Michael:

Even though, Su-8 is a negative resist, conc.KOH at 75 C would cause most of the
commonly used resists to peel off. My suggestion would be to RIE SiO2 using Su-8
mask and then use SiO2 mask to wet etch Si. However, if you are having problems
with your Su-8 processing. I would be able to help you out if you send me the
process details.

hope that answers your question,
-Mahavir