U.S. patent application number 10/253206 was filed with the patent office on 2004-03-25 for apparatus and method for in-situ cleaning of borosilicate (bsg) and borophosphosilicate (bpsg) films from cvd chambers.
This patent application is currently assigned to Infineon Technologies Richmond, LP. Invention is credited to Govindarajan, Shrinivas, Jain, Ankur.
Application Number | 20040055708 10/253206 |
Document ID | / |
Family ID | 31993125 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040055708 |
Kind Code |
A1 |
Govindarajan, Shrinivas ; et
al. |
March 25, 2004 |
Apparatus and method for in-situ cleaning of borosilicate (BSG) and
borophosphosilicate (BPSG) films from CVD chambers
Abstract
A method for cleaning borosilicate (BSG) and borophosphosilicate
(BPSG) films from CDV chambers including controlling the pressure
within the chamber, introducing Ar into the chamber, introducing
NF.sub.3 into the chamber, adjustably spacing a heater relative to
the chamber, and adjusting the temperature within the chamber.
Inventors: |
Govindarajan, Shrinivas;
(Glen Allen, VA) ; Jain, Ankur; (Richmond,
VA) |
Correspondence
Address: |
F. Chau & Associates, LLP
Suite 501
1900 Hempstead Turnpike
East Meadow
NY
11554
US
|
Assignee: |
Infineon Technologies Richmond,
LP
|
Family ID: |
31993125 |
Appl. No.: |
10/253206 |
Filed: |
September 24, 2002 |
Current U.S.
Class: |
156/345.24 ;
134/1.1; 156/345.26; 156/345.27 |
Current CPC
Class: |
B08B 7/0035 20130101;
C23C 16/4405 20130101 |
Class at
Publication: |
156/345.24 ;
134/001.1; 156/345.26; 156/345.27 |
International
Class: |
C25F 003/30; C23F
001/00 |
Claims
What is claimed is:
1. A method for cleaning a CVD reaction chamber, comprising the
steps of: controlling the pressure within the chamber; introducing
Ar into the chamber; introducing NF.sub.3 into the chamber;
adjustably spacing a heater relative to the chamber; and adjusting
the temperature within the chamber.
2. The method of claim 1, wherein the pressure is controlled
between 2.5 Torr and 4.5 Torr.
3. The method of claim 1, wherein the pressure is controlled at
about 3 Torr.
4. The method of claim 1, wherein the Ar is introduced at a rate of
about 1,500 sccm to about 1,800 sccm.
5. The method of claim 1, wherein the Ar is introduced at a rate of
about 1,600 sccm to about 1,750 sccm.
6. The method of claim 1, wherein the NF.sub.3 is introduced at a
rate of about 1,100 sccm to about 1,200 sccm.
7. The method of claim 1, wherein the NF.sub.3 is introduced at a
rate of about 1,150 sccm.
8. The method of claim 1, wherein spacing the heater relative to
the chamber comprises spacing the heater from greater than 600 mils
to about 1,500 mils relative to a showerhead.
9. The method of claim 1, wherein adjusting the temperature within
the chamber comprises adjusting the temperature to be substantially
identical to the temperature used in the deposition process.
10. The method of claim 1, including the step of cleaning a
backside of a throttle valve comprising setting a pressure set
point to throttle to 1600 steps, introducing Ar at a rate of about
1,600 sccm into the chamber and introducing NF.sub.3 at a rate of
1,150 sccm into the chamber.
11. The method of claim 1, including the step of optimizing the
clean duration for a specific film comprising correlating a clean
endpoint with a change in a slope of a foreline pressure versus
time plot graph.
12. The method of claim 11, wherein said specific film includes one
of Borosilicate (BSG) film and Borophosphosilicate (BPSG) film.
13. The method of claim 1, including the step of optimizing the
clean duration for a specific film comprising correlating a clean
endpoint with a stabilization of a species selected from the group
consisting of HF, SiFx, BF.sub.3, and F.sub.x.
14. The method of claim 13, wherein said specific film includes one
of Borosilicate (BSG) film and Borophosphosilicate (BPSG) film.
15. The method of claim 1, including the step of optimizing the
clean duration for a specific film comprising correlating the time
to clean a window within a CVD reaction chamber with a second peak
in a foreline pressure versus time plot graph.
