SPICE Model Research Of Silicon Carbide VDMOS Device

Silicon carbide semiconductor material has the advantages of wide band gap,high saturation speed,high critical breakdown electric field and high thermal conductivity,the vertical double implantation of metal oxide semiconductor field-effect transistors(VDMOS)based on silicon carbide substrate have been widely concerned and applied in recent years.The SPICE model is the bridge between the device process and the circuit design.A precise SPICE model of silicon carbide VDMOS device is critical to the design of high performance power integrated circuits.However,there is not a SPICE model which can accurately describe the characteristics of silicon carbide-based VDMOS device.Therefore,the research on silicon carbide-based VDMOS device modeling is of great significance.In this thesis,a complete silicon carbide VDMOS device compacted model is developed for circuit simulation.Firstly,the basic structure and working principle of silicon carbide VDMOS device is introduced,and the influences of device structure and high density interface state on silicon carbide VDMOS device are analyzed emphatically.For the DC part of the silicon carbide VDMOS device,the current model based on the surface potential is proposed for the channel region,and a simple calculation method of surface potential is proposed.Then the drift region is divided into accumulation region,JFET region,N-extension region and N+ substrate region,and the current models of the four regions are established,respectively.Considering the effects of secondary physical effects and interface charge on the device,the threshold voltage shift model,mobility model,velocity saturation model and self-heating model are proposed.For the AC part of the silicon carbide VDMOS device,the internal charge is divided according to the motion path of the carrier,on the basis of the DC model,the end-charge model of silicon carbide VDMOS device is established.Finally,the SPICE model of silicon carbide VDMOS device is realized by Verilog-A language,and the model is validated by measured data.The mean square errors(RMS)of the DC model and AC models of the silicon carbide VDMOS device are within 5%and 10%,respectively,and the compared results demonstrate that the model gives accurate descriptions for both DC and AC characteristics of silicon carbide VDMOS device.The accuracy and convergence of the model meet the expected target.The silicon carbide VDMOS device model proposed in this paper has important guiding significance for the design of power integrated circuit and system.