Electroless deposition of barrier and seed layers for via last Cu-TSV metalization

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