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.
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.
Extreme Ultraviolet Lithography (EUVL) is the favourite next generation lithography candidate for IC device manufacturing with feature sizes beyond 32nm. The SiO2 buffer dry etching is a crucial step in the manufacture of the EUV mask due to stringent CD and reflectance requirements. In contrast to conventional chromium absorber layers new absorber materials e.g. TaN require an adjustment of the SiO2 buffer etch chemistry and process parameters to avoid a strong influence on the initial absorber profile and thickness. We have developed a SiO2 buffer dry etch process that uses the structured TaN absorber as masking layer. A laser reflectometer was used during the SiO2 dry etch process for process control and endpoint detection. Different dry etch processes with SF6/He, CF4 and CHF3/O2 etch chemistry have been evaluated and compared with regard to TaN- and SiO2- etch rate, TaN- and SiO2 etch profile and Si capping layer selectivity. We focused our work on minimum feature sizes and simultaneous etching of different line (e.g. dense- and isolated lines) and hole patterns. Line and contact hole structures with feature sizes down to 100nm have been realized and characterized in a SEM LEO 1560. The whole mask patterning process was executed on an advanced tool set comprising of a Leica SB 350 variable shaped e-beam writer, a blank coater Steag HamaTech ASR5000, a developer Steag HamaTech ASP5000 and a two chamber UNAXIS mask etcher III.
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.
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.
The International Technology Roadmap for Semiconductors for Extreme Ultraviolet Lithography (EUVL) places strict requirements on the quality and flatness of the substrate and patterned mask. The SEMI EUVL Mask Substrate Standard (SEMI P37) specifies that the substrate frontside and backside nonflatness be no more than 50 nm peak-to-valley (p-v). Recent technological advances in polishing and finishing techniques have placed the 50 nm p-v specification within reach. A key ingredient in the development of EUVL is understanding and characterizing the clamping ability of the electrostatic chuck and the resulting effect on the flatness of the chucked mask. By implementing the shape of a representative EUVL mask surface into a numerical model, the effect of electrostatic chucking on the shape of the mask was determined. Legendre polynomials have been identified as an effective and efficient means of representing EUVL mask surface shapes. Finite element (FE) models have been developed to utilize the Legendre coefficients as input data to define the surfaces of an EUVL mask. The FE models were then used to determine the clamping response of the mask. In particular, the maximum mask-to-chuck gap within the Flatness Quality Area and over the entire mask has been tracked as a function of clamping pressure for representative EUVL surfaces. One of the important parameters in this study was the chuck's mechanical stiffness (comprised of the thickness and modulus). The flatness of the EUVL mask also depends on the intrinsic stress and thickness of the multilayer and backside layers. The results in this paper show that the recent advances in EUVL substrate polishing have resulted in masks that can be chucked relatively flat.
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 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.
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.
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.
We present a study of Distributed Feedback laser emission in various polymer materials. This laser scheme permits efficient control of the stimulated emission in dye doped polymer materials. Optical feedback is provided by distributed Bragg gratings formed in the film by interference patterns from the pump beam. We demonstrate broad tunability of laser emission in polymeric waveguides doped with stilbenoid, phenylene vinylene and oligomers of phenyl ethynylene used for OLEDs. Laser action was also obtained with Rhodamine 6G in PMMA deposited on surface relief grating and excited in a transverse single beam pumping geometry.
We present a study of Distributed Feedback laser emission in various polymer materials. This permits efficient control of the stimulated emission in dye doped polymer materials. Confinement and waveguiding effects are evidenced. We also propose a dynamical study of the effect using 4 wave mixing in the saturable absorption regime with stimulated emission.
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