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SEMI F29-0997 © SEMI 1997, 1103 2 5.2.7 pigtail bleed — a pigtail bl eed is a reverse flow of purge gas from the pigtail to minimize atm ospheric intrusion into the gas panel. 5.2.8 purge cycle — following the initial pr…

SEMI F29-0997 © SEMI 1997, 1103 1

SEMI F29-0997 (Reapproved 1103)

TEST METHOD FOR PURGE EFFICACY OF GAS SOURCE SYSTEM

PANELS

This test method 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 September 3, 2003. Initially available at www.semi.org September 2003; to be published

November 2003. Originally published September 1997.

1 Purpose

1.1 This document defines the purge efficacy test

method recommended for determining the minimum

acceptable level of purge efficacy for gas source

systems used in semiconductor manufacturing. It is also

intended as an aid to the procurement of gas source

equipment.

NOTE 1: Users of this specification are encouraged to submit

suggested revisions or other comments to SEMI.

2 Scope

2.1 This specification applies to gas source equipment

used in semiconductor manufacturing facilities and

comparable research and development areas. It includes

contamination testing requirements for gas source

systems.

2.2 The tests covered by this document are as follows:

2.2.1 Purge efficacy with a non-interactive gas using

manufacturers’ standard purge sequence.

2.2.2 Purge efficacy with a non-interactive gas using

the test method specified purge sequence.

2.2.3 Purge efficacy with an interactive gas using

manufacturers’ standard purge sequence.

2.2.4 Purge efficacy with an interactive gas using the

test method specified purge sequence.

NOTICE: This standard does not purport to address

safety issues, if any, associated with its use. It is the

responsibility of the users of this standard to establish

appropriate safety and health practices and determine

the applicability of regulatory or other limitations prior

to use.

3 Limitations

3.1 The document is not intended to determine the safe

operation of a gas source system. The test method

described here is for determining the removal efficacy

of hazardous gas from the pigtail portion of the gas

panel during routine cylinder change operations (pre-

purge). It does not address the purge condition after the

change of the cylinder (post-purge) nor the purge of the

entire gas source system which is usually performed

following its initial installation or during maintenance

(maintenance purge).

3.2 Because the response time of moisture and oxygen

analyzers utilizing different technologies can differ

significantly, this can lead to the possibility that

different instruments will report different peak heights

when measuring identical contaminant spikes.

Therefore, results of tests should only be compared

when similar analyzers are used.

4 Referenced Standards

None.

5 Terminology

5.1 Abbreviations and Acronyms

5.1.1 ppb — Molar parts per billion, same as ppbv.

5.1.2 ppm — Molar parts per million, same as ppmv.

5.2 Definitions

5.2.1 clean dry air (CDA) — filtered air filtered to 0.02

mm and dried to a dew point of at least -80° C.

5.2.2 dry down — removal of residual moisture in a

gas delivery or distribution system, often accomplished

by flowing a stream of high purity dry inert gas

continuously through the system for an extended period

of time.

5.2.3 dwell time — the time for which vacuum or

pressure is applied during the evacuation or

pressurization steps of a purge operation.

5.2.4 interactive gas — a gas that will readily adsorb to

the surface of a vessel used to contain or transport it.

Examples of interactive gases are hydrogen chloride

and moisture.

5.2.5 non-interactive gas — a gas that will not adsorb

to the surface of a vessel used to contain or transport it.

Examples of non-interactive gases are oxygen and

nitrogen.

5.2.6 pigtail — the pigtail is the part of the gas source

equipment that is the flexible connection between the

cylinder and the gas panel.

SEMI F29-0997 © SEMI 1997, 1103 2

5.2.7 pigtail bleed — a pigtail bleed is a reverse flow

of purge gas from the pigtail to minimize atmospheric

intrusion into the gas panel.

5.2.8 purge cycle — following the initial process vent

step, a cycle is defined as a pressurization step followed

by an evacuation step.

5.2.9 purified nitrogen — nitrogen purified to meet the

following characteristics:

Moisture < 20 ppb

Oxygen < 10 ppb

Total hydrocarbons < 1 ppm

< 1 ppm

CO < 1 ppm

6 Ordering Information

6.1 Orders for equipment or services requiring purge

efficacy testing in accordance with this test method

shall include the following:

6.1.1 This test method number and date of issue.

6.1.2 Test requirements as defined in the detailed

specifications for the specific product being purchased.

