U.S. patent application number 11/316329 was filed with the patent office on 2006-07-20 for distributed temperature control system for point of dispense temperature control on track systems utilizing mixing of hot and cold streams.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Sudhir R. Gondhalekar, Tetsuya Ishikawa.
Application Number | 20060158240 11/316329 |
Document ID | / |
Family ID | 39193608 |
Filed Date | 2006-07-20 |
United States Patent
Application |
20060158240 |
Kind Code |
A1 |
Gondhalekar; Sudhir R. ; et
al. |
July 20, 2006 |
Distributed temperature control system for point of dispense
temperature control on track systems utilizing mixing of hot and
cold streams
Abstract
A point of dispense temperature control apparatus for a track
lithography system. The apparatus includes a first liquid source
characterized by a first temperature and a first flow controller
coupled to the first liquid source. The apparatus also includes a
second liquid source characterized by a second temperature and a
second flow controller coupled to the second liquid source. The
apparatus further includes a mixing element coupled to the first
flow controller and the second flow controller. The mixing element
is adapted to provide a mixed stream characterized by a total flow
volume and a temperature intermediate to the first temperature and
the second temperature. The apparatus additionally includes a
sensor coupled to the mixed stream, a point of dispense heat
exchanger coupled to the mixed stream, and a control loop coupled
to the sensor and at least one of the first flow controller or the
second flow controller. The control loop is adapted to provide a
consistent total flow volume at the intermediate temperature.
Inventors: |
Gondhalekar; Sudhir R.;
(Fremont, CA) ; Ishikawa; Tetsuya; (Saratoga,
CA) |
Correspondence
Address: |
TOWNSEND AND TOWNSEND AND CREW LLP / AMAT
TWO EMBARCADERO CENTER
EIGHTH FLOOR
SAN FRANCISCO
CA
94111-3834
US
|
Assignee: |
Applied Materials, Inc.
Santa Clara
CA
|
Family ID: |
39193608 |
Appl. No.: |
11/316329 |
Filed: |
December 21, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60639109 |
Dec 22, 2004 |
|
|
|
Current U.S.
Class: |
327/350 |
Current CPC
Class: |
H01L 21/67225 20130101;
G03D 13/006 20130101; H01L 21/67109 20130101; H01L 21/6838
20130101; H01L 21/67742 20130101; G03B 27/32 20130101; H01L
21/67196 20130101; H01L 21/67748 20130101; Y10S 414/136 20130101;
Y10T 29/53187 20150115; Y02P 90/02 20151101; G05B 2219/45031
20130101; H01L 21/68707 20130101; Y10T 29/5323 20150115; H01L
21/6831 20130101; G03F 7/40 20130101; G05B 2219/40476 20130101;
H01L 21/6715 20130101; G05B 19/41825 20130101; H01L 21/67173
20130101; H01L 21/67745 20130101; G05B 2219/49137 20130101; H01L
22/26 20130101; H01L 21/67184 20130101; H01L 21/67178 20130101;
H01L 21/6719 20130101; H01L 21/67754 20130101; Y02P 90/087
20151101; H01L 21/67161 20130101; Y10S 414/135 20130101 |
Class at
Publication: |
327/350 |
International
Class: |
G06G 7/24 20060101
G06G007/24 |
Claims
1. A point of dispense temperature control apparatus for a track
lithography system, the apparatus comprising: a first liquid source
characterized by a first temperature; a first flow controller
coupled to the first liquid source; a second liquid source
characterized by a second temperature; a second flow controller
coupled to the second liquid source; a mixing element coupled to
the first flow controller and the second flow controller, the
mixing element being adapted to provide a mixed stream
characterized by a total flow volume and a temperature intermediate
to the first temperature and the second temperature; a sensor
coupled to the mixed stream; a point of dispense heat exchanger
coupled to the mixed stream; and a control loop coupled to the
sensor and at least one of the first flow controller or the second
flow controller, wherein the control loop is adapted to provide a
consistent total flow volume at the intermediate temperature.
2. The apparatus of claim 1 wherein the first liquid source and the
second liquid source are packaged in a single unit.
3. The apparatus of claim 1 wherein the control loop is coupled to
the sensor and the first flow controller.
4. The apparatus of claim 1 wherein the control loop is coupled to
the sensor and the second flow controller.
5. The apparatus of claim 1 further comprising: a third flow
controller coupled to the mixed stream and the first liquid source;
and a fourth flow controller coupled to the mixed stream and the
second liquid source.
6. The apparatus of claim 5 wherein a flow rate of the first fluid
through the first flow controller is substantially equal to a flow
rate of the mixed stream through the third flow controller.
7. The apparatus of claim 1 wherein the sensor is a resistance
temperature detector sensor.
8. The apparatus of claim 1 wherein the control loop comprises a
proportional-integral-derivative controller.
9. The apparatus of claim 8 wherein the
proportional-integral-derivative controller provides a control
signal utilized to modulate the flow rate of the second fluid
through the second flow controller.
10. The apparatus of claim 1 wherein the first flow controller and
the second flow controller are adapted to pressure balance a first
fluid pressure associated with the first liquid source and a second
fluid pressure associated with the second liquid source.
11. The apparatus of claim 1 wherein the point of dispense heat
exchanger is coupled to a photolithography chemical dispense
system.
12. A point of dispense temperature control apparatus for a track
lithography system, the apparatus comprising: a first fluid source
characterized by a first temperature; a first flow regulator
coupled to the first fluid source; a second fluid source
characterized by a second temperature; a second flow regulator
coupled to the second fluid source; a mixing element coupled to the
first fluid source and the second fluid source, the mixing element
being adapted to provide a mixed stream characterized by a
temperature intermediate to the first temperature and the second
temperature; a sensor coupled to the mixed stream; a point of
dispense heat exchanger coupled to the mixed stream; a fluid return
path coupled to the point of dispense heat exchanger and adapted to
deliver fluid to at least one of the first fluid source or the
second fluid source; and a control loop coupled to the sensor and
at least one of the first flow controller or the second flow
controller.
