Vacuum Metrology for Science and Industry
Karl Jousten, PTB, Berlin
1. Applications of vacuum and leak detection
2. Traceability and primary standards for vacuum and
low flow rates (leaks)
3. Secondary and reference standards
4. New developments and future challenges
VS4, Coventry, UK, October 2013, Karl Jousten 1
Applications of vacuum and leak detection
VS4, Coventry, UK, October 2013, Karl Jousten 2
Nobel Prize 2013: Peter Higgs and Francoise Englert
Francois Englert (left) and Peter Higgs on July 4,
2012 at CERN
Image: Maximilien Brice/CERN
Break-up of a Higgs Boson, CMS detector,
LHC, CERN
Image: CERN
Applications of vacuum and leak detection
VS4, Coventry, UK, October 2013, Karl Jousten 3
This was not possible without vacuum engineering:
LHC, 27 km, CERN
•3 huge vacuum systems,
for beam, for
superconducting magnets,
for helium distribution line:
104 km long, 15 000 m³
•2 times 27 km UHV < 10-8
Pa
• 250 000 welded joints
• 18 000 seals
• NEG coated walls
• 780 ion pumps
• 1084 Pirani and Penning
gauges
• 170 BAG
Vessel height 10.2m
Vacuum volume ~ 1330m3
Plasma volume ~ 837m3
Cryostat volume: 14 000m3
Hydrogen/isotopes: < 10-5 Pa
Other impurities: < 10-7 Pa
Total leak rate Torus: < 10-7 Pa m3/s
29 m
28.5 m
In the search for new energy: ITER
Applications of vacuum and leak detection
VS4, Coventry, UK, October 2013, Karl Jousten 4
Microelectronic industry: no UHV/bake-out
Applications of vacuum and leak detection
MOCVD: Reactor for
ferroelectric films
Cluster tool
VS4, Coventry, UK, October 2013, Karl Jousten 5
Industrial applications: CD/DVD metallization
Type Cathode Pumps Cycle-time
SINGULUS V
Focus 1
Focus Cathode 1 Turbo Molecular
Pump
2,7 s
SINGULUS V
Focus 2
Focus Cathode 2 Turbo Molecular
Pumps
1,5 s
SINGULUS V
Smart 1
SMART
CATHODE®
1 Turbo Molecular
Pump
2,5 s
SINGULUS V
Smart 2
SMART
CATHODE®
2 Turbo Molecular
Pumps
1,9 s
Applications of vacuum and leak detection
VS4, Coventry, UK, October 2013, Karl Jousten 6
Introduction
Typical distribution of leaks in industrial products
mbar L/s
Majority of products
Geometrical leaks
Permeation leaks
Courtesy M. Bergoglio
Applications of partial pressure measurement:
• Gas purity (Semi)
• Residual gases
• In-situ analysis for reagent gases
• Outgassing rate measurement (EUV-Lithography)
• Sputter process control
• CVD monitoring, gas abatement analysis
• MBE source control
• End point detection (etching)
• Gas chromatography
EUV Lithography
Applications of vacuum and leak detection
VS4, Coventry, UK, October 2013, Karl Jousten 8
1. For now 150 years vacuum technology is
one of the basics for physical experiments
and progress in industrial technology, from
high-tech-industry to food packaging.
2. This will persist (microelectronic-industry)
and grow (solar cells, EUV lithography,
nanotechnology, life sciences, new
materials, optical computer, quantum
computer)!
Turnover 2008: worldwide 6 Mrd $/a.
Conclusions from applications
VS4, Coventry, UK, October 2013, Karl Jousten 9
3. As mature vacuum techniques are, as reliable vacuum measurement should be. All vacuum gauges need a calibration (at least by the manufacturer).
4. Fast processes are required
5. Leak testing: Traceability for low flow rates become more and more important.
6. Materials testing: Traceability and standardization of outgassing rate measurements become important.
7. Surface science/X-ray lasers: XHV is a niche, but also important
Conclusions from applications
VS4, Coventry, UK, October 2013, Karl Jousten 10
Traceability and vacuum primary standards
What is traceability (Vocabulary International Metrology)?
