Insights into Overcurrent-Induced Gate Breakdown and Failure Analysis of 1200 V SiC MOSFETs

Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) have been widely studied due to their high switching speed and high voltage resistance. However, its weak short current withstand capability makes SiC MOSFET face many failure problems. This paper presents the experimental results obtained from investigating the impact of overcurrent in SiC MOSFETs. The results indicate that a gate oxide burnout occurs by loading excessive current between source and drain. The failure mechanism is gate breakdown, which can be detected in-situ by monitoring the change in the electrical characteristic curves of SiC MOSFETs. To further analyze the irreversible damage caused by excessive current, thermally induced voltage alteration was initially utilized to locate the failure point. Then, a Focused Ion Beam (FIB) cut is performed, revealing severe burns at the gate area. According to the transmission electron microscopy (TEM) and TEM energy-dispersive X-ray spectroscopy results, it can be observed that the source metal diffuses into the trench of the SiC MOSFET, which is the origin physical failure point of the device.