Extreme Ultraviolet Lithography (EUVL) is the favourite next generation lithography candidate for IC device manufacturing with feature sizes beyond 32nm. Different absorber layers and manufacturing concepts have been published for the fabrication of reflective EUVL masks. A mandatory step in the EUVL mask making is the patterning of sub 100nm features. The layer composition of such a TaN absorber consists of an anti reflective coating (ARC) on top of a base layer.
We investigated the dry etch behaviour of TaN based absorbers with four different top ARC layers. Our focus was to determine a dependency of patterning criteria e.g. etch selectivity, minimum resolution, CD uniformity and linearity on the different ARC layers. Before, the deposition parameters of the top ARC layers have been optimized by SCHOTT Lithotec towards minimum stress and the appropriate reflectance property at the 257nm inspection wavelength. The mask blank exposure was done on a 50kV Vistec SB350 MW variable shaped e-beam writer using a 300nm thick Fuji FEP171 resist film. Our test pattern covered a quality area of 132mm x 132mm and comprised dense/iso line structures and contacts from 60nm-1200nm. Testmasks with the four different TaN based absorbers have been dry etched on an Oerlikon mask etcher III. The dry etch recipe and parameters have been kept constant for the different absorber testmasks. Line and contact hole patterns with a minimum feature size of ~70nm and perpendicular profiles have been realized. CD uniformity on 180nm L&S and linearity measurements on dense and iso features from 100nm-1200nm havbe been carried out.
Overall, a TaN based absorber including dry etch process has been developed, able to fulfill the requirements for IC device manufacturing with feature sizes down to 22nm - suitable for EUV-Lithography.
Crystalline calcium fluoride is one of the key materials for 193nm lithography and is used for laser optics, beam
delivery system optics and stepper/scanner illumination optics. In comparison to fused silica it shows a much higher
laser durability. However, even in pure calcium fluoride the irradiation by ArF excimer laser (193nm) can cause
transmission loss and depolarization. Short time and long time tests of radiation induced changes of optical properties of
CaF2 were carried out. Within short time tests initial and radiation induced absorption as well as the measurement of
laser induced fluorescence and the measurement of laser induced depolarization are adequate methods for
characterization of the material under ArF laser irradiation. Previous investigations were done by Burnett to prevent
depolarization caused by spatial dispersion. Nevertheless an important challenge is the prevention of depolarization of
the polarized laser beam by CaF2 laser optics caused by a temperature gradient. The dependence of depolarization on
the direction of temperature gradient in comparison to the direction of the laser beam and the orientation of the CaF2
crystal was investigated. In the present work different paths to prevent or mitigate the depolarization by CaF2 due to a
temperature gradient are discussed resulting in a special chance to mitigate depolarization by a laser window.
Reflections occur at every interface of a mask and are known as flare. Flare effects have a negative impact on the resist exposure at the wafer level. In this paper total antireflection (AR) solutions are presented to eliminate flare effects at mask level. These are next generation binary and phase shifting mask blanks, where AR coatings are effective not only on top of the absorber, but also eliminate internal as well as back side reflections. Substrate reflection can be reduced both internally and externally by an order of magnitude to below 0.5%. Internal (backside) reflection of a binary chrome or a phase shifting layer are reduced from about 40% to below 0.1%. Reflection in the etched area is also addressed and reduced by an order of magnitude. A sophisticated absorber AR coating is presented, where reflection at 193 nm lithography can be reduced to zero while at the same time reflection at 257 nm inspection wavelength is tuned to the maximum sensitivity range of 7% to 20%.
Schott's already commercially available two layer Ta/SiO2 phase shift system can be tuned from 6% up to 40% transmission for 157, 193 and 248 nm lithography wavelengths. Thus one film patterning process provides a wide product range. Attenuated phase shift masks for 6%, 20% and 30% transmission at 193nm were produced. Tests for laser stability and chemical durability show excellent performance. The phase shifting film achieves a high etch selectivity to the substrate. Dry etch process development is done at IMS chips in Stuttgart, Germany, to provide our customers the service of a good start process for patterning. Results of phase and transmission uniformity are included. Our newest development enhances the layer system and provides a better contrast for inspection in reflection mode. Transmission of our standard two layer Ta/SiO2 PSM system is below the required 20% at inspection wavelengths. The reflectivity of 30% to 40% can be lowered by insertion of an additional contrast layer. The thickness of this contrast layer is adjusted to achieve the required reflection at inspection wavelengths, while the other film thicknesses are tuned to preserve the desired transmission and 180° phase shift at the design wavelength. As first examples 6% and 20% transmission PSM for 193 nm were tested. Reflection at 257 nm and 365 nm inspection wavelengths can be lowered from initial 30% to 40% down to about 10%.
