Hello Everyone,

I would like to thank everyone that replied to my question regarding
measurement of bonded silicon wafers.  If you're interested in the
responses, I've listed the various topics below along with the option I
finally used.

1. Optical microscope- Using a calibrated stage, focus across the wafers.
Difficulties- stage that holds a wafer on edge, need to make hole through
wafers otherwise, hard to determine focus through a hole.

2. FTIR in resonance.  Respondents indicated useful for below ~ 200
microns.

3. Micrometers- useful only if you have offset wafers or can remove a
piece of one.

4. KOH etch of hole to oxide, measurement of triangular base or focus on
planes.  Again, difficult to focus if contrast is low and no features on
surfaces, need for etching and photoresist.

5. Laser resonance.  Use of laser beam pulse to excite acoustic wave
through films, echos at interfaces return to surface and are read by
another pulse.  Monolayer accuracy.  Unfortunately, works only for ~3-5
micron films.  Great for interconnects, bad for bulk.

6. Interferometer.  By chance received mailing from Filmetrics, San Diego,
CA that has fiber optic system that can measure up to 50 microns in
thickness down to a few namometers.  They're still working on a system for
polishing machines.  Would be great if they had it today.

7. Final choice:  Advanced Coating Technologies, Radford, VA will dice
small flat and profile piece with submicron accuracy.  Relatively cheap
and minimally destructive.



Thanks again for all of your help.

Mike

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Michael H. Beggans
New Jersey Institute of Technology (NJIT)
[email protected]
973-642-7738 voice
973-596-5794 fax