Experimental and numerical investigations on delayed short-circuit failure mode of single chip IGBT devices

This paper presents experimental and numerical investigations on the delayed failure mode of IGBT devices observed under short-circuit operations. For short-circuit energies lightly higher than a critical value, the default current may be successfully turned-off but a leakage current takes place leading to a thermal runaway and finally to a delayed failure. Numerical investigations have been carried out and a detailed analysis of the physical mechanisms occurring during the delayed failure mode is presented. We show that the classical short-circuit failure mode (energy limited) is a limit case of the delayed failure mode with zero delay time to failure. So, the analysis is extended to the energy limited case and give better understanding of the failure process of this last failure mode. An electro-thermal model including the device and the solder layer is presented as well as all leakage current components models like saturation, thermal and avalanche generation currents. A detailed description of the thermal runaway is given and main parameters influence on critical energy value are presented, especially, case temperature and solder layer thickness. Finally, numerical results allow to show that the critical energy which separates two failure modes corresponds to a threshold temperature of about 650 °C in the vicinity of the junction location which seems to be independent of test conditions.