Formation of electroless barrier and seed layers in a high aspect ratio through-Si vias using Au nanoparticle catalyst for all-wet Cu filling technology

An all-wet process was achieved using electroless deposition of barrier and Cu seed layers for fabrication of a high aspect ratio through-Si via (TSV). Formation of a thin barrier metal layer of Ni–B, Co–B and Co–W–B is possible using a Au nanoparticle (AuNP) catalyst, which is densely adsorbed on the SiO2 of the TSV sidewall. A silane coupling agent of 3-aminopropyl-triethoxysilane is effective for enhancement of the density of adsorption for AuNP. A conformal electroless Cu layer is deposited on the barrier layer by displacement plating without a catalyst. The adhesion strength between the electroless barrier layer and the SiO2 substrate is increased by annealing at 300 °C. These results strongly suggest that an all-wet process for the formation of Cu-filled TSV with a high aspect ratio is practically possible.

► Conformal electroless barrier and seed layers were formed in high aspect ratio TSV. ► Au nanoparticles of 20 nm diameter were used as a catalyst. ► Adhesion strength of the diffusion barrier films are enhanced with annealing at 300 °C. ► This technology enables all-wet fabrication of Cu-filled TSV.