I did a similar thing.  I assume that you are using a high power O2 plasma.
I think that the SU-8 doesn't etch, but sputters down until it just can't
any more.  You end up with a residue anywhere there was SU-8.  I got
beautiful SU-8 etching with 20% CF4 80% O2 at low power (30W) for a long
time.  No residue and relatively little etching of the Oxide substrate.  If
the rest of your device can handle the CF4, I think this is the way to go.

Good Luck
Greg Reimann



> Hi,
>
> May I add a question? I've tried to ash SU-8 with O2 plasma in
> ICP/RIE system. But there is a film of residue on wafer. Have you seen
> such problem?
>
> Isaac
>
>
> On Fri, 7 Mar 2003 [email protected] wrote:
>
> > What type of reactor do you have? Is it a barrel asher or a single wafer
system. OUr experience with oxygen and su8 shows it will ash but it is
better if you have not done the second bake. This has been done in an
icp/rie system and the etch rate is a little less than other negative
working photoresists. Bob Henderson
> >
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>
> Yours sincerely,
>
> Isaac Chan
>
> Ph.D. Candidate
> Dept. Electrical & Computer Engineering
> University of Waterloo
> 200 University Ave. W
> Waterloo, Ontario, Canada
> N2L 3V1
> Tel: (519) 729-6409, ext. 6014
> Fax: (519) 746-6321
> [email protected]
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>
>
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>