U.S. patent application number 17/174898 was filed with the patent office on 2022-08-04 for system, apparatus, and method for improving photoresist coating operations.
The applicant listed for this patent is TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY, LTD., TSMC NANJING COMPANY, LIMITED. Invention is credited to Chun-Ming CHEN, Chien-Liang LIN, Jen-Yu TSAI, Chun-Hsiang WANG.
Application Number | 20220246426 17/174898 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-04 |
United States Patent
Application |
20220246426 |
Kind Code |
A1 |
CHEN; Chun-Ming ; et
al. |
August 4, 2022 |
SYSTEM, APPARATUS, AND METHOD FOR IMPROVING PHOTORESIST COATING
OPERATIONS
Abstract
A coating system comprising a vessel, a flexible container
within the vessel, and a coating apparatus. The flexible container
including an outlet port, wherein the flexible container is
configured to contract in response to an increase in pressure
within the vessel. The flexible container is configured to output a
coating composition through the outlet port in response to
contraction. The coating apparatus is configured to receive the
coating composition from the outlet port.
Inventors: |
CHEN; Chun-Ming; (Hsinchu,
TW) ; LIN; Chien-Liang; (Hsinchu, TW) ; WANG;
Chun-Hsiang; (Hsinchu, TW) ; TSAI; Jen-Yu;
(Hsinchu, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY, LTD.
TSMC NANJING COMPANY, LIMITED |
Hsinchu
Nanjing |
|
TW
CN |
|
|
Appl. No.: |
17/174898 |
Filed: |
February 12, 2021 |
International
Class: |
H01L 21/027 20060101
H01L021/027; H01L 21/67 20060101 H01L021/67 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 2021 |
CN |
202110142399.7 |
Claims
1. A coating system comprising: a vessel; a flexible container
within the vessel, the flexible container including an outlet port,
wherein the flexible container is configured to contract in
response to an increase in pressure within the vessel, and the
flexible container is configured to output a coating composition
through the outlet port in response to contraction; and a coating
apparatus for receiving the coating composition from the outlet
port.
2. The coating system according to claim 1, wherein: the coating
composition is a photoresist.
3. The coating system according to claim 1, further comprising: an
intermediate reservoir containing a first volume of the coating
composition, wherein a second volume of the coating composition is
applied to a substrate, a ratio between the first volume and the
second volume being at least 5:1.
4. The coating system according to claim 1, further comprising: a
controller for controlling the pressure within the vessel.
5. The coating system according to claim 1, further comprising: a
filter between the flexible container and a dispensing nozzle.
6. The coating system according to claim 5, further comprising: a
secondary reservoir between the flexible container and the
dispensing nozzle, the secondary reservoir being sized to receive a
first volume of the coating composition.
7. The coating system according to claim 1, wherein: the flexible
container comprises a reinforced region, the reinforced region
having an interior surface area and being connected to a first
attachment apparatus.
8. The coating system according to claim 7, wherein: the flexible
container comprises: a flexible region, the flexible region having
a variable interior surface area and being connected to the
reinforced region, and wherein the interior surfaces of the
reinforced region, the flexible region, and the first attachment
apparatus define a variable container volume.
9. The coating system according to claim 7, wherein: the first
attachment apparatus further comprises an inlet port.
10. The coating system according to claim 9, wherein: the outlet
port has a first configuration operable for establishing a fluidic
connection with an outlet line; and the inlet port has a second
configuration operable for preventing the establishment of a
fluidic connection to the outlet line.
11. A method of coating a substrate comprising: introducing a
pressurized gas into a pressurized volume defined between an
exterior surface of a flexible container and an interior surface of
a pressure vessel, wherein the pressurized gas forces a coating
composition out of the flexible container and through an outlet
port; and applying the coating composition to a substrate.
12. The method of coating according to claim 11, further
comprising: arranging the flexible container within the pressure
vessel, wherein the flexible container contains an initial volume
of the coating composition; and engaging a first attachment
assembly on the flexible container with a second attachment
assembly on the pressure vessel to form a temporary attachment and
define an initial pressurized volume.
13. The method of coating according to claim 11, further
comprising: monitoring a pressure (Pv) within the pressurized
volume; and controlling a flowrate at which additional pressurized
gas is introduced into the pressurized volume to maintain an
operational pressure between a Target Pressure Low (TPL) and a
Target Pressure High (TPH).
14. The method of coating according to claim 11, further
comprising: monitoring a first flowrate of photoresist into an
intermediate reservoir; and controlling a second flowrate at which
the pressurized gas is introduced into the pressurized volume to
maintain the first flowrate between a lower Target Flowrate Low
(TFL) and a higher Target Flowrate High (TFH).
15. The method of coating according to claim 11, further
comprising: isolating the first volume of the coating composition
within an intermediate reservoir; reducing the pressure applied to
the first volume of the coating composition to a pressure below 1
atm for a treatment period to obtain a degassed coating
composition; and releasing the degassed coating composition from
the intermediate reservoir for application to the substrate.
16. The method of coating according to claim 11, further
comprising: preparing a unitary assembly comprising the flexible
container and the pressure vessel; connecting the pressurized gas
to a port provided on the pressure vessel; and connecting the
outlet port to an outlet line.
17. The method of coating according to claim 11, further
comprising: isolating the first volume of the coating composition
within an intermediate reservoir; monitoring a temperature Tv of
the first volume of the coating composition; adjusting the
temperature Tv of the first volume of the coating composition to
obtain a coating composition viscosity within a predetermined
viscosity range; and releasing the adjusted first volume of the
coating composition from the intermediate reservoir for application
to the substrate, wherein the coating composition is
photoresist.
18. A method of preparing a coating composition comprising:
maintaining a coating composition under a vacuum for a treatment
period to reduce by at least 20% a volume of gas dissolved in the
coating composition to obtain a treated coating composition;
introducing a first volume of the treated coating composition into
a flexible container.
19. The method of preparing a coating composition according to
claim 18, comprising: warming the coating composition during the
treatment period to a treatment temperature to reduce a gas
solubility by at least 20% for at least one gas selected from the
group consisting of N2, O2, CO2, and mixtures thereof.
20. The method of preparing a coating composition according to
claim 18, comprising: evacuating a residual gas from the flexible
container; and introducing a second volume of the treated coating
composition into the flexible container to generate a purge stream
of the treated coating composition through the outlet port.
