Bottom-up fill of copper in high aspect ratio via holes by electroless plating

We succeeded in the bottom-up filling of Cu by electroless plating for the first time. Essential points of this technology are the use of an ultra-thin ICB-Pd catalytic layer and the addition of an adequate amount of sulfopropyl sulfonate inhibiter (SPS) to the electroless plating bath. The adhesion strength of the electroless-plated Cu was strong enough to endure against CMP processing, and a 100 nm diameter via hole with 800 nm depth was completely filled by electroless plating only.