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The Lynx x-ray mission will push thin film filters to larger apertures and thinner profiles than those of any preceding mission. We present a study of the uniformity of deposition with existing technology and the consequences of oxidation on 10-15 nm thick Al films on LUXFilm® polyimide. From visible and infrared transmission measurements of thin aluminum filters and the results of a photon-driven oxidation study at the Beamline 1 of the Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology, we conclude that, from a deposition and oxidation standpoint, Al optical blocking layers at this thickness are viable.

A critical component of high-performance EUV lithography source optics is the reflecting multilayer coating. The ideal multilayer will have both high reflectance and high stability to thermal load. Additionally the capping layers must provide resistance to degradations from exposure to an EUV source, and also be compatible with, or enhance, the systems used for cleaning an exposed multilayer coating. We will report on the results of development of C and B4C stabilized Mo/Si multilayers used to increase the as-deposited peak reflectivity (Rp) as well as decreasing the loss of peak reflectivity (Rp) as a function of annealing temperature. Previous results demonstrate that these layers prevent loss of Rp for temperatures up to 600o C. Results on the use of reactively-sputtered oxide capping layers such as SiO 2 and ZrO 2 will be presented as well, along with results of exposure testing. The deposition is performed in a dual processchamber inline magnetron system, using reactive sputtering for the production of capping layers. The reflectometer and exposure apparatus at the NIST Physics Laboratory is used for evaluation of the performance. Exposure results on the resistance to oxidation in the presence of water vapor will be presented and discussed.

This paper reports on an all-out effort to reduce the intersite gap of the resist outgassing contamination growth in the results obtained under the round-robin scheme. All test sites collaborated to determine the causes of such gaps. First, it was determined that wafer temperature during exposure could impact the amount of contamination growth. We discovered a huge intersite gap of wafer temperatures among the sites by using a wafer-shaped remote thermometer with wireless transmitting capability. Second, whether the contamination-limited regime was attained during testing could have been another primary root cause for such a difference. We found that for one of the model resists whose protecting unit had lower activation energy and molecular weight the contamination-limited regime was insufficient at one test site. Third, the ratio of the exposed area to pumping speed is necessary to equalize contamination growth. We validated the effect of matching the ratio of exposure area to pumping speed on reducing the intersite gap. This study and the protocols put in place should reduce the intersite gap dramatically.

The NIST Extreme Ultraviolet (EUV) Reflectometry Facility was designed in the 1990s to accommodate the largest multilayer optics envisioned at that time. However, with increasing power requirements for an EUV scanner, source collection optics have grown larger and more steeply curved than the original design would allow. To accommodate these changes, the mechanical and operational parameters of the facility have been upgraded. To access the entire surface of a larger optic, an auxiliary off-axis rotation stage has been installed allowing an increase in maximum optic size from 350 mm to 450 mm. Likewise, to deal with the deeper sags and steeper slopes of these optics, we have had to significantly expand our data analysis capabilities. In order to make these measurements, the incident radiation is reflected out of the vertical plane, allowing for measurements of effectively unpolarized radiation, an advantage for EUV lithography optics such as source collectors.

Laser-produced plasma (LPP) sources for extreme ultraviolet lithography (EUVL) systems utilize CO 2 lasers operating with wavelength 10.6μm. Since multilayer-coated optics have high reflectivity for this infrared radiation (IR), a significant and detrimental amount of IR is passed through the EUVL system. One method to remove the IR from the system is to utilize a binary diffraction grating. When this grating is applied directly to the surface of the primary collector optic of the source, the majority of the IR is diverted outside the radius of the exit aperture at the intermediate focus (IF). This paper will report details on the performance of a full size (410mm diameter) Demonstration Collector utilizing IR rejection (IRR) technology with the capability to produce over 125X suppression of IR, equaling the performance of a IR spectral filter. Additional details will be reported on the technology development and use of a glassy smoothing layer to enable high EUV performance, a weighted average multilayer reflectance of 50.9% for unpolarized EUV radiation.

