Hi Peter,

  Confused if you trying to etch the ITO or the metal layer....

  For ITO: You should be able to etch ITO in HF or HCl, though you need to
dilute in water (by about 10-25%) to obtain controllable, reproducible etches,
as etch rate in very high otherwise. The other problem, whichever metal you use,
you will obtain a strong undercut, obviously dependent upon etch time/film
thickness.   .

  For metal, I would actually suggest you best chance for patterning any metal
onto ITO is to use lift-off.  Al films (approx. 50nm) can be selectively removed
from ITO by placing in heated KOH for circa 1 minute. Overetching can result in
ITO etching though.

  I'm haven't seen any dry etch chemistries that you can etch metals and not
ITO. Argon plasmas are good at etching ITO, but leaving the Al  film.

  Cheers, jeff kettle

From: "P.E.M. Kuijpers" 
To: mems-talk@memsnet.org
Date: Wed, 6 Aug 2008 08:06:36 +0200
Subject: [mems-talk] Metal etching

Dear all,

Can one of these metals Cr, Ti, Cu or Mo selectively be etched compared to
ITO and what kind of etchant can be used for this

Thanks
Peter