Optical and Compositional Properties of Amorphous SixCyFz Films Prepared by Reactive Sputtering

Amorphous SixCyFz alloy thin films are prepared by reactive rf sputtering of silicon in ArCF4 gas mixture. Measurements of optical absorption coefficient, identification of chemical bonds by IR absorption spectroscopy, and the compositional analysis by EPMA are made as a function of the partial pressure of CF4 (R). It is found that the optical gap obtained from the absorption increases with increasing R. For films prepared under relatively lower value of R, the vibrating mode of chemical bond of CF2 species is found to be dominant, though the modes of SiF and SiF2 are also observed. With the increase of R, stretching mode of SiC becomes predominant and the results of EPMA support the increase of the density of this bond.