Suppressive Effects on Copper Electrodeposition, Induced by Adsorption of Polyethylene Glycol and Pluronic Surfactants

We studied the adsorption of polyethylene glycol （PEG） and amphiphilic polyoxyethylene-polyoxypropylene-polyoxyethylene （PEO-PPO-PEO） triblock copolymers （Pluronic surfactants） on a model metal substrate（gold）and assessed their suppressive effect on copper electrodeposition. The adsorption was characterized using a quartz crystal microbalance with dissipation monitoring （QCM-D） technique and ellipsometry. The electrodeposition-suppressive effect was assessed using linear sweep voltammetry （LSV）. Results showed that the adsorption rate of these additives on the metal substrate contributed to the electrodeposition-suppressive effect to a greater extent than the adsorption mass （or the adsorption density）, as inferred for previously reported cationic surfactant systems. The addition of HCl into an H2SO4 aqueous solution increased the adsorption mass of hydrated PEO, leading to increased suppressive effects on copper electrodeposition. In contrast, addition of HCl decreased suppressive effects in the Pluronic surfactant systems, although their adsorption occurred in a manner similar to that for cationic surfactant systems for shorter PEO analogs and in a manner similar to that for the PEG systems for a longer PEO analog. These results suggest that the electrodeposition-suppressive effect is influenced mainly by the adsorption rate, but hydration of the adsorption layer and the adsorption ability also contribute to the suppressive effect.