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

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.