In our ongoing studies of high precision glass slumping we have successfully formed the first Wolter-I X-ray mirror
segments with parabola and hyperbola in one piece. It could be demonstrated that the excellent surface roughness of the
0.55 mm thick display glass chosen is conserved during the slumping process. The influence of several parameters of the
process, such as maximum temperature, heating and cooling rates etc. have to be measured and controlled with adequate
metrology. Currently, we are optimizing the process to reduce the figure errors down to 1 micrometer what will be the
starting point for further, final figure error corrections. We point out that metrology plays an important role in achieving a
high precision optics, i.e. an angular resolution of a few arcsec. In this paper we report on the results of our studies and
discuss them in the context of the requirements for future X-ray telescopes with large apertures.
Future X-ray missions are aiming at large mirror collecting areas of the order of several square meters. This is obtained with mirror assemblies composed of a large number of segments. The angular resolution of each one must be measured separately down to 1 arcsec. The mass limits imposed by the launchers require low weight and high stiffness materials. In this context we have focused our recent studies on the manufacturing of thin glass mirror segments. These mirrors are made from sheet glass which can be shaped in a high-precision slumping process to e.g. a Wolter-I figure. The excellent surface roughness of the sheet glass chosen is conserved during the slumping process and the final figure corrections with non-contacting tools. The influence of several parameters of the process, such as glass and mould material, heating and cooling, has been measured and controlled with adequate metrology. In this paper we describe our current efforts which are aiming at the production of a Wolter-I scaled demonstration model - preferentially with parabola and hyperbola in one piece - made of thin sheet glass.
EUVL (extreme ultraviolet lithography), utilizing an actinic wavelength of about 13 nm , appears to be the most promising technology approach to reach the 30 nm node. Calling for diffraction limited imaging performance, EUV demand unprecedented requirements for figure metrology and fabrication technology. This paper gives an overview over problems rising from the interferometric measurement of aspheric EUV mirrors.
Dark Energy dominates the mass-energy content of the universe (about 73%) but we do not understand it. Most of the remainder of the Universe consists of Dark Matter (23%), made of an unknown particle. The problem of the origin of Dark Energy has become the biggest problem in astrophysics and one of the biggest problems in all of science. The major extant X-ray observatories, the Chandra X-ray Observatory and XMM-Newton, do not have the ability to perform large-area surveys of the sky. But Dark Energy is smoothly distributed throughout the universe and the whole universe is needed to study it. There are two basic methods to explore the properties of Dark Energy, viz. geometrical tests (supernovae) and studies of the way in which Dark Energy has influenced the large scale structure of the universe and its evolution. DUO will use the latter method, employing the copious X-ray emission from clusters of galaxies. Clusters of galaxies offer an ideal probe of cosmology because they are the best tracers of Dark Matter and their distribution on very large scales is dominated by the Dark Energy. In order to take the next step in understanding Dark Energy, viz. the measurement of the 'equation of state' parameter 'w', an X-ray telescope following the design of ABRIXAS will be accommodated into a Small Explorer mission in lowearth orbit. The telescope will perform a scan of 6,000 sq. degs. in the area of sky covered by the Sloan Digital Sky Survey (North), together with a deeper, smaller survey in the Southern hemisphere. DUO will detect 10.000 clusters of galaxies, measure the number density of clusters as a function of cosmic time, and the power spectrum of density fluctuations out to a redshift exceeding one. When combined with the spectrum of density fluctuations in the Cosmic Microwave Background from a redshift of 1100, this will provide a powerful lever arm for the crucial measurement of cosmological parameters.
This work discusses the imaging properties of EUVL systems on the basis of an aerial image study in resist. A process window analysis for the lithographic structures which are driving the ITRS roadmap is presented. Here we cover the 45 nm and 32 nm node. In a first step we focus on the contribution of wavefront aberrations and flare effects to the imaging performance. In a second step we investigate the process latitude for different generic pattern of the above mentioned nodes. It becomes clear that EUVL tools are a very good choice for the printing of contact holes. Dense and semi-dense lines can be easily printed too, using a conventional illumination setting. From our current perspective, isolated features on bright field reticles are the most challenging structures for EUV imaging due to the flare impact on contrast and process latitude. Related to flare we discuss our progress in mirror surface manufacturing to reduce the overall flare level.
