Destruction in the Active Part of an IGBT Chip Caused by Avalanche-Breakdown at the Edge Termination Structure

Simulations and measurements on IGBT chips with a VLD edge termination structure reveal a periodic sequence of sharp current peaks in the avalanche breakdown regime. These current peaks are caused by a current filamentation process initiated and sustained by the interplay between a dynamically modulated electric field and localized self-heating. This mechanism makes it possible that the IGBT chip is capable of withstanding large avalanche-currents for a certain short period of time. In devices with decreased thickness we observe a destruction mechanism occurring in the active part of the IGBT chip, which is caused by the excessive avalanche-current in the edge termination structure. Consequently, for the largest possible safe-operating area, the edge termination structure and the neighboring cells located in the active area of an IGBT chip have to be focussed on for design optimization.