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Low-speckle holographic beam shaping of high-coherence EUV sources

Description: This paper describes a method to arbitrarily shape and homogenize high-coherence extreme ultraviolet sources using time-varying holographic optical elements and a scanning subsystem to mitigate speckle. In systems with integration times longer than 100 ms, a speckle contrast below 1% can be achieved.
Date: August 1, 2010
Creator: Anderson, Christopher N.; Miyakawa, Ryan H. & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department

A source for quantum control: generation and measurement of attosecond ultraviolet light pulses

Description: This project has pursued the possibility of producing ultra-short pulses of coherent light using harmonic conversion of a mid-infrared light source, focused into an atomic gas medium. This was a joint effort with Louis DiMauro's experimental group at Brookhaven National Laboratory and in collaboration with Ken Schafer from Louisiana State University and Mette Gaarde from Lund University on the theoretical part. High order harmonic generation (HHG) in nobel gas media using short-pulse visible and near infrared lasers has become an established method for producing coherent, short pulse radiation at wavelengths from the ultraviolet to soft x-rays. We recently proposed that this approach could lead to extremely short pulses, potentially less than one fs, provided the unavoidable frequency chirp of the highest harmonics, could be removed by compressing the pulses with a grating pair. Sources of sub-fs pulses would provide unique opportunities to study dynamical processes on time scales short compared to those associated with nuclear motion. Truly stroboscopic pictures of chemical reaction dynamics would be possible, for example. In this research project we have chosen much smaller driving frequencies than used previously in HHG studies for two reasons. First, this will allow us to measure the pulse lengths of the compressed harmonics because they will be in the vacuum ultraviolet where coincidence measurements are possible. Second, the wavelengths of these harmonics will be idea for pump-probe experiments of quantum dynamical control studies. Our theoretical effort was concentrated in two areas. We used our time-dependent quantum numerical codes to evaluate the harmonic response of alkali atoms to the mid-IR laser excitation. Results were obtained for potassium, the initial species to be used in the experiments, then sodium and rubidium to investigate the possibility of higher conversion efficiencies. In fact, rubidium was found to be significantly better than potassium, both because it ...
Date: February 19, 1999
Creator: Kulander, K C
Partner: UNT Libraries Government Documents Department

Adaptive Advantages of Carotenoid Pigments in Alpine and Subalpine Copepod Responses to Polycyclic Aromatic Hydrocarbon Induced Phototoxicity

Description: Alpine zooplankton are exposed to a variety of stressors in their natural environment including ultraviolet radiation. Physiological coping mechanisms such as the accumulation of photoprotective compounds provide these zooplankton protection from many of these stressors. Elevated levels of carotenoid compounds such as astaxanthin have been shown to help zooplankton survive longer when exposed to ultraviolet radiation presumably due to the strong antioxidant properties of carotenoid compounds. This antioxidant capacity is important because it may ameliorate natural and anthropogenic stressor-induced oxidative stress. While previous researchers have shown carotenoid compounds impart increased resistance to ultraviolet radiation in populations of zooplankton, little work has focused on the toxicological implications of PAH induced phototoxicity on zooplankton containing high levels of carotenoid compounds. This thesis discusses research studying the role that carotenoid compounds play in reducing PAH induced phototoxicity. By sampling different lakes at elevations ranging from 9,500' to 12,700' in the front range of the Colorado Rocky Mountains, copepod populations containing different levels of carotenoid compounds were obtained. These populations were then challenged with fluoranthene and ultraviolet radiation. Results discussed include differences in survival and levels of lipid peroxidation among populations exhibiting different levels of carotenoid compounds, and the toxicological and ecological implications of these results.
Date: May 2010
Creator: Kovach, Matthew James
Partner: UNT Libraries


Description: All the published atomic emission lines contained in the literature up to January 1959, are presented. Each line of data contains the vacuum wavelength in Angstroms, the element and spectroscopic notation for ionization the intensity, and reference numbers which refer to the list of references at the end of the report. Lists of intense lines arranged by ions, lines arranged by element, and binding lists are included. The intensities given in the tables are those published for spark sources. (W.D.M)
Date: January 1, 1959
Creator: Kelly, R.L.
Partner: UNT Libraries Government Documents Department

SEMATECH EUV resist benchmarking results

Description: Extreme Ultraviolet Lithography (EUVL) is one of the leading candidates for next generation lithography technology for the 32 nm HP and beyond. The availability of EUV resists is one of the most significant challenges facing its commercialization. To accelerate EUV resist development, SEMATECH provides access to two exposure tools: (1) The EUV Resist Test Center (RTC) at SEMATECH at the University at Albany, SUNY, NY; and (2) the SEMATECH microexposure tools (ALS-MET) at Lawrence Berkeley National Laboratory (LBNL).
Date: October 27, 2007
Creator: Ma, Andy; Park, Joo-On; Dean, Kim; Wurm, Stefan & Naulleau, Patrick
Partner: UNT Libraries Government Documents Department

