U.S. patent application number 12/069514 was filed with the patent office on 2008-10-23 for air handling and chemical filtration system and method.
This patent application is currently assigned to Entegris, Inc.. Invention is credited to William M. Goodwin, Anatoly Grayfer, Oleg P. Kishkovich.
Application Number | 20080257159 12/069514 |
Document ID | / |
Family ID | 34526228 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080257159 |
Kind Code |
A1 |
Goodwin; William M. ; et
al. |
October 23, 2008 |
Air handling and chemical filtration system and method
Abstract
The present invention relates to systems and methods for
controlling humidity and temperature in gases or air streams used
in semiconductor processing systems. These systems and methods can
be used in combination with systems and methods for contaminant
detection and removal.
Inventors: |
Goodwin; William M.;
(Medway, MA) ; Kishkovich; Oleg P.; (Greenville,
RI) ; Grayfer; Anatoly; (Newton, MA) |
Correspondence
Address: |
HAMILTON, BROOK, SMITH & REYNOLDS, P.C.
530 VIRGINIA ROAD, P.O. BOX 9133
CONCORD
MA
01742-9133
US
|
Assignee: |
Entegris, Inc.
Billerica
MA
|
Family ID: |
34526228 |
Appl. No.: |
12/069514 |
Filed: |
February 11, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10888573 |
Jul 9, 2004 |
7329308 |
|
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12069514 |
|
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60485768 |
Jul 9, 2003 |
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Current U.S.
Class: |
96/136 ; 96/251;
96/290; 96/300 |
Current CPC
Class: |
F24F 8/15 20210101; Y10S
438/909 20130101; B01D 53/18 20130101; F24F 3/16 20130101; B01D
2258/0216 20130101 |
Class at
Publication: |
96/136 ; 96/290;
96/300; 96/251 |
International
Class: |
B01D 47/14 20060101
B01D047/14 |
Claims
1. A filtering apparatus for a semiconductor processing tool,
comprising: an inlet in a first absorption section for receiving a
scrubbing liquid; an absorption structure positioned in the first
absorption section such that scrubbing liquid wets a surface of the
absorption structure and flows down the absorption structure; an
inlet in the first absorption section for receiving an output gas
stream from a semiconductor processing tool, the output gas stream
having one or more contaminants; and the first absorption section
configured such that the output gas stream contacts scrubbing
liquid on the surface of the absorption structure and the
concentration of the one or more contaminants in the gas stream is
reduced by sorption in the scrubbing liquid.
2. The apparatus of claim 1, wherein the semiconductor processing
tool comprises a photolithography tool or photolithography tool
cluster.
3. The apparatus of claim 1, wherein the scrubbing liquid comprises
water.
4. The apparatus of claim 1, wherein the scrubbing liquid comprises
de-ionized water having a resistivity in the range from about
100,000 .OMEGA.cm to about 18 M.OMEGA. cm.
5. The apparatus of claim 1, wherein the scrubbing liquid comprises
a non-polar solvent.
6. The apparatus of claim 1, wherein the scrubbing liquid comprises
one or more additives that facilitate reducing the concentration of
one or more contaminants in the output gas stream.
7. The apparatus of claim 1, wherein the inlet for receiving the
scrubbing liquid comprises a liquid atomizer.
8. The apparatus of claim 1, wherein the absorption structure
comprises a loose packed-bed.
9. The apparatus of claim 1, wherein the output gas stream
comprises air.
10. The apparatus of claim 1, wherein the inlet for receiving the
scrubbing liquid and the inlet for receiving the output gas stream
of the first absorption section are configured such that the
filtering apparatus can be operated as a co-current system.
11. The apparatus of claim 1, wherein the inlet for receiving the
scrubbing liquid and the inlet for receiving the output gas stream
of the first absorption section are configured such that the
filtering apparatus can be operated as a counter-current
system.
12. The apparatus of claim 1 further comprising an outlet in the
first absorption section for providing an outgoing gas stream an
inlet in a second absorption section for receiving a scrubbing
liquid; an absorption structure positioned in the second absorption
section such that scrubbing liquid wets a surface of the absorption
structure and flows down the absorption structure; an inlet in the
second absorption section for receiving the outgoing gas stream
from the first absorption section, the outgoing gas stream having
one or more contaminants; and the second absorption section
configured such that the outgoing gas stream contacts scrubbing
liquid on the surface of the absorption structure in the second
absorption section and the concentration of the one or more
contaminants in the gas stream is reduced by sorption in the
scrubbing liquid.
13. The apparatus of claim 12, wherein one of the first absorption
section and second absorption section is configured to be operated
as a counter-current system and the other of the first absorption
section and second absorption section is configured to be operated
as a co-current system.
14. The apparatus of claim 1, wherein the first absorption section
comprises: an outlet in the first absorption section for removing
the scrubbing liquid; and an outlet in the first absorption section
for providing a return gas stream to the semiconductor processing
tool, the return gas stream having a reduced concentration of the
one or more contaminants in the output gas stream.
15. The apparatus of claim 14, wherein the outlet for providing a
return gas stream comprises a collection device for the removing
droplets of scrubbing liquid from the return gas stream.
16. The apparatus of claim 12, wherein the second absorption
section comprises: an outlet in the second absorption section for
removing the scrubbing liquid; and an outlet in the second
absorption section for providing a return gas stream to the
semiconductor processing tool, the return gas stream having a
reduced concentration of the one or more contaminants in the output
gas stream.
17. The apparatus of claim 16, wherein the outlet for providing a
return gas stream comprises a collection device for the removing
droplets of scrubbing liquid from the return gas stream.
18. The apparatus of claim 15, wherein the collection device
controls the relative humidity of the return gas stream.
19. The apparatus of claim 14, wherein the outlet for removing the
scrubbing liquid comprises a recirculation unit for the scrubbing
liquid, the recirculation unit providing a cleaned scrubbing
liquid.
20. The apparatus of claim 14, further comprising a temperature
control unit positioned in the flow path of the cleaned scrubbing
liquid and positioned to provide a temperature controlled scrubbing
liquid to the inlet in the absorption section for receiving
scrubbing liquid.
21. The apparatus of claim 1, further comprising a heat exchanger
positioned to exchange heat between the output gas stream and
return gas stream.
22. The apparatus of claim 1, further comprising a gas temperature
control unit positioned in the return gas stream, wherein the gas
temperature control unit controls the temperature of the return gas
stream.
23. The apparatus of claim 20, wherein the gas temperature control
unit together with the temperature control unit control the
temperature and humidity of the return gas stream.
24. The apparatus of claim 14, wherein the collection device
together with the temperature control unit control the relative
humidity of the return gas stream.
25. The apparatus of claim 1, further comprising a scrubbing liquid
supply.
26. The apparatus of claim 1, further comprising an additive
source.
27. The apparatus of claim 1, further comprising one or more
adsorptive filters placed in the flow path of at least one of the
output gas stream from a semiconductor processing tool and the
return gas stream.
