Adsorption/Desorption of Suppressor Complex on Copper: Description of the Critical Potential

The acid cupric sulfate solutions, used for Damascene copper plating, contain several additives which provide the differential deposition rate inside cavities for void-free fill. Most of the models for this process, available in the literature, can successfully predict trends. However, these models miss fines as they are based on physical adsorption only. Since the copper surface has a complex chemistry, a physicochemical approach is needed to describe all the reaction mechanisms involved. In this work we provide some further insight into the thermodynamics of copper deposition inhibition by the suppressor polymer. The quantitative participation of each solution component is discussed and the adsorption/desorption reaction for the suppression is balanced based on the achieved results. In addition, a value for the standard critical potential was obtained which made possible the solubility constant for the Cu(I)-Suppressor-Cl complex to be estimated.