semi合集-English.pdf - 第7073页
SEMI S18-1102 © SEMI 2002 11 automate d switching sy stem shoul d be employed for the system. 14.3.7 Flow Limit ing Devices sh ould be only as large as necessary to meet pr ocess flow requirements. NOTE 39: UFC 80-1 requ…
SEMI S18-1102 © SEMI 2002
10
13.2.4 A cylinder should be secured to the structure
(directly or indirectly) with at least two non-
combustible securing devices positioned to prevent
cylinders from falling sideways as might be
experienced when only a single device is installed.
NOTE 31: Jurisdictions may impose additional requirements.
14 Supply Systems
14.1 Bulk Silane — Bulk silane supply systems should
incorporate the following features:
14.1.1 Location and Construction
14.1.1.1 The container and its peripherals should be
constructed outside of buildings with set back from
buildings and property lines as required by NFPA 318
or regulation. An example of the recommended layout
is shown in Figure 1.
NOTE 32: There may be some jurisdictions that require more
separation than NFPA 318.
NOTE 33: Additional protective barriers may be required to
shield nearby structures or activities from potential flying
objects.
14.1.1.2 A full risk assessment should be performed to
determine if there are other risks with the location such
as vehicular traffic and sabotage.
14.1.1.3 The storage configuration should be of open
construction and have natural ventilation that does not
allow for pocketing of silane that could result in
explosion, unless regulations require enclosures.
14.1.1.4 Bulk silane systems should be separated from
each other and from the regulator station by 2-hour-
rated firewalls.
14.1.2 Access control should be installed to protect
from unnecessary approach of persons.
14.1.2.1 The storage area should have at least two
exits.
14.1.2.2 Workers from the gas supplier and trained site
personnel should be the only persons authorized to
work in a bulk silane gas area.
14.1.3 Controls and Safeguards
14.1.3.1 The arrangement of piping, valving, controls,
and valve manifold boxes as recommended for
liquefied silane Gas Bulk system should be considered.
14.1.4 Flow Components
14.1.4.1 The Flow Limiting Device [e.g., restricted
flow orifice (RFO)] size used in bulk systems should be
as small as possible to meet combined process needs.
NOTE 34: Combined process needs include the influences of
the length of the delivery line.
14.1.4.2 A Flow Limiting Device should be placed in
the outlet valve of the delivery manifold from the tube
trailer.
14.2 Liquefied Silane Family Gas Bulk Systems
14.2.1 Liquefied silane family gas bulk systems should
be equipped with the following controls and safeguards:
a) Excess flow protection,
b) Secondary containment for spills,
c) A manual shutdown valve at both the point of
supply and the point of use and dispensing,
d) Overpressure monitors with pressure relief
and automatic gas shut off, and
e) A system to prevent overfilling for automated
delivery systems.
14.2.2 If heating mechanisms for liquefied gas
containers are required, over-temperature interlocks
should be provided. Indirect heating is recommended.
14.3 Gas Cylinder (Rack) Systems
14.3.1 Open dispensing racks for silane should not be
located in rooms inside the building.
14.3.2 Exterior dispensing areas should be separated
from structures in accordance with Figure 2. The
dispensing area should be open on at least three sides
with cylinders secured to steel frames. Where a canopy
is provided, the height should be a minimum of 3.7 m
(12 ft). [NFPA318].
14.3.3 The construction or location of the on-line
cylinder system should not inhibit safe cylinder
transfer.
NOTE 35: Jurisdictions may impose additional requirements.
14.3.4 A system of controls regarding how many and
which cylinders are on-line should be implemented.
This includes how many cylinders can be connected in
any given bundle as well as the size and capacity of
cylinders.
14.3.5 Cylinders should be equipped with normally
closed automatic pneumatic shutoff valves and
restricted flow orifices.
NOTE 36: The industry has moved almost exclusively to this
condition.
NOTE 37: For cylinder pack systems, a gas detection system
may be required by some jurisdictions. The detection should
close all cylinders ESOVs upon activation.
