The roles of H2O2 and alumina on the changes of metal removal rate, surface passivation and surface morphology in citric acid (CA) base slurry in simulated Cu chemical-mechanical polishing (CMP) was investigated. X-ray photoelectron spectroscopy (XPS) analysis indicated that H2O2 assisted oxide formation while citric acid promoted anodic dissolution of copper in various slurries that contained 1 wt.% Al2O3. Atomic force microscopy (AFM) revealed that Al2O3 abrasive particles modified the surface morphology by inducing surface deformation. The results of open circuit potential (OCP) and removal rate measurements clearly demonstrated that there existed a synergistic effect due to the chelating and oxidizing agents in Cu CMP (C) 2004 Elsevier B.V. All rights reserved.