BAE Systems and GlobalFoundries are teaming up to strengthen the supply of chips for national security programs, aligning technology roadmaps and collaborating on innovation and manufacturing. Focus areas include advanced packaging, GaN-on-silicon chips, silicon photonics, and advanced technology process development.

Onsemi plans to build a $2 billion silicon carbide production plant in the Czech Republic. The site would produce smart power semiconductors for electric vehicles, renewable energy technology, and data centers.

The global chip manufacturing industry is projected to boost capacity by 6% in 2024 and 7% in 2025, reaching 33.7 million 8-inch (200mm) wafers per month, according to SEMI‘s latest World Fab Forecast report. Leading-edge capacity for 5nm nodes and below is expected to grow by 13% in 2024, driven by AI demand for data center applications. Additionally, Intel, Samsung, and TSMC will begin producing 2nm chips using gate-all-around (GAA) FETs next year, boosting leading-edge capacity by 17% in 2025.

At the IEEE Symposium on VLSI Technology & Circuits, imec introduced:

• Functional CMOS-based CFETs with stacked bottom and top source/drain contacts.
• CMOS-based 56Gb/s zero-IF D-band beamforming transmitters to support next-gen short-range, high-speed wireless services at frequencies above 100GHz.
• ADCs for base stations and handsets, a key step toward scalable, high-performance beyond-5G solutions, such as cloud-based AI and extended reality apps.

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Global

Wolfspeed postponed plans to construct a $3 billion chip plant in Germany, underscoring the EU‘s challenges in boosting semiconductor production, reports Reuters. The North Carolina-based company cited reduced capital spending due to a weakened EV market, saying it now aims to start construction in mid-2025, two years later than 0riginally planned.

Micron is building a pilot production line for high-bandwidth memory (HBM) in the U.S., and considering HBM production in Malaysia to meet growing AI demand, according to a Nikkei report. The company is expanding HBM R&D facilities in Boise, Idaho, and eyeing production capacity in Malaysia, while also enhancing its largest HBM facility in Taichung, Taiwan.

Kioxia restored its Yokkaichi and Kitakami plants in Japan to full capacity, ending production cuts as the memory market recovers, according to Nikkei. The company, which is focusing on NAND flash production, has secured new bank credit support, including refinancing a ¥540 billion loan and establishing a ¥210 billion credit line. Kioxia had reduced output by more than 30% in October 2022 due to weak smartphone demand.

Europe’s NATO Innovation Fund announced its first direct investments, which includes semiconductor materials. Twenty-three NATO allies co-invested in this over $1B fund devoted to address critical defense and security challenges.

The second meeting of the U.S.–India Initiative on Critical and Emerging Technology (iCET) was held in New Delhi, with various funding and initiatives announced to support semiconductor technology, next-gen telecommunications, connected and autonomous vehicles, ML, and more.

Amazon announced investments of €10 billion in Germany to drive innovation and support the expansion of its logistics network and cloud infrastructure.

Quantum Machines opened the Israeli Quantum Computing Center (IQCC) research facility, backed by the Israel Innovation Authority and located at Tel Aviv University. Also, Israel-based Classiq is collaborating with NVIDIA and BMW, using quantum computing to find the optimal automotive architecture of electrical and mechanical systems.

Global data center vacancy rates are at historic lows, and power availability is becoming less available, according to a Siemens report featured on Broadband Breakfast. The company called for an influx of financing to find new ways to optimize data center technology and sustainability.

In-Depth

Semiconductor Engineering published its Manufacturing, Packaging & Materials newsletter this week, featuring these top stories:

• Single Vs. Multi-Patterning Advancements For EUV
• Precise Control Of Copper Plating And CMP
• Ruthenium Interconnects On Tap
• Opportunities Grow For GPU Acceleration

More reporting this week:

• IC Industry’s Growing Role In Sustainability
• What’s Missing In Test

Market Reports

Renesas completed its acquisition of Transphorm and will immediately start offering GaN-based power products and reference designs to meet the demand for wide-bandgap (WBG) chips.

Revenues for the top five wafer fab equipment (WFE) companies fell 9% YoY in Q1 2024, according to Counterpoint. This was offset partially by increased demand for NAND and DRAM, which increased 33% YoY, and strong growth in sales to China, which were up 116% YoY.

The SiC power devices industry saw robust growth in 2023, primarily driven by the BEV market, according to TrendForce. The top five suppliers, led by ST with a 32.6% market share and onsemi in second place, accounted for 91.9% of total revenue. However, the anticipated slowdown in BEV sales and weakening industrial demand are expected to significantly decelerate revenue growth in 2024. 

About 30% of vehicles produced globally will have E/E architectures with zonal controllers by 2032, according to McKinsey & Co. The market for automotive micro-components and logic semiconductors is predicted to reach $60 billion in 2032, and the overall automotive semiconductor market is expected to grow from $60 billion to $140 billion in the same period, at a 10% CAGR.

The automotive processor market generated US$20 billion in revenue in 2023, according to Yole. US$7.8 billion was from APUs and FPGAs and $12.2 billion was from MCUs. The ADAS and infotainment processors market was worth US$7.8 billion in 2023 and is predicted to grow to $16.4 billion by 2029 at a 13% CAGR. The market for ADAS sensing is expected to grow at a 7% CAGR.

Security

The CHERI Alliance was established to drive adoption of memory safety and scalable software compartmentalization via the security technology CHERI, or Capability Hardware Enhanced RISC Instructions. Founding members include Capabilities Limited, Codasip, the FreeBSD Foundation, lowRISC, SCI Semiconductor, and the University of Cambridge.

In security research:

• Japan and China researchers explored a NAND-XOR ring oscillator structure to design an entropy source architecture for a true random number generator (TRNG).
• University of Toronto and Carleton University researchers presented a survey examining how hardware is applied to achieve security and how reported attacks have exploited certain defects in hardware.
• University of North Texas and Texas Woman’s University researchers explored the potential of hardware security primitive Physical Unclonable Functions (PUF) for mitigation of visual deepfakes.
• Villanova University researchers proposed the Boolean DERIVativE attack, which generalizes Boolean domain leakage.

Post-quantum cryptography firm PQShield raised $37 million in Series B funding.

Former OpenAI executive, Ilya Sutskever, who quit over safety concerns, launched Safe Superintelligence Inc. (SSI).

EU industry groups warned the European Commission that its proposed cybersecurity certification scheme (EUCS) for cloud services should not discriminate against Amazon, Google, and Microsoft, reported Reuters.

Cyber Europe tested EU cyber preparedness in the energy sector by simulating a series of large-scale cyber incidents in an exercise organized by the European Union Agency for Cybersecurity (ENISA).

