Hello,

I have found a difficulty in exposure dosage for SU-8 PR. My fabrication include
2 times of exposure in 2 lithography processes.

The first exposure is alright with 250 mJ/cm2 for 10 um thickness! Following by
a deep Si etching, its depth is about 15um. After taking the second PR coating,
now, the total thickness is about 25 um (for the etched areas) and 10 um (for
other areas). My question is how to choose an optimize exposure dose to get a
high exposure resolution due to non-uniform thickness of SU-8 layer.

PS: for large features (~ 100 um-width), it's alright, but for a small feature
as below 8um-width, it seemed the PR cannot be removed out of that area!

Please give me some suggestions.

Thanks!