CMP process development for Cobalt liner integration at the 28-nm-node

Advanced liner materials are crucial for optimizing and further shrinking of integrated circuits´ interconnects. For next generation devices there is a focus on Cobalt (Co) and Ruthenium (Ru) [1]. Besides the challenges to deposit such materials, new chemical-mechanical polishing (CMP) process compatibility is needed. Especially Co introduces a bunch of new requirements. To reach the advantages of improved step coverage and lowered electrical resistivity compared to Tantalum nitride (TaN) [2] a complete change in consumables is needed to prevent Co from corrosion. Different CMP consumables are tested in a newly established 28 nm Co integration flow with special focus on corrosion properties and electrical performance. Starting from a standard TaN/Ta barrier process the corresponding consumables are systematically changed from non- Co compatible to Co compatible alternatives. Eventually the polishing steps are tuned to meet the integration requirements.