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SEMI S18-1102 © SEMI 2002 5 6.5.3.3 The user should in troduce silane family gases only after pu rging oxidizing ga ses and other incompatible gases, materials or substances from the system. 6.5.3.4 Silane family gas sys…
SEMI S18-1102 © SEMI 2002
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moisture, corrosivity can radically increase and
pyrophoric byproduct gases might also be produced.
NOTE 2: The most recent and best research on DCS puts the
AIT (Auto Ignition Temperature) at 44 degrees C plus/minus
3 degrees C, or about 111 degrees F. It should be noted
however, that unlike silane, DCS is not expected to autoignite
in almost all ambient conditions where we would find it in
use. For fire protection purposes it can be treated as a highly
flammable gas.
6.2 Risk Management Strategies Fundamental
concepts of safety and accident prevention are:
6.2.1 An understanding of facilities, piping and
equipment, from storage to gas abatement, is essential
for safe handling of silane family gases in
semiconductor or FPD manufacturing facilities.
6.2.2 The safety of facilities can be enhanced by
implementation of designs for sources, piping and
equipment that use devices with fail-safe, foolproof,
self-diagnostic and predictive functions.
6.2.3 Safety systems should detect current safety status
and generate notices that indicate conditions of elevated
risk, through computer self-diagnosis and dedicated
SSCS devices. If the SSCSs cannot confirm normal
operation of assigned silane family gas handling system
or unit, the silane family gas supply should
automatically be shut off.
6.2.3.1 SSCSs can determine if a safe status has been
achieved before proceeding to the next step in a silane
family gas handling process.
6.2.3.2 SSCSs should be provided in distribution
facilities, cylinder cabinets, process equipment, gas
treatment systems, and the like.
6.2.4 Safe design depends on equipment designers’ and
facilities designers’ understanding of silane family gas
properties and hazards. Design methods for controlling
these hazards require full integration of measures from
all portions of the delivery and use systems.
NOTE 3: Information on silane family gases’ hazards is
available from various sources, including: regulations,
MSDSs, Factory Mutual Loss Prevention Data Sheets, NFPA
Standards, consensus Building Codes, and various research
papers.
6.2.4.1 The supplier should complete, prior to use, a
hazard identification and risk assessment [such as
Process Hazard Analysis (PHA), Hazard and
Operability Analysis (Haz-Op), Failure Mode Effects
Analysis (FMEA)], for all silane family gas systems.
6.2.4.2 The results of the analysis should be reported
using the SEMI S10 risk matrix.
6.2.5 Minimization of Quantity The quantity of any
silane family gas online and in use should be limited to
the smallest amount necessary for effective production.
NOTE 4: Separation and setback considerations for silane
family gas storage and dispensing areas must be in
accordance with jurisdictional requirements.
6.2.6 Periodic accident prevention assessments should
be performed to assist in minimizing incident
frequency.
6.3 Isolation (Lockout/Tagout) Isolation (“lock
out/tag out”) capability should be provided for all silane
sources at all levels necessary to perform service or
maintenance safely on silane family gas systems.
6.3.1 Energy isolation of all other energy sources (e.g.,
electrical, mechanical) should be performed, as
appropriate, to provide safety for personnel working on
energy systems associated with silane family gases.
NOTE 5: Maintenance on energized non-hazardous electrical
systems may not be safe when a silane family gas is present in
the system.
6.4 Access Control
6.4.1 Multiple level access control, to each point where
any hazard may exist in a normal or failure state, should
be provided for all silane family gas systems.
6.5 All personnel concerned in silane family gas
handling should be trained for the jobs they are to
perform and hazards to which they will be exposed. All
such training should be formally documented and if
regulations apply then the documentation should be in
accordance with the regulations.
6.5.1 Audits of system status and equipment condition
should be performed and documented on a periodic
basis.
6.5.2 The operator or technician should be capable of
checking the current status and any abnormal condition
before beginning work on any system or sub-system.
