Chemical-mechanical polishing of Ni-P plated AlMg alloy substrates for high-density perpendicular magnetic recording

摘要

Chemical-mechanical polishing (CMP) has become a primary method for the planarization of hard disk drive (HDD) substrates. With the flying height of magnetic head operating closer to the disk surface and the application of high areal density perpendicular magnetic recording, the disk surface is required to be ultra-smooth. In this study, the velocity field and the polishing track on the disks have been simulated, and their effects on material remove rate (MRR) and surface parameters are also discussed. The effects of the polishing setup and the resulting velocity field are also experimentally explored by using a SPEEDFAM-16B-4M polishing machine. It is found that velocity field difference of upper and lower side of a disk has an import effect on the A and B side difference of material remove rate (MRR), flatness, and head media surface Critical waviness. The mechanical effects of two kinds of slurries with different abrasive size distribution on the polishing properties and surface parameters are also studied. An ultra-smooth surface has been achieved with both Slurry I and Slurry II. Average AFM roughness (Ra) is about 0.11 nm for Slurry I with broad abrasive size distribution and about 0.09 nm for Slurry II with narrow abrasive size distribution. AFM results also found that the disks polished with Slurry I had some very shallow scratches which were not found on the disks polished with Slurry II.