Description
BACKGROUND
[0001] Uniformity and quality of photoresist layers used in the
manufacture of semiconductor devices is a factor in determining
overall yield of the manufacturing process. Some methods and
systems for dispensing photoresist have relied on pressurizing the
headspace above a quantity of photoresist within a sealed
container, typically by introducing compressed nitrogen from a line
or tank, to force the photoresist out of the container and into a
lower pressure outlet line. One or more filters, vibrators, traps
and/or other treatment elements are utilized downstream of the
photoresist container for removing or reducing the particulate
and/or bubble content of the photoresist composition stream before
the photoresist composition is dispensed onto a semiconductor
substrate surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0003] FIG. 1 is a schematic view of a photoresist dispensing
system in accordance with some embodiments.
[0004] FIG. 2 is a schematic view of a photoresist dispensing
system in accordance with some embodiments.
[0005] FIG. 3 is a schematic view of a process control system
useful in the operation of photoresist dispensing systems in
accordance with some embodiments.
[0006] FIGS. 4A and 4B are schematic views of a photoresist
container according to some embodiments.
[0007] FIGS. 5A and 5B are schematic views of a photoresist
container according to some embodiments.
[0008] FIG. 6 is a flow chart of a method for preparing a flexible
photoresist container in accordance with some embodiments.
[0009] FIG. 7 is a schematic view of an electronic process control
(EPC) system useful in the operation of photoresist dispensing
systems in accordance with some embodiments.
DETAILED DESCRIPTION
[0010] This description of the exemplary embodiments is intended to
be read in connection with the accompanying drawings, which are to
be considered part of the entire written description. The following
disclosure provides many different embodiments, or examples, for
implementing different features of the provided subject matter.
Specific examples of components, values, operations, materials,
arrangements, or the like, are described below to simplify the
present disclosure. These are, of course, merely examples and are
not intended to be limiting. Other components, values, operations,
materials, arrangements, or the like, are contemplated. For
example, the formation of a first feature over or on a second
feature in the description that follows may include embodiments in
which the first and second features are formed in direct contact,
and may also include embodiments in which additional features may
be formed between the first and second features, such that the
first and second features may not be in direct contact. In
addition, the present disclosure may repeat reference numerals
and/or letters in the various examples. This repetition is for the
purpose of simplicity and clarity and does not in itself dictate a
relationship between the various embodiments and/or configurations
discussed.
[0011] Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. The spatially relative terms are intended to encompass
different orientations of the device in use or operation in
addition to the orientation depicted in the figures. The apparatus
may be otherwise oriented (rotated 90 degrees or at other
orientations) and the spatially relative descriptors used herein
may likewise be interpreted accordingly.
[0012] For example, a description of the placement of a first
element before or after a second element along a coating
composition flow path within a coating apparatus should be
understood to include embodiments in which the placement of the
first and second elements are reversed and/or interspersed with
other functional elements as long as the effect(s) and/or
function(s) associated with the first and second elements are
substantially retained in the alternative configurations.
[0013] Holding volumes of the photoresist compositions in a
container under pressurized gas, however, tends to increase the gas
content of the pressurized photoresist. As a result, when the
pressurized photoresist is dispensed onto the substrate and exposed
to atmospheric pressure, the reduced pressure reduces the
solubility of the gases dissolved in the photoresist composition.
If the solubility of the gases was reduced below the actual
dissolved gas content within the photoresist composition, the
excess gas tends to form bubbles in the photoresist at the point of
application. Further, because the residence time of the photoresist
composition under the pressurized gas and the relative quantities
of pressurized gas and the photoresist composition could vary
widely, the amount of dissolved gas(es) also varies widely.
[0014] In addition to the increase in the volume of dissolved
gas(es) resulting from holding the photoresist under pressure, the
gas(es) used to establish and maintain the pressure in the
photoresist container potentially introduce other contaminants in
the form of particles and/or moisture. Further, a loss of positive
pressure within the photoresist container potentially allows the
ambient gases present in the clean room to be pulled into the
photoresist container and any photoresist residing therein. FIG. 1
is a schematic diagram of a photoresist dispensing system 100 in
accordance with some embodiments. The photoresist dispensing system
100 includes a pressurized gas source 102, that is connected
through a control valve 104 to a pressure vessel 106 for providing
pressurized gas (such as air, O2, N2, other gas or gas mixture) to
an internal volume 108 defined by the pressure vessel 106. A
flexible photoresist container 110, a non-limiting embodiment of
which is described below with reference to FIGS. 4A-B is arranged
within the pressure vessel whereby the pressurized gas within the
pressure vessel will compress the flexible photoresist container
110 to force a quantity of photoresist into outlet line 112. In
some embodiments, the outlet line will include one or more check
valves 114 for maintaining a single flow direction for the
photoresist, one or more filters (not shown), trap or mini-trap
(not shown) and/or a control valve 116.
[0015] In FIG. 1, in some embodiments, the photoresist flowing
through the outlet line 112 is used to fill, at least partially, an
intermediate photoresist reservoir 118 with a first volume of
photoresist for coating a plurality of semiconductor substrates. In
some embodiments, the intermediate photoresist reservoir 118 is
provided with a heat exchanger 117 and/or a pump 119 for use in
controlling the temperature of the photoresist and/or the pressure
applied to the photoresist within intermediate photoresist
reservoir 118. From the intermediate reservoir, the photoresist
will pass through a metered pump 120, one or more control valves
122, and/or one or more filters 124 to reach the dispensing nozzle
126. In some embodiments, one or more of the metered pump 120, the
one or more control valves 122, and/or the one or more filters 124
are omitted.
[0016] A second volume of the photoresist is then dispensed through
the dispensing nozzle 126 as a stream or spray 128 onto the surface
of a semiconductor substrate 132 to form, in combination with
lateral and/or arcuate movement of the dispensing nozzle and/or
lateral and/or rotational movement of the chuck 134, a photoresist
film 130. In some embodiments, a ratio between the first volume of
photoresist and the second volume of photoresist will be at least
5:1 so that the intermediate photoresist reservoir 118 contains
enough photoresist to coat several semiconductor substrates 132
without needing to be replenished from the volume of photoresist
maintained within the flexible photoresist container 110. In some
embodiments, the chuck 134 includes a heat exchanger 136, the heat
exchanger 136 being arranged and configured for controlling a chuck
temperature. As will be appreciated, in some embodiments the
dispensing operation also includes the application of one or more
solvents and/or solutions to the bare substrate surface and/or to a
quantity of previously dispensed photoresist in order to obtain a
photoresist film having the desired qualities.
