A Co-based surface activator for electroless copper deposition

The activation of the dielectric surface by the colloidal solution of cobalt compounds was examined as a palladium-free activation process. The principle of the process is based on the deposition of a Co-based precursor film on the substrate surface to be metalized and on the reduction of the adsorbed cobalt particles. The reduction of the adsorbed cobalt oxy/hydroxy compounds was carried out by dipping the treated surface in an alkaline solution of borohydride both at room and elevated temperatures. It has been determined that the presence of a small amount of Cu2 + ions in the colloidal solution of cobalt compounds catalyzes the reduction of adsorbed Co-based precursor on the dielectric surface. Furthermore, the formed Co(0) seeds initiate electroless copper deposition. A continuous copper film was deposited on a glass sheet after its activation in a colloidal solution of cobalt compounds containing Cu2 + ions in contrast to that activated in the same solution without Cu2 + ions.