Control of Nitrogen Depth Profile and Chemical Bonding State in Silicon Oxynitride Films Formed by Radical Nitridation

概要

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Chemical bonding states and depth profiles of nitrogen in radical nitrided silicon oxide film formed in Ar/N2 plasma excited by microwave has been investigated using X-ray photoelectron spectroscopy with HF step etching. The main chemical bonding state of nitrogen atom is Si3$\equiv$N configuration, and the other unknown bonding state (termed Nhigh) is observed, whose peak energy shift is about $+4.8$ eV. The nitrogen atoms forming Si3$\equiv$N configuration accumulate only at the film surface and those forming Nhigh configuration are distributed deeper in the films. The Nhigh bond is very weak because it is desorbed completely at low temperature (300–500°C). Although the nitrogen atoms forming Nhigh configuration are removed by post O2-annealing, those forming Si3$\equiv$N configuration migrate toward the film/substrate interface and they increase negative bias temperature instability. In the case of ultra thin film, nitriding species forming Nhigh bond reach the film/substrate interface and form Si3$\equiv$N bond at the interface. Suppression of the generation of nitriding species forming Nhigh bond in the plasma is very important. It is clear that Nhigh bond is reduced using Ar/NH3 plasma.
2005-10-15