Abstract
Electroplated copper thin films have started to be applied to not only interconnections in printed wiring boards, but also thin film interconnections and TSV in semiconductor devices because of its low electric resistivity. However, the electric resistivity of the electroplated copper thin films was found to vary drastically comparing with those of the conventional bulk material. This was because that the electroplated copper thin films consisted of a lot of porous grain boundaries. Thus, annealing is necessary for improving the crystallographic quality of the films. However, it was also observed that stress-induced migration occurred in the annealed film after the annealing. Large voids and hillocks grew during the custody of the film even at room temperature without any application of current. It was also found that sulfur atoms segregated in the grown hillocks, though no sulfur atoms were found by EDX in the initial as-electroplated films or other area in the annealed films. Thus, the hillock formation in the annealed films was enhanced by the segregation of sulfur atoms.
