Short-circuit failure modes and mechanism investigation of 1200 V planar SiC MOSFETs

Abstract This paper presents a comprehensive analysis of the short-circuit failure mechanisms in commercial 1.2 kV planar silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) under 400 and 800 V bus voltage conditions. The study compares two products with varying short-circuit tolerances, scrutinizing their external characteristics and intrinsic factors that influence their short-circuit endurance. Experimental and numerical analyses reveal that at 400 V, the differential thermal expansion between the source metal and the dielectric leads to cracking, which in turn facilitates the infiltration of liquid metal and results in a gate–source short circuit. At 800 V, the failure mechanism is markedly different, attributed to the thermal carrier effect leading to the degradation of the gate oxide, which impedes the device's capacity to switch off, thereby triggering thermal runaway. The paper proposes strategies to augment the short-circuit robustness of SiC MOSFETs at both voltage levels, with the objective of fortifying the device's resistance to such failures.