The Cybersecurity and Infrastructure Security Agency (CISA) issued a number of alerts/advisories.

Education and Training

New York non-profit NY CREATES and South Korea’s National Nano Fab Center partnered to develop a hub for joint research, aligned technology services, testbed support, and an engineer exchange program to bolster chips-centered R&D, workforce development, and each nation’s high-tech ecosystem.

New York and the Netherlands agreed on a partnership to promote sustainability within the semiconductor industry, enhance workforce development, and boost semiconductor R&D.

Rapidus is set to send 200 engineers to AI chip developer Tenstorrent in the U.S. for training over the next five years, reports Nikkei. This initiative, led by Japan’s Leading-edge Semiconductor Technology Center (LSTC), aims to bolster Japan’s AI chip industry.

Product News

UMC announced its 22nm embedded high voltage (eHV) technology platform for premium smartphone and mobile device displays. The 22eHV platform reduces core device power consumption by up to 30% compared to previous 28nm processes. Die area is reduced by 10% with the industry’s smallest SRAM bit cells.​

Alphawave Semi announced a new 9.2 Gbps HBM3E sub-system silicon platform capable of 1.2 terabytes per second. Based on the HBM3E IP, the sub-system is aimed at addressing the demand for ultra-high-speed connectivity in high-performance compute applications.

Movellus introduced the Aeonic Power product family for on-die voltage regulation, targeting the challenging area of power delivery.

Cadence partnered with Semiwise and sureCore to develop new cryogenic CMOS circuits with possible quantum computing applications. The circuits are based on modified transistors found in the Cadence Spectre Simulation Platform and are capable of processing analog, mixed-signal, and digital circuit simulation and verification at cryogenic temperatures.

Renesas launched R-Car Open Access (RoX), an integrated development platform for software-defined vehicles (SDVs), designed for Renesas R-Car SoCs and MCUs with tools for deployment of AI applications, reducing complexity and saving time and money for car OEMs and Tier 1s.

Infineon released industry-first radiation-hardened 1 and 2 Mb parallel interface ferroelectric-RAM (F-RAM) nonvolatile memory devices, with up to 120 years of data retention at 85-degree Celsius, along with random access and full memory write at bus speeds. Plus, a CoolGaN Transistor 700 V G4 product family for efficient power conversion up to 700 V, ideal for consumer chargers and notebook adapters, data center power supplies, renewable energy inverters, and more.

Ansys adopted NVIDIA’s Omniverse application programming interfaces for its multi-die chip designers. Those APIs will be used for 5G/6G, IoT, AI/ML, cloud computing, and autonomous vehicle applications. The company also announced ConceptEV, an SaaS solution for automotive concept design for EVs.

Fig. 1: Field visualization of 3D-IC with Omniverse. Source: Ansys

QP Technologies announced a new dicing saw for its manufacturing line that can process a full cassette of 300mm wafers 7% faster than existing tools, improving throughput and productivity.

NXP introduced its SAF9xxx of audio DSPs to support the demand for AI-based audio in software-defined vehicles (SDVs) by using Cadence’s Tensilica HiFi 5 DSPs combined with dedicated neural-network engines and hardware-based accelerators.

Avionyx, a provider of software lifecycle engineering in the aerospace and safety-critical systems sector, partnered with Siemens and will leverage its Polarion application lifecycle management (ALM) tool. Also, Dovetail Electric Aviation adopted Siemens Xcelerator to support sustainable aviation.

Research

Researchers from imec and KU Leuven released a +70 page paper “Selecting Alternative Metals for Advanced Interconnects,” addressing interconnect resistance and reliability.

A comprehensive review article — “Future of plasma etching for microelectronics: Challenges and opportunities” — was created by a team of experts from the University of Maryland, Lam Research, IBM, Intel, and many others.

Researchers from the Institut Polytechnique de Paris’s Laboratory of Condensed Matter for Physics developed an approach to investigate defects in semiconductors. The team “determined the spin-dependent electronic structure linked to defects in the arrangement of semiconductor atoms,” the first time this structure has been measured, according to a release.

Lawrence Berkeley National Laboratory-led researchers developed a small enclosed chamber that can hold all the components of an electrochemical reaction, which can be paired with transmission electron microscopy (TEM) to generate precise views of a reaction at atomic scale, and can be frozen to stop the reaction at specific time points. They used the technique to study a copper catalyst.

The Federal Drug Administration (FDA) approved a clinical trial to test a device with 1,024 nanoscale sensors that records brain activity during surgery, developed by engineers at the University of California San Diego (UC San Diego).

Events and Further Reading

Find upcoming chip industry events here, including:

Upcoming webinars are here.

Semiconductor Engineering’s latest newsletters:

Automotive, Security and Pervasive Computing
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The post Chip Industry Week In Review appeared first on Semiconductor Engineering.

Rapidus and IBM are jointly developing mass production capabilities for chiplet-based advanced packages. The collaboration builds on an existing agreement to develop 2nm process technology.

Vanguard and NXP will jointly establish VisionPower Semiconductor Manufacturing Company (VSMC) in Singapore to build a $7.8 billion, 12-inch wafer plant. This is part of a global supply chain shift “Out of China, Out of Taiwan,” according to TrendForce.

Alphawave joined forces with Arm to develop an advanced chiplet based on Arm’s Neoverse Compute Subystems for AI/ML. The chiplet contains the Neoverse N3 CPU core cluster and Arm Coherent Mesh Network, and will be targeted at HPC in data centers, AI/ML applications, and 5G/6G infrastructure.

ElevATE Semiconductor and GlobalFoundries will partner for high-voltage chips to be produced at GF’s facility in Essex Junction, Vermont, which GF bought from IBM. The chips are essential for semiconductor testing equipment, aerospace, and defense systems.

NVIDIA, OpenAI, and Microsoft are under investigation by the U.S. Federal Trade Commission and Justice Department for violation of antitrust laws in the generative AI industry, according to the New York Times.

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Apollo Global Management will invest $11 billion in Intel’s Fab 34 in Ireland, thereby acquiring a 49% stake in Intel’s Irish manufacturing operations.

imec and ASML opened their jointly run High-NA EUV Lithography Lab in Veldhoven, the Netherlands. The lab will be used to prepare  the next-generation litho for high-volume manufacturing, expected to begin in 2025 or 2026.

Expedera opened a new semiconductor IP design center in India. The location, the sixth of its kind for the company, is aimed at helping to make up for a shortfall in trained technicians, researchers, and engineers in the semiconductor sector.

Foxconn will build an advanced computing center in Taiwan with NVIDIA’s Blackwell platform at its core. The site will feature GB200 servers, which consist of 64 racks and 4,608 GPUs, and will be completed by 2026.

