High volume manufacturing (HVM) of EUV-masks requires increase in accuracy, precision and practicability. HVM
requirements for reflectometry of EUV-masks are expected to be < 0.05 % in peak reflectance, and < 0.002 nm in
centroid wavelength (3 σ). Absolute accuracies should be of the same value at 1 σ. This should be accomplished along
with the reduced measuring spot size of down to < 0.01 mm2 as well as monitored alignment and positioning using
fiducial mark. With the existing EUV-reflectometer developed for mask blank characterization, 0.1 % in peak reflectivity
precision and 0.005 nm for centroid wavelength (1 σ) are routinely achieved on both reflective multilayer coated and
absorber coated blanks. It has been demonstrated that our EUV-lamp enables EUV-MBR operation without wear or
components change for > 300 million pulses, which is > 100.000 full spectra measured at different sites or > 10.000
samples measured at 9 spots each. In this work we are presenting our present status as well as the first steps to achieve
the demanded target for HVM of EUV masks. We will analyze the factors and parameters which are critical to achieve
this level quality.
The development of a novel compact EUV spectrophotometer will be presented. The device is capable of measuring reflectance and transmittance spectra of medium scale EUV-optics primary in the spectral range from 12nm to 21nm. Based on a new polychromatic measurement principle, the system uses the direct irradiation of a table-top EUV-source for illuminating the sample and a broad-band spectrograph for detecting the probe and reference beam.
Samples can be investigated under different angles of incidence and in respect of lateral dependencies.
Typical results of reflectivity investigations of Mo/Si-mirrors and transmitting foils will be shown and compared with reference measurements of certified institutes and calculations.
Extreme ultraviolet lithography (EUVL) is the leading technology for patterning at the 32 nm technology node and be-yond. EUVL light at 13.5 nm is used to print circuits. This light is produced by heating fuel (Xe, Sn) in EUV sources to a very high temperature by using either magnetic compression or laser irradiation. Today EUV source power remains the number one concern for implementation of EUVL in high volume manufacturing. Over the last few years, much pro-gress has been made in EUV source performance and availability. Today, alpha level high power (~10 W) EUV sources have been integrated in alpha level EUVL scanners. Medium and low power EUV sources are used for in-house metrol-ogy and performance studies on EUV mask blanks, EUV masks, photoresists, and optical elements. These compact dis-charge sources with medium power in the range of 10-100 mW/sr/2% bandwidth and low power EUV tubes are being used by various R&D labs for development of mask, optics, and resists. Previously, development of EUVL was mostly located at beamlines; today, these low power EUV sources are instrumental in allowing in-house R&D projects. In this paper, the latest status of high power EUV sources, low and medium power metrology sources, and some of their appli-cations are described.
For the development of pioneering optical components for beam collimation and shaping, test set-ups are indispensable for characterizing the reflectance and transmittance over the relevant spectral range. Since radiation sources with a sufficiently high brilliance were only available at synchrotron devices up to now, the characterization of the spectral characteristics was concentrated at large-scale research institutions. In contrast to that, a strong need can be noticed for innovative small and medium companies to use compact and flexible in-house spectrophotometers accelerating product development. In the framework of the present collaboration, a novel table-top spectrophotometer for measuring the spectral characteristics of medium scale EUV-optics (up to 50mm diameter) in the spectral range from 11 to 20nm was developed. The device is based on a new polychromatic measurement principle using the direct irradiation of a compact EUV-tube for illuminating the sample and a broad-band spectrometer for detecting the probe and reference beam. The samples can be investigated under different angles of incidence and in respect to lateral dependencies. In the present paper, first results with different reflecting and transmitting EUV-optical elements demonstrate flexibility, and the achieved spectral resolution and accuracy is presented.
In EUV lithography, extreme ultraviolet radiation of 13.5 nm wavelength is used to print feature with resolutions consis-tent with the requirements of the 45 nm technology node or below. EUV is produced by heating xenon, tin, or other ele-ments to a plasma state, using either magnetic compression or laser irradiation. The key concerns-identified at the third EUV-Symposium-are the ability to supply defect-free masks and to increase source component lifetimes to meet the wafer throughput requirements for high volume manufacturing. Source availability and performance, however, made steady progress within the last years on two lines of actions: High power sources for high volume production and medium and low power sources for allowing in-house metrology and performance studies on EUV-mask-blanks, EUV-Masks, photoresists and optical elements.
For "volume production sources" 50 W of collected EUV powers are already available by various suppliers. Compact discharge sources of medium power in the range of 10-100 mW / sr / 2% bandwidth and low power EUV-tubes of low-est cost of ownership and superior stability are ideal for peripheral metrology on components for EUV-Lithography. These low power sources supplement beamlines at storage rings by transferring EUV-applications to individual R&D labs. Proceeding integration of those EUV sources into tools for technology development like open frame and micro-exposers, and in tools for actinic metrology is the best proof of the progress. As of today, the first EUV sources and measurement equipment are available to be used for EUV system, mask, optics and component as well as lithography process development. With the commercial availability of EUV-plasma sources other applications using short wave-length, XUV-radiation will be feasible in a laboratory environment. Some examples of XUV applications are discussed.