13. The apparatus of claim 12 wherein the flow rate of the mixed
stream is characterized by a constant total flow rate during a
predetermined time period.
14. The apparatus of claim 12 wherein the sensor is a resistance
temperature detector sensor.
15. The apparatus of claim 12 wherein the control loop comprises a
proportional-integral-derivative controller and an
electro-pneumatic regulator.
16. The apparatus of claim 15 wherein the
proportional-integral-derivative controller provides a control
signal utilized to modulate the flow rate of the second fluid
through the second flow controller.
17. A method of providing distributed temperature control for
multiple point of dispense heat exchangers in a track lithography
system, the method comprising: providing a first fluid stream
characterized by a first temperature; providing a second fluid
stream characterized by a second temperature; providing a first
fluid flow path coupled to the first fluid stream; providing a
second fluid flow path coupled to the second fluid stream; mixing
the first fluid stream and the second fluid stream to provide a
mixed fluid stream characterized by a third temperature; monitoring
the third temperature; modulating a flow rate of at least one of
the first fluid stream or the second fluid stream in response to
monitoring the third temperature; and coupling the mixed stream to
a plurality of point of dispense heat exchangers adapted to control
a temperature associated with photolithography chemistry.
18. The method of claim 17 wherein the third temperature is
intermediate to the first temperature and the second
temperature.
19. The method of claim 17 wherein each of the plurality or point
of dispense heat exchangers are coupled to a portion of a
photolithography chemistry dispense system.
20. The method of claim 19 wherein the portions of the
photolithography chemistry dispense system are operable to provide
independent temperature set points for photolithography chemistry
fluids.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 60/639,109, filed Dec. 22, 2004, entitled
"Twin Architecture For Processing A Substrate," the disclosure of
which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to the field of
substrate processing equipment. More particularly, the present
invention relates to a method and apparatus for providing point of
dispense temperature control for semiconductor process chemistry.
The method and apparatus can be applied to other processes for
semiconductor substrates, for example those used in the formation
of integrated circuits.
[0003] Modern integrated circuits contain millions of individual
elements that are formed by patterning the materials, such as
silicon, metal and/or dielectric layers, that make up the
integrated circuit to sizes that are small fractions of a
micrometer. The technique used throughout the industry for forming
such patterns is photolithography. A typical photolithography
process sequence generally includes depositing one or more uniform
photoresist (resist) layers on the surface of a substrate, drying
and curing the deposited layers, patterning the substrate by
exposing the photoresist layer to electromagnetic radiation that is
suitable for modifying the exposed layer and then developing the
patterned photoresist layer.
[0004] It is common in the semiconductor industry for many of the
steps associated with the photolithography process to be performed
in a multi-chamber processing system (e.g., a cluster tool) that
has the capability to sequentially process semiconductor wafers in
a controlled manner. One example of a cluster tool that is used to
deposit (i.e., coat) and develop a photoresist material is commonly
referred to as a track lithography tool.
[0005] Track lithography tools typically include a mainframe that
houses multiple chambers (which are sometimes referred to herein as
stations) dedicated to performing the various tasks associated with
pre- and post-lithography processing. There are typically both wet
and dry processing chambers within track lithography tools. Wet
chambers include coat and/or develop bowls, while dry chambers
include thermal control units that house bake and/or chill plates.
Track lithography tools also frequently include one or more
pod/cassette mounting devices, such as an industry standard FOUP
(front opening unified pod), to receive substrates from and return
substrates to the clean room, multiple substrate transfer robots to
transfer substrates between the various chambers/stations of the
track tool and an interface that allows the tool to be operatively
coupled to a lithography exposure tool in order to transfer
substrates into the exposure tool and receive substrates from the
exposure tool after the substrates are processed within the
exposure tool.
[0006] Over the years there has been a strong push within the
semiconductor industry to shrink the size of semiconductor devices.
The reduced feature sizes have caused the industry's tolerance to
process variability to shrink, which in turn, has resulted in
semiconductor manufacturing specifications having more stringent
requirements for process uniformity and repeatability. An important
factor in minimizing process variability during track lithography
processing sequences is to ensure that every substrate processed
within the track lithography tool for a particular application has
the same "wafer history." A substrate's wafer history is generally
monitored and controlled by process engineers to ensure that all of
the device fabrication processing variables that may later affect a
device's performance are controlled, so that all substrates in the
same batch are always processed the same way.
[0007] A component of the "wafer history" is the thickness,
uniformity, repeatability, and other characteristics of the
photolithography chemistry, which includes, without limitation,
photoresist, developer, and solvents. Generally, during
photolithography processes, a substrate, for example a
semiconductor wafer, is rotated on a spin chuck at predetermined
speeds while liquids and gases such as solvents, photoresist
(resist), developer, and the like are dispensed onto the surface of
the substrate. Typically, the wafer history will depend on the
process parameters associated with the photolithography
process.
[0008] As an example, the thickness of the resist layer formed
during a photolithography process is a function of the viscosity of
photoresist and the spin rate of the spin chuck among other
factors. Generally, the viscosity of the photoresist is a function
of the temperature of the resist. Therefore, to achieve uniform
wafer histories, it is generally desirable to control the resist
temperature along with other process variables.
[0009] Depending on the particular application, the desired
temperature of the resist may vary from one photoresist to another.
Therefore, there is a need in the art for improved methods and
apparatus that can provide temperature control for photolithography
chemistry at the point of dispense.
SUMMARY OF THE INVENTION
[0010] According to the present invention techniques related to the
field of substrate processing equipment are provided. More
particularly, the present invention relates to a method and
apparatus for providing point of dispense temperature control for
semiconductor process chemistry. The method and apparatus can be
applied to other processes for semiconductor substrates, for
example those used in the formation of integrated circuits.