[0017] Accordingly, embodiments of photoresist dispensing system
100 according to FIG. 1 allow for the pressurization of the
photoresist without allowing direct contact between the photoresist
and the pressurized gas. By avoiding direct contact between the
photoresist and the pressurized gas, the quantity of gas dissolved
in the photoresist, if any, does not increase over time; and
variations in the dissolved gas content within the photoresist are
reduced or avoided. By avoiding the introduction of additional
dissolved gas into the photoresist, the formation of bubbles
resulting from outgas sing when the pressure applied to the
photoresist is released during the application process is reduced
or eliminated. By reducing or eliminating bubble formation within
the photoresist layer, the photoresist dispensing systems according
to FIG. 1 provide improved uniformity of the resulting photoresist
layer. Further, by isolating the photoresist from the interior of
the pressure vessel, the photoresist dispensing system according to
FIG. 1 reduces the likelihood of contamination being introduced
into the photoresist if the pressure vessel were to lose positive
pressure relative to the fabrication area in which the photoresist
dispensing system is housed. FIG. 2 is a schematic diagram of a
photoresist dispensing system 200 in accordance with some
embodiments. The photoresist dispensing system 200 includes a
pressurized gas source 202 that is monitored by a pressure sensor
202P and that is connected through a control valve 204 and a
flowmeter 202F to a pressure vessel 206 for providing pressurized
gas (such as N2 or other gas) to an internal volume 208 defined by
the pressure vessel and monitored by a pressure sensor 208P.
[0018] A flexible photoresist container 210 is arranged within the
pressure vessel 206 whereby the pressurized gas within the pressure
vessel will tend to compress the sides of the flexible photoresist
container 210 to force a quantity of photoresist into outlet line
212. The condition of the photoresist maintained within the
flexible photoresist container 210 is monitored by a temperature
sensor 210T and/or a pressure sensor (not shown). The outlet line
212 includes one or more check valves 214 for maintaining a single
flow direction for the photoresist, one or more filters (not
shown), trap or mini-trap (not shown), a flowmeter 212F, and/or a
control valve 216. In one or more embodiments, the outlet line 212
omits one or more of the one or more check valves 214, the one or
more filters, trap, or mini-trap and/or the control valve 216.
[0019] In FIG. 2, in some embodiments the photoresist flowing
through the outlet line 212 is used to fill, at least partially, an
intermediate photoresist reservoir 218 with a first volume of
photoresist that is sized for coating one or more semiconductor
substrates 232 with a second volume of photoresist. In some
embodiments, a ratio between the first volume and the second volume
will be at least 5:1 so that the intermediate photoresist reservoir
218 contains enough photoresist for coating several wafers 232
without needing to be replenished. The intermediate photoresist
reservoir 218 is provided with a heat exchanger 217 and/or a pump
219 for use in controlling the temperature of the photoresist
and/or the pressure applied to the photoresist within intermediate
photoresist reservoir 218. In some embodiments, heat exchanger 217
and/or pump 219 are omitted from intermediate photoresist reservoir
218. In some embodiments, the condition of the photoresist held
within the intermediate photoresist reservoir 218 is monitored by a
pressure sensor 218P and or a temperature sensor 218T. In some
embodiments, the photoresist within the intermediate photoresist
reservoir 218 will be subjected to additional processing to further
reduce the quantity of gas(es) within the photoresist composition
and/or adjust the viscosity of the photoresist composition.
[0020] In some embodiments, the photoresist composition maintained
within the intermediate photoresist reservoir 218 will be subjected
to reduced pressure for a treatment period sufficient to remove a
portion of dissolved gas(es) from the photoresist composition in
those instances in which the photoresist was not degassed before
being loaded into the flexible photoresist container 210. While the
flexible photoresist container 210 isolates the photoresist from
the pressurized gas maintained in internal volume 208 to avoid
increasing the volume of dissolved gas within the photoresist,
unless degassed before loading, the photoresist within the flexible
photoresist container 210 includes a base level of dissolved gas.
In some embodiments, pump 219 will be used to produce the reduced
pressure in the intermediate photoresist reservoir 218. In addition
to the reduced pressure, in some embodiments, the photoresist
maintained within the intermediate photoresist reservoir will be
subjected to increased temperature in order to reduce the
solubility of dissolved gas(es) within the photoresist and/or
reduce the viscosity of the photoresist composition. In some
embodiments, after leaving the intermediate reservoir, the
photoresist will pass through a metered pump 220, one or more
control valves 222, and/or one or more filters 224 to reach the
dispensing nozzle 226 where the photoresist 228 is be applied to
the surface of a semiconductor substrate.
[0021] In some embodiments, the output of the metered pump 220 is
monitored by a flow sensor 218F and/or a pressure sensor 224P. In
some embodiments, in addition to the pressure sensor 224P, another
pressure sensor 224P' will be provided downstream of filter 224 in
order to evaluate the pressure drop across the filter as a measure
of the condition of the filter. In some embodiments, the pressure
sensor 224P' will be used to monitor the pressure of the
photoresist entering the dispensing nozzle 226.
[0022] The photoresist 228 is then dispensed through the dispensing
nozzle 226 onto the surface of a semiconductor substrate 232 to
form, in combination with lateral and/or arcuate movement of the
dispensing nozzle 226 and/or lateral and/or rotational movement of
the chuck 234, a photoresist film 230 on the surface of the
semiconductor substrate 232. In addition to controlling the
movement of the chuck 234, in some embodiments a temperature sensor
232T monitors the temperature of the chuck and, in conjunction with
a heat exchanger 236, is used for adjusting and/or maintaining the
temperature of the chuck within a target temperature range for
improving the uniformity of the photoresist film 230 formed on
successive semiconductor substrates 232. As will be appreciated, in
some embodiments the dispensing operation also includes the
application of one or more solvents and/or conditioning solutions
to the bare semiconductor substrate surface and/or to a quantity of
previously dispensed photoresist in order to obtain a photoresist
film having the desired parameters, e.g., thickness, uniformity,
and adhesion.