EUV photoresists are considered as a potential source of optics contamination, since they introduce irradiation induced outgassing in the EUV vacuum environment. Therefore, before these resists can be used on e.g. ASML NXE:3100 or NXE:3300, they need to be tested in dedicated equipment according to a well-defined procedure, which is based on exposing a witness sample (WS) in the vicinity of a simultaneously exposed resist as it outgasses. Such an outgassing test infrastructure is available at many sites, but exposure modes on the witness sample and wafer can be significantly different, which potentially could lead to different test results. In this investigation, we first explored in more detail the relationship between resist outgassing as measured by RGA (Residual Gas Analysis) and the carbon growth obtained in the WS test. A good correlation was found by using a timeintegrated and mass-weighted sum of the RGA-measured mass peaks. Next, the impact of the resist exposure mode on the WS contamination result was investigated at imec, where the outgas test setup allows to expose the wafer with EUV irradiation as well as electrons in the same vacuum environment. It was found that minor differences observed in the WS test results, can be explained by adequate characterization of exposure intensity distribution and dose control. Finally the WS test results at imec from the different exposure modes were compared to the test results at NIST. The small differences in contamination that were observed could be explained by differences in test procedure, by using the time dependent RGA approach. From the combined work on outgassing measurements and WS contamination testing we have significantly improved our understanding of the relationship between outgassing and contamination processes induced by EUV photons and electrons. We have also demonstrated how to compare results obtained at different outgas testing sites, which is important in quantifying the potential risk to EUV device manufacturing posed by resist outgassing.

We report on optics contamination rates induced by exposure to broad-bandwidth, high-intensity EUV radiation peaked near 8 nm in a new beamline at the NIST synchrotron. The peak intensity of 50 mW/mm2 allows extension of previous investigations of contamination by in-band 13.5 nm radiation at intensities an order of magnitude lower. We report nonlinear pressure and intensity scaling of the contamination rates which is consistent with the earlier lower-intensity studies. The magnitude of the contamination rate per unit EUV dose, however, was found to be significantly lower for the lower wavelength exposures. We also report an apparent dose-dependent correlation between the thicknesses as measured by spectroscopic ellipsometry and XPS for the carbon deposits created using the higher doses available on the new beamline. It is proposed that this is due to different sensitivities of the metrologies to variations in the density of the deposited C induced by prolonged EUV irradiation.

Before being used in an extreme-ultraviolet (EUV) scanner, photoresists must be qualified to ensure that they will not excessively contaminate the scanner optics or other parts of the vacuum environment of the scanner. At the National Institute of Standards and Technology we have designed and constructed a high-throughput beamline on the Synchrotron Ultraviolet Radiation Facility (SURF III) in order to provide data on the contamination potential of the outgas products of a candidate resist by simultaneously irradiating a witness substrate and a nearby resist-coated wafer with EUV radiation, the so called witness sample test that is currently the resist qualification method required by ASML. We will present results from four sample resists that were subjected to the test. Although the witness-sample test based on irradiating the resist with EUV radiation at 13.5 nm most closely reproduces conditions in a scanner, the limited availability of suitable EUV sources to conduct such tests has led to development of an alternative method which uses e-beam irradiation in place of EUV radiation. We will also present the results of a comparison of these two methods.

