Investigations on ageing of IGBT transistors under repetitive short-circuits operations

In this paper, we describe experimental results concerning the ageing of 600 V IGBT under repetitive short circuit conditions. A critical energy, which is dependent on test conditions, has been already pointed out which separates two failure modes. The first one, with a cumulative degradation effect, requires some 104 short circuits to reach failure and the other one leads to the failure at the first short-circuit with a thermal runaway effect. This paper is focused on the first failure mode. In order to understand the ageing mechanism, 600 V IGBT dies have been packaged by Microsemi. The packaging has been made in order to make possible the characterisation of some degradations by the measurement of different electrical characteristics. In this paper, we will detail effects of device ageing on on-state voltage, short-circuit current and Al metallization degradation which leads to resistance increase.