Plasma graft copolymerization of 4-vinylpyridine on dense and porous SiLK for electroless plating of copper and for retardation of copper diffusion

Abstract

Argon plasma-pretreated dense and porous SiLK films coated on Si(100) wafers (Si-SiLK wafers) were subjected to plasma graft polymerization of 4-vinylpyridine (4VP). X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results revealed that the pyridine functional groups of the plasma graft-polymerized 4VP (pp4VP) could be retained to a large extent under certain grow discharge conditions. The topography of the pp4VP grafted Si-SiLK (Si-SiLK-g-pp4VP) surface was studied by atomic force microscopy. The preserved pyridine groups were used as the chemisorption sites for the palladium complexes (without prior sensitization by SnCl2) to catalyze the electroless deposition of copper. Rutherford backscattering spectrometry and transmission electron microscopy were employed to investigate the extent of copper diffusion into the pristine and graft-modified Si-SiLK substrates after thermal annealing. The grafted pp4VP layer on the dense and porous Si-SiLK surface served effectively as (i) a sensitization layer for the electroless plating of copper, (ii) an adhesion promotion layer for the electrolessly deposited copper, and (iii) a diffusion barrier for the electrolessly deposited copper. These functionalities arose from strong interactions of the metal ions and atoms with the pyridine moieties of the grafted pp4VP layer. © 2005 The Electrochemical Society. All rights reserved.