M. M. Barysheva

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.

The evolution of roughness of supersmooth surfaces by ion-beam etching

The behavior of roughness on surfaces of Cr/Sc multilayer structure, crystalline silicon [100], and fused quartz upon ion beam etching in the region of middle and high frequencies of the spatial spectrum (10−2–102 μm−1) is studied. The possibility of keeping surface roughness at level σ ∼ 0.3 nm upon etching by Ar atoms/ions to depths of up to 10 μm is demonstrated.

Investigation of supersmooth optical surfaces and multilayer elements using soft X-ray radiation

The aim of this work is application of soft X-ray diffuse scattering for certification of diffractiongrade optical elements and their substrates at a working wavelength. A device is suggested that allows certification under laboratory conditions owing to a dynamic range approaching that of synchrotron radiation sources. Experimental data are compared with data of alternative methods.

Problem of roughness detection for supersmooth surfaces

The requirements for multilayered x-ray elements for diffraction quality imaging optics (EUV - lithography, x-ray microscopy) achieves 0.2-0.3 nm roughness in spatial frequency range 10-3 - 103 mcm-1; its also true for the substrates. Although, there are plenty of publications on studying a surface, when it comes to angstrom-quality substrates there is still a problem. In some cases we observe, standard methods like x-ray diffuse scattering (XRDS), atomic force microscopy (AFM) and optical interferometric microscopy (OIM) give notably different results in surface characterization. The goal of the attestation procedure is choosing the sample for sputtering a multilayer coating with better reflection properties, thats why its important to understand the physical causes of the difference and get reliable information about the surface. In this work we discuss the limitation for aforesaid standard methods. OIM is seems to be inapplicable for supersmooth surface investigation because of applying references. Its also shown, that examination substrates with damaged layers in the volume (caused, for example, by ion-beam etching) by XRDS can lead to incorrect results. Imaging systems are composed by nonplanar optical elements with radiuses from 10 mm to 1 meter. That makes impossible using hard x-rays and also limited AFM applicability to high frequencies. Therefore, we propose the diffuse scattering of soft x-rays as an alternative approach. We also describe a new reflectometer, based on soft x-ray and visible light diffuse scattering, which can be used for surface investigation in middle and high spatial frequency ranges for both plane or curved substrates.

Manufacturing and characterization of diffraction quality normal incidence optics for the XEUV range

Due to recent progress in short-period multilayer mirrors manufacturing, a real opportunity of nanoscale space resolution imaging in the XEUV range is appeared. Traditional manufacturing and surface shape characterization techniques do not meet the requirements. This paper reports on some new methods and technologies of measurement and surface shape correction, developed in IPM RAS. Last experimental results in manufacturing and surface shape studies of spherical and aspherical mirrors and objectives for X-ray optics are presented, as well as reflection characteristics of normal incidence multilayer mirrors made in IPM RAS. The advantages of using the multilayer optical elements for the diffraction quality imaging in comparing with Frenels zone plates are discussed. There are also proposed some new applications for multilayer-based reflecting optical elements.

Polished sitall substrates for X-ray optics

The parameters of the surface roughness of polished sitall substrates fabricated using a technique developed by the authors are reported. A comparison with the world analog, namely the Zerodur optical ceramic manufactured by Edmund Industrial Optics is performed. The effect of ion-beam etching on the surface roughness for both materials is studied.

Multilayer La/B4C mirrors in the spectral region near 6.7 nm

The results from measuring reflection factors are presented for multilayer La/B4/C mirrors with barrier layers of carbon and scandium. It is shown that a higher reflection factor is obtained by depositing a layer of carbon onto a surface of boron carbide. This effect is caused by diminishing absorption in the structure and the reduced width of transition regions.

SIMS depth profiling of Pd/B4C, Ni/C, and Cr/Sc multilayer metal structures using registration of cluster secondary ions: The problem of depth resolution enhancement

The possibility of minimizing matrix effects during the SIMS depth profiling of multilayer metal structures is investigated, based on the use of cluster secondary ions that include a combination of the element to be analyzed and sputtering cesium or oxygen ions. For Pd/B4C, Ni/C, and Cr/Sc structures, the use of cluster secondary ions enabled us to substantially enhance depth resolution up to 1–2 nm.

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.

Interference effect of increasing reflection coefficient of multilayered mirrors based on threefold periodic structures

A possibility of increasing the peak reflection coefficient of binary multilayered periodic structures in the soft X-ray range by inctroducing additional layers (fabrication of trinary mirrors) is discussed. The parameters of the materials at which trinary mirrors become more efficient as compared to traditional binary ones are found.