Solid State Phenomena Vol. 375

Abstract: In this study, high current stress was applied to the body diode of SiC-MOSFETs, and chips exhibiting leakage current degradation due to the bipolar degradation phenomenon were analyzed to identify the crystal defects responsible for the abnormal leakage current. Failure analysis and defect inspection during the device fabrication process revealed that abnormal leakage occurred at the periphery of extended stacking faults originating from or near the micropipe itself. As these extended stacking faults also increase the forward voltage drop of MOSFETs, these results suggest that micropipe are critical defects in SiC-MOSFETs inducing both forward voltage and leakage current degradation in the bipolar degradation phenomenon.

Abstract: In this paper, a method for suppressing bipolar degradation through proton implantation was investigated. Previous work suggests implantation applied to the full thickness of the epi layer, which results in unwanted defects leading to a deterioration in performance. In this work, proton implantation to the buffer layer was successful in reducing the forward-voltage drift ΔV_F of the fabricated SiC PiN diode by 85% at a current density of 800A/cm², when applying room temperature (RT) proton irradiation at a dose of 1×10¹⁶ cm^-2. Irradiation solely to the buffer layer keeps the deterioration of forward current performance to a minimum, while the fabricated SiC PiN diodes are more robust against bipolar degradation at higher current density. In addition, RT proton irradiated PiN diodes show full recovery from their bipolar degraded characteristics within 2.5 h of annealing at 350 °C under vacuum. This indicates proton irradiation alters the crystal structure for the stacking fault (SF) to “shrink” back with ease to their initial basal plane dislocations (BPD) state.