Effect of Different Palladium Nanoparticles on the Adhesion Between Electroless-Deposited Nickel-Phosphorus Film and Silane-Compound-Modified Silicon Surface

Eletroless deposition of nickel/phosphorus (Ni/P) film is a very promising skill for preparing diffusing barrier layer on silicon wafer. In general, palladium metal is needed as the catalyst to initiate electroless Ni/P deposition. In this study, we synthesized two types of palladium nanoparticles which is capped by polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA), coded as PVP-Pd & PVA-Pd, as the catalysts of electroless deposition. In order to enhance the adsorption of PVP-Pd or PVA-Pd on silicon surface, we apply 3- 2-(2-aminoethylamino)ethylamino propyl trimethoxysilane (ETAS) as a coupling agent to modify silicon surface then followed by electroless Ni/P deposition. Evidenced by transmission electron microscopy and scanning electron microscopy, PVP-Pd reveals slightly aggregated, while the particle shape of PVA-Pd is clearly defined; this makes a better distribution when PVA-Pd nanoparticles are adsorbed on silicon surface so that the adhesion of catalyst as well as Ni/P film is further improved. Finally, the interaction between ETAS and PVA-Pd were further explained by X-ray photoelectron spectroscopy. Compared with the adhesion of Ni/P layer catalyzed by commercial Sn/Pd colloids on unmodified silicon surface, the adhesion of Ni/P layer catalyzed by PVP-Pd or PVA-Pd on the ETAS modified silicon surface improved significantly by 2~3 times without the need of post-annealing treatment.