Optical emissions during plasma assisted chemical vapor deposition of diamond-like carbon films

The deposition of diamond-like carbon (DLC) films onto silicon wafers and polyethyleneterephthalate (PET) from methanehydrogen gas mixtures by plasma assisted chemical vapor deposition was investigated by optical emission spectroscopy. Film growth rates, crack formation, and average electron energy in the plasma were analyzed for various deposition conditions. The cracks in the DLC films deposited onto PET could be removed by increasing the hydrogen content in the gas mixture. No adjustment of ion energy, substrate temperature control, or addition of inert gas was necessary to avoid crack formation. In the commonly used range of bias voltage above 500 V, the intensity of the Hα line (656.3 nm) correlated well with the film deposition rate. The hydrogen peak intensity can be used for on-line, non-contact, instantaneous monitoring of the deposition rate.