Hello everyone,
   I am new to both this mailing list and photolithography. Recently I
am having problem with SU8 2025 on 3-inch wafer. The basic procedure
is the following:
   Spin coating: 3000 rpm, giving a height of about 28 micron.
   Pre-bake: 65 degree C 1 min and 95 degree C 3 min
   Exposure: 1 min using transparency as mask
   Post-bake: same as prebake
   Develop: 1-2 minutes in SU8 developer from Microchem(no IPA rinsing)
   The pattern is composed of some 30 micron squares separated by
30-50 microns, so I should have "square" pillars after development.
This procedure worked well for a while, then we switched to a new
bottle of photoresist and a new company for printing transparency mask
with higher resolution. Then we had problem in producing clean
features. To be particular, we found 30 micron squares surronded by a
bigger, black square edge. The edge is tilted around 90 degree
relative to the 30 micro pattern. The dark edge cannot be removed by
prolonged development or IPA rinsing. Also the transparency looks ok
under microscope and we could produce 30 micron patterns weeks ago
when using a different transparency also by this company. As a
control, I switched back to the left-over old photoresist and old
transparency. Although dark edges are reduced, there are still black
remant around patterns. So I am confused ...
    Due to limited resources, I am looking for other's similar
experience before doing more trouble shooting. Any input is gratefully
appreciated. Thanks in advance.

Best,
LIU Yu