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SEMI C3.39-0304 © SEMI 1989, 2004 4 Table 1 Calibration C oncentrations Added Volume of Working Standard (ml) Total Volume (ml) Resulting F - Concentration (M) 0.2 100.2 1.0 × 10 -6 0.2 100.4 2.0 × 10 -6 0.4 100.8 4.0 × …

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

oncentrat

of Standard

oncentrat

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

)

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

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.

SEMI C3.39-0304 © SEMI 1989, 2004 4

Table 1 Calibration Concentrations

Added Volume of

Working Standard

(ml)

Total Volume

(ml)

Resulting F

Concentration (M)

0.2 100.2 1.0 × 10

-6

0.2 100.4 2.0 × 10

-6

0.4 100.8 4.0 × 10

-6

0.4 101.2 5.9 × 10

-6

0.8 102.0 9.8 × 10

-6

1.0 103.0 1.5 × 10

-5

2.0 105.0 2.4 × 10

-5

5.6.5.5 Put 50 ml 0.2 N NaOH into each of two

bubblers connected in series.

5.6.5.6 Establish a flow of < 1000 sccm of NF

through

the bubblers using a suitable flow controller or

flowmeter.

5.6.5.7 Sample approximately 15 liters of NF

. Record

flowrate and time of sampling to determine total

volume sampled (flowrate × time). A wet test meter

can also be used to measure total volume. The amount

of gas sample must be the volume at STP. If the

flowmeter or wet test meter is not reference to 0º and

760 torr, use the formula below to correct sample

volume.

K 273

273T

Torr 760

Liters Measured STPat Liters

××=

P: Pressure of sampled gas (mm Hg)

T: Temperature of sampled gas or reference

temperature of the flow controller or meter in ºC.

5.6.5.8 Transfer contents of each bubbler to individual

100 ml volumetric flasks and add 50 ml Buffer solution

to each. Then, if necessary, add deionized or distilled

water to bring the volume up to 100 ml.

5.6.5.9 Transfer contents to a plastic beaker.

5.6.5.10 While stirring, measure and record mV

readings for each sample.

5.6.5.11 Determine F

concentration in solution using

calibration curve generated in Section 5.6.5.4.

5.6.5.12 Calculate gas phase hydrolyzable fluoride

concentration using the equation below. Note that the

equation assumes the hydrolyzable fluoride is hydrogen

fluoride.

l/mole 22.4

0.11 C )(ppm HF Phase Gas ×××=

C: Measured hydrolyzable fluoride concentration (M)

determined in Section 5.6.5.11.

Vs: Volume of NF

sampled (liters at STP)

5.6.5.13 The HF concentration of the second bubbler

should be insignificant compared to the first bubbler. If

significant HF levels are found in the second bubbler,

resample with a lower flowrate.

5.7 Notes

NOTE 1: Pass the carrier gas through a trap (3 m (10 ft.) by

6.4 mm (1/4 in.) OD) containing 50% by volume molecular

sieve 5A and 50% by volume molecular sieve 13X submerged

in liquid nitrogen.

NOTE 2: The methanizer catalyst can be destroyed by

nitrogen trifluoride passing through to at high temperature.

After the carbon monoxide peak is detected, the bulk nitrogen

trifluoride is bypassed to vent by means of a four-port

switching valve installed downstream of the separating

column and before the methanizer (see Figure 1).

NOTE 3: The sampling system and hygrometer must be

designed to operate under the sample pressure, or the sample

pressure must be reduced, by a regulator with a diaphragm of

stainless steel or other suitable material, to accommodate the

pressure restrictions of the analytical hygrometer.

NOTE 4: A passivation procedure is described in the Metals

Handbook, 8th ed., Vol. 2, American Society for Metals,

Metals Park, OH.

NOTE 5: Polytetrafluoroethlyene, polymethylpentene and

polypropylene are suitable plastic materials.

Figure 1

Configuration for the Analysis of CF

, CO

, N

O, SF

, and CO in NF

Figure 2

Configuration for the Analysis of O

/Ar and N

in NF