You might try a number of things.  Foremost, I would try something called a
neutral density filter, which when placed in the light path of your exposure
tool will reduce the joules/cm2 hitting the resist.  In other words, reduce
the intensity of your exposure, not only the exposure time of each dose.  If
you have a Karl Suss MA150, the system allows you to do this by computerized
adjustment to the lamp output.

The only other immediate idea I have would be to increase the soft bake
temperature and time of bake up to try to retard the photo-active nature of
the resist film, to slow the evolution of the nitrogen bubbles.  If you try
this, you will need to increase your develop times substantially.

- Justin

Justin C. Borski
MEMS Program Manager
Advanced MicroSensors Inc.
[email protected]
www.advancedmicrosensors.com



-----Original Message-----
From: Luigi Corti [mailto:[email protected]]
Sent: Monday, August 11, 2003 11:16 AM
To: General MEMS discussion
Subject: [mems-talk] AZ4620 bubbles in the process


Hi everybody,
I have been working with the photoresist AZ4620. I do want to get 8um thick
and my unexpose area 10um-wide lines, which give a large exposed area.
My problem is that I always have bubbles after the exposure. I did split my
exposure time in several small periods with delays of 30sec in between. Even
though I still get those bubbles. I addition, I checked after the first
second of exposure and most of the bubbles are there by this time.  I start
to thinking about the baking time, and reduce it without success.
If anyone of you had work successfully with AZ4620, please can help with
ideas to solve this problems or with a working recipe. I really appreciate
any input. thanks

Giancarlo Corti,
Graduate Student,  Mechanical Engineering
University of Idaho, POBox: 0902
Moscow, ID  83844-0902
Phone: (208) 885-4996
email:  [email protected]
        [email protected]
http://www.uidaho.edu/~cort4258




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