Generation phenomena of localized interface states induced by irradiation and post-irradiation annealing at the Si/SiO2 interface

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Abstract
The generation phenomena and mechanisms of localized interface states at the Si/SiO2 interface, induced by irradiation and post‐irradiation annealing, are investigated by using 60Co γ rays. In a low dose irradiation of less than 1×106 rad, localized interface states having a peak at about 0.2–0.25 eV above the Si midgap are generated. At a higher irradiation dose, a peak of localized interface states generated by a low dose irradiation is eliminated, and is confirmed to be replaced by a peak of localized interface states that bulge near the Si midgap. This phenomenon is difficult to explain by the water related breakage bond model, but can be explained by the Si—O weak bond stable state and the trivalent Si dangling bond caused by the breakage of the Si—O weak bond. In addition, post‐irradiation annealing generates localized interface states, having a steep peak in the Si band gap near the conduction band, which caused the peak of the localized interface states to move toward the conduction band. In order to elucidate the generation mechanism of such localized interface states, we have proposed an acceptor‐like trap center model that is generated in the oxide near the Si/SiO2 after hole detrapping and recombined with the interface electrons by means of direct tunneling. To investigate its features, we have also investigated the influence on the local oxidation of silicon isolation structure and the effect of Fowler–Nordheim hot‐electron injection after post‐irradiation annealing.