Failure mechanisms of IGBT's under short-circuit and clamped inductive switching stress

Application of insulated gate bipolar transistors (IGBT's) in high-power co nverters subjects them to high-transient electrical stress such as short-ci rcuit switching and turn off under clamped inductive load (CIL). Robustness of IGBT's under high-stress conditions is an important requirement. Due to package limitations and thermal parameters of the semiconductor, significa nt self-heating occurs under conditions of high-power dissipation, eventual ly leading to thermal breakdown of the device. The presence of a parasitic thyristor also affects the robustness of the device. In order to develop op timized IGBT's that can withstand high-circuit stress, it is important to f irst understand the mechanism of device failure under various stress condit ions. In this paper, failure mechanisms during short-circuit and clamped in ductive switching stress are investigated for latchup-free as wed as latchu p-prone punchthrough IGBT's, It is shown that short-circuit and clamped ind uctive switching cannot be considered equivalent in the evaluation of a de, ice safe operating area (SOA). The location of thermal failure of latchup-f ree punchthrough IGBT's is shown to be different for the two switching stre sses.