At next
week's Conference on Lasers
and Electro-Optics/Quantum Electronics
and Laser Science Conference (CLEO/QELS)
in California, Courtney Brewer
of Colorado State University (brewerca@holly.colostate.edu) and her
colleagues will present a tabletop optical imaging system that can
reveal details smaller than 38 nanometers (billionths of a meter) in
size, a world record for a compact light-based optical microscope.
The microscope can keenly inspect nanometer-scale devices designed
for electronics and other applications. It will also be capable of
catching subtle manufacturing defects in today's ultra-miniaturized
computer circuits, where defects just 50 nm in size that were once
too small to cause trouble could wreak havoc in the nanometer scales
of today's computer chips.
Except for some high-tech details, the
microscope works very similarly to a conventional optical
microscope. Light shines through the sample of interest. The
transmitted light gets collected by an "objective zone plate," which
forms an image on a CCD detector, the same kind of device that
records images in a digital camera.
However, in the case of the sub-38-nanometer microscope, there are some
advanced technological twists. The microscope uses a laser that
produces light in the extreme-ultraviolet (EUV) spectrum, whose very
small wavelength makes it possible to see a sample's tiny details.
The EUV light is created by ablating (boiling away) the surface of a
silver or cadmium target material so that the vaporized material
forms a plasma (collection of charged particles) that radiates laser
light. To focus this light, the researchers avoid standard lenses
because they strongly absorb EUV radiation. Instead, the microscope
uses "diffractive zone plates," structures containing
nanometer-spaced concentric rings that focus the light in the
desired fashion.
Other state-of-the-art optical microscopes have achieved resolutions
as low as 15 nanometers, but they required the use of large synchrotrons.
This more compact and less expensive system has the potential to
become more widely available to researchers and industry. In
addition, since the extreme ultraviolet laser produces light pulses
with very short duration (4 picoseconds, or trillionths of a
second), the researchers believe it may be possible to create
picosecond-scale snapshots of important processes in other
applications.
Paper CME4 at the Conference on
Lasers and Electro-Optics/Quantum Electronics
and Laser Science Conference (CLEO/QELS)
Contact Courtney Brewer, Colorado State University, brewerca@holly.colostate.edu
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