Short-Circuit Robustness Testing of SiC MOSFETs

This paper presents electrical results for two different commercial devices and one prototype 1.2 kV SiC power MOSFET device subject to short-circuit (SC) stress. Two failure modes were observed among the devices tested, with one mode of failure resulting in catastrophic device destruction and the other resulting in permanent damage of the insulating gate dielectric manifested as a leakage current of 400 mA. Short-circuit pulses of increasing time duration caused a reduction in the gate-to-source voltage toward the falling edge of the pulse. This phenomenon is a precursor to failure of SiC MOSFETs under SC stress, but this reduction in VGS is not known to occur in silicon-based devices. The measured short-circuit withstand times for commercial devices from group A and B MOSFETs were 8 us and 12 us, respectively. MOSFET-C devices had a withstand time of 7 us. A larger chip size improves robustness even for large values of peak short-circuit current.