Influence of Oxide Thickness on Nucleation and Growth of Copper on Tantalum

Oxide layers can play an important role in determining the kinetics of nucleation and growth during electrodeposition. In this paper, we report on the influence of oxide thickness on the nucleation and growth of copper on tantalum. Anodic oxidation was used to grow Ta 2 O 5 films up to about 20 nm thick. Current-voltage curves for anodically oxidized tantalum films show features associated with the nucleation and growth of copper but no stripping peaks as expected for a rectifying oxide film. Current transients for deposition of copper follow the rate law for instantaneous nucleation followed by diffusion-limited growth, independent of oxide thickness; however, the island density decreases exponentially with oxide thickness.