Chemical Mechanical Planarization of Ruthenium in Hydrogen Peroxide-Based Slurry

In this paper, chemical mechanical polishing behaviors of Ruthenium(Ru) in hydrogen peroxide (H₂O₂)-based slurry are investigated. The effect of the oxidizing agent and complexing agents on the corrosion behaviors are investigated by using electrochemical measurement and X-ray photoelectron spectroscopy. And the polished Ru surface is characterized by atomic force microscopy. Results show that the tightness and thickness of the passive film on the surface of Ru are related to the concentrations of CH₃COOH and H₂O₂. CH₃COOH can accelerate the anode reaction and enhance the chemical action of the slurry on the surface of Ru. The material removal rate (MRR) of Ru in slurries with CH₃COOH as complexing agent is higher than that of TEA or C₄H₆O₆. H₂O₂ at low concentration promotes the chemical corrosion ability to corrode Ru surface and increases MRR, the increasing of H₂O₂ concentration may promote the formation of a thick oxide film on Ru surface, which reduces the corrosion rate and the MRR at higher concentration of H₂O₂. The XPS results suggest that the atomic ratio of Ru to oxide is about 2: 3 and Ru is oxidized to Ru⁴⁺ and Ru⁸⁺ just after the immersion of Ru into the H₂O₂-based slurry with CH₃COOH because of the formation of RuO₂ and RuO₄ on the Ru surface. The roughness average (S_a) of Ru surface can be reduced from 33 nm to 6.99 nm after polished within 5 μm×5 μm area.