Ravi,
The undercutting of convex edges (i.e. outside corners)is one of the
fundamental limitations of the anisotropic wet-etching process. It is a
matter of crystallography, not the specific proces you are using. A number
of authors have achieved some succes in reducing this effect through the
addition of compensation features to the etch mask, although these can be
cumbersome. The book by Madou has some excellent references on this topic,
and is probably your best starting place. Good luck!

Regards,
Barry D. Wissman, Ph.D.
MEMS Process Manager
Nanovation Technologies, Inc.
[email protected]
www.nanovation.com


-----Original Message-----
Message: 1
Date: Sun, 16 Sep 2001 14:24:23 -0700 (PDT)
From: shankar 
Reply-To: shankar 
cc: [email protected]
Subject: [mems-talk] Problem of  Undercut

Hi everybody,
 i am making some v-grooves in silicon, and with good suggestion form this
discussion group,i was able to  settle the cleaning problem after wet
silicon etching.
Now my problem is the UNDERCUT. Basically at convex edges i have problem
that the feature instead of being right angled becomes rounded.i use KOH
at 80 deg cel. for etching silicon. how do one take care of this effect?
Regds
Ravi Shankar
Semiconductor Complex Ltd.,
India.