Multilayer optics for XUV spectral region: technology fabrication and applications

We present research investigations in the field of multilayer optics in X-ray and extreme ultra-violet ranges (XUV), aimed at the development of optical elements for applications in experiments in physics and in scientific instrumentation. We discuss normal incidence multilayer optics in the spectral region of “water window”, multilayer optics for collimation and focusing of hard X-ray, multilayer dispersing elements for X-ray spectroscopy of high-temperature plasma, multilayer dispersing elements for analysis of low Z-elements. Our research pays special attention to optimization of multilayer optics for projection EUV-lithography (ψ-13nm) and short period multilayer optics.     

Microfocus X-Ray Tubes with a Silicon Autoemission Nanocathode as an X-Ray Source

To develop nanostructures with extremely low spatial resolution (to 10 nm and below), a new concept of the use of arrays of microfocus X-ray tubes based on field emission silicon nanocathodes is proposed. A new λ-tunable microfocus source of X-ray radiation, based on a thinfilm transmission target with field emission nanocathode with tunable wavelength, is proposed. The possibility of decreasing the exposed area size to 20 nm and smaller by varying the tube blocking voltage is shown. The use of these X-ray sources opens a new way of developing maskless X-ray lithography.     

Mo-based EUV multilayer filters with enhanced thermal stability

New Mo-based multilayer structures are proposed, and sample free-standing filters 160 mm in diameter with a transparency of 71% at a wavelength of λ = 13.5 nm are described. The enhanced thermo-oxidative stability of filters with Mo layers is demonstrated as opposed to Zr-based films. It is shown in particular that Mo-based filters can withstand vacuum heat annealing at 800°C for three hours without any optical and structural changes.     

Design of the aspheric Schwarzschild lens for a nanolithographer with the operating wavelength λ = 13.5 nm

The design of an aspheric Schwarzschild lens applicable to a nanolithographic test bench with an operating wavelength of 13.5 nm is discussed. Lenses with numerical apertures of 0.3 and 0.4 are examined. The influence of lens aberrations and deviations of optical scheme parameters from rated values on the image quality is analyzed.     

Particulars of studying the roughness of substrates for multilayer X-ray optics using small-angle X-ray reflectometry,atomic-force,and interference microscopy

The abilities of standard methods for rough surface investigation are analyzed in case of supersmooth substrates for multilayered X-ray optics. The X-ray specular reflection technique is shown to be the most adequate one. X-ray diffuse scattering and AFM can be applied only in a case of PSD-function calculation and approximation over the entire spectrum range of spatial frequencies.     

Multilayer X-ray mirrors based on La/B<Subscript>4</Subscript>C and La/B<Subscript>9</Subscript>C

Multilayer X-ray mirrors that are based on La/B₄C and La/B₉C and intended for the reflection of X-ray radiation in the spectral region near λ = 6.7 nm are prepared and studied. Reflection coefficients at a level of 40–60% are achieved for mirrors with various periods. The difference in the interlayer roughnesses reconstructed from the data measured in the hard and soft X-ray spectral regions is explained using a structural model with an asymmetric permittivity profile in a mirror period. A proximate technique is developed to estimate the permittivity profile in a multilayer-structure period using reflectometry data. The effect of antidiffusion Sn, Cr, and Mo barriers on the reflection coefficient of multilayer La/B₄C structures is studied experimentally     

Multilayer X-ray mirrors for the (4.4–5)-nm carbon-window spectral region

Cr/C-based multilayer X-ray mirrors intended for the reflection of X-ray radiation in the “carbon-window” spectral region (λ = 4.4–5 nm) are fabricated and studied. The structures are formed by magnetron sputtering at different deposition parameters. Under normal incidence, record reflection coefficients up to 15% are reached. The structural parameters of the mirrors are investigated by reflectometry at wavelengths of 0.154 and 4.47 nm.     

Comparative heat load testing of freestanding multilayer Mo/ZrSi2 and Mo/NbSi2

The thermal stability of multilayer thin-film Mo/ZrSi₂ and Mo/NbSi₂ filters in the temperature range of 840–940°C upon long-term heating in vacuum is investigated. The filter transmittance is measured before and after current annealing and a layer-by-layer SIMS analysis of the structure is performed. Comparative testing shows that the Mo/NbSi₂ structure is less thermostable at high thermal loads.     

Measurement Error of Interferometers with Diffraction Reference Wave

Technical Physics - An experimental setup and results on aberration of sources of a reference spherical wave (SRSW) based on a single-mode optical fiber with a subwavelength output aperture...