Fluorine-containing amorphous hydrogenated carbon films

Abstract

Films were produced from trifluorotoluenc/hydrogen (TFT/H 2) and trifluorotoluene/tetrafluoromethane (TFT/CF 4) mixtures by plasma-enhanced chemical vapour deposition (PECVD) in a vacuum system fed with RF power. Actinometric optical emission spectroscopy was used to determine the trends in the plasma concentration [H] of the species H as a function of the proportion of the comonomer (H 2 or CF 4) in the plasma feed. Also, the plasma concentration of the species CF 2, [CF 2], was measured as a function of the proportion of CF 4 in the feed. The observed rise in [H] with increasing H 2 flows, and a rise in [CF 2] with increasing CF 4 flows, are attributed to the increased supply of H and CF 2 units, respectively, to the discharge. On the other hand, an observed rise in [H] with increasing CF 4 flows implies increased gas-phase reactions involving the comonomer or plasma/polymer-surface reactions. X-ray photoelectron spectroscopy (XPS) of the films deposited at various proportions of H 2 and CF 4 indicates the presence of CH n, CH−CF, C=0, CF and CF 2 groups. The degree of fluorination of the films decreases as the proportion of H 2 in the feed is increased and rises with increasing proportions of CF 4.