B5 FUNDAMENTALS OF VACUUM TECHNOLOGY Fundamentals of Vacuum Technology Fundamentals of Vacuum Technology revised and compiled by Dr. Walter Umrath with contributions from Dr. Hermann Adam , Alfred Bolz, Hermann Boy, Heinz Dohmen, Karl Gogol, Dr. Wolfgang Jorisch, Walter Mšnning, Dr. Hans-JŸrgen Mundinger, Hans-Dieter Otten, Willi Scheer, Helmut Seiger, Dr. Wolfgang Schwarz, Klaus Stepputat, Dieter Urban, Heinz-Josef Wirtzfeld, Heinz-Joachim Zenker 1 Fundamentals of Vacuum Technology 2 Preface Preface A great deal has transpired since the final reprint of the previous edition of Fundamentals of Vacuum Technology appeared in 1987. LEYBOLD has in the meantime introduced a number of new developments in the field. These include the dry-running ALL×ex chemicals pump, the COOLVAC-FIRST cryopump systems with quick regeneration feature, turbomolecular pumps with magnetic bearings, the A-Series vacuum gauges, the TRANSPECTOR and XPR mass spectrometer transmitters, leak detectors in the UL series, and the ECOTEC 500 leak detector for refrigerants and many other gases. Moreover, the present edition of the ÒFundamentalsÓ goes into much greater detail on some topics. Among these are residual gas analyses at low pressures, measurement of low pressures, pressure monitoring, open- and closed-loop pressure control, and leaks and their detection. Included for the first time are the sections covering the devices used to measure and control the application of coatings and uses for vacuum technology in the coating process. Naturally LEYBOLDÕs ÒVacuum Technology Training CenterÓ at Cologne was dependent on the invaluable support of numerous associates in collating the literature on hand and preparing new sections; I would like to expressly thank all those individuals at this juncture. A special word of appreciation is due the Communications Department for its professional contribution in preparing this document for publishing. Regrettably Dr. Hermann Adam, who at one time compiled the very first version of the ÒFundamentalsÓ, did not live to see the publication of this edition. Though he had been in retirement for many years, he nonetheless labored over the corrections and editing of this current edition until shortly before his death. I hope that this volume will enjoy a response as favorable as the previous version. Dr. Walter Umrath Cologne, August, 1998 3 Fundamentals of Vacuum Technology 4 Table of Contents 1. Vacuum physics Quantities, their symbols, 2.2 Choice of pumping process . .60 units of measure and definitions . .9 2.2.1 Survey of the most usual pumping processes . .60 1.1 Basic terms and concepts in vacuum technology . .9 2.2.2 Pumping of gases (dry processes) . .62 1.2 Atmospheric air . .13 2.2.3 Pumping of gases and vapors (wet processes) . .62 1.3 Gas laws and models . .13 2.2.4 Drying processes . .64 1.3.1 Continuum theory . .13 2.2.5 Production of an oil-free (hydrocarbon-free) vacuum . .65 1.3.2 Kinetic gas theory . .13 2.2.6 Ultrahigh vacuum working Techniques . .65 1.4 The pressure ranges in vacuum technology and 2.3 Evacuation of a vacuum chamber and determination of their characterization . 14 pump sizes . .66 1.5 Types of flow and conductance . .15 2.3.1 Evacuation of a vacuum chamber 1.5.1 Types of flow . .15 (without additional sources of gas or vapor) . .66 1.5.2 Calculating conductance values . .16 2.3.1.1 Evacuation of a chamber in the rough vacuum region . .67 1.5.3 Conductance for piping and openings . .16 2.3.1.2 Evacuation of a chamber in the high vacuum region . .68 1.5.4 Conductance values for other elements . .18 2.3.1.3 Evacuation of a chamber in the medium vacuum region . .68 2.3.2 Determination of a suitable backing pump . .69 2. Vacuum Generation . .19 2.3.3 Determination of pump-down time from nomograms . .70 2.1 Vacuum pumps: A survey . .19 2.3.4 Evacuation of a chamber where gases and 2.1.1 Oscillation displacement vacuum pumps . .20 vapors are evolved . .71 2.1.1.1 Diaphragm pumps . .20 2.3.5 Selection of pumps for drying processes . .71 2.1.2 Liquid sealed rotary displacement pumps . .20 2.3.6 Flanges and their seals . .73 2.1.2.1 Liquid ring pumps . .20 2.3.7 Choice of suitable valves . .73 2.1.2.2 Oil sealed rotary displacement pumps . .21 2.3.8 Gas locks and seal-off fittings . .75 2.1.2.2.1 Rotary vane pumps (TRIVAC A, TRIVAC B, TRIVAC E, SOGEVAC) . .21 3. Vacuum measurement, monitoring, control 2.1.2.2.2 Rotary plunger pumps (E-Pumps) . .23 and regulation . .76 2.1.2.2.3 Trochoid pumps . .24 3.1 Fundamentals of low-pressure measurement . .76 2.1.2.2.4 The gas ballast . .24 3.2 Vacuum gauges with pressure reading that is independent 2.1.3 Dry compressing rotary displacement pumps . .27 of the type of gas . .77 2.1.3.1 Roots pumps . .27 3.2.1 Bourdon vacuum gauges . .77 2.1.3.2 Claw pumps . .31 3.2.2 Diaphragm vacuum gauges . .77 2.1.3.2.1 Claw pumps with internal compression for the 3.2.2.1 Capsule vacuum gauges . .77 semiconductor industry (ÒDRYVAC SeriesÓ) . .33 3.2.2.2 DIAVAC diaphragm vacuum gauge . .78 2.1.3.2.2 Claw pump without internal compression for chemistry 3.2.2.3 Precision diaphragm vacuum gauges . .78 applications (ÒALLáexÓ) . .35 3.2.2.4 Capacitance diaphragm gauges . .78 2.1.4 Accessories for oil-sealed rotary displacement pumps . .38 3.2.3 Liquid-filled (mercury) vacuum gauges . .79 2.1.5 Condensers . .38 3.2.3.1 U-tube vacuum gauges . .79 2.1.6 Fluid-entrainment pumps . .40 3.2.3.2 Compression vacuum gauges (according to McLeod) . .79 2.1.6.1 (Oil) Diffusion pumps . .41 3.3 Vacuum gauges with gas-dependent pressure reading . .81 2.1.6.2 Oil vapor ejector pumps . .43 3.3.1 Spinning rotor gauge (SRG) (VISCOVAC) . .81 2.1.6.3 Pump fluids . .44 3.3.2 Thermal conductivity vacuum gauges . .82 2.1.6.4 Pump fluid backstreaming and its suppression 3.3.3 Ionization vacuum gauges . .83 (Vapor barriers, baffles) . .44 3.3.3.1 Cold-cathode ionization vacuum gauges 2.1.6.5 Water jet pumps and steam ejectors . .45 (Penning vacuum gauges) . .83 2.1.7 Turbomolecular pumps . .46 3.3.3.2 Hot-cathode ionization vacuum gauges . .84 2.1.8 Sorption pumps . .50 3.4 Adjustment and calibration; DKD, PTB national standards . .86 2.1.8.1 Adsorption pumps . .50 3.4.1 Examples of fundamental pressure measurement methods 2.1.8.2 Sublimation pumps . .51 (as standard methods for calibrating vacuum gauges . .87 2.1.8.3 Sputter-ion pumps . .51 3.5 Pressure monitoring,control and regulation in 2.1.8.4 Non evaporable getter pumps (NEG pumps) . .53 vacuum systems . .88 2.1.9 Cryopumps . .54 3.5.1 Fundamentals of pressure monitoring and control . .88 2.1.9.1 Types of cryopump . .54 3.5.2 Automatic protection, monitoring and control 2.1.9.2 The cold head and its operating principle . .55 of vacuum systems . .89 2.1.9.3 The refrigerator cryopump . .56 3.5.3 Pressure regulation and control in rough and medium 2.1.9.4 Bonding of gases to cold surfaces . .56 vacuum systems . .90 2.1.9.5 Pumping speed and position of the cryopanels . .57 3.5.4 Pressure regulation in high and ultrahigh vacuum systems . .92 2.1.9.6 Characteristic quantities of a cryopump . .57 3.5.5 Examples of applications with diaphragm controllers . .93 5 Table of Contents 4. Analysis of gas at low pressures using 5.5.1 Halogen leak detectors (HLD 4000, D-Tek) . .116 mass spectrometry . .95 5.5.2 Leak detectors with mass spectrometers (MS) . .116 4.1 General . .95 5.5.2.1 The operating principle for a MSLD . .117 4.2 A historical review . .95 5.5.2.2 Detection limit, background, gas storage in oil 4.3 The quadrupole mass spectrometer (TRANSPECTOR) . .96 (gas ballast), floating zero-point suppression . .117 4.3.1 Design of the sensor . .96 5.5.2.3 Calibrating leak detectors; test leaks . .118 4.3.1.1 The normal (open) ion source . .96 5.5.2.4 Leak detectors with quadrupole 4.3.1.2 The quadrupole separation system . .97 mass spectrometer (ECOTEC II) . .119 4.3.1.3 The measurement system (detector) . .98 5.5.2.5 Helium leak detectors with 180¡ sector mass spectrometer 4.4 Gas admission and pressure adaptation . .99 (UL 200, UL 500) . ..