How ST Strategizes SiC to Power the Future of EVs

Article By : Anne-Françoise Pelé

STMicro sees SiC technologies as the accelerator for the electrification of road transport.

The electrification of road transport is a necessary step for achieving carbon-neutrality objectives. As the demand for silicon carbide (SiC) wafers accelerates, STMicroelectronics (ST) has applied recent investments in its manufacturing facilities and expanded its partnership with Soitec on SiC substrate manufacturing technology.

Silicon carbide, a wide-bandgap semiconductor, has been a technology accelerator for electric vehicles (EVs), increasing the power density of EV electronics systems while reducing the vehicles’ overall weight, size and cost.

Edoardo Merli (Source: STMicroelectronics)

“Automotive and industrial customers around the world are adopting SiC to improve the performance of their systems as they shift to electric platforms,” said Edoardo Merli, Power Transistor sub-group general manager and executive vice president of STMicroelectronics. “The supply of SiC devices isn’t unlimited, however, and greater volumes will be required over the coming years to support global demand. Our cooperation with Soitec is mutually beneficial in terms of additional qualified capacity to support this strategic market.”

Navigating the road to electrification

In line with carbon-emission–reduction trajectories, EV adoption is surging. Demand for faster charging, greater efficiency and longer range is driving the development of 800-V battery systems as the new standard in the EV powertrain. Silicon carbide will play a key role in the transition from 400-V to 800-V EV systems.

Tesla kicked off the SiC power device market in 2018, when it became the first carmaker to use SiC MOSFETs in its Model 3. Supplied by ST, the device was integrated with an in-house–designed inverter. SiC is now the material of choice for EVs, and market research firm Yole Group predicts that the EV/hybrid-vehicle market will represent more than 70% of the SiC market, equating to $4.7 billion, in 2027.

The sustained demand for SiC wafers is such that IDMs like ST, Infineon and onsemi are adjusting their strategies to meet the requirements of automotive OEMs. And the adjustments are paying off. The French-Italian group generated about $700 million in SiC revenue in 2022, with a plan to be above $1 billion in 2023.

“We are now well over 100 projects involving more than 80 customers, with the majority of projects being automotive,” said Merli. “SiC power devices play a key role in our strategy and to achieve revenue targets over the coming years. Not only are our process and package technologies the focus of constant development and innovation, [but] we are injecting major capital into our supply chain and manufacturing capabilities to meet rising current and future demand.”

In 2023, ST plans to invest about $4 billion in capex. About 80% will be devoted to its 300-mm wafer fabs and SiC manufacturing capacity, including its SiC substrate initiative.

Building the manufacturing base

ST is transforming its manufacturing base to support future growth and improve profitability, with a strong focus on wide-bandgap semiconductors. On the SiC side, the chipmaker said it is on track for a tenfold increase in front-end capacity over 2017.

Last year, ST continued to ramp up its SiC front-end device production in Ang Mo Kio, Singapore, and announced a plan to build a $730 million integrated SiC epitaxial substrate manufacturing facility in Catania, Italy. Production is expected to start in 2023 and ramp up in 2024, said Merli.

“The new facility we are building at the ST Catania site in Italy is the first of its kind in Europe and will solidify our global SiC manufacturing presence, from front-end fabs in Catania and Ang Mo Kio to back-end fabs in Bouskoura, Morocco, and Shenzhen, China, to materials, product design, R&D and engineering in Catania and Norrköping, Sweden.”

With these investments, Merli said, ST is committed to ensuring production capacity for its global customer base across automotive and industrial sectors as they pursue electrification and digitization targets. “The new fabs represent a significant milestone on ST’s path toward ensuring we deliver on our promise of 40% internal substrate sourcing by 2024.”

ST is also committed to helping Europe implement the Chips Act through the establishment of key industries inside the EU, said Merli. “We believe ownership of the full SiC supply chain is key to mastering the technology and with our investments ensure ST builds a flexible and sustainable supply chain.”

Transitioning from 150 mm to 200 mm

The new SiC substrate manufacturing facility in Catania will produce in volume 150-mm SiC epitaxial substrates, integrating all steps in the production flow, and 200-mm wafers in the near future.

This follows the recent extension of the agreement between ST and Soitec to qualify Soitec’s SmartSiC technology for the production of 200-mm SiC substrates.

The first step of their collaboration is implementing the qualification plan over the next 18 months, which will include a technology license agreement. A SiC substrate supply agreement will be subject to the qualification phase of the technology by ST and Soitec, Merli said.

