IGBT Dynamic Electric Field Modulation Turn-off Mechanism And New Structure

Insulated Gate Bipolar Transistor(IGBT)is playing a crucial part in applications like railway,household appliances,smart grid and electric vehicles due to its advantages of high input impedance,low on-state voltage,and low driving loss.The mechanism of IGBT leads to a trade-off relationship between its on-state voltage(V_on)and turn-off loss(E_off).In order to reduce the total power consumption of IGBT,technologies and structures have been proposed to optimize the trade-off relationship between V_on and E_off.Faster turn-on speed helps to reduce the turn-on loss(E_on),but at the cost of significant electromagnetic interference(EMI)noise.Therefore,it is of great significance to optimize the trade-off relationship between E_on and the d V_KA/dt across the freewheeling diode.In this thesis,the dynamic electric field modulation turn-off mechanism is studied and a dynamic electric field modulation IGBT is proposed,as well as a dule hole barriers IGBT.1.The dynamic electric field modulation turn-off mechanism is studied and a new IGBT structure is proposed.Most of the existing IGBT structures and technologies reduce E_off by optimizing the carrier concentration distribution during on-state,which inevitably increases the V_on of the device,impeding the further optimization of the trade-off relationship between V_on and E_off.This thesis focuses on reducing loss by optimizing the dynamic electric field.Dynamic electric field distribution and current during turn-off are deduced by semiconductor physics equations,and the dynamic electric field modulation turn-off model is proposed.According to the dynamic electric field modulation turn-off mode,a new IGBT(DEM-IGBT)with low turn-off loss is proposed.Compared with the state-of-the-art Carrier Stored Trench-Gate Bipolar Transistor(CSTBT),the DEM-IGBT features a P-drift region.During the turn-off process,it helps to build the electric field more rapidly during the voltage rise phase,and reduce the excess carriers during the current fall phase.Compared with the CSTBT,the turn-off time(t_off)of the DEM-IGBT is reduced by 46%.At the same V_on,E_off of the DEM-IGBT is 60%lower than that of the CSTBT,indicating an optimized V_on-E_off trade-off relationship.Meanwhile,DEM-IGBT also improves the trade-off relationship between E_on and surge current under small current turn-on(I_surge).2.A dule hole barriers IGBT(DHB-IGBT)with low EMI noise and low loss is proposed.The structure features an emitter side semi-superjunction(ESJ)and a carrier stored(CS)layer,forming the dual hole barriers(DHB).The depletion of ESJ introduces a lateral electric field modulation during turn-on process,which effectively suppresses the accumulation of holes both under the gate oxide layer and in the floating-P region.The CS layer forms the second hole barrier,which further suppresses the hole accumulation in the floating-P region.Therefore,the displacement current during turn-on is reduced.At the same E_on,d V_KA/dt of the DHB-IGBT is reduced by 62%and 52%compared with Hole path IGBT(HP-IGBT)and IGBT with Fin P-body(Fin-P IGBT),respectively.DHB-IGBT reduces the EMI noise and also features a better V_on-E_off trade-off relationship.