[0011] According to an embodiment of the present invention, a point
of dispense temperature control apparatus for a track lithography
system is provided. The apparatus includes a first liquid source
characterized by a first temperature and a first flow controller
coupled to the first liquid source. The apparatus also includes a
second liquid source characterized by a second temperature and a
second flow controller coupled to the second liquid source. The
apparatus further includes a mixing element coupled to the first
flow controller and the second flow controller. The mixing element
is adapted to provide a mixed stream characterized by a total flow
volume and a temperature intermediate to the first temperature and
the second temperature. The apparatus additionally includes a
sensor coupled to the mixed stream and a point of dispense heat
exchanger coupled to the mixed stream. Furthermore, the apparatus
includes a control loop coupled to the sensor and at least one of
the first flow controller or the second-floor controller. The
control loop is adapted to provide a consistent total flow volume
at the intermediate temperature. In some embodiments, additional
valving is provided to return one or more fluids to one or more
fluid sources.
[0012] In some embodiments, the point of dispense heat exchanger is
coupled to a photolithography chemical dispense system. In a
specific embodiment, the control loop includes a
proportional-integral-derivative controller.
[0013] According to another embodiment of the present invention, a
point of dispense temperature control apparatus for a track
lithography system is provided. The apparatus includes a first
fluid source characterized by a first temperature and a first flow
regulator coupled to the first fluid source. The apparatus also
includes a second fluid source characterized by a second
temperature and a second flow regulator coupled to the second fluid
source. The apparatus further includes a mixing element coupled to
the first fluid source and the second fluid source. The mixing
element is adapted to provide a mixed stream characterized by a
temperature intermediate to the first temperature and the second
temperature. The apparatus additionally includes a sensor coupled
to the mixed stream, a point of dispense heat exchanger coupled to
the mixed stream, a fluid return path coupled to the point of
dispense heat exchanger and adapted to deliver fluid to at least
one of the first fluid source or the second fluid source, and a
control loop coupled to the sensor and at least one of the first
flow controller or the second flow controller.
[0014] In yet another embodiment according to the present
invention, a method of providing distributed temperature control
for multiple point of dispense heat exchangers in a track
lithography system is provided. The method includes providing a
first fluid stream characterized by a first temperature and
providing a second fluid stream characterized by a second
temperature. The method also includes providing a first fluid flow
path coupled to the first fluid stream and providing a second fluid
flow path coupled to the second fluid stream. The method further
includes mixing the first fluid stream and the second fluid stream
to provide a mixed fluid stream characterized by a third
temperature, monitoring the third temperature, modulating a flow
rate of at least one of the first fluid stream or the second fluid
stream in response to monitoring the third temperature, and
coupling the mixed stream to a plurality of point of dispense heat
exchangers adapted to control a temperature associated with
photolithography chemistry.
[0015] In an alternative embodiment according to the present
invention, a point of dispense temperature control apparatus for a
track lithography system is provided. The apparatus includes a
first liquid source characterized by a first temperature coupled to
a fluid line. In a particular embodiment, the first temperature is
room temperature. The apparatus also includes a second liquid
source characterized by a second temperature and a third liquid
source characterized by a third temperature. The third temperature
is less than the second temperature. The second liquid source and
the third liquid source are coupled to the fluid line. The
apparatus further includes a first flow controller coupled to the
second liquid source and a second flow controller coupled to the
third liquid source. The apparatus additionally includes a sensor
coupled to the fluid line, a point of dispense heat exchanger
coupled to the fluid line and a control loop coupled to the sensor
and at least one of the first flow controller or the second flow
controller. In some embodiments, the control loop is adapted to
provide a consistent total flow volume.
[0016] In another alternative embodiment according to the present
invention, a point of dispense temperature control apparatus for a
track lithography system is provided. The apparatus includes a
first liquid source characterized by a first temperature coupled to
a fluid line. In a particular embodiment, the first temperature is
room temperature. The apparatus also includes a second liquid
source characterized by a second temperature and a heating element,
both of which are coupled to the fluid line. The apparatus further
includes a first flow controller coupled to the second liquid
source. The apparatus additionally includes a sensor coupled to the
fluid line, a point of dispense heat exchanger coupled to the fluid
line and a control loop coupled to the sensor and at least one of
the first flow controller or the heating element. In some
embodiments, the control loop is adapted to provide a consistent
total flow volume.
[0017] Many benefits are achieved by way of the present invention
over conventional techniques. For example, embodiments of the
present invention provide for packaging of temperature control
hardware onboard the coat bowl, reducing tubing length between the
mixer and the heat exchanger, thus reducing the distance from the
temperature control hardware to the point of use. Additionally,
embodiments of the present invention provide improvements in energy
efficiency over other approaches, such as Peltier cooler systems.
Moreover, embodiments of the present invention provide simplified
temperature control systems, reducing the cost of the temperature
control system in comparison with other approaches. Depending upon
the embodiment, one or more of these benefits, as well as other
benefits, may be achieved. These and other benefits will be
described in more detail throughout the present specification and
more particularly below in conjunction with the following
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a simplified plan view of an embodiment of a track
lithography tool according to an embodiment of the present
invention;
[0019] FIG. 2 is a simplified schematic diagram illustrating a
point of dispense temperature control system according to an
embodiment of the present invention;
[0020] FIG. 3 is a simplified schematic diagram illustrating a
point of dispense temperature control system according to an
alternative embodiment of the present invention;
[0021] FIG. 4 is a simplified schematic diagram illustrating a
multiple output temperature control system according to an
embodiment of the present invention;
[0022] FIG. 5 is a simplified graph illustrating relationships
between temperature set points for the mixed flow stream and flow
rates according to an embodiment of the present invention;
[0023] FIG. 6 is a simplified schematic diagram illustrating
another temperature control system according to an embodiment of
the present invention;
[0024] FIG. 7 is a graph illustrating temperature set point change
as a function of time achieved utilizing an embodiment of the
present invention;
[0025] FIG. 8 is a graph illustrating temperature stability
achieved utilizing an embodiment of the present invention;
[0026] FIG. 9A is a simplified schematic diagram illustrating yet
another temperature control system according to an embodiment of
the present invention; and
[0027] FIG. 9B is a simplified schematic diagram illustrating
another alternative temperature control system according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0028] According to the present invention techniques related to the
field of substrate processing equipment are provided. More
particularly, the present invention relates to a method and
apparatus for providing point of dispense temperature control for
semiconductor process chemistry. The method and apparatus can be
applied to other processes for semiconductor substrates, for
example those used in the formation of integrated circuits.
