— A brief historical overview of the development of projection lithography in the extreme ultraviolet (EUV) range at a wavelength of 13.5 nm is presented. Using an eleven-mirror X-ray optical system as an example, the efficiency of a source—X-ray optics system for wavelengths of 13.5 nm (Mo/Si multilayer mirrors, tin laser-plasma source), 11.2 nm (Ru/Be multilayer mirrors, xenon source), and 10.8 nm (multilayer mirrors Ru/Sr, xenon source) is compared. Calculation is carried out taking into account experimental data on the reflection coefficients of multilayer mirrors and the conversion efficiency of laser-plasma X-ray sources based on multiply charged Sn and Xe ions. The maximum reflection coefficients of multilayer mirrors achieved are: R Mo/Si = 70.15%, R Ru/Be = 72.2%, and R Ru/Sr = 62.2%. The efficiency of conversion of laser-radiation energy into X-ray radiation based on Sn ions at a wavelength of 13.5 nm corrected for the actual transmission band of the X-ray optical system is taken equal to CE 13.5 = 5.4%. The conversion efficiency of the source based on Xe ions is taken equal to: CE 11.2 = 1.0% and CE 10.8 = 1.6%. The calculated productivity of lithographs expressed in arbitrary units at various wavelengths is: LP 13.5 = 0.1091, LP 11.2 = 0.0278, and LP 10.8 = 0.0089. Despite the lower productivity, due to significant simplification of the lithograph design and the lower cost of both the equipment and its operation, lithography at a wavelength of 11.2 nm has good prospects for practical application.

The article considers broadband multilayer X-ray mirrors based on Mo/Be and Mo/Si structures with a transmission band coinciding with the Si Lα (13.5 nm) and Sn (13.5 nm) emission lines. The described structures are of great interest for the currently developed liquid source of EUV radiation, since they make it possible to increase the efficiency of the source-X-ray optical system due to the "complete" capture of emission lines. Keywords: extreme ultraviolet radiation, emission spectrum, laser spark, multilayer X-ray mirror.

The work is devoted to the development, fabrication and analysis of broadband W / Si multilayer mirrors for a broadband monochromator, calculated for the spectral range of 7-10 keV. The possibility of using the stacking approach to obtain multilayer mirrors with a reflection coefficient of about 30% and a spectral bandwidth Delta E/E of about 20% is shown. The results of measurements of the angular and spectral reflection curves of the mirror obtained on a laboratory diffractometer and on a synchrotron in Novosibirsk are presented. Keywords: hard X-ray range, monochromator, synchrotron radiation, broadband mirrors, stack structures, multilayer X-ray mirrors.

The properties of Mo/B4C multilayer X-ray mirrors with periods of 3.74–3.84 nm are studied in this work. The dependences of the transmission band, reflection coefficient and the magnitude of internal stresses in mirrors on the ratio of material thicknesses in the period were investigated. The results of a study of the effect of thermal annealing on the structural parameters and reflective characteristics of mirrors are also presented in the paper.

The study of chemical interactions between Mo and B4C layers in multilayer structures depending on their total thickness (d) and thickness ratio (Gamma) was carried out using X-ray photoelectron spectroscopy (XPS) method. The results showed significant interactions of materials within the multilayer structures. Specifically, in the range of d from 1.8 to 3.4 nm and Gamma value between 0.24 and 0.46, a complete conversion of B4C into MoBxCy was observed, while retaining some amount of molybdenum. The insertion of tungsten barrier layer to the Mo-on-B4C interface led only to insignificant reduction of component MoBxCy. Based on the data obtained by XPS, theoretical models were developed and applied to X-ray reflectometry data during fitting procedure. The application of XPS has proven to be highly effective in constructing models and obtaining numerical values when fitting reflection curves.

Within the Universat program, a set of solar vacuum ultraviolet (VUV) telescopes has been developed for deployment on 6U nanosatellites. Telescopes are designed to get images of the solar corona. The spectral ranges of observations is considered, the characteristics of the nanosatellite from the point of view of the observations feasibility are opmized, the optical scheme of the telescope and VUV multilayer mirrors coatings and thin-film filters are modelled. Keywords: Nanosatellite, VUV, telescope, solar corona.

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. Keywords: X-ray lithography, multilayer X-ray optics, multilayer X-ray mirrors.