16. The method of claim 15, wherein said specific film includes one
of Borosilicate (BSG) film and Borophosphosilicate (BPSG) film.
17. An apparatus for cleaning a CVD reaction chamber, the apparatus
comprising: servo device for controlling the pressure within the
chamber using PID methodology; first mass-flow device for
introducing Ar into the chamber; second mass-flow device for
introducing NF.sub.3 into the chamber; heater spacing device for
adjustably spacing a heater relative to the chamber; and
temperature control device for adjusting the temperature within the
chamber.
18. A program storage device readable by machine, tangibly
embodying a program of instructions executable by the machine to
perform method steps for cleaning a CVD reaction chamber, the
method steps comprising: controlling the pressure within the
chamber; introducing Ar into the chamber; introducing NF.sub.3 into
the chamber; adjustably spacing a heater relative to the chamber;
and adjusting the temperature within the chamber.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the in-situ cleaning of
borosilicate (BSG) and borophosphosilicate (BPSG) films from the
interior surfaces of chemical vapor deposition (CVD) chambers.
BACKGROUND OF THE INVENTION
[0002] A problem with depositing BSG and BPSG films upon
semiconductors is that the inside of the CVD chamber are also
coated with the film being deposited. This coating should be
cleaned off periodically to avoid contamination and defects which
can arise due to the deposited film "flaking off" from the inner
walls of the reactor.
[0003] The semiconductor industry uses large quantities of
expensive, fluorine-containing gases, for example,
C.sub.nF.sub.2n+2 and nitrogen triflouride (NF.sub.3) to clean CVD
chambers. By-products from the cleaning reactions include F.sub.2,
C.sub.nF.sub.2n+2, HF, and other species that are poisonous and
difficult to scrub from process waste streams. For example, a
typical cleaning procedure using NF.sub.3 would remove a BSG or
BPSG glass film from the inside of a CVD chamber according to the
generic formula:
(2+w)F+SiO.sub.xB.sub.yP.sub.z=SiF.sub.w+HF+F+volatiles
[0004] where F is free fluorine that condenses to molecular F.sub.2
upon exhaust.
[0005] There is an ongoing effort in the semiconductor
manufacturing industry to reduce consumption of gases with high
global warming potentials (GWP). One approach has been to move
towards a remote plasma clean system using nitrogen trifluoride
(NF.sub.3), which is more environmentally favorable. The high cost
of NF.sub.3 as well as the recurring threats of industry-wide
shortages, however, have resulted in numerous investigations to
optimize cleans, many of which are described in D. Wuebbles,
Perfluorocompound Emission Control, Proceedings of the Global
Semiconductor Industry Conference, Monterey, Calif., Apr. 7-8,
(1998).
[0006] One method of cleaning the deposition reactor is with the
help of a remote plasma source (RPS) unit, such as a pressurized
torroidal plasma generator or a microwave generator, which is used
to generate free fluorine for the cleaning process. The RPS unit is
connected to the chamber by a valved conduit which is commonly
available from a number of vendors. CVD reactor chamber walls will
become contaminated with a film of BSG or BPSG every time a
semiconductor wafer is coated with such a film. It is necessary to
clean the reaction chamber walls periodically, depending on the
film thicknesses being deposited. A ballpark estimate of the
maximum thickness before a clean is essential is about 20,000 .ANG.
(2,000 nm or 2 .mu.m) of film deposition so as to prevent these
deposits from flaking off the chamber surfaces and contaminating
wafers in the form of particulates.
[0007] The remote plasma chamber will usually be pressurized with
an inert gas such as argon (Ar), which is used to "ignite" the
plasma and a fluorine-containing compound, such as NF.sub.3. The
NF.sub.3 is dissociated into a low-energy plasma, resulting in the
generation of free fluorine which is fed into the CVD chamber
through the conduit. The pressure in the reactor is controlled by a
so-called "throttle valve."
[0008] A typical remote plasma source (RPS) cleaning processes for
borosilicate glass (BSG) and borophosphosilicate glass (BPSG) films
involves a main clean of the reaction chamber at 2.2 torr with
NF.sub.3 and Ar set at 950 sccm and 1400 sccm, respectively,
followed by a second cleaning step with identical flows but with
the throttle valve set to 1600 steps (to clean the back of the
throttle valve). The throttle valve at 800 steps is fully open, but
only one surface of the throttle valve is thereby cleaned. To clean
the back surface that has not come into contact with the fluorine,
the throttle valve must flip to the 1600 steps position, at which
setting the backside of the throttle valve is cleaned. If the
throttle valve is not cleaned adequately, pressure faults occur due
to the inadequate seal made by the throttle valve. The cleaning
durations are not optimized because of the lack of a suitable
endpoint detection system to determine when cleaning is
complete.
