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

CNx/TiN multilayer coatings were deposited onto Si(100) substrates by using the reactive closed-field unbalanced magnetron sputtering method. Different bilayer thicknesses (BT) 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 CNx layer consisted of C, N and Ti in which N is bonded with C in the forms of CN and CN. 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 CNx/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 CNx/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).