The electrical behaviour of irradiated and post-irradiation annealed nMOSFETs with an implanted p-type body and having a N 2 O oxynitrided gate oxide is analysed in this work. This study reveals the existence of a “threshold fluence” which might change the predominant SiO 2 /SiC interface charge trapping type from donors to acceptors at a given energy. The irradiation fluence and energy limit that guaranty a normal or improved operation of the MOSFETs are also given.

This work presents the 10 MeV protons irradiation effects on 4H-SiC MOSFETs at different fluences. MOSFETs main electrical parameters, such as the channel mobility (µEFF), threshold voltage (VTH), transconductance (gm) and subthreshold current, were analyzed using the time bias stress instability (BSI) technique. Applying this method allowed us to study the effect of carriers interaction with generated interface traps, whether in the bulk or at the interface. Improvements, such as VTHstabilization in time and a significant increase of the µEFFat high fluencies, have been noticed. We assume that this behavior is connected with the atomic diffusion from the SiO2/SiC interface, towards the epilayer during proton irradiation. These atoms, in majority Nitrogen, may create other bonds by occupying various vacancies coming from Silicon and Carbon’s dangling bond. Therefore, by enhancing the passivated Carbon atoms number, we show that high irradiation proton could be a way to improve the SiO2/SiC interface quality.

The 4H-SiC MOSFET electrical response to 180 keV proton radiations at three different fluences has been evaluated. For a certain dose, the devices show an apparent improvement of their electrical characteristics likely due to the N and/or H atoms diffusion inside the oxide layer. This work complete our previous studies on high energy proton irradiation, showing that the 4H-SiC MOSFET is also robust to the low energy proton radiation, when the proton implanted range is located near the MOS interface.

The impact of proton and electron irradiation on the electrical parameters of 4H-SiC nMOSFETs has been investigated by using time bias stress instability method. This study has allowed observing the effect of holes trapped in the oxide together with the generated interface traps. Improvements of important electrical parameters, such as the threshold voltage, the effective mobility and the maximum drain current were observed. These improvements could be connected with the Nitrogen and residual Hydrogen atoms diffusion from the SiO2/SiC interface toward the epilayer during irradiation. These atoms are likely to create other bonds by occupying the Silicon and Carbon's dangling bond vacancies. This way, the number of passivated Carbon atoms is increasing, hence improving the SiO2/SiC interface quality.

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.