U.S. patent application number 15/069496 was filed with the patent office on 2017-09-14 for optical module and a detection method.
The applicant listed for this patent is APPLIED MATERIALS ISRAEL LTD.. Invention is credited to Tal Kuzniz.
Application Number | 20170261713 15/069496 |
Document ID | / |
Family ID | 59758611 |
Filed Date | 2017-09-14 |
United States Patent
Application |
20170261713 |
Kind Code |
A1 |
Kuzniz; Tal |
September 14, 2017 |
OPTICAL MODULE AND A DETECTION METHOD
Abstract
An optical module that includes (a) an optical interface that
includes an input surface and an output surface, and (b) a
scintillator that has a flat surface. The scintillator is
configured emit emitted light through the flat surface in response
to an impingement of a charged particle on the scintillator. The
flat surface is optically coupled to the input surface. The optical
interface is configured to (i) receive the emitted light from the
scintillator and (ii) output, via the output surface, output light.
An optical interface refractive index substantially equals a
scintillator refractive index.
Inventors: |
Kuzniz; Tal; (Kfar-Saba,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
APPLIED MATERIALS ISRAEL LTD. |
Rehovot |
|
IL |
|
|
Family ID: |
59758611 |
Appl. No.: |
15/069496 |
Filed: |
March 14, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01T 1/10 20130101; G02B
27/30 20130101; G02B 6/4212 20130101; G02B 19/0076 20130101; G02B
19/0028 20130101; G02B 6/4298 20130101; G02B 6/4214 20130101 |
International
Class: |
G02B 6/42 20060101
G02B006/42; G01T 1/10 20060101 G01T001/10; G02B 27/30 20060101
G02B027/30 |
Claims
1. (canceled)
2. The optical module according to claim 9 wherein the output light
exits through a region of the output surface at an angle, in
relation to the region of the output surface, that ranges between
70 and 110 degrees.
3. The optical module according to claim 9 wherein the flat surface
contacts the input surface.
4. The optical module according to claim 9 wherein the optical
interface comprises a parabolic mirror that is configured to
collimate the emitted light towards the output surface.
5. The optical module according to claim 9 wherein the output
surface is shaped as a segment of a three dimensional sphere.
6. The optical module according to claim 9 wherein the output
surface has a linear shape.
7. The optical module according to claim 9 wherein the output
surface has a non-linear shape.
8. The optical module according to claim 9 wherein the optical
interface refractive index equals the scintillator refractive
index.
9. An optical module, comprising: an optical interface having an
optical refractive index, the optical interface comprises an input
surface and an output surface; and a scintillator comprising a flat
surface optically coupled to the input surface and being configured
to emit emitted light through the flat surface in response to an
impingement of a charged particle on the scintillator; wherein the
optical interface is configured to (i) receive the emitted light
from the scintillator and (ii) output, via the output surface,
output light and wherein at least one of the following is true: (a)
the optical interface forms at least a part of a light guide, (b)
the input surface is coupled to the flat surface by optical contact
coupling, or (c) the input surface is attached to the flat surface
by an adhesive material that has an adhesive material refraction
index that is substantially equal to the scintillator refractive
index; and wherein the optical interface refractive index differs
from the scintillator refractive index by up to 10 percent.
10. The optical module according to claim 9 herein the input
surface is oriented in relation to the output surface.
11. The optical module according to claim 9 wherein the optical
interface and the scintillator are made of Sapphire.
12. A method for detection, the method comprises: emitting, through
a flat surface of a scintillator that as a scintillator refractive
index, emitted light; wherein the emitting of the emitted light is
responsive to an impingement of a charged particle on the
scintillator; receiving, via an input surface of an optical
interface that has an optical refractive index, the emitted light;
outputting, via an output surface of the optical interface, output
light through a region of the output surface at an angle, in
relation to the region of the output surface, that ranges between
70 and 110 degrees; wherein the optical interface refractive index
differs from the scintillator refractive index by up to 10 percent;
and wherein at least one of the following is true: (a) the optical
interface forms at least a part of a light guide, or (b) the output
surface of the optical interface directly contacts a portion of the
light guide.
13. The method according to claim 12 wherein the optical interface
comprises a parabolic mirror that is configured to collimate the
emitted light towards the output surface.
14. The method according to claim 12 wherein the output light exits
through a region of the output surface at an angle, in relation to
the region of the output surface, that ranges between 70 and 110
degrees.
