Frank Barkusky

Laser-Laboratorium Göttingen e.V., Göttingen, Lower Saxony, Germany

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Publications (37)20.82 Total impact

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    ABSTRACT: We studied 1-on-1 and 10-on-1 damage threshold investigations on Mo/Si multilayers with EUV radiation of 13.5 nm wavelength, using a table-top laser produced plasma source based on solid gold as target material. The experiments were performed on different types of Mo/Si mirrors, showing no significant difference in single pulse damage thresholds. However, the damage threshold for ten pulses is ≍ 60 % lower than the single pulse threshold, implying a defect dominated damage process. Using Nomarski (DIC) and atomic force microscopy (AFM) we analysed the damage morphologies, indicating a primarily thermally induced damage mechanism. Furthermore, we studied the radiationinduced change of reflectivity upon damage of a multilayer mirror. Additionally, we characterised transmission and reflection properties of novel Mo/Si multilayer beam splitters performing wavefront measurements with a Hartmann sensor at 13.5 nm wavelength. Such wavefront measurements allow also actinic investigations of thermal lens effects on EUV optics.
    Proc SPIE 05/2013;
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    ABSTRACT: Extreme ultraviolet Mo/Si multilayers protected by capping layers of different materials were exposed to 13.5 nm plasma source radiation generated with a table-top laser to study the irradiation damage mechanism. Morphology of single-shot damaged areas has been analyzed by means of atomic force microscopy. Threshold fluences were evaluated for each type of sample in order to determine the capability of the capping layer to protect the structure underneath.
    Journal of Applied Physics 01/2013; 113(20):203106. · 2.21 Impact Factor
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    Frank Barkusky, Armin Bayer, Klaus Mann
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    ABSTRACT: We have investigated ablation of polymers with radiation of 13.5nm wavelength, using a table-top laser produced plasma source based on solid gold as target material. ASchwarzschild objective with Mo/Si multilayer coatings was adapted to the source, generating an EUV spot of 5μm diameter with a maximum energy density of ∼1.3J/cm2. In combination with a Zirconium transmission filter, radiation of high spectral purity (2% bandwidth) can be provided on the irradiated spot. Ablation experiments were performed on PMMA, PTFE and PC. Ablation rates were determined for varying fluences using atomic force microscopy and white light interferometry. The slopes of these curves are discussed with respect to the chemical structure of the polymers. Additionally, the ablation behavior in terms of effective penetration depths, threshold fluences and incubation effects is compared to literature data for higher UV wavelength.
    Applied Physics A 10/2011; 105(1):17-23. · 1.69 Impact Factor
  • K. Mann, F. Barkusky, A. Bayer, S. Döring
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    ABSTRACT: As a consequence of the steadily increasing EUV powers and radiation doses, damage and degradation testing of EUV optical elements has become an important issue. In this contribution we report on first damage tests on optics and detectors for the wavelength of 13.5nm using a high fluence micro-focus from a laboratory-scale EUV source. The setup consists of a laser-generated plasma from a pulsed gaseous Xenon jet or a solid Au target, respectively. In order to obtain a small focal spot resulting in a high EUV fluence, a modified Schwarzschild objective consisting of two spherical mirrors with Mo/Si multilayer coatings is adapted to the source, simultaneously blocking unwanted out-of-band radiation. By demagnified (10x) imaging of the Au plasma an EUV spot of 5 μm diameter with a maximum energy density of ~1.3 J/cm2 is generated at a wavelength of 13.5 nm and a pulse width of 8.8 ns. We demonstrate the potential of this integrated source and optics system for damage testing on EUV optical elements and sensoric devices. As an example, single pulse ("1-on-1") and multiple pulse ("S-on-1") damage thresholds were determined for Mo/Si multilayer mirrors, using both on-line optical microscopy, interferometry and atomic force microscopy for damage detection. The data are compared with in-situ measurements of the reflectivity change at 13.5nm. Moreover, thin metal coatings (Gold) used as grazing incidence mirrors were irradiated. Threshold energy densities for damage and film removal were determined, showing a linear dependence on the film thickness. Furthermore, EUV-to-VIS quantum convertors (Ce:YAG crystals, phosphor coatings) employed for beam characterization were investigated in terms of linearity, saturation behavior and conversion efficiency.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
