U.S. patent application number 10/150468 was filed with the patent office on 2002-10-31 for fluorine abatement using steam injection in oxidation treatment of semiconductor manufacturing effluent gases.
Invention is credited to Arno, Jose I., Vermeulen, Robert M..
Application Number | 20020159924 10/150468 |
Document ID | / |
Family ID | 23665001 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020159924 |
Kind Code |
A1 |
Arno, Jose I. ; et
al. |
October 31, 2002 |
Fluorine abatement using steam injection in oxidation treatment of
semiconductor manufacturing effluent gases
Abstract
An apparatus and process for abatement of halogen in a
halogen-containing effluent gas, such as is produced by a
semiconductor manufacturing plant utilizing perfluorocompounds in
the operation of the plant. Halogen-containing effluent gas is
contacted with water vapor in a thermal oxidation reactor to
convert halogen species to reaction products that are readily
removed from the effluent gas by subsequent scrubbing. A shrouding
gas may be employed to separate the halogen-containing effluent gas
from the water vapor at the inlet of the thermal oxidation reactor,
to thereby prevent premature reaction that would otherwise produce
particulates and reaction products that could clog the inlet of the
reactor.
Inventors: |
Arno, Jose I.; (Brookfield,
CT) ; Vermeulen, Robert M.; (Pleasant Hill,
CA) |
Correspondence
Address: |
ATMI, INC.
7 COMMERCE DRIVE
DANBURY
CT
06810
US
|
Family ID: |
23665001 |
Appl. No.: |
10/150468 |
Filed: |
May 17, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10150468 |
May 17, 2002 |
|
|
|
09420080 |
Oct 18, 1999 |
|
|
|
6423284 |
|
|
|
|
Current U.S.
Class: |
422/171 ;
422/173 |
Current CPC
Class: |
B01D 2258/0216 20130101;
B01D 2257/204 20130101; F23G 2209/142 20130101; B01D 53/68
20130101; B01D 2257/2066 20130101; Y02C 20/30 20130101; B01D 53/70
20130101 |
Class at
Publication: |
422/171 ;
422/173 |
International
Class: |
B01D 053/68 |
Claims
We claim:
1. An apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools, comprising: an
oxidizing unit having one or more inlet units at one end,
downstream from at least one semiconductor manufacturing process
tool, arranged to elevate the temperature of the effluent fluid
stream, effect oxidation of at least a portion of the oxidizable
components of the effluent fluid stream, and utilize water vapor to
effect conversion of at least a portion of the halogen-containing
components of the effluent fluid stream to a form that is more
treatable at the inlet end.
2. The apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools of claim 1, further
comprising a post-treatment unit downstream from the oxidizing
unit, arranged to remove acidic components from the effluent fluid
stream.
3. The apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools of claim 1, further
comprising a pre-treatment unit upstream from the oxidizing unit
and downstream from said one or more semiconductor manufacturing
process tools.
4. The apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools of claim 3, wherein
the pre-treatment unit is arranged to remove water-soluble
components and particulates.
5. The apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools of claim 1, wherein
the water vapor is used to effect the conversion of diatomic
halogens to their more readily treatable mineral acid form.
6. The apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools of claim 1 further
comprising a vaporizing unit arranged to provide water vapor to the
inlet end of the oxidizing unit.
7. The apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools of claim 1 wherein
the oxidizing unit is further arranged to utilize a purge gas to
preclude the conversion of at least a portion of the
halogen-containing components of the effluent fluid stream from
being effected at the one or more inlet units.
8. The apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools of claim 1 wherein
the one or more inlet units are arranged to introduce the effluent
fluid stream into the oxidizing unit, introduce the purge gas into
the oxidizing unit close to the one or more inlet units, and
introduce a reagent into the oxidizing unit at the inlet end of the
oxidizing unit.
9. The apparatus for treating the effluent fluid stream from one or
more semiconductor manufacturing process tools of claim 8, wherein
the reagent is water vapor.
10. The apparatus for treating the effluent fluid stream from one
or more semiconductor manufacturing process tools of claim 8
wherein the reagent is a hydrocarbon gas and the oxidizing unit is
further arranged to mix an oxygen containing gas with the
hydrocarbon gas at the inlet end of the oxidizing unit.
11. The apparatus for treating the effluent fluid stream from one
or more semiconductor manufacturing process tools of claim 1
wherein the effluent fluid stream is heated to within the
temperature range of about 650.degree. C. to about 950.degree.
C.
12. The apparatus for treating the effluent fluid stream from one
or more semiconductor manufacturing process tools of claim 1
wherein the semiconductor manufacturing process tools comprise high
density plasma chemical vapor deposition tools which use a remote
plasma source to effect disassociation of diatonic halogen gas from
halogen containing gases used during the cleaning process.
13. A thermal oxidation reactor for abatement of oxidizable halogen
components in an effluent gas, said thermal oxidation reactor
comprising: a housing defining a flow passage therein for flow of
effluent gas therethrough; an inlet coupled to the housing for
introduction of effluent gas to the central flow passage, said
inlet comprising (1) a shrouding gas flow passage arranged to flow
shrouding gas into the central flow passage cocurrently with the
effluent gas and surrounding the effluent gas, and (2) a reagent
gas flow passage arranged to flow a reagent gas into the central
flow passage cocurrently with the shrouding gas and surrounding the
shrouding gas, wherein the reagent gas is reactive with halogen
species in the effluent gas, with said central flow passage being
of sufficient length downstream of the inlet to permit the reagent
gas to mix and react with the halogen species of the effluent
gas.
