Tungsten CMP: Application of mixed potential theory to the tungsten/iodate system

Using potentiodynamic polarization, the rotating disk electrode technique, and solution analysis, the effects of pH and iodate concentration on the rate of tungsten (W) corrosion were investigated at the corrosion potential. Based on mixed potential theory, the corrosion current with and without abrasion was estimated. The estimated corrosion current was found to be anodic-process- controlled in the absence of abrasion. However, in the presence of abrasion, Tafel behavior was assumed to continue at the corrosion potential and the estimated corrosion current density was observed to be cathodic-process- controlled. As the pH decreased and iodate concentration increased, the corrosion current density increased. The calculated W corrosion rate was only a small fraction of the reported W polishing rate.