[0009] What is needed is an optimized method of cleaning BSG and
BPSG films so as to minimize cleaning time, costs, and fluorine
effluents.
SUMMARY OF THE INVENTION
[0010] The above disadvantages of the prior art are addressed by a
method for a remote plasma source (RPS) cleaning process for BSG
and BPSG films deposited in a CVD chamber. The presently disclosed
method includes controlling the pressure within the chamber,
introducing Ar into the chamber, introducing NF.sub.3 into the
chamber, adjustably spacing a heater relative to the chamber, and
adjusting the temperature within the chamber. The actual
temperature used will depend on the temperature used for the
deposition process. Additionally, a methodology for determining the
endpoint of the clean using residual gas analysis and the evolution
of foreline pressure is described.
[0011] These and other aspects, features and advantages of the
present disclosure will become apparent from the following
description of exemplary embodiments, which is to be read in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1a and 1b graph the effects of process parameters upon
etch rate.
[0013] FIG. 2 graph the effects of process parameters upon etch
rate using a statistical software package sold by SAS institute,
Inc. under the tradename JMP.
[0014] FIG. 3 and 4 show graphs of experimental results and
statistical analysis.
[0015] FIG. 5 shows some typical values for using the method of the
invention.
[0016] FIG. 6 shows an embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0017] Disclosed herein is a method for an optimized remote plasma
source (RPS)--based cleaning for BSG and BPSG films deposited in an
Applied Materials CxZ chamber. It is found that the dominant
parameters for such an optimization are chamber pressure, NF.sub.3
flow, and argon flow. An optimized set of parameters is disclosed
and verified with stability tests using blanket wafers. These are
wafers with no patterning on them, basically bare silicon wafers.
It is disclosed that overall cost reductions of about 20% per wafer
and process time reductions of about 30% are attainable over the
prior art using the methods of the invention.
[0018] The etch rate measured on oxide wafers is not an adequate
measure of the clean efficiency. The "effective" etch rate (i.e.
total film thickness deposited on the wafer divided by the total
clean time ) was compared for different films (BSG and BPSG) and
different thicknesses. The mean "etch rate" for BSG increases from
8406 .ANG./min (Prior Art) to 12304 .ANG./min (New Process) and for
BPSG from 15062 .ANG./min (Prior Art) to 21028 .ANG./min (New
Process). This represents a 46% increase for BSG and a 39.6%
increase in etch rate for BPSG.
[0019] Referring to FIGS. 1a and 1b, to determine the effects of
the critical process parameters, such as chamber pressure,
NF.sub.3, Ar, spacing (the distance between the heater on which the
wafer sits and the shower head from which the process gases are
delivered), and the like on the etch rate, experiments were
conducted with thermal oxide wafers.
[0020] As can be seen in FIG. 1a, baseline tests show a strong
effect of wait time on the etch rate--thereby indicating that wafer
temperature affects the etch rate. "Wait time" refers to the
duration the wafer sits on the heater (inside the deposition
chamber) before the process gases are introduced. The longer the
wafer sits in the chamber, the closer the temperature of the wafer
approaches that of the heater (i.e., 480C.). "9PT" and "49PT" refer
to the number of sites where thickness is measured, namely 9
locations or 49 locations.
[0021] Referring to FIG. 1b, the test also demonstrates that the
etch rate exhibits a transient behavior during the first few
seconds of the etch. "Power" refers to the modeling equation,
specifically how the relations between etch rate and time are
fitted, and actually has nothing to do with the clean itself, but
rather is generated by the statistical software used.
[0022] Additional tests indicated that the chamber condition prior
to the experiment affected the etch rate (i.e., whether a BSG/BPSG
film has been deposited and whether the chamber has been cleaned
prior to the experiment). The results of these tests are not shown
in the figures. These were separate tests where the goal was to
determine what factors influenced the etch rate vs. time
relationship. Experimental conditions were identified to minimize
the variability introduced by these controllable factors.
