Surface Morphology Anisotropy and Stress Distribution Uniformity in Annealed Cu–W Films

Abstract

Copper-tungsten films were deposited on Si and Al2O3 substrates by magnetron sputtering and then in situ annealed in vacuum chamber at different temperatures. X-ray diffraction (XRD), scanning electron microscopy (SEM), and the polarization phase shift technique were used to characterize the microstructure, surface morphology, and residual stress of Cu–W films. The results indicated that there are two successive but distinctive stages of phase transition with the change of annealing temperatures. The evolution of surface morphology of Cu–W thin films shows a significant effect on the distribution of in-plane stresses. A strategy of integrating discrete wavelet transform and fractal geometry concepts was developed to analyze the anisotropy of surface structure of Cu–W thin films. The correlation between the anisotropy of surface morphology and the stress distribution of thin films was constructed. It is found that the stress distribution of the thin films is sensitive to the variations of the anisotropy of the surface structure with annealing temperature. The variation in the uniformity of in-plane stress distribution with the evolution of surface structure of thin films is independent of the choice of substrate materials.