189 research outputs found
Alternative EUV absorptive materials and novel architectures for EUV reticle in nm node technology scanner
Get PDFThe 3D effects of typical EUVL masks worsen at higher numerical aperture of the imaging optics employed in EUVL scanners. Therefore, the height of the EUV absorber layer of the reticle for 7nm node technology scanners necessarily should be reduced to the order of 30nm, as compared to current Ta-based absorber heights which are around 50nm. Such a reduction of the absorber height requires higher absorption per unit height or, more specifically, a higher absorption coefficient. In this regard, the implementation of high EUV absorptive materials such as nickel and silver were suggested. Nickel and silver grow polycrystalline which can be disadvantageous in terms of the etching process used. Moreover, silver grows on ruthenium such that the surface roughness is significantly unacceptable in terms of the surface roughness requirement for the absorber layer of the reticle. As a result of these practical restrictions, two different designs were suggested to overcome the practical issues; doping a nickel thin film with boron to suppress the crystallization and a silver-germanium multilayer to suppress the crystallization and reduce the surface roughness of the silver. The validations represented in section 7 showed both designs successfully overcame the corresponding practical issues. Next, according to suggested designs, full-size reticles must be fabricated to undergo further analyses by other stakeholders, such as imaging tests, patterning, cleaning, and repair in order to provide further input to optimize and validate final EUV absorber layers for 7nm node technology reticles
Determining crystal phase purity in c-BP through X-ray absorption spectroscopy
Get PDFCitation: Determining crystal phase purity in c-BP through X-ray absorption spectroscopy. S. P. Huber, V. V. Medvedev, E. Gullikson, B. Padavala, J. H. Edgar, R. W. E. van de Kruijs, F. Bijkerk, and D. Prendergast. Phys. Chem. Chem. Phys. 19 8174--8187 (2017) 10.1039/c6cp06967cWe employ X-ray absorption near-edge spectroscopy at the boron K-edge and the phosphorus L2,3-edge to study the structural properties of cubic boron phosphide (c-BP) samples. The X-ray absorption spectra are modeled from first-principles within the density functional theory framework using the excited electron core-hole (XCH) approach. A simple structural model of a perfect c-BP crystal accurately reproduces the P L2,3-edge, however it fails to describe the broad and gradual onset of the B K-edge. Simulations of the spectroscopic signatures in boron 1s excitations of intrinsic point defects and the hexagonal BP crystal phase show that these additions to the structural model cannot reproduce the broad pre-edge of the experimental spectrum. Calculated formation enthalpies show that, during the growth of c-BP, it is possible that amorphous boron phases can be grown in conjunction with the desired boron phosphide crystalline phase. In combination with experimental and theoretically obtained X-ray absorption spectra of an amorphous boron structure, which have a similar broad absorption onset in the B K-edge spectrum as the cubic boron phosphide samples, we provide evidence for the presence of amorphous boron clusters in the synthesized c-BP samples
Detection of defect populations in superhard semiconductor boron subphosphide B12P2 through X-ray absorption spectroscopy
Get PDFCitation: Detection of defect populations in superhard semiconductor boron subphosphide B12P2 through X-ray absorption spectroscopy. S. P. Huber, E. Gullikson, J. Meyer-Ilse, C. D. Frye, J. H. Edgar, R. W. E. van de Kruijs, F. Bijkerk, and D. Prendergast J. Mater. Chem. A 5 5737--5749 (2017) 10.1039/c6ta10935gRecent theoretical work has shown for the first time how the experimentally observed property of “self-healing” of the superhard semiconductor boron subphosphide (B12P2) arises through a process of mediated defect recombination. Experimental verification of the proposed mechanism would require a method that can detect and distinguish between the various defect populations that can exist in B12P2. X-ray absorption near-edge spectroscopy (XANES) is such a method and in this work we present experimentally collected spectra of B12P2samples with varying crystalline qualities. By simulating the X-ray spectroscopic signatures of potential crystallographic point defects from first-principles within the density functional theory framework, the presence of defect populations can be determined through spectroscopic fingerprinting. Our results find an increasing propensity for the presence of phosphorus vacancy defects in samples deposited at lower temperatures but no evidence for comparable populations of boron vacancies in all the samples that have been studied. The absence of large amounts of boron vacancies is in line with the “self-healing” property of B12P2
Growth and thermal oxidation of Ru and ZrO2 thin films as oxidation protective layers
