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SEMI S18-1102 © SEMI 2002 14 16.1.6.4 A hazard analysis of the system, beyond t he safe-state shut off, should be u sed to determine adequate prote ction. 16.1.6.5 No single component failure shou ld allow for incompatib…
SEMI S18-1102 © SEMI 2002
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monitored and should alarm at a constantly attended
location when a change occurs.
15.2.2.3.1 The alarm should also shut off the silane
family gas at the nearest up-stream valve.
15.2.2.4 A procedure for responding to an annular
space alarm, and determining the nature of the hazard
condition, should be created.
15.3 Flow Components
15.3.1 The state of a valve (open or closed) should be
indicated through display or on the valve itself. The
supplier should provide the user with reliability data for
repeated operations, and the user should replace the
valve within its expected lifetime.
15.4 Heaters and Heat Insulation Materials —
External heating of piping and regulators may be
required in outside locations or long distance lines to
prevent re-liquification. In such cases, the following
should be considered:
15.4.1 If electrical resistance heating is used with
insulation, the insulation should be visually inspected
periodically for degradation or exposed wiring to avoid
electrical arcing and damage to the piping.
15.4.1.1 Electrical resistance piping heating systems
should not be placed in wet areas because of the
increased possibility of damage from corrosion.
15.4.2 Electrical resistance piping heating systems
should be monitored. Monitors should alarm in the
event of over temperature, an open circuit or a short
circuit and should shut off the power supply and gas
supply.
15.4.2.1 Gas supply shutdown may be required by
some jurisdictions.
NOTE 48: Heaters must conform to jurisdictional
requirements for the device type.
16 Equipment Using Silane Family Gases
16.1 Design
16.1.1 Coaxial piping within process equipment is not
usually practical, but piping between equipment gas
box and process chambers should be coaxial piping if
the piping is both pressurized and outside of exhausted
and leak-monitored enclosures.
16.1.2 Safe State Equipment should be designed so
that detection of a silane release immediately sends the
equipment into a safe state. Safe shutdown of the
equipment itself or silane family gas sources may be
appropriate.
16.1.2.1 Any silane process vacuum pump, when used,
should be maintained and monitored for its ability to
safely remove potentially hazardous silane family gases
from equipment for maintenance and repair.
NOTE 49: For fire detection, suppression, and alarm criteria
see Section 9.
16.1.3 Fire detection system activation should shut off
flammable and pyrophoric gases supplying the
equipment being monitored, as this is the only safe
method of extinguishing gas fires.
16.1.4 Equipment using silane family gases should be
capable of performing a purge/vacuum sequence to
purge the silane family gas to prevent chemical reaction
damage before service or maintenance.
16.1.4.1 The minimum number of purge/vacuum
cycles should be decided according to the results of
tests that evaluate the sequence effectiveness.
16.1.4.2 The equipment supplier should provide the
minimum safe number of cycles to the user based upon
the baseline process.
16.1.4.3 If adjustable, this minimum number of cycles
should be controlled in such a way that the user is
aware of the consequences of changing the cycle count,
and access to the means of changing the cycle count is
limited to maintenance or service personnel, but not
operators.
16.1.5 When the appropriate number of purge cycles
for the user’s own process are determined by the user,
the number should not be less than the minimum
number of cycles recommended by the equipment
supplier.
16.1.5.1 If unusual circumstances appear to reduce the
number of cycles needed, the supplier should be
consulted for a recommendation specific to the
circumstances.
16.1.6 If a system is designed to supply a silane family
gas and a gas with which the silane family gas can
react, to a chamber simultaneously, the flows should be
controlled to avoid concentrations and pressures of
those gases that would pose unacceptable risks.
16.1.6.1 The equipment should be designed so that it
will not initiate the next process step if a gas mixture
condition that would pose unacceptable risks exists.
16.1.6.2 The equipment should not allow additional
gas to flow until any unsafe gas condition alarm has
been manually reset.
