Effects of molybdenum, silver dopants and a titanium substrate layer on copper film metallization

Annealing of 100 nm-thick Cu, Cu(Mo) and Cu(Ag) films was carried out to investigate the effect of dopant atoms on the films. Molybdenum (Mo) and silver (Ag) were selected as immiscible dopants for out-diffusion studies. A thermally grown SiO2 layer and a sputtered Ti layer were used as substrates. The dopant and substrate effects were characterized in terms of surface morphology, resistivity, preferred orientation, and diffusional characteristics. The lowest observed resistivity was 2.32 μΩ · cm in the Cu(Ag) film, which was lower than that in a pure Cu film of the same thickness. Ag addition enhanced the surface morphology and thermal stability of the Cu(Ag) films. The highest thermal stability was obtained in the case of a Cu(Mo)/Ti film which maintained film integrity to 800°C. A Ti substrate enhanced Cu(111) texture growth. A highly oriented Cu(111)-texture was obtained in the Cu(Mo)/Ti films. Cu diffusion through the Ti layer was limited in the (111)-textured Cu(Mo)/Ti films, which showed good potential as a diffusion barrier.