A decrease in TDDB Lifetime of Commercial SiC power MOSFETs Under Repetitive Unclamped Inductive Switching Stresses

The degradation behavior under repetitive unclamped inductive switching stresses on the subsequent time-dependent dielectric breakdown (TDDB) of commercial SiC power MOSFETs are investigated. It is reported that repeated avalanche stresses can cause changes, including Vth (the threshold voltage) and Ron (on-state resistance) but not Igss (gate leakage current). However, the results show a significant decrease in the TDDB lifetime after 180k avalanche cycles, which suggests the degradation of the gate oxide. We attribute these results to defects at the SiC/SiO2 interface, which are caused by hot hole injection and trapping into the gate oxide above the channel and JFET region. The subthreshold curve analysis reveals that the density of the interface states changes during aging experiments, which further confirms our view. Meanwhile, interface states should be responsible for the increase in Ron, which was different from the previously research.