A New Era for SiC Power Devices: Enhanced Performance Without Reliability Trade-offs

Silicon Carbide (SiC) Metal-Oxide-Semiconductor (MOS) devices are vital for achieving higher power efficiency in electric vehicles (EVs), high-speed rail, and advanced industrial systems. However, a major hurdle has been the high density of defects at the SiC/SiO2 interface, which limits electron mobility and, crucially, affects long-term device reliability.

Conventionally, improving SiC MOS performance involved introducing impurities like nitrogen (interface nitridation). While this boosted mobility, it often led to a subsequent degradation in overall device reliability, particularly under prolonged voltage stress—a significant concern for safety-critical applications.

A research group at Osaka University has successfully addressed this fundamental conflict. They have developed a novel two-stage thermal treatment technique utilizing diluted hydrogen annealing at ultra-high temperatures (exceeding 1200 degrees Celsius).

The innovation centers on performing the high-temperature hydrogen annealing twice: once before and once after the gate oxide deposition. This unique process effectively passivates or removes defects at the SiC near the surface and at the SiC/SiO2 interface, similar to a standard process used in silicon MOS technology, but adapted for the challenges of SiC.

Crucially, by not relying on the introduction of heterogeneous impurities like nitrogen, the new technique has been shown to dramatically improve both performance and reliability. Devices fabricated with this method exhibit electron mobility more than five times higher than standard unpurified devices, and demonstrate significantly superior immunity against both positive and negative bias stress compared to conventional nitrogen-doped SiC MOS devices.

This breakthrough paves the way for the next generation of SiC power modules that are not only more efficient and compact but also offer an unprecedented level of long-term reliability. The technology is expected to greatly accelerate the adoption of SiC across high-power applications, contributing significantly to a carbon-neutral society.