Achieving equivalent removal of Ta and Ru via controlling oxidation for chemical mechanical polishing of advanced barrier layer

With the feature size of integrated circuits decreasing, Ta/TaN barrier layer gradually evolves to Ru/Ta, posing a significant challenge to planarizing the heterogeneous surface. This study used the oxidant IO4− to tune the material removal rate (MRR) selectivity between Ta and Ru. It is revealed that as the IO4− concentration increases, Ta and Ru have distinct MRR changing trends. The Ta MRR almost keeps the same level, while the Ru MRR gradually increases. The two MRRs are nearly equivalent with about 0.04 wt% IO4−, helping planarize Ru/Ta. For the mechanism, IO4− affects the MRRs of Ta and Ru mainly through influencing corrosion (oxidation) of corrosive wear in metal CMP. In the slurry containing IO4− and at alkaline pH, Ta can be oxidized to Ta2O5 and Ta–OH complexes. Interestingly, the surface oxide film remains stable as the IO4− concentration increases, resulting in an almost unchanged MRR. Ru can be oxidized to RuO4−, and then to RuO2 and RuO3. Notably, the corrosion of Ru is significantly enhanced by IO4−. Consequently, more Ru oxides are formed, and meanwhile, the surface becomes more porous, leading to an increasing MRR. This study provides a promising method for planarizing heterogeneous surfaces via controlling oxidation in CMP.