Design Of 1.2kV Trench SiC Power MOSFET

Silicon Carbide Metal-Oxide-Semiconductor Field Effect Transistor(SiC MOSFET)with high breakdown voltage,switching speed and thermal conductivity,and low on-resistance and switching loss has been rapidly developed and widely applied in the field of Power Systems.Compared with the Planar SiC power MOSFET,the Trench MOSFET has higher cellular density,lower conduction loss and higher switching performance,exhibiting better electrical characteristics.However,due to the limitation of process and the reliability of gate oxide,the design of SiC Trench power MOSFET at home and abroad is in its infancy,and further research is urgently needed.This thesis aims to design the overall structure of a 1.2kV SiC Trench power MOSFET.Firstly,the influence of cell structural parameters(including drift layer,Current Spreading Layer(CSL),P-type body layer and P-type shielding region)on the electrical characteristics is analyzed in order to obtain the optimal cell structure.Secondly,the breakdown characteristics of the termination with equal-spaced and non-equal-spaced Field Limiting Ring(FLR)are compared to obtain the optimum termination.Thirdly,the effect of P-well potential and structure on breakdown characteristics is analyzed to design gate PAD region.Finally,the overall structure of the SiC Trench power MOSFET is determined.The simulation results show that,the device has a breakdown voltage of 1592V,a threshold voltage of 6V,a specific on-resistance of 2.35m?·cm²,a specific input capacitance of 33.92n F/cm²,a specific feedback capacitance of 0.11n F/cm²,a specific output capacitance of 3.32n F/cm²,and the Figure Of Merit(FOM_BR)of cell structure is1.08kV²/(m?·cm²)In addition,new structures,SiC Trench MOSFET with Partly Surrounded by Buried N-Layer and SiC Trench MOSFET with Stepped CSL,are proposed in this thesis.In comparison with the traditional trench device with P-type shielding,the specific on-resistance of SiC Trench MOSFET with Partly Surrounded by Buried N-Layer is decreased by 30.6%,and the FOM_BRis increased by33.3%.While the specific on-resistance of SiC Trench MOSFET with Stepped CSL is reduced by25.1%,and the FOM_BRis improved by 22.9%,which all meet the design requirement..