A Users Guide to Vacuum Technology E-Book

John F. O'Hanlon

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 907

Veröffentlichungsjahr: 2023

Beschreibung

A USERS GUIDE TO VACUUM TECHNOLOGY Choose and understand the vacuum technology that fits your project's needs with this indispensable guide Vacuum technology is used to provide process environments for other kinds of engineering technology, making it an unsung cornerstone of hundreds of projects incorporating analysis, research and development, manufacturing, and more. Since it is very often a secondary technology, users primarily interested in processes incorporating it will frequently only encounter vacuum technology when purchasing or troubleshooting. There is an urgent need for a guide to vacuum technology made with these users in mind. For decades, A User's Guide to Vacuum Technology has met this need, with a user-focused introduction to vacuum technology as it is incorporated into semiconductor, optics, solar sell, and other engineering processes. With an emphasis on otherwise neglected subjects and on accessibility to the secondary user of vacuum technology, it balances treatment of older systems that are still in use with a survey of the latest cutting-edge technologies. The result promises to continue as the essential guide to vacuum systems. Readers of the fourth edition of A User's Guide to Vacuum Technology will also find: * Expanded treatment of gauges, pumps, materials, systems, and best??operating practices * Detailed discussion of cutting-edge topics like ultraclean vacuum and contamination control * An authorial team with decades of combined research and engineering experience A User's Guide to Vacuum Technology is essential for those entering emerging STEM programs, engineering professionals and graduate students working with a huge range of engineering technologies.

Leseprobe

Table of Contents

Cover

Table of Contents

Title Page

Copyright Page

Dedication Page

Preface

Symbols

Part I: Its Basis

1 Vacuum Technology

1.1 Units of Measurement

References

2 Gas Properties

2.1 Kinetic Picture of a Gas

2.2 Gas Laws

2.3 Elementary Gas Transport Phenomena

References

3 Gas Flow

3.1 Flow Regimes

3.2 Flow Concepts

3.3 Continuum Flow

3.4 Molecular Flow

3.5 Models Spanning Molecular and Viscous Flow

References

4 Gas Release from Solids

4.1 Vaporization

4.2 Diffusion

4.3 Thermal Desorption

4.4 Stimulated Desorption

4.5 Permeation

4.6 Pressure Limitations During Pumping

References

Part II: Measurement

5 Pressure Gauges

5.1 Direct Reading Gauges

5.2 Indirect Reading Gauges

References

6 Flow Meters

6.1 Molar Flow, Mass Flow, and Throughput

6.2 Rotameters and Chokes

6.3 Differential Pressure Devices

6.4 Thermal Mass Flow Technique

References

7 Pumping Speed

7.1 Definition

7.2 Mechanical Pump Speed Measurements

7.3 High Vacuum Pump Speed Measurements

References

8 Residual Gas Analyzers

8.1 Instrument Description

8.2 Installation and Operation

8.3 Calibration

8.4 Choosing an Instrument

References

9 Interpretation of RGA Data

9.1 Cracking Patterns

9.2 Qualitative Analysis

9.3 Quantitative Analysis

References

Part III: Production

10 Mechanical Pumps

10.1 Rotary Vane

10.2 Lobe

10.3 Claw

10.4 Multistage Lobe

10.5 Scroll

10.6 Screw

10.7 Diaphragm

10.8 Reciprocating Piston

10.9 Mechanical Pump Operation

References

11 Turbomolecular Pumps

11.1 Pumping Mechanism

11.2 Speed–Compression Relations

11.3 Ultimate Pressure

11.4 Turbomolecular Pump Designs

11.5 Turbo‐Drag Pumps

References

12 Diffusion Pumps

12.1 Pumping Mechanism

12.2 Speed–Throughput Characteristics

12.3 Boiler Heating Effects

12.4 Backstreaming, Baffles, and Traps

References

13 Getter and Ion Pumps

13.1 Getter Pumps

13.2 Ion Pumps

References

14 Cryogenic Pumps

14.1 Pumping Mechanisms

14.2 Speed, Pressure, and Saturation

14.3 Cooling Methods

14.4 Cryopump Characteristics

References

Part IV: Materials

15 Materials in Vacuum

15.1 Metals

15.2 Glasses and Ceramics

15.3 Polymers

References

16 Joints Seals and Valves

16.1 Permanent Joints

16.2 Demountable Joints

16.3 Valves and Motion Feedthroughs

References

17 Pump Fluids and Lubricants

17.1 Pump Fluids

17.2 Lubricants

References

Part V: Systems

18 Rough Vacuum Pumping

18.1 Exhaust Rate

18.2 Crossover

References

19 High Vacuum Systems

19.1 Diffusion‐Pumped Systems

19.2 Turbo‐Pumped Systems

19.3 Sputter‐Ion‐Pumped Systems

19.4 Cryo‐Pumped Systems

19.5 High Vacuum Chambers

References

20 Ultraclean Vacuum Systems

20.1 Ultraclean Pumps

20.2 Ultraclean Chamber Materials and Components

20.3 Ultraclean System Pumping and Pressure Measurement

References

21 Controlling Contamination in Vacuum Systems

21.1 Defining Contamination in a Vacuum Environment

21.2 Pump Contamination

21.3 Evacuation Contamination

21.4 Venting Contamination

21.5 Internal Components, Mechanisms, and Bearings

21.6 Machining Contamination

21.7 Process‐Related Sources

21.8 Lubrication Contamination

21.9 Vacuum System and Component Cleaning

21.10 Review of Clean Room Environments for Vacuum Systems

References

22 High Flow Systems

22.1 Mechanically Pumped Systems

22.2 Throttled High Vacuum Systems

References

23 Multichambered Systems

23.1 Flexible Substrates

23.2 Rigid Substrates

23.3 Analytical Instruments

References

24 Leak Detection

24.1 Mass Spectrometer Leak Detectors

24.2 Performance

24.3 Leak Hunting Techniques

24.4 Leak Detecting with Hydrogen Tracer Gas

References

Part VI: Appendices

Appendix A: Units and Constants

A.1 Physical Constants

A.2 SI Base Units

A.3 Conversion Factors

Appendix B: Gas Properties

B.1 Mean Free Paths of Gasses as a Function of Pressure at

T

= 25°C

B.2 Physical Properties of Gasses and Vapors at

T

= 0°C

B.3 Cryogenic Properties of Gases

B.4 Gas Conductance and Flow Formulas

B.5 Vapor Pressure Curves of Common Gases

B.6 Appearance of Discharges in Gases and Vapors at Low Pressures

B.7 DC Breakdown Voltages for Air and Helium Between Flat Parallel Plates

B.8 Particle Settling Velocities in Air

Appendix C: Material Properties

C.1 Outgassing Rates of Vacuum‐Baked Metals

C.2 Outgassing Rates of Unbaked Metals

C.3 Outgassing Rates of Ceramics and Glasses

C.4 Outgassing Rates of Elastomers

C.5 Permeability of Polymeric Materials

C.6 Vapor Pressure Curves of the Solid and Liquid Elements (Sheet A)

