Fundamental Study of Chemical--Mechanical Polishing Slurry of Cobalt Barrier Metal for the Next-Generation Interconnect Process

A chemical--mechanical polishing (CMP) slurry was developed for use in copper (Cu) damascene interconnects with cobalt (Co) barrier metal by optimizing the corrosion potentials and removal rate selectivities of Cu and Co. A passivation layer was formed on Co surface in an alkaline solution, while no passivation layer was formed in an acidic one even with benzotriazole. In the slurry of pH 10, corrosion potential of Co was the same as that of Cu, which indicates that no galvanic corrosion between Co and Cu could occur. Furthermore, a stable Cu/Co removal rate selectivity of 0.5 was obtained with the slurry.