Selective electroless plating of copper on (100)-oriented single crystal silicon surface modified by UV-induced coupling of 4-vinylpyridine with the H-terminated silicon

A Sn-free electroless plating process for producing patterned and adherent copper deposits on (100)-oriented single-crystal silicon substrates is described. Pristine and resist-patterned Si(100) substrates were etched, initially, by aqueous HF to produce the hydrogen-terminated silicon surfaces (H-Si(100) surfaces). The H-Si(100) surfaces were further functionalized by the UV-induced reactive coupling of 4-vinylpyridine (4VP). The composition and topography of the modified Si(100) surfaces were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The coupled 4VP layer exhibited good stability in boiling chloroform, boiling water, sonicating dichloromethane, aqueous solution of HF and aqueous solution of KOH. Not only did the 4VP layer provide chemisorption sites for the palladium complexes without the need for prior sensitization in SnCl2 solution during the electroless plating process but it also served as the adhesion promotion layer and diffusion barrier for the electrolessly deposited copper. The 180degrees-peel adhesion strength of the electroless deposited copper on the modified silicon surface was dependent on the extent of 4VP surface coverage and could reach about 4 N/cm.