Novel Snapback-free Reverse Conducting IGBT Structure And Design

IGBT?Insulated Gate Bipolar Transistor?is a kind of composite device,which is a BJT?Bipolar Junction Transistor?drived by a MOSFET?Metal Oxide Semiconductor Field Effect Transistor?.IGBT has the advantages of both MOSFET and BJT,so the device has been widely researched and applied since its inception.However,since the IGBT cannot conduct reversely,it is usually required to connect an anti-parallel FWD?Free Wheeling Diode?between the IGBT in practice.Initially,IGBT and FWD are directly connected together by wire bonding,but this method inevitably introduces parasitic inductance and is costly.To solve the problems above,engineers integrated IGBT and anti-parallel FWD on the same chip,and proposed the RC-IGBT?Reverse-Conducting IGBT?.However,due to the inherent structure of the conventional RC-IGBT?Con-RC-IGBT?,voltage snapback phenomenon occurs during the forward conduction of the device,limiting the application of the Con-RC-IGBT.Therefore,this article carries out research on eliminating the voltage snapback phenomenon in Con-RC-IGBT by using Sentaurus TCAD simulation software.In order to suppress the voltage snapback phenomenon of the Con-RC-IGBT,two new structures are proposed in turn.Firstly,a novel RC-IGBT with a sandwich collector structure?Sandwitch RC-IGBT,San-RC-IGBT?was proposed.The collector short-circuit resistance is increased by introducing a high-resistance N^-layer between the N⁺/P⁺collector region and the field stop layer.As a result,the voltage snapback phenomenon will be greatly improved.However,compared with Con-RC-IGBT,the breakdown voltage of the San-RC-IGBT is reduced and the reverse recovery characteristics become worse.In order to improve the dynamic characteristics of the San-RC-IGBT,by introducing Semi-SuperJunction into the collector side of the San-RC-IGBT,a Semi-SuperJunction RC-IGBT with a sandwich collector structure?SSS-RC-IGBT?is proposed.Simulation results show that the voltage snapback phenomenon will disappear in SSS-RC-IGBT.The introduction of the Semi-SuperJunction improves the electric field distribution in the depletion region in the forward blocking mode,which makes up for the reduction of the breakdown voltage caused by the introduction of high resistance N^-layer.Compared to Con-RC-IGBT,the turn-off loss of the SSS-RC-IGBT is reduced by 30.6%,and the reverse recovery loss is reduced by 21.2%.Meanwhile,SSS-RC-IGBT has a better trade-off relationship between the forward conduction voltage drop and the turn-off loss.In view of the application of asymmetrical forward and reverse conduction time of the device,an avalanche RC-IGBT?A-RC-IGBT?is proposed,which utilizes the avalanche breakdown of the PN junction formed by the P⁺⁺collector and N⁺⁺region?field stop layer?on the backside to achieve reverse conducting.Because there is no need to introduce N⁺collector region on the back,snapback phenomenon will not happen.At the same time,the backside photolithography process is avoided,so the manufacturing process is simple and the cost is lower.Although the reverse conduction voltage drop of the device is much larger than that of the Con-RC-IGBT,it has certain practical value in applications such as single-ended quasi-resonant converter with asymmetric forward and reverse conduction time.