Property of a measurement result whereby the result can be
related to a reference through a documented unbroken chain of
calibrations, each contributing to the measurement uncertainty.
As reference serve the primary standards:
Measurement standard established using a primary reference
measurement procedure, or created as an artifact, chosen by
convention.
Primary reference measurement procedure is used to obtain a
measurement result without relation to a measurement standard
for a quantity of the same kind (in the same range).
VS4, Coventry, UK, October 2013, Karl Jousten 11
working standard
secondary standard
primary
standard
Calibration chain and uncertainties
ordinary vacuum gauge
22sec, calprimcert uuu
2sec,
22sec,sec callstcert uuuu 2
,2sec, calworkcertwork uuu
2,
22, calworklstcertworkwork uuuu
2,
2, calordworkcertord uuu
2,
22, calordlstcertordord uuuu
primu
Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 13
Relative uncertainties of pressures in primary standards
2E-021E-02
5E-034E-03
2E-03
3E-04
5E-05
2E-05
6E-06 5E-06
1E-06
1E-05
1E-04
1E-03
1E-02
1E-01
1E+00
1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04 1E+06
p in Pa
Re
lati
ve
Un
ce
rta
inti
es
(k=
2)
Mercury Manometer
Continuous expansion Series expansion
p atm
Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 14
Singapore
Mexiko
Fully developed primary standards down to high vacuum
National standards down to high vacuum
Traceability and vacuum primary standards
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Secondary laboratories
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Secondary labs
• Use secondary standards as reference (calibration by
comparison)
• Are accredited by a National Body (technical
accreditation of their calibration procedure)
• Work according to ISO 17025 and in vacuum in
addition according to ISO 3567 and 27893
• Distribute the scale more economically to the end user
• High
accuracy
• Good long
term stability
• Good
transport
stability
Reference gauges
Secondary and reference standards
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10 5
10 2
10 -1
10 -5
10 -7
Rough vacuum Fine vacuum high vacuum Ultra high vacuum
p in Pa
Quartz Bourdon gauge
Resonance silicon gauge
Capacitance diaphragm gauge
Ionization gauge
Spinning rotor gauge
Lowest relative uncertainties for vacuum gauges and primary standards
.
1
0,2
0,05
0,02
0,05
0,1
0,01
0,005 0,0040,0040,003
0,002
0,001
0,1
0,01
0,02
0,01
0,02
1E-06
1E-05
1E-04
1E-03
1E-02
1E-01
1E+00
1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04 1E+06
p in Pa
Re
lati
ve
Un
ce
rta
inti
es
(k=
2)
Mercury Manometer
Continuous expansion Series expansion
p atm
Ionisation gauge Membrane
(mechanical)
Piston
QBS
CDG
SRGPirani
RSG
Secondary and reference standards
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Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 19
Leak rate threshold
Vacuum
Hood filled with known concentration of tracer gas
Test piece communicating with leak detector
Leak detector sensitive to tracer gas
pressure
Vacuum Test piece pressurized with tracer gas
Leak detector sensitive to tracer gas
Choose appropriate leak test method
Leak test (quantitative)
Standard leak (Validates your leak test)
Geometrical standard leak (capillaries)
Permeation standard leak
Written standards EN 1518, 1779, 13184, 13185,13192 ISO 3530, 27895 AVS practice (1992)
Traceability and vacuum primary standards
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The standard leak enables the user
• To validate the applied method
• To verify and calibrate the reading of a leak detector
• Perform accurate measurements in-situ
Written standards require that
• The standard leak is calibrated (traceability to a primary standard)
• There is an uncertainty associated with the specified leak rate
Calibration/Traceability:
Reference leak
for leak detector
Secondary
standard leak
Primary flow
meter
Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 21
Several types of gas flow measurement in vacuum metrology:
• pressure rise technique
• defined volume change, fixed pressure
• flowmeter (constant pressure, variable volume)
V
t
p
t
Vp
t
pVq pV
Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 22
p=const
t
p
Gas Flow
C
V
Gas Inlet
V1
V2
V3
"Leak"
CDG
t
Vpq pV
RT
pV
Temperature
stability !
