Electroless plating of copper and nickel via a Sn-free process on dielectric SiLK® surface

Electroless plating of copper and nickel via a one-step, Sn-free activation process was carried out effectively on the SiLK® coating on [100]-oriented silicon wafer (SiLK-Si substrate) modified by UV-induced surface graft copolymerization with several N-containing vinyl monomers, including 1-vinylilidazole (VIDz), 2-vinylpyridine (2VP), and 4-vinylpyridine (4VP). The chemical composition and topography of the graft-copolymerized SiLK-Si surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and AFM, respectively. The VIDz, 2VP, and 4VP graft-copolymerized SiLK-Si surfaces could be directly activated by PdCl₂ in the absence of prior sensitization by a tin compound, such as SnCl₂, (the Sn-free activation process) for the subsequent electroless deposition of copper and nickel. The Sn-free process involved initially the chemisorption of palladium, in the complex form, on the pyridine or imidazole group of the graft polymer. The 180°-peel adhesion strength of the electrolessly deposited copper and nickel with the VIDz, 2VP, and 4VP graft-copolymerized SiLK-Si surfaces were much higher than that of the electrolessly deposited copper and nickel with the pristine or the Ar plasma-treated SiLK-Si surfaces.