Chemical Structure of Nitrogen Atoms in Thin-Film Nitrided Silicon Dioxide Formed on Silicon Substrate after Hydrogenation Reaction in Hydrofluoric Acid

Abstract

Hydrogenated structures on a nitrided silicon dioxide SiO(N) film, which had been thermally grown on Si(100) wafers in a NO atmosphere to contain 4 atomic percent of N atoms, were detected after the film was etched slightly in a dilute HF solution. The N atoms on the surface of the etched SiO(N) film were observed as N–H monohydride structures by infrared spectroscopy. The depth profile and chemical structure of the N atoms were deduced on the basis of the infrared absorption intensity and the frequency of N–H stretching vibrations. In the depth profile, the concentration of N atoms had a maximum, which was distant from the interface with the Si crystal and was within the film. The frequencies of the N–H stretching vibrations were from 3380–3390 cm-1 in the film and they shifted down to 3300 cm-1 at the interface. In the film, the N atoms were not directly bound to the O atoms, but instead were found to be connected to the O atoms through the Si atoms. At the interface, the secondary-bonded atoms of the N atoms changed from O atoms to Si atoms.