Effect of Benzoyl peroxide/N, N-dimethyl aniline initiating system on material removal rate in abrasive-free polishing of hard disk substrate

Abrasive-free polishing has been used for nickel-phosphorus (Ni-P) coating hard disk substrates to achieve global planarization of topography with a low post-planarization slope. Benzoyl peroxide (BPO)-H₂O₂ slurry in abrasive-free polishing of hard disk substrate was developed in our previous work, but its material remove rate is relatively low. In this paper, N, N-dimethyl aniline is introduced to the BPO-H₂O₂ slurry and obtains a better polishing performances. The polishing experiments show that, by comparison with BPO-H₂O₂ slurry, the BPO/N, N-dimethyl aniline-H₂O₂ slurry can increase the material removal rate from 11.85nm/min to 19.23nm/min and reduce the surface roughness (Ra) from 12.08nm to 11.85nm for hard disk substrate. Moreover, the acting mechanism of BPO/N, N-dimethyl aniline-H₂O₂ slurry was investigated. The electron spin-resonance spectroscopy (EPR) analysis displays that the BPO/N, N-dimethyl aniline-H₂O₂ slurry provides higher concentration of the HO· free radical which improve the oxidizing ability of the surface of hard disk. The auger electron spectrometer (AES) analysis shows that the oxidization reaction occurs in the external layer of the substrate surface and the thickness of formed oxide film is about 3.75nm. Furthermore, electrochemical studies from polarization and impedance experiments exhibit lower current density and higher passive-film resistance, which proves the increase of oxidizing ability of the surface of hard disk. All the results indicate the introducing of BPO/N, N-dimethyl aniline can effectively improve polishing performances and imply that the BPO/N, N-dimethyl aniline initiator has a better application prospect in the future.