[0023] Accordingly, embodiments of photoresist dispensing system
200 according to FIG. 2 allow for the pressurization of the
photoresist without any direct contact between the photoresist and
the pressurized gas. Because there is no direct contact between the
photoresist and the pressurized gas, the quantity of gas dissolved
in the photoresist, if any, does not increase over the variable
time the photoresist is maintained within the system and variations
in the dissolved gas content within the photoresist are reduced or
avoided. By avoiding the introduction of additional dissolved gas
into the photoresist, the formation of bubbles resulting from
outgassing when the pressure applied to the photoresist is released
during the application process are reduced or eliminated. By
reducing or eliminating bubble formation within the photoresist
layer, the photoresist dispensing system according to FIG. 2
provides improved uniformity of the resulting photoresist layer.
Further, by isolating the photoresist from the interior of the
pressure vessel, the photoresist dispensing system according to
FIG. 2 reduces the likelihood of contamination being introduced
into the photoresist if the pressure vessel were to lose positive
pressure relative to the fabrication area in which the photoresist
dispensing system is housed.
[0024] FIG. 3 is a schematic diagram of a control system 300 useful
in operating a photoresist dispensing system in accordance with
some embodiments. The description of control system 300 is based on
elements from photoresist dispensing system 200. In some
embodiments, control system 300 is applicable to other photoresist
dispensing systems. In some embodiments, the control system 300 for
the photoresist dispensing system includes a controller 302
configured to receive input signals from one or more of the
pressure sensor, temperature sensor, flow sensor, and other sensors
provided throughout the photoresist dispensing system 200. In some
embodiments, the controller 302 is configured to communicate over a
bus 304 as part of an electronic process control (EPC) system.
[0025] In some embodiments, the controller is configured to access
one or more memory modules which maintain control instructions and
target parameter ranges for the operation of the photoresist
dispensing system. In some embodiments, the controller 302 is a
component in an electronic process control (EPC) system. In some
embodiments, the EPC system is configured in accord with the EPC
system of FIG. 7. In some embodiments the controller is configured
to output operational information to one or more displays for
operator reference, confirmation, and/or adjustment. In some
embodiments, the controller is configured to receive inputs from an
operator and/or other devices through one or more input/output
modules that will be used for adjusting one or more parameters in
the operation of the photoresist dispensing system. In some
embodiments, the controller is configured to output predetermined
information and/or alarms to other devices and/or an operator in
order to coordinate the operation of the photoresist dispensing
system with other equipment and/or prevent out of range
operation.
[0026] In some embodiments, the controller 302 uses the inputs from
the various sensors, valves, pumps, heat exchangers, memory
modules, and/or the input/output modules to determine whether to
adjust pressure, temperature, and/or photoresist flow within the
photoresist dispensing system in order to maintain the desired
operating conditions of the photoresist dispensing system 200. In
those instances in which the controller makes one or more
adjustments, the controller is configured to output control signals
to modify the operation of one or more of the valves, pumps,
heaters, chillers, heat exchangers, and/or other active elements
within the photoresist dispensing system in order to maintain
satisfactory operation.
[0027] In some embodiments, the electronic process control (EPC)
system 700 is used for monitoring a pressure (Pv) within the
pressurized internal volume 208 defined between the pressure vessel
206 and the flexible photoresist container 210 by controlling a
flowrate at which additional pressurized gas is introduced into the
monitored pressurized internal volume 208 to maintain an
operational pressure between a Target Pressure Low (TPL) and a
Target Pressure High (TPH). In some embodiments, the electronic
process control (EPC) system 700 is used for monitoring a flowrate
FR of photoresist into an intermediate reservoir and controlling a
flowrate at which the pressurized gas is introduced into the
pressurized internal volume 108, 208 to maintain the monitored
flowrate between a lower Target Flowrate Low (TFL) and a higher
Target Flowrate High (TFH).
[0028] In some embodiments, the quantity of gases dissolved in the
photoresist is further reduced by isolating a volume of the coating
composition within the intermediate photoresist reservoir 118, 218
while engaging a pump 119, 219 to reduce the pressure applied to
the volume of the coating composition to below 1 atm for a fixed or
variable treatment period to obtain a degassed photoresist
composition. In some embodiments, in addition to or in place of the
low pressure treatment, a heat exchanger 117, 217 is utilized for
increasing the temperature of the photoresist, thereby reducing the
solubility of gas(es) within the photoresist. The gas(es) released
from the photoresist are then released or evacuated using pump 119,
219 to obtain a degassed photoresist composition. The degassed
photoresist composition is then released from the intermediate
photoresist reservoir 118, 218 for application to the semiconductor
substrate 132, 232.
[0029] In some embodiments, the coating composition is degassed
before being introduced into the flexible photoresist container 110
by preparing or obtaining a coating composition and then
maintaining the coating composition under a vacuum for a treatment
period that reduces by at least 20% a volume of gas dissolved in
the coating composition to obtain a treated coating composition. In
some embodiments, the treated coating composition is then
introduced into the flexible container, a first volume of the
treated composition corresponding to a fill volume of the flexible
container, the filled volume defined by an interior surface of the
flexible container, wherein the filled volume is greater than the
initial volume.
[0030] In some embodiments, the coating composition is degassed
before being introduced into the flexible container by preparing or
obtaining a coating composition and then maintaining the coating
composition under an elevated temperature for a treatment period
that reduces by at least 20% a volume of N2, O2, CO2, and mixtures
thereof dissolved in the coating composition to obtain a treated
coating composition. In some embodiments, the treated coating
composition is then introduced into the flexible container, a first
volume of the treated composition corresponding to a fill volume of
the flexible container, the filled volume defined by an interior
surface of the flexible container, wherein the filled volume is
greater than the initial volume.
[0031] In some embodiments, a portion of residual gas is removed
from the flexible container before filling the flexible container
with photoresist. In some embodiments, a volume of photoresist in
excess of the fill volume of the flexible container is utilized to
generate a purge stream of excess photoresist for removing residual
gas, if any, from within the flexible container.
