Determination of Short-Circuit Safe Operating Area of Trench SiC MOSFETs Under Repetitive Stress Conditions

In this work, repetitive short-circuit measurements are performed on symmetrical double-trench and asymmetrical trench silicon carbide (SiC) MOSFETs under different short-circuit durations (tsc) and drain-source voltages (Vds). The short-circuit safe operating area (SCSOA) of SiC MOSFETs is characterized. Results show that the failed devices under all test conditions exhibit gate-source short-circuit failure. The number of cycles to failure is related to the short-circuit energy (Esc), which is affected by tsc and Vds. Besides, an important result demonstrated by the measurements is that the increase in Vds bias can reduce the reliability of SiC MOSFETs even under the same Esc. However, the devices that were electrothermally stressed below certain Esc thresholds maintain high reliability without degradation even at high Vds. Mathematical models were developed to describe the relationship between the number of short-circuit cycles and the test conditions for both types of trench SiC MOSFETs. It is revealed that if parallel trench SiC MOSFETs are driven outside the SCSOA, even a small difference in Esc is able to cause reliability disparities, which will ultimately affect the overall reliability of the power electronics system.