Carson,
SU-8 is negative tone and so exposed regions should remain after development.
For SU-8 2035 with a 50um thickness I'm currently using an exposure dose of
around 270mj/cm^2 which in your case gives a time of 13.5 seconds.
Are you using an optical filter to attenuate components below ~350nm? In the
early stages of my SU-8 work I was using a broadband exposure source i.e. with
power below 350nm, which lead to very poor results. If this is the case for you
I would recommend obtaining a Hoya UV-34 filter to remove these components.
Hope this helps,
Novak
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of laetitia philippe
Sent: Wednesday, December 08, 2004 9:02 AM
To: [email protected]
Subject: [mems-talk] SU8 exposure time
Hello All,
I am trying to find the best exposure time for a SU8-2035 with a
thickness of around 50 um
This is not looking to be very easy. I am working with a UV i-line 365
nm, with 20 mW/cm2
For high exposure time (up to 100s ), I see that my structure does not
developp at all, i.e. the exposed polymer is not removed in the
developper although the sutructre is clearly visible with a color difference
between the exposed and non exposed part
For reasonnable exposure time (20 s), I have a good developpment but I
have always a resulting mould that is small as my mask. i.e some
feature of my pattern of 200 um would lead to only 100 um cavity in my
developped polymer and so one.
Finally, when I go down to 7 seconds, I have a good resulting mould,
with much better dimensions, but I have enormous stress on my polymer and
sometimes delamination which makes me thing I am under exposing of
course
Could someone share his own experience about that? especially about the
over-exposure'?
Many thanks
Carson
_____________________________________
Novak Farrington
Institute of Microwaves and Photonics
School of Electronic and Electrical Engineering
University of Leeds
Leeds LS2 9JT
UK
Mob. 0790 9948673
Fax. +44 (0)113 343 7265
email: [email protected]
