Potential-pH Diagrams of Copper for the Planarization Slurries with Different Complexing Agents

Planarization processes such as chemical mechanical planarization (CMP) and electrochemical mechanical planarization (ECMP) are typically carried out with slurries containing complexing agents as one of the principal chemical components. In such slurries, complexing agents enhance the solubility of copper and increase the dissolution rate of the abraded material, promoting higher copper planarization rates. The nature of the complexing agents used in the slurry, along with slurry pH and redox potential are among the key factors controlling the dissolution and passivation behavior of copper, and thereby governing the dynamic copper removal and planarization rates during the CMP and ECMP processes. In this paper, potential-pH diagrams of copper in aqueous systems containing a number of complexing agents including glutaric acid, maleic acid, α-alanine and α-aminobutyric acid are presented. The predominance regions of copper complexes under different copper and ligand activities and their implications on copper removal during planarization processes are discussed.