There's a paper put out called "Anisotropic etching of surfactant-added TMAH
solution" (IEEE 0-7803-5194-0/99/$10.00 1999) In which the author (Masayuki
Sekimura) describes adding a detergent called NCW-601A (Wako Pure chemical
company) to the etch to reduce the convex corner undercut.

I tried it out a few years back, and found that it did slow down the convex
corner attack for a time, but once the fast etch planes on the corner were
revealed, they etched at the same rate.

So using this stuff will help you if you are doing shallow etches ( < 200
microns), but not for more than that.

I don't know if that's applicable to IPA.

David Nemeth
Senior Engineer
Sophia Wireless, Inc.
14225-C Sullyfield Circle
Chantilly, VA
-----Original Message-----
From: mems-talk-bounces+nemeth=sophiawireless.com@memsnet.org
[mailto:mems-talk-bounces+nemeth=sophiawireless.com@memsnet.org]On
Behalf Of wez6@lehigh.edu
Sent: Friday, October 03, 2003 9:21 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] KOH IPA Undercut



Dear All,

I am a new-comer of MEMS area. I am suffering from KOH etching problem. My
outside convex edge has been etched to be round because I forget corner
compensation when I draw my design. I do not have any budget to order a new
mask. Is KOH+IPA will help me? What is the recipe? I am also confused what
the
undercut compensation really meant in some literature.

Your help is highly apperciated.

Lydia



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