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SEMI C3.39-0304 © SEMI 1989, 2004 2 5.2.2.3 Sample Vol ume: 1.0 m L. 5.2.2.4 Tem peratures: Detector 100° C Oven 42° C Gas sampling valve 42° C 5.2.2.5 Valve Material : Nitronic-60 or e quivalent. 5.2.3 Calibration Stand…
SEMI C3.39-0304 © SEMI 1989, 2004 1
SEMI C3.39-0304
STANDARD FOR NITROGEN TRIFLUORIDE (NF
3
)
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 October 16, 2003. Initially available at www.semi.org February 2004; to be published March
2004. Originally published in 1989; last published September 1999.
1 Description
1.1 Nitrogen trifluoride is a toxic, odorless, colorless,
nonflammable gas. It is a strong oxidizer and supports
combustion.
2 Specifications
2.1 QUALITY: 99.98%
Impurities Maximum Acceptable Level
(ppm) (see NOTE 1)
Carbon Dioxide (CO
2
) 10
Carbon Monoxide (CO) 10
Carbon Tetrafluoride (CF
4
) 100
Nitrogen (N
2
) 10
Nitrous Oxide (N
2
O) 10
Argon/Oxygen 10
Sulfur Hexafluoride (SF
6
) 10
Water (H
2
O) (v/v) 1
TOTAL IMPURITIES 161 (see NOTE 1)
NOTE 1: An analysis of significant figures has not been considered.
The number of significant figures will be based on analytical
accuracy and the precision of the provided procedure.
3 Chemical Specification
Hydrolyzable Fluorides as HF 1 ppm
4 Physical Constants (for information only)
Metric Units US Units
Molecular weight 71.00 71.00
Density of gas at 21.1° C
(70° F) and 1 atm
2.94 kg/m
3
0.1838 lb./ft.
3
5 Analytical Procedures
5.1 Carbon Tetrafluoride — This procedure is for the
determination of carbon tetrafluoride in nitrogen
trifluoride using a gas chromatograph with a thermal
conductivity detector. (See Figure 1 and Note 1.)
5.1.1 Detection Limit — 1.0 ppm.
5.1.2 Instrument Parameters
5.1.2.1 Column: Super Q (80/100 mesh), 4.9 m (16 ft.)
by 1.75 mm (1/16 in.) ID, 3.2 mm (1/8 in.) OD ss or
equivalent.
5.1.2.2 Carrier Flow: 19 mL/min helium.
5.1.2.3 Sample Volume: 0.1 mL.
5.1.2.4 Temperatures:
Detector 100° C
Oven 42° C
Gas sampling valve 42° C
5.1.2.5 Valve material: Nitronic-60 or equivalent.
5.1.3 Calibration Standard — 100 ppm carbon
tetrafluoride, balance helium.
5.1.4 Operating Procedure
5.1.4.1 Inject the calibration standard into the column
using a gas sampling valve. Record retention time and
peak area.
5.1.4.2 Inject nitrogen trifluoride sample to be tested in
the same manner as the calibration standard. Record the
retention times and peak areas.
5.1.4.3 Repeat Section 5.1.4.1.
5.1.4.4 Compare the average peak area of the
calibration standard to that of the nitrogen trifluoride
sample being tested. Calculate the concentration of
carbon tetrafluoride, using the formula below. The
result may not exceed the specification in Section 2 of
this standard.
Sample Peak Area
Standard Peak Area
×
C
oncentrat
i
on
of Standard
=
C
oncentrat
i
on
of Sample
5.2 Carbon Dioxide, Nitrous Oxide, and Sulfur
Hexafluoride — This procedure is for the determination
of carbon dioxide, nitrous oxide, and sulfur
hexafluoride in nitrogen trifluoride using a gas
chromatograph with a thermal conductivity detector.
(See Figure 1.)
5.2.1 Detection Limit — 1.0 ppm for carbon dioxide,
nitrous oxide, and sulfur hexafluoride.
5.2.2 Instrument Parameters
5.2.2.1 Column: Super Q (80/100 mesh), 4.9 m (16 ft.)
by 1.75 mm (1/16 in.) ID, 3.2 mm (1/8 in.) OD ss or
equivalent.