    03/2011;
  • K. Mann, F. Barkusky, A. Bayer, S. Döring
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    ABSTRACT: As a consequence of the steadily increasing EUV powers and radiation doses, damage and degradation testing of EUV optical elements has become an important issue. In this contribution we report on first damage tests on optics and detectors for the wavelength of 13.5nm using a high fluence micro-focus from a laboratory-scale EUV source. The setup consists of a laser-generated plasma from a pulsed gaseous Xenon jet or a solid Au target, respectively. In order to obtain a small focal spot resulting in a high EUV fluence, a modified Schwarzschild objective consisting of two spherical mirrors with Mo/Si multilayer coatings is adapted to the source, simultaneously blocking unwanted out-of-band radiation. By demagnified (10x) imaging of the Au plasma an EUV spot of 5 mum diameter with a maximum energy density of ~1.3 J/cm2 is generated at a wavelength of 13.5 nm and a pulse width of 8.8 ns. We demonstrate the potential of this integrated source and optics system for damage testing on EUV optical elements and sensoric devices. As an example, single pulse ("1-on-1") and multiple pulse ("S-on-1") damage thresholds were determined for Mo/Si multilayer mirrors, using both on-line optical microscopy, interferometry and atomic force microscopy for damage detection. The data are compared with in-situ measurements of the reflectivity change at 13.5nm. Moreover, thin metal coatings (Gold) used as grazing incidence mirrors were irradiated. Threshold energy densities for damage and film removal were determined, showing a linear dependence on the film thickness. Furthermore, EUV-to-VIS quantum convertors (Ce:YAG crystals, phosphor coatings) employed for beam characterization were investigated in terms of linearity, saturation behavior and conversion efficiency.
    Proc SPIE 03/2011;
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    ABSTRACT: We present first damage threshold investigations on EUV mirrors and substrate materials using a table-top laser produced plasma source. A Schwarzschild objective with Mo/Si multilayer coatings for the wavelength of 13.5 nm was adapted to the source, generating an EUV spot of 5 microm diameter with a maximum energy density of approximately 6.6 J/cm(2). Single-pulse damage tests were performed on grazing incidence gold mirrors, Mo/Si multilayer mirrors and mirror substrates, respectively. For gold mirrors, a film thickness dependent damage threshold is observed, which can be partially explained by a thermal interaction process. For Mo/Si multilayer mirrors two damage regimes (spot-like, crater) were identified. Fused silica exhibits very smooth ablation craters, indicating a direct photon-induced bond breaking process. Silicon shows the highest damage threshold of all investigated substrate and coating materials. The damage experiments on substrates (fused silica, silicon, CaF(2)) were compared to excimer laser ablation studies at 157 nm.
    Optics Express 03/2010; 18(5):4346-55. · 3.55 Impact Factor
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    ABSTRACT: We present first damage threshold investigations on EUV mirrors and substrate materials using a table-top laser produced plasma source. A Schwarzschild objective with Mo/Si multilayer coatings for the wavelength of 13.5 nm was adapted to the source, generating an EUV spot of 5 mum diameter with a maximum energy density of ~6.6 J/cm2. Singlepulse damage tests were performed on grazing incidence gold mirrors, Mo/Si multilayer mirrors and mirror substrates, respectively. For gold mirrors, a film thickness dependent damage threshold is observed, which can be partially explained by a thermal interaction process. For Mo/Si multilayer mirrors two damage regimes (spot-like, crater) were identified. Fused silica exhibits very smooth ablation craters, indicating a direct photon-induced bond breaking process. Silicon shows the highest damage threshold of all investigated substrate and coating materials. The damage experiments on substrates (fused silica, silicon, CaF2) were compared to excimer laser ablation studies at 157 nm.
