Burn-out failure analysis of SiC MOSFET power device after HTRB

SiC MOSFETs have become indispensable core components in vehicle power systems with their high-voltage tolerance, high-frequency operation, and excellent thermal stability. However, their failure mechanisms under environmental stress remain poorly understood. This study conducted 175℃ High Temperature Reverse Bias (HTRB) tests on automotive-grade SiC MOSFETs and employed comprehensive microscopic characterization methods to reveal the failure mechanisms of SiC power devices. Experimental data showed that after 200 hours of HTRB testing, the threshold voltage (VTH) curve became disordered until undetectable, while IGSS and IDSS surged dramatically, far exceeding device specification limits, ultimately leading to thermal breakdown. Internal chip observations via FIB revealed fractures in the unit structure due to thermal expansion coefficient mismatch. EDS analysis further confirmed ionic contamination in the dielectric layer crack regions. These findings clarify a dual failure mechanism: bonding interface defects causing localized thermal runaway, and thermal expansion mismatch in the gate-dielectric-source multilayer structure inducing penetrating cracks.