Passivation Kinetics of 1,2,4-Triazole in Copper Chemical Mechanical Polishing

Optimizing the copper slurry, especially the corrosion inhibitor, is critical to its successful application in copper chemical mechanical polishing (CMP) for the next-generation ultra-large scale integrated circuits manufacturing. In this paper, 1,2,4-triazole was considered to be a promising alternative to the conventional benzotriazole (BTA). The passivation kinetics of 1,2,4-triazole on the copper surface was investigated with several different electrochemical techniques, including open-circuit potential, potentiodynamic polarization, cyclic polarization and chronoamperometry. The results of the chronoamperometry experiments show that the peak response I-f and the time constant tau(f) of the current density from the faradaic reactions are critical to the passivation kinetics of 1,2,4-triazole. Based on the electrochemical results and the existing material removal model, the material removal mechanism of copper when being polished with the slurry containing colloidal silica, H2O2, glycine, 1,2,4-triazole and with pH 6.0 is inferred to be corrosion-enhanced wear dominant. Additionally, the passivation kinetics parameters of 1,2,4-triazole were compared with those of BTA. I-corr, I-f and tau(f) of 1,2,4-triazole are all larger than those of BTA, which can be used to partly explain why 1,2,4-triazole's passivation is relatively weaker than that of BTA and its resultant suitability as an alternative corrosion inhibitor for copper CMP. (C) 2016 The Electrochemical Society. All rights reserved.