AIXUV GmbH and partners have developed a high speed Reflectometer for EUV mask-blanks which is fully compliant with the SEMI-standard P38 for EUV-mask-blank metrology. The system has been installed in June 2004 at SCHOTT Lithotec AG. It features high throughput, high lateral and spectral resolution, high reproducibility and low absolute uncertainty. Using AIXUV's EUV-LAMP and debris mitigation, low cost-of-ownership and high availability is expected. The spectral reflectance of up to 3 mask-blanks per hour can be measured with at least 20 spots each. The system is push button-controlled. Results are stored in CSV file format. For a spot size of 0.1x1 mm2, 2000 spectral channels of 1.6 pm bandwidth are recorded from 11.6 nm to 14.8 nm. The reflectance measurement is based on the comparison of the sample under test to two reference mirrors calibrated at the PTB radiometry laboratory at BESSY II. The three reflection spectra are recorded simultaneously. For each spot more than 107 photons are accumulated in about 20 s, providing statistical reproducibility below 0.2% RMS. The total uncertainty is below 0.5% absolute. Wavelength calibration better than 1 pm RMS over the whole spectral range is achieved by reference to NIST published wavelengths of about 100 xenon emission lines. It is consistent with the wavelength of the krypton 3d-5p absorption resonance at 13.5947 nm to better than 2 pm.
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.
AIXUV GmbH and partners have developed a high speed Reflectometer for EUV mask-blanks which is fully compliant with the SEMI-standard P38 for EUV-mask-blank metrology. The system has been installed in June 2004 at SCHOTT Lithotec AG. It features high throughput, high lateral and spectral resolution, high reproduci-bility and low absolute uncertainty.
Using AIXUV's EUV-LAMP and debris mitigation, low cost-of-ownership and high availability is expected. The spectral reflectance of up to 3 mask-blanks per hour can be measured with at least 20 spots each. The system is push button-controlled. Results are stored in CSV file format. For a spot size of 0.1×1 mm2, 2000 spectral chan-nels of 1.6 pm bandwidth are recorded from 11.6 nm to 14.8 nm. The reflectance measurement is based on the comparison of the sample under test to two reference mirrors calibrated at the PTB radiometry laboratory at BESSY II. The three reflection spectra are recorded simultaneously. For each spot more than 107 photons are ac-cumulated in about 20 s, providing statistical reproducibility below 0.2 % RMS. The total uncertainty is below 0.5 % absolute. Wavelength calibration better than 1 pm RMS over the whole spectral range is achieved by refe-rence to NIST published wavelengths of about 100 xenon emission lines. It is consistent with the wavelength of the krypton 3d-5p absorption resonance at 13.5947 nm to better than 2 pm.
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.
A prototype of a reflectometer for masks and mask blanks has been set-up in autumn 2003 for in-house quality check of EUV mask blanks at Schott Lithotec. The target specifications are those under discussion as SEMI standard for EUV mask blank reflectometry. Additionally, the identified demands for semiconductor capital investment for future actinic EUV metrology, high throughputs and small measuring spots, were taken into account for the tool development. Effective use of the emission from a laboratory discharge source is achieved by using polychromatic reflectometry, which has been shown to deliver results about a factor of 100 faster with the same source power and needs less mechanical overhead than a monochromatic reflectometer. The hardware concept, first results and discussion of a test of the performance with respect to resolution, uncertainty and reproducibility will be represented. Jointly with the Physikalisch-Technische Bundesanstalt’s laboratory for radiometry at BESSY II the traceability to storage ring metrology, the calibration and the validation of the concepts will be assessed.
Rainer Lebert, Christian Wies, Bernhard Jaegle, Larissa Juschkin, Ulrich Bieberle, Manfred Meisen, Willi Neff, Klaus Bergmann, Konstantin Walter, Oliver Rosier, Max Schuermann, Thomas Missalla
Compact, flexible laboratory sources offer advanced flexibility in developing components for EUV-lithography by supplementing beamlines at storage rings. Hence, they are the basis for transferring EUV-metrology and technology to individual, industrial and university R&D labs. Laboratory sources have features similar to the sources planned for EUVL production on one hand and offer high flexibility like storage ring beamlines on the other hand.
Discharge based EUV sources offer some flexibility, which allow for tuning of the spectral and spatial characteristics of their emission. Depending on the system complexity sources can be supplied in various forms ranging from low budget semi-manual systems over OEM components to fully automatic stand-alone sources. As power scaling has been demonstrated by just adding higher power generators and cooling, these sources can be matched to various levels of flux requirements.
AIXUV’s discharge based EUV-sources have been used as beamline supplement for tasks closely connected with the development of EUV-Lithography. Examples are: development of tools for EUV source characterization (prototype testing, qualification and calibration), “in-band-EUV” open frame resist exposure, reflectometry of EUV mask blanks and EUV mirrors and for basic research using XUV radiation as thin film analytics and EUV microscopy.
The development of suitable radiation sources for extreme ultraviolet lithography (EUVL) is a major challenge. For the optimization of these sources and for the determination of the parameters needed for the system design and the system integration these sources have to be characterized in terms of the absolute in-band power, the spectral distribution in the EUV spectral region and the out-of-band spectral regions, the spatial distribution of the emitting volume and the angular distribution of the emission. For improving the lifetime of such sources, generally accepted as one key risk with EUVL, another task, the debris emitted from sources under development has to be investigated. Therefore, JENOPTIK Mikrotechnik GmbH is co-operating with the Laser Laboratorium Goettingen, the Physikalisch-Technische Bundesanstalt (PTB) and the AIXUV GmbH in developing ready-for-use metrology tools for EUVL source characterization and optimization. The set of the tools employed for EUV-source characterization is presented in detail as well as concepts for calibration and measurement procedures.
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.
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