Cu seeding using electroless deposition on Ru liner for high aspect ratio through-Si vias

High aspect ratio through-Si vias (AR=16.7) filling has been achieved by using non-PVD seed metallization approach. We demonstrate the formation of conformal and thin electroless deposited Cu seed on Ru liner. The optimized ELD Cu process was conducted at room temperature on activated Ru surface, which can improve the ELD bath life time. The deposited Cu with 2,2′ bipyridyl shows smoother and higher purity inside the Cu film.