Study On New Structure Mechanism And Characteristics Of High Voltage And Low Power Loss IGBT Devices

As the requirement for emission reduction and energy saving becomes pressing,more and more attention is paid to how to use electric energy efficiently.As the hub of electric energy processing and conversion,power semiconductor devices play a vital role in the high-efficiency conversion of electric energy.Insulated Gate Bipolar Transistor(IGBT)is one of the most widely used power semiconductor devices.It combines the features of field effect transistors and bipolar transistors and has the superiorities of reduced conduction loss and large input impedance.The decrease in V_on of IGBT is due to the conductivity modulation effect in the drift region during on-state.A large number of holes and the electrons are stored in the drift region,which greatly reduces the equivalent resistance of the drift region.However,E_offof the device will also increase as a result,and there is a tradeoff relationship between V_onand E_off.To optimize the trade-off relationship between V_on and E_off,methods such as superjunction technology and short-anode technology have been proposed,but new problems have been introduced at the same time.For example,traditional superjunction IGBT causes V_on to increase,and superjunction IGBT with a floating P-pillar jeopardizes breakdown voltage and short-anode technology will bring about snapback phenomenon and so on.In view of the problems of super junction technology and short-anode technology,this paper proposes two new structures:1.Aiming at the problems of superjunction IGBT,a superjunction IGBT with self-adaptive hole path is proposed.The new device introduces an adaptive hole path on the emitter side.In the forward conduction state,the adaptive hole path is depleted,and a hole barrier is formed,which prevents holes in the drift region from being extracted out by the emitter,enhances the conductivity modulation effect and reduces V_on of the device.In the forward blocking state,the adaptive hole path shorts the P-pillar and the emitter,preventing the P-pillar potential from rising with the rise of the collector voltage,enhancing the modulation effect of the superjunction on the E-field,and effectively improving the forward blocking voltage of the device.During the turn-off process,the adaptive hole path gradually changes from depleted state to neutral state.Holes can be quickly extracted out by the emitter through this path,and E_off is reduced.At the initial stage of turn-on,holes injected from the collector and accumulated under the trench gate can be pumped away through the hole path,and the reverse displacement current during turn-on stage is suppressed.As a result,the controllability of the gate is effectively enhanced.Based on the simulation results,compared with Con.SJ-IGBT,the new structure reduces V_on by 43.1%under the same turn-off loss,and at the same time makes the device performance insensitive to N/P pillar doping.Compared with that of FP SJ-IGBT,BV is increased by 19.7%,and E_off is reduced by 50.5%under the same V_on.Meanwhile,at the same turn-on loss E_on,the d I_C/dt of the IGBT is reduced by 47.2%,the lower limit of d V_KA/dt of FWD is reduced by 68.1%,enhancing the capability of anti-EMI(Electromagnetic Interference)and E_on is reduced by 28.2%at the same value of d V_KA/dt of FWD.2.Aiming at the problems of short-anode technology,a LIGBT with self-adaptive switching n-MOS is proposed.The new structure introduces n-MOS on the anode side with adaptive switching function.In the forward conduction state,because the anode voltage does not reach the threshold voltage of the n-MOS,the n-MOS cannot be turned on and thus the unipolar mode does not work,effectively avoiding the snapback phenomenon.In the forward blocking state,the n-MOS is turned on and formed A flow path of electron leakage current,which prevents the IGBT parasitic PNP transistor from being turned on,and effectively improves the BV of the device.During the turn-off process,the anode voltage rises to turn on the n-MOS,and electrons at the anode side can be quickly drawn away through the n-MOS without waiting for recombination to disappear,as a result,the tail current when the device is turned off is greatly reduced,and the turn-off loss is reduced as well.The simulation results illustrate that when the current density is 100A/cm²,E_off of the new structure is 37.2%lower than that of the traditional LIGBT under the same V_on.Under the same E_off,the V_on of the new structure is 21.7%lower than that of the SSA LIGBT.When the current density is 200A/cm²,under the same V_on,E_off of the new structure is 26.7%lower than that of the traditional LIGBT.Under the same E_off,V_on of the new structure is 23.1%lower than that of the SSA LIGBT.In addition,the new structure will increase the BV by 13.9%.