A positive impact of low proton irradiation energy on oxynitride gate 4H-SiC MOSFETs

The electrical response of lateral 4H-SiC MOSFET with different thicknesses of N2O gate oxide, and submitted to different irradiation fluences under 0.18 MeV proton energy is reported. After being firstly measured with the time bias stress instability technique (BSI), the MOSFETs were submitted to a short thermal annealing at 120oC for 14h. Regardless the irradiation and the very short annealing time, significant differences with respect to Silicon-irradiated MOSFET have been observed. We associated these differences to the diffusion of nitrogen atoms inside the SiC epilayer but also, to the mobile ion charge tunneling from the same epilayer into the oxide, especially during the annealing process. Finally, if the oxide thickness and the irradiation fluence are balanced, the SiC MOSFET performance can be enhanced, operating in high temperature and harsh environments.