Inhibition Due to the Interaction of Polyethylene Glycol, Chloride, and Copper in Plating Baths:  A Surface-Enhanced Raman Study

The synergic effect of poly(ethylene glycol) together with chloride ion for inhibiting copper deposition in copper electroplating has been of particular interest for some time. In this study, the potential-dependent behavior of poly(ethylene glycol), with or without chloride ion in a copper electroplating bath is investigated using the surface-enhanced Raman spectroscopy technique. The presence of chloride proves to play a significant role in enhancing PEG adsorption to the Cu electrode surface. More importantly, spectroscopic evidence strongly suggests the formation of a PEG−Cu−Cl complex. By comparing experiment with vibrational modes calculated by using the Hartree−Fock method with a 3-21G* basis set, the structure of this complex is proposed to be a three-coordinated Cu center with two oxygen atoms from PEG and one chloride ligand.