Structural analysis of amorphous hydrogenated silicon-carbon thin films from silane/propane mixtures

The structure of amorphous films prepared by rf plasma decomposition of silane/propane mixtures has been investigated by a combination of XPS, IR absorption and Bruggeman effective medium modelling of dielectric constant spectra. The influence of the deposition parameters was studied by statistical selection of a set of growth conditions and the closer investigation of a limited range of such conditions. The dominant deposition parameter is the gas mixture, although the substrate temperature is important in controlling hydrogen content at high substrate temperature. The carbon to silicon-plus-carbon contents are greater than 50 at.%, and hydrogen is bonded to both silicon and carbon. The films are predominantly carbon networks with silicon included, varying from a tetrahedral structure at low carbon content to polymeric at high carbon content, with a region that contains a significant amount of SiCH₃ and microvoids. There is only an insignificant graphitic component throughout the range. © 1994.