Low temperature through-Si via fabrication using electroless deposition

All-wet fabrication process using electroless deposition of barrier and Cu seed layers has been achieved for a high aspect ratio through-Si via (TSV). Formation of thin barrier metal layer of NiB and CoB is possible by the use of nano particles catalyst which is densely adsorbed on SiO₂ of TSV sidewall. Silane coupling agent with 3-aminopropyl-triethoxysilane is effective for enhancement of adsorption density of nanoparticles. Conformal electroless Cu layer is deposited on the barrier layer without catalyst by displacement plating. The adhesion strength between electroless barrier layer and SiO₂ substrate is strengthened by annealing. These results strongly suggest a possibility of the all-wet process for high aspect ratio TSV.