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The nanoscope

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.

Dr. Johannes Ehrlenspiel
Hansastraße 27 c
80686 München








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