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SEMI F76-0303 © SEMI 2003 5 • last calib ration date of CNC, • age of moisture permeation source, • measured moisture con centration at valve V7, • ambient temperature and relative humidity, and • record all exposure tim…

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SEMI F76-0303 © SEMI 2003 4
measured on the analyzer should be recorded. This
level must be 100 ppm ± 10 ppm or the test cannot
proceed.
11.5 Following each test, the section of tubing between
V3, V4 and the test piece must be replaced. This will
minimize the particle contribution from the system due
to system corrosion.
12 Calibration
12.1 Calibration of the mass flow controllers should be
performed according to manufacturers
recommendations. The permeation source used in the
moisture generator should be provided with
documentation of permeation rate.
13 Procedure
13.1 Baseline Particle Cleanliness Evaluation — A
particle cleanliness evaluation is to be conducted on
each component before installation into the HCl
exposure system. The baseline particle cleanliness
evaluation is to be conducted on new components
according to one of the following test methods:
13.1.1 Low Pressure Regulators — SEMASPEC
#93021510A-STD — Test Method for Determination
of Particle Contribution by Low Pressure Regulators in
Gas Distribution Systems.
13.1.2 Valves — ASTM F1394-92 — Standard Test
Method for Determination of Particle Contribution from
Gas Distribution System Valves.
13.1.3 Filters — SEMASPEC #93021511A — Test
Method for Determination of Particle Contribution by
Filters in Gas Distribution Systems.
13.2 Install sample in system while maintaining a
continuous nitrogen purge of 500 sccm.
13.3 Bake the sample for two hours. Filters will be
baked at 100°C and valves and regulators will be baked
at 70°C. Maintain a continuous N
2
purge during
baking. Valves and regulators will be in the full open
position.
13.4 Cool sample overnight under N
2
purge of 500
sccm. From this point on, the sample remains at room
temperature.
13.5 Run HCl exposure sequence once per hour six
times.
Table 1 HCl Exposure Sequence
STEP TIME CONDITION
1 5 minutes Flow dry N
2
, 0.5 slm
2 10 minutes Flow wet N
2
- 100 ppm
H
2
O, 0.5 slm
STEP TIME CONDITION
3 5 minutes Flow dry HCl, 0.5 slm
4 40 minutes Stagnant HCl, no flow
13.6 Hold sample in static HCl (no flow) for 16 hours.
13.7 Repeat Sections 13.5 and 13.6 for a total of 8
times. This will require a number of days to complete.
If this involves a weekend or a period of time when the
test must be temporarily suspended, then a dry N
2
flow
must be resumed while in this idle mode (see Section
11.1). Flow is not to be interrupted prior to completion
of Section 13.6.
13.8 The test should not be interrupted immediately
prior to moving to the particle testing, Section 13.9.
13.9 Purge with dry N
2
for 2 hours at 500 sccm.
13.10 Cycle purge for 30 cycles. The cycle purge
consists of 20 seconds of rough vacuum 85000 pascals
(25” Hg) and 10 seconds of pressurization with dry N
2
to 5.5 × 10
5
pascals (80 psig).
13.11 Final Dry N
2
Purge — The component is purged
with dry N
2
according to the following schedule: 4
hours for a valve or regulator, and 24 hours for a filter.
13.12 With a purged glove bag around the sample,
remove it into the glove bag and cap both ends. The
sample can now be removed from the glove bag and
transferred to the particle test stand.
13.13 Final Particle Test in Nitrogen
13.13.1 Place a purged glove bag on the particle test
apparatus at the sample installation point.
13.13.2 Place the sample inside the glove bag and only
then remove the caps and install the sample in the
system.
13.13.3 Carry out the particle test according to the
methods cited in Section 13.1.
14 Reporting Results
14.1 Data Presentation — Particle data should be
plotted for each component on a single graph according
to the methods cited in Section 13.1. Both the before
HCl exposure and after HCl exposure data should be
plotted on the same graph.
14.2 Other Information — Other information to be
included in the report:
• sample make, model and serial number,
• date of test,
• person who conducted test,
SEMI F76-0303 © SEMI 2003 5
• last calibration date of CNC,
• age of moisture permeation source,
• measured moisture concentration at valve V7,
• ambient temperature and relative humidity, and
• record all exposure times, temperatures, and flow
rates from each of the exposure events.
