Neutron irradiation effects on the breakdown voltage of power MOSFETs

The effect of neutron irradiation on power metal-oxide-semiconductor field effect transistors (power MOSFETs) breakdown voltage has been investigated. Power MOSFETs of both n- and p-channel with manufacturer's rated breakdown voltage between 100 to 500V were radiated up to accumulated neutron fluence of 5x10¹⁴ neutron/cm² Considerable increase in the breakdown voltages were observed in n-type MOSFETs after 10¹³ neutron/cm² and to p-type MOSFETs after 10¹² neutron/cm² The increase in breakdown voltages is due to the decrease in the mean free path caused by the neutron-irradiation-induced defects. The effect of positive trapped charge oxide and the termination structure to the breakdown voltage were considered. S-PISCES 2B device simulation was used to investigate the change in the b coefficient of Chynoweth's law that relates to the mean free path. Two empirical models are presented: one predicts the power MOSFET breakdown voltage after a certain amount of neutron fluence and the other considers the change in the b coefficient after some amount of neutron radiation to predict the change of breakdown voltage in a device simulation