Thermal Breakdown Failure Mechanisms of IGBT Chips

As insulated gate bipolar transistors (IGBTs) become widely used in all kinds of power conversion systems, the demands of power converters to the IGBT's reliability turn to be more stringent. Thus, investigations of the IGBT's internal failure mechanism are very important to guarantee the improvements of device reliability and the optimizations of design and applications. Previous researches concentrate on the external factors of the device failures which are the failure modes. However, it lacks thorough studies of the internal mechanism which ultimately causes the device failure. In this paper, the analysis of the internal mechanism of thermal breakdown, has been presented based on the detailed investigations of the IGBT's structure and operation principles, applying the semiconductor physics theory. In addition, the existing misunderstandings on the IGBT's failure mechanism in the normal applications have been pointed out. Finally, experiments were designed to rebuild the failure process with the online monitoring through the high speed thermal infrared imager. This further verified the proposed conclusion and ascertained the internal failure mechanism of the IGBT chips.