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SEMI F67-1101 © SEMI 2001 2 5.1.13 ppm — parts per million, volume basis 5.1.14 psi — pounds pe r squa re inc h 5.1.15 psia — pounds per square inch absolute 5.1.16 psig — pounds p er sq uare inc h gauge 5.1.17 R a — su …
SEMI F67-1101 © SEMI 20011
SEMI F67-1101
TEST METHOD FOR DETERMINING INERT GAS PURIFIER CAPACITY
This test method was technically approved by the Global Facilities Committee and is the direct responsibility
of the North American Facilities Committee. Current edition approved by the North American Regional
Standards Committee on August 27, 2001. Initially available at www.semi.org September 2001; to be
published November 2001.
1 Purpose
1.1 The purpose of this document is to define a test
method to quantify impurity removal capacity of inert
gas purifiers.
2 Scope
2.1 To determine the impurity capacity of a gas purifier
at the point of breakthrough. Capacity tests are done by
adding ppm levels of a given gaseous impurity to a pure
zero gas and monitoring the effluent of the test purifier
for active impurity species.
NOTE 1: Mixtures of two or more impurities for multi
impurity removal purifiers is a more representative method
for determining capacity.
2.2 This document is intended for point of use (POU)
inert gas purifiers where inlet purity is 99.9995% or
higher.
2.3 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 and safety health practices and determine
the applicability of regulatory limitations prior to use.
3 Limitations
3.1 The inherent limitation to this method is the limit
of detection (LOD) of the analytical instrument
employed by the user.
3.2 This test method can only be used to compare
purifier capacity results if the user application for flow
rate, pressure, and temperature are the same as the test
conditions. Different
users and/or different operating
conditions may result in different purifier performance
results.
3.3 In testing mixtures of impurities, some impurities
may influence the capacity results. Discussion with the
manufacturer is highly recommended prior to testing.
3.4 The test method does not apply to particulates.
3.5 This test method can only be used to compare the
capacity of different purifiers, when the purifiers are
sized for the appropriate flow rate. Comparing purifiers
of different maximum flow ratings will result in
misleading information.
3.6 This test method will provide capacity information
only for impurities that are used in the challenge gas.
4 Referenced Standards
4.1 SEMI Standards
SEMI E29 — Standard Terminology for the Calibration
of Mass Flow Controllers and Mass Flow Meters
SEMI F6 — Guide for Secondary Containment of
Hazardous Gas Piping Systems
SEMI F22 — Guide for Gas Distribution Systems
SEMI F33 — Method for Calibration of Atmospheric
Pressure Ionization Mass Spectrometer (APIMS)
4.2 ANSI Standards
1
ANSI B46.1 — Surface Texture (Surface Roughness,
Waviness, and Lay)
NOTE 2: Unless otherwise indicated, all documents cited
shall be the latest published versions.
5 Terminology
5.1 Abbreviations and Acronyms
5.1.1 APIMS — atmospheric pressure ionization mass
spectrometer
5.1.2 °C — degrees Celsius
5.1.3 DUT — device under test
5.1.4 °F — degrees Fahrenheit
5.1.5 in — inch
5.1.6 kPa — kiloPascal
5.1.7 LOD — limit of detection
5.1.8 m — meter
5.1.9 MFC — mass flow controller
5.1.10 NMHC — non methane hydrocarbons
5.1.11 POU — point of use
5.1.12 ppb — parts per billion, volume basis
1 American National Standards Institute, New York Office: 11 West
42nd Street, New York, NY 10036, USA. Telephone: 212.642.4900;
Fax: 212.398.0023 Website: www.ansi.org
SEMI F67-1101 © SEMI 2001 2
5.1.13 ppm — parts per million, volume basis
5.1.14 psi — pounds per square inch
5.1.15 psia — pounds per square inch absolute
5.1.16 psig — pounds per square inch gauge
5.1.17 R
a
— surface roughness average (as defined in
ANSI B46.1)
5.1.18 R
a,max
— surface roughness maximum (as
defined in ANSI B46.1)
5.1.19 s — second
5.1.20 sccm — standard cubic centimeters per minute
5.1.21 slpm — standard liter per minute
5.2 Definitions
5.2.1 activation — the process of initially preparing the
purifier media to be chemically reactive with gas
impurities.
