Effect of Potassium Tartrate on Removal Rate Selectivity of Co/TiN/TEOS for Cobalt "Buff Step" Chemical Mechanical Planarization

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. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.