Researchers
are discerning objects in ever-smaller dimensions through
advances in microscope technology. The big leap from
micro to nano is being made possible with extreme ultraviolet
(EUV) hence the worlds first nanoscope, compliments
of the scientists at Fraunhofer.
In the production of high-performance integrated circuits
with increasingly finer structures, the days of visible
light are gone. The semiconductor industry has meanwhile
moved on to processes that entail ultraviolet laser
with wavelengths of 193 and 248 nanometers. The candidate
with the brightest prospects for continuing the trend
of manufacturing even finer structures is extreme ultraviolet
or EUV. This lithography operates at wavelengths close
to x-ray, in the 11 to 14-nanometer range. However,
this poses various problems. To generate EUV beams,
synchrotron radiation facilities are required which
are big, costly and complex. And since EUV is absorbed
by the atmosphere, the entire exposure process must
take place in a vacuum. Finally, instead of conventional
transparent masks and lenses, EUV beams must be reflected
using special mirrors. Fraunhofer
researchers in Aachen recently introduced the worlds
first synchrotron-independent EUV microscope. We had
to solve several demanding technical challenges and
develop a totally new, high-performance, economical
EUV radiation system, recalls Willi Neff of the Fraunhofer
Institute for Laser Technology ILT. Clearly the scource
isnt as powerful as a synchrotron machine. This part
comes from AIXUV, a company that specializes in EUV
technology. The optical systems such as collectors,
multilayer mirrors and Schwarzschild optics were supplied
by the Fraunhofer Institutes for Material and Beam
Technology IWS and for Applied Optics and Precision
Engineering IOF. A CCD camera is used to capture the
image. The detector pixel size still limits the achievable
resolution, at present nevertheless well under one
micrometer.
The
objective of reaching a resolution of only 50 nanometers
is just
one aspect, emphasizes Neff. Different to other devices,
our nanoscope also supplies information about deeper
atom layers and their identities. An additional factor
is moving images. A single EUV pulse, typically lasting
a tenth of a second, is all thats required to capture
an image of the object to be examined. At a pulse
frequency of 50 hertz, its possible to create films.
Combining
spectroscopy with high-resolution imaging opens up
a wealth of new applications in the fields of materials
and life sciences. Besides biological structure research,
future areas of focus include examining thin films
and semiconductors. Through their advances in the
development of functional EUV devices, the Fraunhofer
researchers have laid the groundwork that will enable
scientific and industrial research laboratories to
implement and continue testing this technology.
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