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SEMI F78-0304 © SEMI 2003, 2004 16 APPENDIX 1 STAINLESS STEEL AND WELDING FUME NOTICE : The ma terial in thi s appendix i s an official part o f SEMI F78. It has been deri ved from the cited documents. Determination of t…
SEMI F78-0304 © SEMI 2003, 2004 15
Figure 9
If a Cut-Out or Cut-In is Required, Purge Shall be Applied to Both Ends or the Downstream End Must be
Discarded or Cleaned
SEMI F78-0304 © SEMI 2003, 2004 16
APPENDIX 1
STAINLESS STEEL AND WELDING FUME
NOTICE: The material in this appendix is an official part of SEMI F78. It has been derived from the cited
documents. Determination of the suitability of the material is solely the responsibility of the user.
A1-1 General
A1-1.1 The fume generated when welding stainless
steels includes respirable particles, the composition of
which—particularly with the flux-shielded welding
processes—suggests a risk to cause cancers. However,
epidemiological analyses have not identified any actual
risk specific to stainless steels but have shown a slight
excess of lung cancers among welders as a whole, i.e.
both welders of non-alloyed steels and welders of
stainless steels, compared with the general population.
The cause of this excess has not been identified but may
be connected with factors incidental to welding.
Nevertheless, appropriate precautions to avoid exposure
to welding fume of all kinds are advisable and indeed
necessary if regulatory limits are to be observed.
A1-1.2 There is an important difference between the
chemical forms of chromium in fume from the flux
processes and from the gas-shielded processes. In the
former group most of the chromium is present in
hexavalent form (chromates), while almost all
chromium in fume produced by the gas-shielded
processes is in the trivalent form and hexavalent
compounds are only present in very small proportions.
The relevance of this difference is that, without
reference to welding, hexavalent chromium compounds
are classified as carcinogenic to humans (Group 1) by
the IARC
5
particularly lung cancer. This fear is based
on the chemical composition of the fume, especially
that produced by the flux processes, and the very small
size of the particles, which puts them in the respirable
range, i.e., capable of penetration down to the level of
the lung alveoli. Trivalent chromium compounds are
unclassifiable to carcinogenicity to humans (Group 3).
Nickel compounds are also classified in Group 1 by the
IARC.
A1-1.3 Further information on the above topic can be
found in Status Report: Stainless Steel and Welding
Fume, SR-0008, March 2001, Nickel Development
Institute, 214 King Street West, Suite 510, Toronto,
Ontario, Canada M5H 3S6.
A1-1.4 For information about hexavalent chromium,
refer to HESIS Hazard Alert, June 1992, Hazard
Evaluation System & Information Service, California
Occupational Health Program, 2151 Berkeley Way,
Annex 11, Third Floor, Berkeley, CA 94704.
5 International Agency for Research on Cancer
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
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respecting any materials or equipment mentioned
herein. These standards are subject to change without
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Copyright by SEMI® (Semiconductor Equipment and Materials
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f
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consent of SEMI.
SEMI F79-0703 © SEMI 2003 1
SEMI F79-0703
GUIDELINE FOR GAS COMPATIBILITY WITH SILICON USED IN GAS
DISTRIBUTION COMPONENTS
This guideline 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 guideline is to identify resource
information on compatibility of gases in contact with
silicon in the wetted path of a gas delivery system
operating at typical gas stick conditions.
2 Scope
2.1 The information and conclusions provided are
taken from published literature. References are cited.
No opinion is made as to the validity of the published
conclusions. The suggestions are specific to high purity
silicon, single or poly crystal, covered by native oxide.
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 (Prescribed Conditions)
3.1 The guideline applies to the gas distribution system
for a typical semiconductor process tool. It is assumed
that silicon is in the wetted path as a coating or a
silicon-based component (eg. a valve, orifice, sensor,
mass flow controller) in the gas distribution system.
The ambient temperature and operating temperature
limits are typical for the industry. No additional energy
source, thermal, radiative or ionizing, is present. The
moisture content of the gas is not specified for the
purpose of this guideline; the recommendations apply
whether or not the conditions are anhydrous.
4 Referenced Standards
4.1 SEMI Standard
SEMI E52 — Practice for Referencing Gases Used in
Digital Mass Flow Controllers
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
5 Classification of Gases
5.1 The gases included are taken from SEMI E52; the
number assigned to a gas is the same as in that
document.
5.1.1 Inerts
5.1.2 Hydrogen
5.1.3 Hydrocarbons
5.1.4 Halogenated Hydrocarbons
5.1.5 Hydrides
5.1.6 Halogens, other than Fluorine
5.1.7 Halides, other than Fluorides
5.1.8 Fluorine and Fluorides
5.1.9 Organo-metallic and Siloxanes
5.1.10 Oxygen and Oxides and Sulfides
5.1.11 Nitrogen and Nitrogen Compounds
5.1.12 Acids
5.1.13 Other
6 Review of the literature
6.1 Inerts
6.1.1 References (1, 2, 3, 4, 5) are cited which indicate
these gases do not react with silicon under the
prescribed conditions.
6.2 Hydrogen
6.2.1 References (1, 2, 3, 4, 5) are cited which indicate
these gases do not react with silicon under the
prescribed conditions. Hydrogen has been reported to
react with silicon (75) and silicon carbide (76) at
temperatures above 1100° C.
6.3 Hydrocarbons
6.3.1 References (1, 2, 3, 4, 5, 55, 56) are cited which
indicate these gases do not react with silicon under the
prescribed conditions.
6.4 Halogenated Hydrocarbons
6.4.1 References (1, 2, 3, 4, 5, 35, 51, 54, 55, 56, 57,
58, 59) are cited which indicate these gases do not react
with silicon under the prescribed conditions. Extensive
review papers by Flamm (55) and Coburn (56) cite
numerous references on the etching of silicon and other
materials using halogenated hydrocarbons. The critical
requirement for etching of silicon, or any material using