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SEMI C3.52-02 00 © SEMI 1995 , 2000 1 SEMI C3.52-0200 STANDARD FOR TUNGSTEN HEXA FLUORIDE, 99.996% QUALITY This s tandard w as technica lly approve d by the Global G a ses Committe e and is the dire ct responsi bility of…
SEMI C3.26-0301 © SEMI 1984, 20013
H
elium
C
arrier
Porapak
Column
Vent
Sample
Out
Sample In
T.C.
DET
Position 1:
• Sample is purging through loop
• Porapak S column is backflushing
• MS5A column connected to detector
MS5A
Column
Position 2:
• V1 is turned
• Sample flows through sample loop to the
Porapak S column and then to MS5A column
Figure 2
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SEMI C3.52-0200 © SEMI 1995, 20001
SEMI C3.52-0200
STANDARD FOR TUNGSTEN HEXAFLUORIDE, 99.996% QUALITY
This standard was technically approved by the Global Gases Committee and is the direct responsibility of the
North American Gases Committee. Current edition approved by the North American Regional Standards
Committee on December 15, 1999. Initially available at www.semi.org February 2000, to be published
February 2000. Originally published in 1995; previously published in 1996.
1 Purpose
1.1 To define the specification and analytical methods
and validate the specifications for WF
6
.
2 Scope
2.1 This specification relates to a geometry of 0.5 µ or
less (0.35 or 0.5 range) and describes analytical
techniques using gas phase and liquid phase analysis.
3 Description
3.1 Tungsten hexafluoride is a colorless, odorless gas
or a clear liquid.
4 Specifications
Quality: 99.996%
Impurities Maximum Acceptable
Level
Oxygen (O
2
) & Argon (Ar) 1 ppm
Nitrogen (N
2
)5 ppm
Carbon Dioxide (CO
2
)1 ppm
Carbon Tetrafluoride (CF
4
)1 ppm
Hydrogen Fluoride (HF) 20 ppm
Silicon Tetrafluoride (SiF
4
)1 ppm
Sulfur Hexafluoride (SF
6
)1 ppm
Carbon Monoxide (CO) 1 ppm
TOTAL SPECIFIED IMPURITIES 31 ppm
Impurities Maximum Acceptable
Level
Cobalt (Co) & Manganese (Mn) 0.01 ppm w
Lead (Pb) 0.02 ppm w
Chromium (Cr), Zinc (Zn), &
Uranium (U)
0.05 ppm w
Calcium (Ca) & Magnesium (Mg) 0.10 ppm w
Nickel (Ni), Copper (Cu), Sodium
(Na), & Potassium (K)
0.15 ppm w
Iron (Fe) 0.02 ppm w
Thorium (Th) 0.1 ppm w
Molybdenum (Mo) 1 ppm w
5 Physical Constants
Metric Units U. S. Units
Molecular weight 297.85 297.85
Boiling point 17.1°C 62.8°F
Density of gas at 22.8°C (73°F)
and 1 atm
12.9 kg/m
3
0.805 lb/ft
3
Specific gravity of gas 10.8 10.8
Density of liquid at boiling point 3440 kg/m
3
6 Analytical Procedures (se e NOTE 1)
6.1 Carbon Tetrafluoride, Silicon Tetrafluoride,
Carbon Dioxide, and Sulfur Hexafluoride — This
procedure is for the determination of carbon
tetrafluoride, silicon tetrafluoride, carbon dioxide, and
sulfur hexafluoride in tungsten hexafluoride using a gas
chromatograph equipped with a helium ionization
detector. A backflush is used in order to protect the
detector from the main component.
6.1.1 Detection Limits — 0.3 ppm (mole/mole) carbon
tetrafluoride, 1 ppm (mole/mole) silicon tetrafluoride,
0.1 ppm (mole/mole) carbon dioxide, and 0.5 ppm
(mole/mole) sulfur hexafluoride.
6.1.2 Instrument Parameters
6.1.2.1 Columns:
Column 1: 10% Kel F Nr10 on Chromosorb T, 4.0 m
(13 ft) by 3.2 mm (1/8 in) nickel or
equivalent,
Column 2: Preconditioned HAYESEP Q, 60/80 mesh, 3
m (10 ft) by 3.2 mm (1/8 in) or equivalent.
The column should be treated by repeated
WF
6
sample injections at 125°C.