Soitec’s SmartSiC is an adaptation of Soitec’s proprietary Smart Cut process to SiC. Emerging from a pilot line at Soitec’s Substrate Innovation Center within CEA-Leti in Grenoble, France, SmartSiC is made of a very thin layer from a single-crystal SiC donor wafer, transferred and bonded onto a highly conductive carrier wafer made of polycrystalline SiC. Soitec claims SmartSiC substrates enable new levels of performance and energy efficiency compared with traditional bulk SiC through higher donor-wafer reusability, improved yields and lower die sizes.

After demonstrating the quality and performance of 150-mm SiC engineered substrates for high-voltage power devices, Soitec moved to the next step and released in May what it claims is the world’s first bonding of a 200-mm single-crystal SiC donor wafer onto a 200-mm polycrystalline SiC handle wafer.

Emmanuel Sabonnadière (Source: Soitec)

“The larger the surface, the better the bonding,” Emmanuel Sabonnadière, vice president of the SiC program at Soitec, told EE Times Europe. “Because the polySiC handle wafer that we bond the silicon carbide to is very low-resistivity, you have more current. You have good voltage handling and higher current ratings, which is the holy grail for a power component.”

With widespread EV adoption, the volume of high-quality SiC substrates is expected to increase. Soitec claims its SmartSiC technology enables the production of 10× more high-quality SiC substrates from one single-crystal SiC substrate.

The prime-quality SiC donor wafer can be reused multiple times, Sabonnadière said. “Since we reuse 10× the value of a monoSiC [donor] wafer, if it’s of very good quality, you will have 10 wafers of very good quality. This reusability effect will allow us to improve manufacturing yields and put more devices on a single wafer.”

Transitioning from 150-mm to 200-mm SiC wafers allows for a substantial increase in capacity, with almost twice the usable area for IC fabrication, allowing for 1.8× to 1.9× more working chips per wafer.

“Accelerating the transition to 200 mm is the main focus of our collaboration with ST,” said Sabonnadière. “We will continue to improve SiC substrate performance and bring SmartSiC technology to high-volume production at ST’s Catania fab and Soitec’s Bernin 4 fab.”

Merli said the medium-term vision of ST’s collaboration with Soitec’s fab in Bernin, France, is to ensure a second qualified source of 200-mm SmartSiC substrates. “While ST is investing heavily in its in-house SiC substrate manufacturing to ramp up device and module manufacturing operations for global automotive and industrial customers, the cooperation with Soitec promises further benefits, including superior manufacturing yields and additional support for the transition from 150-mm to 200-mm wafers.”

Making SiC a de facto technology

SiC is influencing the entire EV industry, and Soitec wants to install SmartSiC as a market standard for SiC wafers at 150 mm and 200 mm.

“To make it a market standard, we have to work with the leaders to get the leaders to adopt it,” Sabonnadière said. “We’ve been fortunate to develop greatly in RF, where our technology has become a global standard,” he added, but in the EV sector, SmartSiC  “won’t necessarily be the whole market, because [the sector] is extremely burgeoning and several technologies will develop in parallel. We’ll be in the part of the market that is focused on high performance and high reliability.”

Soitec’s strategy is to establish collaborations beyond its direct customers and throughout the automotive supply chain, including design houses, Tier 1s and car OEMs. Sabonnadière believes that Soitec could “reasonably” take 30% of the SiC substrate market in the years to come.

In mid-2022, Paul Boudre, then-CEO of Soitec, said, “There is no smartphone without Soitec technology. There is no 4G or 5G without Soitec technology. We’re going to do exactly the same thing in the automotive industry. In 2030, there will be no electric car without Soitec technology.”

Will ST be part of that equation? Absolutely, Merli answered. “In fact, our ambition is to be an outsized portion of that equation.”

According to S&P Global Mobility, the average value of semiconductors per car is forecast to rise from $700 in 2020 to $1,138 by 2028. Full electrification is expected to add about $1,000 in the value of semiconductors to each vehicle and might require up to 5× as many chips.

Merli said ST is well-positioned to meet this rapid acceleration in chip demand. “ST pioneered the first automotive-grade SiC MOSFETs in 2016, and today, we lead the market with an estimated market share above 50% and more than 5 million passenger cars on the road using ST SiC devices.”

 

This article was originally published on EE Times.

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