No abstract

As the technology node of integrated circuits (ICs) shrinks down to 7 nm and below, cobalt (Co) has been identified as the promising candidate for the interconnect/contact material. In this paper, colloidal silica was used as abrasive, potassium tartrate (PTH) was used as the promoter of TEOS and complexing agent of Co and titanium nitride (TiN), H2O2 was used as oxidant. The effects of PTH and H2O2 on the removal rate (RR) of Co/TiN/TEOS were studied. Polishing results showed that PTH can improve the RR of Co/TiN/TEOS effectively. The removal mechanism was revealed by X-ray photoelectron spectroscopy (XPS), electrochemical and UV–visible (UV-vis) spectroscopy measurements. It revealed that PTH can complex with Co(II)/Co(III) and TiO2+ ions produced during CMP, and formed Co(II)-PTH/Co(III)-PTH and TiO-PTH complex increases the RR of Co and TiN. The attractive force between silica abrasive and TEOS surface was improved as the concentration of PTH increased, resulting in the mechanical force increased and the RR of TEOS enhanced.

In this study, the passivation mechanism of three azole inhibitors with different functional groups, benzotriazole (BTA), 5-methylbenzotriazole (TTA), 1-H carboxyl benzotriazole (CBT), on cobalt in H 2 O 2 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 Co 2+ 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.