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Journal ArticleDOI

Nanofabrication and diffractive optics for high-resolution x-ray applications

TL;DR: In this paper, a diffractive Fresnel zone plate lens was used for short wavelength x-ray radiation microscopy at the Advanced Light Source Synchrotron in Berkeley, California.
Abstract: Short wavelength x-ray radiation microscopy is well suited for a number of material and life science studies. The x-ray microscope (XM1) at the Advanced Light Source Synchrotron in Berkeley, California uses two diffractive Fresnel zone plate lenses. The first is a large condenser lens, which collects soft x-ray radiation from a bending magnet, focuses it, and serves as a linear monochromator. The second is the objective zone plate lens, which magnifies the image of the specimen onto a high-efficiency charge coupled device detector. The objective lens determines the numerical aperture and ultimate resolution. New objective lens zone plates with a minimum linewidth of 25 nm and excellent linewidth control have been fabricated using Berkeley Lab’s 100 keV Nanowriter electron beam lithography tool, a calixarene high-resolution negative resist, and gold electroplating. Although the condenser zone plate is less critical to the resolution of the instrument, its efficiency determines the flux on the sample and ul...

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Citations
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Journal ArticleDOI
30 Jun 2005-Nature
TL;DR: The achievement of sub-15-nm spatial resolution with a soft X-ray microscope—and a clear path to below 10 nm—using an overlay technique for zone plate fabrication is reported.
Abstract: The study of nanostructures is creating a need for microscopes that can see beyond the limits of conventional visible light and ultraviolet microscopes. X-ray imaging is a promising option. A new microscope described this week achieves unprecedented resolution, and has the ability to see through containing material. It features a specially made two-component zone plate — a lens with concentric zones rather like the rings in the Fresnel lenses familiar in overhead projectors and elsewhere — that makes use of diffraction to project an image into a CCD camera sensitive to soft X-rays. Spatial resolution of better than 15 nm is possible. Analytical tools that have spatial resolution at the nanometre scale are indispensable for the life and physical sciences. It is desirable that these tools also permit elemental and chemical identification on a scale of 10 nm or less, with large penetration depths. A variety of techniques1,2,3,4,5,6,7 in X-ray imaging are currently being developed that may provide these combined capabilities. Here we report the achievement of sub-15-nm spatial resolution with a soft X-ray microscope—and a clear path to below 10 nm—using an overlay technique for zone plate fabrication. The microscope covers a spectral range from a photon energy of 250 eV (∼5 nm wavelength) to 1.8 keV (∼0.7 nm), so that primary K and L atomic resonances of elements such as C, N, O, Al, Ti, Fe, Co and Ni can be probed. This X-ray microscopy technique is therefore suitable for a wide range of studies: biological imaging in the water window8,9; studies of wet environmental samples10,11; studies of magnetic nanostructures with both elemental and spin-orbit sensitivity12,13,14; studies that require viewing through thin windows, coatings or substrates (such as buried electronic devices in a silicon chip15); and three-dimensional imaging of cryogenically fixed biological cells9,16.

842 citations

Journal ArticleDOI
TL;DR: Two new soft X-ray scanning transmission microscopes located at the Advanced Light Source (ALS) have been designed, built and commissioned and interferometer control implemented in both microscopes allows the precise measurement of the transverse position of the zone plate relative to the sample.
Abstract: Two new soft X-ray scanning transmission microscopes located at the Advanced Light Source (ALS) have been designed, built and commissioned. Interferometer control implemented in both microscopes allows the precise measurement of the transverse position of the zone plate relative to the sample. Long-term positional stability and compensation for transverse displacement during translations of the zone plate have been achieved. The interferometer also provides low-distortion orthogonal x, y imaging. Two different control systems have been developed: a digital control system using standard VXI components at beamline 7.0, and a custom feedback system based on PC AT boards at beamline 5.3.2. Both microscopes are diffraction limited with the resolution set by the quality of the zone plates. Periodic features with 30 nm half period can be resolved with a zone plate that has a 40 nm outermost zone width. One microscope is operating at an undulator beamline (7.0), while the other is operating at a novel dedicated bending-magnet beamline (5.3.2), which is designed specifically to illuminate the microscope. The undulator beamline provides count rates of the order of tens of MHz at high-energy resolution with photon energies of up to about 1000 eV. Although the brightness of a bending-magnet source is about four orders of magnitude smaller than that of an undulator source, photon statistics limited operation with intensities in excess of 3 MHz has been achieved at high energy resolution and high spatial resolution. The design and performance of these microscopes are described.

636 citations


Cites methods from "Nanofabrication and diffractive opt..."

  • ...Zone plates with outermost zone widths as small as 20±25 nm have been fabricated, and a spatial resolution suf®cient to resolve half-period features 25±30 nm in size has been achieved (Anderson et al., 2000; Spector et al., 1997; Schneider et al., 1995; Denbeaux et al., 2001)....

