U.S. patent application number 16/559979 was filed with the patent office on 2021-03-04 for hybrid wavelength-division multiplexing filters.
The applicant listed for this patent is GLOBALFOUNDRIES Inc., KHALIFA UNIVERSITY OF SCIENCE AND TECHNOLOGY. Invention is credited to Yusheng Bian, Sujith Chandran, Marcus Dahlem, Ajey Poovannummoottil Jacob, Bruna Paredes, Jaime Viegas.
Application Number | 20210063655 16/559979 |
Document ID | / |
Family ID | 1000004317436 |
Filed Date | 2021-03-04 |
United States Patent
Application |
20210063655 |
Kind Code |
A1 |
Chandran; Sujith ; et
al. |
March 4, 2021 |
HYBRID WAVELENGTH-DIVISION MULTIPLEXING FILTERS
Abstract
Structures for a wavelength-division multiplexing filter and
methods of fabricating a structure for a wavelength-division
multiplexing filter. The structure includes a first waveguide core,
a second waveguide core laterally spaced from the first waveguide
core, and a ring resonator arranged in a vertical direction over
the first waveguide core and the second waveguide core. The ring
resonator is also arranged in a lateral direction between the first
waveguide core and the second waveguide core. The first and second
waveguide cores are composed of a semiconductor material, such as
single-crystal silicon, and the ring resonator is composed of a
dielectric material, such as silicon nitride.
Inventors: |
Chandran; Sujith;
(Thiruvananthapuram, IN) ; Dahlem; Marcus; (S. M.
Feira, PT) ; Jacob; Ajey Poovannummoottil;
(Watervliet, NY) ; Bian; Yusheng; (Ballston Lake,
NY) ; Paredes; Bruna; (Abu Dhabi, AE) ;
Viegas; Jaime; (Abu Dhabi, AE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GLOBALFOUNDRIES Inc.
KHALIFA UNIVERSITY OF SCIENCE AND TECHNOLOGY |
Grand Cayman
ABU DHABI |
|
KY
AE |
|
|
Family ID: |
1000004317436 |
Appl. No.: |
16/559979 |
Filed: |
September 4, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/29338 20130101;
G02B 6/4215 20130101 |
International
Class: |
G02B 6/42 20060101
G02B006/42; G02B 6/293 20060101 G02B006/293 |
Claims
1. A structure for a wavelength-division multiplexing filter, the
structure comprising: a first waveguide core; a second waveguide
core laterally spaced from the first waveguide core; and a ring
resonator over the first waveguide core and the second waveguide
core, the ring resonator including a first waveguide ring and a
second waveguide ring laterally between the first waveguide core
and the second waveguide core, the first waveguide ring having a
first non-overlapping relationship with the first waveguide core,
and the second waveguide ring having a second non-overlapping
relationship with the second waveguide core, wherein the first
waveguide core and the second waveguide core comprise a
semiconductor material, and the first waveguide ring and the second
waveguide ring of the ring resonator comprise a dielectric
material.
2. (canceled)
3. The structure of claim 1 wherein the first waveguide ring is
spaced from the second waveguide ring by a perpendicular distance
that is less than a minimum distance for optical signal transfer
between the first waveguide ring and the second waveguide ring.
4. The structure of claim 1 wherein the first waveguide core is
spaced from the first waveguide ring by a first perpendicular
distance that is less than a minimum distance for optical signal
transfer between the first waveguide core and the first waveguide
ring.
5. The structure of claim 4 wherein the second waveguide core is
spaced from the second waveguide ring by a second perpendicular
distance that is less than a minimum distance for optical signal
transfer between the second waveguide ring and the second waveguide
core.
6. The structure of claim 1 wherein the first waveguide core and
the second waveguide core have a first thickness, the first
waveguide ring and the second waveguide ring have a second
thickness, and the second thickness is greater than the first
thickness.
7. The structure of claim 1 wherein the first waveguide ring and
the second waveguide ring of the ring resonator are
serially-coupled.
8. The structure of claim 1 wherein the dielectric material is
silicon nitride, and the semiconductor material is single-crystal
silicon.
9. The structure of claim 1 further comprising: one or more
dielectric layers between the ring resonator and the first
waveguide core and between the ring resonator and the second
waveguide core.
