Impact of Repetitive Short-Circuit Tests on the Normal Operation of SiC MOSFETs Considering Case Temperature Influence

This article presents the impact of repetitive shortcircuit (SC) tests on the normal operation of a commercial silicon carbide (SiC) MOSFET and the influence of different case temperatures on the SC degradation process. To ensure repeatable SC test conditions, the maximum SC withstanding time is studied at three different case temperatures and the critical energy is identified. To investigate the effect of SC stress on the normal operation, the static and dynamic characteristics are periodically measured along with the repetitive SC activity. The turn-on switching loss increases gradually with the increasing number of repetitive SC tests. This is associated with the increase in the gate leakage current during the SC tests, which shows a reduction in the ON-state gate voltage because of the gate oxide degradation. Then, since the case temperature of the device is subject to the operating condition in the application, the degradation process of repetitive SC tests with respect to different case temperatures is investigated, and the relationship between the number of repetitions to failure and the initial case temperature is established. Finally, the case temperature influence is explained by a 1-D transient thermal model based on the SC condition.