In this article, we analyze the effect of complexing agents in Cu chemical mechanical polishing slurry on the formation of oxide and the evolution of stress. The passivation property and surface morphology of the oxide on the surface showed significant differences depending on the kind of complexing agent. Oxalic acid showed fast oxide formation with poor passivation performance, and this caused large tensile stress evolution over 250 MPa in the Cu film. The synergetic effect of stress evolution and temperature increase due to the friction during the polishing caused severe pitting of the Cu surface after polishing in oxalic-acid-based slurry. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3236391] All rights reserved.