Hi Chris,

If you have the opportunity to cover your frontside with SiN or TiN would be
the best solutions otherwise you can realize (and this is efficacious and a
low cost solution) a wafer support in teflon.This support is made ia way
that the frontside of the substrate is completely cover and protect. In the
past i have realized Coplanar Wave Guide Grounded (CPWG) on 400um thikness
Si substrate <100>oriented and for the realization of via holes on the wave
guide i have used all the three sulotion previously mentioned, in particula
the support in teflon is a good solution if you don't have the necessary
equipment for the realization of SiN or TiN. If you want i can send you the
scheme of my wafer support in teflon.

On this site you can also find some information for you problem.
http://www.ee.byu.edu/cleanroom/KOH.phtml

Hope you find this helpful.
Good luck for all.
Best Regards

Dr.Andrea Lucibello
Young Researcher
CNR - Istituto per la Microelettronica e Microsistemi
Area della Ricerca di Roma 2 - Tor Vergata
Via del Fosso del Cavaliere, 100 - 00133 Roma
Tel +39 0649934577 (Office)
Tel +39 0649934531   (Laboratory)
Mobile +39 3348314970

----- Original Message -----
From: "Chris P. Park" 
To: 
Sent: Monday, March 23, 2009 11:11 PM
Subject: [mems-talk] KOH - backside etch - frontside protection


Hi all,

I'm planning on a process where I want to create membranes in a KOH etch
from the back side but the front-side is already structured and must remain
dry. I want to control the membrane thickness (~18µ) optically. Does anyone
have experience with such a process or knowledge on the equipment I would
need?