Hydrogenated and nitrogenated amorphous carbon films, a-C:H and a-C:H:N, were elaborated by Plasma Enhanced Chemical Vapor Deposition (PECVD) in a dual Electron Cyclotron Resonance - Radio Frequency (ECR-RF) discharge of methane and/or nitrogen. The use of a low pressure plasma (2.6 mTorr) and a capacitive coupling of the substrate, separately from the electrical power of the ECR source, leads to reach new conditions of preparation. The ions and radicals fluxes, Φi and ΦR, determined respectively from the Langmuir probe measurements and the Mass Spectrometry (MS) give a ratio ΦR/Φi of order of 20. The CH3 radicals were identified and their concentration was measured from the technique of threshold ionization. It is shown that, even at low pressure, numerous ion-molecule reactions take place in the gas phase which explain the formation of major ions CH5+. and C2H5+.
The plasma-surface interaction is studied by in-situ kinetic ellipsometry and by ex-situ X-ray Photoelectron Spectroscopy (XPS) measurements of deposited films. The role of the impact energy of ions, during the growth of films, is studied by Ultra-Violet-Visible spectroscopic ellipsometry.
A new technique of deposition by alternating sequences of «C H4 deposition - treatment by N2, plasma » is described in this paper. The resulted a-C:H:N films are compared to those elaborated from CH4-N2 plasmas. The aim of the discussion on the presented results is to better understand the mechanism of the growth of amorphous carbon films by PECVD.