Electrical and optical properties of CH4/H2 RF plasmas for diamond-like thin film deposition

A study of the effect of the substrate bias potential on the electrical properties of CH4/H2 discharges used for depositing a-C:H thin films on polymeric substrates was performed. Accurate measurements of the rf power and impedance based on recording voltage and current waveforms were applied for the determination of the effect of substrate bias. In addition, spatially resolved emission spectroscopy was utilized for following the effect of bias on the spatial production of species. The results show an increase of the total discharge power consumption and the production of species with the bias voltage. It is shown that apart from modifying ion bombardment, substrate biasing leads at the same time to significant changes in the discharge structure and the density of film precursors.