Study On Novel Reverse Conducting IGBTs At 1200V

Insulated Gate Bipolar Transistor(IGBT)has the advantages of high switching frequency,low conduction voltage drop,simple driving circuit and so on.Now it has become a choice in the field of medium and high voltage power switch.However,because IGBT itself has no reverse conduction capability,its reverse parallel fast recovery diode is used as a freewheeling protection in practical application circuits.In order to reduce the use cost and reduce the parasitic inductance produced by the two welds,people began to try to integrate the continuous flow diode and IGBT through the process integration on the same chip,and develop the IGBT chip(Reverse-Conducting Insulated Gate Bipolar Transistor,RC-IGBT)with the reverse conduction ability.At present,RC-IGBT can't replace the traditional IGBT and diode modules,because there are still many problems to be overcome.Including the forward conduction process will generate voltage jump,drift area current distribution is uneven,and reverse work recovery loss is too large.In view of the phenomenon of voltage snapback during forward conduction,a novel short-circuit area structure proposed in this paper adopts dielectric isolation technology to increase the short-circuit resistance of the device,The SiO2 trench is used to isolate the low impedance electronic channel of the field stop layer,and the electronic barrier formed by the P pillar region increases the short circuit resistance of the device,By controlling the height,width and concentration of the P pillar region,the voltage snapback phenomenon can be effectively suppressed.with this structure,the cell width can be reduced to 1/8 of conventional RC-IGBT,and its forward and reverse characteristics are improved.In view of the poor recovery performance of RC-IGBT in diode operation,this paper proposes a fast recovery RC-IGBT structure and its main process flow.By means of self isolation,the p-float is formed by ion implantation over the N+ collector,and the effect of the snapback can be eliminated by controlling the size of the Lgap and the concentration and height of the p-float.the new cell width can be reduced to the 1/10 of the conventional RC-IGBT,p-float region can reduce the efficiency of the electron injection in the diode mode,and reduce the hole injection in the diode mode with the reduced P-base structure,and finally achieve the design requirements of the fast recovery.The results show that the reverse recovery is restored.The recovery time was reduced by more than 30%.