Qing:

I don't think you will ever get the results you are looking to make with the
process you described. Contact the photoresist manufacturer first for
suggestions on how to do multiple coats of resist. You might need to bake for a
longer time at a lower temperature to begin with. Your exposure method is also
suspect. I am sure someone within the MEMS community has the proper equipment
for exposure you might be able to borrow or even do a joint development project
with to help you along. Bob Henderson