Front-side metallization of silane-compoundmodified Si by electroless deposition of Ni(P) and interfacial characterizations

Front-side metallization techniques for nonconductive substrates receives numerous attention due to their practical application importance in the microelectronic and solar cell industries. Electroless deposition of Ni(P) with the help of catalyst such as Sn/Pd colloids is a common method to deposit a metallic film on non-conductive substrates. However, weak physical adsorption of the Sn/Pd colloids on the substrate may influence the adhesion strength of the Ni(P) film. Besides, employment of the Sn/Pd colloids involves an acceleration step (using acid solution to remove the Sn ion shell) which inevitably increases the complexity of the activation process. In this study, we demonstrated a promising method to fabricate an adhesive Ni(P) film on a textured Si substrate by using polyvinylpyrrolidone-capped Pd nanoclusters (PVP-nPd) as the catalyst and a silane compound layer as an agglutinant to bridge with the Pd cores in the PVP-nPd clusters. An improved adhesion strength of the Ni(P) film on Si is obtained even without postannealing treatment which shows high potentials in the applications of temperature-sensitive substrates. For potential application in the Si-based solar cells, post-annealing treatment was conducted to form the Ni silicides at the Ni(P)/Si interface. The experimental results indicated that the cleaning process of Si surface prior to the Ni(P) film deposition was crucial for the film uniformity and stability against the thermal annealing treatment.