Reduction Characteristics of Iodate Ion on Copper: Application to Copper Chemical Mechanical Polishing

Potentiodynamic and potentiostatic polarization, and the rotating disk electrode technique were used to study the reduction characteristics of iodate (IO₃ ^–) ion on copper (Cu). Depending on the relative concentrations of IO₃ ^– and H⁺ two pH regimes were observed. The cathodic current in the first regime (pH > ,3) was controlled by H⁺ diffusion from the solution to the metal surface. In the second regime (pH > 3 and up to 10^–2 m IO₃ ^– concentration) the cathodic current was found to be under mixed control, involving reaction control via the electrochemical reduction of IO₃ ^– and transport control via the diffusion of I₂(aq). It was concluded that IO₃ ^– was an effective oxidant for Cu chemical mechanical polishing (CMP) with strongly acidic (pH < 3) slurries but it was not convenient reagent as an oxidant for Cu CMP with weakly acidic (pH > 3) slurries.