Nathan,
If the design will let the silicon sag a lot, say 1 mm, when pulled by the
vacuum, it will break.
Usually the design is such that the oring protrudes only few tenths of a mm
above the surface so the wafer will be pulled but won't break.
Many chucks don't even have an oring. Just vacuum slots, radial and
concentric. Since the wafer is very flat, the will be minimum or close to
zero leakage between the wafer and the chuck.
In any case, you want to add a liquid trap between the chuck and the pump to
allow for resist or solvents that are sucked into the line to stay there so
they don't reach the pump.

Good luck
Shay

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Nathan
McCorkle
Sent: Friday, December 06, 2013 9:07 PM
To: mems-talk
Subject: [mems-talk] Vcuum chuck pressure? How to prevent wafer breaking?

I am trying to build a vacuum chuck for spinning, and can't figure out if a
common laboratory roughing vacuum pump would break a silicon wafer. There is
some distance from the center of the chuck to the O-ring(s), but how much?
And the vacuum will never apply more than
14.7 PSI (at sea level), right?

This mentions silicon surviving >10000 PSI, but is that an ingot or rod or
wafer, I can't tell.
http://www.me.berkeley.edu/~lwlin/me119/papers/paper9.pdf

--
-Nathan
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