6.1.2.2 Carrier Flow — 26 mL/min helium, 6.0 grade.
6.1.2.3 Temperatures:
Detector 50°C
Column Oven 50°C
6.1.2.4 Sample Volume — 2 mL
6.1.2.5 Calibration Standards — 1 and 5 ppm
(mole/mole) carbon tetrafluoride, carbon dioxide, and
sulfur hexafluoride in helium (see Figures 1 and 2).
SEMI C3.52-0200 © SEMI 1995, 2000 2
10 ppm silicon tetrafluoride in helium or permeation
device (see Figure 3).
6.1.3 Operating Procedure
6.1.3.1 Attach a suitable pressure regulator to the
standard cylinders. Connect the regulator to the
dedicated WF
6
handling system which is connected to
the chromatographic sampling valve.
6.1.3.2 Purge the sampling lines with the standard for
at least one minute.
6.1.3.3 Inject the standard into the gas chromatograph.
Record the retention times and peak areas. Order of
elution for the above mentioned standard is carbon
tetrafluoride, silicon tetrafluoride, carbon dioxide, and
sulfur hexafluoride.
6.1.3.4 Inject the WF
6
sample to be analyzed in the
same manner as the calibration standard. Record the
retention times and peak areas.
6.1.3.5 Compare the average peak areas of the
calibration standard to that of the detected peak in
tungsten hexafluoride. Calculate the concentration of
each impurity using the standard and sample peak areas
and the standard concentration. The results may not
exceed the specifications.
6.2 Oxygen and Argon, Nitrogen, and Carbon
Monoxide — This procedure is for the determination of
oxygen and argon, nitrogen, and carbon monoxide in
tungsten hexafluoride using a gas chromatograph
equipped with a helium ionization detector. A backflush
is used in order to protect the detector from the main
component.
6.2.1 Detection Limits
6.2.2 Instrument Parameters
6.2.2.1 Columns:
Column 1: 10% Kel F Nr 10 on Chromosorb T, 4.0 m (13 ft)
by 3.2 mm (1/8 in) nickel or equivalent.
Column 2: Preconditioned HAYESEP Q, 60/80 mesh, 3 m
(10 ft) by 3.2 mm (1/8 in) or equivalent. The
columns should be treated by repeated WF
6
sample injections at 125°C.
Column 3: Molecular sieve 5 A, 60/80 mesh, 2 m (6 ft) by
3.2 mm (1/8 in).
6.2.2.2 Carrier Flow — 26 mL/min helium, 6.0 grade.
6.2.2.3 Temperatures:
Detector 50°C
Column Oven 50°C
6.2.2.4 Sample Volume — 2 mL
6.2.2.5 Calibration Standards — 1 and 5 ppm
(mole/mole) oxygen, nitrogen, and carbon monoxide in
helium (see Figure 4).
6.2.3 Operating Procedure
6.2.3.1 Attach a suitable pressure regulator to the
standard cylinder. Connect the regulator to the
dedicated WF
6
handling system, which is connected to
the chromatographic sampling valve.
6.2.3.2 Purge the sampling lines with the standard for
at least one minute.
6.2.3.3 Inject the standard into the gas chromatograph.
Switch the valves in order to operate in the same
conditions as the WF
6
sample analysis. Record the
retention times and peak areas. Order of elution for the
above mentioned standard is oxygen and argon,
nitrogen, and carbon monoxide.
6.2.3.4 Inject the WF
6
sample in the same manner as
the calibration standard. Record the retention times and
peak areas.
6.2.3.5 Compare the average peak areas of the
calibration standard to that of the detected peak in the
tungsten hexafluoride. Calculate the concentration of
each impurity using the standard and sample areas and
the standard concentration. The results may not exceed
the specifications.
6.3 Hydrogen Fluoride — This procedure is for the
determination of hydrogen fluoride in tungsten
hexafluoride using Fourier Transform Infra Red (FTIR)
analyzer.
6.3.1 Detection Limit — 0.5 ppm (mole/mole).
6.3.2 Instrument Parameters
• cell with CaF
2
windows
• HF band: 4038,8 cm
-1
• resolution: 2 cm
-1
• path length: 12 cm
6.3.3 Calibration Standard — Calibrate with low
vapor pressure hydrogen fluoride or permeation device.
6.3.4 Operating Procedure — Carefully dry the cell
before sampling tungsten hexafluoride. Then purge it
with tungsten hexafluoride and record the
concentration. When it is steady, that means the line is
purged and the true hydrogen fluoride concentration is
obtained.
6.4 Elemental Impurities — This procedure is for the
determination of Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Mo,
Na, Ni, Pb, Th, U, and Zn in the nonvolatile residue of
liquid phases tungsten hexafluoride (WF
6
) and analyzed