(169d) Aqueous Electrochemistry of Ta in HF

Ta is an active metal that typically oxidizes at all potentials within the electrochemical window of water. However, the native oxide of Ta can be dissolved in aqueous HF due to the formation of Ta heptauoride. Ta electrochemistry is studied in aqueous HF at several different concentrations using both cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Direct Cu electrodeposition onto Ta rod can be accomplished, but adhesion is poor. This is believed to arise from an interfacial Ta oxide or fluoride film, as evidenced by low frequency inductive loops seen with EIS. Ta electrochemistry in HF is also studied in the presence of several different polymers to assess their ability to prevent the growth of Ta oxide. This is critical to the development of Ta chemical mechanical planarization (CMP) slurries that operate at low downforce.