A Deep Insight Into the Degradation of 1.2-kV 4H-SiC mosfets Under Repetitive Unclamped Inductive Switching Stresses

In this paper, the long-term reliability of commercial 1.2-kV 4H-SiC MOFSETs under repetitive unclamped inductive switching stresses is evaluated experimentally. The degradation of device characteristics, including the threshold voltage Vth, drain leakage current Idss, and on-state resistance Ron, is observed after 80k avalanche cycles. The regular charge pumping (CP) measurements reveal that the failure mechanism characterized by the hot holes injection and trapping into the gate oxide above the channel and JFET region may occur during the aging experiments, which is further ascertained by the succeeding electrothermal simulations and should be responsible for the degradation of Vthand Idss. After decapping the failed devices, the bond wires lift off due to thermal fatigue is discovered and regarded as the main reason for the degradation of Ron. The poststress high-temperature treatment is also carried out as an approach to indirectly corroborate the aforementioned failure mechanisms. Moreover, the impact of different test conditions on the degradation rate of electrical characteristics is discussed to thereby find ways to relieve these degeneration phenomena.