[0032] FIG. 4A is a diagram of a flexible photoresist container 400
in accordance with some embodiments. The flexible photoresist
container 400 includes a main storage reservoir 402 that is
attached to and forms enclosed storage volume with an attachment
assembly 404. The main storage reservoir may be manufactured from
any material that has a combination of strength sufficient to
maintain structural integrity when pressurized while still being
sufficiently flexible to collapse as the photoresist is withdrawn
from the container. Embodiments may be manufactured from a range of
polymer types, e,g., polyamides (PA), polyethylenes (PE),
polyethylene terephthalate (PET), polypropylenes (PP), polyvinyl
chlorides (PVC), polyvinylidene chlorides (PVDC), acrylonitrile
butadiene styrene (ABS), and may include more than one molecular
configuration of a single polymer and/or two or more types of
polymer in combination. The flexible photoresist container 400 is
fillable through a port 406a, 406b. In some embodiments, one or
more of the ports 406a, 406b is configured for establishing a
removable connection to both a fill line (through which photoresist
will be injected into the flexible photoresist container 400 during
a filling operation) and the output line (during operation) of the
photoresist dispensing system.
[0033] Depending on the placement of any check valves or other
hardware, establishing the proper connections to the ports 406a,
406b provided on the flexible photoresist container allows for
proper operation of the coating system. Further, because the use of
the inlet and/or outlet ports provides a sealed flexible
photoresist container, the orientation of the container is less
important in some embodiments. Indeed, in some embodiments
orienting or manufacturing the flexible photoresist container
whereby the outlet port is provided adjacent the lowest portion of
the container will assist in removing the contents with one or more
pumps rather than an externally applied pressure.
[0034] In some embodiments, the walls of the main storage reservoir
402 include at least one region of a reinforcing material 410 that
increases the strength and/or dimensional stability of the main
storage reservoir 402.
[0035] In some embodiments, the flexible photoresist container 400
will include a single port 406a with both the fill line and output
line being configured with complementary attachment assemblies to
ensure that the connection is maintained for the duration of the
relevant operations. In some embodiments, a plurality of ports
406a, 406b are utilized and will include dedicated input and output
ports that are configured differently to ensure proper connections
are established and maintained for the duration of the relevant
operations.
[0036] FIG. 4B is a diagram of a flexible photoresist container 400
in accordance with some embodiments. In comparison to the flexible
photoresist container 400 in FIG. 4A, a portion of the initial
photoresist volume has been removed from the main storage reservoir
402' through one or more of the ports 406a, 406b and the walls of
the flexible photoresist container 400 have contracted accordingly.
In some embodiments, the walls of the main storage reservoir 402
are manufactured from a flexible and durable material that is
generally impervious to the photoresist and anticipated
environmental conditions and contaminants that will be found (or
are likely to be found) in the manufacturing, packaging, transport,
and semiconductor device fabrication environments. The walls of the
main storage reservoir 402 are manufactured from a range of
polymeric materials including, without limitation, polyvinyl
chloride (PVC), polyethylene (PE), and polypropylene (PP).
[0037] As the photoresist is removed from the main storage
reservoir 402, the walls of the main storage reservoir 402 contract
to conform to the enclosed storage volume of the remaining volume
of photoresist. By ensuring that the flexible photoresist container
400 remains completely filled with photoresist over a wide volume
range, the contracting walls of the flexible photoresist container
help prevent external gases and/or contaminants from entering the
flexible photoresist container. In some embodiments, the walls of
the main storage reservoir 402 will include reinforcing material
410 and/or additional structure, e.g., pleats, folds, and/or
biasing means, which help to control the manner in which the walls
contract or expand in response to changes in pressure within the
pressure vessel and/or the volume of photoresist within the main
storage reservoir 402.
[0038] For example, in some embodiments, the walls of the main
storage reservoir 402 will include a band of peripheral reinforcing
material 410, e.g., an arrangement of fibers, strips and/or other
regions of a stronger (higher density), thicker, and/or less
flexible type of material, polymer, and combinations thereof, for
increasing the structural integrity of the main storage reservoir,
to which one or more sheets or regions of more flexible material
are used in combination to form the wall(s) of the main storage
reservoir. In some embodiments, the walls of the main storage
reservoir may comprise two flexible sheets that are bonded or
otherwise joined along a periphery to form a thicker band of
reinforcing material 410. With such an arrangement, the reinforcing
material 410 assists in maintaining dimensional stability in one or
more dimensions even as the volume of the main storage reservoir
decreases as the photoresist is consumed. Similarly, in some
embodiments vertical or horizontal pleats will be used to control
the "collapse" of the flexible photoresist container to avoid
sagging and/or increase the volume of photoresist or other coating
composition removed from the flexible photoresist container 400 as
the main storage reservoir 402 is compressed by the external
pressure.
[0039] Although the volume of the main storage reservoir 402
decreases as the photoresist is consumed, the attachment assembly
404 is configured and constructed to provide a more dimensionally
stable attachment structure by which a flexible photoresist
container is attached to the photoresist filling assembly of a
photoresist dispensing system (not shown), directly to photoresist
coating equipment which does not include a separate pressure vessel
and extracts the photoresist from the flexible photoresist
container using a pump rather than a pressure vessel, and/or to the
pressure vessel used to apply external pressure to the flexible
photoresist container. The use of a flexible photoresist container
400 configured for attachment to a pressure vessel that remains
fixed within the photoresist coating equipment reduces
manufacturing costs and required storage volume by eliminating the
need for a separate pressure vessel for each flexible photoresist
container while still suppressing or eliminating bubble formation
as the photoresist is dispensed onto a substrate.
[0040] FIG. 5A illustrates an embodiment of a photoresist container
500 useful in practicing the disclosed methods in which a flexible
photoresist container comprising a main storage reservoir 502 is
incorporated within a pressure vessel 508 to form a more integrated
or unitary assembly than that shown in FIG. 4A. In some
embodiments, the enclosed storage volume is defined between the
main storage reservoir 502 and an attachment assembly 504. The
photoresist container 500 will be provided with port 506a, 506b
through which the main storage reservoir 502 will be filled and/or
emptied. In some embodiments, one or more ports 506a, 506b will be
configured for establishing a removable connection to both a fill
line (for introducing photoresist into the main storage reservoir
502) and an output line (during operation) of the photoresist
dispensing system. In some embodiments, one port 506a will be
configured for establishing a first removable connection to a fill
line (for introducing photoresist into the main storage reservoir
502) and with another port 506b being configured for establishing a
second removable connection the output line (during operation) of
the photoresist dispensing system to avoid cross connections
between the fill line, the output line, and the ports 506a,
506b.
