Design And Characteristics Of High Voltage Silicon Carbide Gate Turn Off Devices

The di/dt and dv/dt capacity is reaching the physical limit of the silicon for the high power device based on silicon material.Silicon carbide material has excellent physical properties such as wide bandgap,high critical electric field,high thermal conductivity and high saturated electron velocity,which brings hope to the development of new generation power device.SiC GTO power device is an ideal switch,which has the advantages of excellent current handling capability,extremely high blocking voltage,low power consumption and fast turn-off speed.And it is suitable for the application in the field of high voltage and high current pulse power.Simultaneously,SiC GTO device is applied in high voltage and high power choppers,inverters and switch circuits because it can reduce the device number connected in series,system volume and the cost.Based on the semiconductor two-dimensional numerical analysis software Synopsys Sentaurus-TCAD,an ultra-high voltage,high pulse current SiC GTO power device is designed.First,the SiC material properties and the physical performance of SiC GTO device were studied and analyzed while the simulation model was established.Next,the structural parameters of the SiC GTO device were optimized.The effects of the blocking voltage,the forward voltage drop and the turn-on time on the electrical performance of the device were compromised to optimize the parameters of the device P⁺anode,N-base layer,P-drift layer,P-buffer layer and N-buffer layer.The breakdown voltage of the cell is 13.4kV,the forward voltage drop is 4.36V@1000A·cm^-2 and the calculated specific on-resistance is 1.5m?·cm².At the same time,the effects of carrier lifetime and temperature on the electrical characteristics of ultra-high voltage SiC GTO devices are studied.Research shows that when the carrier lifetime increases from 1?s to7?s,the device forward voltage(@1000A·cm^-2)decreases by 0.8V;With the increase of temperature,the turn-on time of the device decreases while the turn-off time increases;The 95ns turn-on time is obtained at room temperature when the carrier lifetime is 2.5?s.Subsequently,the pulse characteristics of the device was studied using a double pulse circuit and the pulse current was 35kA/cm² with 1?s carrier lifetime.Secondly,in order to alleviate the electric field concentration effect of the SiC GTO device,this paper adopts the terminal structure of the slowly-changing field limit ring terminal and optimizes the terminal structure parameters.The device breakdown voltage is 12.4kV and achieve 92.5%termination efficiency.Compared with the traditional field limit ring,the length of new terminal is reduced by 100?m under the same voltage withstand capability.Finally,the fabrication technology of ultra-high voltage and high pulse current SiC GTO device was studied.According to the domestic process conditions and design rules,SiC GTO layouts with two different cell structures,strip and square,were drawn for later comparison of tape-out experiments.In this paper,a 10kV,35kA/cm² SiC GTO power device is designed by numerical simulation.The influence of the cell and terminal structure parameters on the electrical characteristics of the device is learned,which provides a reference for the design of domestic high-voltage SiC GTO devices.