With he resists you list, lift-off would be difficult, since all of them
will exhibit a positive slope profile.  Also, all of those materials are
of the same, or similar, resin chemistry, so performing a two-stage
develop to create an undercut profile is not an option either.

Some suggestions for processing (which would require additional
materials, of course):

1) Use a lift off resist (negative tone) such as AZ nLOF 2000 series
(uses similar chemistry to AZP4620, and so can be processed in the same
spin bowl).

2) Use an image reversal resist (such as AZ 5214) - this can also give a
good negative profile for lift-off. Also, YES (Yield Engineering
Systems) has a solution for lift-off processes with other resists
(search the mems-talk archives for more info).

3) As I mention above, try to use a binary system, such as a PMGI
underlayer (from MicroChem), with resist over the top.  This way, the
top layer of resist will not directly interact with the bottom layer,
and the bottom layer will be undercut during the develop process.

Best Regards,
Chad Brubaker

-----Original Message-----
From:  Richard Chang
Subject: [mems-talk] Photoresist for Lift-off process

Hi, All,

  Does anybody know what the photoresist are for lift-off process other
than Futurrex NR7-1500PY?
  I need to use lift-off process to pattern the sputtering silicon
dioixde layer. But I don't have NR7-1500 PY.
  Could I use two different photoresists, just normal positive
photoresists, to do the lift-off? I have S1813, AZP 4620, and AZP 4210.
  Is there guidance I should follow?
  Thanks.