Infrared spectroscopic study on amorphous-carbon film deposition process by methylacetylene plasma

Plasma-enhanced chemical vapor deposition of amorphous carbon films with methylacetylene (CH3CCH) as a source gas is investigated with in situ and real-time infrared absorption spectroscopy. From the analysis of IR spectra, it is suggested that the adsorption species for the film deposition is considered to be ·CCH dissociated from the source molecule. sp2-C and sp3-CH2 species were generated in the deposited film. It is suggested that sp2-C in the film is transformed into sp3-CH2 during deposition by the adsorption of the plasma-generated species such as ·CCH and hydrogen. The methyl group of the source molecule acts as a hydrogen source in the plasma processing. The optical emission spectroscopic data support the generation of hydrogen in the plasma. The deposition rate in the case of methylacetylene plasma is suppressed compared with that in the case of acetylene plasma. The decreases in deposition rates are attributed to the hydrogen termination to surface dangling bonds and sp2-C bonds.