Electrochemical potential measurements during the chemical-mechanical polishing of copper thin films

A description is given of the mixed electrochemical potential measured in situ during the chemical-mechanical polishing of Cu. Potential measurements are indicative of the dissolution rate of Cu and of the equilibrium form of the polished Cu by-products. These measurements are used to explain the polish performance in several ammonia-based slurries. Specifically, the polish rate is shown to correlate with the potential and the change in potential during polishing. In addition, complexing of Cu ions with dissolved ammonia is discussed and shown to be an effective method for increasing the solubility of Cu ions in the slurry and thereby increasing the polish rate.