Electroless Cu deposition on a TiN barrier in a CuSO4-HF solution by separated electrodes of a Si wafer and a TiN/Ti/SiO2/Si substrate has been studied. In this electroless Cu plating method, two substrates are fixed on a base made by polystyrene without an external circuit. During plating the Si wafer is oxidized by hydrofluoric acid and releases free electrons; F- ions transmit the free electrons to the TiN/Ti/SiO2/Si substrate, and Cu2+ ions accept the electrons and then directly deposit them on the TiN surface. The morphology, surface coverage, average grain size, crystallography, and adhesion of the as-deposited Cu films on the TiN surface are related to the distance between the two substrates, bath temperature, and concentration of HF and CuSO4. During the plating, Cu is also deposited on the Si wafer and the properties of the Cu films on the Si wafer are discussed in the paper as well. The effect of HF on the TiN barrier in this electroless Cu deposition method is examined by X-ray photoelectron spectroscopy. (c) 2005 The Electrochemical Society. All rights reserved.