Dear Chad,

I have experience working with trenches which are more then a 100 micron
thick. I tried spraying AZ-1518 PR on it but after softbaking the trences
could not be completely covered. An SEM would confirm the coverage. The only
solution I found was using a very thick PR, which is thicker then the
minumum depth of the trench. SU-8 50 or SU-8 2050 can form a 100 micron
thick layer which should be sufficient. However SU-8 does have release
issues so you would definitely need to use Omnicoat as the release layer.
Also you might try NR4-8000P which can form a 100 micron thickness as well
and is Acetone strippable. However the exposure time for that thick a layer
is approx. 6 min 30 sec for a 14 W/m2 light intensity source so depending
upon the capability of your mask aligner you might need to do multiple
exposures. Check your mask aligner capability before opting for this PR.

Thanks
Aeraj ul Haque