C.7 Outgassing Rates of Polymers

C.8 Austenitic Stainless Steels

Appendix D: Isotopes

D.1 Natural Abundances

Appendix E: Cracking Patterns

E.1 Cracking Patterns of Pump Fluids

E.2 Cracking Patterns of Gases

E.3 Cracking Patterns of Common Vapors

E.4 Cracking Patterns of Common Solvents

E.5 Cracking Patterns of Semiconductor Dopants

Appendix F: Pump Fluid Properties

F.1 Compatibility of Elastomers and Pump Fluids

F.2 Vapor Pressures of Mechanical Pump Fluids

F.3 Vapor Pressures of Diffusion Pump Fluids

F.4 Kinematic Viscosities of Pump Fluids

F.5 Viscosity Index, Viscosity and Temperature

F.6 Kinematic Viscosity Conversion Factors

References

Index

End User License Agreement

List of Tables

Chapter 1

Table 1.1 ISO Definition of Vacuum Pressure Ranges and Descriptions

Table 1.2 Components of Dry Atmospheric Air

Chapter 2

Table 2.1 Low‐Pressure Properties of Air

Chapter 3

Table 3.1 Dimensionless Constant

Y

Used in Rectangular Duct Eqs. (3.17) and...

Table 3.2 Transmission Probability

a,

for Round Pipes

Table 3.3 Transmission Probability

a,

for Thin, Rectangular, Slit‐like Duct...

Chapter 4

Table 4.1 Average Residence Time of Chemisorbed Molecules

Table 4.2 Desorption Yields for Stainless Steel and Aluminum

Chapter 5

Table 5.1 Approximate Relative Sensitivity of Bayard–Alpert Gauge Tubes for...

Chapter 6

Table 6.1 Thermal Mass Flow Meter Correction Factors

Chapter 8

Table 8.1 Experimental Total Ionization Cross Sections (70 V) for Selected ...

Table 8.2 Properties of RGA Filament Materials

Chapter 9

Table 9.1 Common Ion–Molecule Reactions

Table 9.2 Analysis of Background Gases in an Orb–Ion Pumped System

Chapter 12

Table 12.1 Diffusion Pump Backstreaming

Chapter 13

Table 13.1 Order of Preference of Gas Displacement on Titanium Film

Table 13.2 Initial Sticking Coefficient and Quantity Sorbed for Various Gas...

Chapter 15

Table 15.1 Firing Temperatures for Some Common Metals

Table 15.2 The Theoretical Time to Reach an Outgassing Rate of 10

−13

...

Table 15.3 Outgassing Rates of 316L Stainless Steel After Different Process...

Table 15.4 Selected Properties of Common Aluminum Alloys

Table 15.5 Properties of Some Glasses Used in Vacuum Applications

Table 15.6 Physical Properties of Some Ceramics

Table 15.7 Generic, Trade, and Chemical Names of Polymer Materials Frequent...

Chapter 16

Table 16.1 A Summary of Various Mechanical and General Considerations Regar...

Table 16.2 Compression Set for Viton and Kalrez for Various Times and Tempe...

Chapter 17

Table 17.1 Properties of Representative Mechanical and Turbomolecular Pump ...

Table 17.2 Properties of Representative Diffusion Pump Fluids

Table 17.3 Properties of Representative Vacuum Greases

Chapter 18

Table 18.1 Critical Saturation Ratio (

S

c

) for Three Condensation Processes ...

Table 18.2 Lower Crossover Pressure Limits

Table 18.3 Upper Crossover Pressure Limits

Table 18.4 Best Practices for Rough Pumping

Chapter 19

Table 19.1 Best Practices for Diffusion‐Pumped Systems

Table 19.2 Best Practices for Turbo‐Pumped Systems

Table 19.3 Best Practices for Sputter‐Ion‐Pumped Systems

Table 19.4 Best Practices for Cryo‐Pumped Systems

Table 19.5 Best Practices for General System Operation

Table 19.6 Best Practices for Managing Water Vapor

Chapter 20

Table 20.1 ISO Standards Definitions for Ultraclean Vacuum

Table 20.2 Best Practices for Ultraclean Vacuum Systems

Chapter 21

Table 21.1 Maximum Number of Particles Allowed per m

3

≥ Given Diameter, as ...

Table 21.2 Allowed Size and Distribution of Particles at Various Levels Acc...

Table 21.3 Allowed Nonvolatile Residue (NVR) Levels as Permitted by IEST‐ST...

Table 21.4 Efficiency of Removing Aluminum Oxide Particles from Optical Sur...

Table 21.5 Best Practices for Contamination Control

Chapter 22

Table 22.1 Enthalpy of Gases Frequently Pumped at High Flow Rates

Table 22.2 Best Practices for High Gas Flow Systems

Chapter 24

Table 24.1 Best Practices for Leak Detection

List of Illustrations

Chapter 1

Fig. 1.1 View of a viscous gas and a rarefied gas.

Fig. 1.2 Relation between the atmospheric pressure and the geometric altitud...

Chapter 2

Fig. 2.1 Relative velocity distribution of air at 0°C, 25°C, and 400°C.

Fig. 2.2 Relative velocity distribution of several gases at 25°C.

Fig. 2.3 Individual molecular paths.

Fig. 2.4 Dalton's law: the total pressure is the sum of the partial pressure...

Fig. 2.5 Origin of the viscous force in a gas.

Fig. 2.6 Viscous shear force between two plates at 22°C.

Chapter 3

Fig. 3.1 Examples of flow regimes: (a) turbulent flow in a pipe, (b) laminar...

Fig. 3.2 Pictorial description of speed and conductance. Speed is defined at...

Fig. 3.3 Normalized speed (

S

/

A

) and conductance (

C/A

) of a thin orifice in c...

Fig. 3.4 Pressure profile through a fine leak in a vacuum wall, as calculate...

Fig. 3.5 Conceptual view of an ideal pump operating in a rarefied gas. All t...

Fig. 3.6 A molecule making a diffuse collision with a wall is scattered in a...

Fig. 3.7 A computer graphical display of the trajectories of 15 molecules en...

Fig. 3.8 Molecular transmission probability of a round pipe.

Fig. 3.9 Molecular transmission probability of a round pipe with entrance an...

Fig. 3.10 Molecular transmission probability of an annular cylindrical pipe....

Fig. 3.11 Molecular transmission probability of a rectangular duct.

Fig. 3.12 Molecular transmission probability of a chevron baffle.

Fig. 3.13 Molecular transmission probability of an elbow.

