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SEMI F5-1101 © SEMI 1990 , 2001 20 from the s ections above. If on l y non-hazardou s gases are left these sys tems can provide cost-effective abatement to keep ducts clear. T hey can al so be used in combination with ot…

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SEMI F5-1101 © SEMI 1990, 200119
A2-5.1.4 Limitations — Fill material can also react
with oxygen or moisture so hot bed systems are not
always suited to wet processes or where air is used.
A2-5.2 Hot Catalytic Bed
A2-5.2.1 Principle of Operation — Gas is passed into
a steel cartridge, which is held at an elevated
temperature, that contains granules of a catalyst. The
target-input gas is catalytically converted to other gases
[e.g., ammonia (NH
3
) to nitrogen (N
2
) and hydrogen
(H
2
), and oxides of nitrogen (NOx) to nitrogen (N
2
) and
oxygen (O
2
)].
A2-5.2.2 Removal Capacity — In theory, if not
poisoned, a catalyst bed should last for a long time.
Units available are claimed to be able to operate for
one-year before bed change.
A2-5.2.3 Efficiency — Efficiency of hot catalytic bed
systems is normally high, with removal of the target gas
to below OEL levels.
A2-5.2.4 Limitations — Hot catalytic bed units are
designed to be gas specific. Catalysts can be sensitive
to other compounds; so for complex gas mixtures in
process exhausts they may not be suitable on their own.
A2-5.3 Hot Reactor Beds with Gas Inputs
A2-5.3.1 Principle of Operation — Exhaust gases are
passed into a hot bed as in hot bed reactors above, but
concurrently with the process gas another gas is
introduced (e.g., air or steam). The gases then react
together in the bed, either with each other or with the
bed material. Hazardous gases are converted either to
solid salts that remain fused into the bed matrix, or
other gases [e.g., carbon dioxide (CO
2
)] that pass on
into the exhaust.
A2-5.3.2 Flow Capacity and Removal Capacity —
Both capacities of these systems are a function of the
container (cartridge) size (mass of granules) and surface
area.
A2-5.3.3 Efficiency — Process gases [e.g., phosphine
(PH
3
), carbon monoxide (CO)] are normally removed to
below the OEL.
A2-5.3.4 Limitations — These systems are suited only
to processes where the end products will be either
stable solids or inert gases.
A2-6 Reactor Systems (Plasma, Microwave,
etc.)
A2-6.1 Principle of Operation — Gases are abated in
the vacuum line (before or after the vacuum pump) by
passing them through a reaction chamber, containing
plasma, to enhance reaction of gases such as silane into
a solid material. For high efficiency PFC conversion, it
is necessary to inhibit recombination by the addition of
a material (e.g., moisture, or a hydrogen/oxygen
mixture). Two types of reactors exist - large plasma
volume/small surface area, in which a downstream
particle trap is utilized; and small plasma volume/large
surface area, where solid films are deposited. Other
reactor systems (e.g., microwave systems) are also
being developed.
A2-6.2 Flow Capacity and Removal Capacity —
Reactor systems are designed for the process system
effluent and are sized to handle specific process flows.
A2-6.3 Efficiency — With inputs of up to 300 sccm of
silane, removal efficiencies of greater than 99% have
been documented. At higher flows efficiency can be
reduced. High removal efficiencies of PFCs have also
been demonstrated.
A2-6.4 Limitations — Silane will form solids in the
plasma. Gaseous by-products will pass into the
exhaust. Solids transmission into the vacuum pump
will be reduced, but additional abatement devices may
be required downstream if by-products need to be
removed. Formation of hydrogen (H
2
) as a by-product
should be considered to ensure that the H
2
outlet
concentration is below the lower flammable limit.
A2-7 Traps/Filters/Cyclones/Precipitators
A2-7.1 Principle of Operation — Designed to remove
the particulate component in exhausts. Some processes
produce solid powders (e.g., silica) and other processes
generate condensable vapors. These vapors, on
compression in the pump and cooling in the exhaust,
condense into solid materials. Numerous designs exist
to collect these solids out of the gas stream. These
include filters (paper/bag etc.), cooled condensation
chambers, cyclones, and electrostatic precipitators.
A2-7.2 Removal Capacity — Removal capacity is
normally measured as the mass of solid the unit can
collect before it partially blocks. As they are blocked,
these systems generate a backpressure, which can
prevent effective removal of material or create a
process disturbance.
A2-7.3 Efficiency— Efficiency for these various units
is difficult to measure. It is usually assessed
pragmatically in terms of increased interval between
exhaust clean out.
