Hi Jack,
It should be quite high depending on the temperature.
5% TMAH at 85 C etches single crystal silicon with the
rate of 0.6 - 0.8 um per minute and amorphous silicon
will go much faster.
As for masking material, Silicon oxide or silicon
nitrides are quite fine, but you will get other issue
such as sticking of your released layer to your
substrate. That is why you might consider to do dry
etching by vapors of XeF2. As for masking material,
you can use either silicon oxide or photoresist and
due to the nature of the etching, the sticking problem
is completely eliminated. In case you are interested
to try out, you can just send me a wafer (or a few) to
Singapore and after etching I will ship it back to you
to Korea. We offer this service for a few samples free
of charge and the delivery time in this case should be
about a week or so. You can find more details at:
http://www.pentavacuum.com/mems.htm
The XeF2 etching can be also done at end (if
compatible with your process) of your fabrication
after the dicing and wirebonding so you do not have to
handle fragile structures after they are released.
Best regards
Pavel Neuzil
SiMEMS Pte Ltd
Singapore


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