The effort to develop EUVL has presented the metrologist with a set of unique challenges both in radiometry and in measuring reflectivity. Since the inception of the National Institute of Standards and Technology's (NIST's) EUV-detector-based radiometry program in 1970, there has been little need for accurate measurements of pulsed EUV sources, and the radiometric techniques in this spectral range were all tailored to continuous wave (cw) measurements. Now, however, EUV sources bright enough to be suitable for EUVL are all based on very high temperature plasmas that must be generated by extremely high power pulses. Recently some experience in pulsed radiometry has been gained through the creation of standards for pulsed radiometry connected with DUV lithography with its pulsed 248- and 193-nm laser sources. However, important differences in the spectral, temporal, and spatial characteristics of the EUV sources as contrasted with the DUV laser sources necessitate specialized approaches, still under development, that are described in Sec. 29.3. Soon after the demonstration in 1986 of the first practicable EUV mirror in the form of a Mo∕Si multilayer, NIST established a capability to measure the reflectivity of EUV mirrors for such applications as solar astronomy, plasma diagnostics, EUV laser development, and EUV microscopy. At that point, measurement accuracy of order 0.01 nm in wavelength and 2% in reflectivity seemed to provide more than adequate characterization for the applications at hand. However, the advent of EUVL made the demands much more stringent due to the imaging and illumination needs of the process. NIST has continued to perform EUV mirror calibrations since the program's inception, has increased its capabilities to meet many of the reflectometry demands of EUVL, and will continue to expand and improve the program to help meet the future needs of the industry.

The higher energy associated with extreme ultraviolet (EUV) radiation coupled with the high absorptivity of most organic polymers at these wavelengths should lead to increased excited state population and higher quantum yields of photoproducts. Polymers representative of those commonly employed in resists as well as some model polymers were selected for this study. Polymer photochemistry at EUV was catalogued as to the effect of absorbed 13.4-nm radiation on a polymer's quantum yield of chain scission (Φs) and crosslinking (Φx). In selected cases, the chain scission and crosslinking quantum yields were also compared to those previously determined at 157-, 193- and 248-nm. It was found that quantum yield values were over a magnitude greater at EUV relative to optical wavelengths.

Optics in EUVL exposure tools are known to suffer reflectivity degradation, mostly from the buildup of carbon. The sources of this carbon have been difficult to identify. The vacuum cleanliness in the preproduction micro-exposure tools is monitored with a residual gas analyzer, but they have not shown carbon-containing species in sufficient concentration to account for the observed carbon buildup seen in these tools. We have developed a technique based on cryo trapping followed by gas chromatography with mass spectrometry analysis that is more sensitive to less-volatile compounds. We will present sample data on typical vacuum systems as well as a preliminary analysis of the Intel micro-exposure tool.

The primary, publicly reported cause of optic degradation in pre-production extreme-ultraviolet (EUV) lithography systems is carbon deposition. This results when volatile organics adsorb onto optic surfaces and then are cracked by EUV-induced reactions. Hence the deposition rate depends on the adsorption-desorption kinetics of the molecule-surface system as well as the basic photon-stimulated reaction rates, both of which may vary significantly for different organic species. The goal of our ongoing optics-contamination program is to estimate the contamination rate of species expected in the tool environment by exposing samples to in-band 13.5 nm light from our synchrotron in the presence of fixed partial pressures of admitted gases. Here we report preliminary results of contamination rates on TiO2-capped samples for species observed in resist-outgassing measurements (benzene, isobutene, toluene and tert-butylbenzene) in the pressure range (10-6 to 10-4) Pa which all display an unexpected logarithmic dependence on pressure. This scaling is in agreement with previous EUV exposures of other species at NIST as well as independent measurements of coverage performed at Rutgers University. These results are consistent with a molecular desorption energy that decreases with coverage due to molecular interactions (Temkin model). Use of the proper scaling law is critical when estimating optic lifetimes by extrapolating over the 3-to-6 orders of magnitude between accelerated-testing and tool-environment partial pressures.

