Electroless plating of copper via a Sn-free process on dielectric SiLK surface modified by UV-induced graft copolymerization with 4-vinylpyridine and 1-vinylimidazole

Abstract

Surface modification of Ar plasma-pretreated SiLK film coating on a (100)-oriented silicon wafer (SiLK-Si substrate) via UV-induced graft copolymerization with 4-vinylpyridine (the 4VP-g-SiLK-Si surface) or 1-vinylimidazole (the VIDz-g-SiLK-Si surface) was carried out to promote the adhesion with the electrolessly deposited copper. The surface composition of the graftcopolymerized SiLK-Si substrates was characterized by X-ray photoelectron spectroscopy. The topography of the 4VP-g-SiLK-Si and VIDz-g-SiLK-Si surfaces was investigated by atomic force microscopy. The 4VP-g-SiLK-Si and VIDz-g-SiLK-Si surfaces could be activated by PdCl2 in the absence of prior sensitization by SnCl2 (the Sn-free activation process) for the subsequent electroless deposition of copper. The 180°-peel adhesion strength of the electrolessly deposited copper on the 4VP-g-SiLK-Si and VIDz-g-SiLK-Si surfaces reaches about 6 and 5 N/cm, respectively. These adhesion strength values were much higher than those of the electrolessly deposited copper on the pristine and Ar plasma-treated SiLK-Si surfaces. The strong adhesion of the electrolessly deposited copper to the VIDz-g-SiLK-Si and 4VP-g-SiLK-Si surfaces was attributed to the synergistic effect of the strong interactior, between the pyridine or imidazole functional groups of the grafted polymers with copper atoms, the spatial distribution of the graft chains on the SiLK surface and into the metal matrix, and the fact that the graft chains were covalently tethered on the SiLK surface. © 2002 The Electrochemical Society. All rights reserved.