JIAN WANG AND HUBERT KOSTAL
Repeat Test and dice
Mold preparation
Imprint Repeat for multilayer
Wafer Deposition Nanoimprint Etching Deposition preparation lithography
NANOOPTO
FIGURE 1. In nanoimprint lithography, a mold is used repeatedly to pattern prepared wafers in volume. After the final deposition step, wafers can either be diced to size or run through the process again for additional functional layers.
With their unique properties, diffrac- designed using a broad material range that includes dielec-
tive optics can improve optical sys- trics, metals, polymers, and plastics, and many types of reg-
tems by increasing their reliability, ular structures, including linear, grid, and circular, which
robustness, and functional integra- allows them to be fabricated by extending semiconductor-
tion, while reduc- production techniques that
ing their effective size. One interesting class With its precision, simplify and reduce the cost
of diffractive optics has critical dimensions of optical-component fabrica-
smaller than the wavelength of the light with versatility, and 3-D tion. Specifically, nanoimprint
which they are designed to interact. These lithography is an emerging
nano-optic diffractive structures typically capabilities, nanoimprint manufacturing methodology
have grating periods ranging from
50 to lithography is well suited that simultaneously enables 200 nm. They exhibit only zero-order dif- high-throughput wafer-scale
fraction, allowing for precise control of light for the manufacture of production and the nanoscale
without loss into undesired orders; with ap- lithographic resolution need-
propriate selection of materials they can ex- subwavelength ed to produce multifunction
hibit, among other optical properties, form integrated subwavelength op-
birefringence or polarizing behavior, or both diffractive optics. tical components.
simultaneously; and their optical function
is realized in less than a micron of thickness. Polarization Nanoimprint lithography
filters, polarizing beamsplitters, spectral filters, retardation Standard photolithography is now capable of creating sub-
plates, and lenses are among the functions that have been 100-nm linewidths, but even this is not yet sufficiently high
demonstrated using subwavelength-grating structures. resolution to be generally usable for the creation of practical
Breakthrough efficiencies in the manufacturing of these subwavelength diffraction gratings. Other lithographic ap-
optical components must be achieved to drive down the proaches have been developed specifically to address these
cost of subwavelength diffractive optics. Such optics can be challenges, including “soft lithography” (or microcontact
printing), atomic-force-microscope/dip-pen lithography,
and nanoimprint lithography. Of these, nanoimprint
JIAN WANG is chief technical officer and HUBER T KOSTAL is vice president of marketing and sales at NanoOpto, 1600 Cottontail Lane, lithography has so far demonstrated the most commercial Somerset, NJ 08873; e-mail: HKostal@nanoopto.com. success, both in the availability of commercial manufac-
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