15. The method according to claim 12 wherein the flat surface
contacts the input surface.
16. The optical module according to claim 9 wherein the optical
interface forms at least a part of a light guide.
17. The optical module according to claim 9 wherein the input
surface is coupled to the flat surface by an optical contact
coupling.
18. The optical module according to claim 9 wherein the input
surface is attached to the flat surface by an adhesive material
that has an adhesive material refraction index that is
substantially equal to the scintillator refractive index.
Description
BACKGROUND OF THE INVENTION
[0001] A scintillator (www.wikipedia.org) is a material that
exhibits scintillation--the property of luminescence when excited
by ionizing radiation. Luminescent materials, when struck by an
incoming particle, absorb its energy and scintillate, (i.e.,
re-emit the absorbed energy in the form of light). Sometimes, the
excited state is metastable, so the relaxation back down from the
excited state to lower states is delayed (necessitating anywhere
from a few nanoseconds to hours depending on the material): the
process then corresponds to either one of two phenomena, depending
on the type of transition and hence the wavelength of the emitted
optical photon: delayed fluorescence or phosphorescence, also
called after-glow.
[0002] Various tools such as scanning electron microscopes and
electron beam inspection tools include a scintillators and a light
guide.
[0003] The scintillator and the light guide are made of different
materials and when the scintillator is flat the optical coupling
between the scintillator to the light guide is problematic and
results in losing a substantial amount of light.
[0004] There is a growing need to collect the light from a
scintillator in an efficient manner.
BRIEF SUMMARY OF THE INVENTION
[0005] According to an embodiment of the invention there may be
provided an optical module that may include (a) an optical
interface that may include an input surface and an output surface;
and (b) a scintillator that may have a flat surface and has a
scintillator refractive index; wherein the scintillator is
configured emit emitted light through the flat surface in response
to an impingement of a charged particle on the scintillator. The
optical interface has an optical interface refractive index. The
flat surface is optically coupled to the input surface. The optical
interface may be configured to (i) receive the emitted light from
the scintillator and (ii) output, via the output surface, output
light. The optical interface refractive index substantially equals
the scintillator refractive index.
[0006] According to an embodiment of the invention there may be
provided a method for detection, the method may include: (a)
emitting, through a flat surface of a scintillator that as a
scintillator refractive index, emitted light; wherein the emitting
of the emitted light is responsive to an impingement of a charged
particle on the scintillator; (b) receiving, via an input surface
of an optical interface, the emitted light; and (c) outputting, via
an output surface of the optical interface, output light. The
optical interface refractive may equal the scintillator refractive
index or differs from the scintillator refractive index by up to
ten percent. The output light exits through a region of the output
surface at an angle, in relation to the region of the output
surface, that ranges between 70 and 110 degrees;
[0007] According to an embodiment of the invention at least one of
the following is true: (a) the optical interface forms at least a
part of a light guide; (b) the input surface is coupled to the flat
surface by optical contact coupling; and (c) the input surface is
attached to the flat surface by an adhesive material that has an
adhesive material refraction index that is substantially equal to
the scintillator refractive index.
[0008] The output light may exit through a region of the output
surface at an angle, in relation to the region of the output
surface that ranges between 70 and 110 degrees.
[0009] The flat surface may contact the input surface.
[0010] The optical interface may include a parabolic mirror that is
configured to collimate the emitted light towards the output
surface.
[0011] The output surface may be shaped as a segment of a three
dimensional sphere.
[0012] The output surface may have a linear shape.
[0013] The output surface may have a non-linear shape.
[0014] The optical interface refractive index may equal the
scintillator refractive index.
[0015] The optical interface refractive index may differ from the
scintillator refractive index by up to 10 percent. A difference of
up till ten percent is still regarded as substantially equal.
[0016] The input surface may be oriented in relation to the output
surface.
