Potassium Periodate-Based Solutions for Minimizing Galvanic Corrosion at the Cu-Mn Interface and for Polishing the Associated Cu Interconnect Structures

One of challenge associated with a self-forming Mn barrier for Cu interconnects in sub-22 nm devices is galvanic corrosion that can occur at the Cu-Mn interface during chemical mechanical planarization. In the present work, it is shown that an aqueous solution of sucrose, BTA and KIO4 is able to reduce the corrosion potential gap between Cu and Mn to ∼0.01 V at pH 10 and lower the galvanic currents significantly. We discuss the role of the additives and the inhibiting film that can be formed at the interface of the bimetallic system in this solution. Polishing results for Cu and Mn using a silica-based slurry formulated with this solution are also presented.