Fig. 3.14 Molecular transmission probability of a chevron baffle.

Fig. 3.15 Molecular transmission probability of a parallel plate model.

Fig. 3.16 Series conductance of two elements: (a) the pipes are isolated by ...

Fig. 3.17 Angular distribution of particles exiting tubes of various ratios ...

Fig. 3.18 Model for calculating the transmission probability of a single ele...

Fig. 3.19 Model for calculating the transmission probability of two elements...

Fig. 3.20 Example conductance evaluated using Haefer's addition theorem.

Fig. 3.21 Normalized gas flow–pressure regimes.

Chapter 4

Fig. 4.1 Potential sources of gases and vapors in a vacuum system.

Fig. 4.2 Left: The outdiffusion rate of nitrogen from one surface of a 5‐mm‐...

Fig. 4.3 Change in outdiffusion rate for an increase in temperature from

T

1

...

Fig. 4.4 Desorption rate (log) versus time (linear) for first‐order desorpti...

Fig. 4.5 Outgassing measurements for different H

2

O exposures during venting ...

Fig. 4.6 Outgassing data notation, as used in Appendixes C2, C3, C4, and C7....

Fig. 4.7 Total outgassing rate as a sum of four rates, each resulting from a...

Fig. 4.8 The total residence time for a water molecule after two bounces fro...

Fig. 4.9 Permeation of helium through

d =

 1‐mm‐ and 2‐mm‐thick 7740 gl...

Fig. 4.10 Rate limiting steps during the pumping of a vacuum chamber.

Chapter 5

Fig. 5.1 Classification of pressure gauges.

Fig. 5.2 Double‐sided capacitance manometer head assembly.

Fig. 5.3 Single‐sided capacitance manometer head assembly. The outer electro...

Fig. 5.4 Heat transfer regimes in thermal conductivity gauges, such as therm...

Fig. 5.5 Basic Pirani gauge circuit.

Fig. 5.6 Gas dependence curves for the Oerlikon Leybold Vacuum TTR91 Pirani ...

Fig. 5.7 Thermocouple gauge tube commonly used in the 0–100 Pa (0–1000 Torr)...

Fig. 5.8 Calibration curves for the Hastings DV‐6 M thermocouple gauge tube....

Fig. 5.9 Spinning rotor gauge sensor.

Fig. 5.10 Cross‐sectional views of two Bayard–Alpert sensors. Left: Bakeable...

Fig. 5.11 Control circuit for a Bayard–Alpert ionization gauge tube.

Fig. 5.12 Transient desorption during degassing a glass‐encapsulated Bayard–...

Fig. 5.13 IE514 Extractor gauge. Left: Sensing head. Right: Expanded detail ...

Fig. 5.14 Carbon monoxide concentration in an ultrahigh vacuum system as mea...

Fig. 5.15 Ion current versus grid temperature in a hot cathode UHV ion gauge...

Fig. 5.16 Cold cathode gauge: A, envelope; B, cathode; C, magnet; D, anode; ...

Fig. 5.17 Simplified view of the magnet configurations in modern inverted ma...

Chapter 6

Fig. 6.1 (a) Rotameter and (b) choke.

Fig. 6.2 Differential pressure flow elements, (a) laminar and (b) molecular....

Fig. 6.3 Principle of thermal mass flow measurement.

Fig. 6.4 Thermal mass flow sensor and temperature profile. Upper: Cross‐sect...

Fig. 6.5 Constant power mass flow controller circuit.

Fig. 6.6 Simulation and experimental gas correction functions for He and H

2

...

Chapter 7

Fig. 7.1 Test domes for the measurement of mechanical and high vacuum pumps....

Fig. 7.2 The effect of orientation on pressure gauge readings.

Chapter 8

Fig. 8.1 Left: Expanded sweep over the

M/z

 = 28 triplet showing resolution o...

Fig. 8.2 Three stages of partial pressure analysis: (a) Ionizer: hot filamen...

Fig. 8.3 One form of an open ion source.

Fig. 8.4 Schematic view of a closed ion source. Gas enters the upper end of ...

Fig. 8.5 Mass separation methods.

Fig. 8.6 A Magnetic sector mass separator (60°) with symmetrical entrance an...

Fig. 8.7 Quadrupole mass filter. Left: Idealized hyperbolic electrode cross ...

Fig. 8.8 Electric fields in a quadrupole mass filter.

Fig. 8.9 Relative transmission of a typical rf quadrupole as a function of

M

...

Fig. 8.10 Mass scan taken on a small oil diffusion pumped chamber by an rf q...

Fig. 8.11 Combination Faraday cup–electron multiplier detector.

Fig. 8.12 Channeltron

®

electron multiplier: (a) Schematic detail of cap...

Figure 8.13 Analysis of a differentially pumped residual gas analyzer using ...

Fig. 8.14 Analysis of a differentially pumped residual gas analyzer using a ...

Fig. 8.15 Measurement of the sensitivity and pumping speeds of four gases us...

Chapter 9

Fig. 9.1 This cracking pattern of methane illustrates the five largest disso...

Fig. 9.2 The argon cracking pattern illustrates isotopic mass differences (t...

Fig. 9.3 The cracking pattern of CO contains peaks due to dissociative ioniz...

Fig. 9.4 Background spectrum constructed from a (20:4:4:1:1) mixture of H

2

O,...

Fig. 9.5 Mass spectrum of Apiezon BW oil (obtained using MS9 sector spectrom...

Fig. 9.6 Comparison of residual gas background in a system contaminated with...

Fig. 9.7 Mass spectra obtained during the heating of Buna‐N rubber. (a)

T

 = ...

Fig. 9.8 Mass spectra obtained during the heating of Viton fluoro‐elastomer....

Fig. 9.9 Errors induced in the calculation of pressures of mixtures of N

2

an...

Chapter 10

Fig. 10.1 Sectional view of the Pfeiffer DUO‐35, 35 m

3

/h double‐stage, rotar...

Fig. 10.2 Schematic section through a two‐stage rotary pump.

Fig. 10.3 Pumping speed curves for the Pfeiffer UNO 30A and DUO 30A rotary v...

Fig. 10.4 Relative abundance of gases at pump ultimate: Top: After prolonged...

Fig. 10.5 Section through a single‐stage lobe blower: (1) inlet, (2) rotors,...

Fig. 10.6 Dependence of the air compression ratio

K

o

max

of the Leybold WS500...

Fig. 10.7 Lobe blower‐rotary pump combinations. Transport mode: (A) Leybold ...

Fig. 10.8 Compression sequence for 1 revolution of a claw stage: (a)–(f) sho...

Fig. 10.9 Pumping speed curve for a four‐stage booster pump exhausting direc...

Fig. 10.10 (a) Schematic illustration of a multistate lobe pump with four st...

