Characterization of 1, 2, 4-Triazole as Corrosion Inhibitor for Chemical Mechanical Polishing of Cobalt in H2O2 Based Acid Slurry

Cobalt has been applied as liners in current Cu interconnect and even as interconnect conductors in next-generation interconnect. In this work, effects of corrosion inhibitors 1, 2, 4-triazole (TAZ) on Co chemical corrosion, galvanic corrosion between Cu and Co, and Co polishing properties in the H2O2 based acidic slurry have been systematically investigated. Results show that 5 mM TAZ yields a low static etching and removal rate with a selectivity of about 1: 1 for Co to Cu, applicable for Co barrier/ Cu CMP, while 100 mM TAZ yields a high removal rate with same selectivity, applicable for Co via and trench CMP. It demonstrates that TAZ can effectively inhibit the galvanic corrosion between Co and Cu. Additionally, the adsorption behavior of TAZ on Co surface is both physisorption and chemisorption. In case of 5 mM TAZ, self-assembly TAZ molecules absorb on native Co oxide. In case of 100 mM TAZ, more soluble Co-TAZ complexes form, which reduces the stability of the passivation layer and results in pitting corrosion.