[0029] FIG. 1 is a plan view of an embodiment of a track
lithography tool 100 in which the embodiments of the present
invention may be used. As illustrated in FIG. 1, track lithography
tool 100 contains a front end module 110 (sometimes referred to as
a factory interface or FI), a central module 112, and a rear module
114 (sometimes referred to as a scanner interface). Front end
module 110 generally contains one or more pod assemblies or FOUPS
(e.g., items 116A-D), a front end robot 118, and front end
processing racks 120A and 120B. The one or more pod assemblies
116A-D are generally adapted to accept one or more cassettes 130
that may contain one or more substrates or wafers, "W," that are to
be processed in track lithography tool 100.
[0030] Central module 112 generally contains a first central
processing rack 122A, a second central processing rack 122B, and a
central robot 124. Rear module 114 generally contains first and
second rear processing racks 126A and 126B and a back end robot
128. Front end robot 118 is adapted to access processing modules in
front end processing racks 120A, 120B; central robot 124 is adapted
to access processing modules in front end processing racks 120A,
120B, first central processing rack 122A, second central processing
rack 122B and/or rear processing racks 126A, 126B; and back end
robot 128 is adapted to access processing modules in the rear
processing racks 126A, 126B and in some cases exchange substrates
with a stepper/scanner 5.
[0031] The stepper/scanner 5, which may be purchased from Canon
USA, Inc. of San Jose, Calif., Nikon Precision Inc. of Belmont,
Calif., or ASML US, Inc. of Tempe Ariz., is a lithographic
projection apparatus used, for example, in the manufacture of
integrated circuits (ICs). The scanner/stepper tool 5 exposes a
photosensitive material (resist), deposited on the substrate in the
cluster tool, to some form of electromagnetic radiation to generate
a circuit pattern corresponding to an individual layer of the
integrated circuit (IC) device to be formed on the substrate
surface.
[0032] Each of the processing racks 120A, 120B; 122A, 122B and
126A, 126B contain multiple processing modules in a vertically
stacked arrangement. That is, each of the processing racks may
contain multiple stacked integrated thermal units 10, multiple
stacked coater modules 132, multiple stacked coater/developer
modules with shared dispense 134 or other modules that are adapted
to perform the various processing steps required of a track
photolithography tool. As examples, coater modules 132 may deposit
a bottom antireflective coating (BARC); coater/developer modules
134 may be used to deposit and/or develop photoresist layers and
integrated thermal units 10 may perform bake and chill operations
associated with hardening BARC and/or photoresist layers.
[0033] In one embodiment, a system controller 140 is used to
control all of the components and processes performed in the
cluster tool 100. The controller 140 is generally adapted to
communicate with the stepper/scanner 5, monitor and control aspects
of the processes performed in the cluster tool 100, and is adapted
to control all aspects of the complete substrate processing
sequence. In some instances, controller 140 works in conjunction
with other controllers, such as a post exposure bake (PEB)
controller, to control certain aspects of the processing sequence.
The controller 140, which is typically a microprocessor-based
controller, is configured to receive inputs from a user and/or
various sensors in one of the processing chambers and appropriately
control the processing chamber components in accordance with the
various inputs and software instructions retained in the
controller's memory. The controller 140 generally contains memory
and a CPU (not shown) which are utilized by the controller to
retain various programs, process the programs, and execute the
programs when necessary. The memory (not shown) is connected to the
CPU, and may be one or more of a readily available memory, such as
random access memory (RAM), read only memory (ROM), floppy disk,
hard disk, or any other form of digital storage, local or remote.
Software instructions and data can be coded and stored within the
memory for instructing the CPU. The support circuits (not shown)
are also connected to the CPU for supporting the processor in a
conventional manner. The support circuits may include cache, power
supplies, clock circuits, input/output circuitry, subsystems, and
the like all well known in the art. A program (or computer
instructions) readable by the controller 140 determines which tasks
are performable in the processing chamber(s). Preferably, the
program is software readable by the controller 140 and includes
instructions to monitor and control the process based on defined
rules and input data.
[0034] It is to be understood that embodiments of the invention are
not limited to use with a track lithography tool such as that
depicted in FIG. 1. Instead, embodiments of the invention may be
used in any track lithography tool including the many different
tool configurations described in U.S. application Ser. No.
11/112,281, entitled "Cluster Tool Architecture for Processing a
Substrate" filed on Apr. 22, 2005, which is hereby incorporated by
reference for all purposes and including configurations not
described in the above referenced application.
[0035] During photolithography processes, the temperature of the
photolithography chemistry, including both organic and inorganic
resists, developers, BARCs, TARCs, and the like is controlled to
achieve predetermined temperature set points. Generally, the
temperature set points for coat and/or develop processes range from
about 18.degree. C. to about 28.degree. C. In some embodiments
according to the present invention, the temperature set points are
maintained at a predetermined set point.+-.0.05.degree. C. In other
embodiments, the temperature set points are maintained at a
predetermined set point.+-.0.03.degree. C. at approximately
20.degree. C. In yet other embodiments, the temperature set points
are maintained at a predetermined set point.+-.0.01.degree. C. As
is well known to one of skill in the art, it is desirable to
control chemistry set points since the coat and develop properties,
as well as the process results, are functions of temperature. As
illustrated in FIG. 1, coater modules 132 and 134 generally contain
multiple fluid source assemblies 260 and 262 to run different
process recipes containing different materials. These materials
include, but are not limited to, photoresists, developers, BARCs,
TARCs, ARCs, and the like.
