Chris,

This is a very interesting question. Maybe you can provide the average shape
and dimension of your recessed structures to help people understand your
situation better.

I would try letting photoresist cover the wafer completely (instead of 1/3 or 1
/4 of the wafer surface) before spining, and perhaps spining at a slower rate
initially. I am curious about whether you have tried these.

Regards,

Chang Liu
MEMS Critical Research Initiative
University of Illinois, Urbana-Champaign
217-333-4051(o)
http://www.cco.caltech.edu/~changliu