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SEMI C6.4-90 © SEMI 1990, 2002 1 SEMI C6.4-90 (Reapproved 1102) PARTICLE SPECIFICATION FOR GRADE 20/0.02 NITROGEN (N 2 ) AND ARGON (Ar) DELIVERE D AS PIPELINE GAS This specification was technically approved b y the Globa…

SEMI C6.3-89 © SEMI 1989, 2003 2

6.4 Determine the background count for the particle

counter by using the standard method recommended by

the instrument manufacturer using hydrogen gas.

7 Specification

7.1 Maximum permissible total concentration: 20

particles per SCF equal to or larger than 0.2

micrometers, after subtracting background count as

defined in Section 4.1.1.

7.2 The specification will be considered as met, if the

particle concentration does not exceed 20 particles per

SCF in any five consecutive sampling periods as

defined in Section 4.1.5.

8 Report

8.1 Report each of the five consecutive sampling

periods to read as total number of particles per SCF7 of

gas, equal to or larger than 0.2 micrometers optical

equivalent diameter, without reference to any specific

size distribution function. The background count shall

be reported as defined in Section 4.1.1.

9 Calibration

9.1 The optical particle counter is normally calibrated

using latex spheres of a known diameter suspended in a

gas. Since the gas density and refractive index enter

into the amount of scattering detected by the

instrument, hydrogen should be used for calibration.

10 Safety

10.1 The lower explosive limit (LEL) for hydrogen in

air is 4%; therefore, proper precautions should be taken

to insure that the maximum possible concentration of

hydrogen in air does not exceed 2%. The particle

counter and any other ancillary equipment must be

checked for leaks and the hydrogen exiting the

equipment must be disposed of appropriately to insure

that its concentration in air at any point does not exceed

2%.

(a)

(b)

(c)

(d)

Figure 1

Schematic Diagrams of Configurations of

Different Merit for Obtaining Particle Samples

from Pipelines

NOTICE: SEMI makes no warranties or

representations as to the suitability of the standards set

forth herein for any 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.

By publication of this standard, Semiconductor

Equipment and Materials International (SEMI) takes no

position respecting the validity of any patent rights or

copyrights asserted in connection with any items

mentioned in this standard. Users of this standard are

expressly advised that determination of any such patent

rights or copyrights, and the risk of infringement of

such rights are entirely their own responsibility.

International), 3081 Zanker Road, San Jose, CA 95134. Reproductio

of the contents in whole or in part is forbidden without express writte

consent of SEMI.

SEMI C6.4-90 © SEMI 1990, 2002 1

SEMI C6.4-90 (Reapproved 1102)

PARTICLE SPECIFICATION FOR GRADE 20/0.02 NITROGEN (N

) AND

ARGON (Ar) DELIVERED AS PIPELINE GAS

This specification 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 July 21, 2002. Initially available at www.semi.org October 2002; to be published November

2002. Originally published in 1990.

1 Purpose

1.1 The purposes of this document are: (1) to set a

maximum permissible particle concentration for

20/0.02 grade nitrogen and argon bulk supply gases,

and (2) to describe a reference method for its

verification.

2 Scope

2.1 This document applies only to nitrogen gas and

argon gas delivered through pipelines; it is not

applicable to cylinder gases or gases in their liquid

state.

2.2 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 health practices and determine the

applicability or regulatory limitations prior to use.

3 Terminology

3.1 Variables

= Volume of the i

sample interval of the pipeline gas

= Volume of the i

sample interval of the background

= Concentration of particles observed in the i

sample

interval of the pipeline gas

= Concentration of particles observed in the i

sample

interval of the background

= Number of sample intervals of the pipeline gas

= Number of sample intervals of the background

Average observed concentration of counts in the

pipeline gas sample

Average observed concentration of background

counts

Calculated concentration of particles in the pi

eline

gas

Standard deviation of

3.2 Gas Sample Volume (V

, V

) — The volume of

the sample interval, expressed in standard liters at

standard conditions, 0° C (32° F) and 1.00° atmosphere

pressure. Standard Cubic Feet (SCF) is defined at

21.1° C (70° F) and 1.00° atmosphere pressure.