Record reflectivity’s of R EXP =23.8% at 3.14 nm and R CALC =30.8% at 3.12 nm have been obtained for Cr/Sc mirrors. Such increases in reflection are the result of decreases in mixing of the system layers with each other due to the use of interface-engineering methods – passivation of the already deposited Cr layer with nitrogen before deposition of the subsequent Sc layer. However, it has been found that adding additional B 4 C layers to such a system leads to a decrease in reflectivity.

The paper reports on a new Zr/Be/Si/Al multilayer structure that provides record reflectances of up to 67% and a spectral resolution of triangle lambda = 0.63 nm (lambda / triangle lambda approximate to 27) in the spectral range of 17-20 nm. It is shown that the structure has a high temporal stability of extreme ultraviolet (EUV) optical characteristics. This fact makes the structure promising for future missions to study the solar corona. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

The effect of annealing on the intermixing of thin Ti and Cr layers and their crystallinity in multilayer structures was studied using XPS, TEM, XRR and XRD methods. Multilayer structures with varios period values (sum thickness of the Ti and Cr layers) in the range from 1.4 nm to 4.3 nm were considered. The analysis revealed the formation of TiCrx at the interfaces of the layers. The contribution of the formed chromide relative to the base layers increases with decreasing period of the structure. The layers in the structure with thinnest period were found to be X-ray amorphous, while the structure with a thicker period exhibited the appearance of large crystallites of chromium and titanium. Annealing of the multilayer structures induced additional intermixing, leading to an increase in the extension of the chromide regions. Additionally, it resulted in a reduction of internal stresses within the structures. When the multilayer structures were annealed at a temperature of 700 degrees C, complete degradation occurred, with all layers intermixing with each other and with the Si substrate.

The effect of nitridation of Cr, Sc or both layers in the ultrathin multilayer structure Sc/Cr on the intermixing of thin Cr and Sc layers, as-deposited and after annealing at different temperatures were considered in details. The processes of passivation by nitrogen and synthesis in nitrogen medium of chromium and scandium layers are also compared. It was established that during passivation process the nitrogen interacts with surface of scandium film forming a ScNx compound and does not interact at all with the chromium layer. A net scavenging of nitrogen is observed in the case of CrNx/Sc system, while in the Sc/CrNx system the interaction of scandium with nitrogen gas before chromium layer deposition with formation of some amount of ScNx is added.Based on theoretical analysis of the effect of nitriding the system and detailed analysis carried out by photoelectron spectroscopy a multilayer system [Sc/CrNx]300 was synthesized and analyzed at different tem-peratures of annealing. Analysis of X-ray diffraction data showed that the sample consists of X-ray amorphous layers, the crystallinity of which practically does not change with increasing temperature. The results show that the [Sc/CrNx]300 system with small nitrogen content is very resistant to elevated temperatures up to 450 degrees C.

The X-ray optical and mechanical properties of dielectric multilayer mirrors based on pairs of C/Si and B4C/Si materials are synthesized and studied. The mirrors are optimized for a wavelength of 13.5 nm. Parameters of the deposition process that simultaneously ensure the fulfillment of three conditions are found: relatively high reflection coefficients at the operating wavelength, near-zero mechanical stresses in the film, and the absence of electrical conductivity. At zero internal stresses, the reflection coefficient of C/Si multilayer mirrors deposited onto superpolished silicon substrates at an operating wavelength of 13.5 nm is R = 11

The paper presents the results of studies of W/B4C multilayer structures with small periods for their use as the first mirror in a two-mirror soft X-ray monochromator at the KOSMOS station of the VEPP-4M synchrotron. It is shown that even if the periods of the mirror and the RbAP crystal coincide, when operating in a wide wavelength range, the Bragg angle must be adjusted due to the stronger refraction in the W/B4C multilayer mirror.

The reflective and structural parameters of Be/Si/Al multilayer mirrors have been studied. The extent of stability of their X-ray optical characteristics has been demonstrated during storage in air for 4 years and during vacuum annealing at temperatures up to 100°C. A high reflectance of 62.5% was obtained, together with a spectral selectivity of λ/Δλ≈59 at a wavelength of 17.14 nm and 34%, with λ/Δλ ≈ 31 at a wavelength of 31.3 nm. It was shown that Si interlayers reduce the interlayer roughness from 0.45 to 0.20 nm.

