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Vacuum Technology.Pdf Vacuum Technology Nagamitsu Yoshimura Vacuum Technology Practice for Scientific Instruments Dr. Nagamitsu Yoshimura 3-22-75 Fujimoto Kokubunji, Tokyo 185-0031 Japan ISBN 978-3-540-74432-0 e-ISBN 978-3-540-74433-7 Library of Congress Control Number: 2007933832 c 2008 Springer-Verlag Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Cover design: WMX Design, Heidelberg Printed on acid-free paper 987654321 springer.com Preface Many scientific instruments for analyzing specimen surface such as the electron microscope and the Auger electron spectrometer require clean, ultrahigh vacuum. The electron microscope and Auger electron spectrometer need fine electron probe, requiring a field emission emitter which can well work under ultrahigh vacuum. In the electron microscope and the ion microscope, microdischarges due to applying high voltage to electrodes sometime occur, resulting in deterioration of image qual- ity. Microdischarges are related with the gas molecules on the surfaces of insulators and electrodes. For many scientific instruments such as the electron microscope, a very clean, ul- trahigh vacuum is necessary in the vicinity of the specimen and the electron emitter. So, ultrahigh vacuum technology is essential for microscope engineers and micro- scope users. This book consists of the following chapters: Chapter 1 Designing of Evacuation Systems Chapter 2 Vacuum Pumps Chapter 3 Simulation of Pressures in High-Vacuum Systems Chapter 4 Outgassing Chapter 5 Phenomena Induced by Electron Irradiation Chapter 6 Vacuum Gauges Chapter 7 Microdischarges in High Vacuum Chapter 8 Emitters for Fine Electron Probes Some important articles on the subject of every chapter are reviewed, and their dis- cussions and conclusions are presented in rather high detail. The author believes that Chaps. 1, 2, 3, 4, 5, 6 would help the engineers who engage in designing the vacuum systems of ultrahigh vacuum scientific instruments such as electron mi- croscopes. Chapters 7 and 8 will help the users of the scientific instruments using electron probes to understand the key technology intrinsic to electron beam systems, like high-voltage discharge and narrow electron beam emitter. v vi Preface Acknowledgement is made to Dr. Frank Gualtieri, Professor of University of Maryland University Collage Asia, who kindly read the manuscript through and made useful correction. He gave me some useful suggestion throughout this review. I would like to express my appreciation to Dr. Tatsuo Okano, Professor of Tokyo University, for encouraging me to publish this book. Due thanks are given to the coworker of JEOL Ltd., especially to Mr. Haruo Hirano. It is a nice memory that we all did our best in working on the electron beam system technology related to vacuum. I would like to express my appreciation to JEOL Ltd. for permission to present its know-how technologies based on our experiments. 09 January 2007 Nagamitsu Yoshimura Profile of author Nagamitsu Yoshimura 1965; Graduated from Osaka Prefecture University, Engineering Division. Entered JEOL Ltd. Engaging in research and development of vacuum related technology in electron microscopes for 35 years at JEOL Ltd. 2000; Retired at the age limit from JEOL Ltd. 1985; Received Doctor of Engineering degree from Osaka Prefec- ture University. Thesis for degree: Research and develop- ment of the high-vacuum system of electron microscopes (in Japanese). Contents 1 Designing of Evacuation Systems ................................ 1 SelectionofPumpingSpeed...................................... 2 Pumping-downCharacteristics ............................... 2 Steady-StateEvacuation..................................... 3 Roughing System .......................................... 3 BackstreamingofRPOilVapor................................... 4 BackstreamingofDPOilVapor................................... 6 OverloadinHigh-VacuumEvacuationSystems...................... 8 DPIn-SeriesSystem............................................. 14 UltrahighVacuumElectronMicroscopes............................ 27 Know-how Technology in Designing UHV Evacuation Systems . 31 References..................................................... 32 2 Vacuum Pumps ................................................ 35 MechanicalPumps.............................................. 35 DiffusionPumps................................................ 38 TurbomolecularPumps .......................................... 41 DryVacuumPumps............................................. 45 Cryopumps . ................................................... 51 VaporPressuresforGases........................................ 55 SputterIonPumps .............................................. 56 NoblePumpsforInertGases...................................... 60 GetterPumps................................................... 68 Titanium-SublimationPumps ................................ 68 Non-EvaporableGetter(NEG)Pumps......................... 69 Methods for Measuring Pumping Speeds............................ 70 OrificeMethod............................................. 70 Three-Gauge Method (Pipe Method) .......................... 71 Three-Point Pressure Method (3PP Method) . ................. 72 References..................................................... 76 vii viii Contents 3 Simulation of Pressures in High-Vacuum Systems .................. 85 ConventionalCalculationofSystemPressures....................... 85 3AVacuumCircuits............................................. 87 BasicConceptofVacuumCircuits............................ 87 DesigningofVacuumCircuits................................ 89 SimulationofPressures ..................................... 91 Resistor-NetworkSimulationMethod.......................... 91 MatrixCalculationofPressures............................... 94 3B Molecular-Flow Conductance . ................................108 Conductance ..............................................108 Transmission Probability ....................................109 3CGas-FlowPatterns............................................117 References.....................................................119 4 Outgassing ....................................................123 ProcessofOutgassing ...........................................123 Diffusion .................................................124 Recombination-limitedOutgassing............................134 DataofOutgassing..............................................136 StainlessSteel.............................................136 Electro-polishingandVacuumFiring..........................137 Aluminum Alloy, Copper and Titanium . ......................147 Permeation Through Elastomer Seals ..........................148 Evaporation...............................................156 Methods for Measuring Outgassing Rates ...........................157 DifferentialPressure-riseMethod[4-41].......................159 Variable Conductance Method [4-43] ..........................161 Conductance Modulation Method [4-44] . ......................164 Two-Point Pressure Method and One-Point Pressure Method [4-45] 167 References.....................................................168 5 Phenomena Induced by Electron Irradiation ......................175 5AElectron/PhotonStimulatedDesorption(ESD/PSD)...............176 5BPolymerizationofHydrocarbonMolecules.......................182 TransportofHydrocarbonMoleculesinHighVacuum............182 TransportofHydrocarbonMoleculesinUltrahighVacuum........185 Materials to be Polymerized by Electron Beam Irradiation . .......192 5C Darkening in Secondary Electron Images in SEM .................195 5DEtchingofCarbonaceousSpecimens............................198 References.....................................................199 6 Vacuum Gauges ................................................205 MechanicalGauges..............................................207 CapacitanceManometer.....................................207 Thermal Conductivity Gauges . ....................................209 Contents ix PiraniGauge ..............................................209 ViscosityGauges................................................211 SpinningRotorGauge ......................................211 Crystal Oscillation Gauge. ................................214 IonizationGauges...............................................217 PenningGauge.............................................217 SputterIonPumpasaPressureIndicator.......................220 Bayard-AlpertIonizationGauge..............................221 ExtractorGauge............................................228 Hot-Cathode Magnetron Ionization Gauge . .....................231 Cold-Cathode Ionization Gauge for UHV ......................232 MagneticSector[6-24]......................................234
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