[0023] Referring to FIGS. 2a and 2b, full factorial experiments
were run to identify the effects of the critical variables. The
results are summarized in FIGS. 2a and 2b through interaction plots
provided by a commercially available statistical software package
sold by SAS institute, Inc. under the tradename JMP. Chamber
pressure and NF.sub.3 flow rate have the strongest effects on etch
rate. Ar was fixed at 1600 Sccm (standard centimeter cubed per
minute) because it has a positive influence on uniformity and would
help to provide a more stable plasma at higher NF.sub.3 flow rates.
However, the oxide etch rate tests essentially provided information
about the main effects on the localized etch rate above the heater
and did not address the etch rate at other locations in the
chamber. One useful tool that was utilized is a quartz window near
the rear of the CVD chamber, which allows a visual observation of
the film deposition and removal (during the clean). The time to
clean the window is found to follow a linear trend with increasing
film thickness.
[0024] FIG. 2a shows the "interaction plots"--this is a useful
graphical method of analyzing the effect of multiple variables on a
response. For example, you can see simultaneously the effects of
pressure, spacing, and NF.sub.3 flow on Etch rate: the X-axis
consists of three segments--pressure 1.78 to 2.64 torr;
spacing--440 to 800 mils; and NF flow--880 to 1050 sccm. The Y-axis
has three segments to show the effect of two of the three
variables. For example, with pressure fixed at 1.78 torr,
increasing NF.sub.3 would increase etch rate and increasing spacing
would also increase etch rate, but increasing spacing has a much
greater impact. These plots also show if there are "interactions"
between variables. Interactions appear where two lines are not
parallel to one another.
[0025] FIG. 2b is a simpler graph called a "prediction
profile"--this is a tool provided by the JMP statistical software
to find an "optimum" setting for multiple variables and responses.
In other words, you can move around the set points for each
variable and see how it impacts the response.
[0026] Referring to FIG. 3, a response surface design was used to
determine the optimum settings for NF.sub.3 and chamber pressure
during the clean. In the graph called Actual vs. Predicted, the
different lines show the confidence limits. This is a plot which
shows the values (for the window clean time) predicted by the model
(X-axis) and the actual values obtained during experiments
(Y-axis). The other two graphs show the effect of individual
variables, like pressure and NF.sub.3 flow, on the response. The
response in this case is the time to "clean the window". The
"window" is a translucent quartz window located on the chamber lid
near the foreline. During film deposition, the window builds up a
white film. The cleaning of this window is a secondary tool to
determine that the clean is working. The time to clean the window
could be correlated to one of the peaks observed in the pressure
versus time trace for the "backing pressure" (i.e., pressure
measured in the foreline). The etch rate referred to in FIGS. 1a
and 1b is the rate at which the oxide film on a flat wafer is
removed by the clean. The etch rate measured using a thermal oxide
wafer was not an appropriate method to determine the clean efficacy
(because it only addresses the etch rate above the heater and does
not take into account the cleaning of the entire chamber). The
results are summarized in FIGS. 4a and 4b with a prediction
profiler.
[0027] Referring to FIGS. 4a and 4b, the prediction profiler, which
graphically displays the effects of variables on responses, is
shown. A minima in the time to clean the window at a pressure
setting of about 3 torr of NF.sub.3 in the reaction chamber can be
observed. The model fit indicates that 97% of the variation could
be explained. On the other hand, increasing NF.sub.3 flow shows a
continuous decrease in the clean time (i.e., increasing etch
rate).
[0028] The results therefore identify two critical parameters for
the cleaning method of the invention. The issues to be resolved are
the NF.sub.3 flow rate and the clean duration. Because reduction in
NF.sub.3 consumption is one of the desirable goals of the
invention, increasing the NF.sub.3 appears counterproductive.
[0029] To verify the findings from the design of experiments (DOE),
tests were conducted with varying NF.sub.3 flows and clean
durations. The goal was to identify conditions under which a
particle failure could be created over the course of a five-wafer
deposition run. "Particle failure" means a situation wherein a
wafer shows a high number of particles that exceeds the control
limits, meaning the limit above which the parameter is considered
to have "failed" and requires further investigation and passing
results before production can be resumed. In addition, if there was
a problem with incomplete cleans, a significant separation in the
foreline pressure traces (a plot of the pressure in the foreline as
a function of time) for consecutive wafers could be discerned.
