Triblock copolymers as suppressors for microvia filling via copper electroplating

In this work, ethylene-propylene-ethylene (EPE) oxide triblock copolymers were found to be effective suppressors for microvia filling during copper electroplating. The studied EPE copolymers were divided into two groups according to their solubility and compositions. The first group was composed of EPE 1000, EPE 2000, and EPE 3500, and the second group contained EPE 2450, EPE 2900, and EPE 8000. In particular, the function of the triblock copolymer suppressors (e.g. EPE 2900) and their synergistic effect with other additives during copper electroplating were studied by galvanostatic measurements, suggesting that the suppression strength was greatly dependent on Cl ^-. In addition, cyclic voltammetry (CV) measurements indicated that a given suppressor in the plating bath required an optimal Cl^- concentration to realize the strongest suppression strength. Then the filling performance of the plating bath using different suppressors was systematically compared by galvanostatic measurements and filling plating experiments in the plating bath with a fixed Cl^- concentration (60 ppm), an optimal Cl^- concentration, and a wide operation window of Cl^- respectively. These experimental analyzes indicated that EPE 2000 and EPE 2900 were the best suppressors in the first and second group, respectively. The relevant mechanism of triblock copolymer suppressors for microvia filling was discussed.