Effect of Potassium Iodate-Based Slurry for Polishing of Ruthenium (Ru) as Advanced Interconnects

With the reduction of technology nodes to less than 10 nm, ruthenium (Ru) has emerged as a viable replacement for copper (Cu) for back-end-of-the-line (BEOL) interconnects. Good surface uniformity while maintaining an appropriate thickness of Ru is required during the fabrication process, which can be achieved by employing the chemical mechanical planarization (CMP) process. However, a crucial step in the CMP process is to attain reasonable removal rates of high-mechanical-strength and chemically inert metals such as Ru. Hence, this study investigates a competent CMP slurry comprising potassium iodate (KIO 3 ) as an oxidizer and fumed silica as an abrasive for polishing Ru. The polishing results show that adding KIO 3 to fumed silica modifies the silica particles, thereby enhancing the removal rates of the metal. thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis) characterization confirm the modification of the silica particles by KIO 3 as an oxidizer. The studies reveal that the abrasive concentration usage was reduced to 60% due to silica modification. The surface morphology of the treated metal surface was evaluated using field emission scanning electron microscopy (FESEM). No adsorbed contamination or pitting is observed on the metal surface. The inhibition effect of 1,2,3-benzotriazole (BTA) was investigated in detail by performing potentiodynamic polarization experiments. The nature of the metal dissolution in KIO 3 was investigated by examining the effect of solution temperature on the etch rates. The thermodynamic process of the system was found to be endothermic in nature, and the dissolution followed an associative mechanism. The results reported in this paper reveal that the proposed slurry can be used to significantly improve Ru polishing efficiency and provide desired selectivity without compromising the surface quality of the metal.