Sudesh,
       A common technique is to treat the mask first with a hydrophobic
silane coating. Using the correct equipment and chemistry, a coating
that has a contact angle of 120 degrees to water and is impervious to
normal processing can be created. This means the mask is first what I
can only describe as resistaphobic for hundreds if not thousands of
contacts.  Then when cleaning is necessary water does not cling to the
surface and there are no water drops.

Bill Moffat, CEO
Yield Engineering Systems, Inc.
203-A Lawrence Drive, Livermore, CA  94551-5152
(925) 373-8353

bmoffat@yieldengineering.com

www.yieldengineering.com

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Sudesh Bhagwat
Sent: Thursday, September 06, 2007 5:16 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Photomask cleaning problem

Hello all,
I am currently using a 7"x7" photomask for my work.I had procurred the
Photomask blank  (Cr blank) from a company called as Telic in USA.
To clean the photomask I use 70% Sulphuric Acid +30% Hydrogen Peroxide
(Pirana solution). I dip my photomask in this solution for 7 minutes and
then clean in thoroughly in DI water.
Can anyone suggest whether the procedure is correct and do I have to
something else to clean the mask. After Cleaning the photomask, the Cr
side looks pretty much clean, but the glass side of the photomask still
has stains/spots. I suspect that the stains/spots are not on the glass
side, but inside the glass and hence I would like to ask whether anyone
has experience in using photomask blanks from Telic.
Regards,
Sudesh