributes affect the thermal-mechanical stresses between neighboring materials, as well. This directly impacts interconnect dimensional control over a large area substrate area.

“If you go work the numbers, you will find that the level of tolerance and control required is frightening,” said Dick Otte, CEO of Promex Industries. “You’re talking about controlling dimensions equivalent to the width of a grass blade over the length of a football field, so that’s roughly 1 in 100,000.”

The goal is uniform heating of the structure in reflow in order to attain the best process results and to avoid cracking. “When you’re taking it through a 250 degrees centigrade temperature change, then you need to heat up slowly so that the top doesn’t get hot before the bottom does,” said Otte.

Multi-physics to comprehend co-optimization
Multi-physics modeling has become the go-to method for co-optimizing packaging design and assembly process development. That affects both permanent and temporary materials, as well the placement of processors, memories, and other components.

“You always looking to what the customer needs electrically, because that’s going to help define the material set. The material set is broadly applicable to a bunch of speed ranges. As long as you don’t step outside of those electrical specifications, theoretically you should be okay,” said Mike Kelly, vice president of advanced package and technology integration at Amkor Technology.

To save many iterations of empirically based development, engineers can use physics-based simulations to understand the impact of a material set’s properties impact on the assembly process, power/thermals, and mechanical vibrations.

Consider that HPC chiplet products can consume ~1,000 watts at peak performance so the power and thermal interactions need to be fully understood.

“We’ve struggled, as everybody has, with this blizzard of complexity in the different techniques. Not only do they vary across different vendors, but they’re also varying over time,” said Marc Swinnen, director of product marketing at Ansys. “Our approach has been to identify the essentials that need to be worked on. We work jointly with customers to develop a simulation flow that actually achieves what is needed now.”

Materials are just one piece of the puzzle. “Then there’s the assembly stresses that need to be modeled to know whether you can correctly assemble this device. The third one is mechanical vibration,” Swinnen said. “Can your device withstand those regular vibrations? Modeling these attributes ties directly into our mechanical analysis tools — acoustic, thermal, vibration, etc. In the end, you’re going to have to do physics simulation. We’re trying to make it accessible to people in many different forms. But the bedrock of our tool offerings is that we have the meshing simulation and analysis. It’s a question of getting the data in the right format in a way that’s practical and usable.”

Evolving assembly design kits
For conventional packages, OSATs provide design rules for each packaging technology. These need to consider electrical, mechanical and thermal design requirements and manufacturing process limitations. In effect this is a multi-dimensional bounding box. Suppliers perform iterations with the customer to create a product specific process recipe.

Rules cover the macro-level attributes. “At a minimum, what you see from design rules is maximum package size, maximum silicon size, and whether silicon can be [mounted] on both sides of the substrate, such that when you follow these constructions the final product will have a lifetime of 1,000 thermal cycles, for example,” said Fraunhofer’s Braun.

In addition, design rules need to describe routing constraints for the interposer and/or redistribution layer, such as RDL line widths and spaces, ball-grid/pillar/pad size and pitches, and the maximum number of interconnections.

Breaking up a monolithic HPC device into multiple dies shifts some of the semiconductor design/process complexity into the packaging space. That makes things much more complicated. Consider that to connect 10 dies requires on order of 100,000 traces within the interposer’s or substrate’s redistribution layer.

To cope with the complexity at the chip level, the IC industry has long relied upon process design kits (PDKs) to capture design rules in an electronic file that can be imported into EDA tools. Their counterparts, assembly design kits (ADKs), are relatively immature.

“We call it Smart Package,” said Amkor’s Kelly. “It’s an ADK that we give to every customer who’s doing their own design. It is a set of macros, and a customization of a database tailored to a customer’s particular design. For chiplets, it is a high-density fan-out package technology. And it’s cognizant of the limitations for metal density and metal spacing, etc. This makes it easier for us to do design rule checks (DRCs).”

But right now, with the level of customization still required, how an ADK is derived and what it entails is in flux. Partnerships between EDA tool vendors, OSATs, and semiconductor device providers are required.

