Convection-Dependent Competitive Adsorption between SPS and EO/PO on Copper Surface for Accelerating Trench Filling

Abstract

In the absence of halogen ion, the convection-dependent competitive adsorption between bis(3-sulfopropy)-disulfide (SPS) and poly(ethylene glycol)-block-poly(propylene glycol) copolymer (EO/PO) on unpowered (in open circuit) copper surface is found in sulfuric acid solution. Galvanostatic measurements and electrochemical impedance spectroscopy were employed to analyze this particular adsorption behavior, revealing that the adsorption of EO/PO is enhanced by increased local convection intensity. The molecular dynamic simulation demonstrates that the increase of EO/PO adsorption decreases the adsorption of coexisting SPS on copper surface, supporting that the enhanced EO/PO adsorption in strong convection condition leads to the decrease of coexisting SPS adsorption on copper surface with the increase of convection intensity. The study of this convection-dependent competitive adsorption behavior enriches the understanding for the convection-dependent adsorption (CDA) behavior on electrolytic copper ‘bottom-up’ filling. Besides, the competitive adsorption behavior serves as a powerful handle to manipulate the accumulation of SPS at via or trench bottom before electroplating for improving the efficiency of via or trench filling. For example, the silicon wafer trench filling by copper electroplating is significantly accelerated with the introduction of convection-dependent competitive adsorption. Furthermore, a possible mechanism for accelerating trench filling by pre-adsorption process of SPS together with EO/PO is proposed.