电子辐照对SiC功率MOSFET器件动态特性的影响机理

This paper studies the impact of electron irradiation on the dynamic characteristics of 1 200 V SiC MOSFETs and the corresponding mechanism in an attempt to tackle the aging of SiC power field-effect transistors used in high-energy particle irradiation applications such as the space and nuclear industry. First, the SiC MOSFET is irradiated with a dose of 200 kGy under 10 MeV electron beam. Then the SiC MOSFET is tested for switching in a double-pulse test circuit, and parameters such as switching speed and switching transient energy loss are recorded. After that, the static characteristics of the device are tested to obtain the threshold voltage, gate resistance, parasitic capacitance and other parameters. Finally, the impact of electron irradiation on the dynamic characteristics of SiC MOSFETs is analyzed by comparing the dynamic and static characteristic parameters of irradiated and non-irradiated devices. The results show that the turn-on delay time of the irradiated device is reduced by 11.6 ns, the turn-on transient energy loss is reduced by 0.18 μJ, the turn-off delay time increases by 48.4 ns, and the turn-off transient energy loss increases by 0.11 μJ under a drain voltage of 800 V, a drain current of 15 A, and an external gate resistance of 200 Ω. It is found that the positive fixed charge in the oxide layer increases by 7.14×1011 cm^-2 after irradiation, and the threshold voltage of the device decreases by 1.5 V; ionizing electron irradiation in the oxide layer creates electron hole pairs and the oxide layer traps the holes and form positive fixed charges, which reduces the threshold voltage of the device. This is the main reason for faster turn-on and slower turn-off of the device after electron irradiation. The research results can provide some reference for the application of SiC power devices in the irradiation environment and for manufacturers to improve the reliability of SiC MOSFETs in the irradiation environment.