U.S. patent application number 16/948169 was filed with the patent office on 2022-01-20 for radiation sensor.
This patent application is currently assigned to Tower Semiconductor Ltd.. The applicant listed for this patent is Tower Semiconductor Ltd.. Invention is credited to Pikhay Evgeny, Yakov Roizin.
Application Number | 20220018977 16/948169 |
Document ID | / |
Family ID | 1000005088848 |
Filed Date | 2022-01-20 |
United States Patent
Application |
20220018977 |
Kind Code |
A1 |
Roizin; Yakov ; et
al. |
January 20, 2022 |
RADIATION SENSOR
Abstract
A radiation sensor that may include a first transistor, a first
isolated conductive structure that comprises a floating gate of the
first transistor, a first group of radiation sensing diodes that
are coupled to each other, wherein the first group is configured to
convert sensed radiation that is sensed by the first group to a
first output signal, and to change a state of the first isolated
conductive structure using the first output signal, a second
transistor, a second isolated conductive structure that comprises a
floating gate of the second transistor, and a second group of
radiation sensing diodes that are coupled to each other, wherein
the second group is configured to convert sensed radiation that is
sensed by the second group to a second output signal, and to change
a state, under a control of the first transistor, of the second
isolated conductive structure using the second output signal.
Inventors: |
Roizin; Yakov; (Afula,
IL) ; Evgeny; Pikhay; (Haifa, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tower Semiconductor Ltd. |
Migdal Haemek |
|
IL |
|
|
Assignee: |
Tower Semiconductor Ltd.
Migdal Haemek
IL
|
Family ID: |
1000005088848 |
Appl. No.: |
16/948169 |
Filed: |
September 4, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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16947004 |
Jul 14, 2020 |
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16948169 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01T 1/244 20130101;
G01T 1/243 20130101; G01T 1/247 20130101 |
International
Class: |
G01T 1/24 20060101
G01T001/24 |
Claims
1. A radiation sensor, comprising: a first transistor; a first
isolated conductive structure that comprises a floating gate of the
first transistor; a first group of radiation sensing diodes that
are coupled to each other, wherein the first group is configured to
convert sensed radiation that is sensed by the first group to a
first output signal, and to change a state of the first isolated
conductive structure using the first output signal; a second
transistor; a second isolated conductive structure that comprises a
floating gate of the second transistor; and a second group of
radiation sensing diodes that are coupled to each other, wherein
the second group is configured to convert sensed radiation that is
sensed by the second group to a second output signal, and to change
a state, under a control of the first transistor, of the second
isolated conductive structure using the second output signal.
2. The radiation sensor according to claim 1 wherein the first
transistor is configured to prevent the second isolated conductive
structure to reach a saturation level.
3. The radiation sensor according to claim 1 wherein the first
group of radiation sensing diodes are configured to receive a
larger dose of radiation in relation to the second group of
radiation sensing diodes.
4. The radiation sensor according to claim 1 comprising a blocking
element for preventing the radiation from impinging on the first
transistor.
5. The radiation sensor according to claim 1 wherein the first
isolated conductive structure further comprises a first plate of a
first control capacitor; and wherein the second isolated conductive
structure further comprises a first plate of a second control
capacitor.
6. The radiation sensor according to claim 5 wherein the first
group of radiation sensing diodes and the second group of radiation
sensing diodes are formed in a device layer; wherein the device
layer comprises a second plate of the first control capacitor, and
a second plate of the second control capacitor.
7. The radiation sensor according to claim 1 wherein the first
transistor is serially coupled to the second group of radiation
sensing diodes.
8. The radiation sensor according to claim 1 wherein the first
group of radiation sensing diodes are serially connected radiation
sensing diodes of alternating polarities, some of which are
preceded by radiation shields.
9. The radiation sensor according to claim 8 wherein the first
group of radiation sensing diodes comprises of multiple sequences
of (a) a P+ doped region, (b) an intrinsic region, and (c) an N+
doped region.
10. The radiation sensor according to claim 1 wherein the first
group of radiation sensing diodes and the second group of radiation
sensing diodes are configured to sense ultraviolet radiation.
