Wet etch is isotropic when the substrate to be etched is largely or
completely isotropic in nature, such as glass. Some type of flouride
solution should do well. Depending on the type of resist you might want
to use a buffered oxide etch solution which comes either 13:2 or 6:1
from vendors and is known as "BOE".

Ed

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Yoshi Sakata
Sent: Thursday, April 03, 2008 10:28 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] Pyrex isotropic etching

Hi,

I'm looking for the isotropic etching method to cut grooves on a pyrex
wafer. The groove will have about 50um depth. I expect that the bottom
and side surface of the groove is smooth. Because I will put the Au
electrodes on those surface. Does someone have a good idea?