U.S. patent application number 16/805952 was filed with the patent office on 2020-07-23 for ceramic-aluminum assembly with bonding trenches.
This patent application is currently assigned to Watlow Electric Manufacturing Company. The applicant listed for this patent is Watlow Electric Manufacturing Company. Invention is credited to Todd Brooke, Kurt English, Patrick Margavio, Miranda Pizzella, Jacob Wilson.
Application Number | 20200230728 16/805952 |
Document ID | / |
Family ID | 66248706 |
Filed Date | 2020-07-23 |
United States Patent
Application |
20200230728 |
Kind Code |
A1 |
Margavio; Patrick ; et
al. |
July 23, 2020 |
CERAMIC-ALUMINUM ASSEMBLY WITH BONDING TRENCHES
Abstract
A method of joining is provided. the method includes preparing a
first member, preparing a second member, and forming at least one
trench in at least one of the first member and the second member.
The method further includes placing a strip of solid aluminum
material between the first member and the second member across the
trench, bringing the first member and the second member together to
contact the solid aluminum material and to form an assembly, and
applying a force and heat to the assembly above a melting point of
the solid aluminum material such that the solid aluminum material
flows into the trench. Additionally, the method further includes
applying additional heat to the assembly at or above a wetting
temperature of the member in which the trench is formed to bond the
first member to the second member along adjacent faces and cooling
the assembly.
Inventors: |
Margavio; Patrick;
(Columbia, MO) ; English; Kurt; (Columbia, MO)
; Wilson; Jacob; (St. Charles, MO) ; Pizzella;
Miranda; (St. Louis, MO) ; Brooke; Todd; (St.
Louis, MO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Watlow Electric Manufacturing Company |
St. Louis |
MO |
US |
|
|
Assignee: |
Watlow Electric Manufacturing
Company
St. Louis
MO
|
Family ID: |
66248706 |
Appl. No.: |
16/805952 |
Filed: |
March 2, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15955431 |
Apr 17, 2018 |
|
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|
16805952 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B 2235/963 20130101;
C04B 2237/365 20130101; C04B 2237/121 20130101; C04B 35/645
20130101; C04B 37/006 20130101; C04B 2237/64 20130101; C04B
2237/343 20130101; C04B 2237/366 20130101; C04B 2237/592 20130101;
B23K 1/19 20130101; C04B 2235/945 20130101; H01L 21/6831 20130101;
C04B 2237/50 20130101; C04B 2237/348 20130101 |
International
Class: |
B23K 1/19 20060101
B23K001/19; C04B 35/645 20060101 C04B035/645; H01L 21/683 20060101
H01L021/683 |
Claims
1. A method of joining comprising: preparing a first member;
preparing a second member; forming at least one trench in at least
one of the first member and the second member; placing a strip of
solid aluminum material between the first member and the second
member across the trench; bringing the first member and the second
member together to contact the solid aluminum material and to form
an assembly; applying a force and heat to the assembly above a
melting point of the solid aluminum material such that the solid
aluminum material flows into the trench; applying additional heat
to the assembly at or above a wetting temperature of the member in
which the trench is formed to bond the first member to the second
member along adjacent faces; and cooling the assembly, wherein a
spacing between the first member and the second member along the
adjacent faces is less than 5 .mu.m.
2. The method according to claim 1, wherein preparing the first and
second member comprises creating a surface roughness of the
adjacent faces of the first and second members between 5 .mu.m and
100 nanometers.
3. The method according to claim 1, wherein the first member and
the second member are selected from the group consisting of
aluminum nitride (AlN), alumina, zirconia, and silicon carbide
(SiC).
4. The method according to claim 1, wherein each of the first
member and the second member are each aluminum nitride (AlN).
5. The method according to claim 4, wherein the wetting temperature
is above 850.degree. C.
6. The method according to claim 1, wherein a purity of the strip
of solid aluminum material is greater than or equal to about 97%
and the assembly is heated to a temperature above about 800.degree.
C., and the force applied to the assembly is between about 0.1 MPa
to 6.5 MPa.
