Hi Aarthi,

>From your description I think even more that XeF2 would be the best solution.
It will not attack either your SU8 or your metal wires. It is a dry chemical
etch (no plasma) which will help avoid a host of other problems. XeF2 is a bit
slow for etching a whole wafer so you might want to use a faster etch to get
really close and then use XeF2 to finish off the job.

Regards
David

____________________________
David Springer, Ph.D.
XACTIX, Inc.
2403 Sidney St - Suite 300
Pittsburgh, PA 15203
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---------- Original Message ----------

FROM:      Aarthi lavanya 
TO:        "[email protected]" 
CC:
DATE:      Sun, 17 Apr 2011 22:31:22 -0400

SUBJECT:   [mems-talk] Si Etch with KOH

Thanks for the suggestions. I think I have not made myself quite clear.

I am not releasing Su-8 structures, I am transferring the metal
structures on Si to Su-8.( For example I have wires made of Cr/ Ag or
Cr/ Au sitting on Si wafer. Then i have an layer of Su-8 on top of the
structures. So the metal structures are sandwiched between Su-8 on one
end and Si on the other, the idea is to have the wires transferred on
Su-8 layer).  I had tried different methods for releasing the
structures,like having a Ti or Cr layer covering the entire wafer and
then try to etch away Cr or Ti,but the etchant couldn't go all the way
to the middle of the wires might be because of surface tension. So I had
to resort to etching the whole wafer.

Cheers
A