Investigation on Degradation of 1.2-kV Planar and Trench SiC MOSFETs Under Repetitive Pulse Current Stress of Body Diode

This study experimentally investigates the body diode reliability of the latest commercial 1.2-kV SiC MOSFETs with planar-gate, reinforced symmetric-trench, and asymmetric-trench structures for the first time. The proposed testing platform enables testing at high currents within reasonable thermal limits through a repetitive pulse current mode. Experimental results reveal a risk of bipolar degradation in large-area 1.2-kV commercial SiC MOSFETs. Degradation phenomena and mechanisms, including first-quadrant and third-quadrant characteristics degradation caused by basal plane dislocations (BPDs) originating from the substrate, as well as third-quadrant knee voltage (Von) and blocking voltage degradation resulting from BPDs originating from fabrication processes, are characterized and analyzed. Specifically, two degradation phases were identified: during the initial stress period, on-resistance (Rds), third-quadrant on-voltage drop (Vsd), and leakage current (Idss) exhibited significant increases. However, after a certain period, the degradation saturated, and Rds, Vsd, and Idss ceased to further deteriorate. Furthermore, technology computer-aided design (TCAD) simulations were employed to model the bipolar degradation behavior in reinforced symmetric-trench MOSFETs, with particular emphasis on analyzing and validating the impact of BPDs localization on device performance. In addition, the effects of case temperature, current density, and chip area on bipolar degradation are thoroughly examined. In large-area devices, BPDs induced by fabrication processes are more easily activated under high temperature and high current density, leading to degradation in Rds, Vsd, and Idss. In contrast, slight degradation in Rds, Vsd, and Idss in small-area devices is attributed to BPDs originating from the substrate.