17 research outputs found
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Initial development of efficient, low-debris laser targets for the Sandia soft x-ray projection lithography effort
During the fiscal years 92-94 a joint group from Sandia/New Mexico and Sandia/California studied the development of new laser-plasma targets for projection x-ray or EUV (extreme ultraviolet) lithography. Our experimental and theoretical analyses incorporated target design as an integral part of the lithographic optical system. Targets studied included thick solid targets, thin-foil metal-coated targets, and cryogenic targets. Our complete measurement suite consisted of x-ray conversion efficiency measurements, source size imaging, source x-ray angular distribution measurements, debris collection, and source EUV spectrum. Target evaluation also included the variation of laser characteristics, such as, laser intensity, spot size, wavelength, pulselength, and pulseshape. Over the course of these experiments we examined targets using KrF (248nm), XeCl (308nm), and CO{sub 2} (10.6 {mu}m) lasers. While debris issues now dominate research in this area, final details were concluded on our understanding of material spectra and radiation transport of 13 run light in laser-plasmas. Additionally, conclusive results were obtained with 308 rim light, showing the pulselength threshold below which plumes no longer limited the transmission of (and thus the conversion efficiency to) 13 nm radiation
Anisotropic optical response of the diamond (111)-2x1 surface
The optical properties of the 21 reconstruction of the diamond (111)
surface are investigated. The electronic structure and optical properties of
the surface are studied using a microscopic tight-binding approach. We
calculate the dielectric response describing the surface region and investigate
the origin of the electronic transitions involving surface and bulk states. A
large anisotropy in the surface dielectric response appears as a consequence of
the asymmetric reconstruction on the surface plane, which gives rise to the
zigzag Pandey chains. The results are presented in terms of the reflectance
anisotropy and electron energy loss spectra. While our results are in good
agreement with available experimental data, additional experiments are proposed
in order to unambiguously determine the surface electronic structure of this
interesting surface.Comment: REVTEX manuscript with 6 postscript figures, all included in uu file.
Also available at http://www.phy.ohiou.edu/~ulloa/ulloa.html Submitted to
Phys. Rev.
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Supersonic cluster jet source for debris-free extreme ultraviolet production
The supersonic cluster jet has been developed and characterized for use as a target medium to produce a clean source of extreme ultraviolet radiation for extreme ultraviolet lithography and other applications. Spectroscopic characterization of the laser plasma emission produced from Xe, O{sub 2} and Kr cluster gas targets has been performed. Xe is the most efficient target gas, exhibiting a conversion efficiency at 13.5 nm of 0.8% into the relevant 2.5% spectral bandwidth. The other target gases are less efficient in the spectral region of interest and, in the case of oxygen, emit {approximately}5 times less off-band radiation. The angular distribution of the Xe plasma emission has also been characterized
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High-power extreme ultraviolet source based on gas jets
The authors report on the development of a high power laser plasma Extreme Ultraviolet (EUV) source for Extreme Ultraviolet Lithography. The source is based on the plasma emission of a recycled jet beam of large Xe clusters and produces no particulate debris. The source will be driven by a pulsed laser delivering 1,500 W of focused average power to the cluster jet target. To develop condensers and to optimize source performance, a low power laboratory cluster jet prototype has been used to study the spectroscopy, angular distributions, and EUV source images of the cluster jet plasma emission. In addition, methods to improve the reflectance lifetimes of nearby plasma facing condenser mirrors have been developed. The resulting source yields EUV conversion efficiencies up to 3.8% and mirror lifetimes of 10{sup 9} plasma pulses
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Debris-free laser plasma sources for EUVL based on gas jets
EUV sources for EUVL must not only be bright for throughput, they must also be debris-free to increase condenser longevity. Many schemes to achieve bright, clean sources for EUVL have been studied, including mass-limited targets, cryogenic targets, electric discharges, and electron-beam pumped vapor. Several of these sources show promise, with varying degrees of brightness, debris reduction, and system complexity. We have studied pulsed gas jets, which we find to be relatively simple, debris-free sources when used under appropriate conditions. Under transverse, 1.06 {mu}m irradiation of the jet at incident laser intensities in the range of 10{sup 11}-10{sup 12} Watts/cm{sup 2}, the conversion efficiency into 2{pi} steradians is in the range of 0.3-0.4%, or approximately half the value exhibited by solid Au or W targets under similar conditions. Source sizes in the range of 350 {mu}m x 400 {mu}m can be achieved, as shown in Fig. 2, depending sensitively on both laser and gas jet parameters. One issue that must be overcome in the use of gas jet targets is the requirement that the laser-irradiated plasma be located as far from the jet nozzle as possible to avoid debris generation while maintaining adequate EUV conversion. We will describe conditions under which these criteria are met. Measurements of the reflectance lifetimes of multilayer-coated mirrors placed near the plasma source under these conditions will also be presented. The potential for scaling such sources up to meet the requirements of a commercial EUVL system will be discussed
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Large-solid-angle illuminators for extreme ultraviolet lithography with laser plasmas
Laser Plasma Sources (LPSS) of extreme ultraviolet radiation are an attractive alternative to synchrotron radiation sources for extreme ultraviolet lithography (EUVL) due to their modularity, brightness, and modest size and cost. To fully exploit the extreme ultraviolet power emitted by such sources, it is necessary to capture the largest possible fraction of the source emission half-sphere while simultaneously optimizing the illumination stationarity and uniformity on the object mask. In this LDRD project, laser plasma source illumination systems for EUVL have been designed and then theoretically and experimentally characterized. Ellipsoidal condensers have been found to be simple yet extremely efficient condensers for small-field EUVL imaging systems. The effects of aberrations in such condensers on extreme ultraviolet (EUV) imaging have been studied with physical optics modeling. Lastly, the design of an efficient large-solid-angle condenser has been completed. It collects 50% of the available laser plasma source power at 14 nm and delivers it properly to the object mask in a wide-arc-field camera