6.5.3 Evacuation and Purging
6.5.3.1 When connecting silane family gas piping to
equipment, the air in the piping should be purged out
with inert gas such as nitrogen into a safe location to
prevent reaction with silane family gases.
6.5.3.2 To enable purging without venting into unsafe
locations, a purge port should be installed at locations
where sealed systems require purging. Purge ports
should have a stop valve and, if not connected to the
purge gas, should be sealed with a cap or plug.
SEMI S18-1102 © SEMI 2002
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6.5.3.3 The user should introduce silane family gases
only after purging oxidizing gases and other
incompatible gases, materials or substances from the
system.
6.5.3.4 Silane family gas systems should have
procedures based on calculated minimum purge cycles,
minimum purge-gas pressures, and necessary vacuum
levels to insure the system has been adequately purged
before being opened to atmosphere. Calculations are
needed to define minimum number of cycles. Process
purges typically far exceed this number of cycles,
therefore testing is usually not necessary.
6.5.3.5 An adequate means should be provided to avoid
a cross contamination of purge gases and the process
gases by accidental backflow.
6.5.3.6 Separation of purge gas and silane family gases
should not solely depend on check valves. A control
valve, such as a pneumatic valve placed before or after
the check valve, is preferred for isolating silane family
gases from other gases during procedures that might
allow reverse flow.
6.5.4 The purge gas for silane family gases should be
supplied from dedicated source containers.
NOTE 6: Some regional codes (e.g., Japan’s High Pressure
Gas Safety Law) require a purge gas source which is totally
separated from the purge gas source for oxidizer gas lines.
6.5.4.1 Purge lines from dedicated bulk supplies
(where allowed at all by the jurisdiction) should have
multi-level back-flow and pressure differential
protection to prevent potential back-flow of pyrophoric
gases into bulk systems.
NOTE 7: Back-flow into these bulk purge systems has been
known to generate ignitable mixtures when the inert gas is
exposed to atmosphere far from the source of contamination.
7 Education and Training
NOTE 8: It is important for managers as well as employees
to deepen their understanding of the characteristics of gases
that they handle, so as to ensure safe work practices. If
employees do not handle gases, this section is not applied.
7.1 Everyone who handles silane family gases should
be specially educated about the hazardous properties
and safe handling methods of these gases.
NOTE 9: Some jurisdictions (such as Japan) require that
users of “specialty high-pressure gases” provide special safety
education to their employees.
7.1.1 In regard to safety education and training, each
organization should create the curricula or obtain
approved curricula for education and training, assign a
person responsible for education and training, and
implement a periodic training plan.
7.1.2 Instructors should be persons who have sufficient
knowledge and experience about the hazards, use and
safe control of silane family gases.
NOTE 10: It may be necessary to request the assistance of
outside experts, depending on an organization’s capabilities.
7.1.3 Training should include safe use, handling,
hazardous properties and by-products and emergency
procedures of process gases as well as case studies of
past accidents.
7.1.4 Training should be performed periodically and
the training results documented.
7.2 Equipment and facilities suppliers, maintenance
service providers and users should establish education
curricula for job specific environmental, safety, and
health (ES&H) education programs, train their
personnel, and keep records or issue certificates.
7.3 Maintenance personnel should be fully trained in
their own areas of responsibility.
7.3.1 Maintenance personnel should understand the
overall design of facilities and equipment for silane
family gases.
7.3.2 Energy isolation (“lock out/tag out”) training
should be provided to all employees who are expected
to perform service or maintenance on silane family gas
systems.
7.4 Training curricula, should be requested from the
responsible party (constructor, facility manager, or
equipment manufacturer) as part of the purchase
specifications.
7.4.1 Each party should have qualified persons to train
personnel working in their facility.
NOTE 11: It may be necessary to request the assistance of
outside experts to perform training, depending on an
organization’s capabilities.
NOTE 12: Responsible persons for each party must be
trained as required by regulation.