Fig. 10.11 Pumping speed curves for a representative family of multistage lo...

Fig. 10.12 Anest‐Iwata orbiting scroll pump mechanism. Right: Plan view of o...

Fig. 10.13 Pumping speed of a model ESDP12 orbiting scroll pump.

Fig. 10.14 Cross‐sectional view of a screw vacuum pump. (1) Inlet, (2) disch...

Fig. 10.15 Pumping speed curves for a family of screw pumps.

Fig. 10.16 Diaphragm pumping mechanism.

Fig. 10.17 Pumping speed curves for four‐stage, three‐stage, and two‐stage d...

Fig. 10.18 Schematic illustration of a reciprocating piston pump configured ...

Chapter 11

Fig. 11.1 Sectional view of a rotor disk.

Fig. 11.2 Calculated curve of the compression ratio at zero flow for a singl...

Fig. 11.3 Measured compression ratio for zero flow in a Pfeiffer TPU‐400 tur...

Fig. 11.4 Maximum speed factor (Ho coefficient), single blade row with

s

/

b

 =...

Fig. 11.5 Transmission coefficient versus compression ratio (pressure ratio)...

Fig. 11.6 Measured pumping speeds for the Pfeiffer TPU‐400 turbomolecular pu...

Fig. 11.7 Rotor from a classical vertical turbomolecular pump.

Fig. 11.8 Cross section of a magnetically levitated turbomolecular pump.

Fig. 11.9 Detail of the Holweck revolving‐screw molecular drag stage used in...

Fig. 11.10 Pumping speeds of a magnetically levitated turbopump (MAG 1500) a...

Chapter 12

Fig. 12.1 A sectional view of a metal diffusion pump and some of its innovat...

Fig. 12.2 Typical diffusion pump speed curve for a given gas. Four regions a...

Fig. 12.3 Air pumping speed of the Varian VHS‐6, 6‐in. diffusion pump with a...

Fig. 12.4 Diffusion pump performance for individual gases.

Fig. 12.5 Effect of heat input variations on various diffusion pump paramete...

Fig. 12.6 Residual gas analysis of selected mass fragments backstreaming fro...

Fig. 12.7 Backstreaming of the parent peak (

M/z

= 446; Convalex‐10) over a l...

Chapter 13

Fig. 13.1 Schematic of a basic titanium sublimation pump. (1) Titanium alloy...

Fig. 13.2 Room‐temperature sorption characteristics for pure gases on batch ...

Fig. 13.3 Characteristic pumping speed versus pressure for a TSP: (a) Speed ...

Fig. 13.4 Typical pressure rise due to decrease in pumping speed as a titani...

Fig. 13.5 Early forms of the diode sputter‐ion pump. (Upper Left) Ring anode...

Fig. 13.6 Schematic diagram showing sputter deposition and pumping mechanism...

Fig. 13.7 Pump designs for inert gas pumping: (a) Brubaker's triode pump; (b...

Figure 13.8 Pumping speeds for air and argon in a 500‐L/s Varian diode Vac I...

Chapter 14

Fig. 14.1 Adsorption isotherms of xenon, krypton, and argon on porous silver...

Fig. 14.2 Adsorption of hydrogen on coconut charcoal at low pressures. ⚬ Gar...

Fig. 14.3 Cryotrapping of hydrogen on solid argon at various temperatures. T...

Fig. 14.4 Cryogenic pumping model. The gas in the pump has a temperature,

T

s

Fig. 14.5 Relative variation of pumping speed and ultimate pressure versus q...

Fig. 14.6 Schematic representation of a single‐stage Gifford–McMahon helium ...

Fig. 14.7 Sectional schematic of the API Model DE‐202 expansion head.

Fig. 14.8 Block diagram of a remotely located helium gas compressor.

Fig. 14.9 Typical liquid nitrogen‐cooled sorption pump.

Fig. 14.10 Adsorption isotherms of nitrogen, hydrogen, neon, and helium at 7...

Fig. 14.11 Pumping characteristics of a 100‐L, air‐filled chamber with (a) o...

Fig. 14.12 Typical cryogenic pumping array for a two‐stage helium gas refrig...

Fig. 14.13 Cutaway view of the Cryo‐Torr 8 cryogenic pump.

Chapter 15

Fig. 15.1 Permeation constant of H

2

through various metals as a function of ...

Fig. 15.2 Measured outgassing rates from 304L stainless steel for five diffe...

Fig. 15.3 Analysis of stainless steel surface cleaned with 40‐psig silica be...

Fig. 15.4 Measured outgassing rates from 6063 aluminum for four different su...

Fig. 15.5 EDX and RGA analysis of (a) food grade and (b) pre‐cleaned aluminu...

Fig. 15.6 Stainless steels used in vacuum equipment (AISI designation). CR =...

Fig. 15.7 Permeability of He, D

2

, Ne, Ar, and O

2

through silicon oxide glass...

Fig. 15.8 (a) Atomic arrangement in a crystalline material possessing symmet...

Fig. 15.9 Helium permeability through a number of glasses and ceramics. Afte...

Fig. 15.10 Desorption of water from a Pyrex glass surface of 180 cm

2

at incr...

Fig. 15.11 Relation between permeation and temperature for seven common gase...

Fig. 15.12 A comparison of the helium permeability through three elastomers:...

Fig. 15.13 Room temperature outgassing rates for several polymer materials. ...

Chapter 16

Fig. 16.1 Examples of welded joints: (a) Butt‐welded from the vacuum side; (...

Fig. 16.2 The appearance and location of carbide‐rich zones bordering a weld...

Fig. 16.3 Schematic‐inclusions in steel during casting and rolling.

Fig. 16.4 Porosity in high‐vacuum flanges.

Fig. 16.5 Examples of brazed joints: (a) One form of a strong butt‐lap joint...

Fig. 16.6 (a) Tapered stainless tubing for fabricating a 7052 or Pyrex glass...

Fig. 16.7 Compression set as a function of temperature measured according to...

Fig. 16.8 Calculated permeation rates for the components of atmospheric air ...

Fig. 16.9 Measured mass‐resolved gas release from two valves with Viton seat...

Fig. 16.10 Elastomer seal forms: (a) Rectangular groove, (b) ISO‐KF flange w...

Fig. 16.11 Metal gasket seals: (a) ConFlat type knife‐edge seal; (b) Helicof...

Fig. 16.12 (a) Distortion in a copper gasket caused by uneven thermal expans...

Fig. 16.13 Components of a simple elastomer‐sealed valve: (1) Valve seat; (2...

Fig. 16.14 Small right‐angle valves: (a) Elastomer‐sealed, pneumatically dri...

Fig. 16.15 Bellows‐sealed gate valve.

Fig. 16.16 Sealing concept used in the VAT gate valve.