10. The structure of claim 1 further comprising: a first optical
component coupled with the first waveguide core; and a second
optical component coupled with the second waveguide core.
11. The structure of claim 10 wherein the first optical component
is a photodetector.
12. The structure of claim 11 wherein the second optical component
is a laser.
13. The structure of claim 1 further comprising: a resistive heater
configured to be operated to transfer heat to the structure.
14. The structure of claim 1 wherein the first waveguide core is
substantially straight and has a first longitudinal axis, the
second waveguide core is substantially straight and has a second
longitudinal axis, and the second longitudinal axis is aligned
substantially parallel to the first longitudinal axis.
15. A method of forming a wavelength-division multiplexing filter,
the method comprising: patterning a semiconductor layer to form a
first waveguide core and a second waveguide core laterally spaced
from the first waveguide core; depositing a first dielectric layer
over the first waveguide core and the second waveguide core; and
patterning the first dielectric layer to form a ring resonator that
is laterally between the first waveguide core and the second
waveguide core, wherein the ring resonator includes a first
waveguide ring and a second waveguide ring arranged adjacent to the
first waveguide ring, the first waveguide ring has a first
non-overlapping relationship with the first waveguide core, the
second waveguide ring has a second non-overlapping relationship
with the second waveguide core, the first waveguide core and the
second waveguide core comprise a semiconductor material, and the
first waveguide ring and the second waveguide ring of the ring
resonator comprise a dielectric material.
16. (canceled)
17. The method of claim 15 wherein the first waveguide core is
coupled with a photodetector.
18. The method of claim 17 wherein the second waveguide core is
coupled with a laser.
19. The method of claim 15 further comprising: forming one or more
second dielectric layers between the ring resonator and the first
waveguide core and between the ring resonator and the second
waveguide core, wherein the first dielectric layer is deposited on
the one or more second dielectric layers.
20. The method of claim 15 wherein the dielectric material is
silicon nitride, and the semiconductor material is single-crystal
silicon.
21. The structure of claim 1 wherein the ring resonator only
includes the first waveguide ring and the second waveguide
ring.
22. The structure of claim 1 wherein the first waveguide ring has a
first width and a first thickness selected to match the effective
refractive index of the first waveguide ring to the effective
refractive index of the first waveguide core, and the second
waveguide ring has a second width and a second thickness selected
to match the effective refractive index of the second waveguide
ring to the effective refractive index of the second waveguide
core.
Description
BACKGROUND
[0001] The present invention relates to photonics chips and, more
specifically, to structures for a wavelength-division multiplexing
filter and methods of fabricating a structure for a
wavelength-division multiplexing filter.
[0002] Photonics chips are used in many applications and systems
including, but not limited to, data communication systems and data
computation systems. A photonics chip integrates multiple optical
components, such as waveguides and optical switches, and multiple
electronic components, such as field-effect transistors, into a
unified platform. Among other factors, layout area, cost, and
operational overhead may be reduced by the integration of both
types of components on the same chip.
[0003] Wavelength-division multiplexing is a technology that
multiplexes multiple data streams onto a single optical link. In a
wavelength-division multiplexing scheme, a set of data streams is
encoded onto optical carrier signals with a different wavelength of
laser light for each data stream. These optical carrier signals of
the individual data streams are then combined in an optical
wavelength-division multiplexing filter, which has a dedicated
input for the data stream of each wavelength and a single output at
which the individual data streams are combined (i.e., multiplexed)
into a single multi-wavelength data stream for further transport
through a single optical link. At the receiver side of the optical
data link, a wavelength-division multiplexing filter of the same
type, but used in reverse, separates (i.e., de-multiplexes) the
optical carrier signals of the individual data streams and the
separated optical carrier signals to corresponding optical
detectors.
[0004] Wavelength-division multiplexing filters fabricated from
silicon are extremely sensitive to temperature drift due to the
relatively high thermal optical coefficient of silicon.
Silicon-based wavelength-division multiplexing filters may rely on
resistive heaters in an attempt to control the temperature shift.
However, the addition of resistive heaters adds complexity to not
only device fabrication, but also to device operation due to the
need to control the operation of the resistive heaters. In
addition, the resistive heaters require the dissipation of high
amounts of power to provide the requisite heating for temperature
shift control.
