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This work focuses on the investigation of Co/Cu removal rate (RR) selectivity and reduction of galvanic corrosion associated with Co and Cu by using oxalic acid (weak acid) as the complexing agent and imidazole as an inhibitor in hydrogen peroxide (H2O2) and fumed silica-based slurry. The results obtained from a dissolution study, polishing experiments, and potentiodynamic polarization measurements revealed that the proposed chemistry can achieve a desirable Co/Cu RR selectivity and a significant decrease in corrosion potential of Co and Cu (pH 9) to be used in the semiconductor industry. The corrosion potential difference (CuEcorr - CoEcorr) was reduced to 12 mV by using 0.1 wt.% H2O2 + 0.02 M oxalic acid + 5 ppm imidazole solution at pH 9. Meanwhile, a removal rate of ~147 nm/min for Co and ~140 nm/min for Cu was achieved using the same composition in a fumed silica slurry which resulted in Co/Cu selectivity ratio of 1.05:1, which is acceptable for cobalt barrier and copper interconnect CMP. Based on Fourier transform infrared and ultraviolet spectra, the dissolution mechanism in the proposed chemistry is also discussed.

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Potentiodynamic polarization and electrochemical impedance measurements were employed to investigate the effect of acetic acid on the anodic dissolution of carbon steel in a CO2–H2S solution. Both polarization and impedance results unveil that the dissolution rate of carbon steel first increases and then decreases with an increase in acetic acid concentration. At lower concentrations of acetic acid, the corrosion rate increases due to the increase in cathodic current density. While the decrease in corrosion rate at higher acetic acid concentrations is attributed to the decrease in the anodic current density. The reaction mechanism of carbon steel dissolution in the CO2–H2S–acetic acid medium is elucidated along with the retrieval of kinetic parameters using the impedance data acquired at different overpotentials for various concentrations of acetic acid (1, 50, and 500 ppm). Further field emission scanning electron microscopy (FESEM) images confirm that the pitting corrosion occurs on carbon steel surface at higher acetic acid concentrations.