EUV has long been hailed as the next generation lithography technology. Its adoption into high volume manufacturing (HVM), however, has been delayed several technology nodes due to technical issues, many of which can be attributed to the EUV source performance. Today’s EUV lithography scanners are powered by laser produce plasma (LPP) sources. They have issues with power scaling beyond 300 W, reliability and contamination. Free Electron Lasers (FELs) have been considered as an alternative EUV source. Advantages of accelerator based sources are the maturity of the accelerator technology, lack of debris/contamination, and ability to provide high power. Industry turned away from this technology because of the requirement to feed up to 10 scanners from one linear FEL to make it economically feasible, the large footprint, and generation of radioactive byproducts. All of these issues are overcome in the presented concept using a compact storage ring with steady-state FEL lasing action. At 1 kW output power, comparable cost and footprint to an LPP source, this source is ideally suited for use on a single scanner and promises reliable, contamination free operation. FEL action in the storage ring is sustained by operating the FEL well below the saturation regime and preserving the equilibrium low emittance and energy distribution of the ring.
The Lyncean Compact Light Source (CLS) is a true miniature synchrotron x-ray source with undulator output x-ray characteristics (inherently monochromatic, tunable, high flux). The compact size (8m x 4m) is accomplished by employing a low energy (45 MeV) electron beam storage ring combined with a sub-micrometer period “laser undulator” replacing the permanent magnets of traditional undulators. The output beam of the Lyncean CLS is axially symmetric with 4 mrad beam divergence, a 4% bandwidth and tunable from 8 to 35 keV by changing the energy of the stored electron beam. It delivers 1010 photons per second to experimental end stations located outside of the CLS shielded enclosure.
The first commercial installation of a Lyncean CLS is at the Technical University Munich (TUM) in Germany. Applications pursued there are primarily Talbot grating based multi-modal imaging and tomography (quantitative absorption/phase contrast, dark field) and high-resolution x-ray tomography. The Lyncean CLS is very well matched to these measurements due to the inherent coherence property, Monochromaticity (no beam hardening + quantitation) and the high flux. Analytical applications using specifically developed multilayer focusing optics have been demonstrated at the Lyncean factory in the USA. Protein crystallography with freely selectable x-ray energy to enable advanced phasing techniques such as single wavelength anomalous dispersion (SAD) are possible. Other examples include powder diffraction and small angle scattering to name a few.
Operating the Lyncean CLS has been made extremely simple for users. The complexity of the system is packaged into easy to use interfaces enabling non-experts to run the machine after one week of training. The special characteristic of the Lyncean CLS of producing a truly symmetric and monochromatic beam without contamination by higher x-ray energies (compared to traditional synchrotrons) allows very simple beam transport systems and experimental stations with relaxed shielding requirements to be utilized.
Benjamin Hornberger, Hrishikesh Bale, Arno Merkle, Michael Feser, William Harris, Sergey Etchin, Marty Leibowitz, Wei Qiu, Andrei Tkachuk, Allen Gu, Robert Bradley, Xuekun Lu, Philip Withers, Amy Clarke, Kevin Henderson, Nikolaus Cordes, Brian Patterson
X-ray microscopy (XRM) has emerged as a powerful technique that reveals 3D images and quantitative information of interior structures. XRM executed both in the laboratory and at the synchrotron have demonstrated critical analysis and materials characterization on meso-, micro-, and nanoscales, with spatial resolution down to 50 nm in laboratory systems. The non-destructive nature of X-rays has made the technique widely appealing, with potential for “4D” characterization, delivering 3D micro- and nanostructural information on the same sample as a function of sequential processing or experimental conditions. Understanding volumetric and nanostructural changes, such as solid deformation, pore evolution, and crack propagation are fundamental to understanding how materials form, deform, and perform. We will present recent instrumentation developments in laboratory based XRM including a novel in situ nanomechanical testing stage. These developments bridge the gap between existing in situ stages for micro scale XRM, and SEM/TEM techniques that offer nanometer resolution but are limited to analysis of surfaces or extremely thin samples whose behavior is strongly influenced by surface effects. Several applications will be presented including 3D-characterization and in situ mechanical testing of polymers, metal alloys, composites and biomaterials. They span multiple length scales from the micro- to the nanoscale and different mechanical testing modes such as compression, indentation and tension.
