Parametric optimization of microhardness of diamond-like carbon films prepared by plasma enhanced chemical vapor deposition

Diamond-like amorphous carbon (DLC) thin films may have high hardness and low surface roughness depending on the deposition process parameters. A systematic parametric study of DLC films deposited by plasma enhanced chemical vapor deposition was conducted. Atomic force microscopy was applied to characterize the film microhardness and the surface mean roughness. The complex parametric effects of multiple deposition variables on process responses (microhardness and mean roughness) were examined using a face-centered central composite response surface experimental design. The directions, magnitudes, and significance of various main and interaction effects on the responses were studied. The response contour plots indicated that a combination of relatively high induction power and low deposition pressure at high bias voltage with low Ar dilution produces DLC films with high hardness. The parametric optimization agreed reasonably well with theoretical predictions. The design of experiments is demonstrated to be a powerful tool in exploration of the parameter space of the complex physical process of DLC film deposition.