14. The thermal oxidation reactor of claim 13, wherein the housing
comprises a liner susceptible to corrosion in contact with said
halogen species in the absence of said reagent gas to react with
said halogen species.
15. The thermal oxidation reactor of claim 13, wherein the inlet is
arranged to receive effluent gas from a semiconductor manufacturing
plant.
16. The thermal oxidation reactor of claim 13, wherein the
semiconductor manufacturing plant utilizes at least one
perfluorocompound as a reagent therein, and produces effluent gas
containing fluorine and/or fluorinated species.
17. The thermal oxidation reactor of claim 13, wherein the housing
includes a heating element arranged to maintain a temperature of
effluent gas flowed through the central flow passage in the range
of from about 650.degree. C. to about 950.degree. C.
18. The thermal oxidation reactor of claim 13, coupled in effluent
gas flow supply relationship to a scrubbing unit.
19. The thermal oxidation reactor of claim 18, wherein the
scrubbing unit comprises a water scrubbing unit.
20. The thermal oxidation reactor of claim 19, wherein the water
scrubbing unit comprises a packed bed column equipped with at least
one water spray nozzle.
21. The thermal oxidation reactor of claim 13, wherein the central
flow passage comprises an elongate cylindrical passage.
22. The thermal oxidation reactor of claim 13, coupled in effluent
gas supply relationship to a quench unit, with the quench unit
coupled in effluent gas supply relationship to a scrubbing
unit.
23. The thermal oxidation reactor of claim 22, wherein the
scrubbing unit comprises a water scrubbing unit.
Description
[0001] This is a divisional of U.S. application Ser. No.
09/420,080, filed on Oct. 18, 1999.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to an effluent
abatement system for the treatment of gas streams from processes
such as manufacturing of semiconductor materials, devices and
products. The invention relates more specifically to abatement of
halogens such as fluorine and fluorinated chemical species, by
reaction thereof with water vapor during thermal oxidation
treatment of a halogen-containing effluent gas.
[0004] 2. Description of the Related Art
[0005] Gaseous effluents from the manufacture of semiconductor
materials, devices, products and memory articles may contain a wide
variety of chemical species from the process facility. These
chemical species include inorganic and organic compounds, breakdown
products of photo-resist and other reagents, and a wide variety of
other gases that must be removed from the waste gas streams before
being vented from the process facility into the atmosphere.
[0006] The effluent gas in such instances may be subjected to any
of a wide variety of treatments to abate the various undesirable
components of the gas. Such effluent gas treatment may for example
include scrubbing of the effluent gas to remove acid gas components
and/or particulates from the gas stream. The gas may also be
thermally oxidized to remove organic components and other
oxidizable components, by mixing the effluent with an oxidant, such
as high purity oxygen, air or nitrous oxide, and flowing the
resulting gas mixture through a thermal oxidation reaction
chamber.
[0007] In such effluent treatment systems, halogens, e.g., fluorine
(F.sub.2) and fluorinated compounds are particularly problematic
among the various components requiring abatement. The electronics
industry uses perfluorinated compounds (PFCs) in wafer processing
tools to remove residue from deposition steps and to etch thin
films. PFCs are recognized to be strong contributors to global
warming and the electronics industry is working to reduce the
emissions of these gases.
[0008] The most commonly used PFCs include CF.sub.4,
C.sub.2F.sub.6, SF.sub.6, C.sub.3F.sub.8, and NF.sub.3. These PFCs
are dissociated in a plasma to generate highly reactive F.sub.2 and
fluorine radicals, which do the actual cleaning, and etching. The
products from these processing operations include mostly fluorine,
silicon tetrafluoride (SiF.sub.4), and to a lesser extent hydrogen
fluoride (HF) and carbonyl fluoride (COF.sub.2). The toxic nature
of these gases poses considerable health and environmental hazards,
in addition to being highly corrosive to exhaust systems.
[0009] Optimization of the operating conditions in the
semiconductor manufacturing process tool to increase the conversion
efficiencies (of PFCs to end products) has been the primary focus
in reducing PFC emissions. An example of this approach is the
Applied Materials HDP-CVD process. The improvements that have been
made in PFC conversions by process optimization has enabled the use
of shorter clean cycles to be achieved, and consequently higher
wafer throughputs to be obtained.
[0010] The current trend in the semiconductor manufacturing
industry to 300 mm wafer manufacturing will increase the amounts of
PFCs used in semiconductor manufacturing facilities. The increase
in usage of PFCs and their conversion to highly reactive products
have led to an increase in the corrosion rate of the abatement
equipment and associated exhaust ductwork. In particular the
corrosion attributable to fluorine has necessitated more frequent
replacement of equipment components upstream of the typically
employed wet scrubber unit in the effluent treatment system.
[0011] A number of reagents have been used for reaction with PFCs
to convert them to compounds that are less corrosive, can easily be
scrubbed from the exhaust stream, or pose less of a danger to
health and the environment. For example, hydrogen (H.sub.2) can be
introduced as a reagent to convert the fluorine to HF, which can
then be removed using a wet scrubber. Hydrogen, however, poses a
potential problem due to its explosive nature, and hydrogen has
been banned from some semiconductor processing operations because
of this danger.
