Nanostructured copper–carbon composite thin films produced by sputter deposition/microwave plasma-enhanced chemical vapor deposition dual process

Pure copper and copper–carbon composite films have been deposited on silicon substrates by sputtering of a copper target associated with microwave plasma-enhanced chemical vapor deposition (PECVD) process of carbon from argon–methane mixtures of various compositions. The composition of films determined by Rutherford backscattering spectroscopy (RBS), the crystallographic structure identified by X-ray diffraction (XRD) techniques, the deposition rate deduced from the film thickness, and the electrical resistivity of films obtained by four point probe measurements were investigated as functions of the methane concentration in the argon–methane gas phase. Copper–carbon composite films containing 20–75 at.% of carbon were produced as the CH4 concentration was varied from 10% to 100%. A large increase (from 25 to 60 at.%) in carbon content in the films was observed as the CH4 concentration in the gas phase increased from 60% to 70%. These composite films consisted of polycrystalline copper and amorphous carbon phase. The copper crystallite size was in the range 15–30 nm and less than 5 nm for a carbon content in Cu–C films ranging from 20 to 25 at.% and from 60 to 75 at.%, respectively. The electrical resistivity of Cu–C films containing 20–25 at.% of carbon was approximately 2.5 μΩ cm whereas the resistivity value can reach 107 μΩ cm for films containing 60–75 at.% of carbon. A large variation of grain size and electrical resistivity of nanostructured Cu–C composite thin films was noticed as the CH4 concentration in the gas phase was varied from 60% to 70%.