Turn-off switching voltage surge analysis with dependence on IGBT cell design

Abstract

Surge voltage at IGBT turn-off switching was analyzed with dependence on cell design parameters. Although drift layer thinning is effective to improve trade-off characteristics between turn-off loss Eoff and on-state voltage Von, voltage surge is induced due to quick expanding depletion layer. Therefore, the surge voltage Vsurge has also trade-off relationship with the Von at the same Eoff condition. The origin of voltage surge was analyzed using TCAD simulation, and total amount of remained holes in the drift layer during turn-off switching is a key factor for the Vsurge. Narrow mesa structure and thick buffer layer are effective for improvement of trade-off characteristics between Vsurge and Von. However, the optimum buffer layer thickness depends on the voltage-class due to the speed for punch through.