I had a similar experience trying to do liftoff with AZ5214; vertical
sidewalls.  Sometimes the pattern wouldn't even develop.  I seem to
recall later reading that profile control with image reversal is
achieved by varying the image exposure dose.  I resorted to using the
LOR material from MichroChem with an over layer of S1813 resist.  The
LOR technique seems to be much simpler than image reversal and one can
achieve unlimited undercut if the geometry allows.  This makes liftoff
very easy, even with relatively thick metals.

Roger Shile

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
[email protected]
Sent: Wednesday, February 18, 2004 6:01 PM
To: [email protected]
Subject: [mems-talk] help request for image reversal and lift off with
AZ5214

Hello, everyone

I am working on AZ 5214 and trying to get reversed image with nice
undercut
profile. So for, I can only get vertical profile, which caused a big
problem
for lift-off process.

The substrate I am using is highly doped silicon deposited with SiO2
(200nm).
The recipe I tried is as follows:
prebake 90-100 degree 45-60 sec
image exposure   2-5 sec at 10mW/cm^2 (Karl suss MJB3)
PEB   115 degree   20-60 sec
Flood exposure  15-40 sec at 10mW/cm^2
Develpment   20-30 sec in AZ 400K (1:4)


When I tried to increase exposure dose and PEB time, some inversed
patterns(<10um) were gone and develpment became very diffult.The profile
is
overcut.  When the exposure dose is low and PEB time short, I can get
small
features in the inversed patterns, but the small gaps (the parts with
photoresist)between the inversed patterns are develped away easily . At
this
time, the profile is vertical because of overdevelpment.


Does anyone has experience with AZ 5214?  Please give me some suggestion
about
this problem.


Thanks,









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