7. The method according to claim 1, wherein the applying additional
heat to the assembly comprises heating the assembly to 1100.degree.
C. under a vacuum condition of approximately 10.sup.-3 Torr.
8. The method according to claim 1, wherein applying additional
heat to the assembly comprises heating the assembly to 800.degree.
C. under a vacuum condition of approximately 10.sup.-6 Torr.
9. The method according to claim 1, wherein the solid aluminum
material is aluminum foil.
10. The method according to claim 1, wherein the solid aluminum
material is applied by a physical vapor deposition (PVD)
process.
11. The method according to claim 1, wherein at least one trench is
formed with a depth and a width, and the width of the trench is
between 5 and 20 times the depth of the trench.
12. The method according to claim 1, wherein each of the first
member and the second member are each a flat plate.
13. The method according to claim 1, wherein the first member is a
flat plate and the second member is a hollow shaft.
14. The method according to claim 1 further comprising forming a
plurality of trenches that are spaced a distance apart less than 2
mm.
15. A method of joining comprising: preparing a first member;
preparing a second member; forming a plurality of trenches spaced a
distance apart less than 2 mm in at least one of the first member
and the second member, placing a strip of solid aluminum material
between the first member and the second member across the trench;
bringing the first member and the second member together to contact
the solid aluminum material and to form an assembly; applying a
force and heat to the assembly above a melting point of the solid
aluminum material such that the solid aluminum material flows into
the trench; applying additional heat to the assembly at or above a
wetting temperature of the member in which the trench is formed to
bond the first member to the second member along adjacent faces;
and cooling the assembly, wherein a spacing between the first
member and the second member along the adjacent faces is less than
5 .mu.m.
16. The method according to claim 15, wherein preparing the first
and second member comprises creating a surface roughness of the
adjacent faces of the first and second members between 5 .mu.m and
100 nanometers.
17. The method according to claim 15, wherein the first member and
the second member are selected from the group consisting of
aluminum nitride (AlN), alumina, zirconia, and silicon carbide
(SiC).
18. The method according to claim 15, wherein each of the first
member and the second member are each aluminum nitride (AlN).
19. The method according to claim 15, wherein the solid aluminum
material is aluminum foil.
20. The method according to claim 15, wherein the solid aluminum
material is applied by a physical vapor deposition (PVD) process.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 15/955,431, filed on Apr. 17, 2018. The disclosure of the above
application is incorporated herein by reference.
FIELD
[0002] The present disclosure relates generally to methods of
joining objects, and more particularly to methods of joining
ceramic materials and the resulting joined assemblies.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0004] Support pedestals are often used in semiconductor
processing. A support pedestal typically includes a plate member
for supporting a wafer thereon and a tubular shaft disposed under
the plate member. The plate member may include a ceramic substrate
and a plurality of functional elements, such as a heating element,
embedded in the ceramic substrate.
[0005] The ceramic substrate may be formed by hot pressing. Hot
pressing is a high-pressure, low-strain process to enhance
densification of powder or compacted preform at high temperature.
Typically, the powder or the compacted preform is put into a mold,
and high temperatures and pressure are applied for densification
and sintering.
[0006] The functional elements that are embedded in the ceramic
substrate must withstand high heat and high pressure in the hot
pressing process. Therefore, the materials for forming the
functional elements are limited. Moreover, hot pressing requires
high temperature and high pressure equipment, thereby increasing
manufacturing costs.
[0007] In some cases, two or more ceramic substrates may be bonded
together by brazing. However, the brazed joint is not without
problems due to poor wettability of the ceramic materials as well
as the incompatible coefficient of thermal expansion (CTE) between
the brazing metals and the ceramic materials. Cracks or
delamination may occur between the brazing metals and the ceramic
substrates at elevated temperatures due to their significantly
different thermal expansions.
[0008] These challenges, among other challenges, in manufacturing
ceramic support pedestals are addressed by the present
disclosure.
