Adsorption of Pd nanoparticles catalyst in high aspect ratio through-Si vias for electroless deposition

We studied electroless Co–W–B plating in through-Si vias (TSVs) using Pd nanoparticles (Pd-NPs) as a catalyst. The density of adsorbed Pd-NPs on SiO2 in the high aspect ratio TSVs was over 8500/μm2 after a long adsorption treatment. No Pd-NP agglomeration was observed. In contrast, agglomerates of large particles were observed after a conventional Sn–Pd colloid adsorption treatment. Using a Pd-NP catalyst, we succeeded in the formation of a thin continuous electroless Co–W–B barrier layer in high aspect ratio TSVs. The adhesion strength of the Co–W–B layer increased with increasing particle density of the Pd-NPs. These results indicate that the process with Pd-NPs catalyst is a promising method for the formation of a thin barrier layer in high aspect ratio TSVs at low temperatures.