[0012] As a result of the explosive hazard associated with H.sub.2,
other reagents can be dissociated to provide hydrogen to abate the
F.sub.2. Methane (CH.sub.4) can be employed to abate fluorine and
fluorinated species by combustion thereof using added air or oxygen
(O.sub.2). The water vapor and reactive hydrogen produced from this
combustion react with the F.sub.2 and fluorinated species to
convert them to HF and SiO.sub.2, which can then be readily removed
from the exhaust stream.
[0013] Methane is not as explosive as H.sub.2, but suffers from
other problems. The combustion of CH.sub.4 at high temperatures in
the presence of oxygen produces oxides of nitrogen (NO.sub.x).
Under combustion conditions where insufficient oxygen is present,
the CH.sub.4 can be converted to fluorine substituted methanes (of
the formula CH.sub.xF.sub.y, wherein x and y may range from 0 to
4). These fluoromethanes are of concern because of their strong
global warming potential.
[0014] Both anhydrous ammonia (NH.sub.3) and aqueous ammonia
(NH.sub.4OH) can also be used as reagents for F.sub.2 abatement.
Ammonia increases the cost of ownership for the effluent treatment
system in which it is used, and thus has a corresponding economic
disadvantage. Further, the presence of ammonia can be a factor in
the generation of oxygen difluoride if pH is not rigorously
controlled in the effluent treatment system.
[0015] It would therefore be an advance in the art to provide a
method of abatement of fluorine and other halogen species, which
overcomes the various above-described deficiencies of the prior
art.
SUMMARY OF THE INVENTION
[0016] The present invention relates to the abatement of halogen in
a halogen-containing effluent gas stream.
[0017] In one aspect, the invention relates to an apparatus for
treating the effluent fluid stream from one or more semiconductor
manufacturing process tools, comprising: an oxidizing unit having
one or more inlet units at one end, downstream from at least one
semiconductor manufacturing process tool, arranged to elevate the
temperature of the effluent fluid stream, effect oxidation of at
least a portion of the oxidizable components of the effluent fluid
stream, and utilize water vapor to effect conversion of at least a
portion of the halogen-containing components of the effluent fluid
stream at the inlet end.
[0018] Such apparatus may in one embodiment further include a
post-treatment unit, downstream from the oxidizing unit, arranged
to remove acidic components from the effluent fluid stream.
[0019] Another aspect of the invention relates to a thermal
oxidation reactor for abatement of oxidizable halogen components in
an effluent gas, such thermal oxidation reactor comprising: a
housing defining a flow passage therein for flow of effluent gas
therethrough; an inlet coupled to the housing for introduction of
effluent gas to the central flow passage, such inlet comprising (1)
a shrouding gas flow passage arranged to flow shrouding gas into
the central flow passage cocurrently with the effluent gas and
surrounding the effluent gas, and (2) a reagent gas flow passage
arranged to flow a reagent gas into the central flow passage
cocurrently with the shrouding gas and surrounding the shrouding
gas, wherein the reagent gas is reactive with halogen species in
the effluent gas, with the central flow passage being of sufficient
length downstream of the inlet to permit the reagent gas to mix and
react with the halogen species of the effluent gas.
[0020] In one method aspect, the invention relates to a method for
treating the effluent fluid stream from one or more semiconductor
manufacturing process tools using a system that includes an
oxidizing unit having one or more inlet units at one end,
comprising the steps of:
[0021] providing water vapor to the inlet end of the oxidizing
unit;
[0022] effecting, at the inlet end of the oxidizing unit, the
conversion of at least a portion of the halogen-containing
components of the effluent fluid stream to a form that is more
treatable using such water vapor; and
[0023] effecting, in the oxidizing unit, the oxidation of at least
a portion of the oxidizable components of the effluent fluid
stream.
[0024] The above-described method may further comprise in a
particular embodiment the additional step of removing acidic
components from the effluent fluid stream.
[0025] Another aspect of the invention relates to a method of
thermally oxidizing a halogen-containing effluent gas in a thermal
oxidation reactor including a gas flow path bounded by a liner
susceptible to corrosion in exposure to halogen species in the
halogen-containing effluent gas, such method comprising introducing
the halogen-containing effluent gas into the thermal oxidation
reactor and flowing water vapor between the introduced
halogen-containing effluent gas and the liner to thereby protect
the liner by reaction of the water vapor with the halogen species
in the halogen-containing effluent gas.
[0026] Other aspects, features and embodiments will be fully
apparent from the ensuing disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a schematic representation, in partial section, of
an effluent abatement system receiving a halogen-containing
effluent gas from a semiconductor manufacturing plant, according to
one embodiment of the invention.
[0028] FIG. 2 is a schematic representation of gas flows in the
inlet portion of a thermal oxidizer apparatus, according to one
aspect of the invention.
[0029] FIG. 3 is a cross-sectional elevation view of an inlet of a
thermal oxidizer unit, according to one embodiment of the
invention.
[0030] FIG. 4 is a cross-sectional elevation view of an inlet of a
thermal oxidizer unit, according to another embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS
THEREOF
[0031] The disclosures of U.S. patent application Ser. No.
