Meifang,

Try to solve this problem with softbake.  A series of soft bakes from 65 to 95
to 105 °C should allow for the material to reflow to a more uniform condition
before it is set in place.


Best Regards,
Garrett Oakes

-----Original Message-----
From: Meifang Lai [mailto:meifang@mech.uwa.edu.au]
Sent: Wednesday, June 11, 2008 8:55 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] thickness variation of SU-8 layer

Hi all,

I am just starting to pattern a 50-µm-thick SU-8 layer on Si wafer by
photolithography. However, I found the SU-8 layer is not uniform. The center
of the SU-8 layer is about 8 µm higher than the part near the edge (except
the edge beads). My spin speed is: 500 rpm for 5 s with acceleration of 100
rpm/second, then spin at 3000 rpm for 40 s with acceleration of 1000
rpm/second. If any one has any solution for this problem, please tell me.

Thank you!

Cheers,

Meifang