Study On Radiation Damage Of Silicon-based Power VDMOS Devices

Power VDMOS devices are widely used in aerospace electronic equipment due to many advantages such as high withstand voltage,high withstand current,fast switching speed and stable frequency characteristics.However,the radiation particles in a complex space environment will pose a serious threat to the normal operation of the device.In order to study the effect of radiation damage on the electrical characteristic of VDMOS devices,this paper conducted three kinds of power VDMOS devices with different dose rate gamma-ray irradiation experiments,30 Me V silicon ions irradiation experiments,and 1Me V high-energy electron irradiation experiments at 300 K and 80 K ambient temperatures.Through the above experiments,dose rate effects,comparison of ionization and displacement effects and the temperature and radiation synergy effects of VDMOS devices were studied respectively.In this paper,the mid-band voltage method is used to separate and extract the changes of threshold voltage,oxide trap charge and interface state trap charge in VDMOS devices.In addition,some devices were tested for deep-level transient spectrum and combined with simulation to verify some conclusions.The results show that the radiation damage of the VDMOS device after the low dose rate ?-ray irradiation is more serious,and the threshold voltage drift of the device is larger.Compared with high-dose-rate gamma-ray irradiation,the ratio of unrecombination electron-hole pairs which produced by irradiation in the oxide layer of the device is greater than that of high-dose-rate irradiation.It results in a higher density of oxide trap charges.Because low-dose-rate irradiation experiments take a long time,the interface state traps have enough time to establish,and the total absorbed dose is lower when it reaches saturation.30Me V silicon ions irradiation will cause ionization damage and displacement damage in VDMOS devices.Displacement damage is mainly a body trap in silicon,and the trapping and scattering of carriers cause the saturation drain current of the device to decrease and the leakage current to increase.The ionization damage is basically the oxide trap charge,which causes the threshold voltage of the device to drift negatively.Ionizing radiation damage mainly occurs in the device after the 1Me V electron irradiation.The threshold voltage of the device drifts towards negative direction,and the saturation drain current decreases.Irradiation generates more oxide trap charges than interface state trap charges.When irradiated at a low temperature of 80 K,the radiation damage appears as a large amount of oxide trap charges,and the interface state trap charges are basically not formed.The threshold voltage of the device drifts negatively,and the leakage current is too high.Study on dose rate effects,comparison of ionization and displacement damage,temperature and radiation synergy effects can explore the generation mechanism of different radiation damage in VDMOS devices,and study the reliability of the device in different radiation environments,which are significant to improve the manufacturing process and structural design of the radiation resistance devices.