Synthesis and characterization of CN_x/TiN multilayers on Si(100) substrates

CN_x/TiN multilayer coatings were deposited onto Si(100) substrates by using the reactive closed-field unbalanced magnetron sputtering method. Different bilayer thicknesses (B_T) were attained by varying the substrate rotation speed during the deposition process. The focus of this work was a collective investigation of the bonding states and structure of the multilayer by means of X-ray photoelectron spectroscopy (XPS), high-angle X-ray diffraction (XRD), and low-angle X-ray scattering (LXRD). The characteristic of the layer was also confirmed by transmission electron microscopy (TEM), root-mean-square (RMS) surface roughness by atomic force microscopy (AFM). Chemical states such as TiN, TiO₂, and TiC exist in the TiN layer. The CN_x layer consisted of C, N and Ti in which N is bonded with C in the forms of C - N and C = N. The RMS surface roughness of the multilayers significantly varied with the substrate rotation speed. The RMS surface roughness was between 0.7 and 1.4 nm. The hardness of CN_x/TiN multilayer was highly dependent on their bilayer thickness. This multi-layer structure demonstrated an enhanced microhardness with decreasing bilayer thickness. It is found that for smaller bilayer thicknesses, the microhardness reproducibly achieved is as high as ∼50 GPa. In addition, stress measurement on the CN_x/TiN multilayer is also conducted. The internal (compressive) stress is associated with the hardness of the multilayer. For the maximum hardness the stress is found to be ∼7.7 GPa. Moreover, pin-on disc test under dry condition showed low friction coefficient (0.11).