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The paper proposes an X-ray optical scheme of a lithograph with a transmissive dynamic mask and a synchrotron radiation source. The image of a dynamic mask in the form of holes of small diameter is transferred with a decrease to a plate with a resist using a Schwarzschild projection lens. The formation of a topological pattern will occur due to the coordinated operation of the system for scanning a plate with a resist and a microelectromechanical system of a transmissive type. Objectives with a reduction of 10 and 20 times for obtaining 10–20 nm images of 200 nm holes of the dynamic mask are considered. The scheme of illumination of the mask is calculated, which provides uniform illumination on a field of 10 × 10 mm2. For the synchrotron Siberia-2 of the KISI on a bending magnet, the expected productivity of the lithograph will be up to 1/14 of a plate with a diameter of 100 mm per hour. [ABSTRACT FROM AUTHOR]

The paper discusses an optical layout for obtaining reduced X-ray oblique images, which can be useful for X-ray lithography problems. A special feature of the layout is the ability to illuminate the photomask at small grazing angles while recording images with minimal distortion. Using numerical simulations carried out for an X-ray laser with an operating wavelength of 13.9 nm, the spatial resolution and field of view of this system are found. [ABSTRACT FROM AUTHOR]

Promising wavelengths for next-generation lithography with a wavelength shorter than 13.5 nm based on a synchrotron X-ray source are discussed. Theoretical and experimental values of the reflection coefficients of multilayer X-ray mirrors providing the maximum reflectivity in the range of 11.4–3.1 nm are presented. The theoretical efficiency of multilayer optics is compared for different wavelengths. [ABSTRACT FROM AUTHOR]

The results of studies of Ru/Sr multilayer mirrors optimized for the working wavelength range of 9–12 nm are presented in the paper. Within the framework of the presented article the strontium based multilayer structures with stable over time reflective characteristics were obtained for the first time. It is shown that Ru/Sr mirrors have the highest reflectance of all known reflective coatings, with the exception of beryllium-containing, in the spectral range of 9–12 nm. [ABSTRACT FROM AUTHOR]

Beamlines on synchrotron radiation sources may impose different and sometimes even incompatible requirements to the X-ray beam. In some cases, implementation of probe methods for examination of samples in the mapping mode necessitates beams with the smallest possible cross–section. In contrast to this, radiation processing of material and manufacture of a commercial product using X-ray lithography approach require an X-ray beam with a relatively large area and providing a uniform exposure field. On the beamline X-Techno under development for the synchrotron radiation source SKIF, it will be possible to form synchrotron radiation beams up to 100 mm in size in the horizontal plane, differing in the spectral composition. Such beams will be used in any of the beamline's three research chambers for study of radiation effects in materials, as well as for creation of structures in the micro- and nano-size range. The design of the beamline will enable study of the physicochemical properties of materials exposed to X-rays in the spectral range from 2 to 70 keV. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of syndiotactic polymethyl methacrylate with a molecular weight of 107 g/mol, synthesized by the method of ionic polymerization with radiation initiation. Changes in the chemical structure of the polymer material were analyzed by means of IR spectroscopy, differential thermal analysis, and gel permeation chromatography. The process of weight loss during thermal decomposition of the initial polymer can be divided into three stages: low-temperature, medium-temperature, and high-temperature ones. After exposure of the polymer even to minimum doses of ionizing radiation, there is no pronounced thermal effect of polymer melting. A scatter in the molecular sizes was found, as well as a relatively rapid decrease in the molecular weight under the action of X-rays in the dose range of up to 100 J/cm3. Polydispersity at low doses is approximately 3.5 times higher than that at doses on the order of 10 kJ/cm3. The achieved rate of latent image development was approximately five times compared with the polymer with a molecular weight of 106 g/mol under standard conditions. The contrast was 3.4. Microstructuring was performed by the X-ray lithography method on the VEPP-3 source with the use of synchrotron X-rays. The resulting microstructures are up to 5 µm high and about 2 µm in diameter. [ABSTRACT FROM AUTHOR]

