CMP process optimization for improved compatibility with advanced metal liners

As copper interconnect structures are shrinking with each technology node novel metals other than PVD Ta(N)/Ta are being introduced as barrier materials. These materials act as seed enhancement layers and enable the Cu filling of the narrowest structures. However, the integration of such metals into the manufacturing of sub-35 nm wide Cu lines produces several challenges which need to be addressed. One of these challenges is the compatibility of the interconnect metals with the copper Chemical Mechanical Polishing (CMP) step. In particular, corrosion issues and Cu defectivity in the trenches need to be controlled. An evaluation of the compatibility of the CMP slurries with the new incorporated materials therefore becomes extremely important. Our work shows that by optimizing the CMP process and selecting compatible slurries, novel metals such as CVD Co (combined with a Ta(N) barrier) are promising candidates for the metallization of sub-35 nm lines.