In conventional Cu electroplating, various additives are used to fill pattern without defects in patterned wafers. Pulse plating and electrochemical oxidation were used to deposit Cu without any additives. Defects such as voids and seams were generated if only pulse plating was carried out. Electrochemical oxidation was performed to remove Cu metal containing defects and to remain Cu species only at the bottom part of the trenches. Then, defect free Cu films could be obtained when Cu electroplating without additives was performed on the etched substrate. (c) 2006 The Electrochemical Society.