A tapered shape of Cu pattern by electrodeposition through mask is preferred for fabricating metal line on thin-film transistors (TFTs). The influence of individual organic additive [polyethylene glycol (PEG), bis-3-sodiumsulfopropyl disulfide (SPS)] on the sidewall shape of the Cu pattern was identified. A compromising effect shows up when both PEG and SPS are added owing to the competition of the behavior of two different organic additives during Cu electrodeposition. Therefore, a method has been developed for the fabrication of copper pattern used in TFTs, which forms a tapered pattern in one single Cu deposition step. (c) 2006 The Electrochemical Society.