Electroplating performance enhancement by controlling resistivity of electrolyte with porous materials for advanced Cu metallization

An advanced electroplating process has been developed for 0.1 μm nodes. The electroplating of Cu was performed by using a porous ceramic plate between an anode and a cathode (a seed Cu layer on the wafer). This configuration showed remarkable thickness uniformity of grown film even for the thin Cu seed layer of 20 nm. This thinner seed layer secured the hole opening during the filling, and resulted in improved hole filling capability. By using the 80 nm thick seed layer, φ0.15 μm holes with A.R. 5 have been successfully filled. The electrical resistance increase of the plating solution brought about by inserting the porous ceramic provides a uniform electric field between two electrodes. Moreover, the ceramic plate behaves as a filter of the plating solution, and undesirable reactions at anode surface can be isolated from the wafer surface. These particular effects by using the porous ceramic plate resulted in a great improvement of the electroplating performance, such as film thickness uniformity within wafer, filling capability, and also the chemical process stability of plating.