Effect of Benzotriazole and 5-Methyl/1-H Carboxyl Benzotriazole on Chemical Mechanical Polishing of Cobalt in H₂O₂ Based Slurry

In this study, the passivation mechanism of three azole inhibitors with different functional groups, benzotriazole (BTA), 5-methyl-benzotriazole (TTA), 1-H carboxyl benzotriazole (CBT), on cobalt in H2O2 based slurry were investigated. Results showed that cobalt (Co) has the highest removal rate (RR) and static etching rate (SER) in the solution without inhibitors, and RR and SER of Co decreased when three inhibitors were added to the reference solution respectively. However, compared with BTA and TTA, CBT showed the strongest passivation effect. Through the single frequency EIS experiments and X-ray photoelectron spectroscopy (XPS) measurements analysis, all three azole inhibitors can react with Co2+ to form insoluble networked nanoparticles on the Co surface, but CBT had the thickest passivation film, which was inferred that the carboxyl group on the CBT can not only increase the coverage area on the Co surface like the methyl group, but also the oxygen on the carboxyl group can chemically adsorb on the Co surface like the N-17 on the imidazole ring. Moreover, TTA showed better passivation effect than BTA due to the existence of the methyl on TTA, which can increase the coverage area on Co surface and prevent the polishing slurry from contacting Co surface.