Investigation of inductively coupled Ar and CH4/Ar plasmas and the effect of ion energy on DLC film properties

Abstract

Gas-phase and surface analysis techniques were utilized to investigate the effects of gas-phase species on plasma deposited diamond-like carbon (DLC) thin films. A vacuum system was built to perform Langmuir probe and energy analysis-based mass spectrometry measurements to characterize the gas-phase of low pressure, 13.56 MHz inductively coupled plasma molecular beams. Low-energy peaks contributed significantly to the total area of the ion energy distributions (IEDs) measured for Ar+ in Ar and CH4/Ar plasmas. In contrast, for all other ions in these systems, the low-energy peaks had a lower contribution to the IEDs as a result of the low probability of energy exchange via ion–neutral collisions. Hydrogenated DLC films were deposited on silicon wafers at different substrate potentials to determine the effect of ion bombardment on film properties. Films were characterized via Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and nanoindentation measurements. The hydrogen content, surface roughness and deposition rate decreased, whereas the hardness of the films increased when a negative bias voltage was applied. These results demonstrate that ion energy has a significant effect on the composition and morphology of plasma deposited DLC films.