Structural analysis of silicon oxynitride films deposited by PECVD

We have investigated the SiOxNy films obtained by plasma enhanced chemical vapor deposition (PECVD) technique at low temperature using nitrous oxide (N2O), nitrogen (N2) and silane (SiH4) as precursor gases. Controlling the gas flow ratio during film deposition, it was possible to vary the material stoichiometry from silicon dioxide to silicon nitride. The structure of the films was investigated by X-ray absorption near-edge spectroscopy (XANES) at the SiK, NK and OK edges, Rutherford backscattering spectroscopy (RBS) was utilized to characterize the material composition. The results show the possibility of obtaining a chemical composition varying continuously from SiO2 to Si3N4. The SiK edge absorption spectra indicate that the basic structural element of the network is a tetrahedron with a central Si atom connected to N and O, consistent with a random bonding model. Analysis at the NK edge shows the presence of two distinct edges, which are attributed to the different nitrogen neighborhoods in this material, nitrogen in a Si3N4 matrix and nitrogen substituting O in a SiO2 type matrix.