[0036] Accordingly, the temperature of the fluid source assemblies
are each independently controlled to assure consistency in
achieving desirable process results. Embodiments of the invention
provide various methods and apparatus for controlling the
temperature of photoresist as well as other fluids utilized in
photolithography chemistries before the fluids are dispensed on the
surface of a substrate during a coat and/or develop process. In
some embodiments, the temperature control for develop chemistries
is preferably about.+-.0.1.degree. C. In other embodiments, the
temperature control for develop chemistries is preferably
about.+-.0.2.degree. C.
[0037] FIG. 2 is a simplified schematic diagram illustrating a
point of dispense temperature control system according to an
embodiment of the present invention. A hot stream source 210 and a
cold stream source 220 are provided according to embodiments of the
present invention as illustrated in FIG. 2. Fluid at a temperature
T.sub.H is sourced from the hot stream source 210 into source line
212 and the flow rate of the fluid in line 212 is controlled using
flow control valve 214. According to some embodiments, the
temperature of the fluid provided by the hot stream source is a
predetermined value. Merely by way of example, in some embodiments,
the temperature of the hot stream source ranges from about
25.degree. C. to about 60.degree. C. In a specific embodiment, the
temperature of the hot stream source is 30.degree. C. Likewise,
according to some embodiments, the temperature of the fluid
provided by the cold stream source is a predetermined value. Merely
by way of example, in some embodiments, the temperature of the cold
stream source ranges from about 5 to about 25.degree. C. In a
specific embodiment, the temperature of the cold stream source is
18.degree. C.
[0038] By way of example, embodiments of the present invention are
utilized in conjunction with heat exchanging devices such as those
described in commonly owned and assigned U.S. patent application
Ser. No. 11/112,281, referenced above. For example, discharge
nozzles containing heat exchanging devices that are adapted to heat
and/or cool the nozzle body, the supply tube, and the processing
fluid contained in the supply tube, for instance, photoresist, are
described in the above referenced application. According to
embodiments of the present invention, temperature controlled fluids
are provided that are utilized in such heat exchanger applications.
For example, in some embodiment, de-ionized (DI) water,
de-mineralized (DM) water, DI water/ethylene glycol mixtures, DI
water with anti-corrosive additives, DI water with anti-bacterial
additives, combinations of these, and the like are utilized as
fluids for the hot and/or cold sources. One of ordinary skill in
the art would recognize many variations, modifications, and
alternatives.
[0039] In a particular embodiment of the present invention, source
line 212 is a fluid line with a predetermined inside diameter (ID).
Merely by way of example, in an embodiment, source line 212 has a
1/4'' ID. In alternative embodiments, the ID of source line 212
varies with flow rate over a range from about 1/16'' to about 1''.
Moreover, in some embodiments of the present invention, the flow
rate of the fluid at temperature T.sub.H is set at a predetermined
value, such as X liters per minute (lpm). Merely by way of example,
the flow rate for the hot stream is about 1 lpm in some embodiments
of the present invention. In alternative embodiments, the flow rate
for the hot stream ranges from about 0.1 lpm to about 3 lpm.
[0040] Cold stream source 220 provides a source of fluid at
temperature T.sub.C into source line 222. In a particular
embodiment of the present invention, source line 222 is a fluid
line with a predetermined ID. Merely by way of example, in an
embodiment, source line 222 has a 1/4'' ID. In alternative
embodiments, the ID of source line 222 varies over a range from
about 1/16'' to about 1''. In some embodiments, the hot stream
source 210 and the cold stream source 220 are packaged in a single
unit. One of ordinary skill in the art would recognize many
variations, modifications, and alternatives.
[0041] Mixer 216 is illustrated in FIG. 2 as a junction point at
which the fluid in the hot stream 212 and the cold stream 222 are
combined to form a mixed stream in fluid line 226. As will be
evident to one of skill in the art, mixer 216 may be a "T" junction
or other suitable flow combiner. As illustrated in FIG. 2, the
mixed stream in fluid line 226 is at a temperature T.sub.M greater
than T.sub.C and less than T.sub.H. The temperature T.sub.M is a
function of the flow rates of the hot and cold streams as well as
the temperatures of these streams. Accordingly, a sensor 228 and
controller 230 are provided according to embodiments of the present
invention to achieve the desired temperature T.sub.M for the mixed
stream 226.
[0042] According to a particular embodiment of the present
invention, a resistance temperature detector (RTD) sensor 228 is
utilized to measure the temperature of the fluid flowing in the
mixed stream 226. As is well known to one of skill in the art, the
electrical resistivity of metals changes with temperature.
Therefore, RTDs provide a resistance element for which the
resistance is calibrated as a function of temperature. Embodiments
of the present invention not limited to RTDs, as other temperature
sensors are included within the scope of the present invention. In
an embodiment, a proportional-integral-derivative (PID) controller
230 is coupled to the temperature sensor 228 and to flow control
valve 224 in a feedback loop. Based on the temperature measurement
provided by sensor 228, controller 230 modifies the flow rate
through fluid line 222. Thus, the temperature of the mixed stream
is controlled at T.sub.M according to embodiments of the present
invention. Embodiments of the present invention are not limited to
PID controllers, as other suitable controllers are included within
the scope of the present invention.
