Controlling the Galvanic Corrosion of Copper during Chemical Mechanical Planarization of Ruthenium Barrier Films

A specific challenge for integrating Ru as barrier in Cu interconnect structures is the galvanic corrosion of Cu that occurs during chemical mechanical planarization (CMP). The present work reports an electrochemical approach to mitigate this problem through judicious engineering of CMP dispersions using benzotriazole and ascorbic acid as selective anodic and cathodic corrosion inhibitors for Cu and Ru, respectively. The experimental background slurry employs KIO 4 at p H = 9, where the removal rates of both Ru and Cu are reasonable and the formation of RuO 4 is avoided.