As part of its role in providing radiometric standards in support of industry, the National Institute of Standards and Technology has been active in advancing extreme ultravio let dosimetry on various fronts. Recently, we undertook a major effort in accurately measuring the sensitivity of three extreme ultraviolet photoresists. It has been common practice to use photoresists as a transfer “standards” to dete rmine the intensity and uniformity of the radiation transmitted by extreme ultraviolet steppers. In response to preliminary results from Lawr ence Berkeley National Laboratory that showed that two “standard” photoresists were almost twice as sensitive as had been previously believed, NIST carried out similar measurements and confirmed the Berkeley resu lts. However, we have found that the assumed sensitivities are more a question of system calibration than of absolute resi st dose sensitivity. We will describe the facility we used to make these measurements. Photoresists make less than perfect radiometers. They are very non-linear, sensitive to atmosphere, and difficult to calibrate. All of these characteristics led to the disparate re sults in assumed sensitivity values. We have developed an alternate wafer-plane dosimeter based on image plates. The dosimeter is linear over several orders of magnitude, comparatively insensitive to atmosphere, and can be re-ca librated as necessary. Moreover it can pass through a stepper as any other wafer. We will describe this dosimeter in detail. Keywords: radiometry, dosimet ry, photoresists, image plates

The photon-stimulated emission of organic molecules from the photoresist during exposure is a serious problem for extreme-ultraviolet lithography (EUVL) because the adsorption of the outgassing products on the EUV optics can lead to carbonization and subsequent reflectivity loss. In order to accurately quantify the total amount of outgassing for a given resist during an exposure, we have constructed a compact, portable chamber that is instrumented with a spinning rotor gauge and a capacitance diaphragm gauge that, unlike the more commonly used ionization gauge or quadrupole mass spectrometer, provides a direct and accurate measurement of the total pressure that is largely independent of the composition of the outgas products. We have also developed a method to perform compositional analysis on the outgas products and, more generally, on any contaminants that might be present in the stepper vacuum. The method involves collecting the vacuum contaminants in a trap cooled to liquid-nitrogen temperature. Once collected, the products from the trap are transferred to a system for analysis with gas chromatography with mass spectrometry. We will describe the workings of the instruments in detail as well as results of initial tests.

Extreme ultraviolet (EUV) photoresists are known to outgas during exposure to EUV radiation in the vacuum environment. This is of particular concern since some of the outgassed species may contaminate the nearby EUV optics and cause a loss of reflectivity and therefore throughput of the EUV exposure tools. Due to this issue, work has been performed to measure the species and quantities that outgas from EUV resists. Additionally, since the goal of these measurements is to determine the relative safety of various resists near EUV optics, work has been performed to measure the deposition rate of the outgassed molecules on Mo/Si-coated witness plate samples. The results for various species and tests show little measurable effect from resist components on optics contamination with modest EUV exposure doses.

Multilayers are artificially layered structures that can be used to create optics and optical elements for a broad range of x-ray wavelengths, or can be optimized for other applications. The development of next generation x-ray sources (synchrotrons and x-ray free electron lasers) requires advances in x-ray optics. Newly developed multilayer-based mirrors and optical elements enabled efficient band-pass filtering, focusing and time resolved measurements in recent FLASH (Free Electron LASer in Hamburg) experiments. These experiments are providing invaluable feedback on the response of the multilayer structures to high intensity, short pulsed x-ray sources. This information is crucial to design optics for future x-ray free electron lasers and to benchmark computer codes that simulate damage processes.

Endurance testing of Ru-capped multilayer mirrors (MLMs) at the NIST synchrotron facility has revealed that the damage resulting from EUV irradiation in a water-dominated environment is nonlinear and may be influenced by competing oxidation and carbon-deposition processes. Concurrent results from two different environmental chambers reveal non-intuitive relationships between reflectivity loss and the admitted water-vapor partial pressure, the ambient background-gas composition, the presence or absence of hot filaments in the chamber, the EUV intensity and the irradiation dose. We discuss possible mechanisms and propose further experiments to test them. Determining the MLM lifetime from accelerated tests is a very difficult task. It is crucial that any lifetime testing procedure involves duplicate exposures for consistency, and, if possible, testing in multiple facilities.

