PECVD synthesis, optical and mechanical properties of silicon carbon nitride films

SiCxNy thin films were synthesized at a temperature of 700 °C by the PECVD process, using trimethylphenylsilane C6H5Si(CH3)3 (TMPhS) and ammonia as a reactive mixture. The effect of NH3 dilution on the structure and chemical bonding of SiCxNy films was investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray analysis. The influence of deposition conditions on the transmittance, the optical band gap, the hardness and the Young's modulus of SiCxNy films was studied. It was shown that the chemical composition and the functional properties of the films are governed by the initial pressure ratio of NH3 to TMPhS. The variation of the ratio enables the film of different composition to be deposited, e.g. SiCx, SiCxNy and SiNy. It was shown that the films deposited from a reactive mixture with the highest ammonia dilution had a transmittance comparable to that of SiO2 and hardness of 23 GPa.