Electrodeposition of Copper on Oxidized Ruthenium

Abstract

Ruthenium is an alternative liner material for copper metallization. We report on the nucleation and growth of copper on ruthenium in acidified copper sulfate solution and explore the influence of the PEG-Cl-SPS additive system. We show that the physical vapor deposition ruthenium has an oxide layer approximately 1 nm thick. The additives and copper concentration have a relatively small influence on island density but a significant influence on the island morphology. Without additives, both randomly oriented hemispherical islands and disk-shaped islands with a (111) orientation are observed. The distribution of islands is dependent on potential. In the presence of additives, the islands are irregular in shape due to renucleation that becomes more pronounced at higher concentrations and lower overpotentials. Analysis of the island size distributions implies that nucleation is fast in comparison to growth. The island density is exponentially dependent on potential increasing from 107 cm-2 at low overpotentials to almost 1011 cm-2 at larger overpotentials. The distribution of islands at the surface is shown to be consistent with complete spatial randomness.