Experimental analysis of electro-thermal instability in SiC Power MOSFETs

In this paper we experimentally demonstrate that SiC high voltage Power MOSFTEs exhibit an unstable electro-thermal behavior for given electrical conditions, depending on the chip thermal impedance. This instability can lead to hot-spot formation and eventually thermal runaway whit subsequent device destruction after a stressful short-circuit. The analysis was carried out on a commercial 1.2 kV SiC Power MOSFET by investigating the device electro-thermal behavior in short-circuit operation with a state-of-art IR thermographic set-up. By biasing the device at different gate voltages, the stable and unstable regions are evidenced with electrical and thermal measurements. Finally an unstable behavior is triggered and an hot-spot coherent with the failure location is demonstrated