Structure and performance of Si/Mo multilayer mirrors for the extreme ultraviolet

Abstract

We report the results of structural, chemical, and extreme ultraviolet (EUV) characterization of Si/Mo multilayers grown by sputtering and by UHV evaporation. This study includes mirrors designed for normal incidence with peak reflectivities Rpeak between 22 and 24 nm, and 45° mirrors having Rpeak between 16 and 19 nm. The deposition conditions were varied to produce multilayers with a wide range of interface morphologies. A variety of techniques were used to determine the structure and composition of the multilayers, including x-ray diffraction, transmission electron microscopy, Rutherford backscattering spectroscopy, and Auger depth profiling. All of the mirrors have amorphous Si layers and polycrystalline Mo layers with thin amorphous alloy interlayers. We obtain good fits to the low-angle x-ray diffraction data only when these interlayers are taken into account. The best sputter-deposited mirrors were made at the lowest Ar pressure studied, 3 mTorr. The best evaporated mirrors were produced at a substrate temperature of 200 °C. The EUV reflectivity as a function of wavelength was measured using synchrotron radiation. Both the multilayer structure and surface contamination significantly affect the EUV reflectivity, and must be considered to obtain good fits to the reflectivity curves. The best 45° mirror had a peak reflectivity of 53% at 18.6 nm for 100% S-polarized light, and the best normal-incidence mirror had a peak reflectivity of 33% at 23.6 nm.

Analysis of periodic Mo/Si multilayers: Influence of the Mo thickness

“…This is well established for this system [22][23][24]. As a function of the thickness of the Mo layers, we observe no relevant change of the thickness, roughness and composition of the interlayers (Cf.…”

Multilayer optics for XUV spectral region: technology fabrication and applications

“…The values of the transition layers as measured on the TEM images are º 0.3 nm and º 0.7 nm, respectively. This e®ect and the most likely mechanism behind such an asymmetry were discussed by several research groups in detail [32,36,[38][39][40][51][52][53][54]. The qualitative analysis of the experimental data and the results of numerical simulation of the deposition processes show that, most likely, the intermediate layer asymmetry stems from the di®erence in the conditions at very early stages of formation of continuous¯lms on the amorphous surface of silicon and on the surface of molybdenum crystals [38,54].…”

“…The Mo/Si system has been actively investigated by various groups in the last two decades [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43], due to the fact that a combination of these materials, besides being actively used in X-ray optics, is of considerable interest for semiconductor applications as well [30,31,37]. These groups studied the Mo/Si morphology in a variety of experimental techniques including small angle X-ray di®ractometry, transmission electron microscopy (TEM), Auger electron spectroscopy, Rutherford backscattering etc., thus providing an explanation of the dependence of structural changes on deposition parameters.…”

The wet corrosion of molybdenum thin film – Part III: The effect of Ti and Nb

“…As presented previously [1,2], molybdenum is a potential material for many thin film applications in different fields such as protective coatings of nuclear materials [3], solar cells [4], back contact in thin film solar cells [5,6] and microelectronics [7]. All these applications are due to the physical chemistry properties of Mo.…”