Pulse plating effect on stress of CoFe electrodeposits

Abstract

One of the difficulties associated with CoFe alloy deposition is the accumulated high tensile stress during deposition. The chemical reasons for this tensile stress include hydrogen incorporation due to hydrogen evolution and other impurity inclusions (e.g. O or S). The physical reasons of tensile stress include grain coalescence and lattice mismatch. Pulse plating has been shown in the literature to lower deposition stress for some electroplating systems. In this study, we investigated the effect of pulse plating on the stress of CoFe deposit. It was found out that pulse plating has minimal effect on the tensile stress of CoFe deposit from our IBM-Hitachi bath. We believe, the strong dependence of tensile stress on film composition is probably related to the potential increase of oxide/hydroxide inclusion in the film, and also is related to the refined grains with increased Fe content in the film.