Wet processes deposition for HAR TSV metallization using electroless Co liner and alkaline Cu seed layer

Through silicon via (TSV) with a high aspect ratio is in great demand in three-dimension (3D) integration technology. This work demonstrates a wet process flow for high aspect ratio TSV metallization using electroless cobalt deposition and copper electroplating. The electroless deposited Co liner and alkaline electroplating deposited Cu seed layer are successfully integrated into a 4 μm×50 μm TSV with an aspect ratio higher than 10:1. The electroless Co liner layer with a step coverage of up to 97% is formed on the TiN barrier by adding a suppressor additive in the plating bath. Then, a conformal alkaline Cu seed layer with step coverage of 75% is deposited on the Co liner layer throughout the TSV. Finally, the TSV is filled by the acidic Cu electroplating without voids, indicating the high quality of the Co liner layer as well as the Cu seed layer and the feasibility of the demonstrated wet process flow in the high aspect ratio TSV.