Stephan,

How long did you leave the sample in acetone?  In my experience, acetone
works quite well to remove PMMA if you give it enough time (a couple of
hours if doing liftoff on 2" wafer).  However I haven't used that
combination of SF6 and Ar so perhaps, as you mentioned, a different
chemistry is required.

-Mike

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Stephan
Sent: Friday, July 28, 2006 10:30 AM
To: [email protected]
Subject: [mems-talk] To get rid of PMMA that was in a RIE


Hi!

After several ebeam lithogarphy steps, where I have patterned
freestanding structures out of SOI, I want to remove
selectively some
parts of the upper Silicon layer. So I spin on resist (PMMA
500000, 7%),
bake it at 170°C for 2 minutes. After ebeam exposure, I
develop and use
a RIE ICP with SF6 and Ar (5:10) to etch away the unprotected
areas on
the Chip.
All this works fine, the only problem is, to remove the resist
afterwards. Aceton does not work properly, some parts of the
resist
remain. I can't apply an O2 Plasma, because there are magnetic
structures on the Chip. This is probably dur to the fact, that
etching
does harm to the PMMA layer.

Do you have an idea, how to get rid of the resist?