    Proc SPIE 03/2010;
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    ABSTRACT: In recent years, technological developments in the area of extreme ultraviolet lithography (EUVL) have experienced great improvements. Currently, the application of EUV radiation apart from microlithography comes more and more into focus. Main goal of our research is to utilize the unique interaction between soft x-ray radiation and matter for probing, modifying, and structuring solid surfaces. In this contribution we present a setup capable of generating and focusing EUV radiation. It consists of a table-top laser-produced plasma source. In order to obtain a small focal spot resulting in high EUV fluence, a modified Schwarzschild objective consisting of two spherical mirrors with Mo/Si multilayer coatings is adapted to this source, simultaneously blocking unwanted out-of-band radiation. By demagnified (10x) imaging of the plasma an EUV spot of 5 mum diameter with a maximum energy density of ~7.4 J/cm² is generated (pulse length 8.8 ns). We present first applications of this integrated source and optics system, demonstrating its potential for high-resolution modification and structuring of solid surfaces. As an example, etch rates for PMMA, PC and PTFE depending on EUV fluences were determined, indicating a linear etch behavior for lower energy densities. In order to investigate damage tests on EUV sensors and optics, 1-on-1 damage tests were performed on grazing incidence gold mirrors, Mo/Si multilayer mirrors and mirror substrates. To our knowledge, this is the first time that such experiments using nanosecond EUV-pulses were carried out.
    Proc SPIE 10/2009;
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    ABSTRACT: We present a compact setup for near-edge x-ray absorption spectroscopy at the carbon K-edge based on a laser-driven plasma source. Thin polymer films were investigated, showing good agreement with corresponding synchrotron data. Furthermore we have examined the carbon near-edge structure of phospholipids and fulvic acids, providing detailed information on intermolecular binding states.
    Journal of Physics Conference Series 09/2009; 186(1):012032.
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    ABSTRACT: We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky-photodiode-based detectors. AlGaN layers were grown using metal-organic chemical vapor deposition (MOCVD) on Si(111) wafers. The diodes were characterized at a wavelength of 13.5 nm using a table-top extreme-ultraviolet (EUV) radiation source, consisting of a laser-produced xenon plasma and a Schwarzschild objective. The responsivity of the diodes was tested between EUV energies ranging from 320 nJ down to several picojoules. For low fluences, a linear responsivity of 7.14 mAs/J could be determined. Saturation starts at approximately 1 nJ, merging into a linear response of 0.113 mAs/J, which could be attributed to the photoeffect on the Au electrodes on top of the diode. Furthermore, degradation tests were performed up to an absolute dose of 3.3x10(19) photons/cm(2). AlGaN photodiodes were compared to commercially available silicon-based photodetectors. For AlGaN diodes, responsivity does not change even for the highest EUV dose, whereas the response of the Si diode decreases linearly to approximately 93% after 2x10(19) photons/cm(2).
    The Review of scientific instruments 09/2009; 80(9):093102. · 1.52 Impact Factor
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    ABSTRACT: This paper presents the development of a laser-driven plasma source for soft X-ray production in the 2-20 nm spectral range. In the experiment, a Nd:YAG laser (1064 nm, 800 mJ, 6 ns) is focused into a gas-target, that leads to the formation of a plasma, which in turn emits characteristic soft X-ray radiation. A flexible Kirkpatrick-Baez optics is developed for focusing, which provides broadband light steering due to grazing incidence reflection. The carbon-coated mirrors of this device are formed by bent silicon wafer slices, that allow continuous tuning to the desired curvatures. Structural and chemical surface analysis are shown by utilizing the described system. Results on near-edge X-ray absorption fine structure spectroscopy (NEXAFS) at the carbon K-edge are also presented. Hence, NEXAFS spectroscopy using a table-top XUV source can be considered as a highly surface sensitive fingerprint method for chemical analysis.
    Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009
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    ABSTRACT: Triggered by the roadmap of the semiconductor industry, tremendous progress has been achieved in the development of Extreme Ultraviolet (EUV) sources and high-quality EUV optical coatings in recent years, opening up also new fields of applications apart from microlithography, such as metrology, high-resolution microscopy, or surface analysis. The Laser-Laboratorium Göttingen has developed a laser-driven plasma source for generation of soft X-rays in the spectral range 2...20 nm. A Nd:YAG laser (1064 nm, 800 mJ, 6 ns) is focused into a gas-target leading to the formation of a plasma which in turn emits characteristic soft X-ray radiation. Hereby the main focus lies on wavelengths around 13.5 nm ("EUV" - future optical lithography) and the so called water window (2.2 nm...4.4 nm - "XUV") region. Depending on the employed target gas, narrow-band (e.g. O2 for EUV, N2 for XUV) as well as broad-band (e.g. Xe for EUV, Ar, Kr for XUV) spectra can be obtained. For focusing a flexible Kirkpatrick-Baez optics was developed, providing broad-band light steering due to grazing-incidence reflection. The carbon-coated mirrors of this device are formed by bent silicon wafer slices allowing continuous tuning to the desired curvatures. As an application of such a setup, results on near-edge X-ray absorption fine structure spectroscopy (NEXAFS) at the carbon K-edge will be presented. The investigated systems range from synthetic polymers (PMMA, PI) over organic substances (humic acids) to biological matter (lipids), delivering unique spectra for each compound. Thus NEXAFS spectroscopy using a table-top XUV source could be established as a highly surface sensitive fingerprint method for chemical analysis.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    05/2009;
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    ABSTRACT: In recent years, technological developments in the area of extreme ultraviolet lithography (EUVL) have experienced great improvements. So far, intense light sources based on discharge or laser plasmas, beam steering and imaging optics as well as sensitive detectors are available. Currently, applications of EUV radiation apart from microlithography, such as metrology, high-resolution microscopy, or surface analysis come more and more into focus. In this contribution we present an overview on the EUV/XUV activities of the Laser-Laboratorium Göttingen based on table-top laser-produced plasma (LPP) sources. As target materials gaseous or liquid jets of noble gases or solid Gold are employed. Depending on the applications, the very clean but low intense gaseous targets are mainly used for metrology, whereas the targets for high brilliances (liquid, solid) are used for microscopy and direct structuring. For the determination of interaction mechanisms between EUV radiation and matter, currently the solid Gold target is used. In order to obtain a small focal spot resulting in high EUV fluence, a modified Schwarzschild objective consisting of two spherical mirrors with Mo/Si multilayer coatings is adapted to this source. By demagnified (10x) imaging of the Au plasma an EUV spot of 3 μm diameter with a maximum energy density of ~1.3 J/cm2 is generated (pulse duration 8.8 ns). First applications of this integrated source and optics system reveal its potential for high-resolution modification and direct structuring of solid surfaces. For chemical analysis of various samples a NEXAFS setup was developed. It consists of a LPP, using gaseous Krypton as a broadband emitter in the water-window range, as well as a flat field spectrograph. The laboratory system is set to the XUV spectral range around the carbon K-edge (4.4 nm). The table-top setup allows measurements with spectral accuracy comparable to synchrotron experiments. NEXAFS-experiments in transmission and reflection are demonstrated. Beside chemical investigations, also microscopy applications are performed within the XUV spectral range. For this reason a water-window microscope was developed, based on a liquid argon LPP target. The XUV radiation is focused by a Cr/Sc multilayer mirror, leading to spectral narrow band radiation on the sample. For magnifying the sample, a Fresnel zone plate will be used with an outer zone width of 50 nm. Additionally to these applications, an EUV/XUV setup for structural analysis was developed. Using a spectral broad band emitting Xenon gaseous target combined with a grazing incidence optics (Kirkpatrick-Baez arrangement), it offers the possibility to perform angular resolved reflectivity-, diffraction- and scattering experiments as well as NEXAFS analysis in one setup. In completion to these experiments with LPP sources, an EUV/XUV Hartmann-type wavefront sensor has been developed in collaboration with DESY HASYLAB. It consists of a pinhole array, positioned in front of a XUV sensitive CCD camera with quantum converter. With custom-developed software the incident wavefront can be determined. This sensor is currently used at the free electron laser FLASH in Hamburg for beam characterization.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    05/2009;
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    ABSTRACT: Triggered by the roadmap of the semiconductor industry, tremendous progress has been achieved in the development of Extreme Ultraviolet (EUV) sources and high-quality EUV optical coatings in recent years, opening up also new fields of applications apart from microlithography, such as metrology, high-resolution microscopy, or surface analysis. The Laser-Laboratorium Göttingen has developed a laser-driven plasma source for generation of soft X-rays in the spectral range 2...20 nm. A Nd:YAG laser (1064 nm, 800 mJ, 6 ns) is focused into a gas-target leading to the formation of a plasma which in turn emits characteristic soft X-ray radiation. Hereby the main focus lies on wavelengths around 13.5 nm ("EUV" - future optical lithography) and the so called water window (2.2 nm...4.4 nm - "XUV") region. Depending on the employed target gas, narrow-band (e.g. O2 for EUV, N2 for XUV) as well as broad-band (e.g. Xe for EUV, Ar, Kr for XUV) spectra can be obtained. For focusing a flexible Kirkpatrick-Baez optics was developed, providing broad-band light steering due to grazing-incidence reflection. The carbon-coated mirrors of this device are formed by bent silicon wafer slices allowing continuous tuning to the desired curvatures. As an application of such a setup, results on near-edge X-ray absorption fine structure spectroscopy (NEXAFS) at the carbon K-edge will be presented. The investigated systems range from synthetic polymers (PMMA, PI) over organic substances (humic acids) to biological matter (lipids), delivering unique spectra for each compound. Thus NEXAFS spectroscopy using a table-top XUV source could be established as a highly surface sensitive fingerprint method for chemical analysis.
