Hi all,
  I guess that Oygm observation is true in general, because if SU-8 is over-
exposed you get a more compact or more cross-linked and so less permeable
polymer, so it´s much more difficult that it get swollen due to developer,
and cross-linked is more uniform, there are less tensile stress. When there are
a under-exposure, the external su-8 layer is well cross-linked but not the
layers down, so these last can adsorb solvent and give craks...

  There are something that I don´t understand, you say that there are some
cracks but they disspear after hard-bake... sound strange, because the cross-
linking make Su-8 not softening or meltable by increasing the temperature... but
if it works... it works.
  Do you have some problem with bubbles?

  Eowin

oygm  skrev:

Today I tried exposure dose 400mJ/cm2. This time most of the cracks disappeared
with 120s developing. And the feature looks very nice. After 140c 60s hard bake,
all cracks disappeared. Hence I believe Kevin gets the point, under-exposure
leads to the cracks in my case!