Andreas, there is a poly-isoprene resist from Transene that is stable in KOH
solutions.  http://transene.com/pkp/

-----Original Message-----
From: Andreas K. Huettel [mailto:andreas.huettel@physik.uni-regensburg.de]
Sent: Saturday, May 6, 2017 7:42 PM
To: General MEMS discussion 
Cc: alexander.albang@physik.uni-regensburg.de
Subject: [mems-talk] Wet-etching Si, while a niobium film is protected

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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