28. An air conditioning and chemical filtration apparatus for a
semiconductor processing tool, comprising: an absorption section,
the absorption section comprising: an inlet for receiving a
scrubbing liquid; an absorption structure positioned in the
absorption section such that scrubbing liquid wets a surface of the
absorption structure and flows down the absorption structure; an
inlet for receiving an output gas stream from a semiconductor
processing tool, the output gas stream having one or more
contaminants, the absorption section configured such that the
output gas stream contacts scrubbing liquid on the surface of the
absorption structure and the concentration of the one or more
contaminants in the output gas stream is reduced by sorption in the
scrubbing liquid to produce an outgoing gas stream; a temperature
control unit configured to provide to the absorption section the
scrubbing liquid with a temperature in a first temperature range;
and a collection device to remove droplets of scrubbing liquid from
the outgoing gas stream and produce a return gas stream for the
semiconductor processing tool with a relative humidity in a first
relative humidity range.
29. The apparatus of claim 28, further comprising a gas temperature
control unit positioned in the return gas stream, wherein the gas
temperature control unit controls the temperature of the return gas
stream.
30. The apparatus of claim 29, wherein the gas temperature control
unit together with the temperature control unit control the
temperature and humidity of the return gas stream.
31. The apparatus of claim 28, further comprising one or more
adsorptive filters placed in the flow path of at least one of the
output gas stream from a semiconductor processing tool and the
return gas stream.
32. An air conditioning and chemical filtration apparatus for a
semiconductor processing tool, comprising: a first absorption
section, the first absorption section comprising: an inlet for
receiving a scrubbing liquid; an absorption structure positioned in
the first absorption section such that scrubbing liquid wets a
surface of the absorption structure and flows down the absorption
structure; an inlet for receiving an output gas stream from a
semiconductor processing tool, the output gas stream having one or
more contaminants, the first absorption section configured such
that the output gas stream contacts scrubbing liquid on the surface
of the absorption structure and the concentration of the one or
more contaminants in the output gas stream is reduced by sorption
in the scrubbing liquid to produce an first outgoing gas stream,
the first outgoing gas stream having one or more contaminants; a
second absorption section, the second absorption section
comprising: an inlet in the second absorption section for receiving
the first outgoing gas stream from the first absorption section; an
inlet in the second absorption section for receiving a scrubbing
liquid; an absorption structure positioned in the second absorption
section such that scrubbing liquid wets a surface of the absorption
structure and flows down the absorption structure; and the second
absorption section configured such that the outgoing gas stream
contacts scrubbing liquid on the surface of the absorption
structure in the second absorption section and the concentration of
the one or more contaminants in the outgoing gas stream is reduced
by sorption in the scrubbing liquid to produce a second outgoing
gas stream; a temperature control unit configured to provide to at
least the second absorption section the scrubbing liquid with a
temperature in a first temperature range; and a collection device
to remove droplets of scrubbing liquid from the second outgoing gas
stream and produce a return gas stream for the semiconductor
processing tool with a relative humidity in a first relative
humidity range.
33. The apparatus of claim 32, further comprising a gas temperature
control unit positioned in the return gas stream, wherein the gas
temperature control unit controls the temperature of the return gas
stream.
34. The apparatus of claim 32, wherein the gas temperature control
unit together with the temperature control unit control the
temperature and humidity of the return gas stream.
35. The apparatus of claim 32, further comprising one or more
adsorptive filters placed in the flow path of at least one of the
output gas stream from a semiconductor processing tool and the
return gas stream.
36-42. (canceled)
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
Provisional Application No. 60/485,768, filed Jul. 9, 2003. The
entire contents of the above applications are incorporated herein
by reference in entirety.
BACKGROUND OF THE INVENTION
[0002] The quality of air in semiconductor processing tools is a
major concern in the semiconductor manufacturing industry.
Photolithography tools in particular require air of appropriate
temperature, humidity and cleanliness (both with respect to
particulates and molecular contaminants).
[0003] Traditional approaches to air humidity and temperature
control use an air conditioning device that, for example, can
exchange heat with an air stream and remove or add water vapor to
the air stream.
[0004] The removal of contaminants from an air stream and, in
particular, the removal of molecular contaminants, is traditionally
performed with another device. For example, traditional approaches
typically involve the use of activated carbon filters and/or
combination of adsorptive and chemisorptive medias to control
contamination in conjunction with a temperature and/or humidity
controlling air-handling device to manage temperature and humidity
of delivered air.
[0005] Traditional approaches to contaminant removal employ
filters, or a series of filters, to remove particulates and
molecular contaminants. Particulates are generally viewed as
contaminates having a size of greater than about 0.1 microns.
Molecular contaminants are generally viewed as those contaminants
that form deposits (e.g., organics) and/or inhibit process
performance (e.g., bases).
[0006] Filters, however, have several problems. Filters increase
pressure resistance and thereby increase the pressure drop in the
air handling system for a processing tool. Filters also have a
limited service life, requiring that the filters be eventually
removed and replaced. Such replacement can require downtime of the
associated semiconductor processing tools to replace the filter
elements and add to the overall cost of ownership of the process
tool.
[0007] In addition, many filters have a limited capability in
mitigating optics-damaging volatile organic compounds, especially
in the lower molecular weight ranges because lower molecular weight
organics are typically difficult to adsorb. Increasing the
capability and/or capacity of a filter generally means adding
greater amounts of adsorptive media, which in turn further
increases pressure resistance and cost.
[0008] The filtration media of a filter may itself introduce
particulate contamination requiring downstream particulate
filtration. In addition, the filtration media of a filter may
itself introduce chemical contamination. For example, traditional
filtration methods involving the use of highly acidic medias may
introduce damaging acid anions into the air stream, such as sulfur
containing oxides, such as, for example, SO.sub.2.
[0009] In addition, the filter media of a filter, especially of
some traditional chemical filters, can create problems with air
stream temperature and humidity control For example, highly acidic
sulfonated medias (traditionally used for the removal of basic
compounds, such as ammonia and amines) are by their chemical nature
prone to reversible exothermic reactions with water (for example,
hydration reaction). This heat and humidity interaction causes
difficulty in the feedback control of air stream temperature and
humidity. Difficulties in air stream humidity and temperature
control are especially problematic in photolithography, as the
typical objective is to manage temperature and/or humidity
variation to ultra-low levels (for example, variations of less than
tens of a milliKelvin in temperature, and variations of less than
few tenths of a percent in relative humidity). Difficulties in air
stream humidity and temperature control may substantially increase
the time necessary to achieve control stability, for example,
during a start-up process of a photolithography tool. An increase
in the time to achieve control stability is directly related to
tool availability, a production metric of concern to the
semiconductor industry.
