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Electrodeposition of Cu on Ru Barrier Layers for Damascene Processing



Thomas P. Moffat, Marlon L. Walker, P J. Chen, John E. Bonevich, William F. Egelhoff Jr., Lee J. Richter, Daniel Josell, C A. Witt, T Aaltonen, M Ritala, M Leskela


Superfilling of sub-micrometer trenches by direct copper electrodeposition onto PVD and ALD Ru barriers is demonstrated. The Cu nucleation and growth mode is found to be sensitive to the oxidation state of the Ru surface as well as the copper deposition parameters. Depending on the processing conditions, Cu deposition may or may not occur competitively with oxide reduction. Failure to remove the air-formed 3-D oxide film results in Volmber-Weber (island) growth and consequently poor trench filling as well as poor adhesion between Cy and Ru. In the case of thin resistive oxide-covered Ru seed-layers, the terminal effect further exacerbates the difficulties in obtaining a compact fully coalesced Cu film since the rate of Ru oxide reduction is decreased along with the density of Cu nuclei. In contrast, Cu deposition on a reduced oxide-free Ru surface results in more rapid coalescence involving the formation of a wetting Cu upd (underpotential deposition) layer. Electrochemical reduction of the oxidized Ru seed layer in a deaerated sulfuric acid solution, followed by rapid wet transfer to a Cu plating bath, enables robust superfilling of trenches and improved adhesion between Cu and Ru. Early film coalescence is favored by deposition at high (n~0.25 V) overpotentials.
Journal of the Electrochemical Society


copper, Cu upd on Ru, metallization, ruthenium, seedless superfill, superfilling


Moffat, T. , Walker, M. , Chen, P. , Bonevich, J. , Egelhoff, W. , Richter, L. , Josell, D. , Witt, C. , Aaltonen, T. , Ritala, M. and Leskela, M. (2005), Electrodeposition of Cu on Ru Barrier Layers for Damascene Processing, Journal of the Electrochemical Society, [online], (Accessed June 13, 2024)


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Created December 2, 2005, Updated February 17, 2017