Investigation on Degradation of SiC MOSFET Under Accelerated Stress in PFC Converter

The reliability of SiC MOSFETs becomes crucial to their widespread applications. However, its reliability under practical operating conditions are more complicated than that under conventional power or thermal cycling tests, and not yet extensively studied. In this paper, the degradation of SiC MOSFET under accelerated stress in PFC converter is investigated. An online monitoring system is implemented to continuously monitor the on-state voltage of SiC MOSFET. Online experimental results show that the increase of on-state voltage is approximately linear with increasing cycles. The electrical characteristics of SiC MOSFETs before and after test are compared and analyzed. The comparison results illustrate that the increase of on-state resistance can be attributed to the degradation of both package and semiconductor die. The variation of threshold voltage, gate leakage current and capacitance indicate that the accumulation of positively charged traps in the gate oxide of SiC MOSFET takes responsibility for the die degradation.