Jianhua,

I found that cake icing works very well for filling trenches. You dilute it
with a little water and use a needle to inject it. Or pour it on and use a
squeegee to remove the excess. Bake at 325F for about 10-15 minutes and it's
solid (otherwise it will stay gel-like for a very long time - days). After
patterning your PDMS (haven't done that myself), you can either bake the
icing off at high temperature or soak the whole wafer in hot water for
several hours. Best part, you can eat the rest of the icing if you get
hungry.

Or you can use a negative photoresist with the mask you used to define the
trenches in the first place. Slow spin to reduce the effects of the trenches
on uniformity. Might need a little hard bake after exposure and developing
to prevent the solvents in the PDMS from messing up the photoresist. Acetone
or hot NMP to remove the photoresist after patterning PDMS.

Good luck.

Mike

Dr. Michael H. Beggans
Naval Surface Warfare Center, Indian Head
101 Strauss Ave. Bldg. 302            Phone: (301) 744-1927
Indian Head, MD 20640                  Fax:    (301) 744-6406

-----Original Message-----
From: Jianhua Tong [mailto:[email protected]]
Sent: Tuesday, July 25, 2006 11:34 PM
To: [email protected]
Cc: [email protected]
Subject: [mems-talk] Trench Filling and PDMS suspending

Hi, all,

I am designing a structure (a PDMS film bridge over a trench).  I need to
make a trench and fill it with some material(PSG,SOG,SU-8???...), and then
spin PDMS on it and pattern. the trench is 1000um*1000um and 30-40 microns
in depth.
Can anyone tell me which material is fine for filling a 40um-deep trench,
and what are the steps.

I also want to know whether there are some good ways to etch PDMS. does O2
plasma work? I found a paper that used scratching and lift-off, but i dont
think the surface will be very smooth after scratching.

I just searched on the internet/IEL, but failed to find good ways on it.

Thanks a lot,

Jianhua
----------------------------
[email protected]
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