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

摘要

Chemical bonding states and depth profiles of nitrogen in radical nitrided silicon oxide film formed in Ar/N_2 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 Si_3≡N configuration, and the other unknown bonding state (termed N_(high)) is observed, whose peak energy shift is about +4.8 eV. The nitrogen atoms forming Si_3≡N configuration accumulate only at the film surface and those forming N_(high) configuration are distributed deeper in the films. The N_(high) bond is very weak because it is desorbed completely at low temperature (300-500℃). Although the nitrogen atoms forming N_(high) configuration are removed by post O_2-annealing, those forming Si_3≡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 N_(high) bond reach the film/ substrate interface and form Si_3≡N bond at the interface. Suppression of the generation of nitriding species forming N_(high) bond in the plasma is very important. It is clear that N_(high) bond is reduced using Ar/NH_3 plasma.