A2-7.4 Limitations— These various units must be used
with care and only when not associated with hazardous
gases. Often solid exhaust materials are mixed with
hazardous gases. If these gases are present in the
trapped solids a dangerous situation can result. Where
gases and solids are mixed it is safer to keep material
volatile and abate all by a POU abatement technology
SEMI F5-1101 © SEMI 1990, 2001 20
from the sections above. If only non-hazardous gases
are left these systems can provide cost-effective
abatement to keep ducts clear. They can also be used in
combination with other technologies.
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
the responsibility of the user. Users are cautioned to
refer to manufacturer' s instructions, product labels,
product data sheets, and other relevant literature,
respecting any materials or equipment mentioned
herein. These standards are subject to change without
notice.
By publication of this standard, Semiconductor
Equipment and Materials International (SEMI) takes no
position respecting the validity of any patent rights or
copyrights asserted in connection with any items
mentioned in this standard. Users of this standard are
expressly advised that determination of any such patent
rights or copyrights, and the risk of infringement of
such rights are entirely their own responsibility.
Copyright by SEMI® (Semiconductor Equipment and Materials
International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o
f
the contents in whole or in part is forbidden without express written
consent of SEMI.
SEMI F6-92 © SEMI 19921
SEMI F6-92
GUIDE FOR SECONDARY CONTAINMENT OF HAZARDOUS GAS
PIPING SYSTEMS
1 Purpose
To provide a guide for the design, fabrication, and
operation of secondarily contained distribution piping
for hazardous production material (HPM) gases.
2 Scope
This guide covers the general requirements for
hazardous production material distribution piping in
those industries that are included under the H-6
Classification of the Uniform Building Code, or
Articles 51 or 80 of the Uniform Fire Code, or of other
applicable local codes. This guide does not include
requirements for individual exhausted enclosures (e.g.,
valve boxes and gas cabinets).
3 Applicable Documents
3.1 SEMI Documents
SEMI F1 — Specification for Leak Integrity of Toxic
Gas Piping Systems
SEMI F2 — Specification for Seamless Austenitic
Stainless Steel Tubing for Semiconductor
Manufacturing Applications
SEMI F3 — Guide for Welding Stainless Steel Tubing
for Semiconductor Manufacturing Applications
SEMI S2 — Safety Guidelines for Semiconductor
Manufacturing Equipment
SEMI S4 — Safety Guideline for the
Segregation/Separation of Gas Cylinders Contained in
Cabinets
3.2 ANSI/ASME Standard
1
B31.3 — Chemical Plant and Petroleum Refinery
Piping
3.3 Federal Regulations
2
29 CFR — Title 29 of the Code of Federal Regulations
(CFR), Part 1910
49 CFR — Title 49 of the Code of Federal Regulations
(CFR), Chapter I
1 American National Standards Institute, 1430 Broadway, New York,
NY 10018
2 United States Government Printing Office, Washington, D.C. 20402
3.4 ICBO Codes
3
UBC CH 9 — Chapter 9 of the Uniform Building Code,
Requirements for Group H Occupancies
UFC ART 51 — Article 51 of the Uniform Fire Code,
Semiconductor Fabrication Facilities Using Hazardous
Production Materials
UFC STD 79-3 — Standard No. 79-3 of the Uniform
Fire Code
UFC ART 80 — Article 80 of the Uniform Fire Code,
Hazardous Materials
UFC ART 90 — Article 90 of the Uniform Fire Code,
Regulation of Facilities Where Materials Which Are or
May Become Toxic Gases Are Found
3.5 NFPA Standards
4
NFPA 70/ ART 500 — Article 500 of the National
Electrical Code, Hazardous (Classified) Locations
NFPA 497M — Classification of Gases, Vapors and
Dusts for Electrical Equipment in Hazardous
(Classified) Locations
NFPA 704 — Identification of the Fire Hazards of
Materials
3.6 ACGIH Publication
5
TLV
6
— American Conference of Governmental
Industrial Hygienists Threshold Limit Values and
Biological Exposure Indices
4 Terminology
4.1 closed secondary containment — Secondary
containment that has a sealed annulus. In closed
containment systems, the annular space either holds a
certain pressure of gas or a certain level of vacuum. In
closed containment, a change in the pressure or vacuum
would be indicative of a leak in either the primary or
secondary system.
3 International Conference of Building Officials, 5360 South
Workman Mill Road, Whittier, CA 90601
4 National Fire Protection Association, Batterymarch Park, Quincy,
MA 02269
5 American Conference of Governmental Industrial Hygienists, 6500
Glenway Avenue, Building D-7, Cincinnati, OH 45211
6 TLV is a registered trademark of ACGIH.