Electrochemical behavior of copper in conductive peroxide solutions

Electrochemical studies of copper in peroxide solution for chemical mechanical planarization applications was conducted in a solution media containing Na2SO4 as an inactive and highly conductive electrolyte salt. The low current values observed during anodic potentiodynamic polarization of copper in peroxide based solutions can be mistakenly interpreted as a development of passivity at the copper surface. Cathodic pretreatment of the copper surface followed by anodic potentiodynamic polarization reveals the formation of an anodic peak at potentials of 0.2-0.3 V-SCE. The formation of a dense deposition film of copper oxides at potentials below 0.4 V is attributed to increase in the solution pH at the electrode-electrolyte interface to values above pH 5.5. However, further positive shift in the applied potential decreases the cathodic reduction rate of H2O2, leading to a decrease in the solution pH values at the electrode/electrolyte interface and consequently, decreases the deposit formation rates covering the copper surface. The addition of benzotriazole (BTA) to peroxide solutions was also studied, and it was revealed that BTA cannot provide the protection needed to the copper surface in this system. (C) 2004 The Electrochemical Society.