Jeffrey,
   Strong bases are frequently rough on any polymer. I would just use HF to etch
the Ti (though there are lots of ways to etch it), assuming your process will
take it.  Aqua Regia can be a little tricky as it is sometimes hard on resists
and "ages" rapidly.  We use 3:1 HCl:HNO3 at room temperature without the added
water but use it immediately after mixing.  After about 10min the solution
properties change and you should discard the solution.

Good luck,
   Mike Martin
   U. of Louisville

>>> "Yue Mun Pun, Jeffrey"  3/6/2007 1:33 AM >>>
Hi,
I have observed in my experiments that dilute aqua regia (3 parts HCl : 1 part
HNO3 : 2 parts H2O) dissolves evaporated Gold at a rate of ~3nm/s, but etches
Titanium very slowly or not at all.  Therefore Titanium can be used as an etch
mask when etching Gold with this chemistry.  Also, Titanium can be dissolved
with 1:2 or 1:3 NH4OH:H2O2 at a rate of 2.5nm/s, but does this chemistry does
not etch Gold.

So in my application, I am considering etching Titanium with the HN4OH:H2O2
chemistry while masking certain parts of the Titanium with AZ5214E resist.  Does
H2O2 attack AZ5214E resist?

Also, I intend to use Titanium as an etch mask when etching Gold with Dilute
Aqua Regia.  The Gold is evaporated on patterns of crosslinked and uncrosslinked
SU-8 2050.  Does the HCl and HNO3 chemicals in Aqua Regia attack uncrosslinked
SU-8?