Abrasive-free polishing of hard disk substrate with H₂O₂-C₄H₁₀O₂-Na₂S₂O₅ slurry

The effect of tert-butyl hydroperoxide-sodium pyrosulfite ((CH₃)₃COOH-Na₂S₂O₅) as an initiator system in H₂O₂-based slurry was investigated for the abrasive-free polishing (AFP) of a hard disk substrate. The polishing results show that the H₂O₂-C₄H₁₀O₂-Na₂S₂O₅ slurry exhibits a material removal rate (MRR) that is nearly 5 times higher than that of the H₂O₂ slurry in the AFP of the hard disk substrate. In addition, the surface polished by the slurry containing the initiator exhibits a lower surface roughness and has fewer nano-asperity peaks than that of the H₂O₂ slurry. Further, we investigate the polishing mechanism of H₂O₂-C₄H₁₀O₂-Na₂S₂O₅ slurry. Electron spin-resonance spectroscopy and auger electron spectrometer analyses show that the oxidizing ability of the H₂O₂-C₄H₁₀O₂-Na₂S₂O₅ slurry is much greater than that of the H₂O₂ slurry. The results of potentiodynamic polarization measurements show that the hard disk substrate in the H₂O₂-C₄H₁₀O₂-Na₂S₂O₅ slurry can be rapidly etched, and electrochemical impedance spectroscopy analysis indicates that the oxide film of the hard disk substrate formed in the H₂O₂-C₄H₁₀O₂-Na₂S₂O₅ slurry may be loose, and can be removed easily during polishing. The better oxidizing and etching ability of H₂O₂-C₄H₁₀O₂-Na₂S₂O₅ slurry leads to a higher MRR in AFP for hard disk substrates.