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

Abstract

Surge voltage at insulated gate bipolar transistor turn-off switching was analyzed with dependence on cell design parameters. Although drift layer thinning is effective in improving trade-off characteristics between turn-off loss E off and on-state voltage V on, voltage surge is induced due to the quickly expanding depletion layer. Therefore, the surge voltage V surge has also a trade-off relationship with V on at the same E off condition. The origin of the voltage surge was analyzed using TCAD simulation, and the total amount of remaining holes in the drift layer during turn-off switching is a key factor for the V surge. A narrow mesa structure and thick buffer layer are effective for the improvement of trade-off characteristics between V surge and V on. However, the optimum buffer layer thickness depends on the voltage-class due to the speed for punch through.