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Spectroscopic Measurements of the Production and the Transport of CH Radicals in a Methane Plasma Used for the CVD of a-C:H

Spatial and temporal variations of CH radicals in an rf discharge in methane for the deposition of amorphous carbon film were measured by optical emission spectroscopy and laser-induced fluorescence (LIF) spectroscopy. The temporal variation of CH emission from the excited A2Δ state suggested that the electron energy was deeply modulated by the rf field. The spatial distribution of CH in the ground X2Π state showed a broader profile than the time-averaged emission profile of CH(A2Δ), indicating the broader spatial production pattern for the CH(X2Π) and its diffusional transport. The absolute density of CH(X2Π) was also obtained, from which the flux of CH onto the substrate was estimated. The density and the spatial profile of CH were strongly affected by diluent Ar gas. These results were compared with a simulation and discussed in relation to the film deposition.