Intel and its 14 partner companies in Japan will use Sharp‘s LCD plants to research semiconductor production technology, a cost reduction move that should also produce income for Sharp, according to Nikkei Asia.

Japan is considering legislation to support the commercial production of advanced semiconductors, per Reuters.

Saudi Arabia aims to establish at least 50 semiconductor design companies as part of a new National Semiconductor Hub, funded with over $266 million.

Air Liquide is opening a new industrial gas production facility in Idaho, which will produce ultra-pure nitrogen and other gases for Micron’s new fab.

Microsoft will invest 33.7 billion Swedish crowns ($3.2 billion) to expand its cloud and AI infrastructure in Sweden over a two-year period, reports Bloomberg. The company also will invest $1 billion to establish a new data center in northwest Indiana.

AI data centers could consume as much as 9.1% of the electricity generated in the U.S. by 2030, according to a white paper published by the Electric Power Research Institute. That would more than double the electricity currently consumed by data centers, though EPRI notes this is a worst case scenario and advances in efficiency could be a mitigating factor.

Markets and Money

The Semiconductor Industry Association (SIA) announced global semiconductor sales increased 15.8% year-over-year in April, and the group projected a market growth of 16% in 2024. Conversely, global semiconductor equipment billings contracted 2% year-over-year to US$26.4 billion in Q1 2024, while quarter-over-quarter billings dropped 6% during the same period, according to SEMI‘s Worldwide Semiconductor Equipment Market Statistics (WWSEMS) Report.

Cadence completed its acquisition of BETA CAE Systems International, a provider of multi-domain, engineering simulation solutions.

Cisco‘s investment arm launched a $1 billion fund to aid AI startups as part of its AI innovation strategy. Nearly $200 million has already been earmarked.

The power and RF GaN markets will grow beyond US$2.45 billion and US$1.9 billion in 2029, respectively, according to Yole, which is offering a webinar on the topic.

The micro LED chip market is predicted to reach $580 million by 2028, driven by head-mounted devices and automotive applications, according to TrendForce. The cost of Micro LED chips may eventually come down due to size miniaturization.

In-Depth

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

• The Uncertainty Of Certifying AI For Automotive
• Why It’s So Hard To Secure AI Chips
• Toward A Software-Defined Hardware World

More reporting this week:

• Chip Design Digs Deeper Into AI
• Why IC Design Safety Nets Have Limits
• Opportunities Grow For GPU Acceleration

Security

Scott Best, Rambus senior director of Silicon Security Products, delivered a keynote at the Hardwear.io conference this week (below), detailing a $60 billion reverse engineering threat for hardware in just three markets — $30 billion for printer consumables, $20 billion for rechargeable batteries with some type of authentication, and $10 billion for medical devices such as sonogram probes.

Photo source: Ed Sperling/Semiconductor Engineering

wolfSSL debuted wolfHSM for automotive hardware security modules, with its cryptographic library ported to run in automotive HSMs like Infineon’s Aurix Tricore TC3XX.

Cisco integrated AMD Pensando data processing units (DPUs) with its Hypershield security architecture for defending AI-scale data centers.

OMNIVISION released an intelligent CMOS image sensor for human presence detection, infrared facial authentication, and always-on technology with a single sensing camera. And two new image sensors for industrial and consumer security surveillance cameras.

Digital Catapult announced a new cohort of companies will join Digital Security by Design’s Technology Access Program, gaining access to an Arm Morello prototype evaluation hardware kit based on Capability Hardware Enhanced RISC Instructions (CHERI), to find applications across critical UK sectors.

University of Southampton researchers used formal verification to evaluate the hardware reliability of a RISC-V ibex core in the presence of soft errors.

Several institutions published their students’ master’s and PhD work:

• Virginia Tech published a dissertation proposing sPACtre, a defense mechanism that aims to prevent Spectre control-flow attacks on existing hardware.
• Wright State University published a thesis proposing an approach that uses various machine learning models to bring an improvement in hardware Trojan identification with power signal side channel analysis
• Wright State University published a thesis examining the effect of aging on the reliability of SRAM PUFs used for secure and trusted microelectronics IC applications.
• Nanyang Technological University published a Final Year Project proposing a novel SAT-based circuit preprocessing attack based on the concept of logic cones to enhance the efficacy of SAT attacks on complex circuits like multipliers.

The Cybersecurity and Infrastructure Security Agency (CISA) issued a number of alerts/advisories.

Education and Training

Renesas and the Indian Institute of Technology Hyderabad (IIT Hyderabad) signed a three-year MoU to collaborate on VLSI and embedded semiconductor systems, with a focus on R&D and academic interactions to advance the “Make in India” strategy.

Charlie Parker, senior machine learning engineer at Tignis, presented a talk on “Why Every Fab Should Be Using AI.”

Penn State and the National Sun Yat-Sen University (NSYSU) in Taiwan partnered to develop educational and research programs focused on semiconductors and photonics.

Rapidus and Hokkaido University partnered on education and research to enhance Japan’s scientific and technological capabilities and develop human resources for the semiconductor industry.

The University of Minnesota named Steve Koester its first “Chief Semiconductor Officer,” and launched a website devoted to semiconductor and microelectronics research and education.

The state of Michigan invested $10 million toward semiconductor workforce development.

Product News

Siemens reported breakthroughs in high-level C++ verification that will be used in conjunction with its Catapult software. Designers will be able to use formal property checking via the Catapult Formal Assert software and reachability coverage analysis through Catapult Formal CoverCheck.

Infineon released several products:

• 600 V CoolMOS 8 high voltage superjunction (SJ) MOSFET product family.
• CoolGaN bidirectional switch (BDS) and CoolGaN Smart Sense device.
• New CoolSiC MOSFET discretes 650 V, with two product families housed in the Thin-TOLL 8×8 and TOLT packages to increase system power density.

Augmental, an MIT Media Lab spinoff, released a tongue-based computer controller, dubbed the MouthPad.

NVIDIA revealed a new line of products that will form the basis of next-gen AI data centers. Along with partners ASRock Rack, ASUS, GIGABYTE, Ingrasys, and others, the NVIDIA GPUs and networking tech will offer cloud, on-premises, embedded, and edge AI systems. NVIDIA founder and CEO Jensen Huang showed off the company’s upcoming Rubin platform, which will succeed its current Blackwell platform. The new system will feature new GPUs, an Arm-based CPU and advanced networking with NVLink 6, CX9 SuperNIC and X1600 converged InfiniBand/Ethernet switch.

Intel showed off its Xeon 6 processors at Computex 2024. The company also unveiled architectural details for its Lunar Lake client computing processor, which will use 40% less SoC power, as well as a new NPU, and X2 graphic processing unit cores for gaming.

Research

imec released a roadmap for superconducting digital technology to revolutionize AI/ML.

