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SEMI S14-0704 © SEMI 2000, 2004 6 Appendix 1 s hould be included. For ea ch identified residual risk, the report sho uld: • explain the mechanism of loss or damage; • id entify aggravating or necessary contribu ting fact…

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SEMI S14-0704 © SEMI 2000, 2004 5
which do not participate chemically in the process (e.g.,
vacuum pump oil).
6.2.3.2 In assessing the risk, the evaluator should
consider:
• the quantity, concentration, state, temperature, and
pressure of each chemical in each container,
• for those chemicals supplied automatically by the
facility, the available flow, pressure, and total
quantity,
• the aggregate supplies and distribution of similar
chemicals,
• the inherent properties of the chemicals, such as
flammable limits, flash point, autoignition
temperature, heat of combustion, and the products
of combustion and decomposition (see the Material
Safety Data Sheets for guidance on evaluation of
these properties),
• the exposure to oxidizers, and
• the exposure to ignition sources.
NOTE 17: Chemicals with similar fire properties may be
considered together for the purpose of this assessment.
6.3 Sources of Ignition
6.3.1 Sources of ignition can be broadly divided into
those within the equipment and those external to it.
6.3.2 Internal Sources
6.3.2.1 Potential electrical ignition sources:
• devices or conditions that in normal operation can
generate ignition energy (e.g., heaters, static
electricity, lasers);
• devices or conditions that in reasonably foreseeable
assembly, use and/or wear conditions can generate
ignition energy (e.g., power connectors, terminal
strips);
• devices that in reasonably foreseeable single point
failure modes can generate ignition energy (e.g.,
transformers, electronic components); and
• short circuits.
6.3.2.2 Potential chemical ignition sources:
• exothermic process chemical reactions,
• exothermic reactions from inadvertent mixing of
process chemicals,
• exothermic reactions between process chemicals
and materials of construction, and
• release of pyrophoric or air-reactive chemicals
from processing or maintenance.
6.3.2.3 Sudden changes in process conditions:
• rapid (sometimes called “adiabatic”) compression
of gas mixtures, and
• rapid increases in temperature.
6.3.2.4 Mechanical friction
6.3.3 External Sources
6.3.3.1 External sources include expected and foreseen
conditions of the equipment’s use. As these are factors
normally outside the control of the equipment supplier,
their risks are difficult to assess. They are outside the
scope of this document.
6.4 Oxidizers
6.4.1 The most common oxidizer is air, which is
present within and around most semiconductor
manufacturing equipment. Unless specific measures
are taken to exclude air (e.g., inert pressurizing of an
electrical enclosure), it should be assumed to be
available in infinite supply.
6.4.2 It is possible that some materials of construction
will act as oxidizers or will yield oxidizers when
subjected to heat.
6.4.3 Several common process chemicals (e.g., oxygen
and hydrogen peroxide) are oxidizers. Their risks
should be assessed in a manner similar to that described
above for process chemicals that are fuels.
6.5 Reporting
6.5.1 Although these guidelines are intended for use
throughout the design and development process, it is
not the intent of these guidelines that the equipment
supplier should make all of the information recorded
during the development of the equipment available to
others. The equipment supplier should document the
fire risk assessment and mitigation in three forms:
internal records, a final fire risk assessment report, and
a summary report.
6.5.2 Relevant analyses, assessments, and design
decisions should be documented in the equipment
supplier' s internal records. These records need not,
however, be made available to other parties.
6.5.3 Final Fire Risk Assessment Report
6.5.3.1 This report should contain an itemized list of
the residual risks identified in reviewing the final
design, considering the risks described in the preceding
subsections or otherwise known or foreseen by the
evaluator. Only those risks meeting the criteria in
SEMI S14-0704 © SEMI 2000, 2004 6
Appendix 1 should be included. For each identified
residual risk, the report should:
• explain the mechanism of loss or damage;
• identify aggravating or necessary contributing
factors;
• identify the mitigating factors;
• state the assigned Severity for each type of loss and
present the rationale for its assignment. A “type”
is a column in Table A1-1, e.g., “Equipment
Physical Damage”;
• state the assigned Likelihood and present the
rationale for its assignment; and
• state the resulting Risk category.
NOTE 18: Criteria for risks may be found in Appendix 1,
Sections A1-2.5 through A1-2.8.
6.5.3.2 This report should also describe the fire risk
mitigation techniques included in the equipment design.
6.5.3.3 The final fire risk assessment report should be
prepared or reviewed by a party qualified, as described
in SEMI S7, to do such work.
NOTE 19: This party may be an employee of the equipment
supplier or may be a third party.
6.5.3.4 When this guideline is being used as part of a
SEMI S2 equipment evaluation, the manufacturer
should make the final fire risk assessment report avail-
able to the party performing the SEMI S2 evaluation.
6.5.3.5 The equipment supplier may make the final fire
risk assessment report available to other parties.
6.5.4 Summary Report
6.5.4.1 The summary report should be prepared from
the final fire risk assessment report and contain:
• a list of the residual fire risks and their ratings, and
• brief descriptions of the fire risk mitigation
techniques included in the equipment.
6.5.4.2 The equipment supplier should provide the
summary report to users of the equipment and may
provide it to other parties.
7 Fire Risk Mitigation
7.1 Overview
7.1.1 This section describes several means of
mitigating the risks of fire. It describes ways in which
the equipment and its use can be designed to minimize
the risks.