5.2.2 activation temperature — temperature at which
DUT was initially prepared.
5.2.3 atmospheric pressure ionization mass
spectrometer (APIMS) — an instrument consisting of
an atmospheric pressure ion source where gas phase
impurities are ionized via charge exchange reactions
with the bulk gas. These ions are directed into a
vacuum chamber where they are then separated by a
mass analyzer and detected by an electron multiplier.
5.2.3.1 ion source — the section of a mass
spectrometer used to generate sample ions by electron
impact, chemical ionization, or charge exchange.
5.2.3.2 mass analyzer — a device that utilizes electric
and/or magnetic fields to separate charged particles or
ions according to their mass-to-charge (m/e) ratios.
Examples of mass analyzers include quadrupole,
magnetic and/or electric sector, time of flight, and ion
traps.
5.2.3.3 electron multiplier — a device that detects and
amplifies electro-magnetic phenomena such as
positive/negative ions.
5.2.4 back pressure regulator — a self-contained
device, consisting of a mechanical or electrical sensor
and control device, commonly used in the
semiconductor industry to maintain a constant pressure
upstream of the regulator.
5.2.5 breakthrough — the point in time when an
individual impurity level in the purifier effluent exceeds
the level specified by the manufacturer. Typically in
the range of 1–100 ppb.
5.2.6 challenge gas — a gas mixture containing high
levels of gas impurities. Typically, a challenge gas has
impurities of between 500 ppm to 1% which is used to
shorten the test duration; however, challenges in the
range of 1–10 ppm for the impurities is more
representative.
5.2.7 gaseous impurities — gas phase elements and
compounds in the gas stream other than the process or
base gas.
5.2.8 impurity analyzer — an appropriate analyzer to
measure the concentration of desired impurities in a gas
stream from the ppm to the percent (%) concentration
range.
5.2.9 inert gas — a gas, which at ambient conditions,
does not react chemically with other materials or
chemicals.
5.2.10 limit of detection (LOD) — lowest concentration
that can be detected by an instrument. LOD is typically
defined as three times the standard deviation of the
mean noise level (see SEMI F6, lower detectable limit
of instrument).
5.2.11 mass flow controller (MFC) — a self-contained
device, consisting of a mass flow transducer, control
valve, and control and signal-processing electronics,
commonly used in the semiconductor industry to
measure and regulate the mass flow of gas (as defined
in SEMI E29).
5.2.12 pure gas — an inert gas, minimum purity of
99.9995%, and less than 1 ppb of each impurity that is
specified to be removed by the DUT.
5.2.13 purifier — generally a catalytic (getter,
reactive), resinous, or diatomaceous material within a
pressure vessel which removes particulate and/or trace
gas impurities from a gas stream (as defined in SEMI
F22).
5.2.14 purifier capacity — the total quantity of each
trace gas impurity that may be sorbed by the purifier
media. Defined as liters impurity/liter purifier media.
5.2.15 regeneration — the process of reactivating the
purifier media.
5.2.16 test duration — total time required to complete
the test procedure.
5.2.17 test flow rate — flow rate through DUT (slpm).
5.2.18 test pressure — pressure immediately upstream
of the DUT.
5.2.19 test temperature — operating temperature of
DUT.
5.2.20 ultratrace analytical instrumentation —
instrumentation that has sufficient sensitivity to
SEMI F67-1101 © SEMI 20013
measure all impurities of interest at the specified level
of the customer, the ppb or sub-ppb level.