6.1.3 Whether certifications of tests and a report of the

test results is required.

7 Requirements

7.1 Personnel Qualification — Personnel performing

tests in accordance with this specification shall have

suitable training and experience. Such personnel

should, as a minimum,

7.1.1 be trained and experienced in operation of gas

source control equipment,

7.1.2 be trained and experienced in the use of oxygen

and moisture analyzers, and

7.1.3 be familiar with the operation and calibration of

the specific equipment used in performing the tests.

8 Apparatus

8.1 Oxygen Analyzer — The oxygen analyzer should

meet or exceed the following characteristics:

Limit of Detection 10 ppb

Accuracy ± 10 ppb

8.2 Moisture Analyzer — The moisture analyzer

should meet or exceed the following characteristics:

Limit of Detection 10 ppb

Accuracy ± 10 ppb

8.3 Pressure Transducer — The transducer should be

of a high-purity type with minimal dead volume and

meet or exceed the following characteristics:

Accuracy ± 3.4 kPa (0.5 psi)

Hysteresis ± 3.4 kPa (0.5 psi)

Non-Repeatability ± 0.7 kPa (0.1 psi)

8.4 Mass Flow Controller or Flow Meter — The mass

flow controller or flow meter should be accurate to ±

0.2 slpm.

8.5 Moisture Source — The moisture source must be

capable of providing a 2 slpm continuous flow of 2.0 ±

0.2 ppm moisture in nitrogen mixture at 138 kPa (g) [20

psi (g)] for a minimum of 30 minutes.

9 Procedure

9.1 Purge efficacy determination with non-interactive

gas at manufacturer’s recommended pressure, vacuum,

and dwell times.

9.1.1 Connect gas source equipment as in Figure 1.

NOTE 2: To avoid biasing the test results by substantially

increasing piping volume to be purged, the dead space

between the cylinder connection and the valves isolating the

analyzer and the contaminant source must be small compared

to the total pigtail volume. The use of mono-block valve and

flow-through type pressure transducer is highly

recommended.

9.1.1.1 However, the pigtail is connected to the

cylinder valve during the purge in an actual cylinder

change operation. The small additional volume to be

purged in the test setup may be used to account for the

volume of the cylinder valve outlet cavity, which must

be purged during a cylinder change.

9.1.2 To challenge the gas panel with a known

contaminant gas, completely fill and pressurize the gas

source system to 207 kPa (g) [30 psi (g)] with CDA as

measured at the pigtail with the pressure transducer.

9.1.3 Using purified nitrogen as the purge gas,

complete one purge cycle at the manufacturer’s

recommended pressure, vacuum, and dwell times.

9.1.4 Flow purified nitrogen using a pigtail bleed at 1

slpm or at the oxygen analyzer manufacturer’s

recommended flow rate, whichever is higher, into the

oxygen analyzer for 10 minutes or until below the

detection limit of the oxygen analyzer.

9.1.5 Record the pressure and peak oxygen concentration in Table 1. It is highly recommended that, in addition to

the peak oxygen concentration, the oxygen concentration readings also be recorded at regular intervals during the

measurement, so that a graph of the oxygen concentration level in the pigtail bleed gas versus time can be drawn if

necessary.

9.1.6 Repeat Sections 9.1.2–9.1.5 for 2, 5, 25, and 50 purge cycles at the manufacturer’s recommended pressure,

vacuum and dwell times. Additional tests using other purge cycle numbers are encouraged and may provide a more

complete characterization of the purge performance of the test piece.

9.1.7 Plot the peak residual oxygen concentration versus cycles as in Figure 2 for manufacturer’s recommended

pressure, vacuum, and dwell times.

9.2 Purge efficacy determination with non-interactive gas at standard pressure, vacuum and dwell times.

9.2.1 Connect the gas source equipment as in Figure 1.

Figure 1

Test Schematic

9.2.2 To challenge the gas panel with a known contaminant gas, completely fill and pressurize the gas source

system to 207 kPa (g) [30 psi (g)] with CDA as measured at the pigtail with the pressure transducer.