[0005] Improved structures for a wavelength-division multiplexing
filter and methods of fabricating a structure for a
wavelength-division multiplexing filter are needed.
SUMMARY
[0006] In an embodiment of the invention, a structure for a
wavelength-division multiplexing filter is provided. The structure
includes a first waveguide core, a second waveguide core, and a
ring resonator arranged in a vertical direction over the first
waveguide core and the second waveguide core and in a lateral
direction between the first waveguide core and the second waveguide
core. The first waveguide core and the second waveguide core are
composed of a semiconductor material, and the ring resonator is
composed of a dielectric material, such as silicon nitride.
[0007] In an embodiment of the invention, a method of forming a
wavelength-division multiplexing filter is provided. The method
includes patterning a semiconductor layer to form a first waveguide
core and a second waveguide core, depositing a dielectric layer
over the first waveguide core and the second waveguide core, and
patterning the dielectric layer to form a ring resonator arranged
in a lateral direction between the first waveguide core and the
second waveguide core. The first waveguide core and the second
waveguide core are composed of a semiconductor material, and the
ring resonator is composed of a dielectric material, such as
silicon nitride.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate various
embodiments of the invention and, together with a general
description of the invention given above and the detailed
description of the embodiments given below, serve to explain the
embodiments of the invention. In the drawings, like reference
numerals refer to like features in the various views.
[0009] FIG. 1 is a simplified diagrammatic top view of a structure
at an initial fabrication stage of a processing method in
accordance with embodiments of the invention.
[0010] FIG. 2 is a cross-sectional view taken generally along line
2-2 in FIG. 1.
[0011] FIG. 3 is a cross-sectional view taken generally along line
3-3 in FIG. 1.
[0012] FIGS. 4 and 5 are cross-sectional views of the structure at
successive fabrication stages of the processing method respectively
subsequent to FIGS. 2 and 3.
DETAILED DESCRIPTION
[0013] With reference to FIGS. 1, 2, 3 and in accordance with
embodiments of the invention, a structure 10 for a
wavelength-division multiplexing filter includes a waveguide core
12 and a waveguide core 14 arranged over a dielectric layer 16. The
waveguide core 12 extends in a strip along a longitudinal axis 18
over the portion of the waveguide core 12 involved in the structure
10 and provides a bus waveguide along which multiplexed data
streams encoded into optical signals of different wavelength may
propagate. The waveguide core 12 may provide an input port to the
structure 10, and may be coupled with one or more optical
components 19, such as one or more lasers generating the optical
signals at the different wavelengths. The waveguide core 14 extends
over a finite portion of its length along a longitudinal axis 20,
and the waveguide core 14 may provide a local waveguide section
coupled with an optical component 21, such as a photodetector. The
portion of the waveguide core 14 may provide an output port from
the structure 10. The waveguide core 14 has a length and a shape
that are sufficient to be connected with the optical component 21.
The longitudinal axis 18 may be aligned substantially parallel to
the longitudinal axis 20.
[0014] The waveguide core 12 includes sidewalls in the form of side
surfaces 22, 24 that project in a vertical direction from the
dielectric layer 16. The side surfaces 22, 24 may be substantially
linear or straight over the section of the waveguide core 12
involved in the structure 10 such that the section of the waveguide
core 12 is substantially linear or straight. The side surfaces 22,
24 may be vertical, as shown, or may be angled inwardly such that
the waveguide core 12 has a trapezoidal cross-sectional profile.
Similarly, the waveguide core 14 includes sidewalls in the form of
side surfaces 26, 28 that project in a vertical direction from the
dielectric layer 16. The side surfaces 26, 28 may be substantially
linear or straight over the section of the waveguide core 14
involved in the structure 10 such that the section of the waveguide
core 14 is substantially linear or straight. The side surfaces 26,
28 may be vertical, as shown, or may be angled inwardly such that
the waveguide core 14 has a trapezoidal cross-sectional profile.
The waveguide cores 12, 14 each have a width, w1.
