Sample analysis with a GIXUVR
The group ‘Technology of extreme ultraviolet radiation’ at Chair Technology of Optical
Systems (TOS), the RWTH Aachen, Germany, investigates applications for laboratory-based XUV gas-discharge
sources . Extreme ultraviolet radiation (XUV, 1-50 nm, or EUV at 13.5 nm) enables new optical,
analytical and manufacturing technologies because of its characteristic interaction with matter, its short
wavelength, and recent progress on light sources and optical components. XUV tools are already deployed by
the semiconductor industry in the next generation lithography, which significantly accelerates a further
development of XUV technology. Future applications that will support the scientific progress in a
variety of fields, such as nanoelectronics or bio-technology, are the scope of their research. Activities
include structuring on a nanometer scale using interference lithography, XUV microscopy for imaging of
dynamic processes or at-wavelength inspection of multilayer mask-blanks for hidden defects, and
characterization of thin film coated surfaces using grazing-incidence reflectometry [2-6].
For the detection of the XUV radiation charge coupled devices (CCDs) with sufficient quantum efficiency
at the XUV wavelengths and with low level of noise are needed. Therefore several Andor CCD cameras are used
in the group’s laboratories.
The reflectometry set into the Andor DX440-BN CCD is successfully integrated. The developed XUV
reflectometer, shown in Fig. 1 and Fig. 2, consists of two spectrometers.
The first spectrometer utilizes a compact backthinned line sensor with the purpose of determining the
source emission spectrum.After interaction of the zeroth order of the emission with the sample, the
spectrum is analyzed again with the Andor CCD at the end of the beamline. A typical measured line spectrum
is shown in the Fig. 3. The DX440-BN also offers the possibility of in-vacuum operation that allow the
researchers to perform additional measurements of the scattered radiation.
The pixel size of 13.5 x 13.5 μm² provides a state-of-the- art resolution at this wavelength
range. With a sensor size of 2048 x 512 pixels the CCD allows for excellent spectral resolution, as well as
a capability to average the signal over 512 lines, thus improving the accuracy of measurements. In
comparison to line sensors, which were also investigated, the CCD offers the possibility of a vertical
XUV Quantum Efficiency
Series of experiments were performed with the Physikalisch Technische Bundesanstalt (PTB) at the
synchrotron BESSY in Berlin, Germany, to determine the quantum efficiency at the XUV wavelengths. The
quantum efficiency of the Andor DX440-BN CCD in the range from 1 nm to 34 nm is shown in Fig. 4.
The maximum of the QE is at 27 nm wavelength with the value of 64.6%. Due to strong absorption of XUV
radiation at the L-absorption edge of silicon a local minimum of 26.8% is situated next to 12.4 nm .
In summary, the research group found the Andor DX440-BN detector offers good quantum efficiency in the
XUV regime and
With thanks to:
Dipl.-Ing. (FH) Sascha Brose
Chair for the Technology of Optical Systems
RWTH Aachen University, Germany
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Wambach and D. Grützmacher, ‘XUV interference lithography for sub-10 nm patterning’,
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microscope’, in ‘26th European Mask and Lithography Conference’ edited by U. F. W.
Behringer and W. Maurer, Proc. SPIE 7545, 75450O–75450O-9 (2010)
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analysis’, Applied Physics Letters 94 (6), id. 063507 (2009)
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extreme ultraviolet’, Applied Spectroscopy 64 (4), 401–408 (2010)
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extreme ultraviolet’, Meas. Sci.Technol. 20, 105201–105201-5 (2009)
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extreme ultravioletter Strahlung’, diploma thesis, FH Aachen, Jülich (2008)