Mask Blanks for EUV Lithography require a lot of new properties and features compared to standard Chrome-on-Glass blanks. Starting from completely new low thermal expansion substrate materials with significantly improved surface quality over multilayer coatings for EUV reflection, buffer layers, up to new absorber layers with improved dry etching and inspection properties. In addition highly sophisticated metrology is needed for further improvements and process control. New polishing and cleaning technologies, improved sputter technology and updated metrology enable us to routinely produce EUVL mask blanks meeting already many of the ITRS roadmap requirements. Our improvements on low defect EUV multilayer coatings as well as on our metrology methods will be elucidated and some aspects of this will be explained in detail. In addition a new design of EUVL absorber material with experimental results will be reported, including optical performance at inspection wavelength.
Mask Blanks for EUV Lithography require a lot of new properties and features compared to standard Chrome-on-Glass mask blanks. SCHOTT Lithotec has introduced all relevant technology steps to manufacture EUV mask blanks. Starting from completely new low thermal expansion substrate materials with significantly improved surface quality over multilayer coatings for EUV reflection up to new absorber layers with improved dry etching and inspection properties. New polishing and cleaning technologies, improved sputter technology and updated metrology enable us to routinely produce EUVL mask blanks meeting already many of the ITRS roadmap requirements. Further R&D is ongoing to path the way to the production of EUV mask blanks which meet all requirements
An important focus of this report is to present recent results on EUVL multilayer properties such as defect density, optical properties like reflectivity and uniformity in the EUV range. In addition a new design of EUVL absorber material will be reported, including optical performance at inspection wavelength, dry etch performance and resistance to cleaning steps. Finally improvements on our metrology methods for EUVL components, such as high throughput EUV-reflectometry will be elucidated.
Photolithography is a key technolgoy for the production of semiconductor devices. It supports the continuing trend towards higher integration density of microelectronic devices.
The material used in the optics of lithography tools has to be of extremely high quality to ensure the high demand of the imaging. Due to its properties CaF2 is a material of choice for the application in lithography systems.
Because of the compexity of the lithography tools single lenses or lens system modules cannot be replaced. Therefore the lens material has to last the full lifetime of the tool without major degradation.
According to the roadmap for next generation of optical lithography tools, like immersion lithography, the requirements of CaF2 for radiation hardness are increasing considerably.
We will present a detailed analysis of the key factors influencing the laser hardness covering the complete production chain.
Some aspects of the evaluation methods for testing CaF2 laser durability will be presented.
EUV Lithography requires high end quality defect free layers from the backside coating to the absorber stack. Low thermal expansion materials (LTEM) substrates with super flat surfaces are already available with low defect backside coating for E-Chuck technology. The multilayer stack is well developed from a physical point of view and major effort relies nowadays on the layer defectivity. On the other hand, absorber stack becomes one of the main challenges in terms of stress, optical behavior for ultraviolet wavelengths and dry etching behavior. Schott Lithotec is currently developing absorber stack solutions that will fulfill the requirements of next generation lithographies. There are several options for achieving the mechanical, optical and chemical specs for buffer layers and absorber coatings. Some of them are already integrated in our production processes. Buffer layers were evaluated and reach almost the physical and chemical level necessary to fit with the mask processing. TaN based absorber coatings were designed and deposited by an ion beam sputter tool optimized for low defect deposition (LDD-IBS). The chemical composition of our layer and its manufacturing process is already optimized to achieve high quality etching behavior. The current results of defect density for the absorber stack will be presented.
Schott's already commercially available two layer Ta/SiO2 phase shift system can be tuned from 6% up to 30% transmission for 157, 193 and 248 nm lithography wavelengths. Thus one film patterning process provides a wide product range. Dry etch process development is done at IMS chips in Stuttgart, Germany, to provide our customers the service of a good start process for patterning. Our newest development enhances our phase shift layer system. An inspection layer provides an improved contrast for inspection at 257 nm and 365 nm by adjusting reflection to the optimum range from 7% to 20%. Chemical durability against standard mask cleanings was already shown to be good but can be further enhanced by an protection layer. Furthermore a new two layer phase shift system was designed achieving ultra-high transmission above 90% at 193 nm lithography wavelength as an alternative to hard shifter masks.
