Bulletin of the American Physical Society
55th Annual Meeting of the APS Division of Plasma Physics
Volume 58, Number 16
Monday–Friday, November 11–15, 2013; Denver, Colorado
Session VI3: Technology Applications of Plasmas and Charged Particle Beams |
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Chair: J. Gary Eden, University of Illinois Room: Plaza F |
Thursday, November 14, 2013 3:00PM - 3:30PM |
VI3.00001: Novel multi-beam X-ray source for vacuum electronics enabled medical imaging applications Invited Speaker: V. Bogdan Neculaes For almost 100 of years, commercial medical X-ray applications have relied heavily on X-ray tube architectures based on the vacuum electronics design developed by William Coolidge at the beginning of the twentieth century. Typically, the Coolidge design employs one hot tungsten filament as the electron source; the output of the tube is one X-ray beam. This X-ray source architecture is the state of the art in today's commercial medical imaging applications, such as Computed Tomography. Recently, GE Global Research has demonstrated the most dramatic extension of the Coolidge vacuum tube design for Computed Tomography (CT) in almost a century: a multi-beam X-ray source containing thirty two cathodes emitting up to 1000 mA, in a cathode grounded -- anode at potential architecture (anode up to 140 kV) [1,2]. This talk will present the challenges of the X-ray multi-beam vacuum source design -- space charge electron gun design, beam focusing to compression ratios needed in CT medical imaging applications (image resolution is critically dependent on how well the electron beam is focused in vacuum X-ray tubes), electron emitter choice to fit the aggressive beam current requirements, novel electronics for beam control and focusing, high voltage and vacuum solutions, as well as vacuum chamber design to sustain the considerable G forces typically encountered on a CT gantry (an X-ray vacuum tube typically rotates on the CT gantry at less than 0.5 s per revolution). Consideration will be given to various electron emitter technologies available for this application -- tungsten emitters, dispenser cathodes and carbon nano tubes (CNT) [3, 4] -- and their tradeoffs. The medical benefits potentially enabled by this unique vacuum multi-beam X-ray source are:~ X-ray dose reduction, reduction of image artifacts and improved image resolution.~\\[4pt] [1] ``An outlook on X-ray CT research and development,'' G. Wang. H. Yu and B. De Man, Med. Phys. 35 (3), March 2008\\[0pt] [2] ``High power distributed X-ray source,'' K. Frutschy, B. Neculaes, L. Inzinna, A. Caiafa, J. Reynolds, Y. Zou, X. Zhang, S. Gunturi, Y. Cao, B. Waters, D. Wagner, B. De Man, D. McDevitt, R. Roffers, B. Lounsberry, N. Pelc, Proceedings of SPIE, vol. 7622 76221H-1, 2010\\[0pt] [3] ``Analytical study of electron gun temporal current response as a function of electron emission mechanism,'' V. B. Neculaes, A. Caiafa and Y. Zou, 21$^{\mathrm{st}}$ International Vacuum Nanoelectronics Conference Technical Digest, p. 94, ISBN : 83-914886-2-4, 2008 \\[0pt] [4] ``Role of plasma activation in kinetics of carbon nanotube growth in plasma-enhanced chemical vapor deposition,'' I.V. Lebedeva, A. A. Knizhnik, A.V. Gavrikov, A. E. Baranov, B. V. Potapkin, D. J. Smith, and T.J. Sommerer. Journal of App. Phys., 111, 074307, 2012 [Preview Abstract] |
Thursday, November 14, 2013 3:30PM - 4:00PM |
VI3.00002: Gas-Liquid Interfacial Non-Equilibrium Plasmas for Structure Controlled Nanoparticles Invited Speaker: Toshiro Kaneko Plasmas generated in liquid or in contact with liquid have attracted much attention as a novel reactive field in the nano-bio material creation because the brand-new chemical and biological reactions are yielded at the gas-liquid interface, which are induced by the physical actions of the non-equilibrium plasmas. In this study, first, size- and structure-controlled gold nanoparticles (AuNPs) covered with DNA are synthesized using a pulse-driven gas-liquid interfacial discharge plasma (GLIDP) for the application to next-generation drug delivery systems. The size and assembly of the AuNPs are found to be easily controlled by changing the plasma parameters and DNA concentration in the liquid. On the other hand, the mono-dispersed, small-sized, and interval-controlled AuNPs are synthesized by using the carbon nanotubes (CNTs) as a template, where the CNTs are functionalized by the ion and radical irradiation in non-equilibrium plasmas [1]. These new materials are now widely applied to the solar cell, optical devices, and so on. Second, highly-ordered periodic structures of the