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Journal ArticleDOI
TL;DR: Testing of the zone plate with the full-field transmission x-ray microscope, XM-1, in Berkeley, showed that the lens clearly resolved 12 nm lines and spaces, a significant step towards 10 nm resolution and beyond.
Abstract: To extend soft x-ray microscopy to a resolution of order 10 nm or better, we developed a new nanofabrication process for Fresnel zone plate lenses. The new process, based on the double patterning technique, has enabled us to fabricate high quality gold zone plates with 12 nm outer zones. Testing of the zone plate with the full-field transmission x-ray microscope, XM-1, in Berkeley, showed that the lens clearly resolved 12 nm lines and spaces. This result represents a significant step towards 10 nm resolution and beyond.

273 citations

Journal ArticleDOI
04 Feb 2008-Polymer
TL;DR: In this article, the authors provide an overview of the state-of-the-art synchrotron-based tools for soft X-ray characterization and discuss a number of applications to exemplify their unique aspects.

270 citations

Journal ArticleDOI
TL;DR: Using Fresnel zone plates made with robust nanofabrication processes, the authors achieved 10 nm spatial resolution with soft x-ray microscopy using a conventional full-field and scanning soft X-ray microscope, marking a significant step forward in extending the microscopy to truly nanoscale studies.
Abstract: Using Fresnel zone plates made with our robust nanofabrication processes, we have successfully achieved 10 nm spatial resolution with soft x-ray microscopy. The result, obtained with both a conventional full-field and scanning soft x-ray microscope, marks a significant step forward in extending the microscopy to truly nanoscale studies.

228 citations

References
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Journal ArticleDOI
TL;DR: Several conceivable methods for the formation of optical images by x-rays are considered, and a method employing concave mirrors is adopted as the most promising.
Abstract: Several conceivable methods for the formation of optical images by x-rays are considered, and a method employing concave mirrors is adopted as the most promising. A concave spherical mirror receiving radiation at grazing incidence (a necessary arrangement with x-rays) images a point into a line in accordance with a focal length f=Ri/2 where R is the radius of curvature and i the grazing angle. The image is subject to an aberration such that a ray reflected at the periphery of the mirror misses the focal point of central rays by a distance given approximately by S=1.5Mr2/R, where M is the magnification of the image and r is the radius of the mirror face. The theoretically possible resolving power is such as to resolve point objects separated by about 70A, a limit which is independent of the wave-length used. Point images of points and therefore extended images of extended objects may be produced by causing the radiation to reflect from two concave mirrors in series. Sample results are presented.

1,149 citations

Journal ArticleDOI
TL;DR: In this paper, a scanning transmission X-ray microscope with a 45 nm outer zone width and a 10% diffraction efficiency Fresnel zone plate as the probe-forming optic is presented.

249 citations

Journal ArticleDOI
TL;DR: In this paper, a nonpolymer material, calixarene derivative (hexaacetate p‐methnylcalix[6]arene) was tested as a high-resolution negative resist under an electron beam lithography process.
Abstract: A nonpolymer material, calixarene derivative (hexaacetate p‐methnylcalix[6]arene) was tested as a high‐resolution negative resist under an electron beam lithography process It showed under 10‐mm resolution with little side roughness and high durability to halide plasma etching A sub‐10‐nm Ge quantum wire was perfectly etched off without defects Such a performance is suitable for nanoscale device processes

227 citations

Journal ArticleDOI
TL;DR: In this article, the optimization of processes for producing sub-20 nm soft x-ray zone plates, using a general purpose electron beam lithography system and commercial resist technologies, was reported.
Abstract: We report here the optimization of processes for producing sub-20 nm soft x-ray zone plates, using a general purpose electron beam lithography system and commercial resist technologies. We have critically evaluated the failure point of the various process steps and where possible chosen alternate methods, materials, or otherwise modified the process. Advances have been made in most steps of the process, including the imaging resist, pattern conversion for electron beam exposure, and pattern transfer. Two phase shifting absorber materials, germanium and nickel, were compared. Zone plates with 30 nm outer zones have been fabricated in both germanium and nickel with excellent quality using polymethyl methyl accrylate and zones as small as 20 nm have been fabricated in nickel using the calixarene resist. The total efficiency as well as the efficiency of different regions of the zone plates were measured. All zone plates have demonstrated good efficiencies, with nickel zone plates performing better than german...

132 citations

Journal ArticleDOI
TL;DR: A vector scan pattern generator, optimized for smooth curvilinear as well as rectilinear primitive shapes, has been designed and constructed and initial lithography results confirm the operation of the system and stepping rates of 40 MHz have been achieved.
Abstract: A vector scan pattern generator, optimized for smooth curvilinear as well as rectilinear primitive shapes, has been designed and constructed. The pattern generator uses high‐speed hardware to implement a set of second‐order, quadratic equations to drive digital to analog converters and high‐speed array processors to calculate the coefficients for these equations. The digital pattern generator package contains the high‐speed digital, analog, and high‐resolution analog electronics. The initial lithography results confirm the operation of the system and stepping rates of 40 MHz have been achieved.

68 citations