Transitional Additive Adsorption with Co-Addition of Suppressor and Leveler for Copper TSV Filling

Abstract

Suppression of copper electrodeposition by two additives, suppressor and leveler, were studied using a microfluidic device. In industry, two suppressing agents, one a suppressor and the other a leveler, are usually added together into the plating bath for copper bottom-up TSV (Through Silicon Via) filling. Several studies, including our own previous one, suggest that the leveler is the essential agent for bottom-up filling, with its strong suppression and rapid deactivation. The suppressor shows moderate suppression and slow deactivation, and is believed to interfere with bottom-up deposition. It is unclear why bottom-up deposition is possible with co-addition of the suppressor and why co-addition is popular. In the present study, the suppressor and the leveler were supplied onto the plating surface sequentially, using a microchannel; it was found that the leveler replaces the suppressor. The leveler and suppressor were also supplied simultaneously; the suppressor initially covered most of plating surface, but the leveler gradually replaced the suppressor, and the plating surface was finally dominated by the leveler.