16.1.6.3 Silane family gases and incompatible gases
should have separate piping up to the point where a
system EMO or a safe-state function can shut them off.
SEMI S18-1102 © SEMI 2002
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16.1.6.4 A hazard analysis of the system, beyond the
safe-state shut off, should be used to determine
adequate protection.
16.1.6.5 No single component failure should allow for
incompatible gases to mix, in manifolds or other areas,
in pressures and concentrations that would pose
unacceptable risks.
16.2 Construction
16.2.1 Equipment interface points for the gas supply
piping should be designed with seismic bracing as
needed to achieve the seismic protection detailed in
SEMI S2.
16.2.1.1 The external force on the bending point should
be minimized by use of reverse bending or other
methods.
16.2.1.2 The tensile strength of joints should be
compliant with the appropriate piping standard for the
jurisdiction (such as ASTM/ANSI, ISO, or JIS).
16.2.2 Dead leg sections (internal piping which can
trap silane family gases) should be minimized to the
smallest volume possible.
16.2.3 Chambers intended for silane family gas
processes should be evaluated for their ability to
withstand reasonably foreseeable events related to the
silane family gases such as fire or explosion that arise
from single point failures.
16.2.3.1 If viewing ports are used they should be
designed to the same capability as the chamber, or be
provided with safety devices to capture any potential
flying debris before it affects personnel or other
equipment.
16.2.3.1.1 If viewing ports are intended to be user
replaceable, the user documentation should specify the
part and the change procedure and warn the user of the
possible consequences of using an alternate part.
16.2.3.2 If an enclosure is required to contain chamber
rupture, such an enclosure should be ventilated and
evaluated per SEMI S2 and SEMI S6.
16.2.3.2.1 If the chamber rupture protection is an
enclosure, the enclosure panels should be interlocked to
prevent process initiation or continuance if the
enclosure is open.
16.2.4 Flame sensors or leak detectors should be
installed in all areas that may accumulate silane family
gases from a leak.
16.2.5 The results of the tracer gas tests specified in
SEMI S2 and SEMI F15, should indicate that ambient
concentration of silane family gases will be less than
the level specified in SEMI S2 during maintenance
activities or delivery system failure.
16.3 Vacuum Pump Systems
16.3.1 Materials of construction for vacuum pumps
that are exposed to the gas stream should be compatible
with the gas stream.
16.3.2 Vacuum pumps that are exposed to the gas
stream should be dry type or use inert (non-
hydrocarbon) oil.
16.3.3 Purge gases for vacuum pumps should be
nitrogen (N
2
) or other inert gas. The flow rate of the
purge gas should be sufficient to dilute the silane family
gas to below the lower explosive limit until the gas has
safely passed into the burn box or abatement system. If
a combined pump/abatement system is used, this
criterion is not applicable.
16.3.3.1 The flow rate of purge gas flow should be
interlocked to shut off the silane family gases if the
purge gas flow drops below the amount needed to
insure adequate dilution.
16.4 Protection
16.4.1 Fire Detection and Suppression
16.4.1.1 Use the results of the risk assessment
described in SEMI S14 to determine the need for fire
detection and suppression.
16.4.1.2 Fire detection and suppression system(s)
should be operational at all times, including when
equipment or facilities are shut down or in maintenance
mode.
EXCEPTION: Maintenance of the fire detection system.
16.4.2 As for any other safety design consideration
aspect of process equipment, SEMI S2 provides criteria
for assessing and managing safety risks.