A high-throughput contact-hole resolution metric for photoresists:Full-process sensitivity study

Description: The ability to accurately quantify the intrinsic resolution of chemically amplified photoresists is critical for the optimization of resists for extreme ultraviolet (EUV) Iithography. We have recently reported on two resolution metrics that have been shown to extract resolution numbers consistent with direct observation. In this paper we examine the previously reported contact-hole resolution metric and explore the sensitivity of the metric to potential error sources associated with the experimental side of the resolution extraction process. For EUV exposures at the SEMATECH Berkeley microfield exposure tool, we report a full-process error-bar in extracted resolution of 1.75 nm RMS and verify this result experimentally.
Date: January 22, 2008
Creator: Anderson, Christopher N. & Naulleau, Patrick P.
Partner: UNT Libraries Government Documents Department

Deprotection blue in extreme ultraviolet photoresists: influence of base loading and post-exposure bake temperture

Description: The deprotection blur of Rohm and Haas XP 5435, XP 5271, and XP5496 extreme ultraviolet photoresists has been determined as their base weight percent is varied. They have also determined the deprotection blur of TOK EUVR P1123 photoresist as the post-exposure bake temperature is varied from 80 C to 120 C. In Rohm and Haas XP 5435 and XP5271 resists 7x and 3x (respective) increases in base weight percent reduce the size of successfully patterned 1:1 line-space features by 16 nm and 8 nm with corresponding reductions in deprotection blur of 7 nm and 4 nm. In XP 5496 a 7x increase in base weight percent reduces the size of successfully patterned 1:1 line-space features from 48 nm to 38 nm without changing deprotection blur. In TOK EUVR P1123 resist, a reduction in post-exposure bake temperature from 100 C to 80 C reduces deprotection blur from 21 nm to 10 nm and reduces patterned LER from 4.8 nm to 4.1 nm.
Date: June 2, 2008
Creator: Anderson, Christopher N. & Naulleau, Patrick P.
Partner: UNT Libraries Government Documents Department

Extreme ultraviolet lithography: A few more pieces of the puzzle

Description: The work described in this dissertation has improved three essential components of extreme ultraviolet (EUV) lithography: exposure tools, photoresist, and metrology. Exposure tools. A field-averaging illumination stage is presented that enables nonuniform, high-coherence sources to be used in applications where highly uniform illumination is required. In an EUV implementation, it is shown that the illuminator achieves a 6.5% peak-to-valley intensity variation across the entire design field of view. In addition, a design for a stand-alone EUV printing tool capable of delivering 15 nm half-pitch sinusoidal fringes with available sources, gratings and nano-positioning stages is presented. It is shown that the proposed design delivers a near zero line-edge-rougness (LER) aerial image, something extremely attractive for the application of resist testing. Photoresist. Two new methods of quantifying the deprotection blur of EUV photoresists are described and experimentally demonstrated. The deprotection blur, LER, and sensitivity parameters of several EUV photoresists are quantified simultaneously as base weight percent, photoacid generator (PAG) weight percent, and post-exposure bake (PEB) temperature are varied. Two surprising results are found: (1) changing base weight percent does not significantly affect the deprotection blur of EUV photoresist, and (2) increasing PAG weight percent can simultaneously reduce LER and E-size in EUV photoresist. The latter result motivates the development of an EUV exposure statistics model that includes the effects of photon shot noise, the PAG spatial distribution, and the changing of the PAG distribution during the exposure. In addition, a shot noise + deprotection blur model is used to show that as deprotection blur becomes large relative to the size of the printed feature, LER reduction from improved counting statistics becomes dominated by an increase in LER due to reduced deprotection contrast. Metrology. Finally, this dissertation describes MOSAIC, a new wavefront metrology that enables complete wavefront recovery from print or aerial image ...
Date: May 20, 2009
Creator: Anderson, Christopher N.
Partner: UNT Libraries Government Documents Department

Validity of the thin mask approximation in extreme ultraviolet mask roughness simulations

Description: In the case of extreme ultraviolet (EUV) lithography, modeling has shown that reflector phase roughness on the lithographic mask is a significant concern due to the image plan speckle it causes and the resulting line-edge roughness on imaged features. Modeling results have recently been used to determine the requirements for future production worthy masks yielding the extremely stringent specification of 50 pm rms roughness. Owing to the scale of the problem in terms of memory requirements, past modeling results have all been based on the thin mask approximation. EUV masks, however, are inherently three dimensional in nature and thus the question arises as to the validity of the thin mask approximation. Here we directly compare image plane speckle calculation results using the fast two dimensional thin mask model to rigorous finite-difference time-domain results and find the two methods to be comparable.
Date: January 26, 2011
Creator: Naulleau, Patrick & George, Simi
Partner: UNT Libraries Government Documents Department