Fig. 16.17 Poppet (left) and (right) slit valves.

Fig. 16.18 (a) Rotating and (b) translating elastomer sealed feedthroughs.

Fig. 16.19 Bakeable differentially pumped motion feedthrough. The inner seal...

Fig. 16.20 Ferrofluidic

®

seal: (1) Housing; (2) pole piece; (3) magnet;...

Fig. 16.21 Magnetically coupled UHV feedthrough mounted on a ConFlat flange....

Fig. 16.22 (a) Hydroformed and (b) welded bellows.

Fig. 16.23 (a) Translating and (b) rotating feedthroughs using metal bellows...

Chapter 17

Fig. 17.1 Vapor pressure of a pentaphenyl ether calculated using Clausius‐Cl...

Fig. 17.2 Dependence of friction on viscosity, η, relative velocity,

U

, and ...

Fig. 17.3 Oil viscosity index.

Chapter 18

Fig. 18.1 Model for calculating the initial pumping time of a vacuum chamber...

Fig. 18.2 Temperature versus time of fine thermocouples mounted in the cente...

Fig. 18.3 Relationship between relative humidity, critical saturation ratio,...

Fig. 18.4 An example calculation for determining maximum particle‐free rough...

Fig. 18.5 Relation between partial pressures of backstreamed residual gases ...

Fig. 18.6 Concentration of a model impurity, argon, counterflowing against a...

Fig. 18.7 Preventing hydrocarbon contamination from the roughing pump from r...

Fig. 18.8 Gas‐flow‐pressure characteristic of a diffusion pump and roughing ...

Fig. 18.9 Finding the proper crossover condition by performing a rate of ris...

Fig. 18.10 Chamber pressure as a function of gas throughput in a 300‐L/s tur...

Fig. 18.11 Temperature of the cryopump second stage versus time for five dif...

Chapter 19

Fig. 19.1 Diffusion‐pumped system: (1) Diffusion pump, (2) partial water baf...

Fig. 19.2 Turbo pump system, with a separate roughing line: (1) Turbomolecul...

Fig. 19.3 Valveless turbo pump system: (1) Turbo pump, (2) chamber ionizatio...

Fig. 19.4 Components of a small sputter‐ion‐pumped system: (1) Titanium subl...

Fig. 19.5 Components of a helium gas refrigerator cryogenic pump system: (1)...

Fig. 19.6 Relation between water vapor exposure and water vapor adsorption o...

Chapter 20

Fig. 20.1 High vacuum pumping system schematic.

Fig. 20.2 Vacuum chamber containing arbitrary baffles and pumps. The numbers...

Chapter 21

Fig. 21.1 Causes for contamination in the microelectronics industry.

Fig. 21.2 Particle concentration of different sizes measured both inside and...

Fig. 21.3 Surface cleanliness chart derived from ISET‐STD‐CC1246. Black dots...

Fig. 21.4 Particles 1–6 μm

2

on Si wafers added by indicated process step. St...

Fig. 21.5 Comparison of particles generated from various internal drive proc...

Fig. 21.6 Particle generation resulting from HEPA‐filtered air flowing throu...

Fig. 21.7 (a) Surface that may appear smooth but that has potential for gas,...

Fig. 21.8 (a) Vertical downflow, raised floor exit cleanroom with air return...

Chapter 22

Fig. 22.1 Pressure–speed ranges for some thin‐film growth, deposition, and e...

Fig. 22.2 Useful pressure–speed ranges for some pumping systems: (A) rotary ...

Fig. 22.3 Pressure pulsation within the exhaust of a dry pump. Air can count...

Fig. 22.4 Generic reactive processing chamber illustrating

independent

contr...

Fig. 22.5 Hydrogen pumping speed (a), and argon throughput (b), as a functio...

Fig. 22.6 Methane compression ratio as a function of argon gas flow in a Bal...

Fig. 22.7 Measured helium partial pressure in the chamber as a function of n...

Fig. 22.8 Pressure dependence of cryogenic pumping speed. (a) Free surface, ...

Chapter 23

Fig. 23.1 Schematic representation of slit configurations for different two‐...

Fig. 23.2 Schematic representation of an advanced vacuum web coater containi...

Fig. 23.3 Schematic view of a transportable cassette for holding a rolled, t...

Fig. 23.4 An inline system designed for the deposition of chrome–copper–chro...

Fig. 23.5 Inline system for the deposition of

p–i–n

solar cells....

Fig. 23.6 Large double‐ended, continuous flow production glass coating syste...

Fig. 23.7 Detail (vertical cross section) showing the method of gas isolatio...

Fig. 23.8 Cluster tool system designed for silicon device fabrication. This ...

Fig. 23.9 The Dielectric Etch eMax™ Centura

®

cluster tool is designed f...

Fig. 23.10 Endura

®

xP cluster tool system for deposition of metal films...

Fig. 23.11 Schematic of a gas sampling system such as might be used on an at...

Chapter 24

Fig. 24.1 Vacuum circuit of a classical forward flow leak detector. (1) Rota...

Fig. 24.2 Counter flow leak detector configuration. (1) Dry rotary vane pump...

Fig. 24.3 Sensitivity versus pressure for forward flow and counter flow leak...

Fig. 24.4 Three techniques for using an MSLD to detect leaks in a vacuum cha...

Fig. 24.5 A bypass sampling technique for sniffing He from internally pressu...

Fig. 24.6 Response of a sealed chamber to a leak and to outgassing from inte...

Fig. 24.7 Calculated helium permeation at 25 and 80°C through a Viton gasket...

Appendix B

Fig. B.8 Calculated particle settling velocities in air for particles of den...

Guide

Cover Page

Title Page

Copyright Page

Dedication Page

Preface

Symbols

Table of Contents

Begin Reading

Appendix A Units and Constants

Appendix B Gas Properties

Appendix C Material Properties

Appendix D Isotopes

Appendix E Cracking Patterns

Appendix F Pump Fluid Properties

Index

Wiley End User License Agreement

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A Users Guide to Vacuum Technology

Fourth Edition

John F. O'Hanlon

Emeritus Professor of Electrical and Computer Engineering

University of Arizona

Tucson, Arizona, USA

Timothy A. Gessert

Gessert Consulting, LLC

Conifer, Colorado, USA

Copyright © 2024 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.Published simultaneously in Canada.

