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

Abstract

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-thermometallurgical 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.

SiC power MOSFET overload detection, short-circuit protection and gate-oxide integrity monitoring using a switched resistors dual-channel gate-driver

“…In addition to improvements in chip architecture design, another approach consists in functionalising the gate-driver to efficient shortcircuit / over-current handling and dedicated gateoxide health monitoring -conditioning strategies. Among the previous work of the authors on discrete 1.2kV and 1.7kV SiC power MOSFETs, it was shown in [3] [4] that the reduction of the short-circuit power density to 4kW/mm² made it possible to exceed the threshold of 10µs short-circuit withstand time capability (TSCW) and to bring the chip to a safe gatesource short and drain-source open failure mode (Failto-Open FTO mode). Other authors have confirmed this property [5].…”

“…3a, a power density reduction is provided by the proposed gate-driving architecture, thus allowing to avoid a thermal runaway. The gate region's thermomechanical stress is then the phenomenon governing the chip's main failure mechanism [4][5] should no protection be used or if repetitive shorts are applied [12]. Fig.…”