Exposure of collector mirrors facing the hot, dense pinch plasma in plasma-based EUV light sources remains one of the highest critical issues of source component lifetime and commercial feasibility of EUV lithography technology. Studies at Argonne have focused on understanding the underlying mechanisms that hinder collector mirror performance under Sn exposure and developing methods to mitigate them. Both Sn ion irradiation and thermal evaporation exposes candidate mirrors tested (i.e., Ru, Rh and Pd) in the experimental facility known as IMPACT (Interaction of Materials with charged Particles and Components Testing). Studies have led to an understanding of how Sn energetic ions compared to Sn thermal atoms affect three main surface properties of the collector mirror: 1) surface chemical state, 2) surface structure and 3) surface morphology. All these properties are crucial in understanding how collector mirrors will respond to Sn-based EUV source operation. This is primarily due to the correlation of how variation in these properties affects the reflectivity of photons in the EUV spectral range of interest (in-band 13.5-nm). This paper discusses the first property and its impact on 13.5-nm reflectivity. Investigation in the IMPACT experiment has focused on Sn thermal and energetic particle exposure on collector mirrors (Ru, Pd and Rh) and its effect on mirror performance as a function of incident thermal flux, incident ion flux, incident angle and temperature. This is possible by a new state-of-the-art in-situ EUV reflectometry system that measures real time relative EUV reflectivity at 15-degree incidence and 13.5-nm during Sn exposure. These results are then compared to at-wavelength EUV reflectivity measurements using the newly upgraded NIST-SURF facility. Sn energetic ions at 1- keV and fluxes of about 1013 cm-2s-1 are used in conjunction with a moderate flux Sn evaporative source delivering Sn fluences ranging from 1015-1017 cm-2. The temperature of the mirror sample is locally varied between 25 and 200 C with the chemical state of the surface simultaneously monitored using X-ray photoelectron spectroscopy, and lowenergy ion scattering spectroscopy. Results demonstrate the balance between energetic and thermal Sn has on the total Sn surface fraction during exposure and its effect on the structural and reflective properties of the mirror surface.

Recently, while performing extensive EUV irradiation endurance testing on Ru-capped multilayer mirrors in the presence of elevated partial pressures of water and hydrocarbons, NIST has observed that the amount of EUV-induced damage actually decreases with increasing levels of water vapor above {approx} 5 x 10{sup -7} Torr. It is thought that the admitted water vapor may interact with otherwise stable, condensed carbonaceous species in an UHV vacuum system to increase the background levels of simple gaseous carbon-containing molecules. Some support for this hypothesis was demonstrated by observing the mitigating effect of very small levels of simple hydrocarbons with the intentional introduction of methyl alcohol in addition to the water vapor. It was found that the damage rate decreased by at least an order of magnitude when the partial pressure of methyl alcohol was just one percent of the water partial pressure. These observations indicate that the hydrocarbon components of the vacuum environment under actual testing conditions must be characterized and controlled to 10{sup -11} Torr or better in order to quantify the damage caused by high levels of water vapor. The possible effects of exposure beam size and out-of-band radiation on mirror lifetime testing will also be discussed.

The Multi-order Solar EUV Spectrograph (MOSES) is a slitless spectrograph designed to study solar He II emission at 303.8 Angstroms, to be launched on a sounding rocket payload. One difference between MOSES and other slitless spectrographs is that the images are recorded simultaneously at three spectral orders, m = -1,0, +l. Another is the addition of a narrow-band multilayer coating on both the grating and the fold flat, which will reject out-of-band lines that normally contaminate the image of a slitless instrument. The primary metrics f a the mating were high peak reflectivity and suppression of Fe XV and XVI emission lines at 284 Angstroms and 335 Angstroms, respectively. We chose B4C/Mg2Si for our material combination since it provides better values for all three metrics together than the other leading candidates Si/Ir, Si/B4C or Si/SiC. Measurements of witness flats at NIST indicate the peak reflectivity at 303.6 is 38.5% for a 15 bilayer stack, while the suppression at 284 Angstroms, is 4.5x and at 335 Angstroms is 18.3x for each of two reflections in the instrument. We present the results of coating the MOSES flight gratings and fold flat, including the spectral response of the fold flat and grating as measured at NIST's SURF III and Brookhaven's X24C beamline.

