Superconformal electrodeposition of copper

A model of superconformal electrodeposition is presented based on a local g rowth velocity that is proportional to coverage of a catalytic species at t he metal/electrolyte interface. The catalyst accumulates at the interface t hrough reaction with the electrolyte. More importantly, if the concentratio n of the catalyst precursor in the electrolyte is dilute, then surface cove rage within small features can change far more rapidly due to changing inte rface area. In such a case, the catalyst effectively floats on the interfac e during deposition, with changes in coverage coupled to alterations in arc -length of the moving surface. The local coverage therefore increases durin g conformal growth on a concave surface, resulting in a corresponding incre ase in the local deposition rate. The opposite is true for a convex surface . The model is supported by experiments and simulations of superconformal c opper deposition in 350-100 nm wide features. The model also has significan t implications for understanding the influence of adsorbates on the evoluti on of surface roughness during electrodeposition. (C) 2001 The Electrochemi cal Society.