Table-top Extreme Ultraviolet Laser Research Articles

Generation of collimated extreme ultraviolet radiation by single-photon process

Generating laser with short wavelength is a bottleneck problem in laser technology. The current applicable table-top extreme ultraviolet (EUV) lasers are all generated by multi-photon process with low efficiency. By utilizing metastable helium atoms excited by microwave and irradiated by a resonant laser, here we report the development of 58.4 nm collimated radiation by single-photon-excitation related anti-Stokes Raman scattering (ASRS). The conversion efficiency is much higher than that of high harmonic generation (HHG). The same divergence of 1.4 mrad as that of excitation laser indicates its stimulating character. Our results show an applicable path towards up-conversion by single-photon process to generate table-top EUV lasers.

Correction to Depth-Profiling Microanalysis of CoNCN Water-Oxidation Catalyst Using a λ = 46.9 nm Plasma-Laser for Nano-Ionization Mass Spectrometry.

Nanoscale depth profiling analysis of a CoNCN-coated electrode for water oxidation catalysis was carried out using table-top extreme ultraviolet (XUV) laser ablation time-of-flight mass spectrometr...

Depth-Profiling Microanalysis of CoNCN Water-Oxidation Catalyst Using a λ = 46.9 nm Plasma Laser for Nano-Ionization Mass Spectrometry.

Nanoscale depth profiling analysis of a CoNCN-coated electrode for water oxidation catalysis was carried out using table-top extreme ultraviolet (XUV) laser ablation time-of-flight mass spectrometry. The self-developed laser operates at λ = 46.9 nm and represents factor of 4 reduction in wavelength with respect to the 193 nm excimer laser. The reduction of the wavelength is an alternative approach to the reduction of the pulse duration, to enhance the ablation characteristics and obtain smaller quasi-nondestructive ablation pits. Such a XUV-laser ablation method allowed distinguishing different composite components of the catalyst-Nafion blend, used to modify a screen-printed carbon electrode surface. Chemical information was extracted by fragment assignment and relative amplitude analysis of the mass spectrometry peaks. Pure Nafion and the exposed carbon substrate were compared as references. Material specific fragments were clearly identified by the detected nonoverlappingmass-to-charge peaks of Nafion and CoNCN. Three dimensional mapping of relevant mass peak amplitudes was used to determine the lateral distribution and to generate depth profiles from consecutive laser pulses. Evaluating the profiles of pristine electrodes gave insight into fragmentation behavior of the catalyst in a functional ionomer matrix and comparison of post-catalytic electrodes revealed spots of thin localized Co residues.

Invited Article: Progress in coherent lithography using table-top extreme ultraviolet lasers.

Compact (table top) lasers emitting at wavelengths below 50 nm had expanded the spectrum of applications in the extreme ultraviolet (EUV). Among them, the high-flux, highly coherent laser sources enabled lithographic approaches with distinctive characteristics. In this review, we will describe the implementation of a compact EUV lithography system capable of printing features with sub-50 nm resolution using Talbot imaging. This compact system is capable of producing consistent defect-free samples in a reliable and effective manner. Examples of different patterns and structures fabricated with this method will be presented.

Defect-free periodic structures using extreme ultraviolet Talbot lithography in a table-top system

A compact nanofabrication system that combines Talbot lithography and a table-top extreme ultraviolet laser is presented. The lithographic method based on the Talbot effect provides a robust and simple experimental setup that is capable to print periodic structures over millimeter square areas free of defects. Test structures were printed and transferred into metal layers showing a complete coherent extreme ultraviolet lithographic process in a table-top system.

Tabletop single-shot extreme ultraviolet Fourier transform holography of an extended object

We demonstrate single and multi-shot Fourier transform holography with the use of a tabletop extreme ultraviolet laser. The reference wave was produced by a Fresnel zone plate with a central opening that allowed the incident beam to illuminate the sample directly. The high reference wave intensity allows for larger objects to be imaged compared to mask-based lensless Fourier transform holography techniques. We obtain a spatial resolution of 169 nm from a single laser pulse and a resolution of 128 nm from an accumulation of 20 laser pulses for an object ~11x11μm(2) in size. This experiment utilized a tabletop extreme ultraviolet laser that produces a highly coherent ~1.2 ns laser pulse at 46.9 nm wavelength.

Analysis of a scheme for de-magnified Talbot lithography

The authors describe a photolithographic scheme based on the replication of a periodic transparent mask in a photoresist utilizing the coherent self-imaging Talbot effect. A periodic two-dimensional diffractive structure (or Talbot mask) composed of unit tiles distributed in a square matrix was illuminated by a coherent extreme ultraviolet (EUV) beam from a table top EUV laser. The illumination beam was reflected in a spherical mirror and the Talbot mask was placed in the path of the convergent beam. At designed locations determined by the Talbot distance, reduced replicas of the mask were obtained and used to print the slightly de-magnified copies of the mask on the surface of a photoresist. Experimental results showing the de-magnification effect are in good agreement with the diffraction theory. The limits of the technique are discussed.

A study of the mechanical vibrations of a table-top extreme ultraviolet interference nanolithography tool

A prototype low cost table-top extreme ultraviolet (EUV) laser source (1.5 ns pulse duration, lambda=46.9 nm) was successfully employed as a laboratory scale interference nanolithography (INL) tool. Interference patterns were obtained with a simple Lloyd's mirror setup. Periodic structures on Polymethylmethacrylate/Si substrates were produced on large areas (8 mm(2)) with resolutions from 400 to 22.5 nm half pitch (the smallest resolution achieved so far with table-top EUV laser sources). The mechanical vibrations affecting both the laser source and Lloyd's setup were studied to determine if and how they affect the lateral resolution of the lithographic system. The vibration dynamics was described by a statistical model based on the assumption that the instantaneous position of the vibrating mechanical parts follows a normal distribution. An algorithm was developed to simulate the process of sample irradiation under different vibrations. The comparison between simulations and experiments allowed to estimate the characteristic amplitude of vibrations that was deduced to be lower than 50 nm. The same algorithm was used to reproduce the expected pattern profiles in the lambda/4 half pitch physical resolution limit. In that limit, a nonzero pattern modulation amplitude was obtained from the simulations, comparable to the peak-to-valley height (2-3 nm) measured for the 45 nm spaced fringes, indicating that the mechanical vibrations affecting the INL tool do not represent a limit in scaling down the resolution.

