Local structural analysis of a-SiCx:H films formed by decomposition of tetramethylsilane in microwave discharge flow of Ar

Hydrogenated amorphous silicon carbide (a-SiCx:H) films were prepared by the decomposition of tetramethylsilane (TMS) with microwave discharge flow of Ar. When radio-frequency (RF) bias voltage (− VRF) was applied to the substrate, the film hardness increased as (2.39 ± 1.12)–(9.15 ± 0.55) GPa for − VRF = 0–100 V. The a-SiCx:H films prepared under various − VRF conditions were analyzed by the carbon-K near edge X-ray absorption fine structure (NEXAFS), by the elastic recoil detection analysis (ERDA), and by the X-ray photoelectron spectroscopy (XPS). From a quantitative analysis of NEXAFS, the sp2/(sp2+ sp3) ratios of C atoms were evaluated as 67.9 ± 2.0, 55.4 ± 2.7, and 51.7 ± 0.7% for − VRF = 0, 60, and 100 V, respectively. From ERDA, hydrogen content of the film prepared under the condition of − VRF = 100 V was found to decrease 28% comparing with that under − VRF = 0 V. It is suggested that the cause of the increase of the film hardness when applying − VRF is predominantly the growth of the sp3-hybridized structure of C atoms accompanied by the decrease of hydrogen terminations.

Research Highlights
► a-SiCx:H films were prepared by the decomposition of tetramethylsilane with microwave discharge flow of Ar.
► H content and local structure around C atoms were studied with ERDA and C-K NEXAFS. They were prepared under various substrate RF bias voltages.
► Good correspondences were shown among these observations and the film hardness.
► It was suggested that the local structures around C atoms and hydrogen content may be important to control the film hardness