AuNPs are formed by transcribing the periodic plasma structure to the surface of the liquid, where the spatially selective synthesis of the AuNPs is realized. This phenomenon is well explained by the reduction and oxidation effects of the radicals which are generated by the non-equilibrium plasma irradiation to the liquid and resultant dissociation of the liquid [2]. In addition, it is attempted to form nano- or micro-scale periodic structures of the AuNPs based on the self-organizing behavior of turbulent plasmas generated by the nonlinear development of plasma fluctuations at the gas-liquid interface. \\[4pt] [1] T. Kaneko and R. Hatakeyama, Jpn. J. Appl. Phys. \textbf{51}, 11PJ03 (2012).\\[0pt] [2] T. Kaneko, S. Takahashi, and R. Hatakeyama, Plasma Phys. Control. Fusion \textbf{54}, 124027 (2012). [Preview Abstract] |
Thursday, November 14, 2013 4:00PM - 4:30PM |
VI3.00003: Advances in Plasma Process Equipment Development using Plasma and Electromagnetics Modeling Invited Speaker: Ankur Agarwal Plasma processing is widely used in the semiconductor industry for thin film etching and deposition, modification of near-surface material, and cleaning. In particular, the challenges for plasma etching have increased as the critical feature dimensions for advanced semiconductor devices have decreased to 20 nm and below. Critical scaling limitations are increasingly driving the transition to 3D solutions such as multi-gate MOSFETs and 3D NAND structures. These structures create significant challenges for dielectric and conductor etching, especially given the high aspect ratio (HAR) of the features. Plasma etching equipment must therefore be capable of exacting profile control across the entire wafer for feature aspect ratios up to 80:1, high throughput, and exceptionally high selectivity. The multiple challenges for advanced 3D structures are addressed by Applied Material's plasma etching chambers by providing highly sophisticated control of ion energy, wafer temperature and plasma chemistry. Given the costs associated with such complex designs and reduced development time-scales, much of these design innovations have been enabled by utilizing advanced computational plasma modeling tools. We have expended considerable effort to develop 3-dimensional coupled plasma and electromagnetic modeling tools in recent years. In this work, we report on these modeling software and their application to plasma processing system design and evaluation of strategies for hardware and process improvement. Several of these examples deal with process uniformity, which is one of the major challenges facing plasma processing equipment design on large substrates. Three-dimensional plasma modeling is used to understand the sources of plasma non-uniformity, including the radio-frequency (RF) current path, and develop uniformity improvement techniques. Examples from coupled equipment and process models to investigate the dynamics of pulsed plasmas and their impact on plasma chemistry will also be discussed. [Preview Abstract] |
Thursday, November 14, 2013 4:30PM - 5:00PM |
VI3.00004: Challenges in bridging theory and applications with examples from Materials Design Invited Speaker: Sadasivan Shankar Over the past 3 decades the semiconductor industry has doubled the number of transistors on integrated circuits every 2 years, following an empirical law widely known as Moore's law. The ability of the semiconductor industry to stay on Moore's law has enabled the digital revolution and now the convergence of communications and computing. However, as the size of the smallest structures decrease, this has required the introduction of many new materials and the interactions of these heterogeneous materials and processing is increasing in complexity. The increasing use of the nano materials and the ever-shrinking dimensions requires development of an improved understanding of material properties (electronic, thermal, mechanical, and optical) at differences scales. Due to the presence of multiple thin films and metal alloys in the nano technology, grains, and interfaces assume more significance than before. This paper reviews some of the challenges in materials and the opportunities for using fundamental modeling and characterization techniques to enable successful management of these heterogeneous interactions. As the industry evaluates new materials for future technologies, research is needed to develop new modeling and characterization techniques to evaluate nano-materials and materials with nano-scale dimensions and structure. [Preview Abstract] |
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