Creatv developed a unique method that allows
production of high-aspect-ratio microstructures
with a high degree of precision. This method
allows fabrication of septa as thin as 25 μm, a
thickness that cannot be achieved by
conventional casting, foil folding, or chemical
etching.
Creatv applies either deep x-ray or ultra-violet
(UV) lithography techniques to fabricate
microstructures. Both positive and negative tone
resists can be used in the process. Exposed
regions of the positive PMMA resist, or
unexposed regions of the negative SU-8 resist
are developed in the organic solvents, and the
cavities are then electroformed with metal.
Copper, lead and gold
electroforming were
successfully developed to obtain the final
structures. The resulting structures can be used
as an end product or may serve as a mold to
fabricate other articles by
replication.
Deep x-ray lithography using PMMA was applied to
fabricate collimators and anti-scatter grids up
to three mm tall with continuous, smooth,
parallel or focused septa. Hard x-rays are
available from synchrotrons such as Advanced
Photon Source at Argonne National Laboratory and
Center for Advanced Microstructures and Devices
at Louisiana State University.
In recent years, SU-8, a negative-tone
photoresist, has become attractive for many
applications in high-aspect-ratio
microfabrication, because of its high
sensitivity, excellent resolution, and low cost.
The use of SU-8 photoresist instead of PMMA
allows significant reduction in fabrication cost
because of the short exposure time (minutes
instead of hours). The thickness of the resist
layer is limited to about 1 mm. The difficulties
of SU-8 removal from the electroplated structure
previously have limited the utility of this
resist by others. Creatv developed techniques to
remove SU-8 from metal parts, enabling
successful use of SU-8.
Creatv has also developed proprietary technology
to use SU-8 in UV lithography. However, the
thickness of the SU-8 mold is limited to about
600-700 µm for narrow trenches and the finished
product is about 500 µm tall.
