Avalanche capability degradation of the parallel-connected SiC MOSFETs

Abstract

Silicon carbide (SiC) MOSFET chips are often connected in parallel in a module to increase the current rating. However, the current capability is degraded due to unbalanced current and temperature distributions which affect the avalanche processes particularly in extreme operating conditions. To obtain the root cause of the degradation and identify the dominant factors, single-pulse avalanche testing is carried out in this study, and TCAD simulation is used for mechanism analysis. It is revealed that electrothermal parameters have different effects on current sharing in different stages of avalanching. The corresponding failure mechanisms are analyzed, and the main cause of avalanche failure with parallel devices is found to be the difference in breakdown voltage. Device with smaller BV shares more current as well as more heat, which fails first eventually. To resolve such issues, proper device screening/paring should be carried out. The findings are helpful for a better understanding of avalanche capability degradation in parallel devices application.