Hi Peng,

Yes, ramped heating will help you avoid wrinkling and cracking of the
SU8 surface.  I usually have two hotplates set to 65C and 95C -- I
first place my wafers on the 65C plate, then to 95C and finally back to
65C.

Another thing I do to avoid wrinkled surface is to let the SU8 just sit
at room temperature for 10 minutes right after I spin it on.  I found
that the SU8 will "smooth out" quite a bit during these 10 minutes.

Good luck,

Mike

Mike Pinelis
Ph.D. Candidate
University of Michigan
http://www.wimserc.org
http://www.eecs.umich.edu/maharbiz
http://www.memsinvestorjournal.com



Quoting "Peng Li (Paul)" :

> Hey everybody,
>
> I am making mold on silicon wafer by SU-8 photoresist, however, sometimes
> I get "wrinkled surface". I heared that hotplate is better than convection
> oven, ramped heating is also helpful, but I am not sure.
>
> Could you please recommend an inexpensive equipment for ramped heating of
> SU-8 mold? Is there any other better ways to avoid wrinkled surface?