Analysis of new silicon carbide substrates to improve power devices

You may have heard of SiC, but do you know its role in automobiles? Growing demand for the technology in electric vehicles, telecommunications and industrial applications has prompted Soitec and Applied Materials to jointly formulate the next generation of silicon carbide for power devices (SiC) substrate joint development plan. The program aims to provide technologies and products to improve the performance and usability of SiC devices for next-generation electric vehicles.

“We look forward to working closely with Soitec to create materials engineering innovations for silicon carbide technology,” said Steve Ghanayem, senior vice president of new markets and alliances at Applied Materials.

OEMs designing with power devices certainly want the most efficient products they can get, and efficiency gains may be achieved when III-V semiconductors, including SiC, are used instead of silicon. SiC can significantly reduce power losses and increase power density, voltage, temperature and frequency while reducing heat dissipation. SiC also has about 3 times the forbidden bandwidth, and at the same breakdown voltage, the distance of the drift region can be reduced to one-tenth.

"High-voltage SiC devices perfectly combine fast switching and low losses, giving application users unprecedented flexibility in choosing topologies for medium-voltage and high-voltage power conversion." Olivier Beau, General Manager of Soitec's Composite Business Unit Olivier Bonnin said.

But there are a few factors hindering a rapid transition to silicon carbide substrates.

"Higher quality SiC materials are needed to increase yield (lower defect density) and reliability. Improved wafer flatness is needed to accommodate processes in high-volume casting and reduce process costs." The future of electric vehicles will be based on materials derived from semiconductor materials and Technological innovation starts at the substrate level. Demand for SiC-based semiconductor materials has been growing over the past year.

Bonnin cited statistics from Yole Developpement that the SiC power device market will grow from US$560 million today to US$2 billion in 2024, a compound annual growth rate of 28%. “Silicon carbide will likely become the material of choice over the next decade,” Bonin said. Applied Materials’ technology development program aims to create SiC engineered substrates in the second half of 2020 based on Soitec’s proprietary Smart Cut technology. sample. Smart Cut technology is currently used to manufacture silicon-on-insulator (SOI) products, which have been widely adopted by chip manufacturers.

“Soitec’s technology is designed to solve these challenges by transferring the highest quality SiC material over a specific receiver layer and recycling the SiC material multiple times,” said Bonnin.

“Smart Cut is our wafer bonding and layering technology. Essentially, it’s a way to turn a single high-quality SiC wafer into multiple high-quality SiC wafers. It does this by starting from a high-quality donor substrate This is accomplished by removing very thin layers of crystalline material and bonding them to lower cost/quality wafers. This results in multiple wafers with high quality surfaces on which semiconductor devices can be built. We believe that our Smart Cut technology for SiC can significantly improve quality, performance and cost at both the substrate and device levels (Figure 1)," said Olivier.

Switching losses and conduction losses per chip will be significantly reduced, but at high power densities chip area will be further reduced, and power density will have to cope with effective thermal management. SiC power diodes were among the first wide bandgap (WBG) devices to enter the market and have widely penetrated into specific areas, including PV converters and motor drives. These devices instantly increase efficiency, increase voltage and improve thermal performance. The inherent properties of this material bring the following benefits: SiC has a room temperature thermal conductivity of over 300W/mK.

“Our technology will take advantage of the properties of SiC materials and push their advantages to new device challenges with the help of some specific layer engineering techniques,” Bonnin said. Temperature coefficient and switching frequency are fundamental elements in electric vehicle design. Its stability at high temperatures and operability at higher switching frequencies allow for system size and weight reduction compared to partner Si, as components replace bulky magnetic components with lower form factors .

Electrical challenges will address current leakage issues in switching mode, which can lead to overvoltage and significant oscillation. These problems can be avoided due to the circuit layout used to control the current flow near the power module. Another problem has to do with capacitive coupling between AC and ground: this coupling becomes critical when large amounts of electromagnetic interference are generated. Again, in this case, smart design of the power module can help reduce this effect.

Cost is obviously a factor to consider: the biggest challenge is the widespread adoption of SiC devices. The electrical characteristics illustrate how they can significantly reduce system costs, but most importantly truly increase overall efficiency. SiC devices will transform applications through new packaging technologies. The above is the relevant analysis of SiC devices, I hope it can help you.