Effects of proton radiation on capacitance/voltage characteristics of M.O.S. capacitors

The capacitance/bias-voltage characteristics of metal-oxide-semiconductor capacitors have been measured before and after irradiation with 25 MeV protons under various bombardment voltages applied to the gate during irradiation. The radiation-induced charge carriers are trapped in a localised region that extends approximately 300 Å into the oxide layer from the Si-SiO2 interface. The induced space-charge density shows an exponential dependence on the radiation dose and a linear dependence on the bombardment voltage. The effects are independent of the dose rate and appear to approach saturation for a dose of 3.5×1013 protons/cm2 with an effective bonbardment voltage of 5 V.