Research Of Snapback Effect And Trade-off Property Based On RC-IGBT

Power semiconductor device is the key component of the electric equipment,and it is also the essential device of the power electric systems,which are widely applied in the converter and control circuit field.The IGBT is called the heart of modern power electronic converter,which acts as the dominant role of power semiconductor device.In recent years,the IGBT devices are developing towards higher power density,greater working temperature and reverse conduction function.Consequently,the reverse conducting IGBT(RC-IGBT)is proposed and widely investigated.However,there is a current mutation when the forward conduction changes from unipolar to bipolar mode due to the short effect of the N-collector for the conventional RC-IGBT,then the Snapback is observed.The reliability problems such as uneven system current and temperature imbalance are inevitably avoided when the device is applied in parallel circuit topology.In addition,the Trade-off relationship of key performance such as breakdown voltage,threshold voltage,and conduction voltage drop are needed to be researched.Based on the above problems,this thesis focus on the device structure and working principle of the RC-IGBT,and the electrical characteristics including the Snapback effect and Trade-off relationship are investigated by the TCAD MEDICI.For the Chapter ?,it is the theoretical foundation and technical foundation of the thesis.The theoretical model and physical mechanism of the Snapback effect are researched,and the equivalent resistance model is also proposed to analyze the physic mechanism and eliminate the Snapback of the RC-IGBT.The Chapter ? to Chapter ? are the physical mechanism and new structure innovation part of the thesis.Based on the physic mechanism of the conventional RC-IGBT in Chapter ?,three novel RC-IGBT devices are designed from different mechanism including the collector resistance distribution,carrier conductivity mode and the layout design.Additionally,the internal mechanism parameters such as electric field,potential distribution and impact ionization rate are researched.The results show that the novel devices can not only completely eliminate the Snapback effect,but also the superior Trade-off property is achieved for the forward conduction,reverse conduction and turn off.The Chapter ? is the experiment part including the reliability analysis of the thesis,and the key electrical characteristics of the device depending on the temperature is investigated.The temperature is set from 223 K to 423 K in the simulation and experiment,and the RC-IGBT samples are analyzed by the power device test system B1505 A,multi-probe test platform CASCADE,and programmable constant temperature furnace.Finally,the breakdown voltage,the threshold voltage,the forward conduction characteristics,and the reverse conduction characteristics are verified by the experimental data,the numerical simulation and the theoretical model.