Investigation on the Resistance Degradation of Trench SiC MOSFETs under Total Ionizing Dose Irradiation and High Drain Voltage Bias

In this paper, the resistance degradation behaviors of double trench (DT) and asymmetric trench (AT) SiC MOSFETs under total ionizing dose (TID) effect and high drain voltage bias are investigated in detail. The output characteristics measurement results before and after irradiation indicate that the TID effect with high drain voltage bias increases the drain current, resulting in the On-state resistance degradation, whereas the high drain voltage bias seems to have no impact on the degradation. In particular, the DT SiC MOSFETs demonstrate a greater degree of degradation in comparison to the AT SiC MOSFETs under the same gate voltage. This phenomenon can be attributed to a more pronounced decline in channel resistance. Simultaneously, the threshold voltage ( V TH ), the drain leakage current ( I DSS ), and the gate leakage current ( I GSS ) are also measured, which can be concluded that the resistance degradation is attributable to the V TH negative shifting induced by the positive charge accumulation in the gate oxide. Furthermore, the AT SiC MOSFETs have better irradiation tolerance owing to the P-shield asymmetric trench structure, exhibiting slight shift in the V TH , the I DSS , and the I GSS . Finally, the TCAD simulations are utilized to successfully verify the degradation mechanism.