Deposition and characterization of nanocrystalline diamond films on mirror-polished Si substrate by biased enhanced microwave plasma chemical vapor deposition

Hard and smooth nanocrystalline diamond (NCD) thin films were deposited on polished silicon substrates by biased enhanced growth in microwave plasma chemical vapor deposition. The films deposited with varying the methane concentration and biasing voltage were characterized by Raman spectroscopy, nano-indenter, x-ray diffraction and atomic force microscopy. Stress in the films increases with decreasing methane concentration in the gas-phase and with increasing biasing. The adhesion between NCD film and Si substrate is very strong sustaining the compressive stress as high as 85 GPa. It was hypothesized that hydrogen content of the films and graphitic content of the films are responsible in generating stress. The hardness is well correlated with the Raman peak intensity ratio of NCD peak to G peak.