The Si:SiO2 etch rate selectivity of KOH increases with both decreasing
temperature and decreasing concentration.  You might try reducing the
temperature to 60 degC and the concentration to 20%.  If the etch rate
is too low for your needs, you can increase the SiO2 thickness.

Roger Shile

-----Original Message-----
From: mems-talk-bounces+rshile=nanoink.net@memsnet.org
[mailto:mems-talk-bounces+rshile=nanoink.net@memsnet.org] On Behalf Of
mahdi bagheri
Sent: Monday, June 14, 2004 7:34 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Etching Problem

Hello,

I want to etch silicon using SiO2 mask. At the
temperature of 85 (C), after 75 minutes, KOH attacks
to the SiO2 mask. The etchant solution is water: 80
cc, Isopropyl alcohol: 20 cc, koh: 30 gr. What can I
do to etch silicon?

Regards,
Mahdi Bagheri




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