Schemes using chemical mechanical polishing of copper have been proposed for the patterning of interconnections in copper multilevel metallization. In this article, the phenomena involved in the removal of copper during copper chemical mechanical polishing are investigated. The concentration of chemical etchant in the polish slurry is varied to investigate the chemical component, and the applied pressure is varied to investigate the mechanical component. Two slurries, an ammonium hydroxide plus ferricyanide slurry and a nitric acid slurry, are used to polish both copper and Cu2O thin films. Removal of copper or Cu2O is hypothesized to be a result of mechanical abrasion, while the role of the chemical etchant is to dissolve the material abraded from the surface rather than to etch the material directly from the surface.