Dear all,
I am trying to use a sputtered aluminum layer as a mask to etching an
undelying layer of Nb.
The process is as follow:
1) Deposit Nb
2) deposit Al
3) etch Al using transene type A etchant (49 C)
4) Dry etch Nb in IPE-RIE with a SF6 gas

Unfortunately if looks like the Al etchant "passivate" the underlying
Nb so that after the dry etch, it is very hard to get rid of it. I can
always see some remnants of Nb (either with optical or electron
microscope). I would really need to have a clean etch and I was
wondering if anybody had encountered a similar problem. I have also
tried to use CF4 to ecth Nb but I have the same problem
Thanks a lot
Fabio