Determination of Current Density Suppression Ability of Poly(ethylene glycol) during Copper Electrodeposition by an Electrochemical Analysis with a Microfluidic Device and an Electrochemical Quartz Crystal Microbalance

Abstract

The adsorption behaviour of poly(ethylene glycol) (PEG) as an additive during Cu electrodeposition was investigated using a microfluidic device. First, the current density (i) transition curves were measured by rapid exchange from the base electrolyte to electrolytes with different concentrations of additive PEG. Then, the effective surface coverage ratio (θEFF) of the electrodes by PEG was obtained. Equations relating θEFF and the PEG adsorption rate constant (ka) as a function of cPEG (or PEG flux, u·cPEG) were determined from the PEG concentration (cPEG) and average flow velocity of the electrolyte (u) dependency. Finally, the amount of increase the weight on the electrode (Δm) by PEG for different cPEG was measured using a flow cell type electrochemical quartz crystal microbalance (EQCM), and then used to calculate θEFF, assuming the adsorbed PEG molecules are spherical. Results revealed a strong correlation between the Δm and a decrease in i.