The paper presents a brief overview of the critical technologies required to create a modern lithography facility with an operating wavelength in the extreme ultraviolet (EUV) range. The principles of construction, current state, main problems, and prospects for the development of projection lithography at a wavelength of 13.5 nm are described. The principles of maskless X-ray lithography (MXRL) and the project of MXRL (demonstrator of technologies) developed by the authors are reported. MXRL solves the key problem of projection lithography, which consists in a strong dependence of the cost of the lithographic process on production volumes. On the basis of the MXLR demonstrator of technologies developed by the authors, analysis of the area of critical technologies and world-class experimental groundwork currently existing in Russia in the field of EUV radiation sources, the creation and metrology of high-precision aspherical substrates and multilayer X-ray mirrors, thin films for the suppression of long-wavelength radiation and the protection of optical elements from contamination by products of erosion of the tin-plasma source of EUV radiation, and decomposition of the photoresist under the influence of powerful EUV radiation are carried out. An experimental EUV lithograph created for the first time in Russia and an experimental model of a micro-electro-mechanical system of micromirrors reflecting EUV radiation and having no world analogues is reported. [ABSTRACT FROM AUTHOR]

To achieve better structural accuracy and aspect ratio, nano-gratings with a vertical angle close to 90° and a depth-to-width ratio of about 8 were prepared by synchrotron radiation. The optimal exposure dose and development time were determined to be 0.006 (A·h) and 6 min, respectively, by observing the surface loss and roughness of the gratings with slit widths of 150 nm and 250 nm under different conditions. To obtain the desired rectangular grating structure, the experimental conditions were optimized with the help of controlled variables experimental method. With the mask-to-photoresist pitch and the development and drying temperatures of 20 μ m and 23 °C, the optimized depth-to-width ratio of the nano-gratings with a slit width of 250 nm can reach 8.28. The cone angle can reach 88.4°. The aspect ratio of the nano-gratings with a slit width of 150 nm is 7.18, and its cone angle is 87.1°. [ABSTRACT FROM AUTHOR]

X-ray lithography has been first proposed almost 50 years ago, and the related LIGA process around 25 years ago. It is therefore a good time to make an analysis of the technique, with its pros and cons. In this perspective article, we describe X-ray lithography’s latest advancements. First, we report the improvement in the fabrication of the high aspect ratio and high-resolution micro/nanostructures. Then, we present the radiation-assisted synthesis and processing of novel materials for the next generation of functional devices. We finally draw our conclusion on the future prospects of the technique.

As a core component of 2D ultrasound transducers, honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays have attracted enormous attention due to their unique performance and functionality. In this paper, honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays with a high aspect-ratio were designed and fabricated by means of deep X-ray lithography and powder injection molding in six steps: preparation of lost mold, powder-binder mixing, injection molding and demolding, removal of binders, and densification of powder. A polymer-based lost mold insert was generated by a synchrotron X-ray exposure and development process. The optimal volumetric ratio between the piezoelectric powder and binders was determined by torque rheology behavior, then they were homogeneously mixed with a twin extruder mixer. To fully fill in the micro-cavities of the lost mold, rheological properties of the mixture were analyzed with a capillary rheometer using different shear rates (50–5000 s−1) and temperatures (140 °C, 150 °C, and 160 °C). After the mixture was completely injected, the lost mold was chemically dissolved in acetone and rinsed in methanol without bending or clustering of the micropillar arrays during evaporation. The binders in the injection molded portion were thermally decomposed using a continuous heating schedule of 200 °C, 390 °C, and 600 °C in argon gas under atmospheric conditions. Finally, the particles in the sample were densified into a coherent, solid mass by eliminating pores at 1300 °C. Based on the proposed micro-manufacturing process, defect-free honeycomb-shaped 1–3 connectivity piezoelectric micropillar arrays with a pattern dimension of 42 μm and aspect-ratio of 5 were successfully produced. [ABSTRACT FROM AUTHOR]

Synchrotron-based x-ray radiation has been utilized to measure time-resolved x-ray excited optical luminescence (TR-XEOL) from InGaN/GaN multiple quantum well (MQW) structures. Excess carrier recombination lifetimes were determined for MQWs grown on conventional c-plane as well as on non-polar m-plane substrates. In addition, the simultaneous measurement of XEOL and x-ray fluorescence reveals an interaction between inner-core excitations of Si impurities and bound exciton recombination in doped GaN-based device structures. Furthermore, the TR-XEOL characterization technique were also applied to InGaN/GaN MQWs grown on GaN inverted pyramid structures. [ABSTRACT FROM AUTHOR]