08775,838 filed Dec. 31, 1996 in the names of Mark Holst, et al.
for "Effluent Gas Stream Treatment System Having Utility for
Oxidation Treatment of Semiconductor Manufacturing Effluent Gases,"
issued Sep. 21, 1999 as U.S. Pat. No. 5,955,037 and the disclosure
of U.S. patent application Ser No. 09/228,706 filed Jan. 12, 1999
in the names of Robert R. Moore, et al. for "Apparatus and Method
for Controlled Decomposition of Gaseous Pollutants" are hereby
incorporated herein by reference in their respective
entireties.
[0032] The present invention utilizes the introduction of water
vapor as a reagent in the thermal oxidation abatement treatment of
halogen-containing gases, e.g., fluorine-containing gases. The use
of water vapor for such oxidation treatment of the
halogen-containing gas offers the advantage of providing a source
of hydrogen to react with the halogen, in addition to having a
lower impact on cost of ownership than other reagents that might be
used. Introduction of the water vapor at the beginning of the
thermal section of the effluent abatement system allows a maximum
reaction time (relative to any downstream addition of water vapor)
and by early reaction with the halogen components of the effluent
gas serves to protect the sections of the abatement system that are
most vulnerable to corrosion.
[0033] The thermal oxidation unit employed in the practice of the
invention may be utilized in conjunction with an upstream
pretreatment unit (with the pre-treatment unit being downstream
from one or more semiconductor process tools). The pre-treatment
unit may be arranged to remove water-soluble components and
particulates from the effluent gas, prior to treatment of the
effluent gas in the thermal oxidation unit, wherein the
halogen-containing components of the effluent stream are converted
to a form that is more treatment, e.g., by post-oxidation treatment
scrubbing, optionally with quenching of the effluent gas discharged
from the thermal oxidation unit.
[0034] In the thermal oxidation unit, the introduced water vapor
effects the conversion of diatomic halogens (e.g., F.sub.2,
I.sub.2, Cl.sub.2, Br.sub.2) to their more readily treatable
mineral acid form. The water vapor may be utilized to provide a
hydrogen source to effect such conversion, heat to keep the
surfaces in the oxidation unit above dewpoint and overcome the
latent heat of vaporization of the water. Oxidation may be added to
the effluent in or upstream of the oxidation unit, or the effluent
may already contain an oxidizer medium deriving from its upstream
source (semiconductor tool(s)).
[0035] Referring now to the drawings, FIG. 1 is a schematic
representation, in partial section, of an effluent abatement system
10 receiving a halogen-containing effluent gas from a semiconductor
manufacturing plant 74, according to one embodiment of the
invention.
[0036] The semiconductor manufacturing plant 74 may comprise
semiconductor manufacturing process tools of any suitable type. For
example, the semiconductor manufacturing process tools may comprise
high density plasma chemical vapor deposition tools that use a
remote plasma source to effect disassociation of fluorine from
fluorine containing gases used during the cleaning process.
[0037] The effluent abatement system 10 includes main process
section A-D, comprising thermal reaction section A, primary
cooling/scrubbing section B, lower secondary cooling/scrubbing
section C and upper secondary cooling/demister section D.
[0038] In the thermal reaction section A, the effluent abatement
system 10 includes a thermal oxidation reactor 12, to which is
joined an inlet assembly 14 for delivery of process gases and
ancillary fluids to the reactor.
[0039] The thermal oxidation reactor 12 includes an exterior wall
16 and an interior wall 20 enclosing an annular heating element 18.
The interior wall 20 encloses a central flow passage 22 of the
reactor. The annular heating element may for example be
electrically heated to provide a hot surface at the interior wall
20, for elevated temperature treatment of the effluent being
treated. The inner wall 20, or "liner," may be formed of any
suitable material, such as Inconel.RTM. metal alloy.
[0040] The thermal oxidation reactor 12, although illustratively
shown as an electrically heated unit, may alternatively be of any
suitable type. Examples of alternative types include flame-based
thermal oxidizers (e.g., using oxygen as an oxidizer and hydrogen
or methane as the fuel), catalytic oxidizers, transpirative
oxidizers, etc. The thermal oxidizer may be heated in any suitable
manner, such as by electrical resistance heating, infrared
radiation, microwave radiation, convective heat transfer or solid
conduction.
[0041] The thermal oxidization reactor 12 may as shown be equipped
with a control thermocouple 24. The thermocouple is used to monitor
the temperature of the heating element 18. The thermocouple may be
arranged in suitable signal transmission relationship to a thermal
energy controller (not shown). Such thermal energy controller may
in turn be arranged to responsively modulate the electrical heating
energy to the annular heating element 18, and thereby achieve a
desired temperature of the hot wall surface of interior wall 20. In
such manner, the wall surface can be maintained at a desired
temperature level appropriate for the thermal oxidation treatment
of the effluent flowed through the thermal oxidizer unit (in the
direction indicated by arrow F in FIG 1.)
[0042] The thermal oxidation reactor 12 in the embodiment shown is
adapted to receive clean dry air (CDA) from CDA supply line 26. The
CDA supply line 26 may be joined in supply relationship to a
suitable source of clean dry air (e.g., CDA source 72). The
thus-introduced air flows into the annular space between outer wall
16 and inner wall 20 of the thermal oxidizer unit, and is heated to
suitable temperature in contact with the annular heating element
18. Resultant heated air then may flow through orifices or pores in
the inner wall 20 into the central flow passage 22 of the reactor.
In such manner, the oxidant may be added to mix with the effluent
gas an form an oxidizable effluent gas mixture for thermal
oxidation in the reactor. Alternatively, the oxidant may be added
at the inlet, as another introduced fluid stream, to support the
oxidation reactions in the thermal oxidation reactor.
