Surface modification of SiLK1 by graft copolymerization with 4-vinylpyridine for reduction in copper diffusion

Surface modification of Ar plasma-pretreated SiLK1 film coating on (1 0 0)-oriented single crystal silicon wafer (the SiLK– Si substrate) via UV-induced graft copolymerization with 4-vinylpyridine (the P4VP-g–SiLK–Si surface) was carried out to enhance the adhesion of the vacuum deposited copper. The composition and morphology of the P4VP-g–SiLK–Si surface were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The 1808-peel adhesion strength of the copper film with the P4VP-g–SiLK–Si surface was about 2.5 N/cm. This adhesion strength was much higher than that of the copper film with the pristine or the Ar plasma-treated SiLK–Si surface. The strong adhesion of evaporated copper with the P4VP-g–SiLK–Si surface was attributed to the strong interaction of the copper atoms with the pyridine groups. The extent of copper diffusion into the P4VP-g–SiLK–Si film at the annealing temperature of 300 8C, was investigated by timeof- flight secondary ion mass spectroscopy (ToF-SIMS) and compared to those of copper diffusion into the pristine and Ar plasma-treated SiLK–Si surfaces. The improved resistance of the P4VP-g–SiLK–Si surface to copper diffusion, probably arose from the strong interaction of the copper atoms with the grafted 4VP polymer. # 2003 Elsevier B.V. All rights reserved