Research On Switching Characteristics Of Power Trench MOSFET

Power trench MOSFET is the one of the most popular devices in the field of low voltage and high frequency due to its excellent characteristics such as low power consumption,easy integration,small size and so on.However,the gate-drain capacitance(C_gd)of the conventional power trench MOSFET is large,which leads to long switching time and large switching power consumption.Improving switching characteristics has been a hot topic in the research of power slot MOSFET devices.In order to improve the switching characteristics of power trench MOSFET,three kinds of power trench MOSFET devices are proposed.?1?A floating polysilicon junction gate controlled MOSFET structure?FJT-MOSFET?is proposed.The new structure introduces a polysilicon PN junction in the gate.The PN junction capacitance creates an isolation between the gate electrode and the drain electrode,which reduces the gate-drain capacitance and improves the switching characteristics.Compared with the conventional power trench MOSFET structure,the simulation results show that the specific on-resistance(R_on,sp),gate-drain charge(Q_gd),R_on,sp·Q_gd decreases by31.65%,12.39%,39.81%,respectively.The new structure improves the switching characteristics and comprehensive performance of the conventional power trench MOSFET.?2?A trapezoidal gate controlled MOSFET structure?TGC-MOSFET?is proposed.The new structure divides the deep trench into trapezoidal polysilicon gate and trapezoidal oxide layer,and the symmetrical device structure sandwiched the drift region between the oxide layers.The trapezoidal oxide layer optimizes the electric field in the drift region and improves the compromise relationship between R_on,sp and BV.Compared with the conventional power trench MOSFET structure,the simulation results show that the BV increases by 12.71%,the R_on,sp decreases by 75.79%,the R_on,sp·Q_gd increases by 11.6%,and the Figure-of-Merit(FOM,FOM=BV²/R_on,sp)increases by 4.2 times.?3?A P-type polysilicon enhanced MOSFET structure?PE-MOSFET?is proposed.The structure is improved on the basis of TGC-MOSFET.In the trapezoidal polysilicon region,the doping types of the triangular part on the lower side and the rectangular part on the upper side are different,the P-type doping on the lower side and the N-type doping on the upper side.The intra-gate potential is redistributed during device switching,and P-type polysilicon improves the switching characteristics of the device.Compared with the conventional power trench MOSFET structure,the simulation results show that the BV increases by 7.59%,the R_on,sp decreases by 77.38%,the R_on,sp·Q_gd decreases by 45.15%,and the FOM increases by 4.1 times.