The effect of near-interface network strain on proton trapping in SiO/sub 2/

The buildup of positive charge during annealing in forming gas at 600/spl deg/C was compared for various types of Si/SiO/sub 2/ interfaces. Our data suggest a correlation between the presence of stressed bonds in the SiO/sub 2/ network near the Si/SiO/sub 2/ interface, and the ratio of fixed vs. mobile positive charge (protons) detected near the interface after performing a forming-gas annealing. We further propose that the presence of these stressed bonds near the interface is correlated with the oxygen deficiency at the interface and with the confinement of the oxide due to the presence of a Si cover layer. A model based on first-principles quantum mechanical calculations shows a significant decrease in the overall proton binding energy with increasing network strain near the interface. These calculations support our model of mobile proton generation at Si/SiO/sub 2/ interfaces with large densities of stressed bonds.