5.2.2.2 Carrier Flow: 19 mL/min helium.
SEMI C3.39-0304 © SEMI 1989, 2004 2
5.2.2.3 Sample Volume: 1.0 mL.
5.2.2.4 Temperatures:
Detector 100° C
Oven 42° C
Gas sampling valve 42° C
5.2.2.5 Valve Material: Nitronic-60 or equivalent.
5.2.3 Calibration Standard — 10 ppm carbon dioxide,
10 ppm nitrous oxide, 10 ppm sulfur hexafluoride,
balance helium.
5.2.4 Operating Procedure
5.2.4.1 Inject the calibration standard into the column
using a gas sampling valve. Record the retention times
and peak areas. The order of elution is carbon dioxide,
nitrous oxide, sulfur hexafluoride. (See Figure 1 for
valve configuration.)
5.2.4.2 Inject the sample to be tested in the same
manner as the calibration standard. Record the retention
times and peak areas.
5.2.4.3 Repeat Section 5.4.2.1.
5.2.4.4 Compare the average peak area of the
calibration standard to that of the nitrogen trifluoride
sample being tested. Calculate the concentration of each
impurity using the formula below. The results may not
exceed the specifications in Section 2 of this standard.
Sample Peak Area
Standard Peak Area
×
C
oncentrat
i
on
of Standard
=
C
oncentrat
i
on
of Sample
5.3 Carbon Monoxide — This procedure is for the
determination of carbon monoxide in nitrogen
trifluoride using a gas chromatograph with a methanizer
and a flame ionization detector. (See Figure 1 and Note
2.)
5.3.1 Detection Limit — 0.1 ppm.
5.3.2 Instrument Parameters
5.3.2.1 Column: Carbosphere (80/100 mesh), 0.74 m
(2.4 ft) by 1.75 mm (1/16 in) ID, 3.2 mm (1/8 in) OD ss
or equivalent.
5.3.2.2 Carrier Flow: 25 mL/min helium.
5.3.2.3 Sample Volume: 0.5 mL.
5.3.2.4 Fuel gases:
Hydrogen: Zero grade or better hydrogen at a flow rate of
45 mL/min is added to the carrier gas between
the column outlet and the methanizer inlet.
Air: Zero grade or better air is used at a flow rate o
f
300 mL/min.
5.3.2.5 Temperatures:
Detector 150° C
Oven 42° C
Methanizer 340° C
Gas sampling valve 70° C
5.3.2.6 Valve Material: Nitronic-60 or equivalent.
5.3.3 Calibration Standard — 10 ppm carbon
monoxide, balance helium.
5.3.4 Operating Procedure
5.3.4.1 Inject the the calibration standard into the col-
umn using a gas sampling valve. Record the retention
time and peak area.
5.3.4.2 Inject the sample to be tested in the same
manner as the calibration standard. Record the retention
time and peak area.
5.3.4.3 Repeat Section 5.3.4.1.
5.3.4.4 Compare the average peak area of the cali-
bration standard to that of the nitrogen trifluoride sam-
ple being tested. Calculate the concentration of carbon
monoxide, using the formula below. The result may not
exceed the specification in Section 2 of this standard.
Sample Peak Area
Standard Peak Area
×
C
oncentrat
i
on
of Standard
=
C
oncentrat
i
on
of Sample
5.4 Oxygen + Argon, Nitrogen — This procedure is for
the determination of oxygen + argon and nitrogen in
nitrogen trifluoride using a gas chromatograph with a
thermal conductivity detector. (See Figure 2 and Note
1.)
5.4.1 Detection Limit — 5 ppm of oxygen + argon and
nitrogen.
5.4.2 Instrument Parameters
5.4.2.1 Column: Molecular sieve 13X (80/100 mesh),
6.1 m (20 ft) by 1.75 mm (1/16 in) ID, 3.2 mm (1/8 in)
OD ss or equivalent.
5.4.2.2 Carrier Flow: 17 mL/min helium.
5.4.2.3 Sample Volume: 1.0 mL.
5.4.2.4 Temperatures:
Detector 140° C
Filament 240° C
Oven 100° C
Gas sampling valve 60° C
5.4.2.5 Valve Material: Nitronic-60 or equivalent.
5.4.3 Calibration Standard — 10 ppm oxygen, 10 ppm
nitrogen, balance helium.