[0017] The optical interface and the scintillator can be are made
of Sapphire or of other materials.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The subject matter regarded as the invention is particularly
pointed out and distinctly claimed in the concluding portion of the
specification. The invention, however, both as to organization and
method of operation, together with objects, features, and
advantages thereof, may best be understood by reference to the
following detailed description when read with the accompanying
drawings in which:
[0019] FIG. 1A illustrates an optical module that includes a
scintillator, an interfacing module and a light guide according to
an embodiment of the invention;
[0020] FIG. 1B illustrates an optical module that includes a
scintillator, an interfacing module and a light guide according to
an embodiment of the invention;
[0021] FIG. 2A illustrates an optical module that includes a
scintillator and a light guide according to an embodiment of the
invention;
[0022] FIG. 2B illustrates an optical module that includes a
scintillator and a light guide according to an embodiment of the
invention;
[0023] FIG. 3 illustrates a propagation of light within the optical
module according to an embodiment of the invention;
[0024] FIG. 4A illustrates an optical module that includes a
scintillator, two interfacing modules and two light guides
according to an embodiment of the invention;
[0025] FIG. 4B is a top view of an optical module that includes a
scintillator, four interfacing modules and four light guides
according to an embodiment of the invention;
[0026] FIG. 5 illustrates a system that includes an optical module
according to an embodiment of the invention; and
[0027] FIG. 6 illustrates a method according to an embodiment of
the invention.
[0028] It will be appreciated that for simplicity and clarity of
illustration, elements shown in the Figures have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements may be exaggerated relative to other elements for clarity.
Further, where considered appropriate, reference numerals may be
repeated among the Figures to indicate corresponding or analogous
elements.
DETAILED DESCRIPTION OF THE INVENTION
[0029] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the invention. However, it will be understood by those skilled
in the art that the present invention may be practiced without
these specific details. In other instances, well-known methods,
procedures, and components have not been described in detail so as
not to obscure the present invention.
[0030] The subject matter regarded as the invention is particularly
pointed out and distinctly claimed in the concluding portion of the
specification. The invention, however, both as to organization and
method of operation, together with objects, features, and
advantages thereof, may best be understood by reference to the
following detailed description when read with the accompanying
drawings.
[0031] It will be appreciated that for simplicity and clarity of
illustration, elements shown in the Figures have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements may be exaggerated relative to other elements for clarity.
Further, where considered appropriate, reference numerals may be
repeated among the Figures to indicate corresponding or analogous
elements.
[0032] Because the illustrated embodiments of the present invention
may for the most part, be implemented using electronic components
and circuits known to those skilled in the art, details will not be
explained in any greater extent than that considered necessary as
illustrated above, for the understanding and appreciation of the
underlying concepts of the present invention and in order not to
obfuscate or distract from the teachings of the present
invention.
[0033] Any reference in the specification to a method should be
applied mutatis mutandis to a system capable of executing the
method.
[0034] Any reference in the specification to a system should be
applied mutatis mutandis to a method that may be executed by the
system.
[0035] FIG. 1A illustrates an optical module 21 that includes a
scintillator 30, an optical interface 40 and a light guide 50
according to an embodiment of the invention.
[0036] The optical module can be a stand-alone module, may be a
part of an inspection system, may form a detection module or be a
part of a detection module.
[0037] The optical interface 40 includes an input surface 41 and an
output surface 43.
[0038] The scintillator 30 has a flat surface 32 and is shown as
including another scintillator surface 31. The scintillator 30 has
a scintillator refractive index.
[0039] The flat surface 32 is not substantially bent or curved.
[0040] Scintillator 30 is configured emit emitted light through the
flat surface 32 in response to an impingement of a charged particle
(such as an electron) on the other scintillator surface 31.
[0041] The optical interface 40 has an optical interface refractive
index. The flat surface 32 is optically coupled to the input
surface 41.
[0042] According to an embodiment of the invention the flat surface
32 contacts the input surface 41. The flat surface 32 can contact
the input surface 41 without any adhesive or bonding material
placed between the flat surface 32 and the input surface 41.
[0043] According to an embodiment of the invention the flat surface
32 is coupled to the input surface 41 so there is not gap between
the flat surface 32 and the input surface. Alternatively--even if
such a gap exists the gap is low enough for evanescing fields low
attenuation--for example it does not exceed few tens of nanometers
(for example--below 10, 20, 30 nanometers).
[0044] Any known method for providing optical contact coupling can
be used for coupling the flat surface 32 to input surface 41. For
example--each one of the flat surface 32 and the input surface 41
may be polished to match each other at a nanometer scale (for
example at an accuracy of about half a nanometer).
[0045] When two surfaces (such as flat surface 32 and the input
surface 41) have a gap of less than 1 nm over a relatively large
area (one square millimeter or more) the Van Der Walls forces
between the two surfaces hold the two surfaces to each other. If
both bodies are made of the same material, the interface between
them cannot be observed at all.
