Synergistic Effect of Different Additives on Microvia Filling in an Acidic Copper Plating Solution

Abstract

Microvia filling by copper electroplating was carried out using a plating bath with a triblock copolymer comprised of propylene oxide (PO)-ethylene oxide (EO)-propylene oxide (PO) (named PEP) and bis– (3–sulfopropyl) disulfide (SPS) as the suppressor and the accelerator respectively, the suppression function of the triblock copolymers suppressors and their synergistic effect with other additives during copper electroplating were studied by galvanostatic measurements (GMs) and the cyclic voltammetry (CV), the results of GMs revealed that the suppression of PEP on copper electrode position strongly depended on the chloride ion (Cl−). In addition, the CV measurements indicated that a given Cl− in the plating bath required an optimal suppressor concentration to realize the strongest suppression strength. The negative values of the standard free energy of adsorption (ΔG0ads) suggest that the adsorption of SPS onto the cathode surface was a spontaneous process and physisorption was dominant in the plating formula. An optimal copper plating solution composed of CuSO4, H2SO4, PEP, SPS, chloride ions, and Janus Green B (JGB) was developed and used to perform bottom-up copper filling of microvias.