SUMMARY OF THE INVENTION
[0010] The systems and methods of the present invention include air
handling and chemical filtration of gas streams for semiconductor
processing tools. The systems and methods of the present invention
utilize a scrubbing liquid, to reduce the concentration of one or
more contaminates in the gas stream. Preferred scrubbing liquids
included, but are not limited to water, de-ionized (DI) water and
chemisorptive aqueous solutions. In preferred embodiments, the
scrubbing liquid wets the surface of an absorption structure (e.g.,
as droplets and/or a film) and one or more contaminates are removed
from the gas stream by sorption in the scrubbing liquid. For
example, one or more contaminates can be removed from the gas
stream by absorption, adsorption, dissolution, or combinations
thereof, in the scrubbing liquid. Adsorption can include, but is
not limited to, chemisorption and physisorption. In addition,
species can be removed by sorption into the scrubbing liquid, onto
the surface of the scrubbing liquid, or a combination of both.
[0011] The systems and methods of the present invention can be used
on a wide variety of molecular contaminants from a wide variety of
gas streams used in semiconductor processing tools. In various
embodiments, molecular contaminants which can be removed include,
but are not limited to, acids, bases, high and low molecular weight
organic compounds, and compound classes that include, but are not
limited to, microelectronic dopants, molecular condensables and
refractory compounds. In various embodiments, the concentration of
one or more contaminants can be reduced in gas streams including,
but are not limited to, streams of air, clean dry air (CDA),
oxygen, nitrogen, and one or more noble gases.
[0012] High molecular weight organics include compounds having
greater than about six carbon atoms (C.sub.6 compounds). Low
molecular weight organics include compounds having about six carbon
atoms or less (C.sub.1-C.sub.6 compounds). Molecular condensables
include high boiling point (i.e., boiling points greater than about
150.degree. C.) organic materials. Molecular condensables can, for
example, be adsorbed on the optical elements of a photolithography
tool and undergo deep ultra violet (DUV) light induced radical
condensation or polymerization. Such DUV light can include, for
example, 193 nm and 157 nm light. Refractory materials are
compounds containing atoms forming nonvolatile or nonreactive
oxides, for example, but not limited to, phosphorous (P), silicon
(Si), sulfur (S), boron (B), tin (Sn), aluminum (Al). These
contaminants, when exposed to DUV light, can form refractory
compounds resistant to traditional photolithography tool cleaning
approaches and even condense irreversibly on optical surfaces.
Refractory materials include refractory organics such as, for
example, silanes, siloxanes (such as, e.g., hexamethyldisiloxane),
silanols, iodates. Future examples, of molecular contaminants whose
concentration in a gas stream can be reduced by various embodiments
of systems and methods of the present invention are listed in Table
1.
TABLE-US-00001 TABLE 1 Compound Ammonia Sulfuric Acid Nitrous acid
Nitric acid Phosphoroganics Dimethyl Sulfoxide (DMSO)
Hexamethyldisiloxane (HMDSO) Silane, Tetramethoxy (TEOS) Silane,
Dimethoxydimethyl Benzene Hexane, 3-Methyl 2-Heptane Silane,
Trimethoxymethyl Hexane, 2,5-Dimethyl Toluene Propanoic acid,
2-hydroxy-ethyl ester propylene glycol methyl ether acetate (PGMEA)
dipropylene glycol methyl ether (DPGME) propylene glycol methyl
ether (PGME) Ethylbenzene n-Propylbenzene Cyclohexane Xylenes
Styrene 1,2,3 Trimethylbenzene 1,3,5 Trimethylbenzene Cyclohexanone
3-Heptanone Octane, 2,6-Dimethyl Cyclohexane, (1-Methylethyl)
Nonane Octane, 2,5,6-Trimethyl Octane, 2,2,7,7-Tetramethyl Octane,
2,2,6-Trimethyl Benzene, 1-Ethyl, 3-Methyl Decane, 2-Methyl
Benzene, 1-Ethyl, 2-Methyl Benzaldehyde Carbamic acid,
methyl-,phenyl ester Heptane,2,2,4,6,6-Pentamethyl
Decane,2,2-Dimethyl Decane 2,2,9-Trimethyl Nonane,3,7-Dimethyl
Decane,5,6-Dimethyl Decane,2,3-Dimethyl Nonane,3-Methyl-5-propyl
Decane,2,6,7-Trimethyl Heptane,4-Ethyl-2,2,6,6-Tetramethyl
Undecane,2,5-Dimethyl Undecane,4,6-Dimethyl Undecane,3,5-Dimethy
Undecane,4-methyl Nonane,3-methyl-5-propyl Undecane,5,7-Dimethyl
Undecane,3,8-Dimethyl Dodecane,2,5-Dimethyl
Heptane,2,2,3,4,6,6-Hexamethyl Dodecane,2,6,10-Trimethyl
Tridecane,5-Methyl Tridecane,4-Methyl Dodecane Benzoic acid
Cyclotetrasiloxane, Hexamethyl Cyclotetrasiloxane, Octamethyl 2,5
Cyclohexadiene-1,4-dione,2,5,-diphenyl
[0013] The systems and methods of the present invention can be used
to remove particulates from gas streams used in semiconductor
processing tools. In various embodiments, the present invention
facilitates removing particulates with an average particle size of
less than about 0.01 microns. In various embodiments, the present
invention facilitates removing particulates with an average
particle size of less than about 0.02 microns, and in various
embodiments, the present invention facilitates removing
particulates with an average particle size of less than about 0.1
microns.
[0014] The systems and methods of the present invention can be
used, for example, on a single semiconductor tool, a cluster of
tools (such as, for example, a photolithography cluster of an
exposure tool and photoresist coat/develop tool), or a tool set
(such as, for example a development track and exposure tool). In
various preferred embodiments, the present invention provides air
handling and chemical filtration systems that facilitate reducing
the cost of ownership for contamination control compared to
conventional methods of adsorptive filtration.
[0015] In various embodiments, the present invention reduces or
eliminates some of the problems associated with traditional filters
by providing a chemical filtration system that can repeatedly
regenerate a filtering media without the semiconductor tool
downtime associated with replacing traditional filter elements. In
the present invention, the filtering media includes the scrubbing
liquid.
[0016] In various embodiments, the present invention reduces or
eliminates some of the problems associated with traditional filters
by providing a chemical filtration system that utilizes a filtering
media that does not substantially generate particulates such as are
associated with traditional filter elements. In the present
invention, the filtering media includes the scrubbing liquid.
[0017] In various embodiments, the present invention reduces or
eliminates some of the problems associated with traditional filters
by providing a chemical filtration system that can remove molecular
contaminants without the humidity and temperature control
difficulties created by some traditional filter elements. For
example, by the use of a scrubbing liquid as a filtering media in
accordance with the present invention, various embodiments of the
present invention avoid introducing damaging concentrations of
acids, bases, or both into the gas stream. In various preferred
embodiments, the present inventions' approach to temperature and
humidity control is more capable of handling disturbances in
upstream temperature and humidity than traditional systems.
[0018] In various embodiments, the present invention provides an
integrated air handling and chemical filtration system for
semiconductor tools. Such integrated systems can facilitate
providing a system with a smaller footprint than the combined
footprint of traditional air handling units and filtration systems.