A brief description of the concept of a soft X-ray microscope for the Nanoscope station, which is planned to be installed at the SKIF fourth-generation synchrotron, is given. The microscope is designed to study the structure of cells and dynamic processes in them with nanometer spatial resolution. It will use a unique absorption contrast of ~15 between carbon-containing structures and water in the spectral range of the water window, λ = 2.3–4.3 nm, which eliminates the need for contrasting and the use of fluorophores and minimizes the doses of ionizing radiation absorbed in the samples to obtain high-quality 3D images. The scanning and projection schemes of the microscope, their main technical characteristics, including the calculated spectra and parameters of the undulator source are presented, and an estimate of the absorbed doses depending on the resolution is obtained. The main advantage of the proposed concept lies in the use of an objective lens of high-aperture multilayer X-ray mirrors, which makes it possible to clearly visualize the focal section of the sample. Technically simple axial tomography will also be used to reconstruct the three-dimensional structure of frozen or dried samples. In the scanning scheme, due to a low dose of radiation, it will be possible to study living plant cells with a resolution of up to 10 nm, animals with a resolution of up to 80 nm, and cryofixed samples with a resolution of up to 5 nm. In the projection scheme, due to simultaneous observation of the entire focal XY section, the time for obtaining three-dimensional images is significantly reduced, but due to a large dose, it will be oriented mainly on the study of fixed samples.

This study investigates mechanical stresses in Mo/Be/Si multilayer mirrors. We determined layer thicknesses (for Si-1.0 nm, Mo-2.8 nm and Be-3.2 nm) in the period that simultaneously provided high reflection coefficients (R-66-67%) at a wavelength of 13.5 nm with zero internal stress values. At the wavelength of 13.5 nm, the reflection coefficient of a stressless Mo/Be/Si multilayer mirror deposited on a micro-electro-mechanical system of micromirrors had a value of about 23% with a reflection from the witness of 67%. An interferometric method for determining the stress values in films, which is able to provide a measurement accuracy at the level of Delta s +/- 0.24 MPa, is described in detail.

The properties of Mo/B4C multilayer X-ray mirrors with periods of 3.74 – 3.84 nm are studied in this work. The dependences of the transmission band, reflection coefficient and the magnitude of internal stresses in mirrors on the ratio of material thicknesses in the period were investigated. The results of a study of the effect of thermal annealing on the structural parameters and reflective characteristics of mirrors are also presented in the paper.

Multilayer Mo/Be/Si mirrors with different ratios of Si- and Be-layer thicknesses in a period are considered. It is shown that the substitution of silicon with beryllium in the Mo/Si system makes it possible to completely eliminate internal stresses in the Mo/Be/Si structure. Layer thicknesses are found (Si 0.9 nm, Mo 2.8 nm, and Be 3.3 nm) that simultaneously provide high reflection coefficients (R 66–67

The reflection coefficient and microstructure of Mo/Be multilayer mirrors were studied as functions of Γ, the ratio of the Mo layer thickness to the period dp. The thickness and period of the layers were studied using X‑ray diffraction (wavelength 0.154 nm). Clearly defined high-intensity Bragg reflection peaks indicate good reproducibility of layer thicknesses over the depth of the multilayer structure and high quality of interfaces. The reflectivity of the mirror at a wavelength of 11.4 nm was maximum 62% at Γ = 0.42. It sharply decreased at higher and lower values of Γ. Both Mo and Be layers at Γ = 0.42 were polycrystals, which were studied using X-ray diffraction and Raman spectroscopy, respectively. It was also found that the sizes of crystallites almost coincided with the thicknesses of the Be and Mo layers in the period.

Effect of Si and Be barrier layers on the intermixing of thin Cr and Sc layers, as-deposited and after annealing in a wide range of temperatures was considered using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray reflectometry (XRR) and grazing-incidence X-ray diffraction (GIXRD). It was established that annealing of a Si/[Cr/Sc]200 system increases mixing. In the sample heated at a temperature of 450 degrees C during 1h as a result of a full intermixing of the Cr and Sc layers a segregation of scandium on the sample surface is traced. The structure becomes textured with Sc [001] preferred orientation perpendicular to the substrate. The insertion of the Be barrier layer in the Si/[Cr/Sc]200 system limits the intermixing between chromium and scandium layers during annealing at temperatures up to 350 degrees C, but full degradation of the structure occurs at 450 degrees C. Be barrier layer in the Cr/Sc system prevents a texturing and grain growth in the system, but does not oppose the crystallization process. A silicon layer inserted between the scandium and chromium layers restricts their intermixing. The multilayer retains an amorphous structure.