Hi Kris,
   We use a powdered silicic acid (anhydrous). I assume that mesh size
means particle size. If you use a very small particle size it will
dissolve quickly in the TMAH however it is tricky to handle in a fume
hood as it tends to blow around very easily. I would therefore recommend
using a relatively large particle size just to keep your clean room
manager happy.
: )

-Mike


>>> crikxo@yahoo.com 08/03/03 01:24AM >>>
Dear All,

I am trying to purchase silicic acid for TMAH
anisotropic etching of silicon(without atttacking Al).

I was going through the catalog of sigma-aldrich
chemicals and could find silicic acids with various
mesh sizes(from 35 microns-200 micros).The formula for
above Silicic acid is H2Sio3

URL:

http://www.sigmaaldrich.com/cgi-
bin/hsrun/Distributed/HahtShop/HAHTShop.htx;start=HS_CatalogSearch


I have also find silicic acid hydrate Sio2.

Can somebody suggest me which is the best silicic acid
to be purchased for TMAH etching of Anisotropic
etching of silicon.

Thanks
Kris

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