[0043] At its lower end, the thermal oxidizer unit 12 is joined to
a quench inlet section 28 of quench unit 32. In the quench inlet
section, an array of water spray nozzles 30 is provided, supplied
with water by an associated water feed conduit, as shown. The water
spray nozzles serve to provide initial quench cooling to the hot
effluent gas stream as the stream is discharged from the thermal
oxidizer unit into the quench unit.
[0044] The quench unit is arranged with the quench inlet section 28
joined to a transverse section 34 of the quench unit.
[0045] The transverse section 34 in turn is joined to the sump
section 36 of the quench unit. The sump section 36 at its lower end
is coupled to a slope drain/vapor barrier 38. A conductivity liquid
level sensor/chamber purge assembly is joined to the sump section
36, and is coupled to CDA branch line 42 which provides clean dry
air to the assembly.
[0046] At its upper end, the sump section 36 of the quench unit 32
is joined to the lower end of the scrubber demister column 44. The
scrubber demister column is filled, in the lower secondary
cooling/scrubbing section thereof, with a secondary scrubbing
packing 46, and the upper portion of such section of the column is
equipped with a water spray nozzle 48 for effecting scrubbing of
the upflowing effluent gas therein, by countercurrently flowing
water downwardly over the packing 46. The water spray nozzle 48 is
supplied with water by water feed line 50.
[0047] The upper portion of the lower section of the scrubber
demister column is equipped with a vapor relief port 52 to which is
coupled a vapor relief line 54, for venting overpressure in the
column. An exhaust temperature sensor 56 is mounted on the upper
portion of the lower section of the scrubber demister column, to
provide temperature monitoring capability for the column.
[0048] The upper section of the scrubber demister column is
likewise filled with a secondary scrubbing packing 58 and is
equipped with a water spray nozzle 60 coupled to water feed line
50. The water feed line 50 has an air operated valve 101 therein.
The valve is normally in a closed condition, and may be actuated as
necessary to provide additional scrubbing capability for treatment
of a specific effluent gas stream.
[0049] The upper section of the scrubber demister column is coupled
to an exhaust temperature sensor 62, for monitoring the temperature
of the effluent gas stream. A magnehelic pressure display 64 is
also joined to the upper section of the scrubber demister column. A
clean dry air line 70 is joined to clean dry air source 72. The CDA
line 70 supplies CDA to the column, e.g., for dilution of the
effluent stream being discharged from the upper end of the column
in the direction indicated by the arrow R. The CDA line 70 has a
restricted flow orifice 68 therein and a flow control valve
upstream of the orifice, for selectively restricting flow of CDA to
the upper end of the column.
[0050] The inlet assembly 14 for delivery of process gases and
ancillary fluids to the thermal oxidation reactor 12 is arranged as
shown, with process gas inlet conduits 88 and 90 receiving process
exhaust gas in lines 84 and 86 from the gas flow router/manifold
82, which in turn receives gas streams 76,78 and 80 from the
semiconductor manufacturing plant 74.
[0051] The semiconductor manufacturing plant 74 may be arranged to
carry out any suitable operations for the production of
semiconductor materials, devices and products.
[0052] Examples of specific operations of such semiconductor
manufacturing plant 74 may include one or more process steps, such
as for example:
[0053] (a) ion implantation;
[0054] (b) epitaxial growth;
[0055] (c) plasma etching;
[0056] (d) reactive ion etching;
[0057] (e) metallization;
[0058] (f) physical vapor deposition;
[0059] (g) chemical vapor deposition;
[0060] (h) photolithography;
[0061] (i) cleaning; and
[0062] (j) doping.
[0063] Specific manufacturing operations may for example comprise
photolithography steps in the manufacture of VLSI and ULSI
circuits, epitaxial deposition of film materials such as silicon
from dispensed Si source gases, ion implantation and doping in the
fabrication of CMOS, NMOS, BiCMOS and other structures, and
manufacture of devices such as DRAMs, SRAMs, FeRAMs, etc.
[0064] The semiconductor manufacturing plant 74 may be employed to
fabricate electronic device structures such as for example:
[0065] (a) transistors;
[0066] (b) capacitors;
[0067] (c) resistors;
[0068] (d) memory cells;
[0069] (e) dielectric material;
[0070] (f) buried doped substrate regions;
[0071] (g) metallization layers;
[0072] (h) channel stop layers;
[0073] (i) source layers;
[0074] (j) gate layers;
[0075] (k) drain layers;
[0076] (l) oxide layers;
[0077] (m) field emitter elements;
[0078] (n) passivation layers;
[0079] (o) interconnects;
[0080] (p) polycides;
[0081] (q) electrodes;
[0082] (r) trench structures;
[0083] (s) ion implanted material layers;
[0084] (t) via plugs;
[0085] (u) precursor structures for the foregoing (a)-(t)
electronic device structures; and
[0086] (v) device assemblies comprising more than one of the
foregoing (a)-(t) electronic device structures.
[0087] With regard to products, the semiconductor manufacturing
plant 74 may be constructed and arranged to produce electronic
device structures. The products may for example comprise memory
chip devices, such as:
[0088] (i) ROM chips;
[0089] (ii) RAM chips;
[0090] (iii) SRAM chips;
[0091] (iv) DRAM chips;
[0092] (v) PROM chips;
[0093] (vi) EPROM chips;
[0094] (vii) EEPROM chips; and
[0095] (viii) flash memory chips.
