Influence of barrier interlayers on the performance of Mo/Be multilayer mirrors for next-generation EUV lithography

Stress, reflectance, and stability of Ru/Be multilayer coatings with Mo interlayers near the 11 nm wavelength

The stress, reflectance, and temporal stability of Ru/Be multilayer mirrors, both with and without Mo interlayers, were studied. A Ru/Be MLM was found to have zero stress at a Ru layer thickness-to-period ratio of γ ∼ 0.4. By adding Mo interlayers to both interfaces, it is possible to achieve a record-high reflectance (R > 71%) at a wavelength close to 11 nm while maintaining near-zero stress levels. A Ru/Be MLM with Mo interlayers at both interfaces also demonstrates high temporal reflectance stability. Ru/Be MLMs may be of interest for the next-generation projection lithography at a wavelength of 11.2 nm.

Investigation of structural and reflective characteristics of short-period Mo/B4C multilayer X-ray mirrors

The results of a study of the structural and reflective characteristics of short-period multilayer X-ray mirrors based on Mo/B4C at wavelengths 1.54 Å, 9.89 Å and 17.59 Å are presented. The period of the samples varied in the range 8-35 Å. The average widths of the interfaces were ∼3.5 and 2.2 Å at one and the other boundaries, with a tendency for weak growth with any decrease in the period. The interlayer roughness was ∼1 Å. The research results indicate promising prospects for the use of multilayer Mo/B4C mirrors for synchrotron applications.

Influence of Mo interlayers on the microstructure of layers and reflective characteristics of Ru/Be multilayer mirrors

The influence of Mo interlayers on the microstructure of films and boundaries, and the reflective characteristics of Ru/Be multilayer mirrors (MLM) were studied by X-ray reflectometry and diffractometry, and secondary ion mass spectrometry (SIMS). An increase in the reflection coefficients of MLM at a wavelength of 11.4 nm to record values of R = 72.2% and FWHM to Δλ_1/2= 0.38 nm is shown. The effect of interlayers on the structural and reflective characteristics of MLM is explained by the barrier properties of the Mo layers, which prevent the mutual mixing of the Ru and Be layers, which leads to the formation of beryllides and a decrease in the X-ray optical contrast at the boundaries.

Highly reflective Ru/Sr multilayer mirrors for wavelengths 9-12 nm

The results of investigations of Ru/Sr multilayer coatings optimized for the spectral range of 9-12 nm are presented in this Letter. Such mirrors are promising optical elements for solar astronomy and for the development of beyond extreme ultraviolet (BEUV) lithography. A near-normal incidence reflectivity of up to 62.3% (λ = 11.4 nm) right after the synthesis is measured. The reflection coefficient decreases to 56.8% after five days of storage in air with a subsequent stabilization of its value. At a wavelength of λ = 9.34 nm, the reflection coefficient is 48.6% after two months of storage in air. To date, to the best of our knowledge, this is the highest reflectivity measured in this spectral range. The possibility of further increasing the reflectivity is discussed.

Phase analysis of tungsten and phonon behavior of beryllium layers in W/Be periodic multilayers

In periodic W/Be multilayers, thickness-dependent microstructural and phase modifications were investigated in W and Be layers. In X-ray diffraction, α-W was predominant for the ultrathin layer of W, while β-W evolved along with the α-W phase for higher film thickness. For the thicker layers, the thermodynamically metastable β-W vanished and a single well-defined preferably oriented stable α-W phase was observed. The lattice spacing revealed that these phases exist in the tensile stressed condition. With the increase in thickness of Be layers, the blueshift and narrow linewidth of the transverse optical (TO) phonon mode was observed in Raman scattering studies. However, the TO mode was redshifted and the linewidth was further narrowed consistently with an increase in the thermal annealing temperature of the multilayers. The investigation has quantified an increase in compressive strain and reduction of defects with an increase in thickness of the Be layers. However, for thermally annealed samples, the compressive strain in the Be layers was relaxed and crystalline quality was improved.

Reflecting properties of narrowband Si/Al/Sc multilayer mirrors at 58.4 nm

This study considers the reflective characteristics of three-component Si/Al/Sc multilayer mirrors with a MoSi₂ protective cap layer as candidates for telescopes for observation of the solar corona in the He I (λ=58.4nm) spectral line. At 58.4 nm, a peak reflectance of 32% and a spectral width at a half-maximum intensity of Δλ=5.4nm are obtained. The temporal stability of the reflectance at λ=58.4nm for Si/Al/Sc samples with a 6 nm thick MoSi₂ cap layer is investigated during storage in air for 20 months.

Nanomaterials by design: a review of nanoscale metallic multilayers

Nanoscale metallic multilayers have been shown to have a wide range of outstanding properties, which differ to a great extent from those observed in monolithic films. Their exceptional properties are mainly associated with the large number of interfaces and the nanoscale layer thicknesses. Many studies have investigated these materials focusing on magnetic, mechanical, optical, or radiation tolerance properties. Thus, this review provides a summary of the findings in each area, including a description of the general attributes, the adopted synthesis methods and most common characterization techniques used. This information is followed by a compendium of the material properties and a brief discussion of related experimental data, as well as existing and promising applications. Other phenomena of interest, including thermal stability studies, self-propagating reactions and the progression from nano multilayers to amorphous and/or crystalline alloys, are also covered. In general, this review highlights the use of nano multilayer architectures as viable routes to overcome the challenges of designing and implementing new engineering materials at the nanoscale.

Multifitting: software for the reflectometric reconstruction of multilayer nanofilms

Multifitting is a computer program designed specifically for modeling the optical properties (reflection, transmission, absorption) of multilayer films consisting of an arbitrary number of layers in a wide range of wavelengths. Multifitting allows a user to calculate the reflectometric curves for a given structure (direct problem) and to find the parameters of the films from the experimentally obtained curves (inverse problem), either manually or automatically. Key features of Multifitting are the ability to work simultaneously with an arbitrary number of experimental curves and an ergonomic graphical user interface that is designed for intensive daily use in the diagnosis of thin films. Multifitting is positioned by the author as the successor to the IMD program, which has become the standard tool in research and technology groups synthesizing and studying thin-film coatings.