U.S. patent application number 15/581716 was filed with the patent office on 2017-08-17 for coaxial hollow cathode plasma assisted directed vapor deposition and related method thereof.
This patent application is currently assigned to University of Virginia Patent Foundation. The applicant listed for this patent is University of Virginia Patent Foundation. Invention is credited to Goesta Mattausch, Henry Morgner, Frank-Holm Roegner, Haydn N. G. Wadley.
Application Number | 20170236692 15/581716 |
Document ID | / |
Family ID | 42665880 |
Filed Date | 2017-08-17 |
United States Patent
Application |
20170236692 |
Kind Code |
A1 |
Wadley; Haydn N. G. ; et
al. |
August 17, 2017 |
Coaxial Hollow Cathode Plasma Assisted Directed Vapor Deposition
and Related Method Thereof
Abstract
A plasma generation process that is more optimized for vapor
deposition processes in general, and particularly for directed
vapor deposition processing. The features of such an approach
enables a robust and reliable coaxial plasma capability in which
the plasma jet is coaxial with the vapor plume, rather than the
orthogonal configuration creating the previous disadvantages. In
this way, the previous deformation of the vapor gas jet by the work
gas stream of the hollow cathode pipe can be avoided and the
carrier gas consumption needed for shaping the vapor plume can be
significantly decreased.
Inventors: |
Wadley; Haydn N. G.;
(Keswick, VA) ; Mattausch; Goesta; (Ullersdorf,
DE) ; Morgner; Henry; (Dresden, DE) ; Roegner;
Frank-Holm; (Dresden, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
University of Virginia Patent Foundation |
Charlottesville |
VA |
US |
|
|
Assignee: |
University of Virginia Patent
Foundation
Charlottesville
VA
|
Family ID: |
42665880 |
Appl. No.: |
15/581716 |
Filed: |
April 28, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13202828 |
Sep 12, 2011 |
9640369 |
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PCT/US2010/025259 |
Feb 24, 2010 |
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15581716 |
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61248082 |
Oct 2, 2009 |
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61154890 |
Feb 24, 2009 |
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Current U.S.
Class: |
427/458 |
Current CPC
Class: |
H01J 37/3244 20130101;
H01J 37/32339 20130101; H01J 37/32357 20130101; C23C 14/246
20130101; H01J 37/34 20130101; H01J 37/32055 20130101; H01J
37/32596 20130101; C23C 14/228 20130101; C23C 14/30 20130101; H01J
37/3233 20130101; H01J 2237/332 20130101; H01J 37/32568 20130101;
C23C 14/32 20130101; H01J 37/3053 20130101; H01J 37/32449
20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32; C23C 14/30 20060101 C23C014/30; C23C 14/22 20060101
C23C014/22 |
Claims
1-37. (canceled)
38. A method for depositing at least one evaporant onto at least
one substrate, said method comprising: providing at least one
substrate, providing at least one evaporant source, impinging said
at least one evaporant source with an energetic beam to generate a
vapor plume, generating a plasma and discharging a current that is
aligned with said vapor plume, emitting at least one plasma forming
gas in a direction that is at least substantially aligned with said
vapor plume, electrostatically attracting said discharge current
towards at least one anode, and interacting said plasma with said
substrate.
39. The method of claim 38, wherein said discharge current is
emitted by at least one hollow cathode operating in a high-current,
low-voltage arc mode, forming a low-voltage electron beam.
40. The method of claim 38, wherein said at least one evaporant
source is a solid.
41. The method of claim 38, wherein said discharge current is
changed to modulate or control the plasma density.
42. The method of claim 39, wherein said at least one hollow
cathode emits said plasma-forming gas such as to generate a plasma
jet streaming off of the hollow cathode's orifice.
43. The method of claim 42, wherein the axis and/or momentum of
said plasma jet and of said low-voltage electron beam is at least
substantially aligned with that of the said hollow cathode.
44. The method of claim 42, wherein said plasma jet at least
partially entrains said vapor plume and at least partially assists
in transporting said vapor plume to said substrate.
45. The method of claim 42, wherein said plasma jet at least
partially shapes said vapor plume.
46. The method of claim 44, wherein at least some of the vapor
plume is ionized by said plasma jet and by said low-voltage
electron beam.
47. The method of claim 38, further comprising providing a heat
source for initiating said plasma emission.
48. The method of claim 47, wherein said heat source comprises a
heat source based on Ohmic heating of a current conductor, a heat
source based on an auxiliary gas discharge, or a kicker circuit to
ignite the hollow cathode emission via a high-voltage impulse.
