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Microscopic Asperity and Depression Standard for Magnetic Recording Disks and Method for Making the Same Disclosure Number: IPCOM000014311D
Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2003-Jun-19

Publishing Venue



Described is a standard for the calibration of tools used to screen magnetic recording disk substrates for the presence of defects that might cause magnetic drop-out errors or glide height errors. The novel feature of this standard is the fabrication of microscopically small and precisely defined asperities and depressions in a regular orderly array with well-controlled heights, depths, and shapes by means of deposition and milling with the focused ion beam (FIB) tool. The calibration standard extends the range of simulated defects beyond those that are currently available, thus making it possible to screen substrates for ever smaller microscopic defects that are becoming increasingly more deleterious as magnetic recording technology advances to higher recording densities. A preferred embodiment of the invention utilizes the features described as follows. The calibration standard employs a magnetic recording disk substrate made from glass, Si, and/or NiP coated aluminum/magnesium alloy. The substrate has fabricated on it a rectangular or square array of nominally square pits and/or bumps; the square pits and/or bumps are arranged with a nominal pitch between pit edges and/or bump edges of 200 microns, edge-to-edge. Also, the pits and/or bumps have nominally square lateral dimensions from 1.6 x 1.6 microns to 0.2 x 0.2 microns, and have, respectively, depths or heights from 100nm to 5nm. These pits and/or bumps are fabricated by means of FIB, wherein the pits are fabricated by milling with a well-collimated and precisely rastered ion beam that is rastered in a pattern of the above specified dimensions, and wherein the bumps are fabricated by depositing a metallic layer of a Ga doped W alloy, or a Ga doped Pt alloy by pseudo-chemical vapor deposition with a similarly well-collimated and precisely rastered ion beam in a pattern of the above specified dimensions. The calibration standard is also provided with a set of alignment marks or scribe marks arranged on a diameter of the disk at a precisely determined distance from the array of pits and/or bumps and visually discernible by the naked eye, whereby the microscopic array of pits and bumps can be more easily located under a detector of a screening tool. Another embodiment of a microscopic asperity and depression standard comprises a disk like that above, but where the pits and/or bumps are replaced by trenches and/or ridges, respectively. Finally, the above embodiments should not be construed to preclude features with other shapes or aspect ratios known to those skilled in the art that might be suitable for calibrating a disk substrate screening tool. 1