CEA-Leti reported breakthroughs in three projects it considers key to the next generation of CMOS image sensors. The projects involved embedding AI in the CIS and stacking multiple dies to create 3D architectures.

Researchers from MIT’s Computer Science & Artificial Intelligence Laboratory (MIT-CSAIL) used a type of generative AI, known as diffusion models, to train multi-purpose robots, and designed the Grasping Neural Process for more intelligent robotic grasping.

IBM and Pasqal partnered to develop a common approach to quantum-centric supercomputing and to promote application research in chemistry and materials science.

Stanford University and Q-NEXT researchers investigated diamond to find the source of its temperamental nature when it comes to emitting quantum signals.

TU Wien researchers investigated how AI categorizes images.

In Canada:

• Simon Fraser University received funding of over $80 million from various sources to upgrade the supercomputing facility at the Cedar National Host Site.
• The Digital Research Alliance of Canada announced $10.28 million to renew the University of Victoria’s Arbutus cloud infrastructure.
• The Canadian government invested $18.4 million in quantum research at the University of Waterloo.

Events and Further Reading

Find upcoming chip industry events here, including:

Upcoming webinars are here.

Semiconductor Engineering’s latest newsletters:

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.

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.

Atomic layer deposition (ALD) used to be considered too slow to be of practical use in semiconductor manufacturing, but it has emerged as a critical tool for both transistor and interconnect fabrication at the most advanced nodes.

ALD can be speeded up somewhat, but the real shift is the rising value of precise composition and thickness control at the most advanced nodes, which makes the extra time spent on deposition worthwhile.

ALD is a close cousin of chemical vapor deposition, initially introduced in high volume to the semiconductor industry for hafnium oxide (high-k) gate dielectrics. Both CVD and ALD are inherently conformal processes. Deposition occurs on all surfaces exposed to a precursor gas. In ALD, though, the reaction is self-limiting.

The process works like this: First, a precursor gas (A) is introduced into the process chamber, where it adsorbs onto all available substrate sites. No further adsorption occurs once all surface sites are occupied. An inert purge gas, typically nitrogen or argon, flushes out any remaining precursor gas, then a second precursor (B) is introduced. Precursor B reacts with the chemisorbed precursor A to produce the desired film. Once all of the adsorbed molecules are consumed, the reaction stops. After a second purge step, the cycle repeats.

ALD opportunities expand as features shrink
The step-by-step nature of ALD is both its strength and its weakness. Depositing one monolayer at a time gives manufacturers extremely precise thickness control. Using different precursor gases in different ratios can tune the film composition. Unfortunately, the repeated precursor/purge gas cycles take a lot of time. In an interview, CEA-Leti researcher Rémy Gassilloud estimated that in a single wafer process, two minutes per wafer is the maximum cost-effective process time. But two minutes is only enough time to deposit about a 2nm-thick film.

Some process adjustments can improve throughput. Silicon dioxide ALD often uses large furnaces to process many wafers at once. Plasma activation can ionize reagents and accelerate film formation. Still, Gassilloud estimates that 10nm is the maximum practical thickness for ALD films.

As transistors shrink, though, the number of layers in that thickness range is increasing. Transistor structures also are becoming more complex, requiring deposition on vertical surfaces, into deep trenches, and other places not readily accessible by line-of-sight PVD methods. Replacement gates for gate-all-around transistors, for instance, need a process that can fill nanometer-scale cavities.

As noted above, HfO₂ was the first successful application of ALD in semiconductor manufacturing. Its precursors, HfCl₄ and water, are both chemically simple small molecules, whose by-products are volatile and easily removed. Such simple chemistries are the exception, though. ALD of silicon dioxide typically uses aminosilane precursors.⁠[1] Metal nitrides often have complex metal-organic precursor gases. Gassilloud noted that ligands might be added to a precursor molecule to change its vapor pressure or reactivity, or to facilitate adhesion to the substrate. In selective deposition processes, discussed below, ligands might improve selectivity between growth and non-growth surfaces. These larger molecules can be difficult to insinuate into smaller features, and byproducts can be difficult to remove. Complex byproducts can also become a contamination source.

One of the advantages of ALD is its very low process temperature, typically between 200°C and 300°C. It is thermally compatible with both transistor and interconnect processes in CMOS, as well as with deposition on plastic and other novel substrates. Even so, Aditya Kumar and colleagues at GlobalFoundries showed that precise temperature control is important.^⁠[2] TDMAT (tetrakis- dimethylamino titanium) condensation in a TiN deposition process was a significant source of particle defects. To maintain the desired process temperature, both the precursor and purge gas temperatures matter. Introducing cold purge gas into a warm process chamber can cause rapid condensation.

As ALD has become a mainstream process, the industry has found applications for it beyond core device materials, in a variety of sacrificial and spacer layers. For example, double- and quadruple-patterning schemes often use ALD for “pitch-doubling.” By depositing a spacer material on either side of a patterned “mandrel,” then removing the mandrel, the process can cut the original pitch in half without the need for an additional, more costly lithography step.^⁠[3]

Fig. 1: Self-aligned double patterning with ALD spacers. Source: Creative Commons

Depositing a doped oxide on the vertical silicon fins of a finFET device is a less directional and less damaging alternative to ion implantation.[^⁠4]

Selective deposition brings lateral control
These last two examples depend on surface characteristics to mediate deposition. A precursor might adhere more readily to a hard mask than to the underlying material. The vertical face of a silicon fin might offer more (or fewer) adsorption sites than the horizontal face. Selective deposition on more complicated structures may require a pre-deposited growth template, functionalizing substrate regions to encourage or discourage growth. Selective deposition is especially important in interconnect applications. In general, though, a comprehensive review by Rong Chen and colleagues at Huazhong University of Science and Technology explained that selective deposition methods need to replenish the template material as the film grows while needing a mechanism to selectively remove the unwanted material.⁠[5]

For example, tungsten preferentially deposits on silicon relative to SiO₂, but the selectivity diminishes after only a few cycles. Researchers at North Carolina State University successfully re-passivated the oxide by incorporating hydrogen into the tungsten precursor.[⁠6] Similarly, a group at Eindhoven University of Technology found that SiO₂ preferentially deposited on SiO₂ relative to other oxides for only 10 to 15 cycles. A so-called ABC-cycle — adding acetylacetone (“Inhibitor A”) as an inhibitor every 5 to 10 cycles — restored selectivity.⁠[7]

Alternatively, or in addition, atomic layer etching (ALE) might be used to remove unwanted material. ALE operates in the same step-by-step manner as ALD. The first half of a cycle reacts with the existing surface, weakening the bond to the underlying material. Then, a second step — typically ion bombardment — removes the weakened layer. For example, in ALE etching of silicon, chlorine gas reacts with the surface to form various SiCl_x compounds. The chlorination process weakens the inter-silicon bonds between the surface and the bulk, and the chlorinated layer is easily sputtered away. The layer-by-layer nature of ALE depends on preferential removal of the surface material relative to the bulk (SiCl_x vs. Si in this case). The “ALE window” is the combination of energy and temperature at which the surface layer is completely removed without damaging the underlying material.