In addition, in various embodiments, an integrated air handling and
chemical filtration system of the present invention can facilitate
reducing capital and operating cost by combining two separate gas
stream processing needs (air conditioning and chemical filtration)
in one apparatus, simplifying the supply chain, ownership, support
and maintenance.
[0019] In preferred embodiments, the present invention reduces a
broad spectrum of chemical contamination from the gas stream
serving a photolithography tool, including, but not limited to,
contaminants such as listed in Table 1. In addition, in preferred
embodiments, the present invention provides systems and methods
that can supply a gas stream to a photolithography tool with very
small levels of temperature and humidity variation. For example, in
various preferred embodiments, the present invention provides a gas
stream with a temperature variation less than about 10 millikelvin
under constant pressure and flow rate conditions and a relative
humidity variation of less than about 0.1%. In various embodiments,
the present invention provides a gas stream with a temperature
variation in the range from about 5 millikelvin to about 20
millikelvin under constant pressure and flow rate conditions and a
relative humidity variation in the range from about 0.05% to about
0.5%. In various embodiments, the present invention provides a
combined air handling and filtration apparatus that can provide
temperature control, humidity control and filtration for a gas
stream within a pressure within about 10 inches w.c. (water column)
and a flow rate in the range from about 1 cubic feet per minute
(CFM) to about 100,000 CFM; and preferably, a flow rate in the
range from about 200 cubic feet per minute (CFM) to about 10,000
CFM.
[0020] In preferred embodiments, the invention provides a combined
air handling and chemical filtration apparatus for a
photolithography tool cluster used in the manufacture of
semiconductor devices that is sensitive to molecular contamination.
In various embodiments, the combined air-handling and filtering
system removes molecular contamination which may include acids,
bases, high and low molecular weight aromatic and aliphatic
organics, and compound classes that include, but are not limited
to, microelectronic dopants, molecular condensables and refractory
compounds.
[0021] In various embodiments, the systems and methods further
include provide metrology information. For example, in one
embodiment, the present invention provides a system that can
measure, either qualitatively, quantitatively, or both, the
concentration of one or more contaminants in a gas stream from a
semiconductor processing tool and the gas returned to the
semiconductor processing tool by a system of the invention. In one
embodiment, the invention provides methods for air handling and
filtration that use metrology information to provide a gas stream
with temperature controlled, relative humidity controlled,
contaminant reduced, or combinations thereof to a semiconductor
tool.
[0022] In various aspects, the invention also provides various
systems and methods for air handling and filtration for one or more
of pharmaceutical, biotechnology, food, and national security
applications (for example, chemical and/or biological dangers). In
various embodiments, the systems and methods of the present
invention use more than one absorption section. In various
embodiments, each absorption section or stage, can use, for
example, the same scrubbing liquid, different scrubbing liquids, or
the same scrubbing liquid with different additives in each stage.
Such staged absorption sections can be used where, for example, the
first additive is used to improve removal efficiency of one or more
contaminants but the first additive itself may be a contaminant and
the subsequent stages are used to remove the first additive from
the gas stream.
[0023] For example, in one embodiment, having first and second
absorption sections, the first absorption section is employed with
a scrubbing liquid having a first additive that facilitates removal
of one or more contaminants. Gas exiting the first absorption
section enters a second absorption section. The second absorption
section can contain a scrubbing liquid without an additive or a
scrubbing liquid with the same or a second additive. The use of a
second absorption section can provide, for example, further
contaminant removal, removal of the first additive, or both.
[0024] In various embodiments, staging absorption sections can be
used to provide information on the presence, concentration, or both
of various contaminants. For example, a first absorption section
can be used to remove a first contaminant and the concentration of
the first contaminant in the gas stream is determined from the
concentration in the scrubbing liquid exiting the first absorption
section. The second absorption section is then used to remove a
second contaminant and determine its concentration from the
scrubbing liquid exiting the first absorption section. Such staged
absorption sections, can be used in pharmaceutical, food,
biotechnology and national security applications. For example, in a
national security application one stage can be used to monitor or
remove chemical contaminants and another to monitor or remove
biological contaminants (such as, for example, particulates such as
spores).
[0025] In various embodiments, the systems and methods of the
present invention can be combined with one or more of the filter
control systems, monitoring systems, methods or combinations
thereof described in U.S. patent application Ser. Nos. 10/395,834
filed Mar. 24, 2003 and 10/205,703 filed Jul. 26, 2002, the
contents of both applications being incorporated herein by
reference in their entirety.
[0026] The foregoing and other features and advantages of the
system and method for air handling and chemical filtration of gas
streams for semiconductor processing tools will be apparent from
the following more particular description of preferred embodiments
of the system and method as illustrated in the accompanying
drawings in which like reference characters refer to the same parts
throughout the different views.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The foregoing and other objects, features and advantages of
the invention will be apparent from the following more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings in which like reference
characters refer to the same parts throughout the different views.
The drawings are not necessarily to scale, emphasis instead being
placed upon illustrating the principles of the invention.
[0028] FIG. 1 is a block diagram of a co-current air handling and
chemical filtration system in accordance with various embodiments
of the present invention;
[0029] FIG. 2 is a block diagram of a counter-current air handling
and chemical filtration system in accordance with various
embodiments of the present invention.
[0030] FIGS. 3A-3C illustrate various examples of loose packed-bed
structures;
[0031] FIGS. 3D-3E illustrate various examples of structured
packed-bed structures;
[0032] FIGS. 4A and 4B schematically illustrate, respectively, the
filling of an absorption section with a structured packed-bed
structure in FIG. 4A, and loose packed-bed structure in FIG.
4B;
[0033] FIG. 5 is a schematic cut-away view of a counter-current air
handling and chemical filtration system in accordance with various
embodiments of the present invention; and
[0034] FIG. 6 is a schematic cut-away view of a co-current air
handling and chemical filtration system in accordance with various
embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] Various preferred embodiments of air handling and chemical
filtration systems in accordance with the present invention are
illustrated in FIGS. 1 and 2. In FIGS. 1 and 2 gas flows are
indicated by dashed lines and liquid flows by solid lines. The
arrow heads on the dashed and solid lines indicate, respectively,
the nominal direction of gas flow and liquid flow. In FIGS. 1 and 2
the systems and methods of the present invention are discussed in
the context of de-ionized (DI) water as the scrubbing liquid,
however, the present invention is not limited to a DI water
scrubbing liquid. Other suitable scrubbing liquids encompassed by
the present invention include, but are not limited to, water, oils,
non-polar solvents and polar solvents such as, for example,
alcohols. In embodiments using a scrubbing fluid comprising
de-ionized water, it is preferred that the de-ionized water has a
resistivity in the range from about 100,000 ohm centimeters
(.OMEGA.cm) to about 18 M.OMEGA. cm.