49. The method of claim 38, further comprising providing at least
one cooling device for cooling said at least one evaporant
source.
50. The method of claim 49, wherein said cooling source comprises a
crucible.
51. The method of claim 44, wherein said at least one of said
hollow cathodes are realized in an annular configuration comprising
two coaxial cylinders of slightly different diameters thus forming
an annular slot which facilitates the hollow cathode effect.
52. The method of claim 44, wherein said two or more hollow
cathodes are positioned in an annular configuration around said at
least one evaporant source with the evaporant source at least
substantially coaxially integrated inside said annular
configuration.
53. The method of claim 52, wherein relative intensity of the
plasma jets generated by said at least one hollow cathodes may be
controlled for directional sweeping either of said plasma or vapor
plume, or both, from side to side.
54. The method of claim 53, wherein said directional sweeping is
accomplished by controlling the pressure or gas flow rate
individually in each hollow cathode.
55. The method of claim 53, wherein said directional sweeping is
accomplished by controlling the direction of emission.
56. The method of claim 38, wherein said energetic beam is produced
by an electron beam gun, or laser.
57. The method of claim 56, wherein said energetic beam source
further comprises means to alter the beam impingement points among
said one or more evaporant sources.
58. The method of claim 38, further comprising providing a bias
voltage applied to said substrate for accelerating ions toward said
substrate.
59. The method of claim 58, wherein said bias voltage is a DC, AC,
or pulsed voltage.
60. The method of claim 42, further comprising means for the inlet
of at least one secondary gas forming at least one jet positioned
at least substantially coaxially with said at lets one evaporant
source and said at least one hollow cathode.
61. The method of claim 60, wherein said at least one secondary gas
at least partially assist in shaping and transporting said vapor
plume to said substrate.
62. The method of claim 60, wherein said secondary gas jets
introduce reactant gases for creating compounds with the vapor
plume.
63. The method of claim 38, wherein said hollow cathode discharges
current to an annular anode.
64. The method of claim 63, wherein said anode is configured in an
elevated position above said hollow cathode source.
65. The method of claim 38, further comprising positioning said
anode above said substrate.
66. The method of claim 38, further comprising positioning said
anode between said substrate and said hollow cathode.
67. The method of claim 38, wherein said anode further comprises
means for creating a magnetic field and for guiding a magnetic flux
such that the magnetic field lines in front of the annular anode
are substantially parallel to its surface and radially directed
thus forming a closed electrons drift track in circumferential
direction which is substantially parallel to the anode's
surface.
68. The method of claim 67, wherein said magnetic field arrangement
facilitates an axial potential gradient for accelerating positive
ions toward said substrate.
69. The method of claim 38, further comprising positioning said
anode at least substantially coaxially and in the same plane as the
at least one hollow cathode.
70. The method of claim 69, further comprising bisecting said anode
radially to form anode segments.
71. The method of claim 70, further comprising bisecting said anode
into the same number of segments as the number of hollow cathodes
and the hollow cathode emissions burn diametrically across the
vapor plume between each one of the at least one hollow cathodes
and corresponding anode segment situated at the opposite
position.
72. The method of claim 38, further comprising positioning a
solenoid at least partially proximal to said hollow cathode.
73. The method of claim 72, wherein said solenoid is capable of at
least partially bending said energetic beam.
74. The method of claim 72, wherein said solenoid is positioned an
energized such as to magnetically enhance the at least one hollow
cathode's efficiency.
75. The method of claim 72, wherein said solenoid at least
partially increases plasma density and facilitates an axial
potential gradient for accelerating positive ions toward said
substrate.
76-77. (canceled)
78. The method of claim 38, wherein said alignment of said
discharging current with said vapor plume is at least substantially
coaxial.
79. The method of claim 38, wherein said substantial alignment of
the emission direction of said plasma forming gas with said vapor
plume is at least substantially coaxial.
80. The method of claim 44, wherein said at least one hollow
cathodes comprises at least one of the following: pipe, conduit,
tube, channel, hose, stem, duct, port, groove, passage, tunnel, and
port.
81. The method of claim 52, wherein said annular configuration
provides an array.
82. The method of claim 57, wherein said altering means comprises
at least one deflection coil.
Description
RELATED APPLICATIONS
[0001] The present application claims priority from U.S.
