Abstract
In this study, we proposed a standard procedure to measure the stress of polycrystalline Ti1-xZrxN thin films by using average X-ray strain (AXS) method. The objective was to narrow down the deviation of stress measurement to 10%, and to find the thickness limit in X-ray diffraction (XRD) and nanoindentation measurement. In addition, the effect of composition on the residual stress of Ti1-xZrxN thin films was also investigated. Eight Ti1-xZrxN thin film specimens with different compositions (x=0.25, 0.50, 0.75) and thicknesses were deposited on Si(100) by unbalanced magnetron sputtering. The strain of the thin films was measured by cos2αsin2ψ XRD method at multiple rotational angles (). The Young’s modulus of Ti1-xZrxN thin films was determined by nanoindentation. The AXS can be obtained from the slope of strain vs. cos2αsin2ψ plot. To verify stress of the thin films, the stress measured by combining AXS and nanoindentation was compared with the stress measured by laser curvature method and the deviation was assessed. The results showed that the compressive stress ranged from 2.69 to 5.10 GPa, and reached a maximum for Ti0.25Zr0.75N. The compressive stress of the Ti0.5Zr0.5N specimens decreased with increasing thickness probably due to the decrease of lattice defects. The different compositions in Ti1-xZrxN induce the asymmetrical variation of residual stress. The asymmetrical behavior in residual stress may be due to the difference in atomic size between Ti atoms in ZrN lattice and Zr atoms in TiN lattice. In this study, the deviation of XRD stress measurement was successfully decreased to 9.2%. The thickness limit of AXS measurement in Ti0.5Zr0.5N thin films was smaller than 200 nm, and the thickness limit of nanoindentation was about 600nm. By combining AXS and stress obtained by laser curvature method, the average effective X-ray elastic constant (AEXEC) could be determined for film thickness down to 200 nm.