[0046] The two surfaces, after being polished are cleaned and are
attached to the other. The attaching process may include driving
any residual gas or liquid positioned between the two surfaces. The
driving out may include spinning one or more of the two surfaces,
heat treatment of one or more of the two surfaces and/or applying
pressure.
[0047] According to an embodiment of the invention the flat surface
32 is connected to the input surface using an adhesive material
that has an adhesion material refractive index that substantially
equals the refractive index of the scintillator.
[0048] Optical interface 40 is configured to (i) receive the
emitted light from the scintillator 30 and (b) output, via the
output surface 43, output light.
[0049] The optical interface refractive index substantially equals
the scintillator refractive index--optical interface refractive
index may either exactly equal the scintillator refractive index or
may differ from the scintillator refractive index by up till ten
percent.
[0050] The output light exits through a region of the output
surface 43 at an angle, in relation to the region of the output
surface 43 that range between 70 and 110 degrees. The region of
output surface includes the point of the output surface 43 through
which the output light exits.
[0051] While the emitted light may exit the input surface 41(and
propagate within optical interface 40) at different angles and
within a large angular range (almost one hundred and eighty
degrees)--the light that exits through the output surface 43 is
substantially normal to the output surface and thus does not
"escape" from the light guide 50.
[0052] According to an embodiment of the invention the output
surface 43 may be curved and may even form a part of a sphere. When
the output surface 43 is shaped as a part of a sphere then then
center of sphere may be proximate to a part of the scintillator
(such as the center of the scintillator) from which light exits.
Light that is emitted from that part of the scintillator and
propagates directly towards the output surface 43 will exit the
output surface 43 at about ninety degrees from the point of
exit.
[0053] Light guide 50 has a light guide input interface 51 that
contacts the output surface 43.
[0054] In FIG. 1A the optical interface 40 includes intermediate
surface 42 in addition to the input surface 41 and to the output
surface 43. The intermediate surface 42 may be configured to
collimate or otherwise reflect light towards the output surface
43.
[0055] In FIG. 1A the intermediate surface 42 is linear.
[0056] FIG. 1B illustrates optical module 22 that includes an
intermediate surface 42 that is shaped as a parabolic mirror.
[0057] The output surface 43 may be linear or non-linear. For
example--the output surface may be shaped as a segment of a three
dimensional sphere.
[0058] While in FIGS. 1A and 1B the optical interface 40 was
connected to light guide 50 it should be noted that the optical
interface 40 may be a part of the light guide 50.
[0059] FIG. 2A illustrates optical module 23. FIG. 2B illustrates
optical module 24.
[0060] FIGS. 1A and 2B illustrate a light guide 60 that has an
input surface 61, an intermediate surface 63 and an output surface
62. The light guide 60 of FIG. 2A is a combination of the optical
interface 40 and the light guide 50 of FIG. 1A. The light guide 60
of FIG. 2B is a combination of the optical interface 40 and the
light guide 50 of FIG. 1B.
[0061] FIG. 3 illustrates the propagation of light within an
optical module 23 that can be, for example, similar to or identical
to optical module 21 shown in FIG. 1A.
[0062] Electron 101 impinges onto scintillator 30. This may result
in an emission of light rays 102 within optical interface 40. A
light ray that is emitted towards the output surface 43 may exit
(as output light 103) the output surface 43. A light ray that is
emitted towards the intermediate surface 42 may be directed (as
output light 103) towards the output surface 43.
[0063] According to various embodiments of the invention different
parts (segments) of the scintillator are optically coupled to
different optical interfaces such as the optical interfaces of
FIGS. 2A or 2B.
[0064] According to various embodiments of the invention different
parts (segments) of the scintillator are optically coupled to
different light guides such as the light guides of FIGS. 2A or
2B.
[0065] FIG. 4A illustrates an optical module 25 that includes a
scintillator 30 and pair of optical interfaces 40 and 240.
[0066] Optical interface 40 is optically coupled between a certain
segment of scintillator 30 and light guide 50. Additional optical
interface 240 is optically coupled between another segment of
scintillator 30 and additional light guide 250.
[0067] FIG. 4B illustrates an optical module 26 that includes a
scintillator 30 and four different optical interfaces--interfaces
40, 140, 240 and 340.
