Detection of localized UIS failure on IGBTs with the aid of lock-in thermography

IGBTs with embedded current monitors, i.e. realized by separating a small part of the main device emitter and using it as the current sense terminal, are currently used to integrate intelligent power modules (IPMs). In a previous paper [Breglio G, Irace A, Napoli E, Spirito P, Hamada K, Nishijima T, et al. Study of a failure mechanism during UIS switching of planar PT-IGBT with current sense cell. Microelectron Reliab 2007;47(9–11):1756–60] we have demonstrated how, during UIS switching in particular circuit configurations, the interplay between the sense-emitter cell and the rest of the device can lead to latch-up of the lateral p–n–p bipolar transistor and current focalization in the sense-emitter cell which finally causes device failure. In this paper, we show how the location of this very localized failure spot can be very accurately determined with the aid of a very sensitive lock-in thermography setup. The main advantage of this approach is the direct applicability to the failed device without the need of time consuming sample preparation as in other failure analysis (FA) techniques.