Hello, the residue has always been a problem with TiW etching in H2O2.
It is very hard to see under normal circumstances, but is decorated
quite "nicely" after passivation deposition.  I guess it also shows up
on white ceramic substrates.  Anyway, we modified the etch by adding a
little EDTA (and this removed the residue, I don't remember the
concentration, but it was a small amount of EDTA). Also, etching in a
stainless-steel container seems to work (without EDTA - don't know why).
I hope this old info helps. We developed this back in 1980 when we used
to etch Pt/TiW/Al stacks.

Charles Ellis....
Auburn University....


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Stella Chang
Sent: Monday, October 25, 2004 6:08 PM
To: [email protected]
Subject: [mems-talk] pink residue film after TiW etching on alumina

Hi all,

We are trying to etch a TiW adhesion layer on an Alumni substrate using
Clariant's TiW etchant.  We're observing a residue film (pinkish on the
white Alumina) that can be rubbed off using a Q-tip.  However, we don't
know how to remove this film from our patterned substrates.  We've tried
acetone, stripper, and RIE in an oxygen plasma, but the film remains.
It seems manually wiping off the film has the best results, but this
ruins the structures (1.5um of Au with TiW adhesion layer).

Has anyone observed this in the past?  Btw, we believe this film may
have something to do with having left the light-sensitive TiW etchant in
the light for too long.  The residue also remains after being dipped in
fresh TiW etchant at 37C.

Thank you for your time!

Stella Chang
University of Waterloo
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