[0036] FIG. 1 depicts a block diagram 100 of various embodiments of
a co-current filtration system that are in accordance with the
present invention. In a co-current system, an input scrubbing
liquid stream 106 is introduced into an absorption section 110 in a
similar flow direction to that of an output gas stream 108 from a
semiconductor processing tool or tool set 120. More than one
absorption section may be repeated, in series, within a co-current
system to increase, for example, contaminant removal. One or more
counter-current absorption sections can also be used in series with
one or more co-current sections. The absorption section contains an
absorption structure wetted by the scrubbing liquid. As the gas
passes the surfaces of the absorption structure wetted by scrubbing
liquid, molecular contaminants with a higher chemical potential in
the gas stream than the scrubbing liquid pass from the gas stream
to the scrubbing liquid. The system thus provides to the tool or
tool set 120 a return gas stream 124 with a reduced concentration
of one or more contaminants found in the output gas stream 108
(also referred to herein as the incoming gas stream because it is
incoming to the absorption section 110).
[0037] In preferred embodiments, the input scrubbing liquid 106 is
introduced as an aerosol prior to the absorption structure in
sufficient volume and temperature to form a liquid which wets and
flows down the surfaces of the absorption structure. An aerosol of
scrubbing liquid can be formed in many ways including, but not
limited to, spray nozzle systems that inject into a "contacting
zone" and systems that apply jets of compressed air onto the
surface of a rotating or stationary scrubbing liquid distributor
within the compressed air stream.
[0038] The absorption structure can comprise a loose packed-bed
structure, structured packed-bed structure, or a combination of
both. Preferably the absorption structure is a loose packed-bed
structure, such as for example, Q-Pack, Lanpack and/or Nupack all
manufactured by Lantec, Inc., Raschig rings, Pall rings, Berl
saddles, Inatolex saddles, Flexrings, Ballast rings, and Cascade
rings. Examples of structured packed-bed structures include, but
are not limited to, Gempack.TM. cartridges, and Glitsch EF-25A
Grid.TM., manufactured by Glitsch, Inc., of Dallas, Tex. FIGS.
3A-3E show examples of various packed-bed structures, where FIG. 3A
301 is an example of a ceramic Intalox.TM. saddle; FIG. 3B 303 is
an example of a plastic Super Intalox.TM. saddle; FIG. 3C 305 is an
example of a Pall ring; FIG. 3D 307 is an example of a Gempack.TM.
cartridge; and FIG. 3E 309 is an example of a Glitsch EF-25A
Grid.TM.. The design of the absorption structure is preferably such
that there is sufficient residence time of the gas stream to allow
for mass transfer of molecular contaminants from the output gas
stream to the scrubbing liquid on the absorption structure.
[0039] In various embodiments, the absorption section includes a
source of UV energy (for example, such as a UV lamp) and absorption
structures having TiO.sub.2 coated surfaces. In combination with
sufficient UV energy, such absorption sections are used to perform
catalytic reactions within the absorption section that reduce
organic compounds and facilitate their removal from an incoming gas
stream.
[0040] In various embodiments, the incoming gas stream 108 is
pre-processed with a pre-processor device 130 prior to entering the
absorption section 110. In various embodiments, the pre-processor
device 130 includes a source of UV energy (for example, such as a
UV lamp) and surfaces coated with a photocatalyst such as, for
example, TiO.sub.2, ZnO, WO.sub.3, or other inorganic compounds
with proper UV light absorbing properties. In combination with
sufficient UV energy, such pre-processor devices are used to
perform photocatalytic reactions that can reduce organic (polar and
non-polar) compounds and facilitate their removal from an incoming
gas stream. For example, photocatalytical reaction can cause a
partial "mineralization" of organic compounds (for example,
formation of CO.sub.2, H.sub.2O) and the formation of by-products,
the prevailing fraction of which are oxygenated substances. Thus
non-polar compounds can be "transformed" to polar compounds which
can be more effectively removed by a scrubbing liquid. In various
embodiments, gaseous chlorine-containing compounds like
trichloroethylene (TCE) or perchloroethylene (PCE), which greatly
accelerate photocatalytical reaction of organics via additional
chain reaction with Cl species, can be added to the incoming gas
stream by the pre-processor device to, for example, "spike" the gas
stream. Chlorine containing by-products and HCl formed in this case
can be effectively removed by the scrubbing liquid and, in various
embodiments, increase the scrubbing liquids removal efficiency
towards bases due to this induced activity.
[0041] In various embodiments, a pre-processor device 130
introduces additives into the incoming gas stream 108 that
facilitates the removal of one or more contaminates in the gas
stream. The additive can, for example; (1) chemically reactive with
one or more containments to produce species that are more readily
removed by the scrubbing liquid; (2) change the chemical potential
of one or more contaminants with respect to the scrubbing liquid to
facilitate there removal; and (3) facilitate contaminant detection
and concentration determination, for example, to provide metrology
information, hazard warnings, et al.
[0042] The molecular contaminants which have a higher chemical
potential in the gas stream than in the scrubbing liquid on the
surfaces of the absorption structure are absorped by the scrubbing
liquid. In addition, because the expected concentration of some
contaminants in the incoming gas stream are expected to be low (for
example, typically lower than about 50 micrograms per cubic meter
(.mu.g/m.sup.3) for non-polar organics); in the present invention,
polar scrubbing liquids are not limited to reducing the
concentration of polar contaminants and non-polar scrubbing liquids
are not limited to reducing the concentration of non-polar
contaminants. For example, non-polar organic contaminants with, for
example, concentrations less than about 50 .mu.g/m.sup.3, can have
sufficient solubility within a polar scrubbing liquid, such as, for
example DI water, such that the scrubbing liquid can reduce the
concentration of one or more of these non-polar organics.
[0043] At the end of the absorption section 110, a collection
device 140 removes scrubbing liquid droplets from an outgoing gas
stream 142. In preferred embodiments, the scrubbing liquid
comprises DI water and the collection device 140 removes water
droplets from the gas stream 142 such that the return gas stream
124 is saturated with water vapor at a desired relative humidity.
Suitable approaches and devices for scrubbing liquid droplets from
a gas stream, include, but are not limited to, collection by
coalescing media, collection by vane separators and collection by
an extended surface of a packed bed.
[0044] In various embodiments, the system includes a gas
temperature control unit 143 that can adjust the temperature of the
return gas stream 124. The gas temperature control unit can include
a heater, cooler, or both. In various embodiments, the system can
include a non-condensing regenerative heat exchanger 144. The heat
exchanger 144, for example, can exchange enthalpy from the "warm"
incoming gas stream 108 to the colder "washed" gas stream 124. The
heat "recovered" can reduce any heating requirements for the return
air stream 124 when the return air stream is colder than the output
air stream 108. A reduction in heating requirements can reduce
electrical power consumption, such as by electrical resistive
elements, and thereby conserve energy resources and reduce
operating costs.
[0045] The scrubbing liquid 146 exiting the absorption section is
cleaned and recirculated with a recirculation unit 148 to provide
cleaned scrubbing liquid 150. In various embodiments, scrubbing
liquid removed 152 from the return gas stream is also conveyed to
the recirculation unit 148 for cleaning and recirculation.
Generally, separation of molecular contaminants from a liquid (such
as, for example, separation of ionic species for DI water) is
significantly more efficient with lower typical operating costs
than atmospheric-pressure gas phase separation.
