Potential-pH diagrams of interest to chemical mechanical planarization of copper

The chemical mechanical planarization (CMP) of copper-based structures is typically carried out with slurries that contain an oxidant, a complexant, and a corrosion inhibitor. The dissolution and passivation of copper are strongly influenced by the pH and the redox potential of the slurry systems. In this paper, potential-pH diagrams for copper in aqueous systems containing various organic compounds and oxidants of interest to copper CMP are presented. The stability region of copper complexes under varying copper and ligand concentrations and the effect that they may have on copper removal during CMP are discussed. Experimental values of redox potentials in some of the chemical systems are included in the diagrams. In cases where the free energy of formation of organic ligands was not available in the literature, values were estimated using the group contribution method.