PTB primary flowmeter (1E-8 Pa L/s…1E-2 Pa L/s)
Traceability and vacuum primary standards
Valve 1
Testleak
Valve 3
Enclosure T=const.
(necessary for permeation leaks)
Flowmeter
Valve 2
QMS
VS4, Coventry, UK, October 2013, Karl Jousten 23
PTB measurement standard for vacuum standard test leaks
(1E-8 Pa L/s…1E-2 Pa L/s)
Traceability and vacuum primary standards
Testleak
Needle
CDG 133 Pa FS
CDG 133 kPa FS T1
T3
T2
T4
V1
V2
V3
V = 5.1 cm³
V = 6.1 cm³ Thermal insulation
VS4, Coventry, UK, October 2013, Karl Jousten 24
PTB measurement standard for sniffer test leaks against atmosphere
Metre Convention (1875)
General Conference on Weights and Measures (CGPM)
every 4 years
International Committee for Weights and Measures (CIPM)
18 individuals elected by CGPM
10 Consultative Committees (CCs)
each chaired by a member of CIPM
Working Groups (WG)
Diplomatic Treaty
Governments of
member states
International
Organizations
National
Metrological
Institutes (NMI)
International Bureau of Weights and
Measures (BIPM, Sevres, France)
CIPM MRA (1999)
Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 25
The Mutual Recognition Arrangement (MRA) of the CIPM
• to provide for the mutual recognition of calibration and measurement certificates issued by NMIs
by
• international comparisons of measurements, to be known as key comparisons, and as well supplementary international comparisons (http://www.bipm.org/kcdb)
• demonstration of competence by NMIs by publishing their calibration measurement capabilities
• establish an internationally accepted quality system in each NMI.
Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 26
Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 27
CCM.P-K12 (key comparison for leak rate measurement, 2012):
Transfer standards
Reservoir cannot
be refilled
Two helium permeation leaks:
4·10-11 mol/s (1·10-4 Pa L/s, 23°C) and 8·10-14 mol/s (2·10-7 Pa L/s),
no clogging, long-term stable, but decreasing rate
Temperature coefficient about 4%/K
Traceability and vacuum primary standards
VS4, Coventry, UK, October 2013, Karl Jousten 28
Results of CCM.P-K12 (key comparison for leak rate measurement, 2012)
Dj
j
nu
DE
2
. mol/s10)0249.03746.4( 11
1,
q
New developments
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High
pressure
volume
Low pressure
volume
Fast
opening
valve
Dynamic vacuum standard for rough vacuum at PTB
New developments : dynamic vacuum standard
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Pressure step
Future developments
VS4, Coventry, UK, October 2013, Karl Jousten 31
• On its way: Vacuum metrology for production environments (EMRP
IND12, 2011-2014)
– Work package 2 „Leak measurement and testing“
Task 1: Leak elements with defined geometry
Task 2: Improvement of the theory of flow in narrow ducts
Task 3: Leak elements performance (environmental conditions)
Task 4: Development of a practical guide on metrological performance of
leak detectors
Task 5: Feasibility study on alternative methods than mass spectrometer
leak detector to detect leaks within few seconds
Future developments
VS4, Coventry, UK, October 2013, Karl Jousten 32
• On its way: EMRP IND12 – Work package 3 „Partial pressure and outgassing rate measurement “ Triggered by EUV-Lithography
• Written standards for vacuum gauge calibrations and perhaps design for ionization gauges
• Written standards for QMS calibration and outgassing rate measurements
• Furter developments of optical methods for vacuum measurement, also for leak testing
• Developments for harsh environments like Fusion (tritium, magnetic fields,…)
• XHV (but niche)
EUV-Lithography
Conclusion
• Traceable calibrations are more important than 20 years ago.
• Primary standards are available world wide.
• An international validation scheme ensures equivalence of vacuum gauge
and leak rate calibrations world wide.
• Reasonable secondary gauges for full vacuum range except for low HV
and UHV.
• Written standards are in progress and shall transform our present
knowledge into long-lasting practical solutions. Need to be extended for
partial pressure and outgassing rate measurement.