[0068] Optical interface 40 (also referred to as a first optical
interface) is optically coupled between a first segment of
scintillator 30 and light guide 50 (also referred to as first light
guide).
[0069] A second optical interface 140 is optically coupled between
a second segment of scintillator 30 and a second light guide
150.
[0070] A third optical interface 240 is optically coupled between a
third segment of scintillator 30 and a third light guide 250.
[0071] A fourth optical interface 340 is optically coupled between
a fourth segment of scintillator 30 and a fourth light guide
350.
[0072] FIG. 5 illustrates a system 520 and an object 510 according
to an embodiment of the invention.
[0073] The object 510 may be a semiconductor wafer, a flat panel, a
solar panel, a lithographic mask or any other object and the
like.
[0074] The system 520 may be a defect review tool, an electron beam
inspection tool and the like.
[0075] System 520 includes memory module 531, processor 533,
controller 532 and image acquisition module 540.
[0076] The controller 532 is configured to control the operation of
the various modules and/or components of system 520.
[0077] Processor 533 is configured to apply various algorithms on
information obtained by the image acquisition module 540. The
algorithms may be defect review algorithms, defect detection
algorithms, and the like.
[0078] The memory module 531 may be configured to store information
obtained by the image acquisition module 540, the outcome of the
processing that was applied by the processor 533, inspection
recipes, defect review recipes, and the like.
[0079] Image acquisition module 540 may include illumination module
550 as well as collection and detection module 560.
[0080] Illumination module 550 and collection and detection module
570 may be separate modules or may share one or more components.
For example, the illumination module 550 and collection and
detection module 560 may share an objective lens.
[0081] The image acquisition module 540 may include one or more
charged particle columns.
[0082] Illumination module 550 may be configured to illuminate
substrate 510 with one or more electron beams thereby generating
one or more collected electron beams. The one or more collected
electron beams may be reflected and/or scattered from substrate or
interact with the substrate in other manners.
[0083] The one or more collected electron beams may be converted to
light beams by one or more modules such as optical module 21.
[0084] Collection and detection module 560 may include an optical
circuit 70 and optical module 21. Optical module 21 may be replaced
by any of the optical modules illustrated in FIGS. 1B, 2A, 2B, 4A
and 4B. The optical circuit may 70 process, amplify, attenuate,
and/or convert the output light that is outputted from the optical
module 21.
[0085] FIG. 6 illustrates method 600 according to an embodiment of
the invention.
[0086] Method 600 includes stages 610, 620 and 630.
[0087] Stage 610 may include emitting, through a flat surface of a
scintillator that has a scintillator refractive index, emitted
light. The emitting of the emitted light is responsive to an
impingement of a charged particle on the scintillator.
[0088] Stage 610 may be followed by stage 620 of receiving, via an
input surface of an optical interface, the emitted light.
[0089] The optical interface refractive index may substantially
equal the scintillator refractive index.
[0090] According to various embodiment of the invention at least
one of the following is true: [0091] a. The optical interface forms
at least a part of a light guide. [0092] b. The input surface is
coupled to the flat surface by optical contact coupling. [0093] c.
The input surface is attached to the flat surface by an adhesive
material that has an adhesive material refraction index that is
substantially equal to the scintillator refractive index.
[0094] Stage 620 may be followed by stage 630 of directing the
emitted light towards an output surface of the optical
interface.
[0095] Stage 630 may be followed by stage 640 of outputting, via an
output surface of the optical interface, output light. The output
light may propagate through a light guide.
[0096] The output light may exit through a region of the output
surface at an angle, in relation to the region of the output
surface that ranges, for example, between 70 and 110 degrees.
[0097] In the foregoing specification, the invention has been
described with reference to specific examples of embodiments of the
invention. It will, however, be evident that various modifications
and changes may be made therein without departing from the broader
spirit and scope of the invention as set forth in the appended
claims.
[0098] Moreover, the terms "front," "back," "top," "bottom,"
"over," "under" and the like in the description and in the claims,
if any, are used for descriptive purposes and not necessarily for
describing permanent relative positions. It is understood that the
terms so used are interchangeable under appropriate circumstances
such that the embodiments of the invention described herein are,
for example, capable of operation in other orientations than those
illustrated or otherwise described herein.
[0099] The connections as discussed herein may be any type of
connection suitable to transfer signals from or to the respective
nodes, units or devices, for example via intermediate devices.
