Growth behavior of copper on TiN and TaN diffusion barriers according to the compositional change of copper-citrate (Cu-Cit) complex baths was studied in seedless copper electrochemical deposition. The peak potentials of cyclic voltammograms in the forward potential sweep were dependent on the concentration ratio of Cu2+ and Cit(3-) in the Cu-Cit baths. For the bath of [Cu2+]/[Cit(3-)]=1, when one-step deposition of copper was performed at a peak potential for competitive reduction of both Cu2+ and CuCit(-) ions, the 3D island growth of copper including lamella-like structure was shown. A peak for Cu2+ reduction and a peak for CuCit(-) reduction existed separately for the bath of [Cu2+]/[Cit(3-)]=2. Two-step deposition of copper in this bath gave birth to the 3D island plus layer-by-layer growth of copper. Interfacial adhesion between copper and TaN was measured as 12 and 34 J m(-2), respectively, for both deposition conditions. The electrical resistivity of copper films grown by two-step deposition was lower than that by one-step deposition for the same thickness. (c) 2007 The Electrochemical Society.