Investigation on Surge Current Capability of 4H-SiC Trench-Gate MOSFETs in Third Quadrant Under Various VGS Biases

In this work, third-quadrant I-V characterization and surge current tests are carried out on SiC asymmetric trench MOSFET (DUT A) and SiC double-trench MOSFET (DUT B) under various gate-source biases (VGS). The surge capability is found to be uninfluenced by VGS for DUT A. However, it has a 71.4% increase when VGS changes from 0V to -5V for DUT B. The I-V characteristics in third quadrant are measured under various VGS. It is found that the channel is open when the source-drain voltage is >2.5V for DUT A and >1.5V for DUT B at VGS=0V. High temperature measurements are also conducted from 298K to 448K. When VGS=0V, the channel current takes up to 50% at 10A source-to-drain current for DUT B, whereas only 10% for DUT A. This could lead to high current/heat density in the channel of DUT B. The transient resistance is also extracted from the surge I-V trajectories and it is higher for DUT B tested under VGS=0V, which will increase the dissipated surge energy. Finally, failure mechanism is analyzed. For DUT A, aluminum melting contributes to the failure at VGS=-5V and VGS=0V. For DUT B tested at VGS=0V, earlier breakdown happens due to gate oxide failure.