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SEMI C3.40-10 00 © SEMI 1989 , 2000 4 5.6.2.3 Flu o ride ion selective electrod e 5.6.2.4 Mag netic stir bars (PTFE coat e d ) 5.6.2.5 Magnetic stirre r 5.6.2.6 Plastic beak ers (See note 5) 5.6.2.7 P T FE bubblers 5.6.2…

SEMI C3.40-1000 © SEMI 1989, 20003

5.3.4.2 Purge the sampling lines with the standard for

at least one minute.

5.3.4.3 Pressurize the sampling lines to 5 psig.

5.3.4.4 Inject the standard into the gas chromatograph,

and start the scan. Record the retention times and peak

areas. Order of elution for the above mentioned

standard is carbon tetrafluoride, trifluoromethane,

hexafluoroethane, chlorotrifluoromethane, and

dichlorodifluoromethane.

5.3.4.5 Inject the sample to be tested in the same

manner as the calibration standard.

5.3.4.6 Repeat 5.3.4.1–5.3.4.4.

5.3.4.7 Compare the average peak areas of the

calibration standard to those of the carbon tetrafluoride

sample being tested. Calculate the concentration of each

of the impurities using the formula below. The results

may not exceed the specifications in Section 2 of this

Standard.

Sample Peak Area

Standard Peak Area

Concentration

of Standard

Concentration

of Sample

5.4 Sulfur Hexafluoride — This procedure is for the

determination of sulfur hexafluoride in carbon

tetrafluoride using a gas chromatograph with a thermal

conductivity detector. (See Figure 2.)

5.4.1 Detection Limit — 0.5 ppm.

5.4.2 Instrument Parameters

5.4.2.1 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.

5.4.2.2 Carrier Flow: 19 mL/min helium.

5.4.2.3 Temperatures:

Detector 100°C

Oven 70°C

Gas sampling valve 70°C

5.4.2.4 Sample Volume: 1 mL.

5.4.3 Calibration Standard — 1 ppm sulfur

hexafluoride, balance helium.

5.4.4 Operating Procedures

5.4.4.1 Inject the calibration standard into the column

using a gas sampling valve. Record retention time and

peak area.

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 5.4.4.1.

5.4.4.4 Compare the average peak areas of the

calibration standard to those of the carbon tetrafluoride

sample being tested. Calculate the concentration of

sulfur hexafluoride using the formula below. The result

may not exceed the specification in Section 2 of this

Standard.

Sample Peak Area

Standard Peak Area

Concentration

of Standard

Concentration

of Sample

5.5 Water — This procedure is for the determination

of trace moisture (water) in carbon tetrafluoride using a

continuous flowing electrolytic hygrometer.

5.5.1 Detection Limit — 1.0 ppm (vol/vol) or -76°C

(-105°F).

5.5.2 Flow Requirements — Set the sample pressure

and flow rate in accordance with the instrument

manufacturer’s instructions.

5.5.3 Operation Check — Check the electrolytic

hygrometer periodically. A gas, containing a known

amount of water, should be passed through the

hygrometer. Agreement between the electrolytic

hygrometer and the moisture standard should be within

their relative accuracies.

5.5.4 Operating Procedure

5.5.4.1 Obtain a continuous flow sample of gas, from

the CF

source, using a clean, passivated stainless steel

line which has been purged dry after exposure to

ambient moisture. (See Notes 3 and 4.)

5.5.4.2 After prepurging with a dry gas, allow the

sample gas to flow through the sampling system and the

electrolytic moisture analyzer 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

carbon tetrafluoride 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)

SEMI C3.40-1000 © SEMI 1989, 2000 4

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

-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.

Table 1 Calibration Concentrations

Added volume of

Working Standard

(ml)

Total Volume

(ml)

Resulting F-

Concentration

(M)

0.2 100.2 1.0 x10

-6

0.2 100.4 2.0 x10

-6

0.4 100.8 4.0 x10

-6

0.4 101.2 5.9 x10

-6

0.8 102.0 9.8 x10

-6

1.0 103.0 1.5 x 10

-5

2.0 105.0 2.4 x 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 CF

through the bubblers using a suitable flow controller or

flowmeter.

5.6.5.7 Sample approximately 15 liters of CF

Record flowrate and time of sampling to determine total

volume sampled (flowrate x 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

273 T

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: 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 CF

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: Introduce the calibration standard as many

times as necessary to achieve the desired precision.

Note 2: 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 3: A passivation procedure is described in the

Metals Handbook, 10th ed., Vol. 2, American Society

for Metals, Metals Park, OH.

Note 4: The sampling system and hygrometer must be

designed to operate at 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

hygrometer.

Note 5: Polytetrafluoroethlyene, polymethylpentene

and polypropylene are suitable plastic materials.

Figure 1

Configuration for the Analysis of CO

, O

, N

, and CO in CF