Influence of plasma source frequency on composition and density of fluorinated amorphous carbon thin films

Different types of fluorinated amorphous carbon (a-C:H:F) thin films were g rown from CH4/CF4/Ar mixtures using a 13.56 MHz radiofrequency and a 13.56 MHz radiofrequency-2.45 GHz microwave hybrid plasma source. Comparison of X -ray photoelectron spectroscopy (XPS) and X-ray reflectivity (XRR) allowed us to determine the film hydrogen concentration, which depends on the plasm a source used, and showed that, independently of the plasma source employed , the fluorine incorporation occurs at the expenses of the hydrogen content . Moreover, films with lower fluorine content were deposited from the radio frequency-microwave hybrid technique. XRR measurements suggested that with increasing fluorine content, the film density changes indicating a phase tr ansition towards an open and less cross-linked structure. For a fixed gas m ixture composition, the deposition of less dense films grown by radiofreque ncy-microwave hybrid plasma source is probably associated to a different pl asma decomposition and lower energy of the bombarding species. (C) 2001 Els evier Science B.V. All rights reserved.