Mechanism of copper removal during CMP in acidic H(2)O(2) slurry

Chemical mechanical polishing of copper was performed using H(2)O(2) as oxidizer and alumina particles as abrasives. Electrochemical techniques were used to investigate the dissolution/passivation behavior of high-purity Cu disk under static and dynamic conditions at pH 4 with varying H(2)O(2) concentrations. Changes in the surface chemistry of the statically etched Cu disk were investigated using X-ray photoelectron spectroscopy. The Cu removal rate reached a maximum at 1% H(2)O(2) concentration and decreased with a further increase in H(2)O(2) concentration. The static etch rate showed the same trend. The etched surface morphology indicates that the removal of copper is primarily the result of electrochemical dissolution of copper at low H(2)O(2) concentrations. However, at increased H(2)O(2) concentrations, the copper oxidation rate increases, resulting in a change in the Cu removal mechanism to mechanical abrasion of the oxidized surface. (C) 2004 The Electrochemical Society