[0041] In some embodiments, the pressure vessel 508 will be
provided with a complementary second attachment assembly 510 which
will cooperate with the first attachment assembly 504 to position
the flexible photoresist container within the pressure vessel and
define the pressurized space between the inner surface of the
pressure vessel and the outer surface of the flexible photoresist
container. In some embodiments, the first attachment assembly 504
on the main storage reservoir 502 engages the second attachment
assembly 510 on the pressure vessel 508 to form a temporary
attachment between the flexible container, the temporary attachment
sealing and defining an initial pressurized volume. In some
embodiments, compressed gas will be introduced into this
pressurized space through port 512 in order to maintain a target or
operating pressure range within the pressurized space that tends to
force the photoresist composition out of the flexible photoresist
container and through a port 506a, 506b.
[0042] In some embodiments, the flexible photoresist container will
include only a single port with both the fill line and output line
being configured with complementary attachment assemblies to ensure
that the connection is maintained for the duration of the relevant
operations. In some embodiments, a plurality of ports (not shown)
will be utilized and will include dedicated input and output ports
that are configured differently (not shown) to ensure proper
connections are established and maintained for the duration of the
relevant operations.
[0043] FIG. 5B illustrates an embodiment of a photoresist container
500 according to FIG. 5A in which a portion of the initial
photoresist volume has been removed from the main storage reservoir
502' and the walls of the flexible photoresist container have
contracted accordingly with additional compressed gas being
introduced into the pressure vessel 508 through port 512 in order
to maintain the target or operating pressure within the pressure
vessel. The pressure maintained within the pressure vessel will
continue compressing the flexible photoresist container and
continue urging the photoresist composition through the port 506
and into the coating apparatus where it will undergo some
additional processing. In some embodiments, the walls of the main
storage reservoir are manufactured from a flexible and durable
material that is generally impervious to the photoresist and
anticipated environmental fluids and contaminants that will be
found in the manufacturing, packaging, transport, and manufacturing
environments.
[0044] As the photoresist is removed from the main storage
reservoir, the walls of the main storage reservoir will contract to
match the enclosed storage volume with the remaining volume of
photoresist. By ensuring that the flexible photoresist container
remains "full" over a wide volume range, the walls of the flexible
photoresist container prevent any external gases and/or
contaminants from entering the flexible photoresist container. In
some embodiments, the walls of the main storage reservoir will
include reinforcement and/or additional structure, e.g., pleats,
folds, and/or biasing means, which will control the manner in which
the walls contract under pressure.
[0045] For example, the walls of the main storage reservoir will
include a band of peripheral reinforcing material 514 or other
internal structure (not shown) to which one or more sheets of a
more flexible material are attached to form the main storage
reservoir. With such an embodiment, the reinforcing material
assists in maintaining dimensional stability in one or more planes
even as the volume of the main storage reservoir decreases as the
photoresist is consumed and the more flexible material contracts.
Similarly, in some embodiments vertical pleats will be used to
control the "collapse" or "contraction" of the flexible photoresist
container to avoid sagging film and/or increase the volume of
photoresist or other coating composition removed from the container
as it is compressed by the external pressure established and/or
maintained within the pressure vessel.
[0046] Although the volume of the main storage reservoir 502
decreases as the photoresist is consumed, the attachment assembly
504 is configured and constructed to provide a more dimensionally
stable attachment structure by which the flexible photoresist
container will be attached to the photoresist filling assembly (not
shown), directly to the photoresist coating equipment (not shown),
and/or to the pressure vessel 508 that will be used to apply
external pressure to the flexible photoresist container. The use of
a unitary flexible photoresist container/pressure vessel
photoresist container 500 for mounting within the photoresist
dispensing system 100 reduces manufacturing costs, leaks, and/or
maintenance time by eliminating the need for operators or
technicians to remove a spent flexible photoresist container and
attach a new flexible photoresist container to a separate pressure
vessel while still suppressing or eliminating bubble formation as
the photoresist is dispensed onto a substrate.
[0047] Although embodiments of the apparatus, system, and method
are not limited to any particular type or viscosity of photoresist
compositions, microbubble formation and retention is typically
associated with higher viscosity photoresist compositions. A
variety of photoresists is available to process engineers in a
range of chemistries and viscosities. Polyimide photoresists are
generally among the more viscous photoresist compositions,
typically having viscosities of a least 50 centipoise. In order to
improve the application of high viscosity photoresist compositions,
methods have been developed that include the sequential application
of a lower viscosity coating composition such as a reducing resist
consumption (RRC) material from a source separate from a primary
photoresist composition source.
[0048] In some embodiments, the primary photoresist composition
source and RRC material source both include separate pumps and/or
nozzles for sequentially dispensing the photoresist coating and RRC
coating(s), respectively. In other embodiments, the photoresist
composition and the RRC material are both directed through a single
pump and are sequentially dispensed through a single nozzle. In
some embodiments, the RRC material includes at least one solvent
capable of dissolving the polymer(s) that comprise the photoresist
composition.
[0049] The photoresist composition polymer can be any of a variety
of materials. In some embodiments, the polymer(s) (i.e., the
photoresist composition) has a viscosity of at least 50 centipoise,
in some embodiments, the viscosity is in a range from 1500 to 3000
centipoise, while in some embodiments the viscosity will reach or
exceed 10,000 centipoise.
[0050] Photoresist compositions can be selected from a wide range
of formulations including, for example, a polyimide or
polybenzoxazole (PBO) film; a polyimide precursor, polyimide, or
PBO precursor; or a polyimide matrix resin.
[0051] FIG. 6 is a flowchart of a method for preparing a flexible
photoresist container in accordance with some embodiments. The
method is useful for practicing the methods and/or configuring the
systems disclosed herein for improving the quality of photoresist
films applied to substrates. In some embodiments, in optional
operation 602 the photoresist composition will be manufactured. In
some embodiments, operation 602 is omitted because the photoresist
composition is obtained by purchasing one or more suitable
photoresist compositions.
