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Extreme Ultraviolet Phase Contrast Imaging

Description: The conclusions of this report are: (1) zone plate microscopy provides high resolution imaging of EUV masks; (2) using phase plates in the back focal plane of the objective lens can provide contrast mechanisms for measurement of the phase shift from defects on the mask; (3) the first high resolution EUV Zernike phase contrast images have been acquired; and (4) future work will include phase contrast mode in reflection from an EUV mask to directly measure the reflectivity and phase shift from defects.
Date: November 1, 2005
Creator: Denbeaux, Gregory; Garg, Rashi; Aquila, Andy; Barty, Anton; Goldberg, Kenneth; Gullikson, Eric et al.
Partner: UNT Libraries Government Documents Department

Holographic optical elements for the extreme-ultravioletregime

Description: As the development of extreme ultraviolet (EUV) lithography progresses, interest grows in the extension of traditional optical components to the EUV regime. The strong absorption of EUV by most materials and its extremely short wavelength, however, makes it very difficult to implement many components that are commonplace in the longer wavelength regimes. One such component is the diffractive optical element used, for example, in illumination systems to efficiently generate modified pupil fills. Here we demonstrate the fabrication and characterization of EUV binary phase-only computer-generated holograms allowing arbitrary far-field diffraction patterns to be generated.
Date: August 14, 2006
Creator: Naulleau, Patrick P.; Salmassi, Farhad; Gullikson, Eric M. & Anderson, Erik H.
Partner: UNT Libraries Government Documents Department

Spin-on-glass coatings for the generation of super-polishedsubstrates for extreme ultraviolet optics

Description: Substrates intended for use as extreme ultraviolet (EUV) optics have extremely stringent requirements in terms of finish. These requirements can dramatically increase the cost and fabrication time, especially when non-conventional shapes, such as toroids, are required. Here we present a spin-on-glass resist process capable of generating super-polished parts from inexpensive substrates. The method has been used to render diamond-turned substrates compatible for use as EUV optics. Toroidal diamond-turned optics with starting rms roughness in the 3.3 to 3.7 nm range have been smoothed to the 0.4 to 0.6 nm range. EUV reflectometry characterization of these optics has demonstrated reflectivities of approximately 63%.
Date: January 1, 2005
Creator: Salmassi, Farhad; Naulleau, Patrick P. & Gullikson, Eric M.
Partner: UNT Libraries Government Documents Department

Tri-material multilayer coatings with high reflectivity and wide bandwidth for 25 to 50 nm extreme ultraviolet light

Description: Magnesium/silicon carbide (Mg/SiC) multilayers have been fabricated with normal incidence reflectivity in the vicinity of 40% to 50% for wavelengths in the 25 to 50 nm wavelength range. However many applications, for example solar telescopes and ultrafast studies using high harmonic generation sources, desire larger bandwidths than provided by high reflectivity Mg/SiC multilayers. We investigate introducing a third material, Scandium, to create a tri-material Mg/Sc/SiC multilayer allowing an increase the bandwidth while maintaining high reflectivity.
Date: September 9, 2009
Creator: Aquila, Andrew; Salmassi, Farhad; Liu, Yanwei & Gullikson, Eric M.
Partner: UNT Libraries Government Documents Department

Progress in Large Period Multilayer Coatings for High Harmonic and Solar Applications

Description: Multilayer coatings for normal incidence optics designed for the long wavelength region (25 nm < {lambda} < 50 nm) are particularly challenging due to the few number of layers that can be utilized in the reflection. Recently, Mg/SiC multilayers have been fabricated with normal incidence reflectivity in the vicinity of 40% for wavelengths near the He-II line at 30.4 nm. Motivated by this success we have investigated the use of a tri-band multilayer to increase the bandwidth while maintaining the reflectivity. The multilayers were deposited by conventional magnetron sputtering. Using Mg/SiC bilayers a reflectivity of 45% was achieved at 27 to 32 nm at an angle of 5 deg from normal. The Mg/Sc/SiC multilayer systems have also been investigated. It obtained a near normal incidence reflectivity of 35% while increasing the bandwidth by a factor of 2. These results are very encouraging for the possibility of more widespread applications of normal incidence optics in high harmonic applications.
Date: January 7, 2008
Creator: Jones, Juanita; Aquila, Andrew; Salmassi, Farhad & Gullikson, Eric
Partner: UNT Libraries Government Documents Department

