Novel seed layer formation using direct electroless copper deposition on ALD-Ru layer for high aspect ratio TSV

High aspect ratio through-Si vias (2 µmφ, AR 15) have been filled without voids on coupon scale by using an electroless deposited Cu seed layer on ALD-Ru. The total Cu overburden, which is ELD and filling Cu, was about 700 nm. In addition, the electroless Cu bath showed good stability during 2 hours with controlling pH to stabilize the deposition process. These results show the feasibility of electroless deposition in TSV processing.