15 Related Documents
15.1 SEMI Standards
SEMI F55 — Test Method for Determining the
Corrosion Resistance of Mass Flow Controllers
15.2 SEMATECH Documents
3
SEMASPEC #90120390B-STD — Test Method for
Determination of Particle Contribution by Valves in
Gas Distribution Systems.
SEMASPEC #92071233B-STD — “SEMASPEC
Provisional Test Method for Determining the Corrosion
Resistance of Mass Flow Controllers,” February 5,
1993.
15.3 Other
Hwa-Chi Wang, Govind Doddi, and Stephen Chesters,
“Comparative Corrosion Studies for HCl - and HBr-
Gas Distribution Systems,” 1995 Proceedings - Institute
of Environmental Sciences.
Journal of the IES — “Estimating the Lifetime of
Electropolished Stainless Steel (EPSS) Tubing in
Corrosive Gas Services”, July/Aug. 1994.
The Electrochemical Society, Inc. — “The Role of
Moisture in Corrosion of HBr Gas Distribution
Systems”, April 1995.
3 SEMATECH, 2706 Montopolis Drive, Austin, TX 78741, website:
www.sematech.org
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 F77-0703 © SEMI 2003 1
SEMI F77-0703
TEST METHOD FOR ELECTROCHEMICAL CRITICAL PITTING
TEMPERATURE TESTING OF ALLOY SURFACES USED IN
CORROSIVE GAS SYSTEMS
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 April 11, 2003. Initially available at www.semi.org June 2003; to be published July 2003.
1 Purpose
1.1 The purpose of this test method is to determine the
relative resistance to pitting corrosion of the wetted
surfaces of components intended for use in corrosive
gas distribution systems for semiconductor
manufacturing. This test method is intended to
differentiate between alloy compositions and processes
intended to enhance the corrosion performance of the
wetted surfaces.
2 Scope
2.1 This test method describes a procedure, based on
the electrochemical critical pitting temperature (CPT),
which is used to rank the pitting corrosion resistance of
wetted surfaces of tubing or test coupons of
representative finished surfaces intended for use in
corrosive gas systems. Pitting corrosion is believed to
be a major corrosion failure mode in semiconductor gas
delivery systems, particularly in components and tubing
welded and exposed to corrosive gases.
2.2 This test method is an adaptation of ASTM G150.
The adaptation describes a method for performing the
test method on coupons or wetted-surface sections cut
from gas supply system components such as tubing. It
is an aqueous immersion method.
2.3 The test method is reproducible and provides a
metric (critical pitting temperature) in addition to a
qualitative (visual) evaluation of corrosion resistance.
2.4 This test method applies to materials as specified in
SEMI Standards referenced in Section 4.1, and to welds
of these materials.
2.5 This test method may also be used for other
corrosion resistant alloys and their welds not referenced
in Section 4.1.
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 health practices and determine the
applicability of regulatory or other limitations prior to
use.
3 Limitations
3.1 Only analysts familiar with the instrumentation and
technique should use this test method.
3.2 The test conditions of this test method do not
simulate actual service in a corrosive gas supply
system. Thus the test results may not correlate to
relative corrosion resistance in a specific corrosive gas
or corrosive gas supply system.
3.3 The Critical Pitting Temperature (CPT) is valid
only in a range of 10° C to 95° C. A CPT result greater
than 95° C is not considered to be valid since it is
approaching the boiling point of the solution. A critical
pitting temperature (CPT) below 10° C shall only be
reported as < 10° C and may be an indication of crevice
corrosion.
3.4 Since alloy composition and surface parameters
can affect the results of the test (e.g., surface finish), all
variables other than the one being tested must be fixed
during the test in order to obtain reproducible and
comparable results.
3.5 The bias for this test has not yet been determined.
4 Referenced Standards
4.1 SEMI Standards
SEMI F2 — Specification for 316L Stainless Steel
Tubing for General Purpose Semiconductor
Manufacturing Applications
SEMI F17 — Specification for High Purity Quality
Electropolished 316L Stainless Steel Tubing,
Component Tube Stubs, and Fittings made from Tubing
SEMI F19 — Specification for the Finish of the Wetted
Surfaces of Electropolished 316L Stainless Steel
Components
SEMI F20 — Specification for 316L Stainless Steel
Bar, Extruded Shapes, Plate, and Investment Castings
for Components Used in High Purity Semiconductor
Manufacturing Applications