Gate-damage safe failure-mode deep analysis under short-circuit operation of 1.2kV and 1.7kV power SiC MOSFET using dedicated gate-source / drain-source voltage depolarization and damage-mode optical imaging

Robustness of 1.2kV and 1.7kV Silicon Carbide MOSFETs submitted to short-circuit operations mode is studied. Experimental results confirm two main failure modes: a safe fail-to-open mode and an unsafe fail-to-short mode. A technique based on direct depolarization of gate source voltage is used to increase the short-circuit withstand capability and to partially obtain a fail-to-open mode. Electro-thermo-metallurgical simulations are investigated to deeply explain the fail-to-open mechanisms. Finally, using lock-in-thermography and scanning-electronic-microscopy imaging, a new and spectacular lift-off effect of gate-finger is highlighted to clearly confirm the fail-to-open mode capability such devices.