There are many obstacles in the path to the commercialization of EUV lithography including optics lifetime and source power. The Photon Physics Group at the National Institute of Standards and Technology has programs to support the extreme-ultraviolet source and optics development community in their efforts to meet the needs of lithography tool makers. Extreme-ultraviolet detector and optics metrology have been key elements of the Photon Physics Group program for over a decade, and this program has expanded recently to allow the calibration of assembled instruments for source development metrology. This program also includes a dedicated beamline for the exposure of multilayer optics in a low-pressure water atmosphere to test the performance of optics under irradiation conditions similar to those expected in a stepper's projection optics box. In this paper we will outline our programs in multilayer optics testing and at-wavelength detector and optics metrology including descriptions of facilities, capabilities and future plans to further support the efforts to commercialize this important technology.

Silicon capped [Mo/Si] multilayer mirrors (MLM’s) can undergo oxidation by the combined effects of radiation (Extreme Ultraviolet [EUV], electron) and water vapor. This parametric study provides silicon-capped MLM oxidation rate data. The goal of this study was to determine the dependence of silicon oxidation on water vapor pressure and radiation flux density over three orders of magnitude. Previous work1 has shown that electron and 95.3 eV EUV exposures produce similar oxidation. The present study verifies that correlation and examines the effects of EUV and electron flux on the oxidation rate of the Si-capping layer. E-beam and EUV exposed areas on silicon-capped MLM samples were analyzed following radiation exposure by Auger depth profiling to determine the thickness of the oxide grown. A ruthenium (Ru) capped MLM was also exposed for 4-hours, however it showed very little oxidation under the most extreme conditions of our test matrix. Also the effect of varying the primary e-beam voltage (0.5-2.0 keV) on Si-capped MLM was examined, which showed that exposures in the 1-2 keV range produce similar results.

The reflectance stability of multilayer coatings for extreme ultraviolet lithography (EUVL) in a commercial tool environment is of utmost importance to ensure continuous exposures with minimum maintenance cost. We have made substantial progress in designing the protective capping layer coatings, understanding their performance and estimating their lifetimes based on accelerated electron beam and EUV exposure studies. Our current capping layer coatings have about 40 times longer lifetimes than Si-capped multilayer optics. Nevertheless, the lifetime of current Ru-capped multilayers is too short to satisfy commercial tool requirements and further improvements are essential.

Currently the most demanding application of extreme-ultraviolet (EUV) optics is in lithography. A commercial extreme-ultraviolet stepper will likely have six or more normal-incidence reflective optics, and the largest of these will be tens of cm in diameter. Each of the Mo/Si multilayer stepper mirrors must have the highest attainable reflectivity at 13 nm, but more importantly the central wavelength of the reflectivity must be controlled to better than 0.01 nm and the peak reflectivity of the mask reticle to better than 0.1 percent. In order to meet these demands, our group at the National Institute of Standards and Technology (NIST) has implemented several improvements to our reflectometer. Additionally, the recent upgrade of the Synchrotron Ultraviolet Radiation Facility (SURF III) allows reliable operation at a variety of stored beam energies. Utilizing this capability, and a variety of filters, we analyzed the out-of-band radiation in the system. Under optimum conditions, the out-of-band contribution of the beam incident on the sample is held to 0.4 percent, and is primarily due to correctable effects of near-band scatter. We estimate that our total uncertainty, due to both systematic effects (accuracy of our out-of-band corrections) and random effects (noise, optics heating, etc.) is better than 0.3 percent. We will also discuss improvements that have been designed and are yet to be implemented.

