A model of Radiation Induced Leakage Current (RILC) in ultra-thin gate oxides

An analytical model of Radiation Induced Leakage Current (RILC) has been de veloped for ultra-thin gate oxides submitted to high dose ionizing radiatio n. The model is based on the solution of the Schrodinger equation for a sim plified oxide band structure, where RTLC occurs through electron trap-assis ted tunneling. The values of the model parameters have been calibrated by c omparing the transmission probabilities obtained in this model with those o btained through the WKB method in the actual oxide band structure. No free fitting parameter has been introduced, and all physical constant values hav e been selected within the values found in literature. Different trap distr ibutions have been considered as candidates, but the comparison between sim ulated and experimental curves have indicated that a double gaussian distri bution in space and in energy grants the best fit of the experimental resul ts for different ionizing particles, oxide fields during irradiation, radia tion doses, and oxide thickness. Excellent matching has been found for both positive and negative RILC by using a single trap distribution. The trap d ensity linearly increases with the radiation dose and decreases with the ox ide field during irradiation. The trap distribution is spatially symmetrica l in the oxide, centered in the middle of the oxide thickness, and is not m odified as the cumulative dose increases.