The orientation and center-of-mass contributions of water to light scattering are calculated based on the known anisotropy of the polarizability of the water molecule. Further, the polarization ratio under 90-deg scattering is calculated and the relation between orientational and center-off-mass contributions for different polarization directions is evaluated. An experiment is proposed that enables us to separate the different scattering contributions. While the amount of scattering due to molecular orientations seems to be still moderate for water, it is expected to be larger for most fluids, like fluorinated polymers.
A new phase shifting film system based on tantalum and silicon dioxide is presented. The tantalum film works as a transmission control layer and furthermore as an etch stop layer due to its good etch selectivity. The silicon dioxide phase control layer is tuned to 180° phase shift. Excellent laser stability and chemical durability were already shown. The two layer system can be easily tuned to various transmission values for three different lithography wavelengths. Transmission and phase shift uniformity fulfill already the final production specifications according to ITRS. An optimized deposition process yields excellent film surface roughness values equal to an uncoated substrate. Defect density could be significantly reduced recently. First SEM pictures of structured films show promising results.
Lutz Aschke, Hans Becker, Falk Friemel, Thomas Leutbecher, Nathalie Olschewski, Markus Renno, Frauke Rueggeberg, Mario Schiffler, Frank Schmidt, Frank Sobel, Kurt Walter, Guenter Hess, Frank Lenzen, Konrad Knapp, Jochen Alkemper, Hrabanus Hack, Klaus Megges, Ina Mitra, Rolf Mueller, Uwe Nolte, Joerg Schumacher, Wolfgang Pannhorst
Mask Blanks for EUV Lithography require a lot of new properties and features compared to standard COG blanks. Starting from completely new low thermal expansion substrate materials with significantly improved surface quality over multilayer coatings for EUV reflection, buffer layers, up to new absorber layers with improved dry etching and inspection properties. This paper introduces in the special features of Low Thermal Expansion Materials (LTEM), their manufacturing and the special metrology for the Coefficient of Thermal Expansion (CTE). We will look into some details of polishing methods for much better flatness of the substrates. The process and the metrology of low defect EUV multilayer coatings will be elucidated and some aspects of this will be explained in detail. In addition we will present new results from no-chrome alternative absorber materials.
Homogeneity residuals of the refractive index have a strong influence on the performance of lithography tools for both 193 and 157 nm application wavelengths. By systematic investigations of various defects in the real structure of CaF2 crystals, the origin of homogeneity residuals can be shown. Based on a quantitative analysis we define limiting values for the individual defects which can be either tolerated or controlled by optimized process steps, e.g. annealing. These correlations were carried out for all three relevant main crystal lattice orientations of CaF2 blanks. In conclusion we achieved a strong improvement of the critical parameters of both refractive index homogeneity and striae for large size lens blanks up to 270mm diameter.
When investigating fluids for liquid immersion lithography scattering
of light is more crucial than absorption. The reason is that pure absorption can be compensated by an increase of exposure time or light intensity, while scattered light decreases the imaging contrast on the photoresist. We therefore carefully investigate the scattering of light in a molecular liquid. Light can be scattered due to a number of mechanism. These are inelastic mechanism like Raman scattering, elastic scattering on micro- and nano bubbles but also quasielastic scattering on density fluctuations. In addition to the quasielastic scattering on density fluctuations a molecular fluid shows scattering on orientation degrees of freedom. Based on the known anisotropy of the polarizability of the water molecule, we calculate the scattering components due to orientation fluctuations. Among these the polarization ratio under 90° scattering is calculated and the relation between orientation and center-off-mass contributions for different polarization directions is evaluated.
While the amount of scattering due to molecular orientations seems to
be still moderate for water it is expected to be larger for most
fluids, like fluorinated polymers.
For three different fluor--organic molecules, which are in discussion for
immersion fluids, the molecular polarizability is calculated using an
abinitio method. The resulting polarizabilities are used to estimate
the scattering due to orientation motion of these molecules. As a
result the scattering due to orientation motions has the potential to
increase the scattering level remarkably.