SUMMARY
[0009] In one form of the present disclosure, a method of joining
is provided. The method comprises preparing a first member,
preparing a second member, and forming at least one trench in at
least one of the first member and the second member. The method
further comprises placing a strip of solid aluminum material
between the first member and the second member across the trench,
bringing the first member and the second member together to contact
the solid aluminum material and to form an assembly, and applying a
force and heat to the assembly above a melting point of the solid
aluminum material such that the solid aluminum material flows into
the trench. Additionally, the method further includes applying
additional heat to the assembly at or above a wetting temperature
of the member in which the trench is formed to bond the first
member to the second member along adjacent faces and cooling the
assembly, wherein a spacing between the first member and the second
member along the adjacent faces is less than 5 .mu.m.
[0010] In another form of this method, preparing the first and
second member comprises creating a surface roughness of the
adjacent faces of the first and second members between 5 .mu.m and
100 nanometers.
[0011] In yet another form of this method, the first member and the
second member are selected from the group consisting of aluminum
nitride (AlN), alumina, zirconia, and silicon carbide (SiC).
[0012] In at least one form of this method, each of the first
member and the second member are each aluminum nitride (AlN). In
variations of this method, the wetting temperature is above
850.degree. C.
[0013] In other forms of this method, a purity of the strip of
solid aluminum material is greater than or equal to about 97% and
the assembly is heated to a temperature above about 800.degree. C.,
and the force applied to the assembly is between about 0.1 MPa to
6.5 MPa.
[0014] In another form of this method, applying additional heat to
the assembly comprises heating the assembly to 1100.degree. C.
under a vacuum condition of approximately 10.sup.-3 Torr.
[0015] In numerous forms of this method, applying additional heat
to the assembly comprises heating the assembly to 800.degree. C.
under a vacuum condition of approximately 10.sup.-6 Torr.
[0016] In at least one form of this method, the solid aluminum
material is aluminum foil.
[0017] In some forms of this method, the solid aluminum material is
applied by a physical vapor deposition (PVD) process.
[0018] In still another form of this method, at least one trench is
formed with a depth and a width, and the width of the trench is
between 5 and 20 times the depth of the trench.
[0019] In numerous forms of this method, each of the first member
and the second member are each a flat plate.
[0020] In a form of this method, the first member is a flat plate
and the second member is a hollow shaft.
[0021] Other forms of this method further comprise forming a
plurality of trenches that are spaced a distance apart less than 2
mm.
[0022] In another form of the present disclosure, a method of
joining is provided. The method comprises preparing a first member,
preparing a second member, and forming a plurality of trenches
spaced a distance apart less than 2 mm in at least one of the first
member and the second member. The method further comprises placing
a strip of solid aluminum material between the first member and the
second member across the trench, bringing the first member and the
second member together to contact the solid aluminum material and
to form an assembly, and applying a force and heat to the assembly
above a melting point of the solid aluminum material such that the
solid aluminum material flows into the trench. Additionally, the
method further comprises applying additional heat to the assembly
at or above a wetting temperature of the member in which the trench
is formed to bond the first member to the second member along
adjacent faces and cooling the assembly, wherein a spacing between
the first member and the second member along the adjacent faces is
less than 5 .mu.m.
[0023] In at least one form of this method, preparing the first and
second member comprises creating a surface roughness of the
adjacent faces of the first and second members between 5 .mu.m and
100 nanometers.
[0024] Additionally, in other forms of this method, the first
member and the second member are selected from the group consisting
of aluminum nitride (AlN), alumina, zirconia, and silicon carbide
(SiC).
[0025] In some forms of this method, each of the first member and
the second member are each aluminum nitride (AlN).
[0026] In yet another form of this method, the solid aluminum
material is aluminum foil.
[0027] Alternatively, in another form of this method, the solid
aluminum material is applied by a physical vapor deposition (PVD)
process.
