I have seen a paper by Fred Williamson from the University of Minnesota
titled SU-8 as an E-beam resist.  I seem to recall that he successfully used
E-beam lithography to produce 3D structures in SU-8, mostly parabolic and
hemispherical lenses.  Also, you could use gray scale lithography to likely
achieve the same thing (we have made micro lenses out of UV curable
polyimide using gray scale lithography with some success).

Eric Miller
Laboratory Manager
Washington Technology Center
Ph:  206 616-3855
www.watechcenter.org


-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Kapi, Sameena
Sent: Monday, October 18, 2004 8:04 AM
To: [email protected]
Subject: [mems-talk] fabrication of cone structure with SU-8

Hello all,

I am trying to fabricate a cone structure using SU-8, with the base of
the cone (on the substrate surface) being approximately 50 microns, the
height of the cone approximately 100 microns, and the tip of the cone
approximately 20 microns across.  One method which was suggested was to
expose a 100 micron SU-8 layer thru a mask with 20 micron holes using a
DIVERGING light source - i.e. putting a concave lens in the path of a
collimated light source in order to produce a "cone" of light - with the
cone diverging to the desired width after the 100 micron thickness of
the SU-8, thereby exposing a cone of SU-8 to produce the desired
structure.  (The exposure time would have to be based on the required
flux at the base of the structure, which means that the surface (point
of cone) would be significantly overexposed.)  Does anyone have any
experience. or suggestions, regarding this process?



Thanks,

Ed

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