Reflektives optisches Element und Verfahren zu seiner Herstellung/ Method to enhance layer contrast of a multilayer for reflection at the B absorption edge

Lithography applications beyond EUVL are expected to use 6.72 nm radiation. In this spectral region no transparent materials exist, therefore mirrors have to be used as optical elements. Spacer materials of interest in reflective optics for λ > 6.65 nm are B and B4C. Simulations show that La is a suited refractive material, because of its relatively low absorbtion and high optical contrast with B and B4C

Nanometer interface and materials control for multilayer EUV-optical applications

An overview is given of the progress in thin film and surface physics involved in multilayered systems with nanometer scale periodicity. When properly engineered, these enable the synthesis of reflective optics for the Extreme UV wavelength range. Design, deposition, and analysis of these structures have been driven by the demanding application of Extreme UV photolithography. This review addresses the selection of the wavelength in relation to the optical constants of materials, the layer growth mechanisms and ways to reduce layer roughness and interlayer formation. Special attention is given to the development of thin diffusion barrier layers between the materials in the multilayers to enhance the optical contrast and to reduce the interdiffusion. Practical issues like reduction of multilayer induced stress and enlargement of the reflectance bandwidth are also discussed, as well as the development of capping layers to control surface physics processes occurring under EUV irradiation. A description of the multilayer deposition techniques is given and the deposition of multilayers on large, heavily curved optics for real lithography systems is discussed. (C) 2011 Elsevier Ltd. All rights reserved

Nanometer interface and materials control for multilayer EUV-optical applications

An overview is given of the progress in thin film and surface physics involved in multilayered systems with nanometer scale periodicity. When properly engineered, these enable the synthesis of reflective optics for the Extreme UV wavelength range. Design, deposition, and analysis of these structures have been driven by the demanding application of Extreme UV photolithography. This review addresses the selection of the wavelength in relation to the optical constants of materials, the layer growth mechanisms and ways to reduce layer roughness and interlayer formation. Special attention is given to the development of thin diffusion barrier layers between the materials in the multilayers to enhance the optical contrast and to reduce the interdiffusion. Practical issues like reduction of multilayer induced stress and enlargement of the reflectance bandwidth are also discussed, as well as the development of capping layers to control surface physics processes occurring under EUV irradiation. A description of the multilayer deposition techniques is given and the deposition of multilayers on large, heavily curved optics for real lithography systems is discussed. (C) 2011 Elsevier Ltd. All rights reserved.</p

Atomic O and H exposure of C-covered and oxidized d-metal surfaces

Carbon coverage, oxidation and reduction of Au, Pt, Pd, Rh, Cu, Ru, Ni and Co layers of 1.5 nm thickness on Mo have been characterized with ARPES and desorption spectroscopy upon exposure to thermal H and O radicals. We observe that only part of the carbon species is chemically eroded by atomic H exposure, yielding hydrocarbon desorption. Exposure to atomic O yields complete carbon erosion and CO2 and H2O desorption. A dramatic increase in metallic and non-metallic oxide is observed for especially Ni and Co surfaces, while for Au and Cu, the sub-surface Mo layer is much more oxidized. Although volatile oxides exist for some of the d-metals, there is no indication of d-metal erosion. Subsequent atomic H exposure reduces the clean oxides to a metallic state under desorption of H2O. Due to its adequacy, we propose the atomic oxygen and subsequent atomic hydrogen sequence as a candidate for contamination removal in practical applications like photolithography at 13.5 nm radiation

Reflective multilayer optics for 6.7 nm wavelength radiation sources and next generation lithography

Reported is a computational and chemical analysis of near normal incidence reflective multilayer optics for 6.7 nm wavelength applications in e.g. the Free Electron Laser FLASH and next generations of EUV lithography. We model that combinations of B or B4C with La offer a reflectivity of ~ 70%. The small reflectivity bandwidth poses problems in applications, but it can be significantly improved by replacing La with Th or U. Grazing incidence X-ray reflectometry, cross-section TEM, and in-depth XPS analysis of B/La and B4C/La multilayers reveal chemical reactivity at the interfaces. Significant LaBx interlayer formation is observed in especially B/La multilayers, stressing the relevance of interface passivation. We propose nitridation of the interfaces, which mitigates interlayer formation and simultaneously increases optical contrast