Study on effect of complexing agents on Co oxidation/dissolution for chemical-mechanical polishing and cleaning process

The effect of complexing agents on Co oxidation/dissolution in alkaline solution was investigated for Co chemical-mechanical polishing (CMP) and post-CMP cleaning processes. The oxidation and dissolution properties of Co in a solution are greatly affected by complexing agents, which could influence the performance of Co CMP and post-CMP cleaning processes. Herein, three complexing agents, glycine, ethylenediaminetetraacetic acid (EDTA), and citric acid were studied. It was revealed that the complexing agents determined Co dissolution rate depending on the presence or absence of H2O2. Glycine showed a higher Co dissolution rate than EDTA and citric acid in the absence of H2O2, while EDTA showed the highest dissolution rate in the presence of H2O2. Negligible dissolution was observed with citric acid, regardless of the presence of H2O2. Electrochemical impedance and UV-Vis spectroscopies found that the difference in Co dissolution rates was related to Co oxidation rate and complexation capability of each complexing agent. Glycine showed a higher Co oxidation rate than EDTA, while EDTA had a much higher complexation capability than glycine. Citric acid exhibited the lowest Co oxidation rate and complexation capability, resulting in the slowest Co dissolution rate.