Experimental and numerical investigation on MOSFET's failure during reverse recovery of its internal diode

The failure of the power MOSFET during the reverse-recovery of its intrinsic body-source diode used as a fly-back element in a half-bridge configuration has been investigated, The experimental Waveforms have been studied based on the analysis carried out by a mixed device and circuit simulator, According to the test conditions, it is shown that during the diode reverse recovery either a carrier current or a displacement current contribute to the activation of the parasitic BJT, which may cause the failure of MOSFET's. Among the parasitic elements inherent in the MOSFET structure, the capacitance associated to the gate oxide and the resistance of the polysilicon gate are shown to play a relevant role in the activation of the parasitic BJT due to a displacement current. The activation of the BJT due to carrier current, on the other side, is essentially dependent upon the resistances of the distributed base and of the body-source contact.