An absolute efficiency measurement technique for Fresnel zone plates using an electron impact micro-focus laboratory
X-ray source (Lα line of Tungsten at 8.4 KeV) is demonstrated. A quasi-monochromatic x-ray image of a zone plate was
obtained employing a pair of copper and cobalt filters. Applying this method to zone plates optimizes the zone plate
fabrication process and provides the ability to explore zone geometry to achieve the best possible efficiency. Several
zone plate parameters were tested with first order efficiency measuring from 1% to 29%.
While electron microscopes and AFMs are capable of high resolution imaging to molecular levels, there is an ongoing
problem in integrating these results into the larger scale structure and functions of tissue and organs within a complex
organism. Imaging biological samples with optical microscopy is predominantly done with histology and
immunohistochemistry, which can take up to a several weeks to prepare, are artifact prone and only available as
individual 2D images. At the nano resolution scale, the higher resolution electron microscopy and AFM are used, but
again these require destructive sample preparation and data are in 2D. To bridge this gap, we describe a rapid non
invasive hierarchical bioimaging technique using a novel lab based x-ray computed tomography to characterize complex
biological organism in multiscale- from whole organ (mesoscale) to calcified and soft tissue (microscale), to subcellular
structures, nanomaterials and cellular-scaffold interaction (nanoscale). While MicroCT (micro x-ray computed
tomography) is gaining in popularity for non invasive bones and tissue imaging, contrast and resolution are still vastly
inadequate compared to histology. In this study we will present multiscale results from a novel microCT and nanoCT
(nano x-ray tomography system). The novel MicroCT can image large specimen and tissue sample at histology
resolution of submicron voxel resolution, often without contrast agents, while the nanoCT using x-ray optics similar to
those used in synchrotron radiation facilities, has 20nm voxel resolution, suitable for studying cellular, subcellular
morphology and nanomaterials. Multiscale examples involving both calcified and soft tissue will be illustrated, which
include imaging a rat tibia to the individual channels of osteocyte canaliculli and lacunae and an unstained whole murine
lung to its alveoli. The role of the novel CT will also be discussed as a possible means for rapid virtual histology using a
biopsy of a human regenerated bone sample done without contrast agents and that of other soft tissues with contrast
agents. Comparison between histology, SEM and MRI will be given.
X-ray computed tomography (XCT) is a powerful nondestructive 3D imaging technique, which enables the visualization of the three dimensional structure of complex, optically opaque samples. High resolution XCT using Fresnel zone plate lenses has been confined in the past to synchrotron radiation centers due to the need for a bright and intense source of x-rays. This confinement severely limits the availability and accessibility of x-ray microscopes and the wide proliferation of this methodology. We are describing a sub-50nm resolution XCT system operating at 8 keV in absorption and Zernike phase contrast mode based on a commercially available laboratory x-ray source. The system utilizes high-efficiency Fresnel zone plates with an outermost zone width of 35 nm and 700 nm structure height resulting in a current spatial resolution better than 50 nm. In addition to the technical description of the system and specifications, we present application examples in the semiconductor field.
