CMP of hard disk substrate using a colloidal SiO2 slurry: preliminary experimental investigation

With magnetic heads operating closer to hard disks, the hard disks are forced to be ultra-smooth. At present, chemical–mechanical polishing (CMP) has become a widely accepted global planarization technology. In this paper, the effects of SiO2 particle size, and the contents of SiO2 particle, oxidizer and lubricant additive in the prepared slurry, as well as pH value of the slurry, on the polishing performances in the CMP of hard disk substrates with nickel–phosphorous plated were investigated. Results indicated that the average roughness (Ra) and the average waviness (Wa) of the polished surfaces as well as material removal amount were much dependent on all of the factors above. For comparison, CMP of hard disk substrates with a kind of commercial SiO2 slurry was conducted under the same polishing conditions. Based on Auger electron spectrogram (AES) examinations of the chemical changes in the polished surfaces with the prepared slurry, the CMP mechanism was deduced preliminarily.