Characterization and modeling of electrical resistivity of sputtered tungsten films

Tungsten (W) thin films were deposited on a polyimide substrate by sputtering deposition inn pure argon plasma using a triode discharge system. The properties of these W films were investigated as functions of ions energy, argon pressure and film thickness. The composition and crystallographic and micrographic structures of W films were determined by Rutherford backscattering spectroscopy and x-ray diffraction techniques, respectively. Less than 6 at. % argon and metallic impurities (duc to the sputtering chamber configuration) was incorporated into the W films and different volume ratios of tungsten crystallographic phases (Wa and WP) were observed in the films. The electrical resistivity of Wa films was interpreted from impurity concentrations and the microstructure with a model based on electron scattering mechanisms at grain boundaries. It was shown that the electron reflectivity of the grain boundaries depends of the size of the grains. In order to evaluate the contribution of wp phase on the electrical resistivity of biphase W films, two models were proposed. The model of the averaged effect of the two phases leads to calculations that are in good agreement with experimental results and an intrinsic resistivity of WP phase is proposed to be close to 30 mu Omega cm. (C) 2001 American Vacuum Society.