Dear Mac,
  You can use KOH Etch for deep Si Etch.
  Etch rate of KOH varies with temperature and concentration.

                   KOH Soln %
            Etch rate (um/hr)
                  50
            26
                  45
            31

  I hope, this serves the purpose. Please feel free to contact me at
[email protected]  or at 3182354806.

  Sincerely,
  Aditya Bhandare


Mac McReynolds  wrote:Does  any one have a source
for deep silicon etching on 200mm wafers?? I'm  looking for depths in the range
of 100-200µ, large (50µ plus) features.