Fresnel zone plates for x-ray focusing optics are typically made using lithographic techniques. To achieve optimum efficiency for hard x rays, a depth of several microns is required, which limits the minimum zone width and hence minimum focal spot size achievable using lithography. We are exploring the fabrication of zone plates by an alternative technique that surmounts these limitations: the growth of a multilayer film to be used in transmission (Laue) diffraction geometry, in which the thickness of consecutive layers gradually increases according to the Fresnel zone formula; the film is sectioned after growth to the required depth. For a planar multilayer, this produces a linear zone plate that can focus x rays in one dimension. Here we report the growth and characterization of a depth-graded multilayer suitable for use as a zone plate for hard x-ray focusing. The multilayer has a total of 470 alternating layers of WSi2 and Si with thicknesses increasing monotonically from 15 to 60 nm, for a total thickness of 11.33 μm. One of the major challenges is to understand and select the right material system for this kind of thick multilayer. We have found that WSi2/Si is a promising system. A comparison between WSi2/Si and W/Si multilayers is presented. [ABSTRACT FROM AUTHOR]

Oblique submicron-scale structures are used in various aspects of research, such as the directional characteristics of dry adhesives and wettability. Although deposition, etching, and lithography techniques are applied to fabricate oblique submicron-scale structures, these approaches have the problem of the controllability or throughput of the structures. Here, we propose a simple X-ray-lithography method, which can control the oblique angle of submicron-scale structures with areas on the centimeter scale. An X-ray mask was fabricated by gold film deposition on slanted structures. Using this mask, oblique ZEP520A photoresist structures with slopes of 20° and 10° and widths of 510 nm and 345 nm were fabricated by oblique X-ray exposure, and the possibility of polydimethylsiloxane (PDMS) molding was also confirmed. In addition, through double exposure with submicron- and micron-scale X-ray masks, dotted-line patterns were produced as an example of multiscale patterning.

SyLMAND, the Synchrotron Laboratory for Micro and Nano Devices, is a recently commissioned microfabrication bend magnet beamline with ancillary cleanroom facilities at the Canadian Light Source. The synchrotron radiation is applied to pattern high‐aspect‐ratio polymer microstructures used in the area of micro‐electro‐mechanical systems (MEMS). SyLMAND particularly focuses on spectral and beam power adjustability and large exposable area formats in an inert gas atmosphere; a rotating‐disk intensity chopper allows for independent beam‐power reduction, while continuous spectral tuning between 1–2 keV and >15 keV photon energies is achieved using a double‐mirror system and low‐atomic‐number filters. Homogeneous exposure of samples up to six inches in diameter is performed in the experimental endstation, a vertically scanning precision stage (scanner) with tilt and rotation capabilities under 100 mbar helium. Commissioning was completed in late 2017, and SyLMAND is currently ramping up its user program, mostly in the areas of RF MEMS, micro‐fluidics/life sciences and micro‐optics. Microfabrication of high‐aspect‐ratio polymer structures using deep X‐ray lithography benefits from independent beam‐power and spectral tuning now available at the Synchrotron Laboratory for Micro and Nano Devices at the Canadian Light Source. [ABSTRACT FROM AUTHOR]

Photopolymer materials based on new polyacryl monomers of acrylate and mixed acrylate–acrylamide types have been obtained. Crosslinked films based on the synthesized monomers have been prepared by photopolymerization, and the thermomechanical properties of the crosslinked films have been studied. The storage modulus of the photopolymer films were determined at room temperature (1.3 and 1.5 GPa) and the glass transition temperature (82–93°С). High-aspect-ratio microstructures have been written using synchrotron radiation (SR) at the VEPP-3 storage ring (electron energy, 2 GeV) of a LIGA station at the Budker Institute of Nuclear Physics, SB RAS. It has been revealed that a synchrotron radiation dose of 1–15 J/cm3 results in polymerization of the monomers. The dependence of the thickness of a given microstructure on the absorbed SR dose has been found, and the corresponding characteristic curve has been constructed. Microstructures with an aspect ratio of 1 : 25 have been obtained. [ABSTRACT FROM AUTHOR]