Actinic characterization of EUV bump-type phase defects

Description: Despite tremendous progress and learning with EUV lithography, quantitative experimental information about the severity of point-like phase defects remains in short supply. We present a study of measured, EUV aerial images from a series of well-characterized, open-field, bump-type programmed phase defects, created on a substrate before multilayer deposition.
Date: January 10, 2011
Creator: Goldberg, Kenneth A.; Mochi, Iacopo & Liang, Ted
Partner: UNT Libraries Government Documents Department

Ultraviolet Radiation Tolerance in High Elevation Copepods from the Rocky Mountains of Colorado, USA

Description: Copepods in high elevation lakes and ponds in Colorado are exposed to significant levels of ultraviolet radiation (UV), necessitating development of UV avoidance behavior and photoprotective physiological adaptations. The copepods are brightly pigmented due to accumulation of astaxanthin, a carotenoid which has photoprotective and antioxidant properties. Astaxanthin interacts with a crustacyanin-like protein, shifting its absorbance from 473 nm (hydrophobic free form, appears red) to 632 nm (protein-bound complex, appears blue). In six sites in Colorado, habitat-specific coloration patterns related to carotenoprotein complex have been observed. The objective of this study was to determine whether pigment accumulation or carotenoprotein expression has a greater effect on resistance to UV exposure. For each site, copepod tolerance to UV was assessed by survivorship during UV exposure trials. Average UV exposure was determined for each habitat. Astaxanthin profiles were generated for copepods in each site. Ability to withstand UV exposure during exposure trials was significantly different between color morphs (p < 0.0001). Red copepods were found to tolerate 2-fold greater levels of UVB than blue or mixed copepods. Additionally, red copepods have much higher levels of total astaxanthin than blue or mixed copepods (p < 0.0001) and receive a higher daily UV dose (p < 0.0003). Diaptomid carotenoprotein sequence is not homologous with that of other crustaceans in which crustacyanin has been characterized which prevented quantification of carotenoprotein transcript expression. Overall, diaptomid color morph may be an important indicator of UV conditions in high elevation lentic ecosystems.
Date: December 2011
Creator: Hudelson, Karista
Partner: UNT Libraries

Extreme Ultraviolet Lithography for 0.1 {micro}m Devices

Description: Extreme Ultraviolet Lithography (EUVL) has emerged as one of the leading successors to optics for 0.1 {micro}m IC fabrication. Its strongest attribute is the potential to scale to much finer resolution at high throughput. As such, this technique could meet the lithography needs for Si ULSI down to fundamental device limits. In the US, Lawrence Livermore, Sandia, and Lawrence Berkeley National Laboratories are participating in an industry funded research effort to evolve EUV technology and build a prototype camera for lithographic exposure. More recently, both Europe and Japan have initiated government/industry sponsored programs in EUVL development. This talk will focus on our program successes to date, and highlight some of the challenges that still lie ahead.
Date: July 7, 1999
Creator: Vaidya, S.; Sweeney, D.W.; Stulen, R. & Attwood, D.
Partner: UNT Libraries Government Documents Department

Masks for extreme ultraviolet lithography

Description: In extreme ultraviolet lithography (EUVL), the technology specific requirements on the mask are a direct consequence of the utilization of radiation in the spectral region between 10 and 15 nm. At these wavelengths, all condensed materials are highly absorbing and efficient radiation transport mandates the use of all-reflective optical systems. Reflectivity is achieved with resonant, wavelength-matched multilayer (ML) coatings on all of the optical surfaces - including the mask. The EUV mask has a unique architecture - it consists of a substrate with a highly reflective ML coating (the mask blank) that is subsequently over-coated with a patterned absorber layer (the mask). Particulate contamination on the EUVL mask surface, errors in absorber definition and defects in the ML coating all have the potential to print in the lithographic process. While highly developed technologies exist for repair of the absorber layer, no viable strategy for the repair of ML coating defects has been identified. In this paper the state-of-the-art in ML deposition technology, optical inspection of EUVL mask blank defects and candidate absorber patterning approaches are reviewed.
Date: September 1, 1998
Creator: Cardinale, G; Goldsmith, J; Kearney, P A; Larson, C; Moore, C E; Prisbrey, S et al.
Partner: UNT Libraries Government Documents Department

The Ultra-Violet and Visible Transmission of Various Colored Glasses

Description: Technical paper issued by the Bureau of Standards over studies conducted on transmissions of ultra-violet energy through different colored glasses. As stated in the introduction, "in the present paper are given the transmissions for the visible and ultra-violet of a large number of glasses, mostly colored, which are not used primarily for eye protection, but which are useful for various other purposes" (p. 3). This paper includes illustrations, and photographs.
Date: March 19, 1920
Creator: Gibson, K. S.; Tyndall, E. P. T. & McNicholas, H. J.
Partner: UNT Libraries Government Documents Department