NF.sub.3 flows ranging between 950 sccm to 1,150 sccm were tested.
The results confirm that at the 1,150 setting a particle failure
could not be forced even with a 50% reduction in clean time, unlike
the prior art.
[0030] The next step was to track the evolution of chamber
parameters during the clean, such as foreline pressure, throttle
valve position, chamber pressure, and the like, and correlate the
variation of the parameters with the window clean time and residual
gas analysis (RGA). The foreline is the conduit connecting a
proportional, integral and derivative ("PID") controlled
servo-motor to the chamber. The proportional, integral and
derivative ("PID") controlled servo-motor is used to reduce the
pressure in the chamber from atmospheric pressure (760 torr, or 1
atmosphere) to the operating pressure (3 torr, or 200
torr)--depending on whether it is the clean operation or the
deposition process.
[0031] The residual gas analysis (RGA) allows identification of the
gaseous species present in the chamber. The RGA was hooked up to
the foreline just below the chamber, and 200 AMU (atomic mass
units) runs were conducted to determine which species showed
significant changes in partial pressure during the clean. The
critical species were identified as SiF.sub.x, HF, F.sub.x and
BF.sub.x. While this list not all-inclusive, these species provide
a very good estimate of the clean endpoint as will be demonstrated
below.
[0032] Referring to FIGS. 4a and 4b,it can be seen that the
foreline pressure during the clean provides a reproducible means of
tracking the evolution of the clean. JMP was used to identify an
excellent correlation between the window clean time and the
2.sup.nd peak in the foreline pressure. Both parameters exhibit a
linear variation with film thickness. The foreline pressure
exhibits a change in slope, which coincides with stabilization of
F.sub.2, HF, SiF.sub.4, and BF.sub.3, as can be seen in FIG.
4a.
[0033] Referring to FIG. 4b, to verify the completion of a clean,
an alternative approach is to fix the setting of the throttle valve
position to the value required to achieve the desired pressure
during the main clean, and to observe the variation of the chamber
pressure. As can be seen in FIG. 4b,the chamber pressure can be
seen to stabilize at the same time as seen in the experiments with
the RGA.
[0034] Having optimized the clean recipe in terms of etch rate and
clean duration, twenty five wafer verification runs were completed
for the complete range of BSG and BPSG films at the optimized rate
and duration as indicated in FIG. 5. Optimized rate and duration is
dependent upon film thickness and the film chemistry, for example,
BSG or BPSG. The films tested include 9,000 .ANG. BSG, 7,000 .ANG.
BSG, 2,600 .ANG. BSG, 5,500 .ANG. BPSG, 11,000 .ANG. BPSG and
16,500 .ANG. BPSG. All the film properties were stable and particle
performance was stellar. The etch rate of the method of the
invention will typically be about 20% higher than that of the prior
art.
[0035] FIG. 5 shows the preferred parameters for the methods of the
invention. It provides details of what each of the parameters on an
AMAT Centura 5200 should be set up for the "optimized" clean. Novel
preferred values for various parameters are shown in bold. To
generate the chart, the clean was done after every wafer for the
BSG films and every two wafers for BPSG. In general, the clean will
be implemented perhaps every three wafers for BPSG.
[0036] Referring to FIG. 5, steps 1 and 2, note that a NF.sub.3
Pump and Ar Strike, are identical to the prior art. Step 3, the
NF.sub.3 Ramp is altered according to the invention by raising the
flow rate of Ar above the 1400 sccm level typical of the prior art.
It can be seen from the figure that this will be true for each of
steps 3 through 6. In general, a first mass-flow controller will
regulate the Ar rate which will be greater than 1,400 sccm,
preferably greater than 1,500, more preferably from about 1,500 to
about 1,800, or from about 1,600 to about 1,750 sccm.
[0037] The rate of NF.sub.3 flow is also increased over the prior
art, but only for steps 3 through 5. The standard prior art flow
rate for NF.sub.3 for these steps in 950 sccm. For the method of
the invention, a second mass-flow controller will regulate the
NF.sub.3 rate which will generally be greater than 950 sccm,
preferably at least 1,000 sccm, still more preferably from about
1,100 to about 1,200 sccm, or generally about 1,150 sccm.