KEYWORDS: Ions, Crystals, Absorption, Deep ultraviolet, Distortion, Electron holes, Optical properties, Chemical species, Glasses, Temperature metrology
Lens fabrication for the short wavelengths of the DUV spectral range
requires the replacement of glasses, by the crystalline material CaF2. We review mechanism for the interaction of CaF2 with electromagnetic radiation, especially at wavelengths of 193 nm and 157 nm. In the ideal material an absorption process can occur only via a two photon process where charges are separated and an electron--hole pair is created in the material. These excited charges can localize as charge centers or as as localized excitonic state, a bound F--H+-pair. At room temperature all charge centers should recombine within a few pico seconds and no long time change of the optical material properties should be observable. In the real material not only charge center formation but also the stabilization of these charge centers at room temperature due to impurities is identified as a key for the understanding of a radiation induced change of optical material properties.
EUV substrate materials have to meet enhanced requirements with respect to extreme low thermal expansion, high homogeneity and superior surface quality. A SCHOTT R&D program aims at the development of advanced materials covering these various aspects. The glass-ceramic Zerodur (registered trademark) of SCHOTT represents a substrate material currently used for EUV masks and optics of first generation tools due to its extremely low coefficient of thermal expansion (CTE) and its excellent homogeneity. Zerodur(registered trademark) even allows continuous shifting of the position of zero crossing of the CTE-slope to control the thermal expansion behavior according to varying customer requirements: As a result of specifically adjusted process parameters, samples of Zerodur (registered trademark) exhibit a coefficient of thermal expansion CTE < 5 ppb/K corresponding to the lowest expansion class of the SEMI standard P37 (19 to 25°C) for EUV mask blanks. By further variation of process parameters, the position of zero crossing, e.g. at 22.5°C or 30°C, can be varied, revealing an attractive attribute feature of Zerodur (registered trademark).
A new dilatometer type reveals an improved reproducibility of ~ 1ppb/K in the temperature range of 0 to 50°C. A series of CTE(0;50°C) measurements with a test-cube of Zerodur (registered trademark) provides information on CTE homogeneity on a cm-scale: no CTE variation was observed within the error of measurements (1ppb/K) for a block exhibiting ± 3.5*10-6 variation in refractive index. CTE variation can cause surface deformations during changing temperature conditions. A Fizeau-Interferometer was used to record surface roughness at two different temperatures. This non- destructive metrology is regarded as a method to distinguish CTE variation < 1ppb/K. The surface deformation of Zerodur (registered trademark) due to elevated temperature was determined to be lower than the resolution. Both methods to analyze the CTE homogeneity of Zerodur (registered trademark) lead to the result of CTE variation below 1 ppb/K.
Surface treatment of glass-ceramic material is a major challenge as final finishing of EUV substrates may increase roughness of super-polished surfaces significantly. Improved new glass-ceramic materials demonstrate optimization of glass-ceramic compositions to nearly meeting the specification of surface roughness after a standard finishing process.
Recent achievements of material development reveal CTE-performance of this new glass-ceramic to also be adjustable to varying customer needs as already known for Zerodur (registered trademark).
These results are regarded as a promising milestone to develop an optimized glass-ceramic material, because the features of the modified New-Glass Ceramic now better match the key requirements of EUVL substrate materials.
Schott Lithotec has introduced all relevant technology steps to manufacture EUV mask blanks - ranging from Low Thermal Expansion Material (LTEM) via high quality substrate polishing to low defect blank manufacturing. New polishing and cleaning technologies, improved sputter technology and updated metrology enable us to routinely produce EUVL mask blanks meeting already many of the roadmap requirements. The goal is pilot production of EUV blanks for the 45 nm node end of 2005.
There are several technology options for achieving the mechanical, optical and chemical specs for substrates and coatings. Some of them are already integrated in our processes. An important focus of this paper is the understanding of defect sources starting from the LTEM bulk material to the fully coated blanks with multilayer, buffer and absorber. We present details on some production steps controlling defect detection sensitivity dedicated to various layers and report on new results on defect reduction research after the different process steps.
A new attenuated phase shifting film system for 157 nm lithography is presented. The system is designed for 6% transmission but is tunable to higher values. Tests for laser stability and chemical durability show excellent performance. First results of defect density and phase and transmission homogeneity are presented. The phase shifting film achieves a high etch selectivity to the substrate. The film system is extensible to be used as a high transmission phase shifter for 193 nm lithography. Further it is feasible to repair the film system using electron beam repair technology.
Schott Lithotec has introduced all relevant technology steps to manufacture EUV mask blanks in its advanced quality mask blank manufacturing line -- ranging from Low Thermal Expansion Material (LTEM) high quality substrate polishing to low defect blank manufacturing. New polishing and cleaning technologies, improved sputter technology and updated metrology enable us to produce EUVL mask blanks meeting already some of the roadmap requirements. Further R&D is ongoing to path the way to the pilot production of EUV blanks which meet the beta-specifications end of 2005.
