Radiation-Induced Effects in SiC Vertical Power MOSFETs Irradiated at Ultrahigh Doses

Total-ionizing dose (TID) and displacement damage (DD) are investigated in SiC power MOSFETs at ultrahigh doses with 10-keV X-ray and 3-MeV protons. Significant parametric shifts in the electrical responses of the devices are observed depending on the bias condition and on the fabrication technology. Worst TID degradation is measured when positive gate bias is applied during the irradiation, due to positive charge trapping in the gate oxide. Devices built in the latest generation SiC technology reveal a smaller subthreshold swing degradation, thanks to a better quality of the SiC/SiO2 interface. Devices exposed to 3-MeV protons exhibit a complex combination of TID and DD effects. The I-V and capacitance-voltage (C-V ) measurements in SiC power MOSFETs identify two main degradation mechanisms: 1) TID-induced charge trapping in the gate oxide and SiC/SiO2 interface and 2) DD-induced lattice damage in the SiC drift region, which degrades the series resistance of the devices.