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SEMI C3.26-03 01 © SEMI 1984 , 2001 3 H elium C arrier Por apa k Col umn Ven t Sampl e Out Sam ple In T.C. DET P o sit i o n 1: • S a m p l e i s p u rgi n g t h ro ug h l o op • P o r a p ak S co l u m n is bac k f l u …
SEMI C3.26-0301 © SEMI 1984, 2001 2
4.1.4.4 Flow the sample to be tested through the 10-
port valve for 1 minute. Analyze in the same manner as
in 4.1.4.3.
4.1.4.5 The standard is again run as in 4.1.4.3.
4.1.4.6 Calculate the concentrations of nitrogen and
oxygen + argon in the sample, using the formula below.
The result may not exceed the specifications in Section
2 of this Standard.
Sample Peak Area
Standard Peak Area
×
Concentratio
n
of Standard
=
Concentratio
n
of Sample
4.2 Carbon Tetrafluoride, Hydrogen Fluoride, Silicon
Tetrafluoride, and Sulfur Hexafluoride — This
procedure is for the determination of these gases in
tungsten hexafluoride using infrared
spectrophotometry. (See Note 2.)
4.2.1
Detection Limits — 10 ppm (mol/mol) carbon
tetrafluoride, 1000 ppm (mol/mol) hydrogen fluoride,
10 ppm (mol/mol) silicon tetrafluoride and 10 ppm
(mol/mol) sulfur hexafluoride.
4.2.2
Instrument Parameters
4.2.2.1 Cell path length: 10 cm
4.2.2.2 Sample Cell Pressure: 1 atmosphere
4.2.2.3 Wavenumbers:
Component Wavenumber (cm
-1
)
Carbon Tetraflouride (CF
4
) 1283
Hydrogen Fluoride (HF) 4076
Silicon Tetrafluoride (SiF
4
) 1029
Sulfur Hexafluoride (SF
6
) 948
4.2.3 Calibration Standards — 1% (mol/mol)
hydrogen fluoride in tungsten hexafluoride, 100 ppm
(mol/mol) silicon tetrafluoride in nitrogen, 25 ppm
(mol/mol) each carbon tetrafluoride and sulfur
hexafluoride in nitrogen.
4.2.4
Operating Procedures
4.2.4.1 Flow each calibration gas through the system
for 1 minute. Pressurize the cell to 1 atmosphere.
Record the absorbance of each calibration standard at
the wavenumber listed in 4.2.2.3.
4.2.4.2
Flow the sample gas through the system for 1
minute. Pressurize the cell to 1 atmosphere. Record the
absorbance at each of the appropriate wavenumbers.
Calculate (See Note 1) the concentration of each gas,
using the formula below. The results may not exceed
the specification in Section 2 of this standard.
Sample of
ionConcentrat
Standard of
ionConcentrat
Standard theof
Absorbance Measured
Sample theof
Absorbance Measured
=×
4.3 Notes
NOTE 1: Tungsten hexafluoride interferes with the direct
absorbance reading for silicon tetrafluoride. The absorbance
for silicon tetrafluoride is determined by compensating for the
interfering absorbance from the tungsten hexafluoride.
Compensation is made by subtracting the absorbance
contributed to this band by tungsten hexafluoride band at 930
cm
-1
. This absorbance is halved and subtracted from the total
peak absorbance at 1040 cm
-1
, resulting in the peak
absorbance for silicon tetrafluoride.
NOTE 2: Actual detection limits will be determined by the
noise level and the resolution of the spectrometer. One way is
to reduce the noise level is to use a Fourier Transform
Infrared Spectrometer.
NOTE 3: All gases used in the analysis of the sample should
not contain more than 10% of the specified value of the
component of interest, unless otherwise stated.
NOTE 4: As tungsten hexafluoride has a low vapor pressure,
the cylinder should be kept at room temperature (20°C) for at
least 8 hours prior to analysis.
NOTE 5: Observe proper safety procedures for handling and
disposing of tungsten hexafluoride.
NOTE 6: Prior to introducing tungsten hexafluoride purge the
sample lines and instrument tubing with helium to remove
moisture.
NOTE 7: Upon completing the analysis, cap off the manifold
and instrument lines or purge the system with helium.
Figure 1
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
NOTICE: These standards do not purport to address
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appropriate safety and health practices and determine
the applicability of regulatory limitations prior to use.
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particular application. The determination of the
suitability of the standard is solely the responsibility of
the user. Users are cautioned to refer to manufacturer’s
instructions, product labels, product data sheets, and
other relevant literature respecting any materials or
equipment mentioned herein. These standards are
subject to change without notice.
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compliance with this standard may require use of
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takes no position respecting the validity of any patent
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of such rights, are entirely their own responsibility.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o
f
the contents in whole or in part is forbidden without express written
consent of SEMI.
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).