Reduction of electron trapping in silicon dioxide by high-temperature nitrogen anneal

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Abstract
Electron trapping in silicon dioxide is reduced by nitrogen annealing in a furnace system with very low moisture content and special cooling techniques. The flatband voltage shift resulting from injected hot electrons is significantly reduced by the annealing together with the interface states generated. The trapped charge is laterally nonuniform when the oxide is not annealed. From photo I-V measurement, the density of electrons trapped in the bulk of the oxide is reduced by this treatment. The distribution of the trapped charge changes from a uniform distribution in the bulk for a 1-h anneal to a distorted U shape distribution, with a larger build-up on the aluminum-silicon dioxide side for a 17-h anneal. The density of trapped charge close to the silicon-silicon dioxide interface is reduced and thus the smaller flatband voltage shift. With the reduction in bulk change, interface state charge beomes important.