Structural properties of sputter-deposited CN_x/TiN multilayer films

CN_x/TiN multilayer films with different bilayer periods were produced by reactive unbalanced magnetron sputtering. Low-angle X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM) were employed to investigate the structural properties of these films including layer density, bilayer thickness, layer thickness variation, and interface roughness. The results showed that the density of TiN layers in different CN_x/TiN multilayers ranged from ∼4.3×10³ to 4.9×10³ kg/m³ with the CN_x density being around 2.1×10³-2.3×10³ kg/m³. The bilayer thicknesses of those multilayers are about, respectively, 2.2, 5.0, and 10.2 nm, with a variation of layer thickness being ∼0.2-0.3 nm for both TiN and CN_x layers due to the random characteristic of particle deposition. Analysis also revealed that for the multilayer with 5-nm-thick bilayer an initial system instability caused the bilayer thicknesses in the early growth time (∼4.6 nm) to be less than those at the later stage of growth (∼5 nm). By incorporating three different interface roughness models into low-angle X-ray diffraction simulations, it was found the underlying interface roughness of CN_x/TiN multilayers increased with the bilayer number, and the roughness of three different multilayers was determined to be, respectively, about 1.1, 1.5, and 2.1 nm, showing an increasing trend with the bilayer thickness.