In this paper, the electrochemical behavior of copper in aqueous solutions containing phosphoric acid (H3PO4) is investigated to elucidate the role of H3PO4 in the Cu ECMP slurries. Aqueous solubility and potential-pH diagrams were constructed for copper-phosphate-water system. Good correlations were found between the diagrams and the experimental polarization data. It was found that H3PO4 might not able to sufficiently increase the solubility of copper alone. A complexing agent is needed to ensure the high solubility of copper, especially as the slurry pH and dissolved copper concentration increase. Specific conductance measurements revealed that phosphoric acid was the key constituent responsible for increasing the conductivity of the ECMP electrolyte. In situ electrochemical polarization experiments showed that the planarization mechanism during the ECMP process was similar to that observed in conventional copper CMP.
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