In the chemical mechanical polishing (CMP) of Cu, the Cu surface is oxidized and is concurrently removed by the mechanical function of an abrasive. Surface oxidation can lead to severe surface corrosion, and to prevent this, a corrosion inhibitor is added to slurries. Accurate understanding of the competition between oxidation and passivation is essential for advanced Cu CMP technologies. In this work, layer formation on clean Cu surfaces in benzotriazole (BTA), H2O2, and BTA–H2O2 aqueous solutions was studied by in situ spectroscopic ellipsometry. Time changes of ellipsometric parameters are discussed with respect to BTA and H2O2 concentrations. It was found that the BTA adsorbs onto the Cu surface and the adsorbed BTA transforms into a Cu–BTA complex in about 3 min after the onset of adsorption. The BTA/complex layer passivates the Cu surface against oxidation by H2O2.

The effect of pH on layer formation onto clean Cu surfaces in benzotriazole (BTA) aqueous solutions was studied by in situ spectroscopic ellipsometry. The effect of H2O2 addition was also investigated. Time changes in the ellipsometric parameters Ψ and Δ, which correspond to the structural changes of the layers on Cu, were discussed. In acidic solutions, a BTA or a Cu–BTA complex layer grows directly on Cu. The out-diffusion of Cu is suppressed at the Cu layer interface. When H2O2 was mixed, the Cu surface is eroded in acidic solutions. In alkaline solutions, the BTA layer grows on the oxidized Cu layer, or no growth occurs, depending on the composition of the solutions. In neutral solutions, the Cu–BTA complex layer forms on Cu, and the uncovered part is oxidized in the presence of H2O2.

No abstract