[0096] In the FIG. 1 effluent abatement system, the process gas
inlet conduits 88 and 90 flow the influent process exhaust gas into
the thermal oxidation reactor 12. These process gas inlet conduits
are constructed with ancillary fluid addition lines 92 and 94, for
addition of ancillary process fluids to the main effluent stream
being flowed through the process gas inlet conduits 88 and 90.
[0097] The inlet assembly 14 also includes a shroud gas feed line
96 and a hydrogen source feed line 98. The hydrogen source feed
line 98 is joined to a hydrogen source gas supply 100. The shroud
gas may be a purge gas for the thermal oxidation reactor, or the
inlet or associated piping and channels of the effluent abatement
system. Illustrative shroud or purge gas species include nitrogen,
helium, argon, etc.
[0098] In accordance with a preferred aspect of the present
invention, water vapor (steam) is introduced as a hydrogen source
gas to the thermal oxidation reactor 12. The water vapor is
utilized at elevated temperature appropriate to the thermal
oxidation process being carried out in the thermal oxidation
reactor and the halogen components being abated in the effluent
gas. The hydrogen source gas supply 100 therefore may comprise a
vaporization unit that is supplied with water from a suitable feed
source, such as a water line in the semiconductor manufacturing
facility, a municipal or industrial water supply, or the like. The
hydrogen source gas supply 100 may alternatively comprise a steam
line in the semiconductor manufacturing facility or other source of
water vapor. As a still further alternative, the hydrogen source
gas supply 100 may comprise a chemical reaction vessel for reacting
reagent materials to form water vapor. For example, a hydrocarbon
reagent, such as methane, propane, natural gas, etc., may be
introduced to the chemical reaction vessel for mixing and reaction
with an independently introduced oxidant, e.g., an
oxygen-containing gas such as air, oxygen, oxygen-enriched air,
ozone, or the like, to produce water vapor as a reaction
product.
[0099] Water vapor is employed in accordance with the present
invention to provide a source of hydrogen in the thermal oxidation
reactor, for reaction with the halogen constituents of the effluent
gas. Although the invention is described hereinafter primarily in
reference to fluorine and fluorinated species being the halogen
components of interest, it will be appreciated that the invention
is not thus limited, and extends in utility to the abatement of
other halogens, e.g., bromine, iodine and chlorine, and to
corresponding other halogen-containing compounds, complexes and
radicals.
[0100] The invention therefore provides water vapor as a source of
hydrogen gas for reaction with the halogen species, e.g.,
converting fluorine species to forms that are amenable to removal
by wet scrubbing. For example, fluorine gas is readily converted by
reaction with steam, to yield hydrogen fluoride, which is easily
removed from the effluent gas in the scrubbing step. The scrubbing
step also removes various other acid gas components of the
effluent, to produce a halogen-reduced/acid gas-reduced
effluent.
[0101] Fluorine in the effluent gas flowed into an effluent
abatement system of the type shown in FIG. 1, with steam injection
at the inlet of the reactor, will be abated in the upper section of
the reactor.
[0102] In conventional systems comprising thermal oxidation
treatment of the effluent followed by water scrubbing, but lacking
the steam addition (or other hydrogen source injection/addition)
capability of the system of the present invention, fluorine will be
abated in the primary and secondary stages of the cooling and
scrubbing sections, however, prior to being converted to HF, the
reactive fluorine can corrode components in the thermal section of
the thermal oxidation reactor. In some cases this has led to
failure of the thermal section liners and primary cooling sections
in less than two months. The most common failure mode in the liners
is erosion of the center of the liner. For the primary cooling
sections the failures are typically due to attack on the hot areas
not contacted by the water quench.
[0103] The present invention overcomes these deficiencies.
Introduction of steam as a hydrogen source at the inlet, as for
example in line 98 in the system of FIG. 1, allows the reactive
F.sub.2 and fluorinated species to be reacted before they have a
chance to attack the thermal section.
[0104] In preferred practice of the present invention, water vapor
is injected between the stream of process gas and the liner of the
thermal oxidation reactor, thereby protecting the liner from
attack.
[0105] Referring now to FIG. 2, there is shown a schematic
representation of gas flows in the inlet portion of a thermal
oxidizer apparatus (such as that shown in FIG. 1), according to one
aspect of the invention.
[0106] FIG. 2 shows the liner 20 of the thermal oxidation reactor
as bounding the central flow passage of the thermal oxidation
reactor. A fluorine-containing effluent gas stream, indicated by
the arrow G, is flowed from the inlet into and through the central
flow passage of the thermal oxidation reactor.
[0107] Concurrent with the flow of the effluent gas stream through
the inlet into the central passage of the thermal oxidation
reactor, a shrouding gas, indicated by arrows H, is introduced, to
surround the effluent gas stream in downflow through the central
flow passage of the thermal oxidation reactor. The shrouding gas
may for example be nitrogen, or other inert gas.
[0108] Concurrently, the inlet introduces water vapor, indicated by
arrows I, for flow downwardly in the thermal oxidation reactor.
[0109] By such arrangement, the shrouding gas separates the
effluent gas stream from the water vapor and prevents premature
reactions that could otherwise generate solids and clog the gas
feed tubes of the inlet. The water vapor may optionally be
introduced with air or nitrogen mixture.
