On June 18th, Belgium’s microelectronics research center IMEC showcased the first CMOS CFET device featuring stacked bottom and top source/drain contacts at the 2024 IEEE VLSI Technology and Circuits Symposium (2024 VLSI). Although the results were achieved using front-side lithography techniques for both contacts, imec also demonstrated the feasibility of transferring the bottom contacts to the back side of the wafer, which potentially increases the survival rate of top devices from 11% to 79%.

IMEC explained that their logic technology roadmap envisions the introduction of Complementary Field-Effect Transistor (CFET) technology into device architectures at the A7 node. Paired with advanced wiring technologies, CFET is expected to reduce the standard cell height from 5T to 4T or even lower without sacrificing performance. Among the different approaches to integrating vertically stacked nMOS and pMOS structures, monolithic integration is considered the least disruptive compared to existing nanosheet process flows.

At VLSI Symposium 2024, IMEC demonstrated for the first time a functional monolithic CMOS CFET device with both top and bottom contacts. The device features a gate length of 18nm, a gate pitch of 60nm, and a vertical distance of 50nm between the n-type and p-type. The process flow IMEC’s proposed includes two CFET-specific modules: Middle Dielectric Isolation (MDI) and stacked bottom and top contacts.

MDI is a module pioneered by IMEC to isolate the top and bottom gates and to differentiate threshold voltage settings between n-type and p-type devices. Based on modifications to the “active” multilayer Si/SiGe stack in CFET, MDI module allows for the co-integration of internal spacers—a feature unique to nanosheets that isolates the gate from the source/drain.

“We obtained the best results in terms of process control with an MDI-first approach, i.e., before source/drain recess – the step where nanosheets and MDI are ‘cleaved’ to gain access to the channel sidewalls and start source/drain epi. An innovative source/drain recess etch with ‘in-situ capping’ enables MDI-first by protecting the gate hardmask/gate spacer during the source/drain recess.” stated Naoto Horiguchi, IMEC’s CMOS device technology director, as per a report from IMEC.

The second critical module is the formation of stacked source/drain bottom and top contacts, vertically separated by dielectric isolation. Key steps involve bottom contact metal filling and etching, followed by dielectric filling and etching—all completed within the confined space of the MDI stack.

Naoto Horiguchi noted that developing bottom contacts from the front side encountered many challenges, which potentially impacts bottom contact resistance and limits the process window for top devices. At VLSI 2024, IMEC indicated that despite additional processes like wafer bonding and thinning, this design is proved feasible, making the backside bottom contact structure an attractive option for the industry. Currently, research is underway to determine the optimal contact wiring method.

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• [News] TSMC’s Latest Advancements in CFET, 3D Stacking, and Silicon Photonics

(Photo credit: IMEC)

SK keyfoundry, a subsidiary of memory giant SK hynix, has achieved notable progress in the development of Gallium Nitride (GaN) power semiconductors. According to the latest report by Business Korea, the foundry would begin producing power semiconductors for Tesla in the second half of 2024.

According to the report, SK keyfoundry announced in early June that it has achieved the primary device characteristics of a 650V GaN High Electron Mobility Transistor (HEMT), which surpasses traditional silicon-based semiconductors in both efficiency and durability. This advancement aligns with SK keyfoundry’s plan to finalize the development of GaN power semiconductors by the end of this year.

It is worth noting that TSMC has also entered the GaN market a few years ago, as it provides GaN process for manufacturing 100/650V discrete GaN power devices for customers. For instance, in 2020, the world’s largest foundry has announced to collaborate with STMicroelectronics. According to its press release, ST’s GaN products will be manufactured using TSMC’s leading GaN process technology, including applications relating to automotive converters and chargers for hybrid and electric vehicles.

Regarding the development of SK keyfoundry, Business Korea noted that the company established an official team in 2022 to focus on the development of GaN technologies. Citing industry sources on June 20^th, the report stated that SK keyfoundry will reportedly begin producing power semiconductors for Tesla in the second half of this year.

Moreover, it also mulls to broaden its business scope, entering markets like fast-charging adapters, data centers, and energy storage systems afterwards. Starting in November, the company plans to manufacture power management chips (PMIC) at its 8-inch wafer fab in Cheongju.

Though foundries have not significantly contributed to SK hynix’s revenue so far, the development of power semiconductors could boost overall foundry sales. According to the report, SK keyfoundry also provides contract manufacturing for non-memory semiconductors such as Display Driver ICs (DDI) and Microcontroller Units (MCU), further diversifying its product lineup.

In the current landscape of the new energy market, third-generation semiconductors such as SiC and GaN have gained significant traction. SiC (Silicon Carbide) and GaN could offer significant benefits over traditional silicon.

To elaborate, semiconductor materials have the so-called “bandgap,” an energy range in a solid where no electrons can exist. According to German chipmaker Infineon, GaN has a bandgap of 3.4 eV, compared to silicon’s 1.12 eV bandgap. The wider bandgap of GaN allows it to sustain higher voltages and temperatures than silicon. While SiC dominates the high-power domain, GaN excels at lower power levels, offering lower conduction losses.

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• [News] Infineon in GaN and SiC Expansion Drive Advancements in the New Energy Market

(Photo credit: SK keyfoundry)

According to a report from CNA, Taiwanese semiconductor testing and packaging giant ASE announced on June 21st that it will collaborate with Hung Ching Development & Construction Corporation to jointly build the K28 plant in Kaohsiung. Scheduled for completion in Q4 2026, the facility will reportedly focus on advanced packaging and final testing in order to meet the high-performance computing and cooling demands of AI chips.