11. The radiation sensor according to claim 1 wherein the first
group of radiation sensing diodes and the second group of radiation
sensing diodes are configured to sense infrared radiation.
12. The radiation sensor according to claim 1 wherein the first
group of radiation sensing diodes and the second group of radiation
sensing diodes are configured to sense x-ray radiation.
13. The radiation sensor according to claim 1 wherein the first
group of radiation sensing diodes and the second group of radiation
sensing diodes are located at a certain layer of the radiation
sensor; wherein the first isolated conductive structure and the
second isolated conductive structure are located at another layer
of the radiation sensor.
14. The radiation sensor according to claim 1 wherein the first
isolated conductive layer is a single polysilicon layer.
15. The radiation sensor of claim 1 where the first group of
radiation sensing diode are formed in a single polysilicon
layer.
16. The radiation sensor according to claim 1 wherein the radiation
sensor comprises multiple instances of the first transistor, the
first isolated conductive structure, the first group of radiation
sensing diodes, the second transistor, the second isolated
conductive structure, and the second group of radiation sensing
diodes.
17. A method for sensing radiation, the method comprises:
converting, by a first group of radiation sensing diodes that are
coupled to each other, sensed radiation that is sensed by the first
group to a first output signal; changing a state of a first
isolated conductive structure using the first output signal;
wherein the first isolated conductive structure comprises a
floating gate of a first transistor; converting, by a second group
of radiation sensing diodes that are coupled to each other, sensed
radiation that is sensed by the second group to a second output
signal; and changing a state, under a control of the first
transistor, of a second isolated conductive structure using the
second output signal; wherein the second isolated conductive
structure comprises a floating gate of a second transistor.
18. The method according to claim 17 comprising preventing, by the
first transistor, the second isolated conductive structure to reach
a saturation level.
19. The method according to claim 17 comprising receiving by the
first group of radiation sensing diodes a larger dose of radiation
in relation to the second group of radiation sensing diodes.
20. The method according to claim 17 comprising preventing, by a
blocking element, the radiation from impinging on the first
transistor.
21. The method according to claim 17 wherein the first isolated
conductive layer is a single poly silicon layer.
22. A radiation sensor, comprising: a first layer that comprises a
first isolated conductive structure that is a single polysilicon
layer, the first isolated conductive structure comprises a floating
gate of the first transistor; a first insulating layer; a silicon
layer that comprises (a) a first group of radiation sensing diodes
that are coupled to each other, wherein the first group is
configured to convert sensed radiation that is sensed by the first
group to a first output signal, and to change a state of the first
isolated conductive structure using the first output signal;
wherein the first insulating layer is positioned between the first
layer and the silicon layer; an oxide layer; and a silicon
substrate; wherein the oxide layer is positioned between the
silicon layer and the silicon substrate.
Description
[0001] This application is a continuation in part of U.S. patent
application Ser. No. 16/947,004 filing date Jul. 13, 2020 which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] Radiation sensors usually require to be coupled to an
external power source in order to operate.
[0003] The external power source may increase the cost and the size
of the radiation sensor, and may not be available in some
cases.
[0004] There is a growing need to provide a radiation sensor that
may operate without an external power source.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] 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:
[0006] FIG. 1 is an example of a radiation sensor;
[0007] FIG. 2 is an example of a radiation sensor;
[0008] FIG. 3 is an example of a radiation sensor;
[0009] FIG. 4 is an example of a radiation sensor; and
[0010] FIG. 5 is an example of a method.
[0011] 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.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] 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.
[0013] 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.
[0014] 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.
[0015] There may be provided radiation sensors that are powered by
radiation and program one or more floating conductive
structures.
[0016] Such radiation sensors may be used in a variety of
applications--including but not limited to: [0017] a. Allowing a
recipient of a packaged item to learn if the package and especially
the radiation sensor within the package was exposed to
radiation--for example opened, screened by x-ray radiation, and the
like. [0018] b. Monitoring access to a location that--when the
access (for example entering a dark room) exposes a radiation
sensor within the location to radiation. [0019] c. Monitoring
tampering attempts that involve illuminating an item (for example a
memory chip) with radiation.