[0052] In some embodiments of the method, in optional step 604 the
photoresist composition will be degassed through application of
reduced pressure and/or increasing a bulk photoresist temperature.
The treatment time utilized during the degassing operation(s)
depends on a number of factors including, for example, the nature
of the dissolved gas(es), the concentration of the dissolved
gas(es), the surface area of the photoresist composition being
treated, the magnitude of the reduced pressure, and/or the
magnitude of the increased photoresist temperature. The degassing
operation lowers the concentration of the dissolved gas(es) within
the photoresist composition prior to filling the flexible container
to help ensure that the subsequent exposure to atmospheric pressure
during the photoresist application operation will not generate
bubbles within the photoresist composition.
[0053] In some embodiments, once the original photoresist
composition has been treated to remove a portion of the dissolved
gas(es), the treated photoresist composition will be loaded into a
flexible photoresist container in step 606. This filling operation
should occur shortly after the degassing operation(s) have been
completed in order to limit the opportunity for one or more gases
to dissolve in the treated photoresist composition. The volume of
treated photoresist composition introduced into the flexible
photoresist container should be sufficient to provide a target fill
volume and expel any residual gas(es) within the flexible
photoresist container. For those filling operations that utilize a
flexible photoresist container having both an inlet port and an
outlet port, in some embodiments, the filling operation may include
a deliberate overfill in order to generate a purge flow through the
outlet port, thereby ensuring that the treated photoresist
composition fills substantially all of the flexible photoresist
container.
[0054] In some embodiments, once the flexible photoresist container
has been filled with the treated photoresist composition, the
flexible photoresist container will be placed in and/or attached to
a pressure vessel in step 608. In some embodiments, this operation
will be completed in conjunction with the manufacture and filling
of the flexible photoresist container. A composite or unitary
assembly comprising both the flexible photoresist container and the
pressure vessel will then be available for installation in the
photoresist dispensing apparatus. In some embodiments, the filled
flexible photoresist container will be installed in the pressure
vessel by an operator or technician as needed.
[0055] In some embodiments, once the filled flexible photoresist
container and the pressure vessel have been installed in and
connected to the coating apparatus, a pressurized space between the
interior surface of the pressure vessel and an exterior surface of
the flexible photoresist container may be filled with a volume of
compressed gas sufficient to apply a target or operating pressure
to the exterior surface of the flexible photoresist container,
thereby tending to force the photoresist composition from the
flexible photoresist container through an outlet port and into the
downstream portions of the coating apparatus in optional step
610.
[0056] FIG. 7 is a block diagram of an electronic process control
(EPC) system 700, in accordance with some embodiments. Methods
described herein of generating cell layout diagrams, in accordance
with one or more embodiments, are implementable, for example, using
EPC system 700, in accordance with some embodiments. In some
embodiments, EPC system 700 is a general purpose computing device
including a hardware processor 702 and a non-transitory,
computer-readable storage medium 704. Storage medium 704, amongst
other things, is encoded with, i.e., stores, computer program code
(or instructions) 706, i.e., a set of executable instructions.
Execution of computer program code 706 by hardware processor 702
represents (at least in part) an EPC tool which implements a
portion or all of, e.g., the methods described herein in accordance
with one or more (hereinafter, the noted processes and/or
methods).
[0057] Hardware processor 702 is electrically coupled to
computer-readable storage medium 704 via a bus 718. Hardware
processor 702 is also electrically coupled to an I/O interface 712
by bus 718. A network interface 714 is also electrically connected
to processor 702 via bus 718. Network interface 714 is connected to
a network 716, so that hardware processor 702 and computer-readable
storage medium 704 are capable of connecting to external elements
via network 716. Hardware processor 702 is configured to execute
computer program code 706 encoded in computer-readable storage
medium 704 in order to cause system 700 to be usable for performing
a portion or all of the noted processes and/or methods. In one or
more embodiments, hardware processor 702 is a central processing
unit (CPU), a multi-processor, a distributed processing system, an
application specific integrated circuit (ASIC), and/or a suitable
processing unit.
[0058] In one or more embodiments, computer-readable storage medium
704 is an electronic, magnetic, optical, electromagnetic, infrared,
and/or a semiconductor system (or apparatus or device). For
example, computer-readable storage medium 704 includes a
semiconductor or solid-state memory, a magnetic tape, a removable
computer diskette, a random access memory (RAM), a read-only memory
(ROM), a rigid magnetic disk, and/or an optical disk. In one or
more embodiments using optical disks, computer-readable storage
medium 704 includes a compact disk-read only memory (CD-ROM), a
compact disk-read/write (CD-R/W), and/or a digital video disc
(DVD).
[0059] In one or more embodiments, storage medium 704 stores
computer program code 706 configured to cause EPC system 700 (where
such execution represents (at least in part) the EPC tool) to be
usable for performing a portion or all of the noted processes
and/or methods. In one or more embodiments, storage medium 704 also
stores information which facilitates performing a portion or all of
the noted processes and/or methods. In one or more embodiments,
storage medium 704 stores process control data 708 including, in
some embodiments, control algorithms, process variables and
constants, target ranges, set points, and code for enabling
statistical process control (SPC) and/or model predictive control
(MPC) based control of the various processes.
[0060] EPC system 700 includes I/O interface 712. I/O interface 712
is coupled to external circuitry. In one or more embodiments, I/O
interface 712 includes a keyboard, keypad, mouse, trackball,
trackpad, touchscreen, and/or cursor direction keys for
communicating information and commands to processor 702.
[0061] EPC system 700 also includes network interface 714 coupled
to processor 702. Network interface 714 allows EPC system 700 to
communicate with network 716, to which one or more other computer
systems are connected. Network interface 714 includes wireless
network interfaces such as BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA;
or wired network interfaces such as ETHERNET, USB, or IEEE-1364. In
one or more embodiments, a portion or all of noted processes and/or
methods, is implemented in two or more EPC systems 700.
[0062] EPC system 700 is configured to receive information through
I/O interface 712. The information received through I/O interface
712 includes one or more of instructions, data, design rules,
process performance histories, target ranges, set points, and/or
other parameters for processing by hardware processor 702. The
information is transferred to processor 702 via bus 718. EPC system
700 is configured to receive information related to a user
interface (UI) through I/O interface 712. The information is stored
in computer-readable medium 704 as user interface (UI) 710.