[0015] The waveguide cores 12, 14 may be composed of a
single-crystal semiconductor material, such as single-crystal
silicon and, in particular, single-crystal silicon originating from
a device layer of a silicon-on-insulator (SOI) wafer. The
silicon-on-insulator wafer further includes a buried insulator
layer composed of a dielectric material, such as silicon dioxide,
that provides the dielectric layer 16 and a substrate 30 composed
of a single-crystal semiconductor material, such as single-crystal
silicon, under the buried insulator layer. The waveguide cores 12,
14 may be patterned from a layer of single-crystal semiconductor
material (e.g., the device layer of the SOI wafer) by lithography
and etching processes, and may have equal thicknesses, t1, to
provide coplanarity.
[0016] Dielectric layers 32, 34, 36, 38 composed of respective
dielectric materials are sequentially formed in a layer stack over
the waveguide cores 12, 14. In the layer stack, the dielectric
layer 32 is arranged over the dielectric layer 16, the dielectric
layer 34 is arranged over the dielectric layer 32, the dielectric
layer 36 is arranged over the dielectric layer 34, and the
dielectric layer 38 is arranged over the dielectric layer 36. The
waveguide cores 12, 14 are embedded or buried in the dielectric
material of the dielectric layer 32, which acts as lateral
cladding. In particular, the dielectric material of the dielectric
layer 32 is located in the space between the embedded waveguide
cores 12, 14.
[0017] The dielectric layer 32 may be composed of a dielectric
material, such as silicon dioxide, deposited by chemical vapor
deposition and planarized with, for example, chemical mechanical
polishing to remove topography. The dielectric layer 34 may be
composed of dielectric material, such as silicon dioxide, deposited
by chemical vapor deposition or atomic layer deposition over the
dielectric layer 32. The dielectric layer 36 may be composed of
dielectric material, such as silicon nitride, deposited by chemical
vapor deposition or atomic layer deposition over the dielectric
layer 34. The dielectric layer 38 may be composed of dielectric
material, such as silicon dioxide, deposited by chemical vapor
deposition or atomic layer deposition over the dielectric layer 36.
The dielectric layers 34, 36, 38 may be planar layers arranged in
the layer stack over the planarized top surface of the dielectric
layer 32. In the top view of FIG. 1, the dielectric layers 32, 34,
36, 38 are omitted for clarity of depiction.
[0018] A ring resonator 40 is formed over the dielectric layer 38
in a space laterally between the underlying waveguide core 12 and
waveguide core 14, and vertically over the dielectric layer 38. The
ring resonator 40 may include a waveguide ring 42 and a waveguide
ring 44 that are arranged in a spaced arrangement between the
waveguide cores 12, 14. In an embodiment, the ring resonator 40 may
be a second-order filter that includes only two waveguide rings 42,
44. In an embodiment, the waveguide rings 42, 44 may be serially
coupled. In alternative embodiments, the ring resonator 40 may
include additional waveguide rings. The waveguide rings 42, 44 may
be composed of a dielectric material, such as silicon nitride. The
waveguide rings 42, 44 may be patterned from a layer of the
constituent dielectric material by lithography and etching
processes during front-end-of-line processing, and may have equal
thicknesses, t2, to provide coplanarity.
[0019] The waveguide ring 42 has an inner sidewall or side surface
45 and an outer sidewall or side surface 46 at a given outer
radius, r1, from its center. The side surfaces 45, 46 may be
vertical, as shown, or may be angled inwardly such that the
waveguide ring 42 has a trapezoidal cross-sectional profile. The
waveguide ring 44 has an inner sidewall or side surface 47 and an
outer sidewall or side surface 48 at a given outer radius, r2, from
its center. The side surfaces 47, 48 may be vertical, as shown, or
may be angled inwardly such that the waveguide ring 44 has a
trapezoidal cross-sectional profile. In an embodiment, the outer
radii of the waveguide rings 42, 44 may be equal or substantially
equal, and may be increased or decreased as a factor to assist in
selecting the resonance wavelengths.