[0020] There is provided a radiation sensor that may be
manufactured by using fabrication processes that can be easily
integrated into standard process flows (e.g., established CMOS, or
MEMS process flows) without requiring any (or requiring very few)
additional masks. For example, in one embodiment radiation sensing
diodes may be formed on a polycrystalline silicon layer typically
formed on silicon dioxide insulation layers of thick field oxide or
standard shallow trench isolation (STI) in CMOS process flows. Yet
for another example--the radiation sensing diodes may be formed in
silicon device layer on the buried oxide (BOX) layer--using
standard SOI manufacturing processes.
[0021] There may be provided a radiation sensor that may sense
radiation without reaching a saturation level. Reaching the
saturation level may only indicate that the radiation dose exceeded
a predefined level--but does not indicate the exact amount of
radiation.
[0022] Additionally or alternatively--the radiation sensor may
virtually not leak, may store information for a long time, and may
be generated using a cost effective process--that does not require
to manufacture a floating gate made of two layers of
polysilicon.
[0023] A state of an isolated conductive structure or a floating
gate of the isolated conductive structure may refer to the amount
of charge stored in the isolated conductive structure or in the
floating gate. The state may be changed by charging or
discharging--for example using the Fowler-Nordheim programming. Any
reference to a charge operation may be applied mutatis mutandis to
discharge operation.
[0024] FIG. 1 illustrate an example of a radiation sensor 10.
[0025] FIG. 2 is a top view and a schematic view of a radiation
sensor 11. The radiation sensor may belong to radiation sensor 10
or may be a stand-alone radiation sensor.
[0026] FIG. 3 illustrates a partial exploded view and a cross
section view taken along different planes of a radiation
sensor.
[0027] Radiation sensor 10, that includes a first transistor 24, a
first isolated conductive structure 25 that includes a floating
gate 24(1) of the first transistor, a first group 21 of radiation
sensing diodes that are coupled to each other, a second transistor
34, a second isolated conductive structure 35 that comprises a
floating gate 34(1) of the second transistor 34, a second group 31
of radiation sensing diodes that are coupled to each other.
[0028] The second group 31 of radiation sensing diodes may include
any arrangement (one or more sequences) of diodes illustrated in
U.S. patent application Ser. No. 16/947,004 filing date Jul. 13,
2020 which is incorporated herein by reference. The same applies to
the first group 21 of radiation sensing diodes. See--for example
set of group of serially connected photovoltaic diodes of
alternating polarities 21(1)-21(N1), in which odd photovoltaic
diodes are preceded by radiation blocking elements. N1 being a
positive integer. The radiation blocking elements are not shown in
FIG. 2 for convenience of explanation.
[0029] The first group 21 of radiation sensing diodes is configured
to convert sensed radiation that is sensed by the first group 21 to
a first output signal, and to change a state of (by utilizing
Fowler-Nordheim tunneling) the first isolated conductive structure
25 using the first output signal.
[0030] The second group 31 of radiation sensing diodes is
configured to convert sensed radiation that is sensed by the second
group 31 to a second output signal, and to change a state (by
utilizing Fowler-Nordheim tunneling), and under a control of the
first transistor 24, of the second isolated conductive structure
using the second output signal.
[0031] The first transistor 24 controls the changing of state of
the second isolated conductive structure. For example--the first
transistor may be configured to prevent the second isolated
conductive structure 34 to reach a saturation level.
[0032] For example--the first group 21 of radiation sensing diodes
may charge the first isolated conductive structure when sensing
radiation--while the second group 22 of radiation sensing diodes
may discharge the second isolated conductive structure when sensing
radiation.
[0033] The first output signal may be stronger than the second
output signal--for the first output signal may have a magnitude
that has an absolute value that exceeds an absolute value of a
magnitude of the second output signal.
[0034] The stronger first output signal may cause the first
isolated conductive structure 25 to reach a saturation level--when
exposed to large dose of radiation. The value of the large dose may
be predetermined and may be determined based on the characters of
the first isolated conductive structure.
[0035] The first isolated conductive structure 25 may reach a
saturation level before the second output signal causes the second
isolated conductive structure 35 to reach the saturation level.