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Library of Congress Cataloging‐in‐Publication DataNames: O’Hanlon, John F., 1937– author. | Gessert, Timothy A., author.Title: A users guide to vacuum technology / John F. O’Hanlon, Emeritus Professor of Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, USA, Timothy A. Gessert, Gessert Consulting, LLC, Conifer, Colorado, USA.Description: 4th edition. | Hoboken, New Jersey : John Wiley & Sons, Inc., [2024] | Includes index.Identifiers: LCCN 2023024446 (print) | LCCN 2023024447 (ebook) | ISBN 9781394174133 (hardback) | ISBN 9781394174140 (adobe pdf) | ISBN 9781394174225 (epub)Subjects: LCSH: Vacuum technology–Handbooks, manuals, etc.Classification: LCC TJ940 .O37 2024 (print) | LCC TJ940 (ebook) | DDC 621.5/5–dc23/eng/20230630LC record available at https://lccn.loc.gov/2023024446LC ebook record available at https://lccn.loc.gov/2023024447

Cover image: WileyCover design: Courtesy of NASA

For Jean, Carol, Paul, and AmandaandFor Janet, Rachael, Kathryn, and Benjamin

Preface

A Users Guide to Vacuum Technology, Fourth Edition, focuses on the operation, understanding, and selection of equipment for processes used in semiconductor, optics, renewable energy, and related emerging technologies. It emphasizes subjects not adequately covered elsewhere, while avoiding in‐depth treatments of topics of interest only to the vacuum system designer or vacuum historian. The discussions of gauges, pumps, and materials present a required prelude to the later discussion of fully integrated vacuum systems. System design options are grouped according to their function and include both single‐ and multichamber systems and how details of each design are determined by specific requirements of a production or research application.

During the twenty years since the publication of the third edition, the needs of vacuum technology users have evolved considerably. For example, in 2003, when the third edition was published, the minimum feature width for a typical semiconductor fabrication facility was on the order of 200 nm: the “200‐nm node.” Approximately ten years later in 2013, production at the 20‐nm node was becoming available, and its related lithography tools began to require UV exposure in vacuum because any gas ambient detrimentally absorbed or scattered UV light. Presently, the 2‐nm node is being tested for advanced integrated circuit processes, and their (ultra‐) UV light sources require even more advanced vacuum systems, as well as related equipment with increasingly tightened specification regarding particle, film, and gas‐phase contamination. Few (if any) historic vacuum textbooks include these topics to the extent required by today's technologists.

The past two decades have also featured an unprecedented increase in the use of sophisticated vacuum‐based processes for mass producing consumer products, such as low‐cost eyeglass reflective coatings, durable cookware coatings, secure bank notes, RFID tags, and coated plastic films.

Since the publication of the third edition, the authors of this book have collectively taught several thousands of students at academic institutions, in high‐technology companies, and at professional society meetings. Through their experience, the authors have acquired an unusually diverse and unique exposure to industries involved in present vacuum technology processes, future directions, and the related problems they are facing. Much of this experience has been incorporated into this fourth edition, with the goal of assisting users with insight needed for success in both their present and future activities.

Although it is expected that academic students will continue to find this book a valuable reference in their pursuit of advanced degrees, the primary audience of this fourth edition is expected to be vacuum technologists and scientists already working in vacuum technology. However, it is expected that initiatives to expand semiconductor production and developments related to quantum computing both will require the type of advanced guidance presented in this book. Finally, vacuum users in other technology fields are also expected to find this book a valuable resource, e.g., space simulation, fusion research, renewable energy, and medical devices.

In addition to including new requirements and related equipment changes within these technology sectors, another enhancement in this fourth edition includes expanded discussions on vacuum technology Best Practices. This type of general guidance would have been acquired historically through mentoring by experienced colleagues; however, the authors have seen rapid developments in many high‐technology sectors, as well as frequent career changes or added management responsibilities, have left many vacuum technologists in greater need of this type of reliable yet succinct guidance. It is hoped that this edition of A Users Guide to Vacuum Technology can fill some of the education gap resulting from this loss of historic “mentoring,” as well as assist senior technologists in appreciating some of the more advanced vacuum concepts and descriptions.

The authors thank countless personal colleagues, students, and other researchers who over many years have provided numerous questions and practical solutions to the vacuum topics that have been included in this book. At the risk of many unintentional omissions, the authors would like to particularly thank Bruce Kendal for many discussions that continue to remain highly relevant to this book, Frank Zimone for the idea of incorporating “Best Practices,” and Howard Patton for the original development of the AVS Short Course, Controlling Contamination in Vacuum Systems, on which Chapter 21 of this fourth edition is broadly based.

John F. O'Hanlon  Timothy A. Gessert

Tucson, Arizona, USA Conifer, Colorado, USA

Symbols

Symbol

Quantity

Units

A

Area

m

2

B

Magnetic field strength

T (tesla)

C

Conductance (gas)

L/s

C′

vena contracta

D

Diffusion constant

m

2

/s

E

o

Heat transfer

J‐s

−1

‐m

−2

F

Force

N (newton)

G

Electron multiplier gain

H

Heat flow

J/s

K

Compression ratio (gas)

K

p

Permeability constant (gas)

m

2

/s

Kn

Knudsen's number

K

R

Radiant heat conductivity

J‐s

−1

‐m

−1

‐K

−1

K

T

Thermal conductivity

J‐s

−1

‐m

−1

‐K

−1

M

Molecular weight

N

Number of molecules

N

o

Avogadro's number

(kg‐mol)

−1

P

Pressure

Pa (pascal)

Q

Gas flow

Pa‐m

3

/s

R

Gas constant

J‐(kg‐mol)

−1

‐s

−1

R

Reynolds' number

S

Pumping speed

L/s

S

′

Gauge sensitivity

Pa

−1

S

C

Critical saturation ratio

T

Absolute temperature

K

U

Average gas stream velocity

m/s

U

Mach number

V

Volume

m

3

V

a

Acceleration potential

V

V

b

Linear blade velocity

m/s

V

o

Normal specific volume of an ideal gas

m

3

/(kg‐mol)

W

Ho coefficient

a

Transmission probability

b

Turbopump blade chord length, or length dimension

m

c

Condensation coefficient

c

p

Specific heat at constant pressure

J‐(kg‐mol)

−1

‐K

−1

c

v

Specific heat at constant volume

J‐(kg‐mol)

−1

‐K

−1

d

Diameter dimension

m

d

o

Molecular diameter

m

d

′

Average molecular spacing

m

e

Length dimension

m

i

e

Emission current

A

i

p

Plate current

A

k

Boltzmann constant

J/K

l

Length dimension

m

m

Mass

kg

n

Gas density

m

−3

q

Outgassing rate

Pa‐m/s

q

k

Permeation rate

Pa‐m/s

r

Radius

m

s

Turbomolecular pump blade spacing

m

s

r

Turbomolecular pump blade speed ratio

u

Local gas stream velocity

m/s

v

Average particle velocity

m/s

w

Length dimension

m

Γ

Particle flux

m

−2

‐s

−1

Δ

Free molecular heat conductivity

J‐s

−1

‐m

−2

‐K

−2

‐Pa

−1

α

Accommodation coefficient

β

Molecular slip constant

γ

Specific heat ratio

c

p

/c

v

δ

Kronecker delta function

ε

Emissivity

η

Dynamic viscosity

Pa‐s

λ

Mean free path

m

ξ

Volume to surface area ratio

π

Pi

ρ

Mass density

kg/m

3

τ

Vacuum system time constant

s

ϕ

Angle

deg

ω

Angular frequency; (heat transfer rate)

rad/s; (m/s)

Part IIts Basis

An understanding of how vacuum components and systems function begins with an understanding of the behavior of gases at low pressures. Chapter 1 discusses the nature of vacuum technology. Chapter 2 reviews basic gas properties. Chapter 3 describes the complexities of gas flow at near‐atmosphere and reduced pressures, and Chapter 4 discusses a most important topic: how gases evolve from and within material surfaces. Together, these chapters form the understanding of gauges, pumps, and systems that form the mainstay of vacuum technology as we know it today.

