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 IO 4 − to tune the material removal rate (MRR) selectivity between Ta and Ru. It is revealed that as the IO 4 − 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% IO 4 −, helping planarize Ru/Ta. For the mechanism, IO 4 − affects the MRRs of Ta and Ru mainly through influencing corrosion (oxidation) of corrosive wear in metal CMP. In the slurry containing IO 4 − and at alkaline pH, Ta can be oxidized to Ta 2 O 5 and Ta–OH complexes. Interestingly, the surface oxide film remains stable as the IO 4 − concentration increases, resulting in an almost unchanged MRR. Ru can be oxidized to RuO 4 −, and then to RuO 2 and RuO 3. Notably, the corrosion of Ru is significantly enhanced by IO 4 −. 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.