16.5 Information on Exhaust
16.5.1 The equipment supplier should provide exhaust
information to the user. The information should be
based on the baseline process including:
• the chemicals and their composition,
• compatibility requirements and type of connection
expected at outlet of the vacuum pump,
• the potential hazards expected if duct is open to air
during the maintenance,
• recommended maintenance procedures when the
equipment is connected to a point-of-use gas
treatment system,
SEMI S18-1102 © SEMI 2002
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• recommended duct size and flow volumes, based
on the suppliers recommended base process,
• information on potential maintenance issues
associated with the process (such as silicate
deposits and reactive by-product generation),
• The probable hazards that would be generated by
exposure of open ducts to air during maintenance
activities,
• maximum distance from the reaction chamber to
the vacuum pump, and
• maximum distance from the pump to the exhaust
connection or the point-of-use abatement.
16.5.2 The need to route the residual gas and by-
products to the proper gas treatment system may require
consideration of separate pump systems for
incompatible gases.
16.6 Other Information
16.6.1 Manuals as defined in SEMI S13, should
include information and training requirement on silane
family gases, their hazards, and recommended
protective measures.
16.6.2 Hazard warning labels should be designed in
conformance to SEMI S1. Where such labels are to be
placed should be decided per SEMI S2.
17 Exhaust Systems and Plumbing
17.1 Design
17.1.1 Enclosure Exhaust System — Exhaust piping for
the gas panel enclosure or the pump enclosure may be
required to be separated from heat exhaust line to
prevent the possibility for mixing of incompatible
chemistries before dilution.
NOTE 50: Separation of exhaust systems may be required by
certain jurisdictions.
17.1.1.1 Air velocity for an enclosure should be
calculated to minimize collection of silane family gases
into pockets.
NOTE 51: Information to decide what amount of air velocity
should be needed is provided through Related Information 2.
Document such as CGA P32-2000 and NFPA318-2000
provides similar information.
NOTE 52: Some regulations may require minimum velocities
until new research (SSA Journal, Spring and Winter 1998)
can be incorporated into the regulations. This minimum
velocity is not less than 1.0 m/sec for the overall enclosure,
and air velocity across any potential leakage point is not less
than 0.5 m/sec.
NOTE 53: Recommendations for gas cylinder cabinet
exhaust provided in Related Information 2 can also be used
for enclosures within process equipment. For the purpose of
enclosure exhaust calculations, gas delivery pressure to the
enclosure should be used as the “source pressure” in Figure 3
of Related Information 2.
17.1.2 Process Exhaust Systems
17.1.2.1 Materials of construction should be
compatible with the hazards presented by the silane
family gases present.
17.1.2.2 Materials for exhaust piping containing silane
family gases should be compatible with the byproducts
and should provide protection from heat and reactions,
which may be present when silane family gases exit a
reaction chamber.
17.1.2.3 No combustible joint compound (including
adhesive or tape) should be used to seal joints.
17.1.2.4 Process exhaust piping should withstand the
maximum potential pressure generated by the reaction
of respective silane family gases in a reasonably
foreseeable worst case, single-point failure at the
process equipment.
17.1.3 Metal-gasket face-seal fittings should be used
wherever possible. Compression fittings lead to
increased risk of leaks, especially when subjected to
expansion and contraction by internally burning and
extinguishing silane family gases.
17.2 Protective Devices
17.2.1 Mechanical fittings in pressurized exhaust or
treatment system should be enclosed in exhausted
enclosures, like any supply piping. Leaking can be
caused by the result of assembly and disassembly
during pump and treatment system maintenance.
17.3 Maintainability
17.3.1 Maintenance personnel should inspect for
liquids and solids collecting in exhaust ducts to prevent
accidents resulting from the build-up of reaction
products.
17.3.2 Ports for chemical sampling should be provided
in order to enable inspection of deposits and sampling
of gas composition and concentration in the exhaust
duct.
17.3.2.1 Ports, if not connected to a sampling device,
should have a stop valve and should be sealed with a
cap or plug.
17.3.2.2 This monitoring should be performed
periodically to insure gas composition and quantities
have not generated new hazards and to characterize gas
deposits and ensure they are being removed.
17.3.2.3 View ports also require periodic cleaning to
provide for adequate viewing capability. If the gas is