Electroless metallization of dielectric SiLK surfaces functionalized by viologen

Abstract

Surface functionalization of the Ar plasma-pretreated SiLK coating on (100)-oriented silicon wafer (SiLK-Si substrate) via graft modification with viologen (1,1′-substituted-4,4′-bipyridinium salt) was carried out. The method involved a two-step process whereby 4-vinylbenzyl chloride (VBC) was first graft copolymerized, via UV induction, on the Ar plasma-pretreated SiLK-Si substrate surface (the VBC-g-SiLK-Si surface). The benzyl chloride groups of the grafted VBC chains were subsequently coupled with viologen (the viologen-g-SiLK-Si surface). The surface composition and topography of the graft-functionalized SiLK-Si substrates were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. Pd(II) and Au(III) ions could be adsorbed onto the viologen-g-SiLK-Si surfaces and subsequently reduced to their respective metal atoms under UV irradiation. Electroless deposition of copper could be carried out effectively on the viologen-g-SiLK-Si surfaces with the photoreduced palladium metal. The 180°-peel adhesion strength of the electrolessly deposited copper with the viologen-g-SiLK-Si surface reached about 5 N/cm. Thus, not only did the surface grafted viologen molecules provide the chemisorption sites for the photoreduction of the palladium catalyst, they also served as adhesion promoters for the electrolessly deposited copper.