In the fields of micro- and nanolithography, major
advances in resolution have been achieved through
the use of shorter wavelengths of light. Using phase-
shift mask technology, it has been demonstrated that
193 nm photolithography can produce sub-100 nm
features. Such improvements come with an ever-
increasing cost for photolithographic tools. As
conventional projection lithography reaches its limits,
NGL tools using shorter wavelengths and higher
numerical apertures (NA) may provide a means to
further pattern reduction, but are expected to have a
price tag that will be prohibitive for many companies.
The development of light sources and optics are primarily
responsible for the rise in the cost of an NGL tool. 157 nm
lithography, for example, requires the use of CaF
2
as a lens
material. In the case of extreme-UV lithography, no source
has yet been identified with sufficient output that will meet
the industry’s throughput requirements. Clearly, a technology
that can reduce tool cost by an order of magnitude will have
a significant effect on the economics of the fabrication
process
1
.
Imprint lithography is essentially a nanomolding process in
which the topography of a template defines the patterns
created on a substrate. Investigations by several researchers
in the sub-50 nm regime indicate that imprint lithography
resolution is only limited by the resolution of the template
fabrication process
2-4
. This approach possesses important
advantages over photolithography and other NGL techniques
since it does not require expensive projection optics or
advanced illumination sources.
by Douglas J. Resnick
a
*, S. V. Sreenivasan
b
, and C. Grant Willson
c
Step & flash
imprint lithography
a
Motorola Labs, 2100 East Elliot Road, Tempe,
AZ 85284, USA
*E-mail: doug.resnick@motorola.com
b
Molecular Imprints, Inc., 1807-C West Braker Ln.,
Austin, TX 78758, USA
c
Department of Chemical Engineering, The University
of Texas at Austin, Austin, TX 78712, USA
February 2005 34
ISSN:1369 7021 © Elsevier Ltd 2005
The escalating cost of next generation lithography
(NGL) is driven in part by the need for complex
sources and optics. The cost for a single NGL tool
could soon exceed $50 million, a prohibitive amount
for many companies. As a result, several research
groups are looking at alternative, low-cost methods
for printing sub-100 nm features. Many of these
methods are limited in their ability to do precise
overlay. In 1999, Willson and Sreenivasan developed
step and flash imprint lithography (S-FIL™). The use
of a quartz template opens up the potential for
optical alignment of the wafer and template. This
paper reviews several key aspects of the S-FIL
process, including template, tool, ultraviolet (UV)-
curable monomer, and pattern transfer. Two
applications are also presented: contact holes and
surface acoustic wave (SAW) filters.