Get PDFThis thesis focuses on the study of physical and chemical processes occurring during growth and thermal oxidation of Ru and ZrO2 thin films. Acting as oxidation resistant capping materials to prevent oxidation of layers underneath, these films have several applications, i.e., in microelectronics such as gate dielectrics or memory devices, in photovoltaics, or in extreme ultraviolet lithography (EUVL) optics. High-sensitivity low-energy ion scattering (HS-LEIS) has been used in this thesis for in vacuo analysis of the initial growth stages of Ru and ZrO2 films on a-Si, SiN and SiO2 substrate layers, including an accurate determination of surface coverages and thicknesses required for closing the growing film. During ZrO2 growth, the oxygen concentration (high-O and low-O conditions) in the sputter gas was varied in order to study its effect on ZrO2 growth and its properties (e.g., stoichiometry, interaction with the underlying layer, mass density). The oxidation and/or oxygen diffusion behavior of Ru and ZrO2 films upon thermal annealing under atmospheric oxygen have been investigated. In the case of Ru, a detailed description of surface and sub-surface oxidation of Ru thin films has been presented, and a model for concurrent 2D and 3D ruthenium oxide growth has been proposed. It also was found that the 2D oxide did not grow as a single layer but a combination of two layers on top of each other, a low density RuOx (2<x≤3) layer on top of a near bulk density RuO2 layer. In situ XRR measurements during annealing have been used to determine diffusion rates and activation energies for oxygen diffusion through RuO2 thin films. Diffusion rates were found not to be constant, and to decrease with growing RuO2 thickness, while the activation energy increased. In the case of ZrO2, oxygen diffusion through low-O ZrO2 films on a-Si has been investigated by ex situ angular resolved X-ray photoelectron spectroscopy (AR-XPS) of thermally oxidized samples. For temperatures below 400°C, no additional oxidation of the underlying a-Si was observed. Based on this positive result, ZrO2 might be considered as a promising protective layer for applications where an a-Si film should be protected against oxidation
Fracture behavior and characterization of free-standing metal silicide thin films
Get PDFThe research presented in this thesis concerns brittle fracture of free-standing nanoscale thin films, specifically transition metal silicide films which have found use in EUV pellicles. Ensuring the reliability of thin film EUV pellicles requires an understanding of the mechanical properties of the thin film material, which can significantly differ from the properties of its bulk counterpart due to scale effects and differences in the microstructure. The first half of the work aims to deepen the understanding of the link between composition, structure, and fracture strength in transition metal silicide thin films. With this goal, an experimental investigation was carried out using a combination of mechanical characterization techniques, membrane bulge test and tensile testing, with X-ray diffraction and transmission electron microscopy. The second half of the work moves its focus from fracture strength toward another important mechanical property – resistance to crack propagation, or fracture toughness. The recently developed crack-on-a-chip test method was successfully adapted for metal silicide thin films to determine their fracture toughness. Furthermore, several improvements have been made to the method, such as the addition of on-chip drawbridge-like actuators and taking into account the effect of buckling in the analysis, which enable a more detailed and accurate characterization of the fracture process
Self-healing in B12P2 through Mediated Defect Recombination
Get PDFCitation: Self-healing in B12P2 through Mediated Defect Recombination. S. P. Huber, E. Gullikson, C. D. Frye, J. H. Edgar, R. W. E. van de Kruijs, F. Bijkerk, and D. Prendergast. Chemistry of Materials 28 8415--8428 (2016) 10.1021/acs.chemmater.6b04075The icosahedral boride B12P2 has been reported to exhibit “self-healing” properties, after transmission electron microscopy recordings of sample surfaces, which were exposed to highly energetic particle beams, revealed little to no damage. In this work, employing calculations from first-principles within the density functional theory (DFT) framework, the structural characteristics of boron interstitial and vacancy defects in B12P2 are investigated. Using nudged elastic band simulations, the diffusion properties of interstitial and vacancy defects and their combination, in the form of Frenkel defect pairs, are studied. We find that boron icosahedra maintain their structural integrity even when in a degraded state in the presence of a vacancy or interstitial defect and that the diffusion activation energy for the recombination of an interstitial vacany pair can be as low as 3 meV, in line with the previously reported observation of “self-healing”
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