[0028] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The present disclosure will become more fully understood
from the detailed description and the accompanying drawings,
wherein:
[0030] FIG. 1 is a cross-sectional view of a joined assembly
constructed in accordance with the teachings of the present
disclosure;
[0031] FIG. 2 is a side view of a second member of the joined
assembly of FIG. 1;
[0032] FIG. 3 is an enlarged view of portion A of FIG. 2;
[0033] FIG. 4 is a flow diagram of a method of bonding materials in
accordance with the teachings of the present disclosure;
[0034] FIGS. 5A to 5E depict the steps of bonding materials using
the method of FIG. 4, wherein:
[0035] FIG. 5A depicts a step of placing a solid aluminum material
between a first member and a second member;
[0036] FIG. 5B depicts a step of melting solid aluminum material
and causing the molten aluminum material to flow into trenches of
the second member;
[0037] FIG. 5C depicts a step of pressing the first member and the
second member against each other to reduce the spacing
therebetween;
[0038] FIG. 5D depicts a step of heating the assembly to a
temperature above a wetting temperature so that the molten aluminum
material conforms to the geometry of the trenches;
[0039] FIG. 5E is an enlarged view of portion B of FIG. 5D;
[0040] FIG. 6 is a schematic view of a variant of a joined assembly
constructed in accordance with the teachings of the present
disclosure; and
[0041] FIG. 7 is a schematic view of another variant of a joined
assembly constructed in accordance with the teachings of the
present disclosure.
[0042] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0043] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses.
[0044] Referring to FIG. 1, a joined assembly 10 constructed in
accordance with the teachings of the present disclosure includes a
first member 12 and a second member 14 bonded by aluminum material
16 along a periphery of the first and second members 12 and 14. The
first member 12 and the second member 14 may be made of ceramic
materials, such as aluminum nitride (AlN), alumina, zirconia, and
silicon carbide (SiC). When the joined assembly 10 is used to form
a support pedestal in semiconductor processing, both the first
member 12 and the second member 14 may be made of aluminum nitride
(AlN) and functional layers (not shown) may be disposed at the
interface between the first and second members 12, 14.
[0045] The first and second members 12, 14 in this form each have a
plate configuration and define adjacent faces 18 facing each other.
In one form, the adjacent faces 18 have a surface flatness of less
than 5 .mu.m, and a surface roughness of less than 3 .mu.m. In one
application, the surface roughness of the adjacent faces 18 may be
in the range between 100 nm and 5 .mu.m. A spacing between the
first member 12 and the second member 14 along the adjacent faces
is less than 5 .mu.m in one form of the present disclosure.
[0046] Referring to FIGS. 2 and 3, at least one of the first and
second members 12 and 14 define a bonding feature 20 along its
periphery and on the adjacent face 18. The bonding feature 20 may
be in the form of one or more trenches 22 as shown. The aluminum
material 16 is filled in the trenches 22 as described in greater
detail below. One of the trenches 22 that is closer to a center of
the second member 14 may be deeper than the other trenches 22.
While a total of four trenches 22 are shown in the second member 14
in the illustrated form, the bonding feature 20 can have any number
of trenches and can be formed in the first member 12 and/or the
second member 14 without departing from the scope of the present
disclosure. Further, the trenches 22 may take any path along each
of the first and/or second members 12/14 depending on application
requirements, which may be circular, sinuous, or linear, among
other paths.
[0047] In FIG. 3, the solid aluminum material 16 is depicted to
show the position of the solid aluminum material 16 relative to the
trenches 22 when the solid aluminum material 16 is placed between
the first member 12 and the second member 14. In this form, the
solid aluminum material 16 is placed to overlap the two outermost
trenches 22. In this form, the deepest trench that is closer to the
center of the second member 12 functions to restrict the molten
aluminum material from flowing toward the center and outside the
bonding area.
[0048] When a plurality of trenches 22 are formed, the plurality of
trenches 22 may be configured parallel to each other and are spaced
at a distance apart less than 2 mm. Making the trenches 22 closer
to each other can reduce the size of the bonding area to less than
2 mm. A smaller bonding area has the advantages of reducing the
area that needs to be heated to the wetting temperature and
achieving uniform heating in the bonding area during the bonding
process, which will be described in more detail below. Moreover,
the smaller bonding area reduces the risk of aluminum flowing into
adjacent area where functional elements such as vias, routing
circuits, terminations, among others, are disposed. The trenches 22
are also configured limit the flow of aluminum, or other bonding
material that may be used besides aluminum, in the bonding
area.