Somewhat counter-intuitively, Keren Kanarik and colleagues at Lam Research found that higher ion energies actually expanded the ALE window for silicon etching. High ion energies with short exposure times delayed the onset of silicon sputtering relative to conventional RIE.[8]

Adding and subtracting, one atomic layer at a time
For a long time, the semiconductor industry has been looking for alternatives to process schemes that deposit material, pattern it, then etch most of it away. Wouldn’t it be simpler to only deposit the material we will ultimately need? Meanwhile, atomic layer deposition has been filling the spaces under nanosheets and inside cavities. Bulk deposition and etch tools are still with us, and will be for the foreseeable future. In more and more cases, though, those tools provide the frame while ALD and ALE processes fill in the details.

Correction: Corrected attribution of the work on ABC cycles and selective deposition of SiO₂.

References

1. Wenling Li, et al., “Impact of aminosilane and silanol precursor structure on atomic layer deposition process,”Applied Surface Science, Vol 621, 2023,156869, https://doi.org/10.1016/j.apsusc.2023.156869.
2. Kumar, et al., “ALD TiN Surface Defect Reduction for 12nm and Beyond Technologies,” 2020 31st Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC), Saratoga Springs, NY, USA, 2020, pp. 1-4, doi: 10.1109/ASMC49169.2020.9185271.
3. Shohei Yamauchi, et al., “Extendibility of self-aligned type multiple patterning for further scaling”, Proc. SPIE 8682, Advances in Resist Materials and Processing Technology XXX, 86821D (29 March 2013); https://doi.org/10.1117/12.2011953
4. Kalkofen, et al., “Atomic layer deposition of phosphorus oxide films as solid sources for doping of semiconductor structures,” 2018 IEEE 18th International Conference on Nanotechnology (IEEE-NANO), Cork, Ireland, 2018, pp. 1-4, doi: 10.1109/NANO.2018.8626235.
5. Rong Chen et al., “Atomic level deposition to extend Moore’s law and beyond,” 2020 Int. J. Extrem. Manuf. 2 022002 DOI 10.1088/2631-7990/ab83e0
6. B Kalanyan, et al., “Using hydrogen to expand the inherent substrate selectivity window during tungsten atomic layer deposition,” 2016 Chem. Mater. 28 117–26 https://doi.org/10.1021/acs.chemmater.5b03319
7. Alfredo Mameli et al., “Area-Selective Atomic Layer Deposition of SiO2 Using Acetylacetone as a Chemoselective Inhibitor in an ABC-Type Cycle” ACS Nano 2017, 11, 9, 9303–9311. https://doi.org/10.1021/acsnano.7b04701
8. Keren J. Kanarik, et al., “Universal scaling relationship for atomic layer etching,” J. Vac. Sci. Technol. A 39, 010401 (2021); doi: 10.1116/6.0000762

The post Enabling Advanced Devices With Atomic Layer Processes 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.

Atomic layer deposition (ALD) used to be considered too slow to be of practical use in semiconductor manufacturing, but it has emerged as a critical tool for both transistor and interconnect fabrication at the most advanced nodes.

ALD can be speeded up somewhat, but the real shift is the rising value of precise composition and thickness control at the most advanced nodes, which makes the extra time spent on deposition worthwhile.

ALD is a close cousin of chemical vapor deposition, initially introduced in high volume to the semiconductor industry for hafnium oxide (high-k) gate dielectrics. Both CVD and ALD are inherently conformal processes. Deposition occurs on all surfaces exposed to a precursor gas. In ALD, though, the reaction is self-limiting.

The process works like this: First, a precursor gas (A) is introduced into the process chamber, where it adsorbs onto all available substrate sites. No further adsorption occurs once all surface sites are occupied. An inert purge gas, typically nitrogen or argon, flushes out any remaining precursor gas, then a second precursor (B) is introduced. Precursor B reacts with the chemisorbed precursor A to produce the desired film. Once all of the adsorbed molecules are consumed, the reaction stops. After a second purge step, the cycle repeats.

ALD opportunities expand as features shrink
The step-by-step nature of ALD is both its strength and its weakness. Depositing one monolayer at a time gives manufacturers extremely precise thickness control. Using different precursor gases in different ratios can tune the film composition. Unfortunately, the repeated precursor/purge gas cycles take a lot of time. In an interview, CEA-Leti researcher Rémy Gassilloud estimated that in a single wafer process, two minutes per wafer is the maximum cost-effective process time. But two minutes is only enough time to deposit about a 2nm-thick film.

Some process adjustments can improve throughput. Silicon dioxide ALD often uses large furnaces to process many wafers at once. Plasma activation can ionize reagents and accelerate film formation. Still, Gassilloud estimates that 10nm is the maximum practical thickness for ALD films.

As transistors shrink, though, the number of layers in that thickness range is increasing. Transistor structures also are becoming more complex, requiring deposition on vertical surfaces, into deep trenches, and other places not readily accessible by line-of-sight PVD methods. Replacement gates for gate-all-around transistors, for instance, need a process that can fill nanometer-scale cavities.

As noted above, HfO₂ was the first successful application of ALD in semiconductor manufacturing. Its precursors, HfCl₄ and water, are both chemically simple small molecules, whose by-products are volatile and easily removed. Such simple chemistries are the exception, though. ALD of silicon dioxide typically uses aminosilane precursors.⁠[1] Metal nitrides often have complex metal-organic precursor gases. Gassilloud noted that ligands might be added to a precursor molecule to change its vapor pressure or reactivity, or to facilitate adhesion to the substrate. In selective deposition processes, discussed below, ligands might improve selectivity between growth and non-growth surfaces. These larger molecules can be difficult to insinuate into smaller features, and byproducts can be difficult to remove. Complex byproducts can also become a contamination source.

One of the advantages of ALD is its very low process temperature, typically between 200°C and 300°C. It is thermally compatible with both transistor and interconnect processes in CMOS, as well as with deposition on plastic and other novel substrates. Even so, Aditya Kumar and colleagues at GlobalFoundries showed that precise temperature control is important.^⁠[2] TDMAT (tetrakis- dimethylamino titanium) condensation in a TiN deposition process was a significant source of particle defects. To maintain the desired process temperature, both the precursor and purge gas temperatures matter. Introducing cold purge gas into a warm process chamber can cause rapid condensation.

