Simulation Study Of On-Resistance Of Power MOSFET

Power MOSFET plays an important role in the field of power semiconductor devices,because its high input impedance and fast switching speed,and its application range is expanding.However,as a power MOSFET of a unipolar device,the key problem is that the larger on-resistance increases the on-state power consumption and affects the conversion efficiency of the system.For low-voltage low-power MOSFET,the main purpose is to reduce the size of the device as much as possible,so that it has the characteristics of low on-state voltage drop and large current.For high-voltage high-power MOSFET,it is mainly to solve the problem that the on-resistance increases rapidly with the withstand voltage.Therefore,in order to reduce the on-resistance,different structures should be used for the power MOSFET with different withstand voltage levels.In this thesis,the on-resistance of power MOSFET with different structures under different withstand voltage levels was simulated,the optimization parameters of different structures under different withstand voltage levels were given,and a comparative analysis on the conduction resistance of different structures was made.The voltage level is divided into three levels:low（200V）,medium（600V）and high（1200V）,the structure is represented by VDMOSFET,UMOSFET and SJMOSFET.The specific research contents are as follows:（1）With the characteristic on-resistance as the research goal,the doping concentration,thickness and gate width of the drift region of VDMOSFET with different blocking voltages were optimized.The minimum characteristic on-resistance of the low blocking voltage（200V）VDMOSFET is 0.027Ω·cm^-2,optimization of the parameters as follows:doping concentration1.2×10¹⁵cm^-3,thickness 26μm,gate width 8.4μm;The minimum characteristic on-resistance of the medium blocking voltage（600V）VDMOSFET is 0.215Ω·cm-2,and the corresponding optimization parameters are:doping concentration 2.85×10¹⁴cm^-3,thickness 64μm,and gate width 10μm;The minimum characteristic on-resistance of the high blocking voltage（1200V）VDMOSFET is 0.97Ω·cm^-2,the optimization of the parameters of the corresponding to:doping concentration 1.17×10¹⁴cm^-3,thickness 134μm,and gate width 14μm.（2）Taking the characteristic on-resistance as the research target,the doping concentration,trench depth,and oxide thickness at the bottom of the trench of the UMOSFET with two different blocking voltages were optimized.The minimum characteristic on-resistance of the low blocking voltage（200V）UMOSFET is 0.009Ω·cm^-2,the corresponding optimization parameters are:trench depth 2.8μm,trench bottom oxide thickness 60nm,drift region doping concentration1.2×1015cm-3.The minimum characteristic on-resistance of the UMOSFET with medium blocking voltage（600V）is 0.102Ω·cm^-2.optimization of the parameters as follows:trench depth3.0μm,trench bottom oxide thickness 60nm,drift region doping concentration 2.85×1014cm-3.Compared with VDMOSFET,the results show that:for low voltage（200V）level devices,the characteristic on-resistance of UMOSFET is much smaller than VDMOSFET,for medium voltage（600V）level devices,the characteristic on-resistance of UMOSFET is slightly less than VDMOSFET.（3）Taking the characteristic on-resistance as the research goal,the parameters such as the column height,N-pillar concentration,and P-pillar concentration of the SJMOSFET with a blocking voltage of 1200V were optimized.The characteristic on-resistance of 1200V SJMOSFET is 0.079Ω·cm^-2.Compared with VDMOSFET,the characteristic on-resistance of1200V SJMOSFET is smaller.The research on the characteristic on-resistance of power MOSFET with different structures and different withstand voltages shows that UMOSFET can effectively reduce the characteristic on-resistance of low-withstand-voltage VDMOSFET.SJMOSFET can effectively reduce the characteristic on-resistance of high-voltage power MOSFET,suitable for making high-voltage power MOSFET.