Origins of Interface States and Oxide Charges Generated by Ionizing Radiation in Metal-Oxide-Silicon Structures.

摘要

Evidences are presented to support proposed models of interface states and oxide charges in silicon MOS structures and their interaction with ionizing radiation. Interface states arise from a random distribution of the trivalent silicon centers at the oxide-silicon interface which perturb the silicon conduction and valence band states into the silicon band gap to give the U-shaped surface state density spectra. The positive oxide charges are from both trivalent silicon donor centers and excess oxygen centers. The trivalent silicon centers can be readily neutralized by trace amount of water to form the Si-OH centers which are highly sensitive to ionizing radiation. The Si-OH bond can be broken by ionizing radiation via hole capture or secondary impact ionization. The OH(-) ions freed from the trivalent silicon bonds can readily drift in the high electric field in the oxide of a MOS structure. Process conditions for the generation and annealing of these centers are described. A study is made of the accuracy of interface state density spectra analysis using the high-frequency capacitance-voltage characteristics of MOS capacitors. Single and discrete interface state levels can be resolved by this method. (Author)