As ALD has become a mainstream process, the industry has found applications for it beyond core device materials, in a variety of sacrificial and spacer layers. For example, double- and quadruple-patterning schemes often use ALD for “pitch-doubling.” By depositing a spacer material on either side of a patterned “mandrel,” then removing the mandrel, the process can cut the original pitch in half without the need for an additional, more costly lithography step.^⁠[3]

Fig. 1: Self-aligned double patterning with ALD spacers. Source: Creative Commons

Depositing a doped oxide on the vertical silicon fins of a finFET device is a less directional and less damaging alternative to ion implantation.[^⁠4]

Selective deposition brings lateral control
These last two examples depend on surface characteristics to mediate deposition. A precursor might adhere more readily to a hard mask than to the underlying material. The vertical face of a silicon fin might offer more (or fewer) adsorption sites than the horizontal face. Selective deposition on more complicated structures may require a pre-deposited growth template, functionalizing substrate regions to encourage or discourage growth. Selective deposition is especially important in interconnect applications. In general, though, a comprehensive review by Rong Chen and colleagues at Huazhong University of Science and Technology explained that selective deposition methods need to replenish the template material as the film grows while needing a mechanism to selectively remove the unwanted material.⁠[5]

For example, tungsten preferentially deposits on silicon relative to SiO₂, but the selectivity diminishes after only a few cycles. Researchers at North Carolina State University successfully re-passivated the oxide by incorporating hydrogen into the tungsten precursor.[⁠6] Similarly, a group at Argonne National Laboratory found that SiO₂ preferentially deposited on SiO₂ relative to other oxides for only 10 to 15 cycles. Adding acetylacetone (“Precursor C”) as an inhibitor every 5 to 10 cycles — restored selectivity.⁠[7]

Alternatively, or in addition, atomic layer etching (ALE) might be used to remove unwanted material. ALE operates in the same step-by-step manner as ALD. The first half of a cycle reacts with the existing surface, weakening the bond to the underlying material. Then, a second step — typically ion bombardment — removes the weakened layer. For example, in ALE etching of silicon, chlorine gas reacts with the surface to form various SiCl_x compounds. The chlorination process weakens the inter-silicon bonds between the surface and the bulk, and the chlorinated layer is easily sputtered away. The layer-by-layer nature of ALE depends on preferential removal of the surface material relative to the bulk (SiCl_x vs. Si in this case). The “ALE window” is the combination of energy and temperature at which the surface layer is completely removed without damaging the underlying material.

Somewhat counter-intuitively, Keren Kanarik and colleagues at Lam Research found that higher ion energies actually expanded the ALE window for silicon etching. High ion energies with short exposure times delayed the onset of silicon sputtering relative to conventional RIE.[8]

Adding and subtracting, one atomic layer at a time
For a long time, the semiconductor industry has been looking for alternatives to process schemes that deposit material, pattern it, then etch most of it away. Wouldn’t it be simpler to only deposit the material we will ultimately need? Meanwhile, atomic layer deposition has been filling the spaces under nanosheets and inside cavities. Bulk deposition and etch tools are still with us, and will be for the foreseeable future. In more and more cases, though, those tools provide the frame while ALD and ALE processes fill in the details.

References

1. Wenling Li, et al., “Impact of aminosilane and silanol precursor structure on atomic layer deposition process,”Applied Surface Science, Vol 621, 2023,156869, https://doi.org/10.1016/j.apsusc.2023.156869.
2. Kumar, et al., “ALD TiN Surface Defect Reduction for 12nm and Beyond Technologies,” 2020 31st Annual SEMI Advanced Semiconductor Manufacturing Conference (ASMC), Saratoga Springs, NY, USA, 2020, pp. 1-4, doi: 10.1109/ASMC49169.2020.9185271.
3. Shohei Yamauchi, et al., “Extendibility of self-aligned type multiple patterning for further scaling”, Proc. SPIE 8682, Advances in Resist Materials and Processing Technology XXX, 86821D (29 March 2013); https://doi.org/10.1117/12.2011953
4. Kalkofen, et al., “Atomic layer deposition of phosphorus oxide films as solid sources for doping of semiconductor structures,” 2018 IEEE 18th International Conference on Nanotechnology (IEEE-NANO), Cork, Ireland, 2018, pp. 1-4, doi: 10.1109/NANO.2018.8626235.
5. Rong Chen et al., “Atomic level deposition to extend Moore’s law and beyond,” 2020 Int. J. Extrem. Manuf. 2 022002 DOI 10.1088/2631-7990/ab83e0
6. B Kalanyan, et al., “Using hydrogen to expand the inherent substrate selectivity window during tungsten atomic layer deposition,” 2016 Chem. Mater. 28 117–26 https://doi.org/10.1021/acs.chemmater.5b03319
7. Yanguas-Gil A, Libera J A and Elam J W, “Modulation of the growth per cycle in atomic layer deposition using reversible surface functionalization,” 2013 Chem. Mater. 25 4849–60 https://doi.org/10.1021/cm4029098
8. Keren J. Kanarik, et al., “Universal scaling relationship for atomic layer etching,” J. Vac. Sci. Technol. A 39, 010401 (2021); doi: 10.1116/6.0000762

The post Enabling Advanced Devices With Atomic Layer Processes appeared first on Semiconductor Engineering.

The government of India has approved a major investment in semiconductor and electronics production that will include the country’s first state-of-the-art semiconductor fab. It announced that three plants—one semiconductor fab and two packaging and test facilities—will break ground within 100 days. The government has approved 1.26 trillion Indian rupees (US $15.2 billion) for the projects.

India’s is the latest in a string of efforts to boost domestic chip manufacturing in the hope of making nations and regions more independent in what’s seen as a strategically critical industry. “On one end India has a large and growing domestic demand and on the other end global customers are looking at India for supply-chain resilience,” Frank Hong, chairman of Taiwan-based foundry Powerchip Semiconductor (PSMC), a partner in the new fab, said in a press release. “There could not have been a better time for India to make its entry into the semiconductor manufacturing industry.”

The country’s first fab will be an $11 billion joint venture between PSMC and Tata Electronics, a branch of the $370 billion Indian conglomerate. Through the partnership, it will be capable of 28-, 40-, 55-, and 110-nanometer chip production, with a capacity of 50,000 wafers per month. Far from the cutting edge, these technology nodes nevertheless are used in the bulk of chipmaking, with 28 nm being the most advanced node using planar CMOS transistors instead of the more advanced FinFET devices.

“The announcement is clear progress toward creating a semiconductor manufacturing presence in India,” says Rakesh Kumar, a professor of electrical and computer engineering at University of Illinois Urbana-Champaign and author of Reluctant Technophiles: India’s Complicated Relationship with Technology. “The choice of 28-nm, 40-nm, 55-nm, 90-nm, and 110-nm also seems sensible, since it limits the cost to the government and the players, who are taking a clear risk.”