NOTE 38: An example of the recommended arrangement in a
cylinder gas supply system is shown in Related Information 3.
14.3.6 If multiple cylinders are used, in parallel, for
continuous supply during a cylinder replacement, an
SEMI S18-1102 © SEMI 2002
11
automated switching system should be employed for
the system.
14.3.7 Flow Limiting Devices should be only as large
as necessary to meet process flow requirements.
NOTE 39: UFC 80-1 requires maximum 0.010-inch orifice
for cylinders in silane service.
14.3.8 Cylinder Systems Using Gas Cabinets
14.3.8.1 Exhaust Requirements
14.3.8.1.1 A forced exhaust system should be provided
for cabinets. Air flow should be directed across
potential leak points to prevent pocketing.
NOTE 40: Recommendations for cabinet exhaust are
provided in RI-2.
14.3.8.1.1.1 The forced exhaust system for silane
family gas should have capability of treating worst case
leak. The treatment may be accomplished by either an
abatement system or dilution of silane family gas to
below 25% of the lower flammable limit.
14.3.8.1.1.1.1 A worst case leak is typically a full-flow
release rate from the largest cylinder installed through
the Flow Limiting Device at full cylinder pressure.
14.3.8.1.2 The exhaust system should be provided with
automatic emergency source of backup power.
NOTE 41: Jurisdictional requirements may define backup
power.
NOTE 42: Many jurisdictions require sensors, detectors, and
lighting fixtures all to be of electrical construction meeting
hazardous location requirements (e.g., not less than NEC
Class 1 Div. 2.) in rooms classified as flammable rooms.
NOTE 43: In some jurisdictions, the exhaust and abatement
system may not be required to operate continuously, provided
when a leak is detected, the forced exhaust and abatement
system be activated to abate the leak.
14.3.8.2 Mechanical ventilation should be provided for
the gas cabinet to keep inner pressure of the cabinet
negative to atmosphere. The effectiveness of the
ventilation should be monitored.
14.3.8.3 Vent lines of the high pressure side of the
regulator of silane family gas cylinders should be
routed to an abatement system when applicable to meet
jurisdictional requirements. The system should have the
capability to abate the largest possible flow through the
cylinder flow restrictor.
14.3.8.4 Excess flow switches should be provided
upstream of the regulator, either in conjunction with
high pressure process valves or on the pigtail
immediately downstream of the cylinder valve. This is
to limit the maximum flow of gas to the regulator.
14.3.9 Special Cylinder Issues
14.3.9.1 Cylinder Change Procedures
14.3.9.1.1 A well defined method of leak checking
should be performed after a new cylinder is installed
and prior to final pigtail purging to insure cylinder
connection leak-tight integrity.
14.3.9.1.2 Appropriate personal protective equipment
(PPE) should be worn during cylinder handling and
changing.
14.3.9.1.3 Before opening the cabinet door to replace a
cylinder, a visual inspection for silicon dioxide (SiO
2
)
powder should be performed. If SiO
2
is present, it is
evidence of a leak in the system, and the door should
not be opened until the gas supply is shut off and, if
possible, purged remotely. Adequate precautions should
be taken as trapped pockets of silane may ignite.
14.3.9.2 Cylinder should be transported with the
cylinder valve plug securely tightened and the cylinder
valve protective cap in-place.
14.3.9.3 Cylinder replacement should be performed by
two persons. Each should have received appropriate
training to perform their tasks safely.
14.3.9.4 Cylinders should be transported on
appropriate carriages with adequate means for fixing
the cylinder to the carriage.
14.4 Changing Sources
14.4.1 To prevent air from entering a silane family gas
system during container change, a constant purge of the
connection should be operating during the entire time
the supply is not connected.
14.4.1.1 To prevent accidental intake of air into the
source container, the source container pressure should
be maintained above atmospheric pressure and replaced
by new one before the pressure drops to atmospheric
pressure.
