A structural study of organo-silicon polymeric thin films deposited by remote microwave plasma enhanced chemical vapour deposition

SiOxCyHz thin films with different Si/C and Si/O ratios have been prepared by plasma enhanced chemical vapour deposition, using (CH3)3SiCl as precursor and oxygen as plasma gas. Thin films with compositions ranging from SiO2:H to SiO2C4.7H7 were prepared by varying the oxygen to precursor ratio. The stoichiometry and structure of the films were determined by Fourier-transform infrared spectroscopy, Rutherford backscattering spectrometry, electron recoil detection analysis, X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy at the Si K edge. It has been shown that in all the films there are bonding structures of the type SiC and/or SiOC, besides a basic SiOSi skeleton. The preservation of this SiOSi structure for a so wide range of C content in the film is a key feature of the synthesised films. The optical properties of the films were also investigated by spectroscopic ellipsometry. It has been found that the refractive index increases with the carbon content in the films. The films were transparent in the visible although they presented a high absorption in the ultraviolet region that increases with the C content.