Ultra-high efficiency multilayer blazed gratings through deposition kinetic control

Description: Diffraction efficiency of multilayer coated blazed gratings (MBG) strongly depends on the perfection of the saw-toothshaped layers in the overall composite structure. Growth of multilayers on saw-tooth substrates should be carefully optimized in order to reduce groove profile distortion and at the same time to avoid significant roughening of multilayer interfaces. In this work we report on a new way to optimize growth of sputter-deposited Mo/Si multilayers on saw-tooth substrates through variation of the sputtering gas pressure. A new record for diffraction efficiency of 44% was achieved for a optimized MBG with groove density of 5250 lines/mm at the wavelength of 13.1 nm.
Date: January 23, 2012
Creator: Anderson, Erik; Gullikson, Eric; Salmassi, Farhad; Warwick, Tony; Yashchuk, Valeriy & Padmore, Howard
Partner: UNT Libraries Government Documents Department

Multilayer Phase-Only Diffraction Gratings: Fabrication andApplication to EUV Optics

Description: The use of phase-only diffractive devices has long played an important role in advanced optical systems in varying fields. Such devices include gratings, diffractive and holographic optical elements, diffractive lenses, and phase-shift masks for advanced lithography. Extending such devices to the increasingly important regime of extreme ultraviolet (EUV) wavelengths, however, is not trivial. Here, we present an effective fabrication and etch process enabling high-resolution patterning of Mo/Si multilayers for use in EUV phase devices, providing another method for fabrication of high numerical aperture diffractive devices or high-resolution EUV phase shift masks.
Date: May 1, 2007
Creator: Salmassi, Farhad; Gullikson, Eric M.; Anderson, Erik H. & Naulleau, Patrick P.
Partner: UNT Libraries Government Documents Department

Extreme ultraviolet mask substrate surface roughness effects on lithography patterning

Description: In extreme ultraviolet lithography exposure systems, mask substrate roughness induced scatter contributes to LER at the image plane. In this paper, the impact of mask substrate roughness on image plane speckle is explicitly evaluated. A programmed roughness mask was used to study the correlation between mask roughness metrics and wafer plane aerial image inspection. We find that the roughness measurements by top surface topography profile do not provide complete information on the scatter related speckle that leads to LER at the image plane. We suggest at wavelength characterization by imaging and/or scatter measurements into different frequencies as an alternative for a more comprehensive metrology of the mask substrate/multilayer roughness effects.
Date: June 21, 2010
Creator: George, Simi; Naulleau, Patrick; Salmassi, Farhad; Mochi, Iacopo; Gullikson, Eric; Goldberg, Kenneth et al.
Partner: UNT Libraries Government Documents Department

Out-of-band exposure characterization with the SEMATECH Berkeley 0.3-NA microfield exposure tool

Description: For the commercialization of extreme ultraviolet lithography (EUVL), discharge or laser produced, pulsed plasma light sources are being considered. These sources are known to emit into a broad range of wavelengths that are collectively referred to as the out-of-band (OOB) radiation by lithographers. Multilayer EUV optics reflect OOB radiation emitted by the EUV sources onto the wafer plane resulting in unwanted background exposure of the resist (flare) and reduced image contrast. The reflectivity of multilayer optics at the target wavelength of 13.5 nm is comparable to that of their reflectivity in the deep ultraviolet (DUV) and UV regions from 100-350 nm. The aromatic molecular backbones of many of the resists used for EUV are equally absorptive at specific DUV wavelengths as well. In order to study the effect of these wavelengths on imaging performance in a real system, we are in the process of integrating a DUV source into the SEMATECH Berkeley 0.3-NA Microfield Exposure Tool (MET). The MET plays an active role in advanced research in resist and mask development for EUVL and as such, we will utilize this system to systematically evaluate the imaging impact of DUV wavelengths in a EUV system. In this paper, we present the optical design for the new DUV component and the simulation-based imaging results predicting the potential impact of OOB based on known resist, mask, and multilayer conditions. It should be noted that because the projection optics work equally well as imaging optics at DUV wavelengths, the OOB radiation cannot be treated simply as uniform background or DC flare.
Date: February 23, 2009
Creator: George, Simi A.; Nauleau, Patrick; Rekawa, Senajith; Gullikson, Eric & Kemp, Charles D.
Partner: UNT Libraries Government Documents Department

