Design And Study Of Sic Light Triggered Thyristor Amplified Gate Structure

Due to its excellent properties,wide bandgap SiC has become the preferred material for high voltage thyristors.Owing to simplifying drive circuits and resisting electromagnetic interference,SiC light triggered thyristors(LTT)become one of the development directions of the ultra-high voltage and large current.The amplified gate structure is an important means to reduce the power density of light triggered thyristor.However,the conventional gate structure of 4H-SiC LTT has the disadvantages of poor reliability and low area utilization.For this end,the device simulation method is used to design and improve the trenched-isolation amplified gate structure.The mechanism,characteristics,the interfacial charges in passivation of amplified gate region and ? irradiation of SiC LTT with trenched-pn junction amplified gate are studied in depth.The main research contents and results are as follows:1.The trench isolation amplified gate structure is improved research.In view of the fact that the breakdown voltage of SiC LTT can not meet the requirements due to the early breakdown at the bottom of the trench,the arc trenched-isolation and trench-pn junction isolation amplified gate structures are used to improve the structure.Through numerical simulation,it is found that the radian of optimized arc trenched-isolation amplified gate is 2.44rad,and the breakdown voltage of SiC LTT is about 73.1%of the theoretical breakdown voltage.Combining with the actual process,the trenched isolation depth of the optimized trenched-pn junction isolation amplified gate is 0.8?m,the doping concentration of the n-type region at the bottom of the gate is 1×1017cm-3,and the breakdown voltage of the SiC LTT is about 98.4%of the theoretical breakdown voltage;Therefore,the trenched-pn junction isolation amplified gate structure is selected as the preferred structure of SiC LTT,and its characteristics are studied.2.The turn-on and forward breakdown characteristics of SiC LTT with trenched-pn junction isolation amplified gate structure were studied.The results show that the performance of the device can be improved by using SiC LTT with the trenched-pn junction isolation amplified gate structure,and the turn-on delay time and anode voltage drop time of SiC LTT with trenched-pn junction isolation amplified gate structure are 2?s and 113ns,respectively,which are decreased by 45.95%and 14.39%,respectively,compared with SiC LTT with the traditional amplified gate.The blocking voltage of SiC LTT with trenched-pn junction isolation is 10.4kV,and the leakage current is slightly reduced.3.The effects of interfacial charges at SiO2 passivation layer and ? irradiation on the breakdown characteristics of the SiC LTT with trenched-pn junction isolation amplified gate structure were analyzed.The fixed negative charges at the SiC/SiO2 interface can significantly reduce the breakdown voltage of the device,,and the breakdown voltage of the device decreases obviously as the fixed positive charge density at the interface is not less than 1×1013cm-2;The device breakdown voltage decreases as the ? irradiation dose increasing,and the positive charge density in the oxide layer increases significantly.The device breakdown voltage is only about 6600V at the irradiation dose of 1000 krad.