1,2,4-Triazole as a corrosion inhibitor in copper chemical mechanical polishing

Corrosion inhibitors in copper slurries play a quite important role in copper chemical mechanical polishing. Besides widely used benzotriazole (BTA), 1,2,4-triazole has been demonstrated to be another promising copper inhibitor. In this paper, the properties of 1,2,4-triazole were well investigated compared with BTA. It is revealed that 45 mM 1,2,4-triazole can achieve equivalent chemical protection for copper surface as 2 mM BTA. The results of the tests on copper patterned wafers show that the slurry with 45 mM 1,2,4-triazole as the copper inhibitor and 0.1 wt.% colloidal silica can realize lower dishing and erosion than the slurry with 1 mM BTA and 5.0 wt.% colloidal silica. In order to investigate the passivating mechanism, the passivating paths of 1,2,4-triazole on the copper surface were also studied. The results indicate that there exist two passivating paths: the first one is the direct growth of the Cu-1,2,4-triazole passivating film on the copper surface while the second one is the redeposition of Cu-1,2,4-triazole complex on the oxidized copper surface. For the second one, the cupric ions dissolved in slurry can react with the 1,2,4-TAH species, and such reactions will result in the formation of Cu-1,2,4-triazole complex as a form of nano-particles and precipitate, which can subsequently redeposit on the oxidized copper surface to form a weak passivating film as a complement of the first direct growth path.