Abstract A kind of prism-array refractive lens (PRL) for X-ray focusing composed of different prisms with the same width is designed and fabricated. In order to stabilize the whole structure and reduce the fabrication difficulty, bridges are introduced between the opposite two lines of tooth-like segments. The influence of the bridges on the focusing is investigated in theory, which will broaden the width of the focus. Furthermore, two PRLs with and without bridges for 50 keV X-rays are fabricated on the same substrate by X-ray lithography and are tested at BL13W1 beamline in Shanghai Synchrotron Radiation Facilities (SSRF). The bridges are designed a width of 5 μ m and the PRL sample with bridges has the better morphology than the one without bridges after fabrication. The on-line focusing test results show that the focal line width of the samples with and without bridges are 4. 20 μ m and 6. 34 μ m respectively, which implies that the bridges are necessary for the PRL with this fabrication method. Highlights • A kind of prism-array refractive lens (PRL) for 50 keV X-ray is fabricated. • Two PRLs with/without bridges are designed on the same substrate for comparison. • The bridge can influence the focusing in theory but also improve the PRL's profile. • The focal line width of the PRL without bridges is 6. 34 μ m. • The focal line width of the PRL with bridges is 4. 20 μ m. [ABSTRACT FROM AUTHOR]

This work presents a new fabrication technique for micro power inductors by using metal-embedded SU-8 slab molding techniques. The proposed technique uses X-ray lithography to fabricate high-aspect-ratio LIGA-like microstructures in form of embedded structures in the SU-8 slab. This process was applied to fabricate an inductor’s windings with an aspect ratio of 10, which can provide very low resistance but still preserve a small form factor and low profile. Inductors were designed as pot-core structures with overall heights of 370 μm and embedded with 250-μm-thick windings. From the advantage of metal embedded SU-8 slab techniques, 8 μm-thick permalloy core could be fabricated by electroplating around the winding in a single step that could help simplify the process. Four types of inductors were fabricated with 3, 5, 10, and 16 turns in the area of 1.8 to 9.5 mm2. The measured inductance was in the range of 70 nH to 1.3 μH at 1 MHz and DC resistance of 30–336 mΩ for 3–16 turns, respectively. The DC resistance of fabricated inductor was low, as expected, and showed good result compared with the results in literature. [ABSTRACT FROM AUTHOR]

Presents theoretical studies of the electron scattering effect on developed pattern profiles in X-ray lithography. Description of a Monte Carlo simulation of the production of photoelectrons and Auger electrons in a thin positive resist polymethyl methacrylate; Production of photoelectrons and Auger electrons; Simulation of generated electrons and etching profiles.

Discusses a study which explored X-ray projection lithography as a method for the manufacture of <200 nautical mile linewidth integrated circuits. Way of forming projected lithographic images; Computation of the form of the hologram; Requirement for an approach to projections X-ray lithography.

In combination with tapered-trench-etching of Si and SU-8 photoresist, a grayscale mask for deep X-ray lithography was fabricated and passed a 10-times-exposure test. The performance of the X-ray grayscale mask was evaluated using the TERAS synchrotron radiation facility at the National Institute of Advanced Industrial Science and Technology (AIST). Although the SU-8 before photo-curing has been evaluated as a negative-tone photoresist for ultraviolet (UV) and X-ray lithographies, the characteristic of the SU-8 after photo-curing has not been investigated. A polymethyl methacrylate (PMMA) sheet was irradiated by a synchrotron radiation through an X-ray mask, and relationships between the dose energy and exposure depth, and between the dose energy and dimensional transition, were investigated. Using such a technique, the shape of a 26-μm-high Si absorber was transformed into the shape of a PMMA microneedle with a height of 76 μm, and done with a high contrast. Although during the fabrication process of the X-ray mask a 100-μm-pattern-pitch (by design) was enlarged to 120 μm. However, with an increase in an integrated dose energy this number decreased to 99 μm. These results show that the X-ray grayscale mask has many practical applications. In this paper, the author reports on the evaluation results of SU-8 when used as a membrane material for an X-ray mask.

X-ray masks are indispensable tools in deep X-ray lithography (XRL). To date, hardly any fabrication technology can provide affordable and readily available masks with good structure quality. The bottleneck of adequate masks to a large extent limits the widespread use of XRL. In this article, an alternative XRL mask fabrication process is described to significantly improve availability and cost efficiency of XRL masks as key instruments in XRL processing: A 355 nm UV-laser is applied to expose SU-8 resist on an antireflective coating and a copper sacrificial substrate. The voids in this resist template are filled by a two-step electroplating process with sacrificial nickel and 3.6 μm thick gold absorbers. A second SU-8 coat embeds the absorbers, forming the 40 μm mask membrane. This configuration allows for XRL into resists of up to about 200 μm thickness at the SyLMAND beamline, Canada. The absorber structure accuracy is about 1 μm, at smallest tested lateral dimensions of 2 μm isolated features and 500 nm details. Upon release from the substrate, the membrane locally deforms by up to 1.79 μm. PMMA microstructures patterned with such a mask have smooth and vertical sidewalls. The SyLMAND chopper allows one to limit thermal deformations during exposure to the micrometer range: At a beam power of 0.42 W, typical thermal deformations are 0.5 μm–1.4 μm, depending on the layout, and position inaccuracies are about 3.3 μm. [ABSTRACT FROM AUTHOR]

