Research On Snapback Phenomenon And New Structure Of High-Voltage RC-IGBT

RC-IGBT is manufactured by integrating freewheeling diode and IGBT on the same silicon chip,so it has the ability of reverse conduction.Compared with the traditional IGBT module,RC-IGBT has the advantages of small size,low cost,and good stability,but it also has problems such as the snapback effect and complex performance tradeoffs.Thesis studies the snapback effect of RC-IGBT and the reverse recovery characteristics of the built-in diode of RC-IGBT,establishing the mathematical models.And a new RCIGBT structure is proposed,which solves the snapback effect and optimizes the reverse recovery loss of the build-in diode of RC-IGBT.The main research of the thesis is as follows,(1)The mathematical model for the snapback effect is deduced.Starting from the mathematical model of the snapback effect,the influence of the structural parameters of the device on the snapback effect is explored through simulation experiments.(2)The mathematical model for the reverse recovery loss of the build-in diode of RC-IGBT is deduced.Combined with the step-recovery model,the relationship between reverse recovery loss and p-type doping is obtained.The mathematical model between reverse recovery loss and device structure parameters is established.(3)A new RC-IGBT device structure with a partially shortened emitter(PSE RC-IGBT)is proposed.Only shortening the length of the P+ emitters on both sides of dummy trenches,so the peak of reverse recovery current and the reverse recovery loss of the build-in diode can be decreased without deteriorating the IGBT characteristics.Furthermore,using TCAD simulates the characteristics of PSE RC-IGBT,and the results show that the reverse recovery loss of the build-in diode is decreased by 19.9% than that of the conventional RC-IGBT.