The work is devoted to relationships between structural, electro-physical and diffusion barrier properties of W-Ti-N thin films, prepared by reactive dc magnetron sputtering from W-Ti (30 at.%) target in Ar-N2 gas mixture. A dc power density of 1.7 W/cm2 was applied to the target and the partial pressure of nitrogen was varied from 0 to 3.5x10-3 mbar at a total gas pressure of 5x10-3 mbar.
Phase composition and crystallite size were studied using X-ray diffraction method (Philips X'Pert MPD diffractometer with CuKα1 radiation, equipped with a Johansson monochromator and a linear semiconductor strip detector). Surface morphology and root-mean square (RMS) roughness was examined using atomic force microscopy (NanoScope IIIa Dimension 3000 TM). The conductivity, stress and composition of W-Ti-N films were investigated using four-point probe sheet resistance measurements, stress measurement optical system and Rutherford backscattering spectrometry.
About ten layered samples were studied differing by nitrogen partial pressure applied during deposition. With increasing nitrogen partial pressure, the deposition rates decreased, what may be explained by lower efficiency of the nitrogen atoms with regard to argon atoms. Between the values of pN2 = 0.2 and 0.5x10-3 mbar, the deposition rate drops more steeply, which is indicative of changes in the sputtering mode (transition from a metallic to a nitride target), as well as in the film structure (from amorphous to polycrystalline films).
The resistivity of pure W88Ti22 film was 100 μΩcm and rose slowly up to 365 μΩcm for the ternary W42Ti12N46 film. When the nitrogen partial pressure reaches pN2 = 3.5x10-3 mbar, the resistivity of W34Ti11N55 film is 850 μΩcm, which may be attributed to the reduction in crystalline size.