A Comparison of Ionizing Radiation Damage in MOSFETs from Cobalt-60 Gamma Rays, 0.5 TO 22 MeV Protons and 1 to 7 MeV Electrons

Non-radiation hardened P-channel and N-channel MOS transistors were irradiated with Co-60 gamma rays, 0.5 to 22 MeV protons, and 1 to 7 MeV electrons to determine the correlation between the gamma rays and the charged particles. Comparison of electrons to Co-60 showed that for equal absorbed doses, the damage produced was equivalent for all bias conditions. Under zero gate bias conditions, 2 to 22 MeV protons also produced damage in the test devices that was equivalent to Co-60. However, under bias conditions for high drain-source currents, the damage for protons below 22 MeV was always less than Co-60 (the lower the proton energy, the less the damage). The 0.5 MeV proton data showed poor correlation with Co-60 results. No dose-rate dependence was observed in the data. We conclude that, for the silicon MOS devices tested, the radiation damage produced by Co-60 provided a worst case simulation of high energy electron or proton damage.