In this article, application of micro-replication of polymers in the field of next generation mm-wave antennas is presented for the first time. The concept is applied to recently proposed template-based dielectric resonator antenna arrays fabricated by deep X-ray lithography. In this work, the array templates are replicated by hot embossing of polymethyl methacrylate (PMMA) layers using a nickel mold insert fabricated from the direct X-ray exposed PMMA master (LIGA process). Transfer quality of the master pattern is examined through measurements by optical microscope. Under controlled conditions, a number of templates are replicated demonstrating repeatable quality and consistent performance among the devices. A four element dielectric resonator antenna array is fabricated and measured for the impedance bandwidth response. This proposed methodology has the potential to enable low cost and mass utilization of dielectric resonator antennas and arrays in future millimeter-wave applications. [ABSTRACT FROM AUTHOR]

Grating-based X-ray phase contrast imaging is promising especially in the medical area. Two or three gratings are involved in grating-based X-ray phase contrast imaging in which the absorption grating of high-aspect-ratio is the most important device and the fabrication process is a great challenge. The material with large atomic number Z is used to fabricate the absorption grating for excellent absorption of X-ray, and Au is usually used. The fabrication process, which involves X-ray lithography, development and gold electroplating, is described in this paper. The absorption gratings with 4 m period and about 100 m height are fabricated and the high-aspect-ratio is 50. [ABSTRACT FROM AUTHOR]

In deep X‐ray lithography (DXRL), synchrotron radiation is applied to pattern polymer microstructures. At the Synchrotron Laboratory for Micro and Nano Devices (SyLMAND), Canadian Light Source, a chromium‐coated grazing‐incidence X‐ray double‐mirror system is applied as a tunable low‐pass filter. In a systematic study, the surface conditions of the two mirrors are analyzed to determine the mirror reflectivity for DXRL process optimization, without the need for spectral analysis or surface probing: PMMA resist foils were homogeneously exposed and developed to determine development rates for mirror angles between 6 mrad and 12 mrad as well as for white light in the absence of the mirrors. Development rates cover almost five orders of magnitude for nominal exposure dose (deposited energy per volume) values of 1 kJ cm−3 to 6 kJ cm−3. The rates vary from case to case, indicating that the actual mirror reflectivity deviates from that of clean chromium assumed for the experiments. Fitting the mirror‐based development rates to the white‐light case as a reference, reflectivity correction factors are identified, and verified by experimental and numerical results of beam calorimetry. The correction factors are related to possible combinations of a varied chromium density, chromium oxidation and a carbon contamination layer. The best fit for all angles is obtained assuming 7.19 g cm−3 nominal chromium density, 0.5 nm roughness for all involved layers, and an oxide layer thickness of 25 nm with a carbon top coat of 50 nm to 100 nm. A simulation tool for DXRL exposure parameters was developed to verify that the development rates for all cases do coincide within a small error margin (achieving a reduction of the observed errors by more than two orders of magnitude) if the identified mirror surface conditions are considered when calculating the exposure dose. [ABSTRACT FROM AUTHOR]

Featured Application: The characterization of negative photoresists before the application on LIGA process can be a key factor to save time, money and enhance the reproducibility of the main optical components fabricated to be used in techniques such as Talbot–Lau Interferometry. The quality of high aspect ratio microstructures fabricated by deep X-ray lithography is highly dependent on the photoresist material used and the process parameters applied. Even with photoresists more suitable to this process, it is common to face defects in the final optical components, such as in case of X-ray gratings. The gratings need to be fabricated with critical dimensions on a sub-micrometer and micrometer scale, with periods of few micrometers and heights of hundreds of micrometers to be used in X-ray imaging techniques such as Talbot–Lau Interferometry. During the fabrication process, these features lead to challenges such as mechanical stability, homogeneity, and defect-free grating patterns. Usually, an epoxy-based negative photoresist is used in X-ray lithography, which needs to account for the shrinkage that takes place during polymer crosslinking in order to avoid defects in the final pattern. Nowadays, photoresist material still lacks certain suitable properties (chemical and mechanical) to fabricate gratings of high quality and with acceptable reproducibility. This work presents the results of TGA, FTIR, and MALDI-TOF analysis made on photoresists commercially available and suitable for X-ray lithography. The photoresists presented different profiles regarding the solvent content and oligomers composition, and in the case of some samples, there were high amounts of non-epoxidized oligomers. [ABSTRACT FROM AUTHOR]

