The synergy and DFT study of TT-LYK and potassium oleate on chemical mechanical polishing of cobalt in alkaline medium

This work was aimed at elucidating the synergy of the two inhibitors, TT-LYK and potassium oleate (PO), on cobalt (Co) in alkaline medium. Potentiodynamic tests, surface topography measurements, contact angle measurements and the single frequency EIS results revealed that the combination of TT-LYK and PO provided better Co protection. The adsorption of TT-LYK as well as PO on the Co surface fitted Freundlich and Langmuir adsorption isotherm models, respectively. X-ray photoelectron spectroscopy (XPS) revealed that once TT-LYK and PO are mixed together, the inhibitor molecules adsorbed on the Co surface are thicker and stronger. Density-functional-theory (DFT) calculations were employed to clarify the adsorption and bonding mechanism between the oleate and Co surface from an atomic level. Finally, the polishing experiment proved that the slurry consisting of 5 wt% silica abrasives, 0.6 wt% H2O2, 1.2 wt% potassium tartrate, 300 ppm TT-LYK and 1.5 mM PO yielded a removal rate of Co film of ~331.1 Å/min at pH 9, which met the requirements of chemical mechanical polishing (CMP) of the Co barrier liner.