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Method to Determine Laser Texture Bump Height Using Avis Inspection Tool Disclosure Number: IPCOM000015610D
Original Publication Date: 2002-Aug-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 2 page(s) / 80K

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Method to Determine Laser Texture Bump Height Using Avis Inspection Tool


Laser zone texturing technology has been widely implemented in contact start/stop (CSS) disk drive systems. In laser zone texturing an annular area (typically 2-3 mm wide) is "roughened" (textured) by laser-produced micro-sized protrusions, or bumps, to provide a "take-off/landing" zone for flying head during start/stop operation. Laser texturing technique has been mainly applied to NiP-plated AlMg substrates before the final sputtered deposition of the magnetic layer onto the substrate.

To optimize the performance of a CSS drive for "stiction" and " durability", it is imperative to maintain a tight bump height specification for the textured zone. An in-situ Laser Texture Analyzer tool has been utilized to control the texturing process and to measure the average bump height on AlMg substrates, i.e., prior to the magnetic sputter process. At the processed level, i.e., finished disks, bump height monitoring has been performed on a sampling basis to monitor height shrinkage related to the wash and sputter processes.

This publication briefly describes the applicability of the AVIS optical surface inspection tool for monitoring the textured zone on a finished disk. This method can be appropriately used for measurement and process control at the substrate level as well.

AVIS Optical Inspection Tool

The AVIS inspection tool is a scatter-type laser based instrument for monitoring surface defects and contaminants on the finished disks at the end of the process line (AVIS can also be utilized for substrate surface inspection as well). As the AVIS focused probe beam impinges upon the disk surface, a portion of the incident light is scattered by contaminant particles, surface imperfections, and surface structural defects. The AVIS algorithm uses the intensity of the light scattered by a surface "defect" to characterize the defect by a corresponding "number of pixels". Predefined criteria for pixel counts is then used to "pass" or "reject" the disk under inspection.

A textured zone comprises a plurality of individual laser bumps. A laser bump causes light scattering as the AVIS probe beam impinges on the protrusion, therefore, interpreted as a surface defect, characterized by the corresponding "number of pixels". The characteristics of "V-shape" bumps lend themselves to the applicability of the AVIS...