“We come from the IC world where everything is very rigid,” said Kenneth Larsen, director of 3D-IC product management in Synopsys‘ EDA Group. “On the OSAT side, and maybe this is because it’s so custom, design rules seem like a data sheet. Then you build and optimize the products over time or in collaboration with the OSAT. It’s not an electronic exchange. In the IC world, this would be totally unheard of. While it is possible to tweak a few things, you have a qualification process. And it seems like that’s not there yet for packaging.”

Materials and associated assembly recipes ultimately drive what’s possible for a chiplet-substrate stack in terms of pillar pitch, RDL line widths and spaces, bonding processes, and chiplet placement tolerances. But within a handful of ADKs, there are many possible interactions to consider.

The current focus is on co-optimizing the system design with the chiplet assembly process, leading to an assembly process development flow (see figure 4). This flow considers the needs of customization of an assembly process, and it creates the necessary design rules to be used by package designers.

Fig. 4: Chip-package hybrid flow. Source: ASE

“First you need to define your structure using chiplets. Are you using substrate RDL, 2.5D RDL, or a bridge? After that you need to consider your structure’s materials. What kind of material do you choose to fulfill your electrical performance and the mechanical stress requirements,” said Cao. “After that, you do pre-analysis to ensure all the structures and materials you use are workable in terms of electrical, warpage and mechanical stress.”

The design planning flow also includes the evaluation of die-to-die interconnects through the documents for co-design sign-off.

Conclusion
Before chiplet-based designs can be enabled outside the IDM model, the industry needs to complete the ecosystem that bridges the manufacturing and design complexity. This is because the need to co-optimize the system architecture based on materials, process, and integration capabilities is essential. While this would be easier with a set of well-defined products for the chiplet ecosystem to drive forward on, that has not happened yet.

Engineering teams across the design and manufacturing stack will need to collaborate to choose the appropriate materials, architectures, processes, etc., to develop a final chiplet-based product that is designable. As ASE group’s Cao noted, “An integrated design and manufacturing ecosystem is important. It is very critical to have collaboration among IDM, vendors, materials suppliers. Everyone needs to work together to really enable integration for the real applications.”

Related stories
Fan-Out Packaging Gets Competitive
Manufacturability reaches sufficient level to compete with flip-chip BGA and 2.5D.

Inside Panel-Level Fan-Out Technology
Fraunhofer’s panel experts dig into why this approach is needed and where the challenges are to making it work.

Next Steps For Panel-Level Packaging
Where it’s working, and what challenges remain for even broader adoption.

Mini-Consortia Forming Around Chiplets
Commercial chiplet marketplaces are still on the distant horizon, but companies are getting an early start with more limited partnerships.

What Can Go Wrong In Heterogeneous Integration
Workflows and tools are disconnected, mechanical stress is ill-defined, and complete co-planarity is nearly impossible. But there are solutions on the horizon.

Mechanical Challenges Rise With Heterogeneous Integration
But gaps in tools make it difficult to address warpage, structural issues, and new materials in multi-die/multi-chiplet designs.

The post What Works Best For Chiplets appeared first on Semiconductor Engineering.

Automotive processors are rapidly adopting advanced process nodes. NXP announced the development of 5 nm automotive processors in 2020 [1], Mobileye announced EyeQ Ultra using 5 nm technology during CES 2022 [2], and TSMC announced its “Auto Early” 3 nm processes in 2023 [3]. In the past, the automotive industry was slow to adopt the latest semiconductor technologies due to reliability concerns and lack of a compelling need. Not anymore.

The use of advanced processes necessitates the use of advanced packaging as seen in high performance computing (HPC) and mobile applications because [4][5]:

1. While transistor density has skyrocketed, I/O density has not increased proportionally and is holding back chip size reductions.
2. Processors have heterogeneous, specialized blocks to support today’s workloads.
3. Maximum chip sizes are limited by the slowdown of transistor scaling, photo reticle limits and lower yields.
4. Cost per transistor improvements have slowed down with advanced nodes.
5. Off-package dynamic random-access memory (DRAM) throttles memory bandwidth.

These have been drivers for the use of advanced packages like fan-out in mobile and 2.5D/3D in HPC. In addition, these drivers are slowly but surely showing up in automotive compute units in a variety of automotive architectures as well (see figure 1).

