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

Abstract

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 If and the time constant τf 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. Icorr, If and τf 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.