This work demonstrates the utility of a tartaric acid-based slurry for chemical mechanical planarization (CMP) of tantalum and copper. Cu and Ta disks and wafers were polished at a pressure of 2 psi, and selective removal of the two metals was achieved by adjusting the pH of the slurry in the range 3.0-8.0. Changing the H2O2 content of the slurry can further regulate the relative removal rates of Cu and Ta. Optical profilometry shows very good postpolish wafer surface quality. Possible mechanisms for the chemically promoted material removal are discussed. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2980345] All rights reserved.