According to Tata, the fab will make chips for applications such as power management, display drivers, microcontrollers, as well as and high-performance computing logic. Both the fab’s technological capability and target applications point toward products that were at the heart of the pandemic-era chip shortage.

The fab is in a new industrial zone in Dholera, in Gujarat, Prime Minister Narendra Modhi’s home state. Tata projects it will directly or indirectly lead to more than 20,000 skilled jobs in the region.

Chip Packaging Push

In addition to the chip fab, the government approved investments in two assembly, test, and packaging facilities, a sector of the semiconductor industry currently concentrated in Southeast Asia.

Tata Electronics will build a $3.25 billion plant at Jagiroad, in the eastern state of Assam. The company says it will offer a range of packaging technologies: wire bond and flip-chip, as well as system-in-package. It plans to expand into advanced packaging tech “in the future.” Advanced packaging, such as 3D integration, has emerged as a critical technology as the traditional transistor scaling of Moore’s Law has slowed and become increasingly expensive. Tata plans to start production at Jagiroad in 2025, and it predicts the plant will add 27,000 direct and indirect jobs to the local economy.

A joint venture between Japanese microcontroller giant Renesas, Thai chip packaging company Stars Microelectronics, and India’s CG Power and Industrial Solutions will build a $900 million packaging plant in Sanand, Gujarat. The plant will offer wire-bond and flip-chip technologies. CG, which will own 92 percent of the venture, is a Mumbai-based appliances and industrial motors and electronics firm.

There’s already a chip-packaging plant in the works in Sanand from a previous agreement. U.S.-based memory and storage maker Micron agreed last June to build a packaging and test facility there. Micron plans to spend $825 million in two phases on the plant. Gujarat and the Indian federal government is set to cover a further $1.925 billion. Micron expects the first phase to be operational by the end of 2024.

Generous Incentives

After an initial overture failed to attract chip companies, the government upped its ante. According to Stephen Ezzell at the Washington, D.C.–based policy-research organization the Information Technology and Innovation Foundation (IT&IF), India’s semiconductor incentives are now among the most attractive in the world.

In a report issued two weeks before the India fab announcement, Ezzell explained that for an approved silicon fab worth at least $2.5 billion and making 40,000 wafer starts per month the federal government will reimburse 50 percent of the fab cost with a state partner expected to add 20 percent. For a chip fab making smaller-volume products, such as sensors, silicon photonics, or compound semiconductors, the same formula holds, except that the minimum investment is $13 million. For a test and packaging facility, it’s just $6.5 million.

India is a rapidly growing consumer of semiconductors. Its market was worth $22 billion in 2019 and is expected to nearly triple to $64 billion by 2026, according to Counterpoint Technology Market Research. The country’s minister of state for IT and electronics, Rajeev Chandrasekhar projects further growth to $110 billion by 2030. At that point, it would account for 10 percent of global consumption, according to the IT&IF report.

About 20 percent of the world’s semiconductor design engineers are in India, according to the IT&IF report. And between March 2019 and 2023 semiconductor job openings in the country increased 7 percent. The hope is that the investment will be a draw for new engineering students.

In an exclusive interview ahead of an invite-only event today in San Jose, Intel outlined new chip technologies it will offer its foundry customers by sharing a glimpse into its future data-center processors. The advances include more dense logic and a 16-fold increase in the connectivity within 3D-stacked chips, and they will be among the first top-end technologies the company has ever shared with chip architects from other companies.

The new technologies will arrive at the culmination of a years-long transformation for Intel. The processor maker is moving from being a company that produces only its own chips to becoming a foundry, making chips for others and considering its own product teams as just another customer. The San Jose event, IFS Direct Connect, is meant as a sort of coming-out party for the new business model.

Internally, Intel plans to use the combination of technologies in a server CPU code-named Clearwater Forest. The company considers the product, a system-on-a-chip with hundreds of billions of transistors, an example of what other customers of its foundry business will be able to achieve.

“Our objective is to get the compute to the best performance per watt we can achieve” from Clearwater Forest, said Eric Fetzer, director of data center technology and pathfinding at Intel. That means using the company’s most advanced fabrication technology available, Intel 18A.

3D stacking “improves the latency between compute and memory by shortening the hops, while at the same time enabling a larger cache” —Pushkar Ranade

“However, if we apply that technology throughout the entire system, you run into other potential problems,” he added. “Certain parts of the system don’t necessarily scale as well as others. Logic typically scales generation to generation very well with Moore’s Law.” But other features do not. SRAM, a CPU’s cache memory, has been lagging logic, for example. And the I/O circuits that connect a processor to the rest of a computer are even further behind.

Faced with these realities, as all makers of leading-edge processors are now, Intel broke Clearwater Forest’s system down into its core functions, chose the best-fit technology to build each, and stitched them back together using a suite of new technical tricks. The result is a CPU architecture capable of scaling to as many as 300 billion transistors.

In Clearwater Forest, billions of transistors are divided among three different types of silicon ICs, called dies or chiplets, interconnected and packaged together. The heart of the system is as many as 12 processor-core chiplets built using the Intel 18A process. These chiplets are 3D-stacked atop three “base dies” built using Intel 3, the process that makes compute cores for the Sierra Forest CPU, due out this year. Housed on the base die will be the CPU’s main cache memory, voltage regulators, and internal network. “The stacking improves the latency between compute and memory by shortening the hops, while at the same time enabling a larger cache,” says senior principal engineer Pushkar Ranade.

Finally, the CPU’s I/O system will be on two dies built using Intel 7, which in 2025 will be trailing the company’s most advanced process by a full four generations. In fact, the chiplets are basically the same as those going into the Sierra Forest and Granite Rapids CPUs, lessening the development expense.

Here’s a look at the new technologies involved and what they offer:

3D Hybrid Bonding

3D hybrid bonding links compute dies to base dies.Intel

Intel’s current chip-stacking interconnect technology, Foveros, links one die to another using a vastly scaled-down version of how dies have long been connected to their packages: tiny “microbumps” of solder that are briefly melted to join the chips. This lets today’s version of Foveros, which is used in the Meteor Lake CPU, make one connection roughly every 36 micrometers. Clearwater Forest will use new technology, Foveros Direct 3D, which departs from solder-based methods to bring a whopping 16-fold increase in the density of 3D connections.

Called “hybrid bonding,” it’s analogous to welding together the copper pads at the face of two chips. These pads are slightly recessed and surround by insulator. The insulator on one chip affixes to the other when they are pressed together. Then the stacked chips are heated, causing the copper to expand across the gap and bind together to form a permanent link. Competitor TSMC uses a version of hybrid bonding in certain AMD CPUs to connect extra cache memory to processor-core chiplets and, in AMD’s newest GPU, to link compute chiplets to the system’s base die.

