Impact of low-dose radiation on nitrided lateral 4H-SiC MOSFETs and the related mechanisms

Abstract

Lateral type n-channel 4H-SiC metal--oxide--semiconductor field effect transistors (MOSFETs), fabricated using a current industrial process, are irradiated with gamma rays at different irradiation doses in this paper to carry out a profound study on the generation mechanism of radiation-induced interface traps and oxide trapped charges. Electrical parameters (e.g., threshold voltage, subthreshold swing and channel mobility) of the device before and after irradiation are investigated, and the influence of the channel orientation ( [ 1 1 ¯ 00 ] and [ 11 2 ¯ 0 ] ) on the radiation effect is discussed for the first time. A positive threshold voltage shift is observed at very low irradiation doses (< 100 krad (Si)); the threshold voltage then shifts negatively as the dose increases. It is found that the dependence of interface trap generation on the radiation dose is not the same for doses below and above 100 krad. For irradiation doses < 100 krad, the radiation-induced interface traps with relatively high generation speeds dominate the competition with radiation-induced oxide trapped charges, contributing to the positive threshold voltage shift correspondingly. All these results provide additional insight into the radiation-induced charge trapping mechanism in the SiO2/SiC interface.