Hi Dr. Rusanov,

Thanks for your suggestion. I tried 20 sccm CF4, 1sccm O2, 40 mtorr,
60W. I get visible narrowing of my etch mask (I switched from Al to
Cu). I did 1 etch for 40s and etched away possibly 15-20 nm of Nb
underneathe my Cu pattern.  After etching for another 40s, I have
evidence that my Nb is being completely undercut again.

Should I decrease the power further? Is there another chemistry that
might work better.

Thanks!
Serena

--
Graduate Student
3017 MRL
University of Illinois at Urbana-Champaign
Department of Physics
104 S. Goodwin Ave.
Urbana, IL 61801

www.alumni.caltech.edu/~seley

On 11/8/07, [email protected]  wrote:
> Hi Serena,
>
> I suggest to try CF4/O2 (about 5% of O2). Make sure your pressure is below 50
mtorr.
> This should work pretty well. And of course your RIE chamber should be well
descummed before the process of RIE etching.
>
> Regards,
>
> Dr. A.Yu. Rusanov