Metrologies for the Phase Characterization of Attosecond

Description: EUV optics play a key role in attosecond science since only with higher photon energies is it possible to achieve the wide spectral bandwidth required for ultrashort pulses. Multilayer EUV mirrors have been proposed and are being developed to temporally shape (compress) attosecond pulses. To fully characterize a multilayer optic for pulse applications requires not only knowledge of the reflectivity, as a function of photon energy, but also the reflected phase of the mirror. This work develops the metrologies to determine the reflected phase of an EUV multilayer mirror using the photoelectric effect. The proposed method allows one to determine the optic's impulse response and hence its pulse characteristics.
Date: January 17, 2008
Creator: CXRO
Partner: UNT Libraries Government Documents Department

Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

Description: Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects we used an ionbeam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr{sup +} ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the Linear Continuous Model of film growth.
Date: January 23, 2012
Creator: Gawlitza, Peter; Cambie, Rossana; Dhuey, Scott; Gullikson, Eric; Warwick, Tony; Braun, Stefan et al.
Partner: UNT Libraries Government Documents Department

Fabrication and characterization of ultra-high resolution multilayer-coated blazed gratings

Description: Multilayer coated blazed gratings with high groove density are the most promising candidate for ultra-high resolution soft x-ray spectroscopy. They combine the ability of blazed gratings to concentrate almost all diffraction energy in a desired high diffraction order with high reflectance soft x-ray multilayers. However in order to realize this potential, the grating fabrication process should provide a near perfect groove profile with an extremely smooth surface of the blazed facets. Here we report on successful fabrication and testing of ultra-dense saw-tooth substrates with 5,000 and 10,000 lines/mm.
Date: July 26, 2011
Creator: Voronov,, Dmitriy; Anderson, Erik; Cambie, Rossana; Dhuey, Scott; Gullikson, Eric; Salmassi, Farhad et al.
Partner: UNT Libraries Government Documents Department

Growth and Printability of Multilayer Phase Defects on EUV MaskBlanks

Description: The ability to fabricate defect-free mask blanks is a well-recognized challenge in enabling extreme ultraviolet lithography (EUVL) for semiconductor manufacturing. Both the specification and reduction of defects necessitate the understanding of their printability and how they are generated and grow during Mo-Si multilayer (ML) deposition. A ML phase defect can be depicted by its topographical profile on the surface as either a bump or pit, which is then characterized by height or depth and width. The complexity of such seemingly simple phase defects lies in the many ways they can be generated and the difficulties of measuring their physical shape/size and optical effects on printability. An effective way to study phase defects is to use a programmed defect mask (PDM) as 'model' test sample where the defects are produced with controlled growth on a ML blank and accurate placement in varying proximity to absorber patterns on the mask. This paper describes our recent study of ML phase defect printability with resist data from exposures of a ML PDM on the EUV micro-exposure tool (MET, 5X reduction with 0.3NA).
Date: June 10, 2007
Creator: Liang, Ted; Ultanir, Erdem; Zhnag, Guojing; Park, Seh-Jin; Anderson, Erik; Gullikson, Eric et al.
Partner: UNT Libraries Government Documents Department

Development of an ultra-high resolution diffraction grating forsoft x-rays

Description: Resonant Inelastic X-ray Scattering (RIXS) is the one of themost powerful methods for investigation of the electronic structure ofmaterials, specifically of excitations in correlated electron systems.However the potential of the RIXS technique has not been fully exploitedbecause conventional grating spectrometers have not been capable ofachieving the extreme resolving powers that RIXS can utilize. State ofthe art spectrometers in the soft x-ray energy range achieve ~;0.25 eVresolution, compared to the energy scales of soft excitations andsuperconducting gap openings down to a few meV. Development ofdiffraction gratings with super high resolving power is necessary tosolve this problem. In this paper we study the possibilities offabrication of gratings of resolving power of up to 106 for the 0.5 1.5KeV energy range. This energy range corresponds to all or most of theuseful dipole transitions for elements of interest in most correlatedelectronic systems, i.e., oxygen K-edge of relevance to all oxides, thetransition metal L2,3 edges, and the M4,5 edges of the rare earths.Various approaches based on different kinds of diffraction gratings suchas deep-etched multilayer gratings, and multilayer coated echelettes arediscussed. We also present simulations of diffraction efficiency for suchgratings, and investigate the necessary fabricationtolerances.
Date: August 21, 2007
Creator: Voronov, Dmitriy L.; Cambie, Rossana; Feshchenko, Ruslan M.; Gullikson, Eric M.; Padmore, Howard A.; Vinogradov, Alexander V. et al.
Partner: UNT Libraries Government Documents Department