Accordingly, unless implied or stated otherwise, the connections
may for example be direct connections or indirect connections. The
connections may be illustrated or described in reference to being a
single connection, a plurality of connections, unidirectional
connections, or bidirectional connections. However, different
embodiments may vary the implementation of the connections. For
example, separate unidirectional connections may be used rather
than bidirectional connections and vice versa. Also, plurality of
connections may be replaced with a single connection that transfers
multiple signals serially or in a time multiplexed manner.
Likewise, single connections carrying multiple signals may be
separated out into various different connections carrying subsets
of these signals. Therefore, many options exist for transferring
signals.
[0100] Although specific conductivity types or polarity of
potentials have been described in the examples, it will be
appreciated that conductivity types and polarities of potentials
may be reversed.
[0101] Each signal described herein may be designed as positive or
negative logic. In the case of a negative logic signal, the signal
is active low where the logically true state corresponds to a logic
level zero. In the case of a positive logic signal, the signal is
active high where the logically true state corresponds to a logic
level one. Note that any of the signals described herein may be
designed as either negative or positive logic signals. Therefore,
in alternate embodiments, those signals described as positive logic
signals may be implemented as negative logic signals, and those
signals described as negative logic signals may be implemented as
positive logic signals.
[0102] Furthermore, the terms "assert" or "set" and "negate" (or
"deassert" or "clear") are used herein when referring to the
rendering of a signal, status bit, or similar apparatus into its
logically true or logically false state, respectively. If the
logically true state is a logic level one, the logically false
state is a logic level zero. And if the logically true state is a
logic level zero, the logically false state is a logic level
one.
[0103] Those skilled in the art will recognize that the boundaries
between logic blocks are merely illustrative and that alternative
embodiments may merge logic blocks or circuit elements or impose an
alternate decomposition of functionality upon various logic blocks
or circuit elements. Thus, it is to be understood that the
architectures depicted herein are merely exemplary, and that in
fact many other architectures may be implemented which achieve the
same functionality.
[0104] Any arrangement of components to achieve the same
functionality is effectively "associated" such that the desired
functionality is achieved. Hence, any two components herein
combined to achieve a particular functionality may be seen as
"associated with" each other such that the desired functionality is
achieved, irrespective of architectures or intermedial components.
Likewise, any two components so associated can also be viewed as
being "operably connected," or "operably coupled," to each other to
achieve the desired functionality.
[0105] Furthermore, those skilled in the art will recognize that
boundaries between the above described operations merely
illustrative. The multiple operations may be combined into a single
operation, a single operation may be distributed in additional
operations and operations may be executed at least partially
overlapping in time. Moreover, alternative embodiments may include
multiple instances of a particular operation, and the order of
operations may be altered in various other embodiments.
[0106] Also for example, in one embodiment, the illustrated
examples may be implemented as circuitry located on a single
integrated circuit or within a same device. Alternatively, the
examples may be implemented as any number of separate integrated
circuits or separate devices interconnected with each other in a
suitable manner.
[0107] However, other modifications, variations and alternatives
are also possible. The specifications and drawings are,
accordingly, to be regarded in an illustrative rather than in a
restrictive sense.
[0108] In the claims, any reference signs placed between
parentheses shall not be construed as limiting the claim. The word
`comprising` does not exclude the presence of other elements or
steps then those listed in a claim. Furthermore, the terms "a" or
"an," as used herein, are defined as one or more than one. Also,
the use of introductory phrases such as "at least one" and "one or
more" in the claims should not be construed to imply that the
introduction of another claim element by the indefinite articles
"a" or "an" limits any particular claim containing such introduced
claim element to inventions containing only one such element, even
when the same claim includes the introductory phrases "one or more"
or "at least one" and indefinite articles such as "a" or "an." The
same holds true for the use of definite articles. Unless stated
otherwise, terms such as "first" and "second" are used to
arbitrarily distinguish between the elements such terms describe.
Thus, these terms are not necessarily intended to indicate temporal
or other prioritization of such elements. The mere fact that
certain measures are recited in mutually different claims does not
indicate that a combination of these measures cannot be used to
advantage.
[0109] While certain features of the invention have been
illustrated and described herein, many modifications,
substitutions, changes, and equivalents will now occur to those of
ordinary skill in the art. It is, therefore, to be understood that
the appended claims are intended to cover all such modifications
and changes as fall within the true spirit of the invention.
* * * * *