Trends in SiC MOSFET Threshold Voltage and ON-Resistance Measurements from Thermal Cycling and Electrical Switching Stresses

Integrating SiC power MOSFETs is very attractive for advancing power electronic systems, yet the system reliability with new devices remains in question. This work presents two accelerated test experiments to further investigate the packaging and semiconductor failures of a TO-247 SiC MOSFET. First, a variation on power cycling experiments - switching cycling - is introduced. Traditional power cycling experiments utilize conduction losses to self-heat the device where a large temperature swing causes degradation at the packaging level. However, by decreasing the on-time such that the device only turns on and immediately turns off, the temperature swing is decreased and the semiconductor itself is degraded. This work shows experimental device degradation caused by continuous switching events - switching cycling, at 90% of the device's breakdown voltage. Second, thermal cycling experiments were conducted between -40 °C and 175 °C to observe degradation in the mechanical packaging of the device. Experimentally-measured changes in threshold voltage and ON-resistance are recorded in both experiments and compared. These results also illustrate the spectrum between device and package degradation from accelerated test methods.