The effect of pH on the material removal rate (MRR) of Cu in an organic phosphonic acid system abrasive-free slurry was investigated by thermodynamics. X-ray photoelectron spectroscopy analysis, and electrochemical measurements. The pH range can be divided into three chemical regions according to the evolution of the polishing MRR, which relies on the effect of pH on the chelating effect of the chelating ligand. diethylene triamine penta methylene phosphonic acid. The higher the pH is. the more efficient the chelating ligand is. In the alkaline pH region. because of the enhanced chelating effect and precipitation of the chelate complex on the surface, both the MRR and friction coefficient during polishing process increase significantly, and the corrosion current acquired from the potentiodynamic polarization measurement decreases. (c) 2009 The Electrochemical Society. [DOI: 10.1149/1.3055985] All rights reserved.