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SEMI C6.5-90 © SEMI 1990, 2002 3 NOTICE: SEMI makes no warranties or representatio ns as to the suitability of th e standards set forth herein for any particular application. Th e determination of the suitability of the …
SEMI C6.5-90 © SEMI 1990, 2002 2
4.2 Pressure Reducer — An accessory required for
counters operated at atmospheric pressure, it should
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 (
B
X ) by passing air, nitrogen
or argon, believed to be free of particles of 0.2
micrometers or more in diameter, through the
instrument and recording the total number of counts. A
suggested assemby for perfoming this test, using a filter
which removes particles in this size range, is shown in
Figure 1. A method recommended by the instrument
manufacturer, such as internal recirculation through a
filter, may be substituted for the system shown. Count a
minimum of 8 sample intervals, each at least the time to
sample 25 standard liters (0.95 SCF) or 30 minutes,
whichever is greater. Calculate
B
X as defined in
Section 3.
B
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 the time
to sample 25 standard liters or 30 minutes, whichever is
greater. Record the number of counts and the sample
volume for each interval. Calculate
C
X and S
C
, as
defined in Section 3.
6 Specification
6.1 Maximum Permissible Particle Concentration —
10 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 10 particles per 25 standard
liters, i.e.:
X
C
+
2
∗
S
C
≤
10
particles/25 standard liters
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 Diagrams of Configurations of
Different Merit for Obtaining Particle Samples
from Pipelines
SEMI C6.5-90 © SEMI 1990, 2002 3
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.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o
f
the contents in whole or in part is forbidden without express written
consent of SEMI.
SEMI C6.5-90 © SEMI 1990, 2002 1
SEMI C6.6-90 (Reapproved 1102)
PARTICLE SPECIFICATION FOR GRADE 10/0.1 NITROGEN (N
2
) 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 10/0.1
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
V
Mi
= Volume of the i
th
sample interval of the pipeline gas
V
Bi
= Volume of the ith sample interval of the
background
X
Mi
= Concentration of particles observed in the i
th
sample
interval of the pipeline gas
X
Bi
= Concentration of particles observed in the i
th
sample
interval of the background
N
M
= Number of sample intervals of the pipeline gas
N
B
= Number of sample intervals of the background
M
X=
Average observed concentration of counts in the
pipeline gas sample
B
X=
Average observed concentration of background
counts
C
X=
Calculated concentration of particles in the pipeline
gas
S
M
=
Standard deviation of
M
X
S
B
=
Standard deviation of
B
X
S
C
=
Standard deviation of
C
X
3.2 Particle Size/Particle Diameter — The optical
equivalent diameter as detected by a given light-
scattering particle counter.
3.3 Gas Sample Volume (V
Mi
, V
Bi
) — 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.
3.4 Average Observed Concentration of Counts
(
M
X ,
B
X ) — The average concentration of counts, i.e.:
X
M
=
X
Mi
∑
N
M
X
B
=
X
Bi
∑
N
B
3.5 Calculated Concentration of Particles (
C
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
C
=
X
M
− X
B
3.6 Standard Deviation (S
M
, S
B
, S
C
) — 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.:
S
M
=
X
Mi
−
X
M
()
2
∑
N
M
− 1
()
1
2
S
B
=
X
Bi
− X
B
()
2
∑
N
B
− 1
()
1
2
The third is obtained from the first two, i.e.:
S
C
= S
M
2
+ S
B
2
(
)
1
2
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
lower detection limit of 0.1 micrometers or less, based
on calibration with polystyrene latex spheres.