[0043] In an embodiment according to the present invention, the
flow rate of the hot stream is maintained at a constant value
selected to provide temperature control for chemistry through a
heat exchanger at the point of dispense. As will be evident to one
of skill in the art, the flow rate through the point of dispense
heat exchanger will be a function of the particular heat exchanger
design. Coarse adjustment of the temperature T.sub.M of the mixed
stream is provided in the embodiment illustrated in FIG. 2 by
adjusting the temperature set point T.sub.H of the hot stream. In
an alternative embodiment, coarse adjustment of the temperature
T.sub.M is provided by adjusting the flow rate of the hot stream or
combinations of the temperature and flow rate. One of ordinary
skill in the art would recognize many variations, modifications,
and alternatives. Fine adjustment of the temperature of the mixed
stream is provided by the feedback loop including the controller
230, thereby varying the flow rate of the cold stream.
[0044] Flow control valve 240 is utilized to control the flow rate
of fluid to point of dispense heat exchanger 242 and the return to
the hot stream source 210. In a particular embodiment according to
the present invention, flow control valve 240 is adjusted to
provide a flow rate to the point of dispense heat exchanger
substantially equal to the flow rate in fluid line 212, namely X
lpm. Accordingly, the flows sourced by and returned to the hot
stream source 210 are equal. In some embodiments, substantially
equal flow rates include flow rates in which the flow rate in fluid
line 212 is within 90% of the flow rate in the return line to the
hot stream source. In other embodiments, substantially equal flow
rates include flow rates in which the flow rate in fluid line 212
is within 95%, 97% or 99% of the flow rate in the return line to
the hot stream source. Fluid from the mixed stream not returned to
the hot stream source is returned to the cold stream source through
fluid line 244. In some embodiments, an additional flow control
valve 246 is utilized to control the flow of fluid in cold stream
return line 244.
[0045] Although FIG. 2 illustrates the use of flow control valves
to regulate the flow in lines 212, 222, and the hot and cold return
lines, this is not required by the present invention. In
alternative embodiments, other flow control mechanisms are utilized
including pressure regulators that pressure balance lines 212 and
222. Merely by way of example, flow restrictors including valves,
orifices, and the like are utilized according to embodiments of the
present invention. One of ordinary skill in the art would recognize
many variations, modifications, and alternatives.
[0046] According to embodiments of the present invention, the point
of dispense heat exchanger 242 is coupled to fluid lines associated
with the photolithography chemistry. As an example, the point of
dispense heat exchanger is coupled to a photoresist line in a
particular embodiment. By providing a heat exchanger at the point
of dispense, variations in chemistry temperatures as the various
fluids travel through delivery paths are minimized. Therefore, the
temperature of the photoresist, solvents, developers, and the like
is controlled to achieve desired process control, uniformity, and
repeatability.
[0047] FIG. 3 is a simplified schematic diagram illustrating a
point of dispense temperature control system according to an
alternative embodiment of the present invention. Hot stream source
310 and cold stream source 330 are provided as illustrated in FIG.
3. As illustrated in FIG. 3, hot stream source 310 and cold stream
source 330 are combined in a single unit 305. Fluid at temperature
T.sub.H is sourced from the hot stream source 310 in a manner
similar to that as illustrated in FIG. 2. Pressure regulator 312 is
utilized to control the flow through fluid line 314. In some
embodiments, pressure regulator 312 is replaced by a variable rate
flow control valve.
[0048] Flow monitor 316 is coupled to the fluid line 314 to monitor
the flow rate through the line. In an embodiment according to the
present invention, a rotameter available from Omega Engineering,
Inc. of Stamford, Conn. is utilized for this flow monitoring
function. In some embodiments, the flow rate through line 314 is a
predetermined amount of about 1 lpm. In alternative embodiments,
the flow rate ranges from about 0.1 lpm to about 3 lpm. Monitoring
RTD 318 along with a check valve (not shown) is coupled to the line
314 downstream of the flow monitor 316. As will be evident to one
of skill in the art, the use of a check valve prevents back stream
flow in line 314.
[0049] Cold stream source 330 provides a source of fluid at
temperature T.sub.C into source line 332. Dome regulator 348,
needle valve 334, RTD 336, and a check valve(not shown) are coupled
to cold stream line 332 as illustrated in FIG. 3. The hot stream
and the cold stream are mixed at the junction of the hot and cold
streams and mixed in a mixer 340. As illustrated in FIG. 3, a mixed
stream flows in the fluid line downstream of the mixer at a
temperature T.sub.M greater than T.sub.C and less than T.sub.H. The
intermediate temperature T.sub.M is a function of the flow rates of
the hot and cold streams as well as the temperatures of the
streams.
[0050] As illustrated in FIG. 3, in some embodiments of the present
invention, a temperature sensor, such as an RTD sensor 342, is
utilized to measure the temperature of the fluid flowing in the
mixed stream. Embodiments of the present invention not limited to
RTDs, as other temperature sensors are included within the scope of
the present invention. As further illustrated in FIG. 3, a
controller 344 and a signal converter 346 are coupled to the sensor
342 and the dome regulator 348 in a feedback loop. In an
embodiment, a PID controller 344 is utilized to provide feedback
and control signals for the temperature control system. Moreover,
an electro-pneumatic regulator, such as an ITV regulator 346
available from SMC Corporation of America of Indianapolis, Ind.,
which controls air pressure in proportion to an electrical signal
is illustrated in FIG. 3. Thus, electrical signals provided by the
controller 344 are converted to pneumatic signals by the converter
346. The pneumatic signals are utilized in turn to regulate the
flow of the cold stream through dome regulator 348. Therefore,
based on the temperature measurement provided by sensor 342,
controller 344 and signal converter 346 modify the flow rate
through fluid line 332.
