Metrological studies of the characteristics of multilayer surface coatings using synchrotron radiation

The investigations of multilayer surface nanostructures characteristics was performed with synchrotron radiation sources, characterized by an intensive, calculated continuum. It plays an important role in nanoelectronics metrological base. The main research were carried out at electron storage rings «Siberia-1» (Kurchatov Institute) and MLS (PTB, Berlin) with low electron energy, in a wide wavelength range, including visible range, AUV, VU, EUV and to exclude the X-ray radiation influence. The methods of the radiometers, photodiodes, filters and multilayer mirrors characteristics measurements are based on the synchrotron  radiation  absolute spectral characteristics and accelerated electrons number variation. The metrological investigations with synchrotron radiation was concentrated on:
– absolute spectral responsivety of silicon photodiodes with multilayer filters for integral radiometers applications;
– spectral transmittances of surface layers of photodiodes in the extreme ultraviolet region;
– spectral reflectance coefficient of superlattice.
The characteristics of photodiodes and filters on a synchrotron radiation source are measured using a monochromator and a reference detector. The use of a synchrotron radiation channel makes it possible to study the spectral transmittance of thin films and multilayer structures formed in the in situ mode. To form multilayer nanostructures directly on the receiving surface of photodetectors, an ion-plasma sputtering module is used. The optical scheme of the channel provides for the possibility of using monochromators of grazing incidence for the range of photon energies from 25 to 100 ev and normal incidence for the range of photon energies from 4 to 25 ev. At a photon energy of 40 ev, the absolute spectral sensitivity was 70 ma / W for a photodiode with a surface multilayer filter applied. To develop an experimental technique for measuring the spectral reflection coefficient of multilayer mirrors, and to create standard samples, the Mo/Si  system was studied. Computer modeling of multi-layer coatings allows us to calculate the optical characteristics of superlattices in the extreme ultraviolet region. The obtained results of measurements of the spectral reflection coefficient of a multilayer coating in the photon energy range of 65–100 ev indicate a resonance reflection character with a max-imum at an energy of 83.5 ev and an energy width at a half-height of about 6.5 ev. The working wave-length of the reflecting mirror corresponds to the calculated one, which confirms the effectiveness of the adopted model.

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