New Gate Leakage Degradation Behavior and Mechanism Induced by Heavy-Ion Irradiation in High-Voltage Silicon Carbide MOSFETs

In this study, a new gate leakage degradation (GLD) mechanism induced by heavy-ion irradiation was identified for the first time in high-voltage silicon carbide (SiC) MOSFETs. The gate leakage current properties of devices were investigated under multiple distinct bias voltages applied during heavy-ion exposure. It was observed that there is an obvious turning point existing in the degradation trend of the gate leakage current properties during irradiation, indicating a critical transition in the underlying physical processes. Through comprehensive postirradiation tests, including postirradiation gate stress (PIGS) tests, temperature-dependent tests, and postannealing tests, this new GLD mechanism has been systematically investigated. Two competing degradation mechanisms have been identified that take place on carrier transport paths and that cause the gate leakage current degradation. It was found that with the increase of heavy-ion irradiation-induced gate leakage, the main GLD mechanism gradually transforms from Fowler–Nordheim (FN) tunneling to Poole–Frenkel (PF) emission, which is confirmed by the temperature-dependent and postannealing tests. Moreover, a stress-induced transition in the degradation mechanism was also identified. Electrical characterizations, combined with scanning electron microscopy (SEM) and focused ion beam (FIB) analysis, revealed distinct morphological signatures associated with each degradation mechanism, establishing a clear correlation between electrical degradation behavior and microstructural evolution.