Synthesis and characterization of PVP stabilized Ag/Pd nanoparticles and its potential as an activator for electroless copper deposition

Poly(N-vinyl-2-pyrrolidone) (PVP) stabilized Ag/Pd nanoparticles have been successfully synthesized at various molar ratios. The transmission electron microscopy images show the diameters of Ag/Pd nanoparticles decrease with increasing I'd molar ratios. Data from UV-vis absorption spectroscopy, X-ray diffraction and energy-dispersive X-ray analysis (EDX) all confirm the formation of a bimetallic structure. Additionally, the EDX shows that the average composition of the bimetallic nanoparticle is approximately equal to the feeding solution while the X-ray photoelectron spectroscopy reveals the surface is palladium-rich, which implies an inhomogeneous alloy structure. ne Ag/Pd (3/7) nanoparticles have the highest deposited amount of copper owing to its larger surface area even though their specific activity is less than palladium nanoparticles. Furthermore, the effect of the molecular weight of the protective agent was also studied. Higher molecular weight will result in a greater thickness of the protective layer and therefore decrease the specific activity (PVP-(8000) Ag/Pd (3/7) > PVP-(29000) Ag/Pd(3/7) > PVP-(58000) Ag/Pd(3/7)). A preliminary test has demonstrated that copper can be successfully deposited and filled in 0.25 mum pattern wafer. Accordingly, the Ag/Pd nanparticles show promising application as a novel activator for electroless copper deposition. (C) 2005 The Electrochemical Society. All rights reserved.