Fig. 1: Vehicle E/E architectures. (Image courtesy of Amkor Technology)

Vehicle electrical/electronic (E/E) architectures have evolved from 100+ distributed electronic control units (ECUs) to 10+ domain control units (DCUs) [6]. The most recent architecture introduces zonal or zone ECUs that are clustered in physical locations in cars and connect to powerful central computing units for processing. These newer architectures improve scalability, cost, and reliability of software-defined vehicles (SDVs) [7]. The processors in each of these architectures are more complex than those in the previous generation.

Multiple cameras, radar, lidar and ultrasonic sensors and more feed data into the compute units. Processing and inferencing this data require specialized functional blocks on the processor. For example, the Tesla Full Self-Driving (FSD) HW 3.0 system on chip (SoC) has central processing units (CPUs), graphic processing units (GPUs), neural network processing units, Low-Power Double Data Rate 4 (LPDDR4) controllers and other functional blocks – all integrated on a single piece of silicon [8]. Similarly, Mobileye EyeQ6 has functional blocks of CPU clusters, accelerator clusters, GPUs and an LPDDR5 interface [9]. As more functional blocks are introduced, the chip size and complexity will continue to increase. Instead of a single, monolithic silicon chip, a chiplet approach with separate functional blocks allows intellectual property (IP) reuse along with optimal process nodes for each functional block [10]. Additionally, large, monolithic pieces of silicon built on advanced processes tend to have yield challenges, which can also be overcome using chiplets.

Current advanced driver-assistance systems (ADAS) applications require a DRAM bandwidth of less than 60GB/s, which can be supported with standard double data rate (DDR) and LPDDR solutions. However, ADAS Level 4 and Level 5 will need up to 1024 GB/s memory bandwidth, which will require the use of solutions such as Graphic DDR (GDDR) or High Bandwidth Memory (HBM) [11][12].

Fig. 2: Automotive compute package roadmap. (Image courtesy of Amkor Technology)

Automotive processors have been using Flip Chip BGA (FCBGA) packages since 2010. FCBGA has become the mainstay of several automotive SoCs, such as EyeQ from Mobileye, Tesla FSD and NVIDIA Drive. Consumer applications of FCBGA packaging started around 1995 [13], so it took more than 15 years for this package to be adopted by the automotive industry. Computing units in the form of multichip modules (MCMs) or System-in-Package (SiP) have also been in automotive use since the early 2010s for infotainment processors. The use of MCMs is likely to increase in automotive compute to enable components like the SoC, DRAM and power management integrated circuit (PMIC) to communicate with each other without sending signals off-package.

As cars move to a central computing architecture, the SoCs will become more complex and run into size and cost challenges. Splitting these SoCs into chiplets becomes a logical solution and packaging these chiplets using fan-out or 2.5D packages becomes necessary. Just as FCBGA and MCMs transitioned into automotive from non-automotive applications, so will fan-out and 2.5D packaging for automotive compute processors (see figure 2). The automotive industry is cautious but the abovementioned architecture changes are pushing faster adoption of advanced packages. Materials, processes, and factory controls are key considerations for successful qualification of these packages in automotive compute applications.

In summary, the automotive industry is adopting advanced semiconductor technologies, such as 5 nm and 3 nm processes, which require the use of advanced packaging due to limitations in I/O density, chip size reductions, and memory bandwidth. Processors in the latest vehicle E/E architectures are more complex and require specialized functional blocks to process data from multiple sensors. As cars move to the central computing architecture, the SoCs will become more complex and run into size and cost challenges. Splitting these SoCs into chiplets becomes a logical solution and packaging these chiplets using fan-out or 2.5D technology becomes necessary.

