Aluminium modification as indicator for current filaments under repetitive short-circuit in 650 V IGBTs

Abstract

In this work, an investigation of the top-side aluminium (Al) metallization modification, under repetitive short-circuit (SC) type I measurements, was carried out for 650 V IGBTs. These measurements were performed far beyond the safe operating area (SOA). The presence of current density filaments at the collector side during SC leads to a local temperature increase that reconstructs the emitter metallization and thus leads to a modification of the top Al surface. Here, the optical microscope was used to observe the change in emitter surface metallization. For 650 V IGBTs, a uniform Al modification pattern was observed irrespective of DC-link voltage and SC pulse width, which is in contrast to the results of 1200 V and 1700 V IGBTs. The computer-aided TCAD simulations were performed using a simplified front-side IGBT structure to understand the uniform Al modification on all the measured DC-link voltages.