[0036] The stronger first output signal may deactivate the first
transistor 24 before the second isolated conductive structure 35
reaches the saturation level.
[0037] The first transistor 24 may be a depletion mode transistor
that is open when its gate does not receive any signal--whereas an
increment in the charge of the first isolated conductive structure
25 reduces the conductivity of the first transistor 24--until the
first transistor 24 closes--and prevents the second group 31 of
radiation sensing diodes from charging the second isolated
conductive structure 35.
[0038] Due to the differences between the first output signal and
the second output signal--this occurs before the second isolated
conductive structure 35 reaches the saturation level--so that the
charge of the second isolated conductive structure 35 reflects the
radiation sensed by the second group 31 of radiation sensing
diodes.
[0039] FIG. 1 also illustrates a first tunneling capacitor (TC) 22,
a first control capacitor (CC) 23, a first control gate 25, a
second TC 32, a second CC 33, and a second control gate 35.
[0040] First transistor 24 has a first floating gate 24(1), a first
source 24(2), and a first drain 24(3).
[0041] Second transistor 34 has a second floating gate 34(1), a
second source 34(2), and a second drain 34(3).
[0042] First TC 22 that has a first upper TC plate 22(1) formed in
the first isolated conductive structure 25, a first TC dielectric
layer 22(2), and a first lower TC plate 22(3) formed in another
layer (may be referred to as a device layer).
[0043] Second TC 32 that has a second upper TC plate 32(1) formed
in the second isolated conductive structure 35, a second TC
dielectric layer 32(2), and a second lower TC plate 32(3) formed in
another layer (may be referred to as the device layer).
[0044] Second lower TC plate 34(3) is coupled to the source 24(2)
of the first transistor 24.
[0045] A first end of first group 21 is coupled to first lower TC
plate 22(3).
[0046] A second end of first group 21 is coupled to first lower
plate 23(3) of first CC 23.
[0047] A first end of second group 31 is coupled to first drain
24(3).
[0048] A second end of second group 31 is coupled to second control
gate 35 and to second lower plate 33(2) of second CC 33.
[0049] The second control gate 35 may be used to program the second
isolated conductive structure 35. For example--the second isolated
conductive structure 35 may be charged or discharged using a write
signal from the second control gate. The second isolated conductive
structure 35 may be discharged or charged in response to the
radiation sensed by the second group.
[0050] The second isolated conductive structure 35 may be read (be
sensing the state of the second isolated conductive structure 35)
using the second transistor 34.
[0051] The floating gate of the first transistor and/or of the
second transistor may be made of a single polysilicon layer--which
is simpler and cheaper to implement than a double polysilicon
floating gate--for example the double polysilicon floating gate of
U.S. Pat. No. 8,659,061. Furthermore--the radiation sensing diodes
of the first and second groups may be formed in the same single
polysilicon layer or in the device layer of SOI. They are not
shunted by leakage between P wells and the substrate. In
addition--each group of radiation sensing diodes charge or
discharge a single capacitor--which is much more effective than
charging different capacitors.
[0052] The first transistor 24 may be protected from radiation--for
example by providing an optical blocking element downstream to the
first transistor--for example the blocking element 24' of FIG. 1
could be made from one of metallization metals. This prevents the
first transistor to be opened due to the radiation impinging on the
first transistor--which may cause the first transistor to leak
(remain partially open) even when it should be closed.
[0053] As indicated above--each one of the groups of the radiation
sensing diodes may be arranged in any of the manners illustrated in
U.S. patent application Ser. No. 16/947,004 filing date Jul. 13,
2020 which is incorporated herein by reference which belongs to the
same applicant as the current application.
[0054] For example--the first group of radiation sensing diodes may
be serially connected radiation sensing diodes of alternating
polarities--with radiation blocking elements formed downstream to
only odd (or even) radiation sensing diodes. The first group of
radiation sensing diodes may comprise multiple sequences of (a) a
P+ doped region, (b) an intrinsic region, and (c) an N+ doped
region.
