Hi Ganesh,

One way is to use a multilayer of low stress nitride (LSN).

1. Deposit the first layer of LSN.
2. RIE etch the LSN to open up both trenches.
3. Then deposit another layer of LSN.
4. RIE etch the LSN to open up the larger trench leaving the smaller one
protected.
5. Etch the sample in KOH for the first 150 um.
6. Then do a flat RIE etch to remove the entire second layer nitride while
leaving the first nitride layer intact.
7. Then you can do another KOH etch to etch the remaining 75 um.

This should get you the two different sized trenches.  Good luck.

Phil Tabada
UC Davis PhD Candidate


>From: Ganesh Iyer 
>Reply-To: General MEMS discussion 
>To: mems-talk@memsnet.org
>CC: giyerr@yahoo.com
>Subject: [mems-talk] Etching?
>Date: Thu, 18 Dec 2003 17:50:03 -0800 (PST)
>
>Dear MEMS team..
>
>Is there any way of making two V grooves (one smaller and one bigger)
>touching each other? smaller one has dimension of 75 microns width and
>larger has dimension of 225 microns wide.. I mean there has to be no gap
>between the two V groove and smaller V groove opens up to a larger V groove
>like a channel..  I am trying the wet etching using some techniques like
>giving a small gap between the two V grooves and etch it in KOH. but not
>working.. is there any other techniques anyone can suggest me or any
>suggestions in wet etching by which i can get the desired results?
>
>thanks
>ganesh
>
>
>
>Ganesh R. Iyer
>(H)    607 729 9499
>(Lab) 607 777 4969
>
>
>
>---------------------------------
>Do you Yahoo!?
>Free Pop-Up Blocker - Get it now
>_______________________________________________
>MEMS-talk@memsnet.org mailing list: to unsubscribe or change your list
>options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
>Hosted by the MEMS Exchange, providers of MEMS processing services.
>Visit us at http://www.memsnet.org/

_________________________________________________________________
Enjoy the holiday season with great tips from MSN.
http://special.msn.com/network/happyholidays.armx