The power-handling limitations of traditional silicon are expected to pave the way for alternative power technologies such as silicon carbide in applications such as electric vehicles. The current status of silicon carbide was discussed by Victor Veliadis, Chief Technical Officer at Power America and Professor of Electrical and Computer Engineering at North Carolina State University, during the recent virtual PowerUP Conference.

According to Veliadis, much of the SiC demand would be fueled by the conversion of vehicle electrical systems from 400 to 800 V, which would call for wide bandgap semiconductors able to handle higher amounts of power. Silicon carbide offers a wide bandgap and critical electric field that allows for higher voltage devices with thinner layers. This in turn  reduces resistance and associated conduction losses, results in low leakage, and allows high-temperature operation. Thinner layers and lower specific on-resistances allow for smaller form factors that reduce capacitance and thus allow the use of smaller passive components.

Veliadis said that electric vehicles would present a golden opportunity for SiC and other wide bandgap semiconductors. Dc-to-dc converters, for instance, can utilize the high-voltage handling capabilities of SiC to convert the higher voltage dc power from the traction battery pack to the lower voltage dc power needed to run vehicle accessories and recharge the auxiliary battery. Other applications include the onboard charger, traction battery pack, and auxiliary battery.  

Related:Silicon Carbide Power Inverter Technology Is Ready for Prime Time

A Yole Development report projects the power SiC semiconductor market to grow from $1.09 billion in 2021 to $6.27 billon by 2027, for a compound annual growth rate of 34%. Automotive applications will account are by far the largest segment.

Veliadias said in his presentation that SiC devices would be the optimal choice at voltages of 650 V and above, including 900 V, 1.2 kV, and beyond.

As with other emerging technologies, cost is one key challenge with SiC devices. Veliadis noted that the SiC wafer presently accounts for 50 to 70% of the cost of SiC devices, with domestic wafer production presently concentrated among only a few manufacturers, including Cree. The trend toward 200mm wafers could potentially reduce substrate costs by 20%.

Veliadis also noted that SiC substrate production processes need to be refined and optimized. For instance,  SiC is inert against chemical solvent and only dry etching is practical. Factors such as masking materials, mask etch selectivity, gas mixtures, etch rates, all need to be optimized. Other process considerations, according to Veliadis, include substrate thinning, doping, metallization, gate oxides, and the relative lack of flatness in SiC wafers.

Related:Bosch Brings Silicon Carbide to EV Mainstream

Producing SiC semiconductors also requires some up-front modification to production equipment, Veliadis noted. This would include a high-temperature anneal furnace, high-temperature implanter, a SiC backgrind tool, a backside metal deposition tool, and SiC substrate and epitaxy wafer surface defect inspection and metrology equipment.

Spencer Chin is a Senior Editor for Design News covering the electronics beat. He has many years of experience covering developments in components, semiconductors, subsystems, power, and other facets of electronics from both a business/supply-chain and technology perspective. He can be reached at [email protected].