Fabrication and characterization of a new high density Sc/Si multilayer sliced grating

Description: State of the art soft x-ray spectroscopy techniques like Resonant Inelastic X-ray Scattering (RIXS) require diffraction gratings which can provide extremely high spectral resolution of 105-106. This problem may be addressed with a sliced multilayer grating with an ultra-high groove density (up to 50,000 mm-1) proposed in the recent publication [Voronov, D. L., Cambie, R., Feshchenko, R. M., Gullikson, E., Padmore, H. A., Vinogradov, A. V., Yashchuk, V. V., Proc. SPIE 6705, 67050E (2007)]. It has been suggested to fabricate such a grating by deposition of a soft x-ray multilayer on a substrate which is a blazed saw-tooth grating (echellette) with low groove density. Subsequent polishing applied to the coated grating removes part of the coating and forms an oblique-cut multiline structure that is a sliced multilayer grating. The resulting grating has a short-scale periodicity of lines (bilayers), which is defined by the multilayer period and the oblique-cut angle. We fabricated and tested a Sc/Si multilayer sliced grating suitable for EUV applications, which is a first prototype based on the suggested technique. In order to fabricate an echellette substrate, we used anisotropic KOH etching of a Si wafer. The etching regime was optimized to obtain smooth and flat echellette facets. A Sc/Si multilayer was deposited by dc-magnetron sputtering, and after that it was mechanically polished using a number of diamond pastes. The resulting sliced grating prototype with ~;;270 nm line period has demonstrated a dispersive ability in the 41-49 nm photon wavelength range with a diffraction efficiency of ~;;7percent for the optimized 38th order assigned to the echellette grating of 10 mu m period.
Date: July 21, 2008
Creator: Source, Advanced Light; Voronov, Dmitriy L.; Cambie, Rossana; Gullikson, Eric; Yashchuk, Valeriy; Padmore, Howard et al.
Partner: UNT Libraries Government Documents Department

Determining the Critcial Size of EUV Mask Substrate Defects

Description: Determining the printability of substrate defects beneath the extreme ultraviolet (EUV) reflecting multilayer stack is an important issue in EUVL lithography. Several simulation studies have been performed in the past to determine the tolerable defect size on EUV mask blank substrates but the industry still has no exact specification based on real printability tests. Therefore, it is imperative to experimentally determine the printability of small defects on a mask blanks that are caused by substrate defects using direct printing of programmed substrate defect in an EUV exposure tool. SEMATECH fabricated bump type program defect masks using standard electron beam lithography and performed printing tests with the masks using an EUV exposure tool. Defect images were also captured using SEMATECH's Berkeley Actinic Imaging Tool in order to compare aerial defect images with secondary electron microscope images from exposed wafers. In this paper, a comprehensive understanding of substrate defect printability will be presented and printability specifications of EUV mask substrate defects will be discussed.
Date: February 28, 2008
Creator: Mccall, Monnikue M.; Han, Hakseung; Cho, Wonil; Goldberg, Kenneth; Gullikson, Eric; Jeon, Chan-Uk et al.
Partner: UNT Libraries Government Documents Department

Determining the critical size of EUV mask substrate defects

Description: Determining the printability of substrate defects beneath the extreme ultraviolet (EUV) reflecting multilayer stack is an important issue in EUVL lithography. Several simulation studies have been performed in the past to determine the tolerable defect size on EUV mask blank substrates but the industry still has no exact specification based on real printability tests. Therefore, it is imperative to experimentally determine the printability of small defects on a mask blanks that are caused by substrate defects using direct printing of programmed substrate defect in an EUV exposure tools. SEMATECH fabricated bump type program defect masks using standard electron beam lithography and performed printing tests with the masks using an EUV exposure tool. Defect images were also captured using SEMATECH's Berkeley Actinic Imaging Tool in order to compare aerial defect images with secondary electron microscope images from exposed wafers. In this paper, a comprehensive understanding of substrate defect printability will be presented and printability specifications of EUV mask substrate defects will be discussed.
Date: May 26, 2008
Creator: Goldberg, Kenneth A.; Gullikson, Eric M.; Han, Hakseung; Cho, Wonil; Jeon, Chan-Uk & Wurm, Stefan
Partner: UNT Libraries Government Documents Department

EUV actinic defect inspection and defect printability at the sub-32 nm half pitch