[0020] The waveguide rings 42, 44 are arranged in a different level
of the structure 10 than the level containing the waveguide cores
12, 14. The waveguide rings 42, 44 are arranged as coplanar
features in an upper level of the structure 10, and the waveguide
cores 12, 14 are arranged as coplanar features in a lower level of
the structure 10. The waveguide ring 42 defines a closed loop in
which the waveguide ring 42 is spaced from the waveguide core 12 at
their closest separation by a perpendicular distance, d1. The
perpendicular distance, d1, is less than a minimum distance needed
to permit optical signal transfer between the waveguide core 12 and
the waveguide ring 42. The waveguide ring 44 defines a closed loop
in which the waveguide ring 44 is spaced from the waveguide core 14
at their closest separation by a perpendicular distance, d2. The
perpendicular distance, d2, is less than a minimum distance needed
to permit optical signal transfer between the waveguide core 14 and
the waveguide ring 44. The waveguide ring 42 is arranged adjacent
to the waveguide ring 44, and the waveguide ring 42 is laterally
offset or spaced from the waveguide ring 44 by a perpendicular
distance, d3, at their closest separation between their respective
side surfaces 44, 46. The perpendicular distance, d3, is less than
a minimum distance needed to permit optical signal transfer between
the waveguide ring 42 and the waveguide ring 44. The respective
perpendicular distances are distances from one object to the other,
measured along a line that is perpendicular to one or both objects.
The perpendicular distances d1 and d2 are not measured in the plane
of the waveguide rings 42, 44 or in the plane of the waveguide
cores 12, 14, but are instead measured between these different
planes. The perpendicular distance d3 is measured in the plane of
the waveguide rings 42, 44.
[0021] The multiple-level arrangement of the waveguide rings 42, 44
relative to the waveguide cores 12, 14 permits flexible placement
of the waveguide core 12 relative to the waveguide ring 42 and the
waveguide core 14 relative to the waveguide ring 44. In the
representative embodiment, the waveguide core 12 and the waveguide
ring 42 are arranged with a non-overlapping relationship, and the
waveguide core 14 and the waveguide ring 44 are also arranged with
a non-overlapping relationship. In an alternative embodiment, the
waveguide core 12 and the waveguide ring 42 may be arranged with an
overlapping relationship, and the waveguide core 14 and the
waveguide ring 44 may also be arranged with an overlapping
relationship. In an alternative embodiment, the side surface 24 of
the waveguide core 12 may be arranged directly under the side
surface 46 of waveguide ring 42, and the side surface 26 of the
waveguide core 14 may also be arranged directly under the side
surface 48 of waveguide ring 44.
[0022] In an embodiment, the waveguide ring 42 may have a width,
w2, and the waveguide ring 44 may have a width, w3, that are each
greater than the widths, w1, of the waveguide cores 12, 14. In an
embodiment, the width, w2, of the waveguide ring 42 may be
substantially equal to the width, w3, of the waveguide ring 44 such
that their inner and outer radii are both substantially equal. In
an embodiment, waveguide rings 42, 44 may have a thickness, t2,
that is greater than the thickness, t1, of the waveguide cores 12,
14. The widths and thickness of the waveguide rings 42, 44 may be
selected to match the effective refractive index of the waveguide
rings 42, 44 to the effective refractive index of the waveguide
cores 12, 14.
[0023] In use, the waveguide core 12 may guide a set of data
streams encoded onto optical carrier signals with a different
wavelength of laser light for each data stream as input to the ring
resonator 40. The particular optical carrier signals in the set
having a wavelength that meets the resonance condition of the
waveguide ring 42 will couple into the waveguide ring 42 and, after
transfer, circulate within the waveguide ring 42. The wavelength of
the particular optical carrier signals may also meet the resonance
condition of the waveguide ring 42 and couple into the waveguide
ring 44 or, alternatively, the loops around the waveguide ring 42
may bring the wavelength of the particular optical carrier signals
to the resonance condition of the waveguide ring 44. After
transfer, the particular optical carrier signals circulate within
the waveguide ring 44. The wavelength of the particular optical
carrier signals may also meet the resonance condition of the
waveguide ring 44 and couple into the waveguide core 14 or,
alternatively, the loops around the waveguide ring 44 may bring the
wavelength of the particular optical carrier signals to the
resonance condition of the waveguide ring 44 for coupling into the
waveguide core 14.
[0024] With reference to FIGS. 4, 5 in which like reference
numerals refer to like features in FIGS. 2, 3 and at a subsequent
fabrication stage, a dielectric layer 54 of a contact level is
formed by middle-of-line processing over the dielectric layer 38.
The dielectric layer 54 may be composed of dielectric material,
such as silicon dioxide, deposited by chemical vapor deposition
using ozone and tetraethylorthosilicate (TEOS) as reactants.