Fabrications of high-aspect-ratio microstructures (HARMS) using negative photoresist have been studied a lot by researchers recently, but the removal of the resist is still a problem. We report a method to fabricate HARMS using PMMA, a positive photoresist. A classical microstructure, densely packed micro square columns, was tried in our study. A top grid made of negative photoresists was employed to join all the separate parts together to prevent them from tilting or clumping. The development and electroplating processes were not influenced by the top grid. Excellent nickel micro-pores-structures were obtained finally, demonstrating that the method is a promising way to fabricate HARMS especially when the resist needs to be removed. [ABSTRACT FROM AUTHOR]

In deep x-ray lithography (DXRL), synchrotron radiation is applied to transfer absorber patterns on an x-ray mask into thick photoresist to generate high quality microstructures. Fabrication of the required x-ray masks is a demanding process sequence and constitutes a bottleneck in DXRL technology. Polymer-based mask membranes offer many benefits during mask fabrication and operation, but usually suffer from large thermal distortions during x-ray exposure. These are due to the low thermal conductivity of most polymers (approximately 0.2W/m K), which results in ineffi- cient heat transfer to the cooled areas around mask and substrate. The power tuning capabilities at the Synchrotron Laboratory for Micro and Nano Devices beamline, Canadian Light Source, however, allow the beam power to be adjusted and consequently limit thermal distortions. In this study, x-ray masks based on 30 lm thick polyimide membranes are studied. Numerical simulations of the thermal and thermoelastic behavior were performed using the software package ANSYS R14.5. The beam power input parameters were calculated with the software LEX-D. For experimental verification, a process to fabricate simple test masks was developed. The polymer membranes were processed on stainless steel sacrificial wafers and were patterned with 80 lm thick nickel absorbers in two macroscopic layouts. Five chromel/alumel (K-type) thermocouples where then bonded to the absorbers to measure the heat distribution. The measurements generally validated the numerical results. The simulated thermal distributions consistently overestimate the experimental values by approximately 4-6 K, which is mainly attributed to uncertainties in the experimental proximity gap settings. The thermal simulation results indicate that the dominant heating mechanism of the resist is conduction: Energy absorbed in the mask absorbers is conducted through the helium gas in the proximity gap to the nonexposed poly(methyl methacrylate) (PMMA) areas and the substrate (cooled to 18 °C). For 500 lm thick PMMA resist, exposed with a synchrotron beam power of 19.6 W, maximum temperatures in the mask are 31.0 and 25.8 °C in the resist below. Maximum single-axis resist deformations in the mask plane amount to 4.12 lm. At 250 lm resist thickness, the observed temperatures are only 25.4 °C in the mask and 22.3 °C in the resist, with maximum mask plane deformations of about 2.3 lm. Integrated over the entire absorber size of 60 mm, these deformations roughly double. Local structure accuracy results were obtained by measuring distortions in a micropatterned polyimide mask. Deformations verify simulation results, vary with the position on the layout, and scale with the incident beam power. At 3.3W incident beam power, typical deformations around 1-1.5 lm and maximum deformations of 2.3 lm were measured in 100 lm thick resist. [ABSTRACT FROM AUTHOR]

Abstracts Periodic nanostructures have attracted considerable interest and been applied in many fields. However, nanostructures of sufficiently large areas and depths are necessary for the development of practical devices. In this study, large-area high-aspect-ratio periodic nanostructures were fabricated by using a hybrid technology based on X-ray interference lithography, and then the patterns were transferred onto various substrates successfully. The final periodic nanostructures on the substrate attained measurements up to square centimetres with depths greater than 200 nm. [ABSTRACT FROM AUTHOR]

