Nondestructive testing of power MOSFET's failures during reverse recovery of drain-source diode

The failure of power MOSFET during reverse recovery of its intrinsic drain-source diode is experimentally studied by means of a nondestructive tester. The analysis is based on the observation of the waveforms during the failure which shows the evidence of the activation of parasitic bipolar transistor. This paper advances the hypothesis that the failure mechanism is strictly related to how this transistor is being activated during reverse recovery. In particular, for higher values of dI/sub D//dt, the bipolar parasitic transistor on small area of the chip is activated at the early beginning voltage rise. Device failure is then caused by the second breakdown of this transistor which takes place during its turn-off.