Try using TMAH.  The undercuts worse, but it doesn't attack SiO.  For a
simple pattern, you can compensate the mask for the expected undercut.

David Nemeth
Senior Engineer
Sophia Wireless, Inc.

-----Original Message-----
From: guda reddy
Subject: SPAM-LOW: [mems-talk] SiO2 As a Mask

      Thank you guys for replying to my previous mail. What iam trying to do
was to make use of the silicon wafers with the grown oxide layer to
fabricate deep v-grooves using KOH. As you all know that one micro thick is
not sufficent enough to make deep grooves. I can go a head and change the
mask to silicon nitride, but before doing that i wanted to know why can't we
grow thicker oxide layers and use it for deeper grooves. I am trying to look
for some books or papers that gives me some solid proof that i have change
the my mask. If any of you guys can mention the books or papers that i am
looking for would be really helpful and i would really appriciate for your
help.