[0046] In preferred embodiments, the scrubbing liquid comprises DI
water. DI water can be cleaned in a recirculated loop using
conventional methods, such as, for example, (UF/RO), twin bed ion
exchange resins, mixed bed resin bottles, and organic membrane
separation, and liquid-phase carbon adsorption for organics removal
and particle filtration for particulate removal. Scrubbing liquid
cleaning can include, for example, photocatalysis on immobilized
TiO.sub.2 or TiO.sub.2 slurry, and advanced oxidation processes,
such as, for example, processes which include H.sub.2O.sub.2,
O.sub.3, Fenton's reagent, and ionizing radiation.
[0047] In various embodiments, the DI water is also treated by the
recirculation unit to prevent biological fouling of the absorption
structure and other wetted sections of the system, because, for
example, de-ionized water containing dissolved chemical species
(particulate, organic, and inorganic) can provide a reasonable
source of "food" for biological activity. Suitable treatments to
prevent biological fouling include, but are not limited to
irradiation of the DI water with ultra violet (UV) light in the C
band (about 200 nm to about 290 nm), ozonization and
peroxidation.
[0048] To maintain scrubbing liquid volume, in various embodiments,
scrubbing liquid is supplied as required from a scrubbing liquid
supply 154. If the supply 154 provides sufficiently clean scrubbing
liquid, then make-up scrubbing liquid can be supplied directly 156
and mixed with the cleaned scrubbing liquid 150. The supply 154 can
also provide make-up fluid 158 to the recirculation unit 148. The
scrubbing liquid supply can be any suitable supply source. For
example, where the scrubbing liquid comprises DI water, the
scrubbing liquid supply can be a DI water source or even tap water
which can, for example, be de-ionized and further cleaned as needed
by the recirculation unit.
[0049] In preferred embodiments, the chemical filtration system
further includes a temperature control unit 160 to control the
temperature of scrubbing liquid 162. In various embodiments, the
temperature of the scrubbing liquid is used to control the
temperature, relative humidity, or both of the return gas stream
124. In various embodiments, the gas temperature control unit 143
(and/or heat exchanger 144) together with the temperature control
unit 160 is used to control the temperature, relative humidity, or
both of the return gas stream 124.
[0050] In preferred embodiments, the present invention uses the
temperature of the scrubbing liquid to control the relative
humidity of the return gas stream by selecting the temperature of
the scrubbing liquid to obtain a desired relative humidity of the
return gas stream after any temperature adjustment by a heat
exchanger and/or gas temperature control unit. The appropriate
scrubbing liquid temperature needed to obtain a desired relative
humidity of the return gas stream at a given temperature can be
determined using, for example, a form of the Clausius-Clapeyron
equation.
[0051] In various preferred embodiments, one or more additives are
added from an additive source 170 to the scrubbing liquid to
change, for example, the chemical potential or solubility of the
scrubbing liquid with respect to one or more contaminants in an
incoming gas stream 108. The additive source can provide, for
example, an additive in substantially pure form or one pre-mixed
with scrubbing liquid. In addition, multiple additive sources can
be used.
[0052] In various embodiments, an additive can be added 172, for
example, to cleaned scrubbing liquid 150 and/or make-up fluid 156,
directly or in a mixing device 174. In various embodiments, an
additive is added after 176 the temperature control unit 160
(directly or in a mixing device 178) to better control, for
example, the concentration of the additive in the scrubbing liquid.
The mixing devices 174, 178 can be any device suitable for mixing
the additive with the scrubbing liquid and can comprise a device as
simple as turbulence in a valve.
[0053] Preferably an additive provides easily rectified reactive
chemistries. For example, in various embodiments, ozone (O.sub.3)
or peroxides (such as, for example, H.sub.2O.sub.2) are introduced
as an additive in sufficient concentration to oxidize organic and
inorganic contaminants; such as, for example NO and SO.sub.2,
through reactions such as, for example:
##STR00001##
which increase the solubility of the noted contaminants in
water.
[0054] In various embodiments, organic compounds reacting with
oxygen radicals (such as can be provided, for example, by an ozone
or peroxide additive) are used to produce more polar (and thus more
water-soluble) species. The preferred effect of an additive in the
present invention is to shift the equilibrium between the gas and
liquid phases such that contaminants are more readily removed. In
embodiments including an ozone additive, for example, it is
preferred that a filter media (such as a granulated activated
carbon media) be provided downstream of the absorption section to
remove residual ozone by, for example, room temperature catalytic
destruction. Other additives for a scrubbing liquid include, but
are not limited to, acids, bases and monoethanolamine.
[0055] It is preferred that additives and their concentrations are
chosen such that they do not result in unacceptable health or
explosive hazards, or comprise species that can have an
unacceptable impact on the process being performed by the
semiconductor processing tool or tool set 120. For example,
monoethanolamine may not be appropriate due its hazardous effect on
amplified resist processes.
[0056] In various embodiments, co-current systems and methods are
useful for those contaminant removal reactions having favorable
equilibrium (e.g., equilibrium which favor contaminant absorption
into the scrubbing liquid throughout the absorption section), and
in some situations co-current systems and methods are preferred
such that high scrubbing liquid-gas stream interface areas can be
achieved. Where contaminant removal reactions have unfavorable
equilibrium, various embodiments of a counter-current systems and
methods in accordance with the present invention are preferred.
[0057] FIG. 2 depicts a block diagram 200 of various embodiments of
a counter-current filtration system that are in accordance with the
present invention. In a counter-current system, an input scrubbing
liquid stream 206 is introduced into an absorption section 210 in a
flow direction counter to that of an output gas stream 208 from a
semiconductor processing tool or tool set 220. More than one
absorption section may be repeated, in series, within a
counter-current system to increase, for example, contaminant
removal. The absorption section contains an absorption structure
wetted by the scrubbing liquid. As the gas passes the surfaces of
the absorption structure wetted by scrubbing liquid, molecular
contaminants with a higher chemical potential in the gas stream
than scrubbing liquid pass from the gas stream to the scrubbing
liquid. The system thus provides to the tool or tool set 220 a
return gas stream 224 with a reduced concentration of one or more
contaminants found in the output gas stream 208 (also referred to
herein as the incoming gas stream because it is incoming to the
absorption section 210).
[0058] After some period of operation, the incoming gas stream 208
begins to contact scrubbing liquid that contains some concentration
of one or more contaminants removed from the gas streams. Although
such contaminants in the scrubbing liquid tend to disfavor removal
of the same contaminant species from the gas stream, the
concentration of contaminants in the gas stream is also highest as
it enters the absorption section, which shifts contaminant removal
equilibrium in favor of contaminant removal.
[0059] As the gas stream progresses, the concentration of one or
more contaminants decreases due to removal by the scrubbing liquid.
Although the decrease in contaminant concentration in the gas
stream tends to disfavor further removal of contaminants, the
concentration of contaminants in the scrubbing liquid is also
decreasing as the gas stream approaches the input scrubbing liquid.
