Sounds like a refraction issue.  Saw this with 12um BCB on round structures
about 60um wide (was using EV aligner).  Can be solved by either going to
thinner resist or using a stepper where we could control the plane of focus.
Was going to try some contrast enhancement material from Shin Etsu but never
really had the time to explore that.

-David Marx


-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Michael Juhl
Sent: Friday, June 25, 2004 7:39 AM
To: [email protected]
Subject: [mems-talk] UV-lithography


Hello

I have a problem with defining towers of diameters less that 10 µm in
AZ4511 resist. A small hole with a diameter of about 1µm appears in the
middle of the tower. I am using a standard i-line Karl-Süss
mask-aligner. How can I get rid of these small holes?

Best regards
Michael Juhl