At what point do the wrinkles occur? Possible causes are uneven hotplate
temperature or too rapid ramping / cooling.
Pitting can be due to insufficient dehydration of the wafer prior to
spinning, contaminants (either on the wafer surface or within the SU-8)
or bubbles during dispensing onto the wafer.
As for the cracks, often these are too shallow to be a problem but are
usually caused during the post exposure bake. Use a lower temperature
bake and/or ensure rapid heating and cooling is avoided. Alternatively,
I have also heard that a hard bake step sometimes closes these cracks.


li chunyu wrote:
> Recently I fabicated su8 mold and encountered some problem.
> First,after soft bake,there are some  wrinkles on the rim of dish and
> some
> pit on the surface,especially when using su8 75.
> Second,after development, there are some crackles on the surface of su8
> molding
>