14.4.1.2 At a certain minimum pressure, a warning
should be provided to an attended location and the gas
shut down.
14.4.2 Auto-sequence Controllers Auto-sequence
controllers are recommended whenever possible to
reduce the potential for human error in supply change-
out.
14.4.2.1 When an auto sequence controller is used, the
leak test after replacement of the cylinder should be
designed to monitor the pressures continuously within
the purging supply system. Interrupted monitoring may
not capture a pressure change that indicates ineffective
purging.
SEMI S18-1102 © SEMI 2002
12
14.4.2.1.1 The design of automatic-sequence control
systems for cylinder cabinets should incorporate the
following features:
a) Fault-tolerant design,
b) The ability to perform a leak check of the
container by measuring pressure rise in the
system, with the container valve closed, under
the condition that the container has been
connected and the purge gas eliminated,
c) Continuous pressure monitoring of the system
during all purges and operating conditions, and
d) Written procedures for safe source container
replacement including verification
requirements for the leak testing and
verification of the sensing system function.
NOTE 44: All tasks assessed as high risk (from the risk
assessment) should minimize human interaction as much as
possible.
15 Distribution Systems for Gas Supply
15.1 General Considerations
15.1.1 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, if not connected to the purge
gas, should be sealed with a cap or plug.
15.1.2 Dead leg sections (internal piping which can
trap silane family gases) should be minimized to the
smallest volume possible.
15.1.3 An excess flow control valve should be installed
on every silane family gas piping system as close as
practical to the source. The excess flow control valve
should be sized to deliver only as much gas as
necessary to the process requirements.
NOTE 45: See Related Information 3 for an example.
15.1.3.1 Silane family gas delivery systems should be
equipped with the following controls and safeguards:
a) Excess flow protection,
b) A manual shutdown valve at both the point of
dispensing and in the distribution line near or
in the equipment gas box, and
c) Over-pressure monitors with pressure relief
and automatic gas shutoff when pressure is
detected above the designed limit.
15.2 Location and Construction
15.2.1 Piping General
15.2.1.1 Piping should be welded throughout or
contained within an exhausted enclosure.
EXCEPTION: Non-welded piping, outdoors, may not require
an enclosure.
15.2.1.2 Piping should be labeled with the gas name
and flow direction.
15.2.1.3 If the piping diverges into two or more lines,
each line should be provided with a shut off valve.
NOTE 46: Some jurisdictions require both manual and
automatic shut off valves.
15.2.1.3.1 These valves should enable cycle purging of
each line.
15.2.1.3.2 These valves should be provided with an
exhausted enclosure.
15.2.1.3.3 The enclosure should be monitored with
detectors for the silane family gases present.
15.2.1.4 The ventilated enclosures should have exhaust
monitoring per SEMI S2.
15.2.1.5 The piping of oxidizer gases should be
isolated from the piping of silane family gases. The
isolation should also be applied to silane family gas
purge lines.
15.2.2 Coaxial Piping
NOTE 47: Some jurisdictions require building-runs of silane
family gas piping to be of secondarily contained (coaxial)
construction. Some believe there is little evidence that
coaxial piping for these gases is appropriate, as long as non-
welded fittings are within secondary enclosures. Coaxial
piping may add substantial costs and other hazards which
should then be addressed. However, pressurized, monitored,
and interlocked coax lines provide a local warning to persons
who accidentally damage the jacket. The sound of the
escaping inert gas used to pressurize the jacket alerts the
worker. The interlock alerts the facility of the breach, and
reduces the total amount of process gas lost if the inner line is
damaged.
15.2.2.1 When coaxial piping is installed, the annular
space should be pressurized with helium or other inert
gas, purged, or maintained at a vacuum.
15.2.2.2 If a purge method is used, the purge gases
from the coaxial piping should be monitored with
detectors for the specific silane family gas.
15.2.2.2.1 This detector should shut down the source
when a leak is detected.
15.2.2.3 If a pressure or vacuum method is used, the
pressure or vacuum in this annular space should be