1Vacuum Technology

Torricelli is credited with the conceptual understanding of the vacuum within a mercury column by the year 1643. It is written that his good friend Viviani actually performed the first experiment, perhaps as early as 1644 [1,2]. His discovery was followed in 1650 by Otto von Guericke's piston vacuum pump. Interest in vacuum remained at a low level for more than 200 years, when a period of rapid discovery began with McLeod's invention of the compression gauge. In 1905, Gaede, a prolific inventor, designed a rotary pump sealed with mercury. The thermal conductivity gauge, diffusion pump, ion gauge, and ion pump soon followed, along with processes for liquefying helium and refining organic pumping fluids. They formed the basis of a technology that has made possible everything from incandescent light bulbs to space exploration. The significant discoveries of this early period of vacuum science and technology have been summarized in a number of historical reviews [2,3,4,5,6,7].

The gaseous state can be divided into two fundamental regions. In one region, the distances between adjacent particles are exceedingly small compared to the size of the vessel in which they are contained. We call this the viscous state because gas properties are primarily determined by interactions between nearby particles. The rarefied gas state is a space in which molecules are widely spaced and rarely collide with one another. Instead, they collide with their confining walls. Figure 1.1 sketches this behavior. This is an extremely important distinction that will appear in many discussions throughout this material.

A vacuum is a space from which air or other gas has been removed. Of course, it is impossible to remove all gas from a container. The amount removed depends on the application and is done for many reasons. At atmospheric pressure, molecules constantly bombard surfaces. They can bounce from surfaces, attach themselves to surfaces, and even chemically react with surfaces. Air or other surrounding gas can quickly contaminate a clean surface. A clean surface, e.g., a freshly cleaved crystal, will remain clean in an ultrahigh vacuum chamber for long periods of time, because the rate of molecular bombardment is low.

Fig. 1.1 View of a viscous gas and a rarefied gas.

Molecules are crowded closely together at atmospheric pressure and travel in every direction much like people in a crowded plaza. It is impossible for molecules to travel from one wall of a chamber to another without myriad collisions with others. By reducing the pressure to a suitably low value, molecules can travel from one wall to another without collision. Many things become possible if they can travel long distances without collisions. Metals can be evaporated from pure sources without reacting in transit. Molecules or atoms can be accelerated to a high energy and sputter away or be implanted in a surface. Electrons or ions can be scattered from surfaces and be collected. The energy changes they undergo on scattering or release from a surface are used to probe or analyze surfaces and underlying layers.

For convenience the sub‐atmospheric pressure scale has been divided into several ranges that are listed in Table 1.1. The ranges in this table are not so arbitrary; rather, they are a concise statement of the materials, methods, and equipment necessary to achieve the degree of vacuum needed for a given vacuum process.

The required degree of vacuum depends on the application. Reduced pressure epitaxy and laser etching of metals are two processes that are performed in the low vacuum range. Sputtering, plasma etching and deposition, low‐pressure chemical vapor deposition, ion plating, and gas filling of encapsulated heat transfer modules are examples of processes performed in the medium vacuum range.

Pressures in the high vacuum range are needed for the manufacture of low‐ and high‐tech devices such as microwave, power, cathode ray and photomultiplier tubes, light bulbs, architectural and automotive glass, decorative packaging, and processes including degassing of metals, vapor deposition, and ion implantation. A number of medium technology applications including medical, microwave susceptors, electrostatic dissipation films, and aseptic packaging use films fabricated in a vacuum environment [8]. Retail security, bank note security, and coated laser and inkjet papers are now included in this group.

Table 1.1 ISO Definition of Vacuum Pressure Ranges and Descriptions

Source: © ISO. This material is reproduced from ISO 3529‐1:2019 with permission of the American National Standards Institute (ANSI) on behalf of the International Organization for Standardization. All rights reserved.

Pressure Ranges

Definition

The reasoning for the definition of the ranges is as follows (typical circumstances):

Prevailing atm. pressure (31–110 kPa) to 100 Pa (232–825 to 0.75 Torr)

Low (rough) vacuum

Pressure can be achieved by simple materials (e.g., regular steel) and positive displacement vacuum pumps; viscous flow regime for gases

<100 to 0.1 Pa (0.75–7.5 × 10

−5

Torr)

Medium (fine) vacuum

Pressure can be achieved by elaborate materials (e.g., stainless steel) and positive displacement vacuum pumps; transitional flow regime for gases

<0.1–1 × 10

−6

Pa (7.5 × 10

−5

–7.5 × 10

−9

Torr)

High vacuum (HV)

Pressure can be achieved by elaborate materials (e.g., stainless steel), elastomer sealings, high vacuum pumps; molecular flow regime for gases

<1 × 10

−6

Pa–1 × 10

−9

Pa (7.5 × 10

−9

–7.5 × 10

−12

Torr)

Ultrahigh vacuum (UHV)

Pressure can be achieved by elaborate materials (e.g., low‐carbon stainless steel), metal sealings, special surface preparations and cleaning, bake‐out, and high vacuum pumps; molecular flow regime for gases

<1 × 10

−9

Pa (<7.5 × 10

−12

Torr)

Extreme‐high vacuum (EHV)

Pressure can be achieved by sophisticated materials (e.g., vacuum‐fired low‐carbon stainless steel, aluminum, copper–beryllium, and titanium), metal sealings, special surface preparations and cleaning, bake‐out, and additional getter pumps; molecular flow regime for gases

Note 1: While there has been some variation in the selection of limits for these intervals, the above list gives typical ranges for which the limits are to be considered approximations.

Note 2: The prevailing atmospheric pressure on ground depends on weather conditions and altitude and ranges from 31 kPa (altitude of Mount Everest, weather condition: “low”) up to 110 kPa (altitude of Dead Sea, weather condition: “high”).