Holographic imaging with a nanometer resolution using compact table-top EUV laser

AbstractHolographic 2D/3D imaging with nanometer resolution using short wavelength extreme ultraviolet (EUV) light is presented in this paper. Gabor’s holograms were recorded with a highly coherent table top EUV laser with different numerical apertures demonstrating ultimately a spatial resolution of 46+/−2 nm, comparable with the illumination wavelength, in 2D holographic imaging. Three dimensional images were obtained from a single high numerical aperture hologram recorded in a high resolution photoresist and numerically reconstructed at different image planes, allowing numerical optical sectioning with a lateral resolution ∼170 nm and depth resolution of 2.4 µm. The holograms were recorded in a high resolution photoresist and digitized with an atomic force microscope. To assess the spatial resolution of the numerical reconstructions of the holograms a correlation method was used. The algorithm allows for simultaneous estimation of the resolution and the feature size of the image under analysis.

High resolution full-field imaging of nanostructures using compact extreme ultraviolet lasers

Recent advances in the development of high peak brightness table-top extreme ultraviolet (EUV) and soft x-ray (SRX) lasers have opened new opportunities for the demonstration of compact full-field EUV/SXR microscopes capable of capturing images with short exposures down to a single laser shot. We demonstrate the practical application of table-top zone plate EUV microscopes that can image nanostructures with a spatial resolution of 54 nm and below and exposure times as short as 1.2 ns, the duration of a single laser shot.

New opportunities in interferometric lithography using extreme ultraviolet tabletop lasers

The development of tabletop extreme ultraviolet EUV lasers opens now the possibility to realize interferometric lithography systems at EUV wavelengths that easily fit on the top of an optical table. The high degree of spatial and temporal coherence and high brightness of the compact EUV laser sources make them a good option for interferometric applications. The combination of these novel sources with interferometric lithography setups brings to the laboratory environment capabilities that so far had been restricted exclusively to large synchrotron facilities. © 2009 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.3129837 Subject terms: nanopatterning; interferometric lithography; extreme ultraviolet EUV lasers.

Large area interference lithography using a table-top extreme ultraviolet laser: a systematicstudy of the degree of mutual coherence

A prototype low cost table-top Ar capillary discharge laser source (1.5 ns pulse duration,λ = 46.9 nm) wassuccessfully used to produce, by means of interference lithography (with a simple Lloyd mirror setup), largearea (0.1 mm2) regular patterns from 400 nm down to 22.5 nm (half-pitch) on PMMA/Si (PMMA:polymethylmethacrylate) substrates. The experiments allowed a systematical investigationof the degree of mutual coherence of the source, giving a clear indication that theinterference lithography can be pushed down to the ultimate resolution limit ofλ/4.

Microscopy of extreme ultraviolet lithography masks with 132 nm tabletop laser illumination

We report the demonstration of a reflection microscope that operates at 13.2 nm wavelength with a spatial resolution of 55+/-3 nm. The microscope uses illumination from a tabletop extreme ultraviolet laser to acquire aerial images of photolithography masks with a 20 s exposure time. The modulation transfer function of the optical system was characterized.

Nanoscale patterning in high resolution HSQ photoresist by interferometric lithography with tabletop extreme ultraviolet lasers

Arrays of nanodots and nanoholes were patterned with a highly coherent tabletop 46.9nm laser on high resolution hydrogen silsesquioxane photoresist using multiple exposure interferometric lithography. The authors observed for λ=46.9nm radiation a penetration depth in excess of 150nm. This laser-based extreme ultraviolet interferometric setup allows printing of 0.5×0.5mm2 areas with different nanoscale patterns using a compact tabletop system and exposure times of tens of seconds.

Patterning of nano-scale arrays by table-top extreme ultraviolet laser interferometric lithography

Arrays of nanodots were directly patterned by interferometric lithography using a bright table-top 46.9 nm laser. Multiple exposures with a Lloyd's mirror interferometer allowed to print arrays of 60 nm FWHM features. This laser-based extreme ultraviolet interferometric technique makes possible to print different nanoscale patterns using a compact table-top set up.

Nanopatterning and Nanomachining with Table-top Extreme Ultraviolet Lasers

ABSTRACTNanopatterning and nanomachining of PMMA coated wafers was performed using table top extreme ultraviolet lasers. Features below 100 nm were imprinted with short (50-60 s) exposure times.

Nearly stigmatic toroidal grazing-incidence spectrometer in the 100–300-Å range: design

We have performed an initial design study on a single-element aberration-corrected holographic toroidal spectrometer for use in diagnosing extreme ultraviolet laser amplifiers that we plan to study as part of ourtabletop extreme ultraviolet laser project at MIT. The spectrometer is designed to be 7 m long from source to image with an incidence angle of 80 degrees and a 450-line/mm holographic grating. The instrument isdesigned to be nearly stigmatic between 100 and 300 A to sufficient precision to allow two-dimensional imaging with a 10-microm resolution. As a spectrometer the ideal resolution (with a zero slit width and a 25-microm spatial resolution at the image) is designed to be lambda/Deltalambda asymptotically equal to 5000.