“The hybrid bond interconnects enable a substantial increase in density” of connections, says Fetzer. “That density is very important for the server market, particularly because the density drives a very low picojoule-per-bit communication.” The energy involved in data crossing from one silicon die to another can easily consume a big chunk of a product’s power budget if the per-bit energy cost is too high. Foveros Direct 3D brings that cost down below 0.05 picojoules per bit, which puts it on the same scale as the energy needed to move bits around within a silicon die.

A lot of that energy savings comes from the data traversing less copper. Say you wanted to connect a 512-wire bus on one die to the same-size bus on another so the two dies can share a coherent set of information. On each chip, these buses might be as narrow as 10–20 wires per micrometer. To get that from one die to the other using today’s 36-micrometer-pitch microbump tech would mean scattering those signals across several hundred square micrometers of silicon on one side and then gathering them across the same area on the other. Charging up all that extra copper and solder “quickly becomes both a latency and a large power problem,” says Fetzer. Hybrid bonding, in contrast, could do the bus-to-bus connection in the same area that a few microbumps would occupy.

As great as those benefits might be, making the switch to hybrid bonding isn’t easy. To forge hybrid bonds requires linking an already-diced silicon die to one that’s still attached to its wafer. Aligning all the connections properly means the chip must be diced to much greater tolerances than is needed for microbump technologies. Repair and recovery, too, require different technologies. Even the predominant way connections fail is different, says Fetzer. With microbumps, you are more likely to get a short from one bit of solder connecting to a neighbor. But with hybrid bonding, the danger is defects that lead to open connections.

Backside power

One of the main distinctions the company is bringing to chipmaking this year with its Intel 20A process, the one that will precede Intel 18A, is backside power delivery. In processors today, all interconnects, whether they’re carrying power or data, are constructed on the “front side” of the chip, above the silicon substrate. Foveros and other 3D-chip-stacking tech require through-silicon vias, interconnects that drill down through the silicon to make connections from the other side. But back-side power delivery goes much further. It puts all of the power interconnects beneath the silicon, essentially sandwiching the layer containing the transistors between two sets of interconnects.

PowerVia puts the silicon’s power supply network below, leaving more room for data-carrying interconnects above.Intel

This arrangement makes a difference because power interconnects and data interconnects require different features. Power interconnects need to be wide to reduce resistance, while data interconnects should be narrow so they can be densely packed. Intel is set to be the first chipmaker to introduce back-side power delivery in a commercial chip, later this year with the release of the Arrow Lake CPU. Data released last summer by Intel showed that back-side power alone delivered a 6 percent performance boost.

The Intel 18A process technology’s back-side-power-delivery network technology will be fundamentally the same as what’s found in Intel 20A chips. However, it’s being used to greater advantage in Clearwater Forest. The upcoming CPU includes what’s called an “on-die voltage regulator” within the base die. Having the voltage regulation close to the logic it drives means the logic can run faster. The shorter distances let the regulator respond to changes in the demand for current more quickly, while consuming less power.

Because the logic dies use back-side power delivery, the resistance of the connection between the voltage regulator and the dies logic is that much lower. “The power via technology along with the Foveros stacking gives us a really efficient way to hook it up,” says Fetzer.

RibbonFET, the next generation

In addition to back-side power, the chipmaker is switching to a different transistor architecture with the Intel 20A process: RibbonFET. A form of nanosheet, or gate-all-around, transistor, RibbonFET replaces the FinFET, CMOS’s workhorse transistor since 2011. With Intel 18A, Clearwater Forest’s logic dies will be made with a second generation of RibbonFET process. While the devices themselves aren’t very different from the ones that will emerge from Intel 20A, there’s more flexibility to the design of the devices, says Fetzer.

RibbonFET is Intel’s take on nanowire transistors.Intel

“There’s a broader array of devices to support various foundry applications beyond just what was needed to enable a high-performance CPU,” which was what the Intel 20A process was designed for, he says.

RibbonFET’s nanowires can have different widths depending on the needs of a logic cell.Intel

Some of that variation stems from a degree of flexibility that was lost in the FinFET era. Before FinFETs arrived, transistors in the same process could be made in a range of widths, allowing a more-or-less continuous trade-off between performance—which came with higher current—and efficiency—which required better control over leakage current. Because the main part of a FinFET is a vertical silicon fin of a defined height and width, that trade-off now had to take the form of how many fins a device had. So, with two fins you could double current, but there was no way to increase it by 25 or 50 percent.

With nanosheet devices, the ability to vary transistor widths is back. “RibbonFET technology enables different sizes of ribbon within the same technology base,” says Fetzer. “When we go from Intel 20A to Intel 18A, we offer more flexibility in transistor sizing.”

That flexibility means that standard cells, basic logic blocks designers can use to build their systems, can contain transistors with different properties. And that enabled Intel to develop an “enhanced library” that includes standard cells that are smaller, better performing, or more efficient than those of the Intel 20A process.

2nd generation EMIB

In Clearwater Forest, the dies that handle input and output connect horizontally to the base dies—the ones with the cache memory and network—using the second generation of Intel’s EMIB. EMIB is a small piece of silicon containing a dense set of interconnects and microbumps designed to connect one die to another in the same plane. The silicon is embedded in the package itself to form a bridge between dies.

Dense 2D connections are formed by a small sliver of silicon called EMIB, which is embedded in the package substrate.Intel

The technology has been in commercial use in Intel CPUs since Sapphire Rapids was released in 2023. It’s meant as a less costly alternative to putting all the dies on a silicon interposer, a slice of silicon patterned with interconnects that is large enough for all of the system’s dies to sit on. Apart from the cost of the material, silicon interposers can be expensive to build, because they are usually several times larger than what standard silicon processes are designed to make.

The second generation of EMIB debuts this year with the Granite Rapids CPU, and it involves shrinking the pitch of microbump connections from 55 micrometers to 45 micrometers as well as boosting the density of the wires. The main challenge with such connections is that the package and the silicon expand at different rates when they heat up. This phenomenon could lead to warpage that breaks connections.

What’s more, in the case of Clearwater Forest “there were also some unique challenges, because we’re connecting EMIB on a regular die to EMIB on a Foveros Direct 3D base die and a stack,” says Fetzer. This situation, recently rechristened EMIB 3.5 technology (formerly called co-EMIB), requires special steps to ensure that the stresses and strains involved are compatible with the silicon in the Foveros stack, which is thinner than ordinary chips, he says.

For more, see Intel’s whitepaper on their foundry tech.