of the JES Focus Issue on Electrochemical Processing for Interconnects.

The adsorption kinetics of polyethylene glycol (PEG) during Cu electroless deposition was investigated in real-time by measuring the open-circuit potential (OCP) and mass change of a Cu electrode. The addition of PEG during the deposition caused an OCP decrease with a reduction in the deposition rate. It was found that the adsorption of PEG blocked active sites for the adsorption of formaldehyde, a reducing agent, resulting in the suppression effect. The adsorption kinetics of PEG was strongly dependent on the concentration and diffusion coefficient which is directly related to the molecular weight of PEG. The diffusion-controlled adsorption was observed when PEG concentration was low. At high PEG concentrations, the adsorption kinetics was adsorption-controlled when the PEG molecular weight was low and diffusion-controlled when the PEG had a high molecular weight. The strength of the suppression effect was also affected by the molecular weight of PEG: increasing the molecular weight enhanced the suppression effect