Chemical and structural characterization of tungsten nitride (WNx) thin films synthesized via Gas Injection Magnetron Sputtering technique

Tungsten nitride (WN_x) thin films were synthesized on the silicon substrates by way of Gas Injection Magnetron Sputtering (GIMS) technique. Pulsed discharge conditions, generated in the GIMS method, were optimized to maintain the nitrogen partial pressure in the range of an order of 10^-3 to 10^-1 Pa by a periodical injection of gas doses. In this way, we could increase the mean free path of atomic species and preserve their kinetic energy, in comparison to the continuous sputtering techniques. Under these conditions we attempted to overcome the high nucleation barrier, common for β-W₂N phase synthesis. Here, different nucleation mechanisms of tungsten nitride thin films were examined by the scanning electron microscopy (SEM) and the atomic force microscopy (AFM). In terms of chemical bonding state investigations of WN_x films, we engaged the Raman spectroscopy measurements and the X-ray photoelectron spectroscopy (XPS). Furthermore, structural circumstances of tungsten nitrides were analyzed via X-ray diffraction (XRD) investigations. On a line of advanced applications issue, optical properties of these films were discussed on the basis of the spectroscopic ellipsometry results.