[0038] Note in Step 4, the Clean, the chamber pressure is elevated
above the 2.2 torr typical of the prior art. In general, the
chamber pressure will be above 2.2 torr, preferably between 2.5 and
4.5 torr, or about 3 torr.
[0039] Referring again to FIG. 5, note that in steps 5 through 9,
the heater space controller is set so that heater spacing is
elevated over the 600 mils typical of the prior art. This is
optional, but will enhance performance further. The preferred range
for the heater space controller for the invention is from greater
than 600 to about 1,500 mils.
[0040] Note that in Steps 4 and 5, the maximum step time is labeled
TBD, meaning To Be Determined. This is because the duration of
these steps is a function of the type of film (BSG takes longer
than BPSG) and the film thickness. This is true for the prior art
as well, but the method of this invention will generally show step
times about 20% to 30% shorter than the prior art.
[0041] The temperature used was 480.degree. C., but of course any
temperature effective in removing the film is within the range of
the invention. The actual temperature used will depend on the
temperature used for deposition process. Ideally, a temperature
control sets the temperature for the clean processes to be about
identical to the temperature set for the deposition processes so
that there is no impact on the repeatability of the film properties
from one wafer to the next.
[0042] It is to be understood that all physical quantities
disclosed herein, unless explicitly indicated otherwise, are not to
be construed as exactly equal to the quantity disclosed, but rather
as about equal to the quantity disclosed. Further, the mere absence
of a qualifier such as "about" or the like, is not to be construed
as an explicit indication that any such disclosed physical quantity
is an exact quantity, irrespective of whether such qualifiers are
used with respect to any other physical quantities disclosed
herein.
[0043] Referring to an embodiment in FIG. 6 for the clean process,
the inside of a chamber 602 is pressured controlled, preferably
between 2.5 torr and 4.5 torr to about 3.0 torr, by a PID servo
device 604. Connected to the chamber 602 is a first mass-flow
device 608 for introducing Ar into the chamber 602. The Ar provides
a more stable plasma at higher NF.sub.3 flow rates. Further, to
strengthen the etch rate by controlling NF.sub.3 flow rate,
connected to the chamber 602 is a second mass-flow device 606 for
introducing NF.sub.3 into the chamber 602. Increasing heater
spacing also can increase etch rate. Therefore, within the chamber
602 is a heater spacing device 612 that can adjustably space a
heater 614 relative to the chamber 602. A temperature control 610
can adjust the temperature within the chamber 602 so that the clean
processes' temperature is substantially identical to the
temperature set for the deposition processes. The result is that
there is no impact on the repeatability of the film properties from
one wafer to the next.
[0044] While preferred embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. Accordingly,
it is to be understood that the present invention has been
described by way of illustration only, and such illustrations and
embodiments as have been disclosed herein are not to be construed
as limiting to the claims.
[0045] The teachings of the present disclosure are preferably
implemented as a combination of hardware and software. Moreover,
the software is preferably implemented as an application program
tangibly embodied on a program storage unit. The application
program may be uploaded to, and executed by, a machine comprising
any suitable architecture. Preferably, the machine is implemented
on a computer platform having hardware such as one or more Central
Processing Units ("CPUs"), a Random Access Memory ("RAM"), and
Input/Output ("I/O") interfaces. The computer platform may also
include an operating system and microinstruction code. The various
processes and functions described herein may be either part of the
microinstruction code or part of the application program, or any
combination thereof, which may be executed by a CPU. In addition,
various other peripheral units may be connected to the computer
platform such as an additional data storage unit and an output
unit.
[0046] It is to be further understood that, because some of the
constituent system components and steps depicted in the
accompanying drawings may be implemented in software, the actual
connections between the system components or the process function
blocks may differ depending upon the manner in which the present
disclosure is programmed. Given the teachings herein, one of
ordinary skill in the pertinent art will be able to contemplate
these and similar implementations or configurations of the present
disclosure.
[0047] Although illustrative embodiments have been described herein
with reference to the accompanying drawings, it is to be understood
that the present disclosure is not limited to those precise
embodiments, and that various changes and modifications may be
effected therein by one of ordinary skill in the pertinent art
without departing from the scope or spirit of the present
disclosure. All such changes and modifications are intended to be
included within the scope of the present disclosure as set forth in
the appended claims.
* * * * *