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 +1 412 381-3195 -- phone +1 412 381-1136 -- fax +1 412 656-3573 -- mobile davids@xactix.com -- e-mail www.xactix.com ---------- Original Message ---------- FROM: Aarthi lavanyaTO: "mems-talk@memsnet.org" 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