Kevin,
      I suspect your resist side walls do not have a reverse camber or slope.
With reverse slope no metal is deposited on the side walls and lift off is
ensured.  We have no problems with up to 40 micron thick resist.  The smallest
dimensions we have done in a production atmosphere is 0.1 micron metal gate.
Contact me directly and I will do free tests and send ample technical papers
[email protected].  Bill Moffat

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of [email protected]
Sent: Tuesday, December 01, 2009 7:19 AM
To: [email protected]
Subject: [mems-talk] Problems with EOT Liftoff of 1.5 um diameter holes (Auon
GaAs)

Hi Kevin,

it should be no problem. We use this recipe every day. What happens sometimes is
that you burn the resist (you see the non-developed regions
opaque) if you are too close to the evaporation source.
Of course you should use the AZ as reversal litho to obtain undercut. If you do
sputtering, lift-off is much more difficult.
Try also hot NMP (80°). I can lift more the 300nm of metal without
ultrasonication.

Good luck.
Daniel