Sources

1. NXP. “NXP Selects TSMC 5nm Process for Next-Generation High-Performance Automotive Platform.” NXP, https://www.nxp.com/company/about-nxp/nxp-selects-tsmc-5nm-process-for-next-generation-high-performance-automotive-platform:NW-TSMC-5NM-HIGH-PERFORMANCE.
2. Mobileye. “Mobileye at CES 2022.” Mobileye, https://www.mobileye.com/news/mobileye-ces-2022-tech-news/.
3. Business Wire. “TSMC Showcases New Technology Developments at 2023 Technology Symposium.” Business Wire, https://www.businesswire.com/news/home/20230426005359/en/TSMC-Showcases-New-Technology-Developments-at-2023-Technology-Symposium.
4. Swaminathan, Raja. “Advanced Packaging: Enabling Moore’s Law’s Next Frontier Through Heterogeneous Integration.” HotChips33, https://hc33.hotchips.org/assets/program/tutorials/2021%20Hot%20Chips%20AMD%20Advanced%20Packaging%20Swaminathan%20Final%20%2020210820.pdf
5. SemiAnalysis. “Advanced Packaging Part 1” SemiAnalysis, https://www.semianalysis.com/p/advanced-packaging-part-1-pad-limited?utm_source=%2Fsearch%2Fadvanced%2520packaging&utm_medium=reader2.
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The integration of multiple dies within a single package increasingly is viewed as the next evolution for extending Moore’s Law, but it also presents myriad challenges — particularly in achieving a universally accepted standard integrating plug-and-play chiplets from different vendors.

“In some respects, people are already doing this,” says Debendra Das Sharma, Intel senior fellow and chair of the UCIe Consortium. “They’re putting multiple dies on the same package, and we’ve been doing it for decades back to what was multi-chip modules (MCMs). And if you look in our mainstream CPUs today, they’re all multiple chips on the same package.”

Combining more than one chip in a package becomes a lot more complicated, however, when those chips have different functions or come from different vendors or foundries. That’s where a standard like UCIe becomes necessary.

“For most of the multi-chip products that are in the market, the same company is designing and providing the multiple dies, so they know exactly how they talk to each other and how to divide or partition the chip,” says Vik Chaudhry, senior director of product marketing and business development at Amkor. “That makes it a little easier to understand how one part talks to the other. What UCIe is trying to do is standardize that interconnect between multiple vendors.”

While other protocols like Bunch of Wires (BoW) have made significant strides in recent years and are still being developed, UCIe stands out for its backing by many of the largest chip manufacturers and its support for all major packaging technologies, including organic substrates, silicon interposers, and RDL fan-outs.

Fig. 1: Chiplet diagram with UCIe interconnect highlighted. Source: Keysight

But the move toward UCIe compatibility necessitates more than a mere afterthought in the chip creation process. It requires a foundational shift back to the drawing board, where compatibility must be conceived as an integral component of the chip, not retrofitted as an expedient solution. As this standard evolves, it has become increasingly apparent that for chiplets to truly embrace UCIe, the blueprint for their design must be reimagined from the ground up.

“UCIe is a layout,” says Chaudry. “It’s designed. But keep in mind, these chiplets can be from different fab nodes. One could be 5nm, another could be 3nm, and third could be 14nm. Somehow you have to connect these dies together. You need to be compatible in terms of how much space you have to run the routes, and that’s what UCIe is addressing.”

The transition to UCIe is not merely about different vendors adapting to a new standard. It requires a willingness among manufacturers throughout the industry to align their design and production processes with a common protocol that is still, in many respects, a work in progress.

While it is commonly assumed that chiplets plus advanced packaging represent the next evolution for extending Moore’s Law, the lack of a fully defined standard, coupled with the uncertainty surrounding the integration with existing technologies, means investing in new designs for UCIe is currently limited to the largest players in the market.

“Anytime you put multiple dies on a substrate or interposer, it’s challenging,” adds Chaudhry. “As we are seeing AI come into the picture, we are seeing a lot of vendors putting multiple dies on a chip, and not just 3 or 4, but 8, 10, or 12 dies. The complexity exponentially grows as you have more and more dies on the same interposer or substrate. You also have to test everything in between, and that increases the complexity and cost. That’s a huge challenge for anybody, and right now only a few companies in the world are capable of committing those kinds of resources and those kinds of expenses to put a line together.”

Moreover, the adoption of UCIe still must overcome significant hurdles in terms of scalability, compatibility with existing systems, and ensuring that the cost implications do not outweigh the benefits.

The chiplet evolution
Large chipmakers have been constrained by the size of the reticle field for at least the last several process nodes, which sharply limited the number of features that could be crammed onto a planar SoC. Today, with node shrinks becoming more costly and challenging, the best solution available is to decompose the SoC into individual blocks, or chiplets.

