Influence of nitrogen profile on electrical characteristics of furnace- or rapid thermally nitrided silicon dioxide films

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Abstract
Thin silicon dioxide films nitrided in N2O by rapid thermal processing (RTP) or in a classical furnace were investigated by x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and electrical measurements on metal-oxide-semiconductor capacitors. Differences between the two nitridation processes were observed and explained. In lightly nitrided films, nitrogen occupies two configurations. Nitrogen is bound to three silicon atoms with at least one in the substrate or all three in the oxide. In RTP-nitrided films, both of these species are confined to within 1.5 nm of the Si/SiO2 interface. In furnace-nitrided films, the first species is also located close to the interface whereas the second one fills most of the regrown oxide thickness. In furnace-grown films, which are more heavily nitrided, a third structure due to Si2=N–O is observed throughout the layer. The electrical characteristics are well correlated with the amount of nitrogen at the interface that is bound to Si atoms in the substrate.