Hello Dr. Sudesh S Bhagwat,

I have copied an old email from Bob Henderson, a regular contributor to
this forum, on a response to a similar question years ago.  Try it and
see if the spots go away.  It is important that the exothermic reaction
complete before dipping the mask.  Otherwise you may etch the chrome.
You may have already.


"I use an HSO4+H2O2 at 5:1,allow the exothermic reaction to cool down to
at least 90 Degrees C then apply heat if available. Soak mask for 5
minutes at 90 Degrees and remove and place in a warm 50 degrees C beaker
of di water. This will prevent thermal shock and possible breakage of
mask. Rinse to purity in di water and dip in IPA. Remove slowly and blow
dry with Nitrogen gun. Bob Henderson"

Best of Luck,

Mike Cain


-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Sudesh Bhagwat
Sent: Thursday, September 06, 2007 8:16 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