3.3 Average Observed Concentration of Counts

(

X ,

X ) — The average concentration of counts, i.e.:

∑

3.4 Calculated Concentration of Particles (

X ) —

The concentration of particles in the pipeline gas

obtained by correcting the observed concentration in

the pipeline gas for the observed concentration in the

background, i.e.:

− X

3.5 Standard Deviation (S

, S

) — A statistical

measure of the spread of the concentration of the counts

or particles. The first two are obtained from the interval

and average concentrations and the number of intervals,

i.e.:

−

()

∑

− 1

()













−

()

∑

− 1

()













The third is obtained from the first two, i.e.:

= S

+ S

(

)

NOTE 1: These expressions are derived from an assumption

of a Gaussian (Normal) distribution.

4 Apparatus

4.1 Particle Counter — An instrument suitable for

counting particles in gaseous nitrogen or argon with a

minimum detection efficiency of 90% at 0.02

micrometers as determined by the manufacturer of the

particle counter. Condensation nucleus counters

(CNCs) typically satisfy this requirement.

4.2 Pressure Reducer — An accessory required for

counters operated at atmospheric pressure, it should

SEMI C6.4-90 © SEMI 1990, 2002 2

preferably use expansion of the gas through a critical

orifice.

5 Test Method

NOTE 2: The details of sampling configuration,

measurement procedure, and instrument calibration procedure

and frequency must be agreed upon by the user and supplier,

taking into account good engineering practice.

5.1 Determine the average observed concentration of

counts in the background (

X ) by passing air, nitrogen

or argon, believed to be free of particles of 0.02

micrometers or more in diameter, through the

instrument and recording the total number of counts.

Count a minimum of 8 sample intervals, each at least

25 standard liters (0.95 SCF) or 30 minutes, whichever

is greater. A suggested assembly for performing this

test, using a filter which removes particles in this size

range, is shown in Figure 1. Calculate

X as defined in

Section 3.

X must not exceed 2 particles per 25

standard liters.

5.2 The sampling point should be at outlet of system,

and sampling lines should be as short as possible.

5.3 A suggested sampling probe configuration for

turbulent main line flow is shown in Figure 2. The flow

rate in the sampling tube at pipeline pressure should be

set so that the mean sampling flow velocity at the probe

inlet matches as closely as possible the axial flow

velocity in the pipeline. The pitot sampling tube ID

should be no less than 2 mm (0.08 inch). The orifice

and sampling horn should be sized so that the mean

flow velocity at the particle counter probe inlet matches

the axial flow velocity in the horn as closely as

possible.

5.4 Count the particles in each of at least 8 sample

intervals. Each sample interval must be at least 25

standard liters or 30 minutes, whichever is greater.

Record the number of counts and the sample volume

for each interval. Calculate

X and S

, as defined in

Section 3.

6 Specification

6.1 Maximum Permissible Particle Concentration —

20 particles per 25 standard liters as determined by the

instrument specified in Section 4.

6.2 The specification will be considered met if the

calculated concentration of particles plus two standard

deviations does not exceed 20 particles per 25 standard

liters, i.e.:

∗

≤

articles/25 standard

7 Report

7.1 The report shall contain the values of all the

variables defined in Section 3.

8 Precision

8.1 This test procedure defines the requirements to

satisfy the specification at the 95% confidence level.

Figure 1

Suggested Assembly for Determining Particle

Counter Background

Figure 2

Schematic Diagram of Configuration for Obtaining

Particle Samples from Pipelines

NOTICE: SEMI makes no warranties or

representations as to the suitability of the standards set

forth herein for any 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 mentioned herein. These

standards are subject to change without notice.

The user’s attention is called to the possibility that

compliance with this standard may require use of

copyrighted material or of an invention covered by

patent rights. By publication of this standard, SEMI

takes no position respecting the validity of any patent

rights or copyrights asserted in connection with any

item mentioned in this standard. Users of this standard

are expressly advised that determination of any such

patent rights or copyrights, and the risk of infringement

of such rights, are entirely their own responsibility.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o

the contents in whole or in part is forbidden without express written

consent of SEMI.