The effect of ionizing radiation on the breakdown voltage of power MOSFETs

It is shown that the drain-source breakdown voltage of power MOSFETs depends strongly on the total dose of ionizing radiation to which the device has been exposed. For the n-channel MOSFETs investigated, the breakdown voltage after exposure is reduced from the unirradiated value. The cause for this is believed to be the trapping of radiation-generated charge in the field oxide and the generation of interface traps at the field oxide-silicon interface. It is also shown that the magnitude of the drain-source voltage applied to the device during irradiation has a pronounced effect on the total shift in breakdown voltage. The method of junction termination also has an effect on the total shift. It is noted that these influences occur because the electric field in the oxide during irradiation depends both on the applied drain-source voltage and on the method of junction termination.