We have recently installed a new sample chamber at the NIST/DARPA EUV Reflectometry Facility at the National Institute of Standards and Technology. The chamber replaces a much smaller system on Beamline 7 at the Synchrotron Ultraviolet Radiation Facility that was commissioned almost ten years ago as a dedicated facility for the measurement of normal-incidence extreme ultraviolet optics used in lithography development, astronomy, and plasma physics. The previous measurement chamber was limited to optics less than 10 cm in diameter, and, thus, we were not able to measure many of the optics used in modern telescopes and extreme ultraviolet lithography steppers. The new chamber was designed to accommodate optics up to 36 cm in diameter and weighing up to 40 kg, and with modifications will be able to measure optics up to 50 cm in diameter. It has three translation and three rotation axes for the sample and two rotation axes for the detector, with an accuracy of better than 0.5 mm in translation and 0.04o in rotation. We will describe design considerations, performance of the positioning mechanisms, and initial reflectivity measurements of both curved and flat surfaces.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

NIST has a long-standing program for the calibration of extreme ultraviolet optical components. Early activities, which began with the advent of the Synchrotron Ultraviolet Radiation Facility (SURF) almost 40 years ago, centered on the development and characterization of detectors for extreme ultraviolet (EUV) radiation. About a decade ago the program was expanded to include reflectometry of normal- incidence EUV multilayer optics. Both calibrated detectors and EUV optics are used by researchers in private industry, academia, and government, in such diverse fields as EUV lithography, astronomy, and plasma physics. Since the inception of SURF, nearly 800 transfer standard photodiodes have been issued to customers, and over 500 measurements of other EUV optical components have been made. NIST researchers, in collaboration with U.S. companies, have developed new, high-quality radiometric detectors for use throughout the EUV spectral range. We will discuss the history of NIST's involvement in EUV metrology and offer examples of our recent work.

Superpolished optical flats with high spatial frequency roughness below 0.1 nm have been commercially available for years. However, it is much more difficult to obtain figured optics of similar quality. We have obtained and tested the finish of figured optics from different vendors by atomic force microscopy and optical profilometry and have investigated how the substrate quality can be improved by the deposition of thin films. We have determined the growth parameters of several thin-film structures. From these parameters we can determine how the surface topography of a coated mirror differs from that of the substrate, select the best thin-film structure, and predict the possible improvement. Keywords: Smoothing films, multilayer coatings, finish of mirror substrates

Artifacts induced by distortions which sometimes occur in two- dimensional projection images can appear in the resulting tomographic reconstructions. We describe a procedure for analyzing, correcting and removing experimental artifacts, and hence reducing reconstruction artifacts. Two-dimensional and three-dimensional images acquired with scanning transmission x-ray microscopy of a sample containing an integrated circuit interconnect show how these procedures can be successfully applied.

The objective crystal spectrometer (OXS) on the forthcoming Spectrum-Roentgen-Gamma satellite is designed to carry three kinds of crystals: LiF(220), Si(111) and RAP(001), placed in front of the SODART telescope. Thirty six super polished (RMS roughness < 0.1nm) Si(111) substrates were coated with 65-80 periods of Co/C multilayers using electron beam evaporation deposition combined with ion polishing for the metal layers. These crystals are to be used in the energy band immediately below the C-K absorption edge of 0.284 keV. Because the crystals are to be assembled as one crystal on the OXS, the reflectivity performance as a function of energy and angle of incidence of all crystals has been measured using line radiation from an x-ray tube which provides 1.487 keV and 0.277 keV and using synchrotron radiation from 0.16 keV to 0.28 keV at the Synchrotron Ultraviolet Radiation electron storage ring a t the National Institute of Standards and Technology. The results from these measurements are discussed.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have produced two new normal incidence soft x-ray telescope mirrors coated for lambda equals 63.5 angstrom wavelength: the first with a focal length f equals 1.5 m and a diameter of 25 cm for the Space Weather and Terrestrial Hazards (SWATH) satellite and the second (f equals 2 m, diameter 27.5 cm) for launch by sounding rocket (NIXT). We describe figuring and polishing of the mirror surfaces and deposition and testing of the multilayer coatings. Optimization of the mirror fabrication included grazing incidence x-ray reflectivity for quality control during polishing. In addition, the substrate and each metal layer of the Co-C multilayer coating were polished by an ion beam with in-situ roughness estimation. We explored the possibilities and limitations of telescopes for shorter wavelengths by coating several small mirrors covering the lambda equals 45 to 60 angstrom region at normal incidence and report on their performance.

