Highly adhesive electroless barrier/Cu-seed formation for high aspect ratio through-Si vias

A conformal diffusion barrier was formed in a high aspect ratio through-silicon via using electroless plating. Dense adsorption of Pd nanoparticle catalyst on SiO2 assisted the formation of a thin electroless Co–W–B layer, upon which an electroless Cu seed layer could be deposited. The adhesion strength of the Co–W–B film was enhanced by reducing the film thickness, and the maximum strength was obtained at a thickness of 20 nm. The Co–W–B layer exhibited good barrier properties against Cu diffusion to SiO2 after annealing at 300 °C, although slight diffusion of the Pd atoms in Cu was observed.

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