Structural and electrical characteristics of W-N thin films prepared by reactive rf sputtering

The crystal structure, chemical bonding state, composition, and electrical resistivity of W-N films deposited by reactive rf sputtering are investigated by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry, and four-point probe. Using 150 W of sputtering power and 25% of N-2 partial flow rate, the deposition rate and resistivity of W-N films decrease with increasing negative substrate bias. When the substrate bias is set at -100 V, resistivity of W-N films increases while the deposition rate decreases with increasing N2 partial flow rate. W+W2N mix phase, W2N phase, and W2N+WN mix phase are obtained at 10%, 15%-25%, and 40% of N-2 partial flow rate, respectively. When the N-2 Partial flow rate is greater than 40%, the films become amorphous like. Nitrogen concentration in the W-N films increases continuously with increasing N-2 partial flow rate, and the W4f core-level electrons change gradually from metallic W bondings to WN bondings. By reducing the sputtering power to 50 W, we have found that film resistivity also rises with increasing N-2 partial flow rate but crystalline W2N phase can be obtained with 10%-50% of N-2 partial flow rate. The,connection between the process conditions, structural change and electrical resistivity of the sputtered W-N thin films is discussed. (C) 2003 American Vacuum Society.