[0049] In one form, the number of the trenches 22 is at least three
or at least five. The aspect ratio (i.e., the width/depth) of each
of the trenches 22 is between 5 to 20. In other words, the width of
each trench is between 5 and 20 times the depth of each trench 22.
A shallower trench 22 contributes to a desired hermeticity of less
than 10.sup.-9 mbar-l/sec. The width of the bonding area may be
less than 3 mm. The depth of the trenches 22 is less than 50 .mu.m,
and in one form less than 20 .mu.m to reduce thermal stress due to
differences in thermal expansion between the bonding material
(i.e., aluminum) and the ceramic member (i.e., AlN). When a deeper
trench (e.g., larger than 100 .mu.m) is used, the trench 22 should
be made wider in order to achieve the required hermeticity.
[0050] When the first and second members 12, 14 are circular
members, the plurality of trenches 22 are configured to have an
annular shape along the periphery of the first and second members
12, 14. However, the shape (or path) of the trenches 22 may vary
according to application requirements and may further be of a
varying width (rather than a constant width as illustrated herein)
while remaining within the scope of the present disclosure.
[0051] Referring now to FIG. 4, a method 50 of joining materials,
particularly ceramic materials, to make the joined assembly 10 of
FIG. 1 starts with preparing a first member 12 and a second member
14 with a predetermined surface roughness in adjacent faces 18 in
step 52. The first member 12 and the second member 14 may be made
of aluminum nitride (AlN), alumina, zirconia, and silicon carbide
(SiC). The adjacent faces 18 of the first and second members each
have a surface roughness between 100 nm and 5 .mu.m.
[0052] Next, at least one trench 22 is formed in the adjacent face
18 of at least one of the first and second members 12, 14 in step
54. Referring to FIG. 5A, the first member 12 and the second member
14 are disposed adjacent each other with a solid aluminum material
disposed therebetween in step 56. The solid aluminum material may
be an aluminum foil and disposed adjacent to the at least one
trench 22. This step is performed at room temperature.
Alternatively, the aluminum material may be sputtered into the at
least one trench 22, such as by physical vapor deposition
(PVD).
[0053] Thereafter, force and heat is applied to the assembly of the
first and second members 12, 14 and the solid aluminum material
above a melting point of the solid aluminum material in step 58.
The melting point of the solid aluminum material is approximately
660.degree. C. The force is applied on the first and second members
12, 14 to press the first and second members against each other. In
this step, the solid aluminum material is melted and the molten
aluminum material flows into the trenches 22 as shown in FIG. 5B.
As force continues to be applied on the first and second members 12
and 14, the spacing between the first and second members 12 and 14
is reduced until most of the molten aluminum material is disposed
in the trenches 22. However, as shown in FIG. 5C, the molten
aluminum material balls up and does not conform to the geometry of
the trench wall due to poor wettability of the ceramic material of
the first or second members 12, 14. In one form, a spacing between
the first member 12 and the second member 14 along the adjacent
faces 18 is less than 5 .mu.m.
[0054] The heat can be applied locally to the bonding area of the
first and second members 12, 14 to reduce the risks of damaging the
functional elements disposed at other areas of the first and second
members 12, 14.
[0055] Next, additional heat is applied to the assembly at or above
a wetting temperature of the first member 12 or second member 14
where the trench 22 is formed to bond the first member 12 to the
second member 14 along adjacent faces 18 in step 60. For aluminum
nitride, the wetting temperature is above 850.degree. C. In this
step, alumina native oxide is broken in order to achieve
wettability of the ceramic material. Wettability of the ceramics
can be achieved when a purity of aluminum is greater than or equal
to about 97%, the temperature is above about 800.degree. C., the
pressure is about 0.1 MPa to 6.5 MPa and a vacuum condition is
approximately 10.sup.-3 Torr and below a vacuum level. Vacuum level
and temperature are balanced to achieve wettability according to
the teachings of the present disclosure. Wettability can be
achieved at 10.sup.-3 Torr and at temperature of 1100.degree. C.,
or at 10.sup.-6 Torr and at a temperature of 800.degree. C. When
the thermal process is performed between 1 to 10 hours, the
aluminum begins to diffuse into the aluminum nitride to conform to
the geometry of the aluminum nitride. Therefore, the molten
aluminum material is shaped to conform to the geometry of the
trenches 22 as shown in FIG. 5D, even on a micro-scale, due to
wetting between the molten aluminum material and the trench wall of
the first member 12 or the second member 14.
