French semiconductor pioneer Soitec on the growing opportunity of silicon-on-insulator technology

Misha Lu, DIGITIMES Asia, Taipei 0

Credit: Soitec

SOITEC, a leading manufacturer of engineered substrates such as silicon-on-insulator (SOI) based in France, has been turning its gaze towards Asia. Talking to DIGITIMES Asia, Thomas Piliszczuk, SOITEC's executive vice president of global business, explained the fundamentals of the SOI technology and where Soitec stands in the industry.

"The base of SOI as well as most of our engineered substrates is a technology called 'Smart Cut'TM, and SOITEC has a very large IP portfolio of this technology," said Piliszczuk. Fundamentally, this technology allows one to cut very thin layers of any material via ion implantation and transfer it onto another material.

Silicon-on-insulator: from a closed system to an open one

First invented around thirty years ago before the invention of FinFET, SOI was first commercialized by IBM and rapidly gained traction with many companies adopting the technology. "There were two values of SOI at the time," according to the Soitec VP, pointing to the reduced power consumption as a result of improved leakage as well as the improved computing power. However, though SOI enjoyed wide success, IBM's ecosystem was a closed one, making it difficult for other companies to join the landscape. "Soitec was at the time fully dependent on IBM's strategy," explained Piliszczuk. This first wave of success seen by SOI technology drew to a close with the emergence of FinFET, especially when companies like TSMC and Intel could build it differently as a result of an open ecosystem.

"This happened around 2000, and we were scrapping our head regarding what to do with SOI," explained Piliszczuk. After looking into different applications, Soitec saw an opportunity in mobile communications, at that time the beginning of 3G communication, as the key components were based on gallium arsenide (GaAs) with inherent limitations. To address this gap, Soitec came up with a new generation of SOI - named RF SOI. "RF SOI immediately brought huge value in terms of RF performance, chip integration, power consumption and overall cost," remarked Piliszczuk, and to avert the course taken by IBM, Soitec brought the technology to open market, talking to multiple foundries, paving the way to the standardization of SOI in the communications industry.

Increasing opportunity for FD-SOI in edge computing

"This is probably the most amazing success story of Soitec," said Piliszczuk, noting that RF-SOI can be found in the front-end modules within all the smartphones, and that now all foundries have RF-SOI offerings, including major players like TSMC and UMC. Today the success of the technology is testified by the number of RF SOI-based antenna switches and tuners in all 4G and 5G phones including all biggest brands.

As Piliszczuk noted, there were 2mm square of Soitec products in iPhone 4. Fast forward to today, in iPhone 14 Pro, there are around 72-millimeter square (Editor's note: Soitec's own estimate) of RF SOI. Though FinFET outperformed fully-depleted SOI, the Soitec VP believes that SOI has an edge against FinFET in applications where one has to strive for a balance between high computing power and low power consumption, such as edge devices in "sleep modes" that only wake up when receiving certain signals. In this sense, Piliszczuk considers SOI technology, the product called FD-SOI to be complementary to FinFET, instead of competition. "We knew it more than ten years ago, but back then nobody was thinking about edge computing," remarked Piliszczuk, "but today it became a real solution."

As RF-SOI becomes a standard in smartphone front-end modules and major foundries around the world are offering the solution, these foundries have all become Soitec's customers, including those in China. Piliszczuk observed that China is catching up in developing the processes around RF SOI, and it has become quite competitive in the market with foundries like SMIC offering RF SOI solutions.

"Today Soitec is serving them as any other foundry, and there's no barrier," indicated Piliszczuk, though the vice president emphasizes that Soitec abides by all the relevant restrictions. Despite that the Chinese market is significantly smaller than that of Taiwan and the US, Piliszczuk still finds it important: Soitec currently has a manufacturing partner in China - Shanghai Simgui Technology - which has the license to manufacture for Soitec products at 200mmdiameter. .

Stepping into GaN and SiC markets

With the rise of compound semiconductors like gallium nitride (GaN) and silicon carbide (SiC), Piliszczuk indicated that Soitec has also stepped into the sector, especially after acquiring a Euope-based company with GaN expertise four years ago. Soitec sees GaN applications in both RF and power markets, with both complimentary to Soitec's RF-SOI offerings.

Nevertheless, the vice president stressed that Soitec's priority lies in GaN's application in the RF market, citing cooperation with undisclosed Asia-based foundry and fabless customers in this sector. Though GaN's application in power market is not Soitec's current priority, the vice president expects more interest in the area as the sector matures with growing EV prevalence. As of now, Soitec places more importance on the RF applications of GaN on silicon (GaN on Si).

However, when it comes to the application of silicon carbide (SiC) in the power market, Piliszczuk sees future opportunities in introducing disruptive solutions. "We're not growing crystals of silicon carbide," he said, "What we do is to apply our Smart Cut ™ technology to take a very thin layer of SiC crystal, and bond it on different substrates called polysilicon carbide." In doing so, according to Piliszczuk, electrical performance and the quality of the substrates are improved, and one can enable the mass production of 200mm SiC wafers.

Credit: SOITEC