SEMI C3.39-0304 © SEMI 1989, 2004 3
5.4.4 Operating Procedure
5.4.4.1 Inject the calibration standard into the column
using a gas sampling valve. Record the retention times
and peak areas. The order of elution is oxygen + argon
(not separated) and nitrogen.
5.4.4.2 Inject the sample to be tested in the same
manner as the calibration standard. Record the retention
times and peak areas.
5.4.4.3 Repeat Section 5.4.4.1.
5.4.4.4 Compare the average peak area of the
calibration standard to that of the nitrogen trifluoride
sample being tested. Calculate the concentrations of
oxygen + argon and nitrogen, using the formula below.
The results may not exceed the specifications in Section
3 of this standard.
Sample Peak Area
Standard Peak Area
×
C
oncentrat
i
on
of Standard
=
C
oncentrat
i
on
of Sample
5.5 Water — This procedure is for the determination of
trace moisture (water) in nitrogen trifluoride using a
continuous flowing piezoelectric hygrometer. (See
Notes 3 and 4.)
5.5.1 Detection Limit — 0.04 ppm (vol/vol) or -95° C (-
139° F).
5.5.2 Flow Requirements — Set the sample pressure
and flow rate set in accordance with the instrument
manufacturer’s instructions.
5.5.3 Calibration Standards — Construct a calibration
curve which contains at least three points covering the
range of interest. Verify the standards employed by
another analytical method.
5.5.4 Operating Procedure
5.5.4.1 Obtain a continuous flow of sample gas from
the source using a clean and passivated 316 stainless
steel line which has been purged dry after exposure to
ambient moisture.
5.5.4.2 After prepurging with a dry gas, allow the
sample as to flow through the sampling system and the
piezoelectric hygrometer until a stable reading is
obtained. The result may not exceed the specification in
Section 2 of this standard.
5.6 Hydrolyzable Fluorides as HF This procedure is
for the determination of hydrolyzable fluorides in
nitrogen trifluoride using fluoride ion selective
electrode.
5.6.1 Detection Limit Detection limits should be
checked for any new implementation of a method.
Detection limits below 0.1 ppm have been determined
with this method. Detection limits can be improved by
increasing the volume of gas sampled.
5.6.2 Equipment
5.6.2.1 mV meter (0.1 mV scale)
5.6.2.2 Reference electrode (single junction type)
5.6.2.3 Fluoride ion selective electrode
5.6.2.4 Magnetic stir bars (PTFE coated)
5.6.2.5 Magnetic stirrer
5.6.2.6 Plastic beakers (See NOTE 5.)
5.6.2.7 PTFE bubblers
5.6.2.8 1000 ml and 100 ml plastic volumetric flasks
(see NOTE 5).
5.6.2.9 0.2 ml and 1 ml plastic volumetric pipettes (see
NOTE 5).
5.6.2.10 Flow controller or flowmeter (0–1000 sccm
NF
3
)
5.6.3 Reagents
5.6.3.1 Distilled or deionized water
5.6.3.2 5 N sodium hydroxide
5.6.3.3 0.2 N sodium hydroxide
5.6.3.4 Glacial acetic acid
5.6.3.5 Buffer Solution To 500 ml distilled or
deionized water in a 1000 ml volumetric flask, add 57
ml glacial acetic acid and 58 g of sodium chloride.
Adjust the pH to between 5.0–5.5 with 5 M sodium
hydroxide. Cool to room temperature. Dilute to one
liter with distilled or deionized water.
5.6.4 Calibration Standard — Sodium fluoride
standard (10
-3
M F
-
in water, freshly prepared)
5.6.5 Operating Procedure
5.6.5.1 Prepare working standard by adding 100 ml 10
-
3
M F
-
to 100 ml buffer solution.
5.6.5.2 Prepare a blank containing 50.0 ml 0.2 N
NaOH and 50.0 ml buffer solution in a plastic beaker.
5.6.5.3 While stirring blank gently, record mV reading
from the blank once reading is stable.
5.6.5.4 Successively add increments of working
standard to the blank to generate a calibration curve.
Record stable mV reading after each addition. Table 1
shows recommended increments and resultant
concentrations.