Investigation of poly (1-vinyl imidazole co 1, 4-butanediol diglycidyl ether) as a leveler for copper electroplating of through-hole

Abstract

A leveler containing quaternary ammonium cations, namely poly (1-vinyl imidazole co 1, 4-butanediol diglycidyl ether) (VIBDGE) was synthesized and studied in this work. Quantum chemical calculations and molecular dynamics simulation of VIBDGE were employed to get insight to the adsorption model by assessing the molecular configuration and electronic orbital parameters. The simulation results reveal that VIBDGE will spontaneously absorb on the copper surface because of its tiling way, the generated nitrogen ions and the large molecular volume of VIBDGE. Galvanostatic measurements (GMs) and cyclic voltammetry (CV) tests were performed to investigate the electrochemical behaviors of VIBDGE and its synergistic mechanism with other additives. The results of GMs demonstrate VIBDGE exhibits good inhibiting performance in copper deposition. However, the reactant, namely 1-vinyl imidazole and 1, 4-butanediol diglycidyl ether, have no inhibition effect. Additionally, GMs results show that adsorption competition between bis-(sodium sulfopropyl)-disulfide (SPS) and VIBDGE is kinetically controlled and a steady state can be achieved regardless of the injection order of additives. The steady potential at lower rpm is less polarized and thus very beneficial for achieving uniform plating of through-hole (TH). The CV testes show that VIBDGE is capable of inhibiting copper deposition in the absence of chloride ions and chloride ions have a synergistic effect with VIBDGE. In addition, VIBDGE and PEG have competitive adsorption in copper deposition process. Consistent with the results of the GMs, the CV results illustrate that in the VIBDGE-SPS-PEG-Cl- system, the amount of copper deposited in the center of TH is more than that of the surface. Through the results of electroplating, it is confirmed that VIBDGE-SPS-PEG-Cl- system significantly improves the throwing power which is in accordance with simulation and electrochemical experiments.