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Surface Study in Extreme UV Range

#2297


Development of Methods and Equipment for Surface and Thin Film Study in EUV Spectral Region

Tech Area / Field

  • INS-MEA/Measuring Instruments/Instrumentation
  • PHY-OPL/Optics and Lasers/Physics
  • PHY-SSP/Solid State Physics/Physics

Status
8 Project completed

Registration date
29.08.2001

Completion date
19.06.2008

Senior Project Manager
Lapidus O V

Leading Institute
VNIITF, Russia, Chelyabinsk reg., Snezhinsk

Supporting institutes

  • FIAN Lebedev / Quantum Radiophysics Department of the Lebedev Physical Institute of Russian Academy of Sciences, Russia, Moscow

Collaborators

  • Five Lab Co.,LTD, Japan, Kanagawa\nNational Institute of Advanced Industrial Science and Technology (AIST), Japan, Tsukuba\nJAERI/Advanced Photon Center, Kansaj Establishment, Japan, Kyoto

Project summary

During execution of the previous ISTC Project, #1051-99, we developed experimental techniques and theoretical approaches to the investigation of the microtopography of flat and figured surfaces, thin films and interfaces, based mainly on the study of reflection and scattering of the hard x-rays (0.15nm), while a number of experiments were performed in the soft x-ray (SXR) spectral region (4-7nm). The works were performed in a close collaboration with the foreign partners and aroused considerable interest among many Russian and foreign scientists. The main results of the project were presented in 11 research papers, 13 talks and posters at 6 International Conferences, including 9 papers and 8 conference reports, prepared together with the foreign project collaborators.

During execution of this earlier project we demonstrated that the EUV radiation of the longer wavelength (10-30nm) has specific advantages for the surface and interface structure study as compared with the radiation of another wavelength. Among these advantages we should note the following:
EUV scattering permits the extraction of information about the surface and interface roughness on the basis of the perturbation theory, applied to analysis of scattering through any angle. Note that the perturbation theory makes it possible to extract information about the roughness properties by just a unique and simple manner and it does not require, in contrast, for example, to the approach based on Distorted Wave Born Approximation, the use of additional model assumptions about the cross-correlation function.
EUV radiation allows one to study the surface roughness at a spatial frequency up to 100, which coincides with the upper frequency limit of AFM measurements and, in contrast to AFM, permits the study of latent interfaces and subsurface layers.
The EUV radiation proves to have the highest sensitivity in respect of the presence of various oxidized, adhered and adsorbed layers placed at a surface and enables the detection of a near surface layer, several angstrom thick (one monolayer), without a problem.
Current multilayer mirrors have the highest reflectivity just in the EUV regions, they permit the creation of a polarized beam and analysis of the reflected radiation polarization, hence, the performance of ellipsometric measurements in the EUV spectral region. EUV ellipsometry has a much higher sensitivity in comparison with EUV reflectometry.
Nowadays, rare-earth elements and their compounds and alloys are widely used in many fields of science and technology. In particular, they are applied as effective catalysts, luminophors, and magnetic materials. Intensive 4d-4f spectral lines of rare-earth elements lie just in the EUV spectral range. This circumstance causes very high sensitivity to the presence of rare-earth atoms in a sample of the reflection spectrum measured with the use of EUV radiation and this facilitates precise structure investigations of rare-earth elements and nanostructures containing these elements.

The use of EUV radiation to study surfaces and materials requires the availability of a highly intensive, compact radiation source, which can be installed in any laboratory and is specially adapted for metrological measurements. At present, similar investigations are performed with the use, as a rule, of synchrotron sources, i.e. they are very expensive and cannot be considered as a prompt testing method.

Therefore, the goal of the present Project is to develop and construct a table-top high-power source of EUV radiation, measurement techniques and methods, theoretical basis and computer software for the study of supersmooth surfaces, thin films, and multilayer structures, and the near-surface and near-interface layers (oxidized, adhered, diffusive, implanted, broken, etc.), based on reflection and scattering measurements in the EUV spectral regions.

Within the course of the implementation of this project, the following will be developed and produced:
Table-top high-power source of EUV radiation based on gas micropinch discharge of high frequency operation (100Hz). The total power of EUV radiation is 0.2W in the narrow spectral band, centered at about 13nm wavelength; the total weight of the source is less than 100kg.
Improved diagnostic and technological chamber including high-vacuum oil-free pumping system, thermal cleaning of the sample surface, electron-beam and thermal deposition of materials onto the substrate, a system of automatic control of the measurements and data procession
Theoretical basis, methods and techniques for reflectivity and scattering measurements in the EUV range.
Adequate computer software.
Technical documentation containing a description of the source and user's instructions.

The following tasks will be solved during the Project execution:
Numerical and theoretical study of the radiation characteristics of the gas micropinch aimed at optimization of the gas load parameters.
Development and installation of the pulsed frequency generator of nanosecond current pulses.
Development of the discharge chamber and a search for micropinch discharge conditions, which correspond to the maximum radiation output.
Improvement of high-vacuum pump system.
Development and construction of a system of heat cleaning of samples and deposition of the materials placed inside the measurement chamber for performing in situ and post-deposition measurements directly in a vacuum.
Software for automation of experiments.
The study of the roughness of surfaces, thin films, and multilayer structures, based on measurements of EUV scattering diagrams.
In situ investigations of the roughness and optical constants of growing films in the EUV spectral region. Development of a model of film and multilayer structure growth.
Investigations of near surface oxide and adhered layers and the fine structure of interfaces, based on comparative analysis of reflectivity measurements in EUV and hard x-ray spectral regions, performed in post-deposition state in vacuum and in air. Development of theoretical approaches to solution of the inverse problem of reflectometry.
Precise measurements of reflectivity and scattering from multilayer mirrors at normal incidence in EUV and soft x-ray spectral regions. Further development of the theory of interaction of EUV and soft x-ray radiation with a rough multilayer structure.
Precise physical and structural investigations of rare-earth elements and nanostructures, which contain these elements, using EUV reflectometry. Determination of the optical constants of rare-earth materials and their compounds in the EUV spectral range.

EUV facility, experimental techniques, and computer software, developed within the framework of the present project, will find applications as the metrological basis in many problems of microelectronics, optics, EUV and soft x-ray optics, material science and high-precision micromachine engineering.

The role of the foreign project collaborators:
Joint investigations of the surface and interface roughness using different methods: EUV and X-ray scattering, UV and visible light scattering, atomic force microscopy, and so on. Comparison of the results obtained by different methods.
Joint investigations of the microtopography and microstructure of different samples (supersmooth surfaces, thin films, multilayer structures) fabricated by the foreign collaborators, bearing in mind the further improvement of current fabrication technology.

The Project participants are specialists in plasma physics, X-ray and EUV radiation diagnostics, X-ray technology and optics, and the application of X-ray methods in surface and solid-state physics. More than 200 research papers have been prepared on the above fields of physics, and the papers are well known and widely cited.

During work on Project execution the main objectives of the ISTC are realized: specialists previously engaged in the development, testing and transport of nuclear weapons, and those engaged in weapons research at powerful laser facilities, will be engaged in civil activity. The efforts of the researchers will be concentrated on the development of new-generation analytical methods and the facility, intended for wide application in many fields of science, technology and industry connected with both the study of surface properties, transition layers, thin films, and the manufacture of supersmooth surfaces. Emphasis in the design will be placed on future commercial applications because such a facility is necessary both for scientific research and industrial applications. Specialists engaged in work on the Project will work in close cooperation with foreign collaborators and scientists from the Russian Academy of Sciences who have close contacts with the international scientific community.


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