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    Electronics Friday Sessions
       Session EL-FrM

Paper EL-FrM8
Cu ECD: Modeling the Effects of Additives

Friday, November 2, 2001, 10:40 am, Room 124

Session: ULSI Metallization & Interconnects
Presenter: S. Sen, Rensselaer Polytechnic Institute
Authors: S. Sen, Rensselaer Polytechnic Institute
S. Soukane, Applied Materials
T.S. Cale, Rensselaer Polytechnic Institute
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Plating additives used in Cu ECD undergo complex reactions that are not well understood but are important to know for the optimization and control of these processes. Simulation results are presented on feature scale modeling of Cu ECD in the presence of additives, incorporating chemistry based models to describe the additive action. We consider an electrolyte bath with three species; cupric ions and two additives. One additive accelerates the copper deposition reaction and results in bump formation on the top and the second additive suppresses deposition at the feature mouth, resulting in more uniform deposition rates in the entire feature. The cupric ion reacts by a two-step charge transfer reaction described by Butler-Volmer kinetics. The accelerator kinetics is described following Moffat.@footnote 1@ The accelerator reacts catalytically with the cupric ions on the electrode enhancing the charge transfer reaction. Additionally the species coverage increases as the surface shrinks due to growth, increasing the deposition rate. The leveling agent adsorbs onto the electrode, occupying active sites and inhibiting copper deposition.@footnote 2@ It is used in the mass transfer limited regime, hence the inhibition is lower in the feature interior than at the top, resulting in more uniform deposition profiles. Feature scale simulations are done with the ECD module of EVOLVE,@footnote 3@ which has transient and steady state solvers for the governing diffusion-reaction equations, and allows inclusion of chemistry based models for the component reactions. @FootnoteText@ @footnte 1@T. P. Moffat, D. Wheeler, W. H. Huber and D. Josell, Electrochemical and Solid-State Letters, 4(4), pp. C26-C29, (2001). @footnote 2@S. Soukane and T. S. Cale, Proceedings of the Seventeenth International VLSI Multilevel Interconnections Conference (VMIC), Tom Wade, ed., IMIC, 2000, pp. 260-262. @footnote 3@EVOLVE is an extensible topography simulation framework. EVOLVE 5.0i was released in June 1999. Copyright 1990-2000, Timothy S. Cale.