[0110] In the thermal section of the reactor, the hydrogen deriving
from the steam will react with the fluorine or other halogen
components of the effluent gas. The hot reaction products will be
quenched in the primary section B (see FIG. 1) and will travel to
the secondary sections C and D (see also FIG. 1) where they will be
scrubbed.
[0111] In a variant of the foregoing water vapor introduction
arrangement described above in connection with FIG. 2, the arrows
I, instead of representing water vapor, may represent an
alternative hydrogen source material, such as methane.
Concurrently, oxygen, air or other oxygen-containing gas, indicated
by arrow J, may be introduced to the thermal oxidation reactor for
reaction with the methane or other hydrogen source material, to
produce water vapor as a reaction product, for reaction with
fluorine and fluorinated species. The nitrogen or other inert gas
indicated by arrow H will serve the same function in this variant
arrangement, of separating the effluent from the water vapor (and
methane combustion products).
[0112] FIG. 3 is a cross-sectional elevation view of an inlet of a
thermal oxidizer unit of the type shown in FIG. 1, according to one
embodiment of the invention. For ease of description, the same
reference numerals are used in FIG. 3 as employed for the
corresponding elements in FIG. 1.
[0113] As shown in FIG. 3, the inlet structure 14 includes a
process gas inlet conduit 90 for introducing effluent gas from a
process facility, such as a semiconductor manufacturing tool, to a
thermal oxidation reactor 12.
[0114] The process gas inlet conduit 90 features an inlet pressure
monitoring port 112 for coupling with a suitable pressure
monitoring device to sense the pressure of the process gas. The
process gas inlet conduit 90 is provided with fluid addition lines
92 and 94, for addition of oxygen, air, nitrogen, and/or any other
gas species, to assist the thermal oxidation reaction in the
reactor 12. For example, the fluid addition lines may be employed
to add a co-reactant species for specific components of the
effluent gas being treated.
[0115] The process gas inlet conduit 90 terminates in a lower
tubular wall 122 enclosing a cylindrical flow passage 120, within
an outer tubular wall 124. The outer tubular wall 124 is in spaced
relationship to tubular wall 122, defining an annular space 126
therebetween.
[0116] Communicating with annular space 126 is a shroud gas feed
line 96, to which shroud gas such as nitrogen is introduced, for
downward flow around the discharged effluent gas in the central
flow passage defined by outer tubular wall 124. The outer tubular
wall 124 thus defines an effluent flow passage and is open-ended at
its lower end.
[0117] Water vapor is introduced in hydrogen source gas feed line
98 and flows downwardly, exiting the inlet structure at its lower
end as indicated by arrows K. Subsequently, in flow below the inlet
12, in the thermal oxidation reactor, the water vapor mixes with
the effluent gas and fluorine and fluorinated species in the
effluent gas are reacted with hydrogen deriving from the injected
water vapor. Hydrogen fluoride and other reaction products thereby
are formed, which are readily removable in the subsequent scrubbing
operation of the effluent treatment system.
[0118] Instead of water vapor, methane or other hydrogen source gas
may be introduced in line 98 to the inlet. For example, if methane
is introduced in line 98, then oxygen, air, or other
oxygen-containing gas may be concurrently introduced in the same
line, or in a different line of the inlet, e.g., in line 92 or line
94. A steam generator may additionally be coupled with hydrogen
source gas feed line 98, to provide hydrogen for reaction with the
halogen in the effluent gas.
[0119] FIG. 4 is a cross-sectional elevation view of an inlet 140
of a thermal oxidizer unit, according to another embodiment of the
invention. The inlet comprises an inlet body 141 constructed with a
first tubular feed conduit 142 and a second tubular feed conduit
144, defining enclosed interior passages 146 and 148, respectively.
Effluent gas, indicated by arrows L, is introduced to the first
tubular feed conduit 142 and second tubular feed conduit 144, for
flow through the inlet into the thermal oxidation reactor.
[0120] The inlet body 141 also comprises nitrogen feed passages 150
and 152, through which nitrogen gas, indicated by arrows M, is
flowed. These nitrogen feed passages communicate with central
nitrogen feed passage 154. As shown, at the bottom of the inlet
body, the nitrogen gas (arrows M) flows downwardly as a shrouding
gas for the effluent gas stream (arrows L).
[0121] Concurrently, a hydrogen source gas is introduced to the
inlet body by hydrogen source gas passages 156 and 158, for entry
into the annular hydrogen source gas reservoir 160. The hydrogen
source gas is flowed from the reservoir through the hydrogen source
gas outlet slots 162 and 164, and flows downwardly (arrows N)
around the effluent gas stream (arrows L), so that the effluent gas
stream is shrouded by the shrouding gas stream (arrows M), to
thereby prevent premature reaction between the effluent gas and the
hydrogen source gas.
[0122] Subsequently, as the gas streams (arrows L, M and N) pass
downwardly, the respective streams mix and the hydrogen source gas
reacts with the fluorine and fluorinated species in the effluent
gas stream, to abate the fluorine content thereof.
[0123] In the broad practice of the invention, the relative flow
rates of the hydrogen source gas and the effluent gas stream may be
suitably selected so as to minimize the incidence of corrosion of
the liner in the thermal oxidation reactor and to effect the
desired reaction and removal of the halogen content of the effluent
gas stream being treated.
[0124] The same is true of the shrouding gas used to protect the
effluent gas from premature reaction with the hydrogen source
gas.