We present the status of our EUVL substrate program and report on the recent results of our activities for low defect multilayer, buffer and absorber coating including new absorber materials. Recent results from the production of full LTEM EUV blanks with multilayer, buffer and absorber coatings will be presented. Process steps in the EUVL mask blank fabrication in a production environment were characterized in terms of defects; the process improvement potential is discussed. We will also throw a light on the aspects of changed layer properties after a longer period of storage. In addition, special metrology methods for EUVL components are currently being developed within the program. The status of the high throughput EUV-Reflectometer for mask blanks will be presented. We developed new processes to achieve EUVL requirements.
F2 lens designs considering Intrinsic birefringence imposed more severe challenges to CaF2 manufacturing technology. In order to compensate the intrinsic birefringence other crystal orientations (100) / (110) are necessary. These other crystal orientation beside (111) require individual process optimization. In this paper the achieved improvements for CaF2 lens blank material will be presented. Furthermore the conversion of stress birefringence results from 633nm to 193nm or 157nm is unclear until now. At wavelength birefringence measurement results of different orientated lens blanks will be shown and discussed.
The enhanced demands for substrate materials for next-generation optics and masks have initiated detailed investigations on Zerodur as a proposed EUVL substrate material with focus on thermal expansion behavior and surface roughness. As a result of specifically adjusted process parameters, the coefficient of thermal expansion (CTE) was tailored to be a minimum at 22.5°C. Laboratory samples of Zerodur exhibit a CTE < 5 ppb/K corresponding to the lowest expasnion class of the SEMI standard P37 (19 to 25°C) for EUV mask blanks. By further variation of process parameters, the position of zero crossing, e.g. at 30°C, can be varied, revealing an attractive attribute feature of Zerodur. A new dilatometer type was mounted in 2002 with first operatinoal results revealing an improved reproducibility of ~1ppb/K in the temperature range of 0 to 50°C. A series of CTE measurements with a small block of Zerodur provides information on CTE homogeneity on a cm-scale: No CTE variation was observed within the error of measurements for a block exhibiting ± 3.5*10-6 vairtion in refractinve index. CTE variation can cause surface deformations during changing temperature conditions. A first setup of Fizeau-Interferometer with a current resolution of 0.3 nm rms was used to record surface deformation of Zerodur due to elevated temperature was determined to be lower than the current resolution. Both methods to analyze the CTE homogeneity of Zerodur lead to the result of CTE variation below 1 ppb/K, still identifying today's need to improve metrology further. Final finishing of EUV substrates may increase roughness of super-polished surfaces significantly. Using appropriate processes a to surface roughness < 0.25 nm rms under production conditions can be achieved after final finishing of Zerodur. As an improved Zerodur-type material, recent achievements of material development demonstrate the optimization of glass-ceramic composition to nearly meeting the specification of surface roughness after a standard finishing process. These results are regarded as a promising milestone to develop an optimized glass-ceramic material providnig adjusted thermal expansion behavior and surface processability according to the specific demands of EUV technology.
EUV mask blanks consist of two thin film systems deposited on low thermal expansion 6 inch substrates (LTEM). First there is the multilayer stack with around 100 alternating layers of elements with different optical properties which are topped by a capping layer. The absorber stack which consists of a buffer and a absorber layer is next. Here a minimum absorption of EUV light of 99 % is required. The stress in both layer systems should be as low as possible. The reduction of defects to an absolute minimum is one of the main challenges. The high-reflective Mo/Si multilayer coatings were designed for normal incidence reflectivity and successfully deposited on 6-inch LTEM substrates by ion-beam sputtering. X-ray scattering, transmission electron microscopy and atomic force microscopy were used for characterization of the multilayer interfaces and the surface morphology. The results are correlated to the measured normal incidence reflectivity using synchrotron radiation at the "Physikalisch- Technischen Bundesanstalt" (PTB) refelctometer at BESSY II, Berlin, Germany. A high resolution laser scanner was used to measure the particle distribution. First multilayer defect results are presented.
