THE CHEMISTRY OF THE ADDITIVES IN AN ACID COPPER ELECTROPLATING BATH .1. POLYETHYLENE-GLYCOL AND CHLORIDE-ION

The mechanisms by which chloride ion and polyethylene glycol, two of the common additives in commercial acid copper electroplating baths, influence the cathodic deposition of copper have been investigated using potential sweep and potential step techniques as well as laser Raman spectroscopy. It is confirmed that adsorption of polyethylene glycol onto the copper surface decreases strongly the rate of copper deposition. In fact, it is suggested that the polymer can adsorb in two different forms. One predominates close to the open circuit potential and may well be a copper chloride complex with the polyethylene glycol as a ligand. The other prevails at the more negative potentials where copper plating is carried out; this species is likely to be the simple, neutral polymer molecule.