Study on Chemical-Mechanical Synergies in Polishing of Ruthenium

Ruthenium (Ru) is widely used in the manufacturing of integrated circuits due to its excellent properties such as low electrical resistivity and good step coverage. The Chemical Mechanical Polishing (CMP) of Ru has been extensively researched, with emphasis on the development of slurry to improve the material removal rate of Ru. The chemical-mechanical synergistic material removal mechanisms of Ru have not received in-depth investigation. To address this gap, CMP of polycrystalline Ru was carried out with polishing pads of different elastic modulus and slurries containing varying oxidizer concentrations. The experimental results demonstrated significant differences in grain boundary step heights under different polishing conditions. This paper suggests that the observed variations in grain boundary step heights during Ru polishing are the result of the interplay between oxide layer thickness (chemical action) and particle penetration depth (mechanical action). Thus, by elucidating the differences in experimental results, this paper reveals the material removal mechanisms associated with the chemical-mechanical synergy in Ru polishing.