Suppression behavior of additive is considered as an essential factor for the bottom-up filling, but critical suppression behavior is not well observed by conventional electrochemical measurements. Desorption of suppressing additive from plating surface seems to have important role, because suppression breakdown occurs from the TSV bottoms where the additive supply is most limited. In this study, we made a microfluidic device to realize precise mass transport and quick switching of plating solutions, and in-situ observation of plating surface was performed. Figure 1 shows a result with a commercial leveler. Initially, VMS (virgin make-up solution) with no additive was supplied into the micro channel, and copper plating was performed on Pt working electrode with 100μm in diameter for 5 s. Then, the solution containing leveler was supplied for 10 s. Finally, the solution was switched to VMS again and additive desorption was monitored. With small overpotential (-550 mV vs. MSE), plating surface was covered by the leveler and strong suppression was observed. After the plating solution was switched to VMS with no additives, localized depositions were observed all over the plating surface. While with large overpotential (-600 mV vs. MSE), strong suppression was observed only on up-stream region of the plating surface where bright smooth surface was kept during the leveler supply. After the solution change, suppression breakdown with localized depositions were observed gradually from the lower-stream region. Identical experimental procedure was applied to several additives and the behaviors were compared.