“Once the dies become really big, you’re up against the reticle limit,” says Intel’s Das Sharma. “That’s where you will see a lot of people deploying chiplets. You’re basically having multiple sets of chips being packaged together to deliver a certain set of functionality.”

Take, for instance, the leap to 50 Tb per second switches that are challenging the limits of reticle size. There’s a growing need to dissect and distribute the functionality of these chips across multiple components. Whether it’s the I/O, memory, or SRAM, the key lies in strategically breaking down the SoC into smaller units. This not only makes the manufacturing process more feasible, but also opens doors to more innovative and efficient design architectures.

It also provides some immediate benefits. Smaller dies yield better than larger ones, which is why in 2012 Xilinx split its 28nm FPGA into four different dies, connected through an interposer. It also provides room to grow, because the individual chiplets are still well below the reticle limit.

But all of the early implementations were homogeneous. They were all developed by the same vendor using the same process technology. A big benefit of advanced packaging is the ability to combine heterogeneous chiplets in the same package, allowing analog circuits and less-critical features to be developed at whatever process node makes sense. This is the challenge facing large chipmakers, foundries, and OSATs today, and it’s one that has not yet been fully solved.

Nevertheless, the chip industry agrees on one thing. There needs to be a common way to connect all of these chiplets together, and this is where UCIe fits into the picture.

The UCIe standard
Achieving a consensus on the electrical characteristics that underpin the UCIe is akin to orchestrating a symphony with a multitude of instruments, each with its own acoustic signature. Ensuring that chiplets from different corners of the industry can connect and communicate efficiently necessitates bridging gaps in voltage levels, signal timing, and power distribution.

In March, 2022, the UCIe consortium released UCIe 1.0 that included specifications for a standardized physical die-to-die interface designed to facilitate seamless communication between chiplets, regardless where they were manufactured or by whom. The specifications encompassed key aspects, such as electrical properties, physical dimensions, and protocols necessary for ensuring compatibility and efficient data transfer between diverse chip components.

“On advanced packages at 45 microns, the numbers are pretty stellar,” says Das Sharma. “You have 188 gigabytes per second per square millimeter as a starting point, up to 1.35 terabytes per second per square millimeter. People will have a hard time even absorbing that kind of bandwidth and processing it.”

UCIe 1.0 uses a layered protocol approach. The physical layer underpins the protocol stack, dedicated to defining and managing electrical signaling, such as clock synchronization and link training, while also incorporating sideband communication channels essential for non-data interactions between chiplets.

At the heart of UCIe’s mechanics is the Die-to-Die (D2D) adapter. This crucial interface acts as the gatekeeper, managing link state and facilitating negotiation parameters for chiplets, crucial for establishing reliable chiplet communication. It optionally extends a safeguard for data integrity through mechanisms like cyclic redundancy check (CRC) and link-level retry capabilities. This not only ensures accuracy in high-speed data transfer, but also aligns different chiplet protocols by providing an arbitration system enabling multiple chips to interact efficiently.

“UCIe is pretty flexible in that way,” says Chaudhry. “It supports your PCIe protocols, XML protocol, or streaming, so you can decide which protocol you want to support. And it has different data rates that it supports. It’s the lowest common denominator that everybody will support. If you’re on a 3nm process, you can support a much higher data rate, but if the other chiplet is at a different process node, then both the parts will support the basic lowest common denominator of the spec, and then you can talk on that.”

UCIe also incorporates strategies to mitigate interconnect defects, such as stuck-at faults and signal discontinuities. Stipulations within UCIe include the implementation of auxiliary pathways, furnishing a means to maintain connectivity if the primary lanes fail. This redundancy helps sustain system functionality by providing avenues for fault tolerance and repair.

UCIe also embraces existing standards such as PCI Express (PCIe) and Compute Express Link (CXL) natively, ensuring a broad resonance across the industry by capitalizing on these well-established protocols. The layered approach of UCIe also encompasses comprehensive usage models.

