Effect of Cl[sup −] on the Adsorption–Desorption Behavior of PEG

The adsorption–desorption behavior of polyethylene glycol (PEG) on the cathode surface in copper plating solution with and without was investigated by cathodic polarization measurement and electrochemical impedance spectroscopy (EIS) measurement. Cathodic polarization analyses show that the inhibiting effect of PEG is potential-dependent in the solution with and without . EIS analyses suggest that the adsorption of PEG is strengthened by the existence of , and both adsorption and desorption potential range of PEG are widened by the existence of , which is attributed to the different adsorption mode of PEG. The adsorption of PEG in the solution without is in the form of and , which adsorb on the cathode surface mainly by two acting forces, the van der Waals force and the electrostatic force. In the solution with , the adsorption of PEG is mainly in the form of and . It is due to the specific adsorption ability of on the electrode surface that the adsorption of PEG is greatly strengthened compared with that in the solution without . Thus, the adsorption and the desorption potential range of PEG are widened, and PEG shows a much stronger inhibiting effect on copper deposition in a wider potential range.