Investigating the Effect of Chlorides on the Reaction Kinetics of a Copper Electrodeposition Process

Over the past two decades, the replacement of aluminum interconnects with copper is one of the biggest advances in semi-conductor industry. As the wiring density continues to increase, so does the demand for tighter control on the electrolytic copper deposition process for these industries. Apart from organic additives and other trace metals, one of the crucial component in plating baths mixtures for manufacturing PCB boards and photovolotaic cells is the intermediate cuprous ion composition, which is formed during the copper dispropornation reaction: 2 Cu + (aq) ⇌ Cu (s) + Cu 2+ (aq) The cuprous ion is typically unstable in normal acidic solution and it disproportionates into metallic copper and cupric ions. In the presence of chlorides however, the disproportionation reaction equilibrium is shifted and the cuprous ions are stabilized. Cuprous ions are also required in order for the other additives (brightener, suppressor, leveler) used in the process to operate at maximum efficiencies. It is therefore important to know if the Cu 2+ intermediate is truly formed and present during the a copper electrodeposition process. In this work, we used Autolab RRDE system to identify mechanisms governing copper electrodeposition process and study the influence of chloride concentration on the generation of intermediates.