Study On The Turn-off Characteristics And New Structure Of High Speed IGBT

IGBT is one of the core power devices in the field of power electronics,which has the advantages of low driving power,high input impedance,high breakdown voltage,low on-voltage drop,and strong current capability.However,there are the long current tail and the slow turn-off speed when the device is turned off.The fast switching speed is beneficial for IGBT to expand to medium and high frequency applications field,and to improve the contradiction between on-voltage(V_on)and turn-off energy loss(E_off).Some common measures such as the shorted anode?SA?,the thinned drift regions,and the minority carrier lifetime control can effectively speed up the turn-off process,but those methods are also accompanied by some negative effects.For example,the undesirable snapback phenomenon occurring in SA LIGBT and the big V_on and weak current capability of ultra-thin top-silicon devices.In order to solve the above problems,this thesis will propose two novel fast switching IGBT devices based on two different fast switching solutions:1.A fast switching LIGBT with a dual carrier extraction path is proposed.The new structure features:dual P-type poly-filled anode trenches and an N-region between the two trenches are introduced on the anode side,which form the Self-Adaptive Resistance?SAR?structure;A N-type poly-filled trench adjacent to the P+cathode region on the cathode side,which forms the Hole Accumulated Trench?HAT?structure.When the device turns off,the excess electrons and holes in the drift region are quickly extracted by SAR and HAT structures respectively,the proposed IGBT can be turned off quickly.At the same time,SAR structure can effectively eliminate the snapback phenomenon,reduce the on-resistance and increase the blocking voltage;HAT structure improves the short-circuit withstand ability by enhancing the anti-latchup ability.The simulation results show that the E_off of the LIGBT with only the SAR structure is reduced by20.6%,28.1%,and 30.5%compared to those of the MSA,STA,and SA-NPN LIGBT under the same V_on.At the same E_off,the V_on of HAT LIGBT is reduced 27.2%compare to that of SSA LIGBT.For LIGBT with only HAT structure,the E_off has decreased by55.4%compared to that of the Con LIGBT under the same V_on;at the same E_off,the V_onn is improved by 17.4%compared to that of SSA LIGBT;the short circuit withstand time of HAT LIGBT is increased by 325%and 77.9%compare with those of SSA and Con LIGBT,respectively.For the proposed new device with both two structures,at the same V_on,the E_off is improved by 27.8%and 39.1%compared with those of the LIGBT devices with only SAR or HAT structures,respectively.And the short-circuit withstand time is extended by 256.6%and 91.5%compare to those of the SAR and HAT LIGBT,respectively.2.A T-type triple-gate ultra-thin SOI LIGBT device with a carrier storage layer is proposed.The main features are:the ultra-thin top-silicon layer,A triple-gate structure?T-type Triple Gate,T-TG?is composed of a T-type planar gate and a double L-shaped trench gate on the cathode side,and a carrier storage layer?Carrier Storage Layer,CSL?surrounded by the T-TG structure.These two structures greatly improve the current capability and the carrier concentration in the drift region of the device,which makes the IGBT device get small V_on while the turnoff speed is extremely fast.By simulation verification,when the gate voltage V_G=8V,the saturation current density of the new device is increased by 29.03%compared with that of Con LIGBT.At the same V_on,the E_off of the new device is reduced by 35.09%and 54.12%compared with those of CS and Con LIGBT,respectively.