The Effects of Co60 Gamma Radiation on MOS Diodes

MOS diodes were fabricated on silicon substrates and exposed to Co60 gamma radiation. A change in both surface state density and oxide charge density was noted. Non-irradiation annealing studies were carried out to determine the nature of the oxide charge. It was deduced on the basis of annealing data that the oxide charge was due to mobile alkali ions. The radiation was seen to cause a decrease in the oxide charge density. A model attempting to explain this change was fabricated assuming Compton scattering in the oxide. The change in semiconductor surface charge density caused by the gamma irradiation was found producable or reversible by means of elevated temperature, applied bias annealing.