[0125] The relative rates of flow of all gas streams in a given
treatment application may be readily determined without undue
experimentation, by the simple expedient of independently varying
the flow rate of each stream in sequence and determining the
corresponding destruction removal efficiency (DRE) of the halogen
component(s) of interest in the treated effluent gas.
[0126] Suitable temperature and pressure levels for the effluent
abatement process of the invention can be similarly determined, to
achieve a desired level of abatement of the halogen component in
the effluent gas.
[0127] Preferred temperatures for the use of water vapor or
CH.sub.4 as a hydrogen source reagent are between 650.degree. C.
and 950.degree. C., with the lower temperatures decreasing the
corrosion rate and F.sub.2 attack on the liner.
[0128] The invention will therefore be appreciated as providing a
simple and effective technique for the abatement of fluorine and
fluorinated species, as well as of other halogen species, from
effluent gases generated in industrial processes, such as
manufacturing of semiconductor materials, devices and products.
[0129] The features and advantages of the invention will be more
fully apparent from the following non-limiting examples.
EXAMPLE 1
[0130] F.sub.2 abatement from an effluent derived from a
semiconductor manufacturing plant was evaluated in a Delatech
CDO.TM. thermal oxidation unit (Ecosys Corporation, San Jose,
Calif.), using NH.sub.4OH as the abatement reagent.
[0131] F.sub.2 abatement from a corresponding effluent was
evaluated using water flushed through the NH.sub.4OH injection
lines of the thermal oxidation reactor.
[0132] The Destruction Removal Efficiency (DRE) for F.sub.2 when
water was flushed through the NH.sub.4OH injection lines was
between DRE value for NH.sub.4OH reagent and the DRE value when no
reagent was used.
[0133] The improved DRE for water flushing relative to performance
with no F.sub.2 abatement reagent indicated that some of the
F.sub.2 was being abated by the water in the heated section of the
CDO.TM. thermal oxidation reactor. Table 1 below shows the fluorine
abatement with injection of water into the inlet section of the
thermal oxidation reactor.
1TABLE 1 Fluorine abatement with injection of water into thermal
oxidation reactor inlet section. NH.sub.3 aq. H.sub.2O NH.sub.3 in
F.sub.2 in Total Flow Water F.sub.2 in F.sub.2 out F.sub.2 DRE
g/min g/min slpm slpm slpm pH (ppm) (ppm) % 4.0 2.9 1.6 2.0 182 3.4
11,013 1 99.99 0.0 4.0 0.0 2.0 180 3.3 11,111 3 99.97 0.0 4.0 0.0
2.0 172 3.2 11,628 10 99.91 0.0 0.0 0.0 2.0 172 3.2 11,628 40
99.66
EXAMPLE 2
[0134] Long term testing with NH.sub.4OH as a F.sub.2 abatement
reagent revealed a problem with corrosion on the bottom of the
inlet section of the thermal oxidation reactor. This corrosion was
traced to cooling by the NH.sub.4OH being vaporized in the inlet
section. To prevent this cooling due to the change of state from
liquid to vapor, a heater was installed before the inlet section to
vaporize the incoming NH.sub.4OH prior to injection. This heater
consisted of a tubular housing with a heating element inside the
housing. The NH.sub.4OH was metered, mixed with air and entered the
side of the housing where it was vaporized by the heater element.
The NH.sub.4OH vapor mixed with air exited the housing and flowed
to the inlet assembly. This modification resolved the corrosion
problem. NH.sub.4OH may be employed as an adjunctive fluorine
abatement agent in the broad practice of the present invention.
EXAMPLE 3
[0135] A fluorine abatement effluent treatment system of the type
shown in FIG. 1 and equipped with an inlet of the type shown in
FIG. 3 is operated, to effect treatment of an effluent gas stream
from a semiconductor manufacturing facility. Water vapor is used as
the fluorine abatement agent. The process gas flows down the center
tube, with N.sub.2 flowing into the surrounding tube and out the
annulus formed by the two concentric tubes. This N.sub.2 flowing
out the annulus separates the process gases from the water vapor
and prevents premature reactions that could generate solids and
clog the inlet tubes. The water is vaporized into steam using the
same heater used for the NH.sub.4OH testing in Example 2. The steam
and air or N.sub.2 mixture is introduced into the hydrogen source
gas feed tube to flow around the tube carrying the effluent gas and
mix with the process gases in the thermal section of the CDO.TM.
thermal oxidation reactor. The hot reaction products are quenched
in the primary section and travel through the secondary section
where they are scrubbed.
EXAMPLE 4
[0136] Another test is conducted using the combustion of CH.sub.4
in air or O.sub.2 to generate water vapor to react with the F.sub.2
and fluorinated species. In this case the same inlet configuration
as shown in FIG. 3 is used. The process gases flow through the same
center tube as in the water vapor injection in Example 3. CH.sub.4
is injected. The flow of N.sub.2 separates the process gases from
the water vapor and CH.sub.4 combustion products. O.sub.2 or clean
dry air (CDA) is added to support the combustion of the
CH.sub.4.
[0137] While the invention has been described with reference to
illustrative embodiments, it will be recognized that other
variations, modification and other embodiments are contemplated, as
being within the spirit and scope of the invention, and therefore
the invention is to be correspondingly broadly construed with
respect to such variations, modifications and other embodiments, as
being within the spirit and scope of the invention as claimed.
* * * * *