The deposition of copper metallization is achieved from acidic copper sulfate solution containing small concentrations of chloride, suppressor, accelerator, and leveler. Void-free filling of trenches and vias results from the complex interplay between the additives in the solution. Here we report on the adsorption/desorption of the copper-suppressor-chloride complex in solutions without accelerator or leveler. We show that desorption of the suppressor complex occurs at a critical potential that is dependent on the pH, chloride concentration, cupric ion concentration, and suppressor concentration. We derive an expression for the critical potential from which we determine the composition of the complex. In addition, the solubility product of the complex is determined to be log K-s=-14.4.