This decrease in contaminant concentration in the scrubbing liquid
shifts contaminant equilibrium in favor of contaminant removal.
[0060] In preferred embodiments, the input scrubbing liquid 206 is
introduced as an aerosol above the absorption structure in
sufficient volume and temperature to form a liquid which wets and
flows down the surfaces of the absorption structure. An aerosol of
scrubbing liquid can be formed in many ways including, but not
limited to, spray nozzle systems that inject into a "contacting
zone" and systems that apply jets of compressed air onto the
surface of a rotating or stationary scrubbing liquid distributor
within the compressed air stream.
[0061] The absorption structure can comprise a loose packed-bed
structure, structured packed-bed structure, or a combination of
both. Preferably the absorption structure is a loose packed-bed
structure, such as for example, Q-Pack, Lanpack and/or Nupack all
manufactured by Lantec, Inc., Raschig rings, Pall rings, Berl
saddles, Inatolex saddles, Flexrings, Ballast rings, and Cascade
rings. Examples of structured packed-bed structures include, but
are not limited to, Gempack.TM. cartridges, and Glitsch EF-25A
Grid.TM., manufactured by Glitsch, Inc., of Dallas, Tex. FIGS.
3A-3E show examples of various packed-bed structures, where FIG. 3A
301 is an example of a ceramic Intalox.TM. saddle; FIG. 3B 303 is
an example of a plastic Super Intalox.TM. saddle; FIG. 3C 305 is an
example of a Pall ring; FIG. 3D 307 is an example of a Gempack.TM.
cartridge; and FIG. 3E 309 is an example of a Glitsch EF-25A
Grid.TM.. The design of the absorption structure is preferably such
that there is sufficient residence time of the gas stream to allow
for mass transfer of molecular contaminants from the output gas
stream to the scrubbing liquid on the absorption structure.
[0062] In various embodiments, the absorption section includes a
source of UV energy (for example, such as a UV lamp) and absorption
structures having TiO.sub.2 coated surfaces. In combination with
sufficient UV energy, such absorption sections are used to perform
catalytic reactions within the absorption section that reduce
organic compounds and facilitate their removal from an incoming gas
stream.
[0063] In various embodiments, the incoming gas stream 108 is
pre-processed with a pre-processor device 130 prior to entering the
absorption section 110. In various embodiments, the pre-processor
device 130 includes a source of UV energy (for example, such as a
UV lamp) and surfaces coated with a photocatalyst such as, for
example, TiO.sub.2, ZnO, WO.sub.3, or other inorganic compounds
with proper UV light absorbing properties. In combination with
sufficient UV energy, such pre-processor devices are used to
perform photocatalytic reactions that can reduce organic (polar and
non-polar) compounds and facilitate their removal from an incoming
gas stream. For example, photocatalytical reaction can cause a
partial "mineralization" of organic compounds (for example,
formation of CO.sub.2, H.sub.2O) and the formation of by-products,
the prevailing fraction of which are oxygenated substances. Thus
non-polar compounds can be "transformed" to polar compounds which
can be more effectively removed by a scrubbing liquid. In various
embodiments, gaseous chlorine-containing compounds like
trichloroethylene (TCE) or polychloroethylene (PCE), which are
greatly accelerate photocatalytical reaction of organics via
additional chain reaction with Cl species, can be added to the
incoming gas stream by the pre-processor device to, for example,
"spike" the gas stream. Chlorine containing by-products and HCl
formed in this case can be effectively removed by the scrubbing
liquid and, in various embodiments, increase the scrubbing liquids
removal efficiency towards bases due to this induced activity.
[0064] In various embodiments, a pre-processor device 230 adds on
additions for the incoming gas stream 208 that facilitates the
removal of one or more contaminates in the gas stream. The additive
can, for example; (1) chemically reactive with one or more
containments to produce species that are more readily removed by
the scrubbing liquid; (2) change the chemical potential of one or
more contaminants with respect tot the scrubbing liquid to
facilitate there removal; and (3) facilitate contaminant detection
and concentration determination, for example, to provide metrology
information, hazard warnings, et al.
[0065] The molecular contaminants which have a higher chemical
potential in the gas stream than in the scrubbing liquid on the
surfaces of the absorption structure are absorped by the scrubbing
liquid. In addition, because the expected concentration of some
contaminants in the incoming gas stream are expected to be low (for
example, typically lower than about 50 .mu.g/m.sup.3 for non-polar
organics); in the present invention, polar scrubbing liquids are
not limited to reducing the concentration of polar contaminants and
non-polar scrubbing liquids are not limited to reducing the
concentration of non-polar contaminants. For example, non-polar
organics contaminants with, for example, concentrations less than
about 50 .mu.g/m.sup.3, can have sufficient solubility within a
polar scrubbing liquid of the present invention such as, for
example DI water, such that the scrubbing liquid can reduce the
concentration of one or more of these non-polar organics.
[0066] At the end of the absorption section 210, a collection
device 240 removes scrubbing liquid droplets from an outgoing gas
stream 242. In preferred embodiments, the scrubbing liquid
comprises DI water and the collection device 240 removes water
droplets from the gas stream 242 such that the return gas stream
224 is saturated with water vapor at a desired relative humidity.
Suitable approaches and devices for scrubbing liquid droplets from
a gas stream, include, but are not limited to, collection by
coalescing media, collection by vane separators and collection by
an extended surface of a packed bed.
[0067] In various embodiments, the system includes a gas
temperature control unit 243 that can adjust the temperature of the
return gas stream 224. The gas temperature control unit can include
a heater, cooler, or both. In various embodiments, the system can
include a non-condensing regenerative heat exchanger 244. The heat
exchanger 244, for example, can exchange enthalpy from the "warm"
incoming gas stream 208 to the colder "washed" gas stream 224. The
heat "recovered" can reduce any heating requirements for the return
air stream 224 when the return air stream is colder than the output
air stream 208. A reduction in heating requirements can reduce
electrical power consumption, such as by electrical resistive
elements, and thereby conserve energy resources and lower operating
costs.
[0068] The scrubbing liquid 246 exiting the absorption section is
cleaned and recirculated with a recirculation unit 248 to provide
cleaned scrubbing liquid 250. In various embodiments, scrubbing
liquid removed 252 from the return gas stream is also conveyed to
the recirculation unit 248 for cleaning and recirculation.
Generally, separation of molecular contaminants from a liquid (such
as, for example, separation of ionic species for DI water) is
significantly more efficient with lower typical operating costs
than atmospheric-pressure gas phase separation.
[0069] In preferred embodiments, the scrubbing liquid comprises DI
water. DI water can be cleaned in a recirculated loop using
conventional methods, such as, for example, (UF/RO), twin bed ion
exchange resins, mixed bed resin bottles, and organic membrane
separation, and liquid-phase carbon adsorption for organics removal
and particle filtration for particulate removal. Scrubbing liquid
cleaning can include, for example, photocatalysis on immobilized
TiO.sub.2 or TiO.sub.2 slurry, and advanced oxidation processes,
such as, for example, processes which include H.sub.2O.sub.2,
O.sub.3, Fenton's reagent, and ionizing radiation.