[0051] In the embodiment according to the present invention
illustrated in FIG. 3, the flow rate of the hot stream is monitored
and regulated prior to mixing with the cold stream. Feedback from
the mixed stream line is utilized to regulate the flow in the cold
stream line, thereby controlling the temperature of the mixed
stream. The point of dispense heat exchanger is utilized to
regulate the temperature of various photolithography chemistry
fluids as described above. Generally, coarse adjustment of the
temperature T.sub.M of the mixed stream is provided by adjusting
the temperature set point T.sub.H, the flow rate of the hot stream,
and/or combinations thereof. Fine adjustment of the temperature of
the mixed stream is provided by the feedback loop regulating the
flow rate in the cold stream line. After passing through the point
of dispense heat exchanger 350, the mixed stream returns to the
source unit 305 through the illustrated fluid lines. Variable rate
flow control valves 352 and 354 are utilized in the embodiment
illustrated in FIG. 3 to control the flow rates of the mixed stream
in the return paths to the fluid source.
[0052] As will be evident, in alternative embodiments the flow rate
of the hot stream is monitored and regulated by a feedback loop. In
this alternative embodiment, fine adjustment of the temperature of
the mixed stream is provided by the feedback loop regulating the
flow rate in the hot stream. In yet other alternative embodiments,
a control loop coupled to both the cold stream flow regulator and
the hot stream flow regulator is utilized. One of ordinary skill in
the art would recognize many variations, modifications, and
alternatives.
[0053] According to some embodiments of the present invention, the
total flow in the mixed stream is regulated through the use of the
variable flow control valves illustrated in FIG. 3 to maintain a
consistent total flow through the point of dispense heat exchanger.
Provision of a consistent total flow rate is accomplished in a
specific embodiment by referencing the temperature and flow rate of
the hot stream and adjusting the cold stream flow in response to
these measurements. In another specific embodiment, the temperature
and flow rate of the cold stream are referenced. In other
embodiments, the hot and cold streams are pressure balanced to
provide a consistent total flow rate. In embodiments of the present
invention, a consistent or constant flow rate is provided for a
predetermined time, for example, during a series of dispense
operations. A constant flow rate is defined in some embodiments by
a flow rate varying less than 10% during the predetermined period.
In other embodiments, a constant flow rate is defined by a
variation of less than 5%, less than 3%, or less than 1%.
[0054] FIG. 4 is a simplified schematic diagram illustrating a
multiple output temperature control system according to an
embodiment of the present invention. As illustrated in FIG. 4, hot
stream source 410 and cold stream source 420 are coupled to a
number of distributed point of dispense heat exchangers (PDHX) PDHX
1 through PDHX n. Accordingly, multiple branches are provided
utilizing common system components, reducing system costs and
complexity while providing independently controlled point of
dispense heat exchangers adapted to provide different temperature
set points. The point of dispense temperature control systems
illustrated in FIGS. 2 and 3, as well as other configurations, are
thereby operated in parallel as illustrated in FIG. 4. Accordingly,
embodiments of the present invention provide for multiple
independent point of dispense temperature control systems operating
at predetermined temperatures.
[0055] In some embodiments of the present invention, a first number
of chemical delivery nozzles are provided in a second number of
groupings, each of the first number of chemical delivery nozzles
coupled to a point of dispense heat exchanger. In a specific
embodiment, four groups of three nozzles are provided for dispense
of resist and other coating liquids. Each of the groups of nozzles
is coupled to a point of dispense heat exchanger operated at a set
point temperature. Thus, three nozzles are maintained at a first
temperature, three other nozzles are maintained at a second
temperature, etc. Utilizing the embodiments of the present
invention illustrated in FIGS. 2 and 3, the first temperature may
be maintained at a different temperature than the second
temperature.
[0056] FIG. 5 is a simplified graph illustrating relationships
between temperature set points for the mixed flow stream and flow
rates according to an embodiment of the present invention. In FIG.
5, the flow rate of the hot and cold flows measured in liters per
minute (lpm) is plotted on the left y-axis and the set point
temperatures of the hot and cold flows in degrees Centigrade are
plotted on the right y-axis. Thus, as illustrated in FIG. 5, the
hot flow set point is set at 30.degree. C. and the cold flow set
point is set at 16.degree. C. For these predetermined set points,
the flow rate of the hot and cold flows can be determined as a
function of the final temperature set point for the mixed stream in
degrees Centigrade, which is plotted along the lower x-axis, titled
"Mixed Flow Set Point."
[0057] As an example, to obtain a final temperature set point for
the mixed stream of 21.degree. C., a flow rate of about 0.7 lpm for
the hot flow (reference A on the left y-axis of FIG. 5) and a flow
rate of about 1.3 lpm for the cold flow (reference B) are utilized.
At the intersection of the hot and cold flow rates, a temperature
of 23.degree. C. (equal to the average of 16 and 30) is obtained
for equal hot and cold flow rates of 1.0 lpm. This set point is
illustrated by dashed line C in FIG. 5. As will be evident to one
of skill in the art, similar charts may be produced as a function
of the hot and cold flow set points and flow rates.
[0058] FIG. 6 is a simplified schematic diagram illustrating
another temperature control system according to an embodiment of
the present invention. As illustrated in FIG. 6, a first flow
controller 610 is coupled to a hot water line 616. Under control of
RTD 622, and control loop 630, the first flow controller 610 is
operable to modulate the flow of fluid in hot water line 616. A
second flow controller 612 is coupled to a cold water line 614. In
the embodiment illustrated in FIG. 6, the second flow controller
612 is maintained at a constant flow rate set point. As described
below, set points of 1.0, 1.5, and 2.0 lpm, providing a constant
flow rate in cold water line 614, are provided in some embodiments.
As will be evident to one of skill in the art, the selection of the
cold water line 614 as the constant flow source is not required
according to embodiments of the present invention. One of ordinary
skill in the art would recognize many variations, modifications,
and alternatives.
