Voltammetric current oscillations due to general and pitting corrosion of tantalum: Implications for electrochemical–mechanical planarization

Anodic corrosion of Ta is examined for potential applications in electrochemical–mechanical planarization (ECMP) of diffusion barriers. This strategy involves electro-oxidation of Ta in the presence of NO3- (or Br−) to form mechanically weak surface-oxide films, followed by mechanical removal of the latter. The voltammetric currents exhibit oscillatory behaviour with frequencies that are signature attributes of localised pitting by Br− or general surface corrosion by NO3-. SEM, voltammetry, and impedance spectroscopy are used to probe these corrosion mechanisms. Apart from their relevance for ECMP, the results also address certain fundamental aspects of pitting and general corrosion of valve metals.