Now showing 1 - 2 of 2
  • Publication
    Angle-resolved studies of tin laser plasma extreme ultraviolet sources
    (University College Dublin. School of Physics, 2008)
    The work presented in this thesis is primarily concerned with the radiation and ions emitted by laser produced plasmas (LPPs) containing tin. If the semiconductor manufacturing industry is to meet Moore’s law (a doubling in the number of transistors per square inch on integrated circuits every two years), new lithographic techniques are required. EUV lithography (EUVL) shows the most promise, requiring a bright source of radiation in the 2% band centered at 13.5 nm, known as in-band radiation. This is due to the high reflectivity of molybdenum/silicon multilayer mirrors at these wavelengths. Tin-based LPPs have been shown to emit strongly in the in-band region. Chapter 2 presents a unique optical system with the ability to present a range of observing angles to a fixed detector, while maintaining normal incidence for the laser onto a planar solid target. This allows the system to be rotated, with respect to a fixed detector, while maintaining spatially stable plasma formation. Chapter 3 presents absolute intensity measurements of in-band radiation, emitted from pure tin laser produced plasmas, for a range of angles. Also measured is the angular distribution of intensities from 10 to 18 nm. Light, from outside the 2% band at 13.5 nm in this region, will result in flare at the resist in extreme ultraviolet lithography, thus limiting the feature resolution attainable. Two of the main problems facing next generation lithography are thermal and debris mitigation. Sn-based LPPs are highly emissive in the region of 100 to 3000 nm, where the multilayer optics can be highly reflective. This out-of-band (OOB) radiation can cause flare, heat the wafer and create overlay issues. It is necessary to quantify the levels of OOB radiation, over a range of wavelength regions, to facilitate the development of suitable optical components that will reduce the OOB radiation at the wafer plane to acceptable levels. Chapter 4 presents the angular distributions of OOB radiation for a range of wavelength regions between 200 and 1000 nm. Also, ions that are emitted from these LPPs may cause significant damage to the components in a real world projection lithography system. Fast ions, impinging on multilayer optics, can lead to the sputtering of mirror layers and debris deposited on multilayer optics and can degrade in-band reflectivity. In order to effectively mitigate this damage it is necessary to know the speed and direction of the emitted ions. The angular distribution of the total number of ions, from Sn1+ to Sn9+, emitted from a Snbased LPP, is investigated in Chapter 5. The charge state, energy and relative number of these ions have also been determined. In order to facilitate comparison between EUV, OOB and ion data in chapters 3, 4 and 5, the measurements in these chapters were performed at approximately equal plasma conditions. This comparison is explored and detailed in Chapter 6.
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  • Publication
    Configuration Interaction in Charge Exchange Spectra of Tin and Xenon
    Charge state specific extreme ultraviolet spectra from both tin ions and xenon ions have been recorded at Tokyo Metropolitan University. The Electron Cyclotron Resonance Source spectra were produced from charge exchange collisions between the ions and rare gas target atoms. In order to identify unknown spectral lines of tin and xenon, atomic structure calculations were performed for Sn14+ - Sn17+ and for Xe 16+ - Xe20+ using the Hartree-Fock with Configuration Interaction code of Cowan. The energies of the capture states involved in the single electron process that occurs in these slow collisions are estimated using the classical over barrier model.
      812Scopus© Citations 3