[0063] In some embodiments, a portion or all of the noted processes
and/or methods is implemented as a standalone software application
for execution by a processor. In some embodiments, a portion or all
of the noted processes and/or methods is implemented as a software
application that is a part of an additional software application.
In some embodiments, a portion or all of the noted processes and/or
methods is implemented as a plug-in to a software application. In
some embodiments, at least one of the noted processes and/or
methods is implemented as a software application that is a portion
of an EPC tool. In some embodiments, a portion or all of the noted
processes and/or methods is implemented as a software application
that is used by EPC system 700.
[0064] In some embodiments, the processes are realized as functions
of a program stored in a non-transitory computer readable recording
medium. Examples of a non-transitory computer readable recording
medium include, but are not limited to, external/removable and/or
internal/built-in storage or memory unit, e.g., one or more of an
optical disk, such as a DVD, a magnetic disk, such as a hard disk,
a semiconductor memory, such as a ROM, a RAM, a memory card, and
the like.
[0065] In some embodiments, a coating system comprises a vessel, a
flexible container within the vessel, the flexible container
including an outlet port, wherein the flexible container is
configured to contract in response to an increase in pressure
within the vessel, and the flexible container is configured to
output a coating composition through the outlet port in response to
contraction; and a coating apparatus for receiving the coating
composition from the outlet port. In some embodiments, the coating
system utilizes a photoresist as the coating composition. In some
embodiments, the coating system includes an intermediate reservoir
containing a first volume of the coating composition and a second
volume of the coating composition is applied to a substrate, a
ratio between the first volume and the second volume is at least
5:1. In some embodiments, the coating system utilizes a controller
for controlling the pressure within the vessel and/or a filter
through which the coating composition passes to reach a dispensing
nozzle.
[0066] In some embodiments, the coating system utilizes a secondary
reservoir between the flexible container and the dispensing nozzle,
the secondary reservoir being sized to receive the first volume of
the coating composition.
[0067] In some embodiments, the coating system utilizes a flexible
container having a reinforced region, the reinforced region having
an interior surface area and being connected to the first
attachment apparatus. In some embodiments, the flexible region has
a variable interior surface area and is connected to the reinforced
region, wherein the interior surfaces of the reinforced region, the
first attachment apparatus, and the flexible region define a
variable container volume.
[0068] In some embodiments, the coating system utilizes a first
attachment apparatus that further comprises a plurality of ports
comprising the outlet port and an inlet port. In some embodiments,
the outlet port has a first configuration operable for establishing
a fluidic connection with the outlet line; and the inlet port has a
second configuration operable for preventing the establishment of a
fluidic connection to the outlet line.
[0069] In some embodiments, a coating method used for forming a
coating layer on a substrate involves arranging a flexible
container within a pressure vessel, the flexible container
containing an initial volume of a coating composition, the initial
volume being sufficient to fill the flexible container to a full
volume, and an outlet port provided on the flexible container;
introducing a pressurized gas into a pressurized volume defined
between an exterior surface of the flexible container and an
interior surface of the pressure vessel, the pressurized gas
tending to force the coating composition through the outlet port
and, eventually to a nozzle where the photoresist is applied to a
substrate to form a layer of the coating composition.
[0070] In some embodiments, the coating method used includes
engaging a first attachment assembly on the flexible container with
a second attachment assembly on the pressure vessel to form a
temporary attachment and define an initial pressurized volume.
[0071] In some embodiments, the coating method used includes
monitoring a pressure (PV) within the pressurized volume;
controlling a flowrate at which additional pressurized gas is
introduced into the pressurized volume to maintain an operational
pressure between a Target Pressure Low (TPL) and a Target Pressure
High (TPH).
[0072] In some embodiments, the coating method used includes
monitoring a first flowrate of photoresist FR into an intermediate
reservoir; controlling a second flowrate at which the pressurized
gas is introduced into the pressurized volume to maintain the first
flowrate between a lower Target Flowrate Low (TFL) and a higher
Target Flowrate High (TFH).
[0073] In some embodiments, the coating method used includes
isolating the first volume of the coating composition within an
intermediate reservoir; reducing the pressure applied to the first
volume of the coating composition to a pressure below 1 atm for a
treatment period to obtain a degassed coating composition; and
releasing the degassed coating composition from the intermediate
reservoir for application to the substrate.
[0074] In some embodiments, the coating method used includes
preparing a unitary assembly comprising the flexible container and
the pressure vessel; connecting the pressurized gas to a port
provided on the pressure vessel; and connecting the outlet port to
an outlet line.
[0075] In some embodiments, the coating method used includes
isolating the first volume of the coating composition within an
intermediate reservoir; monitoring a temperature TV of the first
volume of the coating composition; adjusting the temperature TV of
the first volume of the coating composition as necessary to obtain
a coating composition viscosity within a predetermined viscosity
range; releasing the adjusted first volume of the coating
composition from the intermediate reservoir for application to the
substrate.
[0076] In some embodiments, the coating method used includes
preparing a flexible container, the flexible container having an
initial volume; preparing a coating composition; maintaining the
coating composition under a vacuum for a treatment period to reduce
by at least 20% a volume of gas (O2, N2, CO2, or mixtures thereof)
dissolved in the coating composition to obtain a treated coating
composition; introducing a first volume of the treated coating
composition to the flexible container, the first volume of the
treated composition corresponding to a fill volume of the flexible
container, the filled volume defined by an interior surface of the
flexible container, with the filled volume being greater than the
initial volume.
[0077] In some embodiments, the coating method used includes
warming the coating composition during the treatment period to a
treatment temperature to reduce a gas solubility by at least 20%
for at least one gas selected from a group consisting of N2, O2,
CO2, and mixtures thereof.
[0078] In some embodiments, the coating method used includes
evacuating a residual gas from the flexible container; and
introducing a second volume of the treated coating composition into
the flexible container to generate a purge stream through the
outlet port.
[0079] Although the subject matter has been described in terms of
exemplary embodiments, it is not limited thereto. The appended
claims should, therefore, be construed broadly and found to include
other variants and embodiments, which may be made by those skilled
in the art.
[0080] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
* * * * *