Hydroxyl radical formation in H2O2-amino acid mixtures and chemical mechanical polishing of copper

Hydroxyl radicals play an important role in the planarization of copper films using hydrogen peroxide-based slurries during microelectronic device fabrication. The generation of hydroxyl radicals (*OH) from hydrogen peroxide in the presence of several amino acids and Cu2+ ions was monitored using p-nitrosodimethylaniline as the *OH trapping agent. While the addition of either amino acid or Cu2+ ions to H2O2 does not generate significant amounts of *OH, the addition of both of them together resulted in a significant increase in the *OH concentration. This suggests that the Cu2+-amino acid complex (chelate) is an extremely effective catalyst in decomposing H2O2 to yield *OH. The rate constant for *OH trapping as well as the "initial" *OH concentrations in the presence of several amino acids and Cu2+ ions have been measured. Hydroxyl radical is a much stronger oxidant than hydrogen peroxide and enhances the removal rates of copper during chemical mechanical polishing (CMP) in H2O2-based slurries. This is confirmed by the copper dissolution/polish rates reported here in the presence of glycine without or with alumina abrasives. The role of benzotriazole as an effective passivating agent that can enhance planarization efficiency in Cu CMP using peroxide-based slurries has also been investigated. (C) 2000 The Electrochemical Society. S0013-4651(99)12-100-1. All rights reserved.