Schott Lithotec is producing and developing the optical materials for the 248-nm, 193-nm and 157-nm lithography technology. 248-nm systems are in use already, the first 193-nm prototype system has been set up and the first 157-nm stepper system is expected to run in 2003. Schott Lithotec provides the Fused Silica and CaF2 materials for these systems both in production and in development. In order to ensure the requirements on transmission and laser durability as well as on homogeneity and birefringence numerous metrology R&D activities have been performed. The requirements on the optical material quality concerning these materials are extremely high and continuously increasing. We present the status of R&D activities for the metrology, which is necessary to demonstrate the improvement of the optical material quality. Based on the forecasts of the semiconductor industry (ITRS, SIA and DATAQUEST Roadmaps), we will derive the needs for metrology in the future.
The 157 nm lithography technology is supposed to become the system setup for the 100 nm respectively the 70 nm node. The first 157 nm Full-Field Scanner system is expected in 2002. Every currently evaluated optical design of such lithography systems makes a very intensive use of Calcium Fluoride as one of the few optical materials having the required transmittance at the F2 laser wavelength solely. Additionally the required further industrial production processes e.g. polishing and development of coatings are known from the 193 nm lithography where CaF2 is already in use. In this paper we report about R&D activities of the material development used for the high quality CaF2. Thus the main aspects on quality are discussed in detail.
For EUV lithography mask blank substrates of the 6025 type will be made from Near Zero Thermal Expansion (NZTE) materials. The low thermal expansion of EUV substrates shall provide for the required better thermal stability during mask-writing and lithography exposure. The manufacturing of such NZTE mask blank substrates requires modified finishing processes in comparison to standard mask blanks. Super polishing takes place to provide high spatial frequency roughness of less than 2 Angstroms RMS. To improve the flatness and the roughness at the mid spatial frequencies another correction step is required. Such step can be Ion Beam Figuring for example. We evaluate the results for the different spatial frequencies by interferometry and atomic force microscopy. We have a closer look how the additional finishing steps improve the flatness and mid spatial frequency roughness. The impact of these newly introduced finishing steps for the high spatial frequency roughness is studied. We examine the processes for two different substrate materials with near zero thermal expansion (ZERODUR and ULE).
In order to increase the quality in manufacturing of future photon mask generations Schott Lithotec is brought in a brand new, much increased automatic laser inspection system into a new manufacturing line of photo mask blanks. It is in a position to detect additionally to the standard defect types further defect types like dim- and bright-chrome defects. The resolution of the system is less than 100 nm. With a quickly inspecting time per blank of less than three minutes and for the first time in the world used automatic SMIF-pod-handling this is a tool for the 100 percent final inspection in the manufacturing of photo mask blanks.
The 157 nm lithography technology is supposed to become the system setup for the 100 nm respectively the 70 nm node. The first 157 nm Full-Field Scanner system is expected in 2002. Every currently evaluated optical design of such lithography systems makes a very intensive use of Calcium Fluoride as one of the few optical materials having the required transmittance at the F2 laser wavelength solely. Additionally the required further industrial production processes e.g. polishing and development of coatings are known from the 193 nm lithography where CaF2 is already in use. In this paper we report about R and D activities of the material development used for the high quality CaF2. Thus the main aspects on quality are discussed in detail.
SCHOTT ML (MicroLithography) is presented as the world's first supplier of optical materials for all current generations of wafer steppers: i-line-glasses for 365 nm, fused silica for 248 nm/193 nm and CaF2 for 193-nm microlithography. I-line-glasses are presented optimized in transmission, solarization and refractive index homogeneity for application in high performance i-line-scanner systems for such 0.25 micrometers mix and match technology. The focus for fused silica is laid on laser damage performance, essential for application in 193 nm lithography. An experimental setup is shown, allowing a fast evaluation of materials respecting laser induced fluorescence and absorption. First data of a 193 nm marathon test on SCHOTT ML fused silica are presented. Use of CaF2 in ArF projection optics requires improvement of crystal growth processes and equipment. The progress achieved in refractive index homogeneity, stress birefringence and transmission is presented. High laser damage resistance for ArF illumination optics was also accomplished. Common requirement for mass production of all high grade optical materials is the ability for accurate material characterization. Status of measurement and characterization equipment is presented for selected optical properties.
The Advanced X-ray Astrophysics Facility (AXAF) will be a space-based observatory consisting of special mirrors to form images in x rays. The mirrors are composed by nested conical shaped thin walled ZERODUR cylinders. ZERODUR is the ideal material for grazing incidence optics. The production steps of these ZERODUR blanks are briefly described. Different QA techniques, detection of tiny inclusions in the glass ceramic via infrared light, precise dilatometer measurements of the coefficient of thermal expansion and specific optical metrology, had to be applied. Results of the metrology are discussed.
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