Copper chemical mechanical planarization (CMP) depends for its efficacy on many parameters, including the need for the solution to passivate the surface of copper. The influence of copper ions on the formation of such protective layers in an acidic solution containing BTA and glycine was investigated using potential-step chronoamperometry using two types of copper microelectrode, namely a three dimensional and a planar electrode. After stepping the potential of the copper electrodes to 0.6 V SHE, the measured current decayed as the protective layer was progressively formed. However, with concentrations of Cu(NO3)(2) exceeding 0.1 mM, the current declined to a minimum, and subsequently increased. This behavior is attributed to the homogeneous nucleation and growth of Cu(II)BTA(2) precipitates in the boundary layer near the copper surface. For prolonged chronoamperometry at 0.6 mM of Cu(NO3)(2), the current began to decrease again after 100 seconds. This is thought due to the growth of bulk CuBTA(2) precipitates toward the copper surface and repassivation of the surface. The increase in current due to homogeneous precipitation implies unsuccessful protection of the copper surface. This situation could easily arise during copper CMP. Thus, for effective CMP it is clearly necessary to control the concentration of copper ions in the solution. (C) 2013 The Electrochemical Society. All rights reserved.