Degradation of poly(ethylene glycol–propylene glycol) copolymer and its influences on copper electrodeposition

•PEG–PPG copolymer is fragmented during Cu electrodeposition.•Fragmented PEG–PPG is continuously accumulated in the aged solution.•Fragmented PEG–PPG is easily desorbed from Cu surface with the competition of SPS.•Aged plating solution results in the higher electrical resistivity of deposited Cu.

In this work, the degradation of poly(ethylene glycol–propylene glycol) copolymer (PEG–PPG) and its effect on the electrodeposition of Cu were investigated. PEG–PPG became fragmented during the electrodeposition with changing its terminal groups from hydroxyl to aldehyde, formic ester, and ketone. The aged solution showed a higher saturation current density than the fresh solution in chronoamperometry (CA) measurements, resulting from an easier desorption of the cleaved PEG–PPG from the copper surface through the competition with bis-(3-sulfopropyl)-disulfide (SPS). Furthermore, the electrical resistivity of Cu films deposited from the aged solution increased due to a decrease in the grain sizes.