Surface chemistry studies of the chemical mechanical planarization (CMP) of copper are presented in this paper. Blanket copper samples were polished with an acidic alumina-based slurry which contains an organic acid salt (phthalic acid salt) and an oxidizer (H2O2). Surface studies using X-ray photoelectron spectroscopy (XPS) were performed on copper samples after chemical etching or CMP in order to determine the effect that different polishing parameters (i.e., pH and oxidizer concentration) have on the copper surface. XPS studies were also done on samples that were passively soaked in an acidic slurry mixture containing different concentrations of H2O2 to determine how the chemical action alone affects the removal of copper. The etching results revealed that a cuprous oxide (Cu2O) forms on the surface of etched metal while polished samples showed CuO and Cu(OH)(2). The effect of these copper oxide films on the removal of copper in passive etching and chemical mechanical polishing is discussed.