Electroless copper plating using FeII as a reducing agent

Although the electroless plating method is known to be an effective method for obtaining fine wiring in particular, 1 mol hydrogen gas is generated during 1 mol Cu deposition, and voids are generated in the wiring when electroless Cu plating is applied to fine wiring. To avoid the hydrogen evolution, the possibility of performing electroless Cu plating was confirmed using an inexpensive Fe-II compound as a reducing agent. The bath contains CuSO4, FeSO4, NaCl, ethylenediamine, sodium citrate, polyethylene glycol (PEG), and 2,2'-bipyridine. Under optimal conditions, over 1.7 mum of copper deposit with a smooth surface was obtained after 3 h of plating, which did not contain iron as an impurity. The electrical resistivity of the copper film is about 3-4 muOmegacm corresponding to that of electroplated copper films. (C) 2003 Elsevier Ltd. All rights reserved.