Texture of Ru columns grown by oblique angle sputter deposition

Abstract

Ru films were sputter deposited on native oxide p-Si(100) substrates under normal incidence and oblique angle incidence with and without substrate rotation. We characterized the crystalline texture and morphology of the Ru films by x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. For the case of normal incidence, a smooth, uniform surface layer was observed, and pole figure analysis showed coexisting {101¯0}, {0002}, and {101¯1} normally oriented textures. For oblique angle incidence, we found that the films grown by uniform substrate rotation consist of isolated, vertical columnar structures with a clear pyramidal-shaped apex and display a normal {101¯0} fiber texture. Individual vertical columns were found to possess a single-crystal structure. In comparison, Ru films grown without substrate rotation possess a slanted columnar structure. They mainly show a tilted {101¯1}{101¯0} two-orientation (II-O) texture, with non-negligible {101¯0}{112¯0} and {0002} {112¯0} II-O textures as well. The formation of textures under oblique angle deposition was ascribed to the competition between crystalline planes having different vertical growth rates, where the planes associated with a higher rate survive from the shadowing effects. We argue that the vertical growth rate is determined by the atom mobility. Under substrate rotation this mobility is correlated with the overall atomic roughness of the crystalline planes. For a fixed substrate the adatom mobility exhibits anisotropic behavior, which is reflected in the biased diffusion.