[0056] Similarly, the additional heat can be applied locally to the
bonding area, rather than the entire assembly, to reduce the risks
of damaging the functional elements disposed at other areas of the
first and second members 12, 14.
[0057] As shown in FIG. 5E, molten aluminum material has good
wettability so that aluminum can be used to bond two ceramic
materials, particularly aluminum nitride (AlN) together to create a
hermetic bonding therebetween.
[0058] After the first member 12 is bonded to the second member 14,
the assembly is cooled in step 62.
[0059] Referring to FIG. 6, a variant of a bonded assembly 70
constructed in accordance with the teachings of the present
disclosure may include a first member 72 and a second member 74
bonded by an aluminum material 76 via direct surface to surface
bonding without forming any trench in the first member 72 or the
second member 74. The first and second members 72, 74 are
temporarily spaced apart by shims 78 in this form prior to bonding,
and the aluminum material 76 has a width greater than 2 mm to
achieve hermeticity.
[0060] Referring to FIG. 7, another variant of a joined member 90
constructed in accordance with the teachings of the present
disclosure may include a first member 92, a second member 94, and
an aluminum material 96 filled in a single trench of one of the
first and second member 92, 94. When one single trench is used,
which is arcuate in this form, the trench should have a width
larger than 6 mm and the depth larger than 20 .mu.m in order to
achieve hermeticity.
[0061] It should be understood that the trenches may take on any
shape other than those illustrated herein, including by way of
example, tapered (inwardly or outwardly), dovetail, or polygonal,
among other shapes. Also, the "width" of the trench as used and
claimed herein refers to the maximum dimension across the trench
for any given geometrical shape of the trench, such as the arcuate
shape in FIG. 7. Further, the trenches may further include corner
radii at an intersection with a surface of the member in which the
trench is formed while remaining within the scope of the present
disclosure.
[0062] With the bonding method of the present disclosure, ceramic
materials can be relatively easily bonded. This method can be used
to manufacture a ceramic pedestal in semiconductor processing,
however, other applications are contemplated according to the
teachings of the present disclosure. Therefore, the various
functional layers may be formed on a plurality of ceramic members
and then joined together by aluminum materials to form the heating
plate. Accordingly, high temperature and high pressure equipment
for a hot pressing operation may not be needed to form a monolith
substrate, thereby reducing the manufacturing costs.
[0063] Moreover, the bonding methods according to the present
disclosure involve relatively lower temperatures and relatively
lower pressures. As a result, a wider selection of materials is
available for forming the various functional layers in the ceramic
substrate. For example, a layered heater formed by a thick film,
thin film, thermal spray, or sol-gel process may be applied on one
of the first and second members before the first and second members
are bonded together using the bonding method of the present
disclosure. TiNiHf termination braze, Nickel termination plating,
or Aremco.RTM. anchor paste may be applied on the first member
and/or the second member before the first and second members are
bonded using the method of the present disclosure.
[0064] The bonding methods can also be used to bond a heating plate
to a tubular shaft of the support pedestal to provide thermocouple
pocket isolation. The bonding method can be used to manufacture a
thin (thickness between 10 and 50 mm) flat (surface roughness less
than 10 .mu.m) AlN heater assembly in a variety of applications
including AlN electrostatic chuck assembly.
[0065] Further, a support pedestal manufactured by the bonding
methods of the present disclosure allows for repair and replacement
of the heating plate, thereby increasing the life of the support
pedestal.
[0066] It should be noted that the disclosure is not limited to the
form described and illustrated as examples. A large variety of
modifications have been described and more are part of the
knowledge of the person skilled in the art. These and further
modifications as well as any replacement by technical equivalents
may be added to the description and figures, without leaving the
scope of the protection of the disclosure and of the present
patent.
* * * * *