Andreas,

What is the diameter of the holes you are trying to make?
Are the holes on the same wafer side where the Nb film is located?
Are you trying to form a membrane?

I may have a solution to your problem but it depends on a bit more
knowledge
of your task.

H. Estrada

*             _______*

*Horacio V. Estrada, PhD*
Director
Laboratorio de Microsistemas
CIDESI
Queretaro, QRO
Phone: +52 (442) 211-9800 x1511
Cell MEX: +52 (442) 471-4179,
Cell USA: +1 (980) 254-6951
________________________

2017-05-07 8:28 GMT-05:00 Bill Moffat :

> You could try photosensitive Polyimide if the resolution is good enough.
> It is far more chemically resistive to attack. If you need help baking the
> Polyimide send it to us for free test. Bill Moffat
>
> Sent from my iPad
>
> > On May 6, 2017, at 5:58 PM, Andreas K. Huettel <
> andreas.huettel@physik.uni-regensburg.de> wrote:
> >
> > Dear all,
> >
> > we need to etch deep holes into a Si wafer (with a 500nm surface oxide)
> that
> > already has sensitive Nb structures on top.
> >
> > The etching alone works mostly fine with first RIE through the oxide and
> then
> > hot KOH. However, the KOH also dissolves our photoresist and then
> attacks the
> > niobium.
> >
> > We already tried placing a baked-out PMMA layer between niobium and
> > photoresist, but that didn't help too much.
> >
> > Do you have any advice for this?
> > Are there any photoresists around that are KOH-stable?
> > What other protective could be used that later are easily removed?
> >
> > Best,
> > Andreas
> >
> > --
> > PD Dr. Andreas K. Huettel
> > Institute for Experimental and Applied Physics
> > University of Regensburg
> > 93040 Regensburg
> > Germany
> >
> > tel. +49 151 241 67748 (mobile)
> > tel. +49 941 943 1618 (office)
> > fax +49 941 943 1670
> > e-mail andreas.huettel@ur.de
> > http://www.akhuettel.de/
> > http://www.physik.uni-r.de/forschung/huettel/
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