Extreme ultraviolet reflectometry for structural and optical characterization of thin films and layer systems

The aim of this work is to explore the capabilities of extreme ultraviolet reflectometry (EUVR) as a metrology method for determination of layer parameters (such as thickness, density, roughness, chemical composition) in application to industry-relevant high-k semiconductor films. As a short-wavelength photon-in/photon-out technique, spectral EUVR allows for non-destructive characterization of layer systems at the sub-nanometer scale. A special focus of the study is put on the near-edge spectral region, considering the advantage of high chemical contrast that it provides. Adding the angular dimension to the analyzed reflectivity dataset places additional constraints on the layer model, improving quality of the structural reconstruction and opening a possibility of the complex refractive index determination. A modification of a laboratory polychromatic EUVR setup that enables multi-angle (2°-15°) spectrally broadband (9.5-17 nm) grazing incidence reflectance measurements is presented. The capabilities of the tool are initially tested on a set of thin (1-9 nm) HfO2 films on Si substrates. Further studies are performed on a non-uniform sample contamination layer in spatially resolved reflectivity mapping mode, showing the potential of the technique for local characterization of surfaces. The presence of amorphous Al2O3 in the contamination layer is confirmed by the near-edge fine structure analysis. In addition, spatial resolution extendibility study is performed. With minor alterations to the sample illumination scheme, an EUV spot size of 25 x 30 μm (FWHM) is experimentally achieved. Another major topic of the present thesis is optical and structural characterization of LaLuO3 (LLO) films, a promising high- candidate for future MOSFET technology. EUV reflectivity is experimentally obtained for amorphous, orthorhombic, cubic and hexagonal LLO modifications in the range of 70-200 eV (6.2-17.7 nm)at 5°, 12° and 20° angle of incidence using synchrotron radiation. Previously unreported La absorption edge features are observed. After extending the angular range of the measurement to 2°-50°, the optical constants of amorphous and orthorhombic LLO films are determined, along with the corresponding layer structure parameters. From the near-edge optical constant analysis, La:Lu stoichiometry ratio and the film density are derived. Compared to X-ray reflectance, EUVR method shows a higher sensitivity to sample contamination, substrate oxidation and strain effects. Correlation analysis of the fit parameters for the EUVR and XRR results indicates that both methods allow for precise determination of the layer structure, also highlighting a superior chemical contrast of the EUVR measurements. In attempt to optimize the EUVR data acquisition process, it is found that angle-resolved approach presents the greatest potential for the EUVR method, allowing for in-depth probing and more precise reconstruction of layer structures. The measurement wavelength in this case may be selected to provide the best chemical contrast, according to the studied material

Spatially Resolved Spectroscopic Extreme Ultraviolet Reflectometry for Laboratory Applications

International audienceSpatially resolved extreme ultraviolet reflectometry is presented in application to a local characterization of thin non-uniform contamination layers. Sample reflectivity mapping is performed, demonstrating high chemical sensitivity of the technique. Amorphous Al 2 O 3 and carbon are determined as the contaminants of the studied silicon wafer. The results correlate with those obtained by energy-filtering photoemission electron microscopy. A laboratory tool is developed that is capable of multi-angle (2-15) and spectrally broadband (9.5-17 nm) extreme ultraviolet reflectometry at grazing incidence combined with a reduced sample illumination spot size, enabling spatially resolved metrology. A minimum EUV spot size of 25 × 30 m in the sample plane is achieved experimentally

Multi-angle spectroscopic extreme ultraviolet reflectometry for analysis of thin films and interfaces

Modern nanotechnology is constantly raising demands to quality and purity of thin films and interlayer interfaces. As thicknesses of employed layers decrease to single nanometers, traditional characterization tools are no longer able to satisfy throughput, precision or non-destructibility requirements. Extreme ultraviolet (EUV) and soft X-ray reflectometry has not only demonstrated the ability to detect sub-nm thickness variations but also was shown to be very sensitive to chemical composition changes. Since the laboratory radiation sources in this wavelength range often emit in a relatively broad spectral range, a spectroscopic EUV reflectometry has been developed with the added benefit of a rapid measuring time on the order of milliseconds to seconds. In this paper, the extension of the method to multi-angle measurements will be presented. It allows to reduce a number of fit parameters in the analysis model, making the method suitable for complex samples of unknown composition. First experimental examples for Si-based layer systems measured under grazing incidence angles between 2° and 15° will be demonstrated and discussed. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Optical and structural characterization of orthorhombic LaLuO3 using extreme ultraviolet reflectometry

A thin orthorhombic LaLuO3 film, grown on SrTiO3 substrate by pulsed laser deposition, is characterized using multi-angle spectral extreme ultraviolet reflectometry (EUVR). Layer structure parameters and optical constants of LaLuO3 are determined simultaneously by fitting angular reflectivity curves in a wide spectral range (70–200 eV). From near-edge optical constant analysis, La:Lu stoichiometry ratio and the film density are derived. Sample structure is additionally analyzed using XRR, AFM and TEM methods. EUVR as a method of structural characterization is discussed in comparison with XRR. Correlation error analysis of the layer structure parameters, obtained from independent EUVR and XRR fits, is presented

Automation of Target Delivery and Diagnostic Systems for High Repetition Rate Laser-Plasma Acceleration

Fast solid target delivery and plasma-ion detection systems have been designed and developed to be used in high intensity laser-matter interaction experiments. We report on recent progress in the development and testing of automated systems to refresh solid targets at a high repetition rate during high peak power laser operation (>1 Hz), along with ion diagnostics and corresponding data collection and real-time analysis methods implemented for future use in a plasma-based ion acceleration beamline for multidisciplinary user applications

The ELIMAIA Laser–Plasma Ion Accelerator: technological commissioning and perspectives

We report on the technological commissioning of the Laser–Plasma Ion Accelerator section of the ELIMAIA user beamline at the ELI Beamlines facility in the Czech Republic. The high-peak, high-average power L3-HAPLS laser system was used with an energy of ~10 J and pulse duration of ~30 fs on target, both in single-pulse and high repetition-rate (~0.5 Hz) mode. The laser pulse was tightly focused to reach ultrahigh intensity on target (~1021 W/cm2) and sustain such laser–plasma interaction regime during high repetition-rate operations. The laser beam, ion beam, and laser–plasma emission were monitored on a shot-to-shot basis, and online data analysis at 0.5 Hz was demonstrated through the full set of used diagnostics (e.g., far and near field, laser temporal diagnostics, X- and gamma-ray detectors, Thomson Parabola ion spectrometer, time-of-flight ion detectors, plasma imaging, etc.). The capability and reliability of the ELIMAIA Ion Accelerator was successfully demonstrated at a repetition rate of 0.5 Hz for several hundreds of consecutive laser shots