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Use of Laser Pulse Generated Cavitation to Remove Glassy Skin Formed in Etch Pocket during Excimer Laser Ablation of N-58 Ceramic

IP.com Disclosure Number: IPCOM000115694D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 98K

Publishing Venue

IBM

Related People

Haba, B: AUTHOR [+3]

Abstract

Excimer laser of appropriate wavelength is used to produce by ablation an Air Bearing Surface with desired pattern of trenches in the N-58 ceramic base of the sliders used in the magnetic data storage files.

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This is the abbreviated version, containing approximately 52% of the total text.

Use of Laser Pulse Generated Cavitation to Remove Glassy Skin Formed
in Etch Pocket during Excimer Laser Ablation of N-58 Ceramic

      Excimer laser of appropriate wavelength is used to produce by
ablation an Air Bearing Surface with desired pattern of trenches in
the N-58 ceramic base of the sliders used in the magnetic data
storage files.

      This process leaves a partially cracked glassy film at the
bottom and side-walls of the trenches.  A finite probability exists
that this cracked glassy layer may, under temperature humidity
cycling, flake off and generate particles that will interfere with
the smooth flying of the sliders on the disk surface.  Presently,
ultrasonic cavitation is used to partially remove the weakened
portions of this glassy skin, however, it also simultaneously weakens
previously strong areas.  Ultrasonic cavitation is difficult to
localize and therefore is random in nature.  Use of ultrasonic
cavitation is, thus, like using randomly located Earthquakes to
remove only weak structures from, areas such as San Francisco.  It
cannot be done because such earthquakes will also weaken previously
strong structures.

      The method proposed is the use of cavitation generated by laser
pulses for the purpose of removing this glassy skin completely.  It
has been found that laser pulse generated cavitation is highly
localized  and occurs at solid liquid interface in the illuminated
areas only.  This method has been successfully used in removing such
glassy skin from the trench surfaces completely without causing any
significant and apparent damage to N-58 Air-Bearing Surface.

      Circular patterns of one mm diameter were first etched on a
N-58 sample using a hyperex KrF excimer laser at 248nm.  To provide a
uniform etching, the laser beam was first directed to a 2-dimension
beam homongenizer.  The output from the beam homongenizer was then
focussed onto a dielectric mask with a circular transparent pattern
of 2mm in diameter.  A 4-element projection lens formed a image of
the laser illuminated pattern onto the N-58 sample with a 2X
reduction in size.  The laser was nominally operated at  30Hz and the
fluence at the sample is approximately 1.5J/cm2.  Such laser etched
patterns have a thin crust on the surface with many microcracks.  The
objective of this work is to remove the cracked layer using laser
induced cavitation under water.

      A Copper Vapor Laser (CVL) was shone on the DI water submerged
sa...