Research On Total Dose Effect And Degradation Mechanism Of SiC MOSFET Devices Under Different Conditions

Silicon carbide（SiC）material itself has the advantages of wide band gap,high breakdown field strength,high thermal conductivity and high saturated electron drift rate.It can be used in high voltage,high frequency,high power and high temperature fields.Compared with traditional silicon-based devices,silicon carbide power devices can achieve the purpose of improving the working efficiency of electronic equipment,reducing the size and weight of the device,and increasing the anti-radiation performance,and meet the requirements of the new generation of spacecraft for power semiconductor devices.For SiC MOSFET devices,the total dose effect is an important factor that restricts its long-term stable operation in a space environment.So far,there are few studies on the total dose effect of SiC MOSFET devices,and most of them are based on routine experiments.Based on the above background,this article combines theoretical simulations and total dose irradiation experiments to deeply analyze the degradation law and physical mechanism of the total dose effect of SiC MOSFET devices.The main research content and results of the paper are:（1）In order to study the micro-physical mechanism of the electrical performance degradation of the device caused by the total dose effect,a two-dimensional simulation model of the SiC MOSFET device was constructed using TCAD tools,and the total dose effect was simulated theoretically.The research results show that the increase of the trap charge concentration at the interface state at Si O₂/SiC will not cause the electrical performance of the device to change.The increase of the oxide trap charge concentration in the oxide layer of the device causes the threshold voltage of the device to drift.The oxide trap charge is the main reason for the degradation of the device performance caused by irradiation.（2）In order to study the influence of bias conditions on the total dose effect of SiC MOSFET devices,this paper carried out total dose irradiation experiments under different biases（gate voltage bias,drain voltage bias,zero bias）for SiC MOSFET devices.The research results show that the threshold voltage,breakdown voltage,saturation leakage current and other static electrical parameters of the device change afterγ-ray irradiation;But under different biases,the degree of degradation of the electrical parameters of the device after irradiation is significantly different,Compared with the other two kinds of bias,the degradation degree of the device after irradiation under the gate voltage bias is the largest.the gate voltage bias is the worst bias condition during the irradiation of the device.（3）After determining that the gate voltage bias is the worst bias during irradiation,in order to further study the dependence of the gate voltage on the radiation degradation of the device,The total dose irradiation experiment under different gate voltages（1V,3V,5V,10V,20V）was carried out for SiC MOSFET devices.The experimental results show that when the gate voltage is less than 3V,the threshold voltage drift of the device after irradiation increases with the increase of the gate voltage;When the gate voltage is greater than 3V,the threshold voltage drift of the device after irradiation will decrease as the gate voltage increases.The reduction of the hole trapping cross-section caused by high gate voltage bias is the main cause of the device threshold voltage drift back after irradiation.（4）In order to study the effect of temperature on the total dose effect of SiC MOSFET,the total dose irradiation experiment at room temperature and 100℃was carried out for SiC MOSFET devices,and combined with the annealing experiment at different gate voltages and different temperatures after irradiation,the experiment was carried out.The physical mechanism of the influence of temperature on the device’s total dose radiation degradation.The research results show that the high temperature environment during irradiation will reduce the degradation of the device after irradiation,and tunnel annealing is the main reason for the degradation of the device after high temperature irradiation.