Compensation structures can be added to the mask layout to decelerate the
faster etching planes [(411) as suggested by some authors] and prevent
corner undercutting. The dimensions of the compensation structure depend on
the concentration of etchant and some critical etch ratios. Some good
references for corner compensation schemes are:
1. Mayer et al, J.Electrochem. Soc.,(1990),137(12), 3947
2. Sandmaier et al, IEEE Transducers'91, (1991),456-459
3. Enoksson, J. Micromech. Microeng. (1997),7,141-144

Kunal Vaed
Passives Integration
Silicon Germanium Technology
IBM Microelectronics
Hopewell Junction, NY 12533




************************************************************ 
Eh
bien - Dans un monde tellement laid
La Beauté, c'est la seule véritable protestation
>Ah, in such an ugly world
Beauty, the only real protest
************************************************************


>From: "Wissman, Barry" 
>To: "'[email protected]'" 
>Subject: [mems-talk] RE: mems-talk digest, Vol 1 #47 - 4 msgs
>Date: Mon, 17 Sep 2001 17:24:19 -0400
>
>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.
>
>
>
>
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