Description: Extreme ultraviolet (EUV) mask blanks with embedded phase defects were inspected with a reticle actinic inspection tool (AIT) and the Lasertec M7360. The Lasertec M7360, operated at SEMA TECH's Mask Blank Development Center (MBDC) in Albany, NY, has a sensitivity to multilayer defects down to 40-45 nm, which is not likely sufficient for mask blank development below the 32 nm half-pitch node. Phase defect printability was simulated to calculate the required defect sensitivity for a next generation blank inspection tool to support reticle development for the sub-32 nm half-pitch technology node. Defect mitigation technology is proposed to take advantage of mask blanks with some defects. This technology will reduce the cost of ownership of EUV mask blanks. This paper will also discuss the kind of infrastructure that will be required for the development and mass production stages.
Date: August 1, 2009
Creator: Huh, Sungmin; Kearney, Patrick; Wurm, Stefan; Goodwin, Frank; Han, Hakseung; Goldberg, Kenneth et al.
Partner: UNT Libraries Government Documents Department

Replicated mask surface roughness effects on EUV lithographic pattering and line edge roughness

Description: To quantify the roughness contributions to speckle, a programmed roughness substrate was fabricated with a number of areas having different roughness magnitudes. The substrate was then multilayer coated. Atomic force microscopy (AFM) surface maps were collected before and after multilayer deposition. At-wavelength reflectance and total integrated scattering measurements were also completed. Angle resolved scattering based power spectral densities are directly compared to the AFM based power spectra. We show that AFM overpredicts the roughness in the picometer measurements range. The mask was then imaged at-wavelength for the direct characterization of the aerial image speckle using the SEMATECH Berkeley Actinic Inspection Tool (AIT). Modeling was used to test the effectiveness of the different metrologies in predicting the measured aerial-image speckle. AIT measured contrast values are 25% or more than the calculated image contrast values obtained using the measured rms roughness input. The extent to which the various metrologies can be utilized for specifying tolerable roughness limits on EUV masks is still to be determined. Further modeling and measurements are being planned.
Date: March 11, 2011
Creator: George, Simi A.; Naulleau, Patrick P.; Gullikson, Eric M.; Mochi, Iacopo; Salmassi, Farhad; Goldberg, Kenneth A. et al.
Partner: UNT Libraries Government Documents Department

Absolute sensitivity calibration of extreme ultraviolet photoresists

Description: One of the major challenges facing the commercialization of extreme ultraviolet (EUV) lithography remains simultaneously achieving resist sensitivity, line-edge roughness, and resolution requirement. Sensitivity is of particular concern owing to its direct impact on source power requirements. Most current EUV exposure tools have been calibrated against a resist standard with the actual calibration of the standard resist dating back to EUV exposures at Sandia National Laboratories in the mid 1990s. Here they report on an independent sensitivity calibration of two baseline resists from the SEMATECH Berkeley MET tool performed at the Advanced Light Source Calibrations and Standards beamline. The results show the baseline resists to be approximately 1.9 times faster than previously thought based on calibration against the long standing resist standard.
Date: May 16, 2008
Creator: Jones, Juanita; Naulleau, Patrick P.; Gullikson, Eric M.; Aquila, Andrew; George, Simi & Niakoula, Dimitra
Partner: UNT Libraries Government Documents Department

Molecular orientation in soft matter thin films studied by resonant soft X-ray reflectivity

Description: We present a technique to study depth profiles of molecular orientation in soft matter thin films with nanometer resolution. The method is based on dichroism in resonant soft X-ray reflectivity using linear s- and p-polarization. It combines the chemical sensitivity of Near-Edge X-ray Absorption Fine Structure spectroscopy to specific molecular bonds and their orientation relative to the polarization of the incident beam with the precise depth profiling capability of X-ray reflectivity. We demonstrate these capabilities on side chain liquid crystalline polymer thin films with soft X-ray reflectivity data at the carbon K edge. Optical constants of the anisotropic refractive index ellipsoid were obtained from a quantitative analysis using the Berreman formalism. For films up to 50 nm thickness we find that the degree of orientation of the long axis exhibits no depth variation and isindependent of the film thickness.
Date: January 12, 2011
Creator: Mezger, Markus; Jerome, Blandine; Kortright, Jeffrey B.; Valvidares, Manuel; Gullikson, Eric; Giglia, Angelo et al.
Partner: UNT Libraries Government Documents Department