A pseudo-spin-valve (PSV) wire [Au(3 nm)/Py(10 nm)/Cu(5 nm)/Co(10 nm)/Si] was patterned by e-beam lithography into two sections with different widths, connected by a narrow part that acts as a domain wall trap. The two sections have different magnetic shape anisotropies and thus different coercive fields. Since the sample has two different magnetic layers (soft and hard) and two different anisotropies (thick and thin widths), this patterned system has more than two magnetic configuration states depending on the applied field strength. To probe local magnetization from the two different sections, x-ray magnetic circular dichroism (XMCD) measurements were done on the PSV wire with a microfocused x-ray beam. Measurements were done on the buried hard layer, from which magnetic information cannot be obtained by surface-sensitive techniques. The XMCD experimental results are compared with micromagnetic simulations. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this study, a fabrication method of tapered microstructures with high aspect ratio was proposed by deep X-ray lithography. Tapered microstructures with several hundred micrometers and high aspect ratio are demanded owing to the high applicability in the fields of various microelectromechanical systems (MEMS) such as optical components and microfluidic channels. However, as the pattern and gap size were downsized to smaller micro-scale with higher aspect ratio over 5, microstructures were easily deformed or clustered together due to capillary force during the drying process. Here, we describe a novel manufacturing process of tapered microstructures with high aspect ratio. To selectively block the deep X-ray irradiation, an X-ray mask was prepared via conventional ultraviolet (UV) lithography. A double X-ray exposure process with and without X-ray mask was applied to impose a two-step dose distribution on a photoresist. For the clear removal of the exposed region, the product was developed in the downward direction, which encourages a gravity-induced pulling force as well as a convective transport of the developer. After a drying process with the surface additive, tapered microstructures were successfully fabricated with a pattern size of 130 μm, gap size of 40 μm, and aspect ratio over 7.

We report the nanofabrication and characterization of x-ray transmission gratings with a high aspect ratio and a feature size of down to 65 nm. Two nanofabrication methods, the combination of electron beam and optical lithography and the combination of electron beam, x-ray, and optical lithography, are presented in detail. In the former approach, the proximity effect of electron beam lithography based on a thin membrane of low-z material was investigated, and the x-ray transmission gratings with a line density of up to 6666 lines/mm were demonstrated. In the latter approach, which is suitable for low volume production, we investigated the x-ray mask pattern correction during the electron beam lithography process and the diffraction effect between the mask and wafer during the x-ray lithography process, and we demonstrated the precise control ability of line width and vertical side-wall profile. A large number of x-ray transmission gratings with a line density of 5000 lines/mm and Au absorber thickness of up to 580 nm were fabricated. The optical characterization results of the fabricated x-ray transmission gratings were given, suggesting that these two reliable approaches also promote the development of x-ray diffractive optical elements. [ABSTRACT FROM AUTHOR]

In this paper, fabrication of poly-(methyl methacrylate) (PMMA) retinal tack using x-ray lithography and long-term in-vivo biocompatibility evaluation is presented for progressive observation by optical coherent tomography (OCT). The PMMA is used to fabricate the retinal tack for its transparency, which is necessary for OCT. It is fabricated using x-ray lithography for an accurate micro-patterning, which is very scalable and is suitable for inexpensive/repeatable mass production. The PMMA retinal tack has micro-patterned, barb-shaped scale bars to acquire correct interpretation of OCT findings, which can be influenced by the refractive index of the observed materials. The results can be used for progressive observation of the retina after implantation of microelectrode array, which can provide the influences of the degenerative retinal layers due to repeated electrical stimulation in long-term. [ABSTRACT FROM AUTHOR]

Nickel high energy X-ray compound kinoform lenses were fabricated by X-ray lithography technology at Beijing Synchrotron Radiation Facility. The nickel compound refractive lenses aim at focusing X-ray with 50 keV and the designed smallest width of the tooth-like segment is 2.5 μm. To keep the best morphology of the element, Au masks were made twice, whose thickness gradually increased. The fabrication process of compound lenses consists of three parts in general, including the intermediate mask (1.2 μm thick Au pattern) fabrication, the working mask (12 μm thick Au pattern) fabrication and the 300 μm high lenses fabrication. The intermediate mask was made by UV lithography (UV sample) and electron beam direct write lithography (EBDW sample) for comparison, and the EBDW sample had a better morphology than the UV sample at each step. Both samples were tested using the knife-edge scan method at BL13W1 beamline in Shanghai Synchrotron Radiation Facility, which provided the focal widths of 9.2 and 10.4 μm, and the photon flux gains of 6.9 and 5.4 for the EBDW and UV samples at an X-ray energy with 50 keV, respectively. [ABSTRACT FROM AUTHOR]