In August 2023, the consortium published UCIe version 1.1, extending reliability mechanisms to more protocols and supporting additional usage models. These enhancements are not merely incremental. They are geared towards pivotal segments such as automotive, which is gravitating toward chiplets.

One key area where the evolution from UCIe 1.0 to 1.1 becomes evident is in the standard’s preventive monitoring features. UCIe 1.1 expands the protocol with new registers designed to capture detailed Eye Margin information — viewing both width and height — which provides standardized reporting formats and proactive link health monitoring. Rather than reinventing the wheel, UCIe 1.1 leverages the existing periodic parity Flit injection mechanism from version 1.0, enhancing error detection and reporting capabilities through a new error log register. That, in turn, allows for improved assessment of link repair necessities. UCIe 1.1 also offers enhancements for compliance testing.

Another notable aspect is the advent of new and emerging usages, particularly with streaming protocols. Whereas UCIe 1.0’s support for such protocols was restricted to Raw Mode, UCIe 1.1 extends the utility of the die-to-die (D2D) adapter on the FDI interface to streaming protocols. This extension enables a blend of CRC retry power management features and facilitates the coexistence of multiple protocols.

UCIe 1.1 also considers cost optimization for advanced packaging solutions in anticipation of shrinking bump pitches and the advent of 3D integration. The introduction of additional column arrangements in UCIe 1.1 creates broader opportunities for mix-and-match dies.

“In a chiplet environment, the dies are very close to each other and your shoreline is very limited,” says Chaudhry. “You have limited space to connect the dies, and how the number of pins are connected, facing each other, that becomes critical. That is one thing that UCIe is addressing. What should be the pin location? Whether it’s 6-, 8-, or 16-column, how do you arrange it so that when one vendor has an 8-column configuration, they can talk to one with a 12 column configuration and connect to it physically, not just in terms of pins, but also connectivity and shoreline compatibility?”

Designing for interoperability
There are a number of technical hurdles that still stand in the way of the widespread adoption of UCIe. These include a need for precise electrical conformity, predictable signaling realms, and systematic physical interconnects catering to a variety of nodes and manufacturing processes.

“You can also have HBM in there, which can be very tall compared to a single ASIC,” says Amkor’s Chaudhry. “How do you address those height differences? A lot of different issues come into play when you’re putting different dies and different chiplets together.”

Thermal management is also a key element for high-density packaging. Disparate process nodes inevitably present distinct power profiles and heat dissipation characteristics. Bridging these gaps necessitates innovative heat distribution methodologies and sophisticate warpage control to ensure structural integrity and reliable function in complex modules.

“There are a lot of challenges in thermal,” adds Chaudhry. “When you have two dies from different process nodes, how do you make sure that you have a way to dissipate the power equally? Those are some of the challenges as we go along and there’s no general solution to that yet. Those are kind of things that the consortium is looking at right now.”

Continued evolution
Another goal of the UCIe consortium is to ensure that anyone developing a chiplet today will still be able to use that design five years from now, despite progress in the standard during that time.

“It will absolutely evolve,” adds Chaudhry. “PCI did the same thing. They are on Gen 5 or Gen 6 now. USB is the same way with USB 4.0 coming soon. CXL is at 3.1. We expect the same thing to happen to UCIe. It will continuously improve and come up with new and more flexible solutions that our members can adopt.”

“The more people get involved, the more they’re going to start tweaking things,” adds Das Sharma. “Some of them are not going to work out, and some of them are going to work out really well. This is a multi-decade journey, and the key is to learn and adapt and keep moving on.”

Conclusion
The UCIe initiative aims to revolutionize chip package interconnectivity by emulating the success of Peripheral Component Interconnect Express (PCIe) at the PCB level. By facilitating direct inter-die connections within the chip package, UCIe endeavors to drastically cut power usage, enhance bandwidth efficiency, and, ultimately, reduce production costs.

“The good thing about UCIe is that it’s an open standard,” says Chaudhry. “In all, there are about 120 members, and all of them are working together. There are six different working groups that range from mechanical to electrical to security to software and marketing, where they are bringing up new things as they are developing their chiplet-based designs. A lot of things that have happened between UCIe 1.0 and 1.1 are basically due to their input.”

—Ed Sperling contributed to this report.

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