The background pressure must be reduced to the very high vacuum range for electron microscopy, mass spectrometry, crystal growth, X‐ray and electron beam lithography, and storage media production. For ease of reading, we call the very high vacuum region “high vacuum” and its associated pumps “high vacuum pumps.”

Pressures in the ultrahigh vacuum range were formerly the domain of the surface analyst, materials researcher, or accelerator technologist. Today, critical high‐volume production applications, such as semiconductor devices, thin‐film media heads, and extreme UV lithography, require ultrahigh vacuum base pressures to reduce gaseous impurity contamination.

Yet another category of process takes place in the medium vacuum region using pure process gases and ultrahigh vacuum chamber starting conditions to maintain purity. Additionally, these processes must be free of particles. We call these systems ultraclean vacuum systems.

A vacuum system is a combination of pumps, valves, and pipes that creates a region of low pressure. It can be anything from a simple mechanical pump or aspirator for exhausting a vacuum storage container to a complex system such as an underground accelerator with miles of piping that must be held at an ultrahigh vacuum.

Removal of air at atmospheric pressure is usually done with a displacement pump, i.e., a pump that removes air from the chamber and expels it into the atmosphere. Rotary vane pumps are often used for this “rough pumping” purpose. Liquid nitrogen sorption pumps are used to rough pump ultraclean systems, such as those used for molecular beam epitaxy (MBE) that cannot tolerate even minute amounts of organic contamination. These pumps have finite gas sorption and require periodic regeneration.

Sorption pumps, as well as rotary vane and similar mechanical pumps, have low‐pressure limits in the range 10−1–10−3 Pa. Pumps that will function in a rarefied atmosphere are required to operate below this pressure range. The diffusion pump was the first high vacuum momentum transfer pump. Its outlet pressure is below atmosphere. The turbomolecular pump, a system of high‐speed rotating turbine blades, can also pump gas at low pressures. The outlet pressures of these two pumps need to be kept in the range 0.5–50 Pa, so they must exhaust into a mechanical “backing” pump, or “fore” pump. If the diffusion or turbomolecular pump exhaust gas flow would otherwise be too great, a lobe blower would be placed between the exhaust of the diffusion or turbo pump and the inlet of the rotary pump to pump gas at an increased speed in this intermediate pressure region.

Capture pumps can effectively remove gas from a chamber at low pressure. They do so by freezing molecules on a wall (cryogenic), chemically reacting with the molecules (gettering), or accelerating the molecules to a high velocity and burying them in a metal wall (ion pumping). Capture pumps are useful, efficient, and clean high vacuum pumps.

Air is the most important gas to understand because it is in every vacuum system. It contains at least a dozen constituents, whose major components are described in Table 1.2. The differing ways in which pumps remove air, and gauges measure its pressure, can be understood in terms of the partial pressures of its components. The concentrations listed in Table 1.2 are those of dry atmospheric air at sea level whose total pressure is 101,325 Pa (760 Torr). The partial pressure of water vapor is not given in this table, because it is not constant. At 20°C a relative humidity of 50% corresponds to a partial pressure of 1165 Pa (8.75 Torr), making it the third largest component of air. The total pressure changes rapidly with altitude, as shown in Fig. 1.2, whereas its proportions change slowly but significantly. In outer space, the atmosphere is mainly H2 with some He [10].

In the pressure region below 10 Pa, gases evolving from material surfaces contribute more flux to the total gas load than do the gases originally filling the chamber. A quality pump is not the only requirement to reach low pressures. The materials of construction, techniques for joining components, surface cleaning techniques, and operational procedures are all critically important. In the remaining chapters, the pumps, gauges, materials of construction, and operational techniques are described in terms of fundamental gas behavior. The focus is on the understanding and operation of vacuum systems and developing best practices for many applications.

Table 1.2 Components of Dry Atmospheric Air

Source: R.C. Weast [9]/Reproduced with permission of Taylor & Francis.

Constituent

Quantity

Pressure (Pa)

(vol%)

(ppm)

N

2

78.084 ± 0.004

79,117

O

2

20.946 ± 0.002

21,223

Ar

0.934 ± 0.001

946.357

CO

2

a

420

42.0

CH

4

2

0.203

Ne

18.18 ± 0.04

1.842

He

5.24 ± 0.004

0.51

Kr

1.14 ± 0.01

0.116

H

2

0.5

0.051

N

2

O

0.5 ± 0.1

0.051

Xe

0.087 ± 0.001

0.009

a Carbon dioxide data from NOAA Global Monitoring Laboratory, Mauna Loa, Hawaii, August 2023. Data since 1955 are publicly available at: https://gml.noaa.gov/ccgg/trends

Fig. 1.2 Relation between the atmospheric pressure and the geometric altitude.

R.C. Weast [9]/Reproduced with permission of Taylor & Francis.

1.1 Units of Measurement

Units of measurement present problems in many disciplines, and vacuum technology is no exception. Système International, more commonly known by its abbreviation, SI, is in worldwide use. (SI base units are given in Appendix A.2.) With the exception of the United Kingdom and the United States, the use of SI vacuum units is standard. However, noncoherent units such as the mbar (United Kingdom) and Torr (United States) remain in use.

The meter‐kilogram‐second (MKS) system was first introduced almost 75 years ago and became commonplace only after a decade or more of classroom education by instructors committed to change. In a similar manner, those who teach vacuum technique should lead the way and promote routine use of SI units. Metrology tools are manufactured for a global economy, and their readings can be displayed easily in several formats. The ease of displaying noncoherent units does not encourage change. The advantages of using a coherent unit system are manifold. Calculations become straightforward and logical, and the chance for error is reduced. Incoherent units are cumbersome, to say the least. One example is the permeation constant, which is the volume of gas (at standard temperature and pressure) per material thickness per material area per second. Additionally, noncoherent permeation units mask their relation to solubility and diffusion. Ultimately, SI units will be routinely used, but that will take time. To assist with this change, dual labels have been added throughout the text. SI units for pressure (Pa), time (s), and length (m) will be assumed in all formulas, unless noted differently within a formula statement.

References

1

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2Gas Properties

In this chapter we discuss the properties of gases at atmospheric and reduced pressures. The properties developed here are based on the kinetic picture of a gas. Kinetic theory has its limitations, but with it we are able to describe particle motion, pressure, effusion, viscosity, diffusion, thermal conductivity, and thermal transpiration of ideal gases. We will use these ideas as the starting point for understanding gas flow, surface reactions, gauges, pumps, and systems.

2.1 Kinetic Picture of a Gas

The kinetic picture of a gas is based on four assumptions: (1) The volume of gas under consideration contains a large number of molecules. For example, a cubic meter of gas at a pressure of 105 Pa (760 Torr) and a temperature of 22 °C contains 2.48 × 1025 molecules, whereas at a pressure of 10−7 Pa (10−5 Torr), a very high vacuum, it contains 2.5 × 1013