Void-free deposition for integrated circuit interconnect with polyethylene glycol (PEG) as the single additive has been developed based on the characteristics of the current-potential responses at an acid copper sulfate bath containing PEG and chloride ions (Cl-). Several electrochemical methods were employed, including chronopotentiometry, linear sweep voltammetry and cyclic voltammetry to study the effect of PEG molecular weight on adsorption behaviors and suppression ability of PEG. Field emission scanning electron microscopy was utilized for the characterization of microstructural evolution, related with the suppression ability. The filling capabilities were carried out using acid copper baths containing PEG at various molecular weights, ranging from 3200 to 20,000g mol(-1). Better filling capacity can be obtained as the molecular weight of PEG increases. (C) 2008 Elsevier B.V. All rights reserved.