Steve,
      Let me do a free test for you.  This is possibly a similar
situation to aluminum etching on Silicon wafers.  What we discovered was
the aluminum layer needed 20 minutes of HMDS vacuum prime instead of 5
minutes.  This is due to the lower level of Hydroxyl ions on aluminum.
It is highly probable that Titanium needs longer and better adhesion
promotion than Aluminum.

Bill Moffat, CEO
Yield Engineering Systems, Inc.
203-A Lawrence Drive, Livermore, CA  94551-5152
(925) 373-8353

www.yieldengineering.com


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Stoffels Steve
Sent: Wednesday, February 06, 2008 4:56 AM
To: [email protected]
Subject: [mems-talk] Ti-etching with SPR-220/7 resist

Hey everybody.

Does anyone have experience etching titanium with SPR-220/7 resist as a
mask for patterning?  I am using a H20:BHF (9:1) solution to etch
titanium, however etching a 100nm thick titanium layer gives a undercut
of 1.3 micron under the resist.  Did anyone else experience this problem
or have a solution for this?  I tried a postbake in a oven of the resist
on three different samples 80C 15mins / 80C 25mins / 90C 15mins, this
did however not change the outcome.
I also tried to etch in a H2O2 solution, this however takes 2.5 hours to
etch and after this time the resist started to delaminate.

Any help would be greatly appreciated.
Greetings,
Steve Stoffels.