Characteristic Research Of New Structural RC-IGBT And Freewheeling Diode

Reverse-Conducting Insulated Gate Bipolar Transistors?RC-IGBTs?realize the process integration of Insulated Gate Bipolar Transistors?IGBTs?and freewheeling diodes.Reverse conduction characteristics.RC-IGBT owns the forward and reverse conduction characteristics.Compared with conventional IGBT modules,RC-IGBTs reduce packaging costs and increase chip integration,which is a direction for the development of IGBT modules.However,there is a snapback during the forward conduction of the RC-IGBT,which results in a large difference in turn-on characteristics.Therefore,it is not suitable to use multiple chips in parallel,which limits the application of RC-IGBTs in high-voltage and high-power applications.At the same time,the fast soft recovery characteristics of freewheeling diodes in RC-IGBT chips also need to be further improved.In order to solve the above problems,this paper first makes an in-depth study of the static and dynamic characteristics of RC-IGBTs.Starting from the forward conduction mechanism of RC-IGBT,the causes of the voltage snapback phenomenon of RC-IGBT and the conditions to eliminate the voltage snapback phenomenon are analyzed.The influence of the field stop layer?FS layer?parameters,collector parameters,and N⁺short-circuit zone parameters on the forward and reverse conduction characteristics of the RC-IGBT is discussed,and the dynamic parameters of the RC-IGBT and IGBT are compared and analyzed.Second,in order to eliminate the phenomenon of RC-IGBT voltage snapback,two new improved structures have been proposed.One is a floating field stop-type RC-IGBT?FFS-RC-IGBT?.The field stop layer of the conventional RC-IGBT is moved upward to"float"in the N-drift region,and a P-type floating layer is implanted under the float N stop layer.The barrier formed between the floating FS layer and the P-type floating layer blocks the emitter electrons from entering the N⁺short-circuit region to suppress the return voltage.the device's snapback voltage is well suppressed and the switching time is shortened.The second is collector-isolated RC-IGBT?CI-RC-IGBT?.There is a P-type blocking region above the N⁺shorting region,and a Si₃N₄ isolation trench is introduced between the P⁺collector and the N⁺shorting region while embedding the FS layer in the N-drift region.The Si₃N₄ isolation trench in the CI-RC-IGBT structure separates the N⁺short-circuit region from the P⁺collector and effectively utilizes the embedded P-type blocking region to block the electrons generated by the emitter so that it cannot be discharged from the N⁺short-circuit region.Thus,the effect of suppressing the snapback voltage is played.With the introduction of a silicon nitride isolation trench and a P-blocking region,the collector-isolated RC-IGBT's snapback voltage is completely eliminated,and its blocking characteristics are slightly improved.Finally,an Asymmetric Anode and Cathode Extraction?AA-CE?diode is proposed for the fast soft recovery of freewheeling diodes in RC-IGBTs.Taking 600V/100A as an example,AA-CE free-wheeling diodes were designed and tested for tapeout.The forward voltage drop of the AA-CE diode,reverse recovery time,reverse blocking characteristics,and reverse recovery softness factor were tested.As a free-wheeling diode,the diode is packaged with an IGBT module of 600V/100A into an IGBT module for double-pulse testing.The research done in this article has a certain guiding effect in the design and improvement of RC-IGBT and freewheeling diode.