    Proc SPIE 05/2009;
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    ABSTRACT: We present an overview on the EUV/XUV activities of the Laser-Laboratorium Göttingen based on table-top laser-produced plasma (LPP) sources. As target materials, gaseous jets of noble gases or solid Gold are employed. In order to obtain high EUV fluence, a Schwarzschild objective consisting of two spherical mirrors with Mo/Si multilayer coatings is adapted to the source. By demagnified (10x) imaging of the Au plasma, an EUV spot with a maximum energy density of ∼1.3 J/cm2 is generated (3 μm diameter, pulse duration 8.8 ns). First applications of this system reveal its potential for high-resolution modification and direct structuring of solid surfaces. Additionally, an EUV/XUV setup for structural analysis was developed. Using a gas puff target combined with a grazing incidence optics (Kirkpatrick-Baez arrangement), it offers the possibility to perform angular resolved reflectivity, diffraction, and scattering experiments. For chemical analysis of various samples, an NEXAFS setup was built, based on gaseous Krypton as a broadband emitter in the water-window range around the carbon K-edge (4.4 nm). Here, proof-of-principle for NEXAFS with lab-scaled XUV sources is given on polyimide as a reference.
    Proc SPIE 05/2009;
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    ABSTRACT: In recent years, technological developments in the area of extreme ultraviolet lithography (EUVL) have experienced great improvements. Currently, the application of EUV radiation apart from microlithography comes more and more into focus. Main goal of our research is to utilize the unique interaction between soft x-ray radiation and matter for probing, modifying, and structuring solid surfaces. In this contribution we present a setup capable of generating and focusing EUV radiation. It consists of a table-top laser-produced plasma source. In order to obtain a small focal spot resulting in high EUV fluence, a modified Schwarzschild objective consisting of two spherical mirrors with Mo/Si multilayer coatings is adapted to this source, simultaneously blocking unwanted out-of-band radiation. By demagnified (10x) imaging of the plasma an EUV spot of 5 mum diameter with a maximum energy density of ~0.72 J/cm ^2 is generated (pulse length 8.8 ns). We present first applications of this integrated source and optics system, demonstrating its potential for high-resolution modification and structuring of solid surfaces. As an example, etch rates for PMMA, PC and PTFE depending on EUV fluences were determined, indicating a linear etch behavior for lower energy densities. In order to investigate changes of the chemical composition of PMMA induced by EUV radiation we present FTIR and NEXAFS measurements on irradiated samples. The latter were performed using the laboratory source tuned to the XUV spectral range around the carbon K-edge (lambda ~ 4.4 nm) and a flat-field spectrometer. For showing the potential of this setup, first damage tests were performed on grazing incidence gold mirrors. For these thin Gold films, threshold energy densities could be determined, scaling linear with the film thickness.