[0070] In various embodiments, the DI water is also treated by the
recirculation unit to prevent biological fouling of the absorption
structure and other wetted sections of the system, because, for
example, de-ionized water containing dissolved chemical species
(particulate, organic, and inorganic) can provide a reasonable
source of "food" for biological activity. Suitable treatments to
prevent biological fouling include, but are not limited to
irradiation of the DI water with ultra violet (UV) light in the C
band (about 200 nm to about 290 nm), ozonization, and
peroxidation.
[0071] To maintain scrubbing liquid volume, in various embodiments,
scrubbing liquid is supplied as required from a scrubbing liquid
supply 254. If the supply 254 provides sufficiently clean scrubbing
liquid, then make-up scrubbing liquid can be supplied directly 156
and mixed with the cleaned scrubbing liquid 250. The supply 254 can
also provide make-up fluid 258 to the recirculation unit 248. The
scrubbing liquid supply can be any suitable supply source. For
example, where the scrubbing liquid comprises DI water, the
scrubbing liquid supply can be a DI water source or even tap water
which can, for example, be de-ionized and further cleaned as needed
by the recirculation unit.
[0072] In preferred embodiments, the chemical filtration system
further includes a temperature control unit 260 to control the
temperature of scrubbing liquid 262. In various embodiments, the
temperature of the scrubbing liquid is used to control the
temperature, relative humidity, or both of the return gas stream
224. In various embodiments, the gas temperature control unit 243
(and/or heat exchanger 244) together with the temperature control
unit 260 is used to control the temperature, relative humidity, or
both of the return gas stream 224.
[0073] In preferred embodiments, the present invention uses the
temperature of the scrubbing liquid to control the relative
humidity of the return gas stream by selecting the temperature of
the scrubbing liquid to obtain a desired relative humidity of the
return gas stream after any temperature adjustment by a heat
exchanger and/or gas temperature control unit. The appropriate
scrubbing liquid temperature needed to obtain a desired relative
humidity of the return gas stream at a given temperature can be
determined using, for example, a form of the Clausius-Clapeyron
equation.
[0074] In various preferred embodiments, one or more additives are
added from an additive source 270 to the scrubbing liquid to
change, for example, the chemical potential of the scrubbing liquid
with respect to one or more contaminants in an incoming gas stream
208. The additive source can provide, for example, an additive in
substantially pure form or one pre-mixed with scrubbing liquid. In
addition, multiple additive sources can be used.
[0075] In various embodiments, an additive can be added 272, for
example, to cleaned scrubbing liquid 250 and/or make-up fluid 256,
directly or in a mixing device 274. In various embodiments, an
additive is added after 276 the temperature control unit 260
(directly or in a mixing device 278) to better control, for
example, the concentration of the additive in the scrubbing liquid.
The mixing devices 274, 278 can be any device suitable for mixing
the additive with the scrubbing liquid and can comprise a device as
simple as turbulence in a valve.
[0076] Preferably an additive provides easily rectified reactive
chemistries. For example, in various embodiments, ozone (O.sub.3)
or peroxides (such as, for example, H.sub.2O.sub.2) are introduced
as an additive in sufficient concentration to oxidize organic and
inorganic contaminants; such as, for example NO and SO.sub.2,
through reactions such as, for example, reaction (1) and (2) above
which increase the solubility of the noted contaminants in
water.
[0077] In various embodiments, organic compounds reacting with
oxygen radicals (such as can be provided, for example, by an ozone
or peroxide additive) are used to produce more polar (and thus more
water-soluble) species. The preferred effect of an additive in the
present invention is to shift the equilibrium between the gas and
liquid phases such that contaminants are more readily removed. In
embodiments including an ozone additive, for example, it is
preferred that a filter media (such as a granulated activated
carbon media) be provided downstream of the absorption section to
remove residual ozone by, for example, room temperature catalytic
destruction. Other additives for a scrubbing liquid include, but
are not limited to, acids, bases and monoethanolamine.
[0078] It is preferred that additives and their concentrations are
chosen such that they do not result in unacceptable health or
explosive hazards, or comprise species that can have an
unacceptable impact on the process being performed by the
semiconductor processing tool or tool set 220. For example,
monoethanolamine may not be appropriate due its hazardous effect on
amplified resist processes.
[0079] Referring to FIGS. 4A and 4B, FIG. 4A schematically depicts
the filling of a portion of an absorption section with a structured
packed-bed structure 402 and FIG. 4B schematically depicts the
filling of a portion of an absorption section with a loose
packed-bed structure 404. The packed-bed structures are disposed
between walls of a column 406, 410, that can be the walls of an
absorption section or of one or more columns within an absorption
section. Structured packed-bed material 408 is preferably arranged
within the column in an ordered fashion, whereas loose packed-bed
material 412 is preferably distributed in a random fashion and
supported in the absorption section by a support grid 414. The
loose packed material has the advantage of greater surface area and
higher capacity.
[0080] FIG. 5 depicts schematically a cut-away view of a
counter-current system, the incoming gas stream 508 enters the
absorption section 510. Scrubbing liquid is introduced by a
scrubbing liquid distributor 511 prior to the absorption structure
512. The incoming gas stream passes the wetted surfaces of the
absorption structure 512 and is returned as a return gas stream
524. Prior to being returned, the gas stream temperature can be
adjusted (for example, raised or lowered) by a gas temperature
control unit 543 placed, for example, in the return gas stream 524
flow path.
[0081] In various embodiments, a scrubbing liquid reservoir 554
after the absorption structure captures scrubbing liquid which is
recalculated by a recirculation unit 548 including a circulation
pump 549 and a liquid phase chemical/particulate filters 550. The
temperature of the cleaned scrubbing liquid can be controlled by a
temperature control unit 560 prior to delivery to the scrubbing
liquid distributor 511.
[0082] FIG. 6 depicts schematically a cut-away view of a co-current
system, the incoming gas stream 608 enters the absorption section
610 and comes into contact with scrubbing liquid introduced by a
scrubbing liquid distributor 611 prior to the absorption structure
612. The incoming gas stream passes the wetted surfaces of the
absorption structure 612 and is returned as a return gas stream
624. Prior to being returned, the gas stream temperature can be
adjusted (for example, raised. lowered) by a gas temperature
control unit 643 placed, for example, in the return gas stream 624
flow path.
[0083] In various embodiments, a scrubbing liquid reservoir 654
after the absorption structure captures scrubbing liquid which is
recalculated by a recirculation unit 648 including a circulation
pump 649 and a liquid phase chemical/particulate filters 650. The
temperature of the cleaned scrubbing liquid can be controlled by a
temperature control unit 660 prior to delivery to the scrubbing
liquid distributor 611.
[0084] The claims should not be read as limited to the described
order or elements unless stated to that effect. Therefore, all
embodiments that come within the scope and spirit of the following
claims and equivalents thereto are claimed as the invention.
* * * * *