Precursors of Gate-Oxide Degradation in Silicon Carbide MOSFETs

Abstract

Gate-oxide degradation is more critical in Silicon Carbide (SiC) MOSFETs than in Silicon (Si) MOSFETs. This is because of the smaller gate-oxide thickness and the higher electric field that develops across this thinner gate oxide in SiC MOSFETs. While multiple precursors (indicators) have been identified for monitoring the gate-oxide degradation process in Si MOSFETs, very few have been identified for their SiC counterparts. The purpose of this digest is to demonstrate that the gate-oxide degradation precursors used in Si MOSFETs: a) gate plateau voltage and b) gate plateau time, can also be used as precursors for SiC MOSFETS. Moreover, the precursors are found to exhibit a simultaneous increasing trend (during the stress time) leading to an increase in on-state loss, switching loss and switching time of the SiC MOSFET. The existing studies of gate-oxide degradation mechanisms in SiC MOSFETs, and their effects on threshold voltage and mobility were extended to correlate a variation of precursors using analytical expressions. The increasing trends of precursors were experimentally confirmed by inducing gate-oxide degradation in a commercial SiC MOSFET.