Abstract
Abstract 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.
Highlights
Chemical mechanical polishing (CMP) has been used as a global planarization technique since the 1990s, and it is currently widely used in the manufacture of ultra-precision surfaces, such as Si wafers and the Damascus interconnection structures of Cu in integrated circuits, computer disks and heads, etc. [1, 2]
We investigated the effect of tert-butyl hydroperoxide-sodium pyrosulfite ((CH3)3COOH-Na2S2O5) as the free radical initiator system for H2O2 slurry on the hard disk substrate abrasive-free polishing (AFP)
4 109 m d 2 t where: MRR- material removal rate, nm/min m- mass of material removed, g d- diameter of work piece, mm t- polishing time, min ρ- density, g/cm3
Summary
Chemical mechanical polishing (CMP) has been used as a global planarization technique since the 1990s, and it is currently widely used in the manufacture of ultra-precision surfaces, such as Si wafers and the Damascus interconnection structures of Cu in integrated circuits, computer disks and heads, etc. [1, 2]. In the traditional CMP process, there are chemical reactions between the slurry and the material surface to be polished, which form a layer of oxidation film. Due to the combined chemical and mechanical processes, the material surface can be planarized This leads to depression, erosion, and mechanical damage because of the abrasives [6−9]. Compared with the CMP process, in the abrasive-free polishing (AFP) process, the oxidation film is removed by the soft polishing pad without the abrasives. The use of Cu (II) [14] or potassium peroxydisulfate-sodium hydrogensulfite (K2S2O8NaHSO3) as catalyzers [15] in the H2O2 slurry promoted the decomposition of H2O2, and caused it to exhibit a much higher material removal rate (MRR); a better substrate surface was obtained compared to that of the H2O2 slurry under the same conditions after the AFP process. We investigated the effect of tert-butyl hydroperoxide-sodium pyrosulfite ((CH3)3COOH-Na2S2O5) as the free radical initiator system for H2O2 slurry on the hard disk substrate AFP
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