This paper describes a technological approach to the implementation of quasioptical high-pass subterahertz filters with the use of high-aspect pseudometallic structures. The approach is based on micropatterning a solid polymer layer of polymethylmethacrylate by means of synchrotron X-ray lithography with subsequent metallization of the entire surface of the structure. A fabricated specimen and operational characteristics for the filter with a cutoff frequency of 0.275 THz, which has the thickness of 1 mm and is formed by hexagon-shaped through-holes arranged on a triangular lattice with 70- μm wide crosspieces, are demonstrated. [ABSTRACT FROM AUTHOR]

In classical X-ray lithography, the mask and resist layer are arranged perpendicular to the incident X-ray beam. Being absorbed in the resist layer, the X-ray beam induces a response in the form corresponding to its cross section. However, using a tilt and rotation of the mask/resist and sequential repeated exposures, it is possible to create three-dimensional forms that are accurate to within less than a micron. New approaches to the creation of 3D microstructures by deep X-ray lithography are described, which can ensure the formation of relatively large arrays. [ABSTRACT FROM AUTHOR]

Studies the application of Ag-Se/Ge-Se inorganic resist in x-ray lithography using synchroton radiation. Characteristics of the inorganic resist; Methodology of the study; Discussion on the result of the study.

The quality of high aspect ratio microstructures fabricated by deep X-ray lithography is highly dependent on the photoresist material used and the process parameters applied. Even with photoresists more suitable to this process, it is common to face defects in the final optical components, such as in case of X-ray gratings. The gratings need to be fabricated with critical dimensions on a sub-micrometer and micrometer scale, with periods of few micrometers and heights of hundreds of micrometers to be used in X-ray imaging techniques such as Talbot–Lau Interferometry. During the fabrication process, these features lead to challenges such as mechanical stability, homogeneity, and defect-free grating patterns. Usually, an epoxy-based negative photoresist is used in X-ray lithography, which needs to account for the shrinkage that takes place during polymer crosslinking in order to avoid defects in the final pattern. Nowadays, photoresist material still lacks certain suitable properties (chemical and mechanical) to fabricate gratings of high quality and with acceptable reproducibility. This work presents the results of TGA, FTIR, and MALDI-TOF analysis made on photoresists commercially available and suitable for X-ray lithography. The photoresists presented different profiles regarding the solvent content and oligomers composition, and in the case of some samples, there were high amounts of non-epoxidized oligomers.

With the recent progress in downsizing and the sophistication of various industrial products, the need for more compact actuators is increasing. Actuators account for the larger percentage of volume and weight of a product compared with other parts and devices. We have proposed fabrication process of spiral micro coils that employs X-ray lithography. This process will be effective for fabricating coils of a high aspect ratio lines. Reducing the size of coil lines and increasing their aspect ratio are expected to reduce the size and increase the output of actuators. Using this process, we formed spiral coil lines that can be used in electromagnetic actuators. X-ray lithography was used to form a high aspect ratio helical structure on the surface of an acrylic resin pipe. As a measure to suppress void generation, which is one of the shortcomings of electroplating processes, the sputtering apparatus and plating equipment were improved, a pretreatment process was additionally provided, and the actual electroplating method was improved. As a result, a void-free metallic deposit could be formed on a thin coil line. At the final step of this research study, we etched the coil line to determine optimal etching conditions.

Coils are used in many electronic devices as inductors in mobile units such as mobile phone, digital cameras, etc. Inductance and quality factor of coils are very important value of the performance. Therefore, the requests for coils are small size, high inductance, low power consumption, etc. However, coils are unsuitable for miniaturization because of its structure. Therefore, we have proposed and developed the microcoils of high aspect ratio with the dipping method and an X-ray lithography technique. In dipping method, centrifugal force and highly viscous photoresist solution were key points to evenly apply resist in the form of thick film on metal bar. The film thickness of resist on bar was achieved about 50 μm after single coating. Using these techniques, we succeeded in creating threaded groove structure with 10 μm lines and spaces on 1 mm brass bar. In this case, the aspect ratio was achieved five. It is very expected the high performance microcoil with high aspect ratio lines could be manufactured in spite of the miniature size.