Fluorinated amorphous carbon thin films: Analysis of the role of the plasma source frequency on the structural and optical properties

Abstract

Different types of fluorinated amorphous carbon (a-C:H:F) thin films were grown by CH4/CF4/Ar mixtures using a 13.56 MHz radio frequency (rf) and a 13.56 MHz rf −2.45 GHz microwave hybrid plasma source. The optical properties of films were carried out by ellipsometric measurement, while x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were exploited to study their structural and vibrational properties. XPS spectra showed that the fluorine incorporation increased with the CF4 partial pressure while fluorine-poorer films were deposited with the rf-microwave hybrid technique. Raman measurements also suggested that with increasing fluorine content, the film microstructure changed from diamond-like to polymer-like. The mechanism of the a-C:H:F refractive index dependency on the plasma source frequency is investigated in terms of the amount of fluorine incorporation in the films produced.