Potassium Oleate as a Dissolution and Corrosion Inhibitor during Chemical Mechanical Planarization of Chemical Vapor Deposited Co Films for Interconnect Applications

1,2-4 Triazole (TAZ), N-lauroylsarcosine sodium salt (NLS) and potassium oleate (PO) were tested as passivating additives to previously developed H2O2 and citric acid-based silica dispersions for the polishing of chemical vapor deposited Co films for interconnect applications. In comparison to TAZ and NLS, Co corrosion currents are similar to 1 to 2 order of magnitude lower (similar to 1-3 mu A cm(-2)) at pH 7 with PO and post-polish surface quality was much better. The galvanic corrosion currents between Co-Ti and Ti-TiN couples with PO were also very low (similar to 0.1 mu A cm(-2)), making the previously developed silica and citric acid-based dispersion, now containing PO, suitable for both bulk removal of Co (step I) and for planarizing Co/Ti/TiN structures (step II) with excellent selectivity while stopping on low-k dielectric. Langmuir adsorption isotherm model analysis showed that the standard free energies of adsorption values were similar to 40 kJ/mol for PO suggesting chemisorption. Fourier transform infra-red (FTIR) and attenuated FTIR spectroscopy data show bridging coordination between the carboxylate ligand of PO and the Co surface. (c) The Author(s) 2017. Published by ECS. All rights reserved.