Short-Circuit Capability Prediction and Failure Mode of Asymmetric and Double Trench SiC MOSFETs

In this article, short-circuit capability prediction and failure mode of 1200-V-class SiC MOSFETs with a double and asymmetric trench structure are proposed under single-pulse short-circuit stress. A short-circuit prediction model is established to evaluate short-circuit withstand time and corresponding critical energy of devices under various dc bus voltages. This model can provide quick predictive guidance even if there are few test results, and the predicted values are consistent with practical values. Furthermore, two failure modes are investigated in a short-circuit test. For asymmetric trench SiC MOSFETs, failure modes are gate damage at lower dc bus voltages and thermal runaway at higher dc bus voltages; whereas failure mode for double trench SiC MOSFETs is thermal runaway at all dc bus voltages. In addition, the internal thermal-electro stress of the device is analyzed until it fails during short-circuit condition, and proves that failure mode depends on the dc bus voltage and peak short-circuit current of the device. Finally, the top view of failed devices confirms the two failure modes of trench SiC MOSFETs by the postdecapsulation.