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