    Proc SPIE 05/2009;
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    ABSTRACT: The utilization of nanostructured materials for modern applications gained more and more importance during the last few years. As examples super-fluorescent quantum dots, the use of carbon nano tubes (CNTs) in microelectronics, electrospun fibers in filter membranes, thin film coatings for solar cells, mirrors or LEDs, semiconductor electronics, and functionalized surfaces may be named to address only a few topics. To optimize the systems and enable the full range of capabilities of nanostructures a thorough characterization of the surface-near topography (e.g. roughness, thickness, lateral dimension) as well as of the chemical composition is essential. As a versatile tool for spatial and chemical characterization XUV reflectometry, scatterometry and diffractometry is proposed. Three different experimental setups have been realized evaluating spectral resolved reflectance under constant incidence angle, angular resolved reflectance at a constant wavelength, or a combined approach using laboratory scaled XUV sources to gain insight into chemical composition, film thickness and surface/interface roughness. Experiments on near-edge X-ray absorption fine structure spectroscopy (NEXAFS) at the carbon K-edge have been performed. The investigated systems range from synthetic polymers (PMMA, PI) over organic substances (humic acids) to biological matter (lipids), delivering unique spectra for each compound. Thus NEXAFS spectroscopy using a table-top XUV source could be established as a highly surface sensitive fingerprint method for chemical analysis. Future extended experiments will investigate the silicon L-edge where e.g. silicon oxide interlayers below high-k or other nano-layered material on Sisubstrates depict a technological important group of composite systems.
    Proc SPIE 05/2009;
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    ABSTRACT: In order to perform material interaction studies with intense extreme ultraviolet (EUV) radiation, a Schwarzschild mirror objective coated with Mo/Si multilayers was adapted to a compact laser-driven EUV plasma source utilizing a solid Au target. By 10× demagnified imaging of the plasma a maximum pulse energy density of ∼0.73 J / cm <sup>2</sup> at a wavelength of 13.5 nm can be achieved in the image plane of the objective at a pulse duration of 8.8 ns. In this paper we present EUV photoetching rates measured for polymethyl methacrylate, polycarbonate, and polytetrafluoroethylene at various fluence levels. A linear dependence between etch depth and applied EUV pulse number could be observed without the necessity for any incubation pulses. By evaluating the slope of these data, etch rates were determined, revealing also a linear behavior for low fluences. A threshold energy density could not be observed. The slope of the linear etch regime as well as deviations from the linear trend at higher energy densities are discussed and compared to data known from deep UV laser ablation. Furthermore, the surface roughness of the structured polymers was measured by atomic force microscopy and compared to the nonirradiated polymer surface, indicating a rather smooth etch process (roughness increase of 20%–30%). The different shapes of the etch craters observed for the three polymers at high energy densities can be explained by the measured fluence dependence of the etch rates, having consequences for the proper use of polymer ablation for beam profiling of focused EUV radiation.
    Journal of Applied Physics 02/2009; · 2.21 Impact Factor
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    Proc SPIE 01/2009; 7361.
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    ABSTRACT: Triggered by the roadmap of the semiconductor industry, tremendous progress has been achieved in the development of extreme ultraviolet (EUV) sources and high-quality EUV optical coatings in recent years, opening up also new fields of applications apart from microlithography, such as metrology, high-resolution microscopy, or surface analysis. The Laser-Laboratorium Göttingen e.V. has developed a laser-driven plasma source for generation of soft X-rays in the spectral range 2...20 nm. A Nd:YAG laser (1064 nm, 800 mJ, 6 ns) is focused into a gas-target leading to plasma formation which in turn emits characteristic soft X-ray radiation. Depending on the employed target gas, narrow-band as well as broad-band spectra can be obtained. For focusing a Kirkpatrick-Baez optics is used, providing broad-band light steering due to grazing-incidence reflection. The mirrors of the arrangement are formed by bent silicon wafer slices allowing continuous tuning to the desired curvatures. The motorized control offers active adaption of surface shape and incidence angles even in high vacuum, to various experimental demands (e.g. focusing on different sites, beam collimation). For reduction of aberrations the optical system was fine-adjusted with the help of a Hartmann-Shack wavefront sensor in the visible spectral range. The wave propagation properties were determined and compared to calculations performed with ZEMAX. From the difference between calculated phase and measured wavefront direct information about the figure error between perfect and real mirrors could be obtained.
    Proc SPIE 09/2008;