Electrochemical Deposition of Nanoscaled Palladium Catalysts for 65 nm Copper Metallization

The preparation of nanoscaled palladium (Pd) particles for catalyzation of electroless copper (Cu) plating has been investigated in this research. Nanosized Pd catalysts were electrochemically deposited on substrates using displacement activation and sensitization activation, and their formation and microstructures were characterized. By displacement activation, large Pd particles with nonuniform size distribution from 20 to 200 nm are observed, resulting in subsequent rough and discontinuous Cu films electrolessly deposited on these Pd catalysts. In comparison, tremendous, small, and uniform Pd nanoparticles of about 10 nm are obtained by sensitization activation as fine nucleation sites for following electroless deposition of smooth and conformal Cu films. Nucleation, growth, coalescence, and then connection and film growth steps are observed in the formation process of Cu films. No preferred orientation of both electrolessly deposited Cu films is found. Well-controlled, electrochemically deposited nanoscaled Pd catalysts and uniform Cu films can be used as 65 nm Cu interconnect metallization.