Texture of Cu and dilute binary Cu-alloy films: impact of annealing and solute content

Abstract

The impact of 11 alloying elements, namely Mg, Ti, In, Sn, Al, Ag, Co, Nb and B, at two nominal concentration of 1 and 3 at%, and Ir and W, at only a nominal concentration of 3 at%, on the evolution of texture of Cu was investigated. The behavior of the alloy films was compared with that for a pure Cu film. The films were electron beam evaporated onto oxidized Si wafers and had thicknesses in the range of 420–560 nm. Annealing was carried out at 3°C/s to 400°C, 650°C and 950°C. For the lowest annealing temperature, the samples were held isothermally for 5 h, while for the higher annealing temperatures, the samples were cooled immediately after reaching temperature. In all cases, annealing resulted in the strengthening of film texture. For most of the films, the 〈1 1 1〉 component either remained or became the strongest fiber component with the increase in annealing temperature. The interesting exceptions were the two Mg-containing films for which the 〈1 1 0〉 component was the strongest. Whereas in the as-deposited state all alloy films, except the nominally 3 at% Nb film, had weaker textures than pure Cu, certain combinations of alloy concentration and annealing conditions resulted in more strongly textured films when compared with pure Cu. For example, the most strongly textured film after the 400°C and 950°C anneals were, respectively, Cu(Ti) and Cu(Nb), both nominally 3 at%. Film texture was also related to grain growth for the 400°C-annealed films. The behavior of the alloy films is discussed in terms of the various driving and pinning forces for grain growth and texture evolution in thin films. No simple correlations of alloy film behavior with atom size, electronegativity or the binary alloy phase diagram were found.