[0025] A back-end-of-line stack, generally indicated by reference
numeral 56, is formed by back-end-of-line processing over the
dielectric layer 54 and the structure 10. The back-end-of-line
stack 56 may include one or more interlayer dielectric layers
composed of one or more dielectric materials, such as a
carbon-doped silicon oxide, and metallization composed of, for
example, copper, tungsten, and/or cobalt that is arranged in the
one or more interlayer dielectric layers.
[0026] The structure 10 may have an entirely passive construction
that lacks heaters. In an alternative embodiment, one or more
resistive heaters 50 may be fabricated in the dielectric layer 54
or in the back-end-of-line stack 56, and may be operated to provide
thermal tuning to compensate for fabrication imperfections. The one
or more resistive heaters 50 may also be fabricated as silicide
heaters using the same semiconductor layer as used to fabricate the
waveguide cores 12, 14. The one or more resistive heaters 50 are
connected with a control circuit that outputs regulated power
supplied to the one or more resistive heaters 50.
[0027] The structure 10, in any of the embodiments described
herein, may be integrated into a photonics chip that includes
electronic components and additional optical components formed on
the same chip. For example, the electronic components may include
field-effect transistors that are fabricated by CMOS
front-end-of-line (FEOL) processing.
[0028] The structure 10 provides a composite or hybrid
wavelength-division multiplexing filter based on bus waveguides
composed of a semiconductor material (e.g., single-crystal silicon)
and a ring resonator composed of a dielectric material (e.g.,
silicon nitride). The material of the bus waveguides enables
compact routing, and the material of the ring resonator provides
for a low thermal dependence. The structure 10 may overcome the
minimum feature design rule limitation for optimal design filter
bandwidth. Multiple replicas of the ring resonator 40, each with a
waveguide ring 42 tuned with a different resonance wavelength, may
be used to transfer multiplexed data streams encoded into optical
carrier signals of different wavelength may propagate
[0029] The methods as described above are used in the fabrication
of integrated circuit chips. The resulting integrated circuit chips
can be distributed by the fabricator in raw wafer form (e.g., as a
single wafer that has multiple unpackaged chips), as a bare die, or
in a packaged form. The chip may be integrated with other chips,
discrete circuit elements, and/or other signal processing devices
as part of either an intermediate product or an end product. The
end product can be any product that includes integrated circuit
chips, such as computer products having a central processor or
smartphones.
[0030] References herein to terms modified by language of
approximation, such as "about", "approximately", and
"substantially", are not to be limited to the precise value
specified. The language of approximation may correspond to the
precision of an instrument used to measure the value and, unless
otherwise dependent on the precision of the instrument, may
indicate +/-10% of the stated value(s).
[0031] References herein to terms such as "vertical", "horizontal",
etc. are made by way of example, and not by way of limitation, to
establish a frame of reference. The term "horizontal" as used
herein is defined as a plane parallel to a conventional plane of a
semiconductor substrate, regardless of its actual three-dimensional
spatial orientation. The terms "vertical" and "normal" refer to a
direction perpendicular to the horizontal, as just defined. The
term "lateral" refers to a direction within the horizontal
plane.
[0032] A feature "connected" or "coupled" to or with another
feature may be directly connected or coupled to or with the other
feature or, instead, one or more intervening features may be
present. A feature may be "directly connected" or "directly
coupled" to or with another feature if intervening features are
absent. A feature may be "indirectly connected" or "indirectly
coupled" to or with another feature if at least one intervening
feature is present. A feature "on" or "contacting" another feature
may be directly on or in direct contact with the other feature or,
instead, one or more intervening features may be present. A feature
may be "directly on" or "in direct contact with" another feature if
intervening features are absent. A feature may be "indirectly on"
or "in indirect contact with" another feature if at least one
intervening feature is present.
[0033] The descriptions of the various embodiments of the present
invention have been presented for purposes of illustration, but are
not intended to be exhaustive or limited to the embodiments
disclosed. Many modifications and variations will be apparent to
those of ordinary skill in the art without departing from the scope
and spirit of the described embodiments. The terminology used
herein was chosen to best explain the principles of the
embodiments, the practical application or technical improvement
over technologies found in the marketplace, or to enable others of
ordinary skill in the art to understand the embodiments disclosed
herein.
* * * * *