Characterization of hydrogenated amorphous Si_{1 − x}C_x films prepared at extremely high rates using very high frequency plasma at atmospheric pressure

Using the atmospheric pressure plasma chemical vapour deposition (CVD) technique, hydrogenated amorphous Si_{1 − x}C_x(a-Si_{1 − x}C_x : H) films were deposited at extremely high deposition rates. The films were prepared on Si(001) wafers at atmospheric pressure in a very high frequency (150 MHz) plasma of gas mixtures containing He, H₂, SiH₄ and CH₄. Film properties (structure, density and composition of a-Si_{1 − x}C_x : H) were studied as functions of CH₄ concentration and substrate temperature by transmission electron microscopy, Auger electron spectroscopy and infrared (IR) absorption spectroscopy. The relation between IR absorption spectra and chemical resistance of the films to 15% KOH solution was also investigated. The maximum deposition rate was 50 nm s⁻¹, which was more than ten times faster than that achieved by the conventional plasma CVD technique. It was found that when the CH₄ concentration was more than ten times higher than SiH₄, the interaction of CH₄ with SiH₄ was saturated, and carbon-rich a-Si_{1 − x}C_x : H films were formed. The density of the a-Si_{1 − x}C_x : H films was about 1.5 g cm⁻³, being less than half of the crystalline value of SiC. The a-Si_{1 − x}C_x : H film was not etched by a KOH solution, which was supported by IR analysis of the Si–C stretching vibration mode.