There exists a very good simulation toll for wet etching of silicon, called
SIMODE.
Address:
Dr. Dirk Zielke
GEMAC GmbH
Matthesstrasse 53
D-09113 Chemnitz
Germany
Phone: ++49-371-3377-221
Fax:      ++49-371-3377-272
E-mail: gemac.chemnitz@t-online.de
Web: http://www.gemac-chemnitz.de/

Much success!

U.Breng