[0055] The first and second groups of radiation sensing diodes may
sense any radiation of any frequency range--for example ultraviolet
radiation (or only a part of the ultraviolet spectrum), infrared
radiation (or only a part of the infrared spectrum), x-ray
radiation (or only a part of the x-ray spectrum), and the like.
[0056] The first group 21 of radiation sensing diodes and the
second group 31 of radiation sensing diodes may be located at a
certain layer (for example a device layer) of the radiation sensor.
The first isolated conductive structure 25, and the second isolated
conductive structure 35 may be located at another layer of the
radiation sensor.
[0057] FIG. 2 illustrates that the first isolated conductive
structure 25 is located to the side of the first group 21. In
practice, the first isolated conductive structure 25 and the first
group 21 are located at different layers of the radiation sensor
11.
[0058] FIG. 2 also illustrates a first control gate 26 connected to
a second end of first group 21 and to the first lower plate 23(3)
of CC 23. This allows to program the first isolated conductive
structure 25.
[0059] FIG. 3 illustrates a radiation sensor 40 that includes (from
top to bottom): [0060] a. One or more top layers 46 (such as
dielectrics, metal, and the like). [0061] b. A first layer 45 that
includes first isolated conductive structure 25 that may be a
single poly silicon layer. [0062] c. First insulating layer 44 (in
which the dielectric layers of first CC 23 and first TC 22 may be
formed. [0063] d. A silicon layer (or a device layer) 43 that may
include first group 21 of radiation sensing diodes. [0064] e. Oxide
layer 42 such as a BOX layer. [0065] f. Silicon substrate 41.
[0066] The first layer 45 may also include second isolated
conductive structure 55.
[0067] The device layer may also include first group 21 of
radiation sensing diodes, parts of first and second transistors,
and the like.
[0068] It should be noted that FIGS. 1-3 illustrates a single
sensing element--and that the radiation sensor 12 may include
multiple sensing elements--as illustrated in FIG. 4. The multiple
sensing elements 13 may be arranged in any manner--ordered,
non-ordered, grid, one dimensional, two dimensional, and the
like.
[0069] Having multiple sensing elements may allow to acquire an
image--thereby using the radiation sensor as an image sensor.
[0070] FIG. 4 is an example of a method 100 for sensing
radiation.
[0071] Method 100 may start by steps 110 and 120
[0072] Step 110 may include converting, by a first group of
radiation sensing diodes that are coupled to each other, sensed
radiation that is sensed by the first group to a first output
signal.
[0073] Step 110 may be followed by step 114.
[0074] Step 114 may include changing a state of a first isolated
conductive structure using the first output signal. The first
isolated conductive structure includes a floating gate of a first
transistor.
[0075] The changing a state of the first isolated conductive
structure may affect a conductivity of a first transistor.
[0076] The first isolated conductive layer may be a single
polysilicon layer.
[0077] Step 120 may include converting, by a second group of
radiation sensing diodes that are coupled to each other, sensed
radiation that is sensed by the second group to a second output
signal.
[0078] Step 120 may be followed by step 124 of changing a state of,
under a control of the first transistor, a second isolated
conductive structure using the second output signal. The second
isolated conductive structure may include a floating gate of a
second transistor.
[0079] Step 124 may include preventing, by the first transistor,
the second isolated conductive structure to reach a saturation
level.
[0080] Steps 110 and 120 may include receiving by the first group
of radiation sensing diodes a larger dose of radiation in relation
to the second group of radiation sensing diodes.
[0081] Method 100 may also include step 130 of preventing, by a
blocking element, the radiation from impinging on the first
transistor.
[0082] Any reference to any of the terms "comprise", "comprises",
"comprising" "including", "may include" and "includes" may be
applied to any of the terms "consists", "consisting", "consisting
essentially of". For example--any of the rectifying circuits
illustrated in any figure may include more components that those
illustrated in the figure, only the components illustrated in the
figure or substantially only the components illustrated in the
figure.
[0083] 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.
[0084] 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.
[0085] 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 can be implemented which achieve the
same functionality.
[0086] 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 can 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.
[0087] 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.
[0088] 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.
[0089] 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.
[0090] 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.
[0091] 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.
* * * * *