Status of Thinned Silicon

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Status of Thinned Silicon

• Bill Cooper
• Fermilab

(Layer 1)
(Layer 5)
VXD
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Thinned Wafer

• Ray Yarema received a 6 wafer which had been
  thinned to a nominal thickness of 20 µm by Disco.
• Disco conducted practice thinnings on three
  mirror wafers to learn machine settings.
• After that a wafer Fermilab provided was thinned.
• The wafer includes metallization layers of two D0
  Run IIb sensors.
• There are no implants, so these are not true
  sensors, but objects which could be suitable for
  other studies.
• The plan is to use the wafer for handling,
  wire-bonding, and thermal distortion studies.
• As part of those studies, we need to singulate
  the wafer, that is, to dice it into various
  pieces which have geometries of interest.
• We also need to learn to remove singulated pieces
  from the handling frame, to which the wafer is
  held with UV release dicing tape.
• Various web files on handling silicon can be
  found at http//d0server1.fnal.gov/projects/run2b/
  silicon/mechanical/cooper/ilc/fabrication/handling
  _thin_silicon_1.ppt

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Thinned Wafer

• Greg Sellberg has verified that the dicing saw he
  has should be suitable for dicing the wafer.
• In regards to dicing this wafer, the DAD320 that
  you currently have will have no problem of dicing
  this wafer.  It is a mechanically sound machine
  and should not give you a problem in dicing any
  wafer, especially one this thin. -- Disco
• Depth of cut repeatable to 1 µm
• Hogan Nguyen offered to investigate a UV source
  for releasing from the UV dicing tape.
• UV LEDs were proposed.
• A possible arrangement of 37 LEDs is shown on
  the next transparency.
• It should provide good uniformity of exposure
  across the 6 wafer.
• The required exposure is expected to be 0.5
  joule/cm2 at a wavelength of 254 nm.
• LEDs will require some study, since they
  typically provide a wavelength gt 362 nm.
• Other options will also be investigated.

4
Proposed UV Array
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Proposed Dicing Pattern
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Proposed Procedures
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Status

• We began investigating and gathering pieces in
  mid-September.
• Saw blades
• A determination was made that the purchase should
  follow normal channels.
• A Pro-Card order placed October 10 for five
  blades.
• Vacuum chuck
• Greg has a spare 6 diameter porous ceramic
  chuck.
• The University of Washington offered to make a
  chuck which would be matched to individual diced
  pieces.
• Marcel generated a requisition for UW ILC work
  October 3.
• The PO needs to be approved by the second floor.
• As of yesterday evening, UW had not received the
  PO.
• UV source
• Investigations are in progress.