TUNGSTEN AND TUNGSTEN-CARBON THIN-FILMS DEPOSITED BY MAGNETRON SPUTTERING

Tungsten and tungsten-carbon thin films have been produced from a W target sputtered in argon and argon-methane mixtures, respectively. The deposition rate of W films was measured as a function of the sputtering power and argon pressure varying in the range of 0.3-3 Pa. The crystallographic structure and composition of W films deposited on silicon and carbon substrates were investigated by x-ray diffraction and Rutherford backscattering spectroscopy. The electrical resistivity of the W films was minimum (12 muOMEGA cm) when the internal stresses in the films were negligible. The carbon concentration in the W-C films determined by nuclear reaction analyses and Rutherford backscattering spectroscopy was varied from 10 to 95 at. % with increasing CH4 content in the gas phase. The crystallographic structure of the W-C films was found to be dependent on the carbon concentration. Below 25 at. % of carbon, the structure of the W-C films was that of the cubic alpha-W phase with a dilated lattice parameter. For higher carbon concentrations, the bcc alpha-W phase disappeared and the structure was that of the nonstoichiometric cubic beta-WC1-x, phase. The structure of W-C films with a carbon content greater than 65 at. % was nearly amorphous. Internal stresses and electrical resistivity of W-C films were determined as functions of the carbon concentration. The experimental parameters suitable to produce W and W-C films with low resistivities and reduced internal stress level are reported in this article.