NOTE 20: The description of a mitigation technique in this
section is not intended to imply that such technique should be
used for each system. Therefore, the decision to include a
particular mitigation technique should be based on the
assessed risk.
NOTE 21: Fire detection and suppression are also means of
mitigating fire risk. The criteria for fire detection and
suppression systems are in SEMI S2.
7.1.2 In mitigating risks, the general hierarchy of
elimination, engineering controls, administrative
controls, warning and work practices should be
followed. Following this hierarchy comprises using
techniques which are highest in it if several techniques
are equally applicable. Design and use constraints, as
well as relative cost, however, may justify using
techniques from generally less preferable categories. In
any case, the residual risk should be assessed and
reported.
7.2 Fuels
7.2.1 Materials of Construction
7.2.1.1 The lowest fire risk is posed by noncombustible
materials of construction. Available noncombustible
materials are not, however, suitable or desirable for all
applications within semiconductor manufacturing
equipment.
NOTE 22: The properties necessary to perform the intended
function of system components and the properties necessary
to satisfy component-level standards may also restrict the use
of noncombustible materials.
7.2.1.2 When materials which are combustible are
chosen, the fire risk may be mitigated by:
• selecting those materials with the least undesirable
properties as described above; and
• minimizing the total mass and distribution of such
materials.
7.2.2 Process Chemicals
7.2.2.1 It may be possible to reduce the fire risk by
changing the quantities and species of the chemicals
used in the intended processes.
7.2.3 The fire risks of combustible materials of
construction and flammable and combustible process
chemicals may also be reduced by limiting those factors
described in Section 6.
7.3 Sources of Ignition
7.3.1 Potential sources of ignition should be considered
in conjunction with the fuels and oxidizers they might
ignite.
7.3.2 Risks due to sources of ignition can be mitigated
by:
• limiting their number,
SEMI S14-0704 © SEMI 2000, 2004 7
• limiting their energy, and
• separating them from combustible materials of
construction and from flammable and combustible
process chemicals. Separation may be by distance
or by barriers.
7.3.3 Equipment in which flammable liquids or gases
are used should be assessed to determine if additional
precautions (e.g., purging) in the electrical design are
necessary.
NOTE 23: NFPA 497 and EN 1127-1 are among the
documents that provide methods for making this assessment.
7.4 Oxidizers
7.4.1 Reducing the quantities or pressures of oxidizing
process chemicals may reduce the fire risk.
7.4.2 The fire risks of oxidizing process chemicals may
also be reduced by limiting those factors described in
Section 6.
7.5 Exhaust, Enclosures and Barriers
7.5.1 Mechanical exhaust may reduce the risk of
damage to the facility, other equipment, or other
portions of the same equipment by limiting the spread
of combustion and decomposition products. The
mechanical exhaust could be provided by the
equipment or by the facility.
7.5.2 Enclosures and barriers within the equipment
may reduce the fire risk by separating the fuels and
oxidizers from each other and from potential sources of
ignition.
7.5.3 These design features may also limit the spread
of fire, reducing both the loss of equipment and the
emission of combustion and decomposition products.
8 Related Documents
8.1 SEMI Standard
SEMI S11 — Environmental, Safety, and Health
Guidelines for Semiconductor Manufacturing Equip-
ment Minienvironments
8.2 NFPA Documents
National Fire Protection Association: NFPA 70 —
National Electric Code (NEC)
National Fire Protection Association: NFPA 318 —
Standard for Protection of Cleanrooms
National Fire Protection Association: NFPA 496 —
Standard for Purged and Pressurized Enclosures for
Electrical Equipment
National Fire Protection Association: NFPA 497 —
Recommended Practice for the Classification of
Flammable Liquids, Gases, or Vapors and of
Hazardous (Classified) Locations for Electrical
Installations in Chemical Process Areas
8.3 CEN/CENELEC Standards
4
EN 1127-1 — Explosive Atmosphere – Explosion
prevention and protection – Part 1 Basic concepts and
methodology
8.4 Other Documents
Building Officials and Code Administrators (BOCA)
5
,
NBC: National Building Code
Factory Mutual System Data Sheet 7-7
6
, Semiconductor
Fabrication Facilities
International Conference of Building Officials (ICBO)
7
,
UBC: Uniform Building Code
International Fire Code Institute
8
, UFC: Uniform Fire
Code
International SEMATECH
9
, Process Compatibility
Parameters for Wet Bench Plastic Materials
(Technology Transfer # 98123623A)
Southern Building Code Congress International
(SBCCI)
10
, SBC: Standard Building: Code
4 European Committee for Standardization (CEN)/European
Committee for Electrotechnical Standardization (CENELEC), Central
Secretariat: rue de Stassart 35, B-1050 Brussels Belgium
5 Building Officials & Code Administrators International, Inc., 4051
West Flossmoor Road, Country Club Hills, IL 60477
6 Factory Mutual, 1301 Atwood Ave. P.O. Box 7500 Johnston R.I.
02919, website: www.fmglobal.com
7 ICBO, 5360 South Workman Mill Rd., Whittier, CA 90601
8 International Fire Code Institute, 5360 South Workman Mill Rd.,
Whittier, CA 90601
9 SEMATECH, 2706 Montopolis Drive, Austin, TX, website:
www.sematech.org
10 SBCCI, 900 Montclair Rd, Birmingham, AL 35213-1206