Characteristics of copper/carbon and nickel/carbon composite films produced by microwave plasma-assisted deposition techniques from argon-methane gas mixtures

Copper/hydrogenated amorphous carbon (a-C:H) and nickel/a-C:H composite films have been deposited on Si substrates by combining sputter-deposition of metal and microwave plasma-assisted chemical vapor deposition of carbon from argon-methane mixtures of various concentrations. The deposition rate of films was found to vary between 10 and 25 nm/min depending on the CH4 concentration in the gas phase. The crystallographic structure of films was identified by X-ray diffraction (XRD) techniques. Diffraction peaks of the face-centered cubic (fcc) Cu phase were always detected in the XRD patterns of Cu/C films. Diffraction peaks of the fcc Ni phase appeared in the XRD patterns of Ni/C films deposited from gas mixtures containing less than 5% of CH4. Diffraction peaks of Ni and Ni3C phases were detectable in the XRD patterns of Ni/C films deposited from a gas phase containing 10% of CH4. For Ni/C films deposited with a CH4 concentration in the range 15-30%, the diffraction peaks in the XRD patterns were only ascribable to the Ni3C phase. Beyond 30% of CH4 in the gas phase, the structure of Ni/C films became progressively amorphous as the CH4 concentration increased. The grain size of Cu, Ni and Ni3C was determined as a function of the CH4 concentration. The residual stresses in Cu/C films were very low and independent of the CH4 concentration in the gas phase (or composition of films). For Ni-C films, the maximum value of compressive residual stresses was -0.6 GPa for films deposited with 20% of CH4 in the gas phase (or for Ni/C films containing pure Ni3C phase). The electrical resistivity of films determined by four point probe measurements as well as the hardness and elastic modulus of films deduced from nanoindentation measurements were studied as functions of the CH4 concentration in the gas phase. (C) 2004 Elsevier B.V. All rights reserved.