Investigation of Termination Soft Breakdown Mechanisms in 1700V-SiC MOSFETs Under HTRB with Different Temperatures

High temperature reverse bias (HTRB) testing is widely used to assess the reliability of commercial SiC MOSFETs. This study investigates 1700V planar SiC MOSFETs before and after packaging under different HTRB temperatures. Packaged-level devices exhibited breakdown voltage shifts, with distinct degradation trends at 90°C and 17 SoC. Electrical measurements and TCAD simulations suggest that the degradation is caused by contaminants introduced during packaging infiltrating the termination structure, as well as the generation of interface defects. To mitigate these effects, boron doping in the field oxide effectively reduces contamination-related degradation, and a newly designed termination structure is expected to help reduce interface defects.