Physics of Degradation in SiC MOSFETs Stressed by Overvoltage and Overcurrent Switching

Abstract

This work presents the ruggedness of SiC power MOSFETs outside the safe-operating-area (SOA) conditions based on a hard-switching cycling test. The device was stressed to withstand overvoltage and overcurrent beyond their voltage and current ratings in each switching cycle. This switching cycling test was performed at an ambient temperature of 25 oC and 100 oC. Two independent degradations, one at the gate-oxide and the other at the semiconductor junction region, were observed. The second degradation has not been previously reported in the literature. Both degradations were found to accelerate at the high ambient temperature. The physics of these two device degradations were unveiled: the hot-electron induced gate-oxide degradation accounts for the first device degradation; the electron hopping through the defect states created in the stress tests accounts for the second device degradation.