EUVL, i.e. microlithography at 13nm is one of the most likely technologies to satisfy the requirements for the 45nm-node and below of the IC-manufacturing roadmap. The development of the first step and scan machines meeting production requirements of field size and resolution is in progress. A key component of these machines will be a
diffraction limited, off-axis mirror system with aspherical surfaces. The optical surfaces of these mirrors have to be fabricated and measured with unprecedented accuracy. In recent years, technology development at Carl Zeiss SMT AG was focussed on the on-axis aspheres of the NA=0.30 micro exposure tool (MET). Presently this technology is
transferred to the surfaces of a NA=0.25 off-axis, large field system The current status of the fabrication and metrology of both on-axis and off-axis mirrors will be reviewed.
After the successful completion of the European program EUCLIDES in which core competence for Extreme UltraViolet Lithography (EUVL) technology was generated, ASML (system integration), Carl Zeiss (optics), and their partners have entered the next phase of the program: design and realization of an exposure tool called the alpha tool ((alpha) -tool). This tool should be completed in 2003, and will demonstrate 50-nm-node compliant imaging using full- field all-reflective four-times reducing optics, as well as high performance vacuum scanning wafer- and reticle stages. IN this paper we present the status of the project, as well as highlight the progress in the optics development and optics contamination mitigation efforts.
The Extreme UV Concept Lithography Development System (EUCLIDES) program headed by ASM Lithography (ASML), partnered with Carl Zeiss and Oxford Instruments is evaluating EUV lithography for its viability at resolutions of 70 nm and below. From August 1998 through February 2000 the first phase was done. In this phase, the core technologies necessary to demonstrate the technical solutions for the list of possible EUV lithography 'showstoppers' have been developed. This includes: (1) Mirror substrates, (2) High reflectivity multi- layer coatings, (3) Resist outgassing reduction schemes, (4) Vacuum stages. A synchrotron source design was developed to compare synchrotron sources with plasma sources. The consortium also investigated the total system architecture to make sure the system concept meets the requirements of the semiconductor industry at an acceptable cost of ownership. In this paper, an overview of the program objectives is given, followed by an overview of highlights obtained by the various program partners and subcontractors throughout the first phase. Finally, the European partner's plan for the next phase is shown (working in close collaboration with other international consortia). This next phase will eventually lead to EUVL production tools.
The Coronal Diagnostic Spectrometer (CDS) is one of the key instruments of the ESA cornerstone mission SOHO, scheduled for launch in 1995. It is designed to study the solar corona in the EUV. After successful completion of an engineering model in 1991 the flight model fabrication was started end of 1992. In August 1993 the optical alignment of the CDS flight mirror (FM) module was completed. The paper reports about the fabrication and achieved quality of the primary and secondary mirrors as well as the alignment of the mirror system. The predicted optical quality (half energy width) of the whole telescope is HEW <EQ 3 arcsecs for spatial wavelength >= 10 mm and <EQ 6 arcsec for (lambda) >= 3 mm (2).
Proven bulk materials for mirrors with high surface qualities are classical optical glass, quartz, and low thermal expansion materials like ZERODURR. New requirements for mirrors with high heat load capabilities have established the need for different bulk materials. Metals, silicon and silicon carbide (SiC) are presently the favorite materials for the manufacturing of optical components for high brilliance synchrotron beam lines. This paper discusses properties of different types of material under manufacturing and applicational aspects.
Attention is given to the Coronal Diagnostic Spectrometer (CDS), one of the key instruments on the ESA-cornerstone mission SOHO, scheduled for launch in 1995. It is designed to study the solar corona in the EUV. The on-axis resolution of the system is specified to 2 arcsec half-energy-width, which sets very stringent limits on the figuring and alignment tolerances. From the mechanical measurements and the optical tests a system HEW of 3.3 arcsec at EUV wavelengths is predicted. The HEW at 633 nm, including diffraction, is 2.2 arcsec. A performance comparable to ROSAT was achieved on the CDS mirrors which, due to the much higher asphericity, are at least 20 times more difficult to manufacture. Assembly techniques have been developed which allowed the high accurate alignment of the type II telescope, which is much more sensitive to misalignments than type I telescopes of comparable focal length and required correcting mirror displacements of as little as 20 nm while ensuring sufficient stiffness during glueing.