I would try to mount the front side of the wafer to a glass slide (an old
mask works well) via a melted wax (carnauba from Strahl & Pitsch, Inc. works
well) and etch at with KOH at a low temperature (~65 C).
This can be done by placing the glass slide on a hot plate, melting the wax
on the glass slide, then placing the wafer (front side down) on the melted
wax...once removed from the hot plate, the wax will solidify. The glass
slide/wafer combo is then placed in the KOH bath. This will take longer,
but will protect the front side adequately. If you increase the
temperature, the wax will melt and the wafer will slide off of the glass
slide. After etching, you can remove the wafer just like you mounted
it...heating it on a hotplate. The remaining wax on the wafer will come off
via a piranha etch.
We routinely employ this technique for thinning back wafers to stop on a BOX
of an SOI or a nitride membrane.
********************************************
Mark Sheplak
Assistant Professor
Interdisciplinary Microsystems Group
Department of Aerospace Engineering,
Mechanics, & Engineering Science
227 Engineering Building
PO Box 116250
University of Florida
Gainesville, FL 32611-6250
(352) 392-3983
(352) 392-7303 FAX
[email protected]
www.img.ufl.edu
********************************************
-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Ralph Jih ()uD_5X)
Sent: Thursday, December 13, 2001 6:54 AM
To: [email protected]
Subject: [mems-talk] How to protect the PZT thick film in KOH etchant?
Dear MEMS colleagues,
Does any one know how to protect the PZT thick film(about 30um) in KOH
ecthant?
One side of the wafer is the PZT pattern,and the other side is ecthing
pattern.
I have tried some methods to avoid it, but fail:
1. use nobal metal (Au) to protect PZT --> too expensive, and the Au
will be etched.
Its surface
profile is like the moon surface.
-->NG.
2.use thick PR to protect --> PR will be lifted.
--> NG.
3.use jig to protect PZT --> use two o-rings to protect the wafer and
locked by screw.
when the thickness of the wafer
is thin during the ecthing process,
the wafer will break.
--> NG.
Can anyone give some suggestions to solve this problem?
I will appreciate your response.
Ralph
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