7.5 Training of persons performing periodic
inspections should be provided to ensure the
inspections are performed and documented properly.
NOTE 13: Ideally, information on safe design practices and
accident investigation summaries should be freely shared
across the industry, so the information can be provided, as
part of education and training, to all personnel who could
potentially be exposed.
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8 Leak Detection and Alarm Systems
8.1 General
8.1.1 Audible and visual alarms should be provided at
a location where they can be seen and heard by
workers.
8.1.2 Remote audible and visual alarms should be
provided at a constantly attended location so that
appropriate actions can be taken.
8.2 Silane Family Gas Leak Detection Practice
8.2.1 Leak can be detected directly with leak sensors
(gas detectors) or indirectly with heat or fire detectors.
NOTE 14: Sensor types include electrochemical, chemically
treated tape, chemiluminescence, ionization detection, and
UV/IR.
8.2.1.1 Gas detection should be capable of detecting
the silane family gas down to a level at least one-half of
the TLV
®
level.
8.2.1.2 Ultraviolet/Infrared (UV/IR) detectors may be
allowed in some jurisdictions.
8.2.1.3 If UV/IR detection is used, it should be
designed to focus its detection beam across all areas
within the silane family gas exhausted enclosure where
leaks may occur.
8.2.1.3.1 UV/IR detection may be able to detect the
heat signature at levels lower than detectable limits for
gas detectors in some situations.
8.3 Leak Detection Installation
8.3.1 The location of detection points should be
determined by considering airflow patterns, specific
gravity of the gas, surrounding conditions or barriers,
and equipment height.
8.3.2 A leak detection system should be installed with
detection points at intervals appropriate to the detection
technology, or as required by regulation, for exhaust
ducts or cylinder storage.
8.3.3 Leak detectors should also be placed:
• in gas cabinets at locations that will detect leaks
from the piping system or the cylinder,
• in gas manifold boxes for silane family gas
distribution systems, and
• to detect leaks within equipment gas boxes for
equipment using silane family gases.
8.3.4 Leak detectors should be provided or specified
for locations where potential exposure is anticipated
during maintenance or service, when the normal
detection points might not detect a release.
8.3.5 The number and location of detection points
should be determined from detector capabilities, and the
area (or volume) to be monitored by each detector.
NOTE 15: A detection point is a collection opening for a
suction type gas leak detection system or a detector for a
diffusion-type gas-leak detection system.
8.3.5.1 The coverage should be tested after installation
to verify performance.
8.4 Leak Detection Systems Characteristics
8.4.1 Leak detection systems should be fail safe.
8.4.2 Effective detection that can generate warnings
and alarms when a given concentration of gas is
detected.
8.4.3 Warnings, which may not activate the audible
and visual alarms, should be generated at a
concentration level equal to or below OEL or as
specified in an applicable regulation of the country of
use. Alarms, which do activate notifications and audible
and visual alarms, should be activated at OEL
concentration level. If the OEL value is not available
for a silane family gas, or if the value is impractical for
the system, the lowest detectable concentration
technically practical or the concentration set by an
applicable regulation should be used.
8.4.4 The system should be capable of detecting the
target gas beginning at a level at least ½ of the OEL,
and continuing to at least ½ IDLH (Immediately
Dangerous to Life and Health) levels.
8.4.5 A 10% voltage variation should not produce
more than a 30% change in the indicated concentration.
8.4.6 Detection should be capable of detecting a
release, within one minute of exposure of the detection
point, to a leak, which has a concentration above the
concentration of the warning or alarm level.
8.4.7 The alarm should continue, even if the
concentration varies after detection, until it is manually
reset.
8.4.8 Activation of the leak detection system in a gas
cabinet should close the automatic cylinder shut off
valve referenced in Section 14.3.5.
8.5 Maintenance
8.5.1 Gas leak detection and alarm systems should be
periodically inspected and maintained following the
procedures provided by the gas detection system
manufacturer.
8.5.1.1 Inspection and maintenance should be
recorded.