This self-contained, comprehensive book describes the fundamental properties of soft x-rays and extreme ultraviolet (EUV) radiation and discusses their applications in a wide variety of fields, including EUV lithography for semiconductor chip manufacture and soft x-ray biomicroscopy. The author begins by presenting the relevant basic principles such as radiation and scattering, wave propagation, diffraction, and coherence. He then goes on to examine a broad range of phenomena and applications. The topics covered include EUV lithography, biomicroscopy, spectromicroscopy, EUV astronomy, synchrotron radiation, and soft x-ray lasers. He also provides a great deal of useful reference material such as electron binding energies, characteristic emission lines and photo-absorption cross-sections. The book will be of great interest to graduate students and researchers in engineering, physics, chemistry, and the life sciences. It will also appeal to practicing engineers involved in semiconductor fabrication and materials science.

X-Rays and Extreme Ultraviolet Radiation: Principles and Applications

Among the various material growth techniques, physical vapor deposition of thin films encompasses many experimental forms. They can be categorized into equilibrium and none-quilibrium processes according to the ways in which the source materials are vaporized. Equilibrium process is typified by thermal evaporation including the conventional resistive heating, the more elaborate e-beam evaporation. as well as molecular beam epitaxy (MBE). Nonequilibrium processes include sputtering and many of its derivative forms such as ion beam deposition. In comparison with these techniques, thin-film deposition by laser evaporation is less well known and does not fall cleanly into either category. Depending on the laserconditions, the evaporation process can be either thermal, nonthermal, or a mixture of the two.

Growth of thin films by laser-induced evaporation

Recent advances in ultraviolet photodetectors

Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered, and therefore topics such as loop oscillations and flaring loops (except for non-solar ones which provide information on stellar loops) are not specifically addressed here. The observational section discusses loop classification and populations, and then describes the morphology of coronal loops, its relationship with the magnetic field, and the concept of loops as multi-stranded structures. The following part of this section is devoted to the characteristics of the loop plasma and of its thermal structure in particular, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics and flows are illustrated. In the modeling section some basics of loop physics are provided, supplying some fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are distinguished between those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. Then, more specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC) and impulsive (DC) heating. Finally, a brief discussion about stellar X-ray emitting structures related to coronal loops is included and followed by conclusions and open questions.

https://link.springer.com/content/pdf/10.12942%2Flrsp-2014-4.pdf

Coronal Loops: Observations and Modeling of Confined Plasma

We review the use of specular X-ray reflectivity (XRR) for the characterization of thin-film and surface structures. Specular X-ray scattering at small scattering vectors allows characterization of electron density profiles perpendicular to the surface on the length scale of 0.1 to 100 nm. This allows measurement of surface morphology, thin films, multilayer structures, and buried interfaces. The technique is nondestructive and can be applied in situ in a variety of processing environments. In the first half of the article, we review the theory and methods of XRR, including analysis of XRR spectra by a multilayer optical approach and a discussion of surface roughness measurements by XRR and other techniques. In the second half, we present a wide range of examples of XRR applications in thin-film structures, dynamic processes, liquid surfaces, and macromolecular structures.

Thin film and surface characterization by specular X-ray reflectivity

Optical methods that provide high diffraction image quality with a spatial resolution of several to tens of nanometers and are in demand in such areas as projection lithography, X-ray microscopy, astrophysics, and fundamental research on the interaction of matter (vacuum) with ultrahigh (– W cm) electromagnetic fields are reviewed in terms of fabrication and testing technologies and possible use in the – nm wavelength range. The current worldwide status of and recent achievements by the Institute for Physics of Microstructures of the Russian Academy of Sciences (RAS) in the field are discussed.

https://iopscience.iop.org/article/10.3367/UFNe.0182.201207c.0727/pdf

Precision imaging multilayer optics for soft X-rays and extreme ultraviolet bands

The effect of Be layers on the reflection coefficients of Mo/Be/Si multilayer mirrors in the extreme ultraviolet (EUV) region is reported. Samples were studied using laboratory and synchrotron based reflectometry, and high-resolution transmission electron microscopy. The samples under study have reflection coefficients above 71% at 13.5 nm and more than 72% at 12.9 nm in a near normal incidence mode. Calculations show that by optimizing the thickness of the Be layer it should be possible to increase the reflection coefficient by another 0.5–1%. These results are of considerable interest for EUV lithography.

High-reflection Mo/Be/Si multilayers for EUV lithography

Long-wave X-ray radiation mirrors

In the paper, we report development of two reflectometers in IPM RAS. One enables investigation of the angular and spectral characteristics of mirrors with any shape of a reflecting surface in the 0.6-20 nm spectral range. The other, designed especially to study the influence of EUV sources on the reflecting characteristics of the mirrors, allows testing of flat samples. Owing to a high aperture ratio (solid angle of 0.034 steradian), high reflection coefficient of mirrors, powerful windowless X-ray tube, and effective detector, the reflectometer provides a resolution of the reflection coefficient variation at a level of 0.1%.

Laboratory methods for investigations of multilayer mirrors in extreme ultraviolet and soft x-ray region

A polarimeter for soft X-rays and VUV radiation is described. Two Bragg reflectors at 45° incidence angle are used in the polarimeter. Multilayer mirrors with a suitable period and number of layers are chosen as reflectors. The polarimeter was tested on VEPP-2M storage ring with SR from a bending magnet and from the helical undulator.

Nikolai N. Salashchenko

Papers

Precision imaging multilayer optics for soft X-rays and extreme ultraviolet bands

High-reflection Mo/Be/Si multilayers for EUV lithography

Long-wave X-ray radiation mirrors

Laboratory methods for investigations of multilayer mirrors in extreme ultraviolet and soft x-ray region

A polarimeter for soft X-ray and VUV radiation