[0059] Hot water line 616 and cold water line 614 are joined prior
to their combined flow entering static mixer 620. An RTD 622 is
coupled to the output of a first static mixer 620. The output of
the RTD 622 is fed back to flow controller 610 via control loop
630. After passing through RTD 622, the combined flow passes
through a second static mixer 624. RTD 626 is coupled to the output
of the second static mixer 624. The output of RTD 626 is provided
to a data acquisition system (not shown) for data collection and
analysis.
[0060] FIG. 7 is a graph illustrating temperature set point change
as a function of time achieved utilizing an embodiment of the
present invention. As illustrated in FIG. 7, the apparatus
illustrated in FIG. 6 is utilized to generate a series of
temperature set points. The data presented in FIG. 7 was collected
at the second RTD 622 as illustrated in FIG. 6. In the embodiment
illustrated in FIG. 7, set points at 20.degree. C., 22.degree. C.,
24.degree. C., 26.degree. C., 28.degree. C., and 30.degree. C. are
demonstrated as a function of time. Referring to FIG. 7, each of
the set points listed above are maintained for a time period of
approximately 20 seconds. Temperature set points are demonstrated
in the figure for a single flow rate for the cold stream of 1.0
lpm, although other flow rates (e.g. 1.5 lpm and 2.0 lpm) are
included in alternative embodiments of the present invention.
[0061] As illustrated in FIG. 7, embodiments of the present
invention provide for controllable and stable set points for point
of dispense heat exchangers. Embodiments of the present invention
are thus useful to regulate the temperature of photolithography
chemicals, such as resist. As will be evident to one of skill in
the art, the regulation of these temperatures will provide for
uniform wafer histories and repeatable coating and dispense
operations.
[0062] FIG. 8 is a graph illustrating temperature stability
achieved utilizing an embodiment of the present invention. In FIG.
8, the temperature of the mixed stream measured at RTD 626 is
plotted as a function of time. For reference, boundaries associated
with.+-.3.sigma., calculated based on data collected using the
system illustrated in FIG. 6, are illustrated in FIG. 8 at about
19.99.degree. C. and 20.05.degree. C. The flow rate of the cold
stream was set at 1.0 lpm during the collection of the data
illustrated in FIG. 8. The temperature of the mixed stream varies
from about 20.03.degree. C. to about 20.00.degree. C., exhibiting a
variation of about 0.03.degree. C. at a set point temperature of
about 20.degree. C., well within the.+-.3.sigma. variation
limits.
[0063] FIG. 9A is a simplified schematic diagram illustrating yet
another temperature control system according to an embodiment of
the present invention. A source of fluid 910, water in some
embodiments, is provided at a predetermined temperature. Generally,
the predetermined temperature is room temperature, e.g., 20.degree.
C.-25.degree. C. For purposes of clarity flow and pressure control
apparatus associated with the room temperature source 910 are not
illustrated in FIG. 9A. In alternative embodiments, the temperature
of source 910 is selected to provide a temperature approximately
equal to the average dispense temperature of the photolithography
chemicals, thus reducing operating costs.
[0064] A source of hot fluid 912 and a source of cold fluid 914 are
provided and connected to the output of the room temperature source
910. As illustrated in FIG. 9A, flow control valves 916 and 918 are
utilized to modulate the flow of fluids from the hot source and the
cold source, respectively. Controlled amounts of the hot and cold
fluids are delivered to the fluid line coupled to temperature
sensor 920. In some embodiments, the temperature sensor is an RTD
or other suitable sensor. A control system, not shown, utilizes
measurements of the fluid temperature at the temperature sensor 920
to control the flow through valves 916 and 918, providing the
desired temperature fluid to the point of dispense heat exchanger
922.
[0065] In some embodiments of the present invention utilizing the
temperature control system illustrated in FIG. 9A, a fluid return
path is provided for the fluid passing through the point of
dispense heat exchanger 922. In alternative embodiments, the
temperature control system does not recycle the temperature control
fluid, but utilizes a single pass system. One of ordinary skill in
the art would recognize many variations, modifications, and
alternatives.
[0066] FIG. 9B is a simplified schematic diagram illustrating
another alternative temperature control system according to an
embodiment of the present invention. A source of fluid 950, water
in some embodiments, is provided at a predetermined temperature.
Generally, the predetermined temperature is room temperature, e.g.,
20.degree. C.-25.degree. C. In alternative embodiments, the
temperature of source 950 is selected to provide a temperature
approximately equal to the average dispense temperature of the
photolithography chemicals, thus reducing operating costs.
[0067] A source of cold fluid 952 is provided and connected to the
output of the room temperature source 950. As illustrated in FIG.
9B, flow control valve 954 is utilized to modulate the flow of
fluid from the cold source. Controlled amounts of the cold fluid is
delivered to the fluid line coupled to the room temperature source.
Additionally, a heating element 956 is coupled to the mixed stream
formed by the room temperature source 950 and cold source 952. In
some embodiments, the heating element 956 is a resistive heater
adapted to raise the temperature of the fluid passing through line
958 by approximately 2-5.degree. C. A control system, not shown,
utilizes measurements of the fluid temperature at the temperature
sensor 960 to control the flow through valve 954 and/or the
operation of heating element 956, thereby providing the desired
temperature fluid to a point of dispense heat exchanger (not
shown). The cold source is positioned after the heating element in
alternative embodiments.
[0068] In some embodiments of the present invention utilizing the
temperature control system illustrated in FIG. 9B, a fluid return
path is provided for the fluid passing through the point of
dispense heat exchanger connected to fluid line 958. In alternative
embodiments, the temperature control system does not recycle the
temperature control fluid, but utilizes a single pass system. One
of ordinary skill in the art would recognize many variations,
modifications, and alternatives.
[0069] While the present invention has been described with respect
to particular embodiments and specific examples thereof, it should
be understood that other embodiments may fall within the spirit and
scope of the invention. The scope of the invention should,
therefore, be determined with reference to the appended claims
along with their full scope of equivalents.
* * * * *