Steven,
       This is a classic problem with retained moisture at the edge of
the open areas.  Cure with normal resists was vacuum vapor prime. This
removed all moisture then sealed the surface against any return.  Result
no problems with future processing even at the edges.  The process is
very robust and can survive any sort of exposure after priming.  If you
want we can run free samples.

Bill Moffat, CEO
Yield Engineering Systems, Inc.
203-A Lawrence Drive, Livermore, CA  94551-5152
(925) 373-8353

bmoffat@yieldengineering.com

www.yieldengineering.com


-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Steven Yang
Sent: Monday, January 07, 2008 11:56 PM
To: mems-talk
Subject: [mems-talk] SU-8 2050 Cracking and Peeling off

Hi, all

These days got a lot of problem in SU-8 microchannel fabrication. I
tried to fabricate microchannel using SU-8 2050, after settle down some
alignment problem, I still cannot got the good sample while with the
SU-8 layer kept cracking or peeling off from substrate.

Here I gave the entire process I went through, could anyone give your
suggestion for my case.

Sub: square Si, with 2um PECVD SiO2 layer, and patterned EB evaporated
Cr/Au 150nm on it.

1) Hotplate: 150C to dehydrate 15mins
2) Spin coat SU-8 2050: 500/100/5s, and then 4000/1000/45s, suppose to
be 40um thick.
3) Softbake: 65C for 3mins, and cool down to room temperature, then 95C
for 30mins.
4) Exposure: MA8 CI1 7mw/cm2 35s
5) PEB: 65C for 3mins then raise the temperature up to 95C and stay for
10mins.
6) Develope: SU-8 developer for 4mins.

Results: part of SU-8 pattern starts to peel off from sub after 1-2 mins
rinse in developer, especially at the regions near microchannel open or
the edge of the Sub.

I am not doubting about the Exposure and PEB steps causing such result.
Could anyone advise me what dose and PEB process you adopted for a
sucessful SU-8 pattern.