Hi,

I'm working with SU-8 2010, with thickness of 7 and 20um. I observed the

same problems.
But to me it looked like a over-exposure. The give times from MicroChem
may be for a pure silicon wafer. I use SU-8 on aluminium and have to
reduce the time dramatically, because of the high reflectivity of the
aluminium layer.
Multi-exposure, idle periods between process steps and ramped heating
is also a great improvement.
        Christoph

-----Ursprüngliche Nachricht-----
Von: Alik Widge [mailto:alik@cs.cmu.edu]
Gesendet: Donnerstag, 7. August 2003 23:13
An: mems-talk@memsnet.org
Betreff: [mems-talk] Another SU-8 question


Folks,

Yes, I'm still working on the SU-8 problem (and thanks to the folks from

MicroChem and EV Group who sent me some process sheets). At this point,
I've got it down such that I can spin the layer to the thickness I want
and
expose it such that it doesn't fall off the wafer, but I'm having a
problem
in the final development step. Here's my process (roughly):

- Spin on SU-8 2007 to 10 um thickness
- Prebake 1 min @ 65 degC, 2 min @ 95 degC
- Expose 32 seconds @ 3.3 mW/cm2
- Postbake 1 min @ 65 degC, 2 min @ 95 degC
- Develop by immersion with agitation, isopropanol rinse

My problem is that even after long developments with vigorous agitation,

the SU-8 is not gone from the trenches between my structures; there is
clearly a thin dark film of it left. I have tried reducing bake times,
reducing exposure times, and so on, and all these do is push my wafers
into
being undercrosslinked and cause the SU-8 to lift up off the surface or
dissolve during the development step.

Has anyone experienced this problem before, and if so, is there a known
solution?

Alik