Implications of Ageing through Power Cycling on the Short Circuit Robustness of 1.2-kV SiC MOSFETs

In this paper, the reliability performance of 1.2-kV silicon carbide (SiC) power mosfet modules is investigated through the combination of both accelerated power-cycling tests and short-circuit tests. The short-circuit robustness of SiC mosfet is investigated after stressing the dies under power-cycling tests. In this way, the implications of different levels of degradation on the short-circuit capability can be better understood. During the power-cycling tests, some electrical parameters, either related to the package or the die, may experience variations as a consequence of the device ageing (e.g., increase in bond wire resistance and increase in gate leakage current). The effect of these parameter variations on the short-circuit withstanding capability of SiC mosfets is investigated for the first time in this paper. The proposed method helps to understand which degradation effects under normal operation have a major implication on the short-circuit robustness, which gives a more realistic information about the root cause of the failures observed in the field.