Effect of a Ta-Si-N diffusion barrier on the texture formation in thin Cu films

Abstract

Analyzing pole figures obtained by x-ray diffraction experiments, quantitative texture analyses are carried out on 50 nm thick Cu films sputter-deposited on oxidized Si substrates and on Ta-Si-N diffusion barrier films of various compositions. To explain the observed Cu texture formation during layer deposition, a model of two-dimensional grain growth in thin films is applied. In the case of silicon oxide substrates, a ⟨111⟩ Cu fiber texture component resulting from the minimization of the surface and interface energy is observed, in addition to a ⟨100⟩ component resulting from the minimization of the strain energy. For Cu films deposited onto Ta-Si-N diffusion barriers, preferred growth occurs only for ⟨111⟩-oriented Cu grains and their twins. The volume fractions of both components decrease with increasing N content of the diffusion barrier. Annealing of the Cu films at Tan=600 °C results in a strengthening and a sharpening of the ⟨111⟩ component. Hence, both the chemical composition of the underlayer as well as a postdeposition anneal are observed to have a significant impact on the texture of thin Cu films.