ASE’s CFO Joseph Tung stated that ASE Semiconductor is planning for operational growth at its Kaohsiung facilities. To meet the demand for advanced packaging processes, high-performance computing for AI chips and cooling, the company is developing land in Dashe, Kaohsiung in two phases. The first phase, K27 plant, was completed and moved-in in 2023, while the K28 plant, the second phase, aims to be completed by Q4 2026.

As reported by CNA citing sources, ASE Kaohsiung Plant contributes approximately 20% to ASE Technology Holding Co., Ltd.’s total revenue. The plant specializes in providing services such as packaging, wafer bumping, probe testing, materials, and final testing. It has also developed several smart factories focusing on advanced processes, including Fan-out packaging, System-in-Package (SiP), wafer bumping, and Flip Chip packaging.

These technologies are primarily used in automotive, medical, IoT, high-speed computing, artificial intelligence, and application processor fields.

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• [News] Following TSMC, ASE Reportedly Plans to Establish Plant in Kumamoto
• [News] ASE Expands Production at Kaohsiung Plant, Focusing on Advanced Packaging for AI Chips

Though being capable of running AI features may be the primary focus for global smartphones this year, due to restrictions on AI products’ usage in China, the Wall Street Journal reports that the upcoming new iPhone, expected at the end of the year, will not be able to use ChatGPT in China. Apple has reportedly been in discussions with companies like Baidu for potential partnerships, but no progress has been made yet.

China is Apple’s largest market for iPhones outside the United States. While smartphones from various brands will integrate AI this year at full throttle, incorporating apps like OpenAI’s ChatGPT, these apps from Western countries are not permitted for use in the Chinese market. According to the Wall Street Journal, industry insiders indicate that Apple is still searching for a Chinese AI partner. However, with the new iPhone set to launch in a few months, no progress has been made.

Notably, as per a report from TrendForce, in the first quarter, Apple faced a decline in sales in the Chinese market, resulting in a  drop in annual production to 47.9 million units.

In China, companies must obtain government approval to release AI devices. As of March this year, the Office of the Central Cyberspace Affairs Commission has approved 117 generative AI products, none of which are from brands outside of China.

The Wall Street Journal, citing industry sources, reported that Apple had tentatively inquired with Chinese authorities earlier this year about the possibility of allowing foreign language AI models on their smartphones. While believing approval to be unlikely, Apple has reportedly sought partnerships with local companies instead.

One of Apple’s main competitors, Samsung, has already launched the Galaxy S24 this year, featuring real-time translation and AI-enhanced photo editing and search capabilities. Samsung’s phone includes its own generative AI and also collaborates with Google. However, since Google’s AI tool Gemini is not permitted for use in China, Samsung has shifted to partnering with Baidu and Meitu AI.

It is not new for global tech companies to adjust their product and service offerings to cater to the Chinese market. For example, Apple uses state-owned enterprise servers for iCloud in China, and the recently launched Vision Pro cannot stream Apple TV+ in the country.

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• Q1 Smartphone Production Increases Due to Low Base Last Year, Expected to Decline 5–10% in Q2, Says TrendForce
• [News] Continued Slump in iPhone Demand in China – February Shipments Reportedly Plunge by 33%

(Photo credit: Apple)

Novatek, a major driver IC manufacturer in Taiwan, entered the iPhone 16 supply chain early this year and secured certification ahead of its competitor LX Semi. However, according to a report from Commercial Times citing sources, its Korean competitor, LX Semi, recently also obtained certification and, with strong support from foundries, is challenging Novatek’s exclusive supply position.

The same report continues to cite sources indicating that LX Semi remains the exclusive supplier for iPhone 16 Pro/Pro Max’s LG Display (LGD) OLED screens in the second half of the year, with significant acceleration in chip production starting in September. It is estimated that the order allocation between Novatek and LX Semi will be 55:45.

Industry sources cited by Commercial Times reveal that LX Semi has a closer partnership with leading foundries, compared to Novatek’s previous strategy of relying on established foundries. Reportedly, another sources confirms as well that LX Semi has recently been certified and, with support from foundries, will begin significant wafer production by the end of the third quarter.

Other industry sources cited by the report further pointed out that Apple’s OLED panels are supplied by Korean manufacturer LGD, while LX Semi was originally LG Group’s subsidiary. Therefore, after LX Semi obtained certification, they increased orders from LGD, thereby reducing the originally planned procurement of OLED driver ICs from Novatek. However, for Novatek, they still heavily rely on Apple orders. If shipments go smoothly, they are expected to further secure opportunities in other product lines, such as iPad OLED DDIs and Apple Watch.

Yet, concerns are also noted, as the report brought up that the momentum in TV applications accompanying sports events is expected to slow down. Additionally, subdued sales during China’s 618 shopping festival and a conservative attitude among brand manufacturers in the second half of the year may affect demand for components like DDICs.

Therefore, Novatek keeps investing in establishing OLED production lines in order to seek new breakthroughs, such as IT TCON (timing controller) products. These products are manufactured using a 12-nanometer advanced process to create efficient computing units, integrating UHD 240Hz LCD and OLED panel display compensation functions, targeting high-end laptops.

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• [News] Taiwanese IC Design Company Novatek Reportedly Secured a Spot in iPhone 16 via Collaboration with LGD
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(Photo credit: Novatek)