Limits of strongly punch-through designed IGBTs

We will focus on the turn-off behavior of strongly punch-through designed field-stop IGBTs. Our numerical simulations with a monolithic multi-cell structure show that the appearance of current filaments may limit the safe operating area (SOA) of very thin devices with a high resistivity of base material [1]. A detailed analysis of current densities and electric field distributions gives insight into the mechanisms resulting in the formation of current filaments. The limit for a filament-free turn-off behavior can be found in the thickness-vs.-resistivity phase diagram. It could be shown that also other device parameters, such as field-stop and p-emitter design, highly influence susceptibility for the appearance of current filaments during the turn-off phase.