Effect of hydrogen peroxide on oxidation of copper in CMP slurries containing glycine and Cu ions

Abstract

This study compares the oxidative dissolution, passivation, and polishing behavior of copper chemical–mechanical polishing in the presence of hydrogen peroxide, glycine, and copper sulfate. High purity discs were used to study the dissolution and oxidation kinetics under static and dynamic conditions at pH 4 with varying H 2O 2 concentrations. Changes in surface chemistry of the statically etched copper disc were investigated using X-ray photoelectron spectroscopy (XPS). In the presence of H 2O 2, the copper removal rate reached a maximum at 1% H 2O 2 concentration, and decreased with further increase in H 2O 2 concentration. Electrochemical studies indicate a strong passivation process at higher H 2O 2 concentrations due to the rapid formation of oxide on the surface. With the further addition of glycine and copper sulfate to the slurry, the copper removal rates increased significantly and the maximum removal rate shifted to a H 2O 2 concentration of 3%. Electrochemical investigation indicates an enhanced dissolution of copper, which might be due to the strong catalytic activity of Cu(II)–glycine complexes in decomposing H 2O 2 to yield hydroxyl radicals. XPS results suggest that the passivation at higher H 2O 2 concentrations in the presence of glycine and copper sulfate is provided by the OH radicals adsorbed on Cu surface.