A planar diode, rf-sputtering system, modified to triode operation by addition of a ring filament surrounding the anode, is described. Alternately timed sputtering is used to fabricate multilayer films with good characteristics, predominantly in the extreme ultraviolet (EUV) range of 15 to 20 nm. Fabrication of stable films of niobium/silicon is discussed, along with characterization results that utilized x-ray diffraction (XRD) and synchrotron source reflectance measurements. Characteristics of an optic that was designed and used to photograph the sun at 18.0 nm from a rocket-borne experiment are described.

In response to the needs of a solar imaging program, we designed, fabricated, and evaluated several multilayer mirror coatings for an x-ray telescope to image the sun at 9.39 nm (Fe XVIII). The telescope optic is a single-mirror Herschelian design operating at near normal incidence. Simulations using commercially available software guided preliminary multilayer mirror design. Based upon these calculations, dual ion beam assisted deposition techniques generated trial films and multilayers. Structural evaluations were carried out on a multiaxis x- ray (0.154 nm) reflectometer with specular reflection and non-specular scattering measurements. Performance parameters for the multilayers at design wavelength were obtained from the NIST EUV reflectometer at the SURF II storage ring.

We have recently completed construction of a high throughput, modest resolution soft x-ray monochromator installed at the Synchrotron Ultraviolet Radiation Facility of the National Institute of Standards and Technology. Although this monochromator will be used primarily to characterize the optical properties of multilayer-coated x-ray optics, the versatility of the instrument will enable us to measure such properties as reflectivity, transmission, diffraction, and scatter of a variety of components. We present measurements of monochromator throughput and resolution.

The quest for ultrahigh resolution full-disk images of the sun at soft X-ray/EUV/FUV wavelengths has increased the demand for photographic films with broad spectral sensitivity, high spatial resolution, and wide dynamic range. These requirements were made more stringent by the recent development of multilayer telescopes and coronagraphs capable of operating at normal incidence at soft X-ray/EUV wavelengths. Photographic films are the only detectors now available with the information storage capacity and dynamic range such as is required for recording images of the solar disk and corona simultaneously with sub arc second spatial resolution. During the Stanford/MSFC/LLNL Rocket X-Ray Spectroheliograph and Multi-Spectral Solar Telescope Array (MSSTA) programs, we utilized photographic films to obtain high resolution full-disk images of the sun at selected soft X-ray/EUV/FUV wavelengths. In order to calibrate our instrumentation for quantitative analysis of our solar data and to select the best emulsions and processing conditions for the MSSTA reflight, we recently tested several photographic films. These studies were carried out at the NIST SURF II synchrotron and the Stanford Synchrotron Radiation Laboratory. In this paper, we provide the results of those investigations.

In response to the metrology needs of the soft X-ray community, the National Institute of Standards and Technology (N1ST) has initiated a program devoted to the characterization of multilayer coated optics in the4 -40 nm wavelength region. In this paper, we describe the synchrotron based XUV reflectometers in use and under construction at NIST. We review the characteristics of the Synchrotron Ultraviolet Radiation Facility storage ring (SURF II), discuss the capabilities of the existing reflectometry facility, and present thefinal design parameters, expected performance, and construction status of a new reflectometry beam line. 1. INTRODUCTION 4 —"'I ____________________ I ____________________ ..72T.:.. q — -z-..-. The production of highly reflecting, normal incidence, multilayer coated mirrors for use between 4 and 40 nm (the extremeultraviolet, XUV, or soft X-ray) is an enabling technology that has had a significant impact on many areas of technological and scientific interest.1 Research groups across the country continue to improve the performance of XUV multilayer mirrors