The effect of near-interface network strain on proton trapping in SiO2

The buildup of positive charge during annealing in forming gas at 600 degre es C was compared for various types of Si/SiO2 interfaces. Our data suggest a correlation between the presence of stressed bonds in the SiO2 network n ear the Si/SiO2 interface, and the ratio of fixed vs, mobile positive charg e (protons) detected near the interface after performing a forming-gas-anne aling. We further propose that the presence-of these stressed bonds near th e interface is correlated with the oxygen deficiency at the interface and w ith 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 si gnificant decrease in the overall proton binding energy with increasing net work strain near the interface. These calculations support our model of mob ile proton generation at Si/SiO2 interfaces with large densities of stresse d bonds.