The diffraction efficiencies of a Fresnel zone plate (ZP), fabricated by Xradia Inc. using the electron-beam writing technique, were measured using polarized, monochromatic synchrotron radiation in the extreme ultraviolet wavelength range 3.4-22 nm. The ZP had 2 mm diameter, 3330 zones, 150 nm outer zone width, and a 1 mm central occulter. The ZP was supported by a 100 nm thick Si3N4 membrane. The diffraction patterns were recorded by CMOS imagers with phosphor coatings and with 5.2 μm or 48 μm pixels. The focused +n orders (n=1-4), the diverging -1 order, and the undiffracted 0 order were observed as functions of wavelength and off-axis tilt angle. Sub-pixel focusing of the +n orders was achieved. The measured efficiency in the +1 order was in the 5% to 30% range with the phase-shift enhanced efficiency occurring at 8.3 nm where the gold bars are partially transmitting. The +2 and higher order efficiencies were much lower than the +1 order efficiency. The efficiencies were constant when the zone plate was tilted by angles up to ±1° from the incident radiation beam. This work indicates the feasibility and benefits of using zone plates to measure the absolute EUV spectral emissions from solar and laboratory sources: relatively high EUV efficiency in the focused +1 order, good out-of-band rejection resulting from the low higher-order efficiencies and the ZP focusing properties, insensitivity to (unfocused) visible light scattered by the ZP, flat response with off-axis angle, and insensitivity to the polarization of the radiation based on the ZP circular symmetry. EUV sensors with Fresnel zone plates potentially have many advantages over existing sensors intended to accurately measure absolute EUV emission levels, such as those implemented on the GOES N-P satellites that use transmission gratings which have off-axis sensitivity variations and poor out-of-band EUV and visible light rejection, and other solar and laboratory sensors using reflection gratings which are subject to response variations caused by surface contamination and oxidation.
X-ray imaging offers a number of unique properties that are favorable for NDE applications, including large penetration depth, elemental specificity, and relatively low radiation damage. While direct-projection type x-ray systems with a few um resolution have been widely deployed, recent advances in x-ray optics and imaging methodology have lead to lens-based x-ray microscopes with better than 60-nm resolution, and with integrated 3D imaging and material analysis capabilities. Used independently or in combination with established techniques based on visible light and electron microscopy, these new high-resolution x-ray systems introduces many attractive new capabilities for studying structures at micrometer to tens-of-nm scale.
The spatial resolution is a key optical parameter characterizing the performance of an imaging microscope. Zone plate based x-ray microscopy offers the highest spatial resolution over the whole electromagnet wave spectrum. Sub-20 nm resolution have been demonstrated with soft x-rays and sub-60 nm resolution have been obtained with multikeV x-rays using a laboratory source. There are two simple pathways to achieve sub-10 nm resolution x-ray imaging: (1) improving the fabrication technology to produce zone plates with an outermost zone width less than 10 nm and (2) using a higher diffraction order (such as the third diffraction order) of a currently available zone plate.
Soft x-ray scanning transmission x-ray microscopy allows one to image dry and wet environmental science, biological, polymer, and geochemical specimens on a nanoscale. Recent advances in instrumentation at the X-1A beamline at the National Synchrotron Light Source at Brookhaven National Laboratory are described. Recent results on Nomarski differential phase contrast and first results on investigations at the oxygen K edge and iron L edge of hydrous ferric oxide transformations are presented.
An integrating solid state detector with segmentation has been developed that addresses the needs in scanning transmission x-ray microscopy below 1 keV photon energy. The detector is not cooled and can be operated without an entrance window which leads to a total photon detection efficiency close to 100%. The chosen segmentation with 8 independent segments is matched to the geometry of the STXM to maximize image mode flexibility. In the bright field configuration for 1 ms integration time and 520 eV x-rays the rms noise is 8 photons per integration.
Scanning transmission x-ray microscopes (STXM) are well matched to the optics of high resolution monochromators, offer a variety of imaging modes and can minimize radiation damage to the specimen. We describe the Stony Brook STXM at the NSLS. This microscope is used for a variety of studies by many users; we briefly outline its use for studies of hydrated colloidal system and for dark field microscopy on immunogold labeled specimens as examples. In order to keep pace with developments in zone plate optics, spectroscopy and a variety of imaging modalities, the microscope is being redesigned and its characteristics are discussed. Its preliminary x-ray detector will be a new multiware proportional counter with high count rate capability.
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