Microstructure of sputter-deposited Al–Cu–Si films

Abstract

The microstructure of Al–3 wt. % Cu–1.5 wt. % Si and Al–0.5 wt. % Cu–1.0 wt. % Si films was analyzed with respect to crystal grain orientation and grain size distribution before and after annealing at 475 °C for 30 min. Films were deposited at various substrate temperatures using load-lock magnetron sputtering systems. Crystal orientation was analyzed by Kikuchi line patterns in 20 individual grains with respect to the substrate surface in each sample. Crystal grain size distributions were analyzed in high-Cu content films deposited under no-heat, 140 and 280 °C predeposition conditions. θ-CuAl2 precipitates were found in the as-deposited 280 °C sample at the triple points of the grain boundary. This sample showed the largest orientation dispersion. This phenomenon was not affected by annealing. Stable θ-phase precipitates formed at the grain boundaries during deposition were thought to impede the coalescence of grains resulting in a low degree of preferred orientation. Thin (0.1 μm) Al–0.5 wt. % Cu–1.0 wt. % Si films were deposited onto a MoSi2 underlayer at low substrate temperature and heated, followed by an additional 0.9 μm deposition. Samples treated in this manner exhibited a high degree of crystal orientation. It was found that crystal orientation in the initial stage of deposition is one of the major determinants in the final crystal orientation of films.