Deposition and characterization of silicon carbon nitride films prepared by RF-PECVD with capacitive coupling

The goals of this work were to synthesize stoichiometric silicon carbon nitride (Si1.5C1.5N4) films using the RF-PECVD method and to characterize the deposited material. Gas mixtures, as opposed to an organic monomer, were chosen for reactants. Gas mixtures allow for varying the concentration of the elements needed for silicon carbon nitride synthesis and thereby optimizing the composition of the deposited films. It was found that amorphous hydrogenated silicon carbon nitride films having low oxygen contamination and comparable concentrations of silicon and carbon but deficient in nitrogen could be prepared by RF-PECVD from gas mixtures of silane, methane and nitrogen. The methane concentrations in the reactant gas mixture and flow rate or residence time were found to be important variables in achieving this objective. The chemical composition, structure and morphology of the films were studied by XPS, HFS, FTIR, XRD and AFM. These data suggested that silicon bonding in the films was analogous to that in silicon carbide and silicon nitride while carbon was bonded as carbide carbon and nitrogen as nitride nitrogen. The deposited films adhered well to silicon wafers, aluminum and mild steel with minimum pretreatment prior to deposition. The refractive index and density of representative silicon carbon nitride films are also reported.