In Situ Study of Mechanical-Electrochemical Interactions during Cobalt ECMP

The electrochemical and tribological performance of cobalt during electrochemical-mechanical polishing (ECMP) was investigated in situ. Effects of polishing conditions such as applied loads and rotating speeds on frictional behavior and potentiodynamic polarization were studied. Results showed that the friction coefficient decreased slightly with the increase in applied load and polishing speed indicating the boundary lubrication regime during cobalt ECMP. The corrosion current declined firstly and then increased with the increase in mechanical power input. Further analysis revealed that the cobalt surface electrochemistry was interrelated to mechanical impact and corrosive environment, and it is not simply a linear relationship. The synergy of mechanically induced material removal and oxidation in the polishing process depends on the mechanical power and electrochemical reaction. This finding is beneficial to uncovering the mechanism of cobalt ECMP and guiding the process optimization.