. (2015) Temperature and switching rate dependence of crosstalk in Si-IGBT and SiC power modules.

Threshold voltage (VTH) shift due to Bias Temperature Instability (BTI) is a well-known problem in SiC MOSFETs that occurs due to oxide traps in the SiC/SiO2 gate interface. The reduced band offsets and increased interface/fixed oxide traps in SiC MOSFETs makes this a more critical problem compared to silicon. Before qualification, power devices are subjected to gate bias stress tests after which VTH shift is monitored. However, some recovery occurs between the end of the stress and VTH characterization, thereby potentially underestimating the extent of the problem. In applications where the SiC MOSFET module is turned OFF with a negative bias at high temperature, if the VTH shift is severe enough, there may be electrothermal failure due to current crowding since parallel devices lose synchronization during turn-ON. In this paper, a novel method that uses the forward voltage of the body diode during reverse conduction of a small sensing current is introduced as a technique for monitoring VTH shift and recovery due to BTI. This non-invasive method exploits the increased body effect that is peculiar to SiC MOSFETs due to the higher body diode forward voltage. With the proposed method, it is possible to non-invasively assess VTH shift dynamically during BTI characterization tests.

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