5.2.21 zero gas — nitrogen, argon, helium or hydrogen
with an estimated level an order of magnitude, or more,
lower than the lowest calibration point for each
impurity of interest (as defined in SEMI F33).
6 Summary of Method
6.1 This method will allow a user to quantify the
impurity removal capacity of a given inert gas purifier
for that impurity.
7 Safety Precautions
7.1 This test method may involve hazardous materials,
operations, and equipment. The test method does not
purport to address the safety considerations associated
with its use. It is the responsibility of the user to
establish appropriate safety and health practices and
determine the applicability of regulatory limitations
before using this method.
7.2 Exhaust from the DUT should be properly vented.
7.3 Only the appropriate gas should be used for purifier
testing. Use of the inappropriate gas may cause
exothermic reactions and possible explosions.
7.4 Electric discharges or mechanical friction might
trigger combustion within a getter. Avoid situations
where there is an accumulation of electrostatic charge.
7.5 Purifiers are generally designed for use with
impurity levels less than 1% and should not be used to
purify air or other inappropriate gases. Contact the
manufacturer if there is any question as to the
suitability for a particular gas.
7.6 Care should be taken to minimize the purifier’s
exposure to room air (even filtered air). Room air may
chemically react with some purifiers shortening the
purifier lifetime. Follow manufacturer’s installation
procedures.
8 Test Protocol
8.1 Test Conditions
8.1.1 The test should be conducted following
manufacturers recommended handling procedures to
activate new media or regenerate existing purifier
media.
8.1.2 The test is to be conducted at a room temperature
maintained between 18°C (64°F) and 26°C (78°F).
Environmental temperature fluctuations within this
range are not expected to have any measurable effect on
the instrumentation used to detect the level of
impurities. Follow instrument manufacturer’s operating
procedures.
8.1.3 Testing performed at high impurity challenge
may alter test results, and may not be appropriate to do
for all types of purifiers. Any significant temperature
change during the test could have adverse or false
effects on the capacity results.
8.1.4 For a mixture of more than 1 impurity, competing
reactions may occur between impurities, which may
lead to different results.
8.2 Apparatus
8.2.1 Materials
8.2.1.1 Test Gas — a mixture of pure gas and
challenge gas. Select the appropriate concentration
level. For initial studies, a higher concentration range,
e.g., 500 ppm to 1% is suggested for each given
impurity. For more representative studies done over
longer time periods, 1–10 ppm for each given impurity
is suggested.
8.2.1.2 Pressure Regulators — all wetted internal
surfaces, where appropriate, should be made of
electropolished 316L stainless steel with an internal
surface finish of 0.18 µ m (7 µ in) R
a
and 0.25 µ m (10
µ in) R
a,max
, to control system pressures.
8.2.1.3 Pressure Gauge — all wetted internal surfaces,
where appropriate, should be made of electropolished
316L stainless steel with an internal surface finish of
0.18 µ m (7 µ in) R
a
and 0.25 µ m (10 µ in) R
a,max
, to
monitor system pressures.
8.2.1.4 Standard Test Flows — use appropriate mass
flow devices. One MFC with appropriate range of 0–50
slpm for the pure gas is suggested. Various MFCs with
appropriate ranges of 0–25 sccm, 0–100 sccm and 0–1
slpm for the challenge gas is suggested.
8.2.1.5 Tubing — made of electropolished 316L
stainless steel, with an internal surface finish of 0.18
µ m (7 µ in) R
a
and 0.25 µ m (10 µ in) R
a,max
, to transport
gas.
8.2.1.6 Fittings — the appropriate size face-seal fitting
is used.
8.2.1.7 Gaskets — use metal gaskets for all
connections. New gaskets should be used for each new
connection. Use of cleanroom gloves is required when
handling gaskets and fittings.
8.2.2 Instrumentation
8.2.2.1 An APIMS or other ultratrace analytical
instrumentation is used to determine the level of each
gaseous impurity exiting the DUT.