Investigation of the Short-circuit Failure Mechanisms in 1.2-kV SiC Trench MOSFETs with Thin N+ Substrates Using Electro-thermal-mechanical Analysis

This work investigated the effect of thin substrates on the short-circuit failure mechanisms in 1.2-kV SiC trench MOSFETs, using electro-thermal-mechanical analysis. With a high DC voltage, the SiC trench MOSFETs suffered destructive failure caused by a typical thermal runaway regardless of the thickness of the n+ substrates; however, with a medium DC voltage, SiC trench MOSFETs with thin n+ substrates of 100 μm failed not because of thermal runaway but because of thermal-mechanical stress at the gate interlayer. This stress was due to a volume mismatch caused by the different thermal expansion rates of the materials that composed the SiC MOSFETs.