Provisional Application Ser. No. 61/154,890, filed Feb. 24, 2009,
entitled "Coaxial Hollow Cathode Plasma Assisted Directed Vapor
Deposition and Related Method Thereof and U.S. Provisional
Application Ser. No. 61/248,082, filed Oct. 2, 2009, entitled
"Coaxial Hollow Cathode Plasma Assisted Directed Vapor Deposition
and Related Method Thereof;" the disclosures of which are hereby
incorporated by reference herein in their entirety.
BACKGROUND OF THE INVENTION
[0002] Coatings applied by physical vapor deposition (PVD)
processes--typically performed in a vacuum--are widely used in
various applications such as in creating barrier layers for
packaging films, metalizing plastics for flexible electronics and
EMI shielding purposes, depositing scratch-proof, corrosion
protection or decorative layers on various raw materials, or for
controlling the electrical, optical and tribological properties of
components, tools and machine parts. Usually, different techniques
may be capable of depositing the desired layers, but business
economics favor processes which create the coatings quickly and
efficiently. This means, the process must be able to generate large
amounts of vapor rapidly, and to transport and deposit it to the
substrate with low losses and at the right atomic scale structures
needed for the given application.
[0003] Electron beams are established as a known tool for
evaporating materials at highly achievable rates. For coating of
large-area substrates, like plastic or metal films and sheets,
extended evaporators heated by scanned high-power electron beams
are available. It is well known that deposition rates ranging up to
10 .mu..mu.m/s can be achieved with this technology, i.e. the rates
are several orders of magnitude higher than with sputter
technology. Without applying additional aids, however, the layers
grown at high rates are usually of poor quality.
[0004] Another drawback of conventional thermal evaporators--the
fairly low utilization of the evaporant material when coating
smaller substrates such as tools, engine parts or fibers--stems
from the inherently divergent propagation characteristic of the
vapor particles.
[0005] To address these issues, the development of a new coating
technology, which is now called "Directed Vapor Deposition" (DVD)
was started several years ago. The basic idea of the DVD concept is
to evaporate the coating material by an electron beam and then to
capture, transport and focus the vapor particles by a flowing
carrier gas stream. This approach, fully described and disclosed in
the U.S. Pat. No. 5,534,314 (of which is hereby incorporated by
reference), combines the advantages of conventional EB evaporation
(high vaporization rate, clean and uncontaminated material
evaporation, easy alloy deposition by co-evaporation of the pure
constituents from individual crucibles) with the advantages of
known jet evaporators (high material utilization efficiency,
possibility to vary adatom energy and spatial distribution of the
vapor stream, natural mixing of vapor and reactive gas
components).
[0006] In a number of applications, such as coating of fibers and
metal foams, or formation of "zig-zag" structured thermal barrier
coatings (TBC's) for jet engines, the DVD process demonstrated
unique capabilities (non-line-of-sight coating, vapor utilization
efficiency) beyond those known from established PVD technologies.
However, it was also found in the course of investigations that DVD
at this stage was restricted to deposition of porous or columnar
microstructures. As in conventional EB-PVD, this is caused by the
limited kinetic energy of the thermally generated vapor atoms. In
the case of TBC's, a columnar structure is desired by the
engineering purpose. For other applications or also for certain
layers in the multilayer systems required in turbine blade coating,
however, dense structures are demanded.
[0007] Extensive development work previously done in conventional
PVD has shown that this goal can be achieved by combining the
thermal evaporation process with a plasma activation of the vapor.
The plasma facilitates that a remarkable fraction of the neutral
vapor particles will get ionized. The ions can then be accelerated
towards the substrate by the electrical fields within the plasma
sheath between the bulk plasma and the substrate's surface. These
fields are generally caused by the intrinsic self-bias potential of
the plasma but may also be enforced by an external bias voltage.
The enhanced kinetic energy of condensing particles results in
densification and improved adherence of the deposited layers. By
changing the plasma density, a wide range of layer modifications
can be created. Further, the plasma promotes the chemical activity
of reactive gases involved in deposition of compounds.
[0008] Calculations and experiments have revealed that only arc
sources deliver plasma, which is sufficiently dense and capable of
efficiently ionizing the vapor flux prevalent in high-rate coating.
For instance, an apparatus for plasma-assisted high-rate coating
has been described in the U.S. Pat. No. 5,635,087 (of which is
hereby incorporated by reference). It combines electron beam
evaporation with a plasma activation utilizing a transverse hollow
cathode arc discharge. The process appeared to be well suited even
for reactive deposition of insulating layers (oxides, nitrides)
onto cold plastic substrates.
[0009] This approach has been adopted for creating a
plasma-activation tool for the DVD process, too. Details of this
innovation have been fully described and disclosed in the U.S. Pat.
No. 7,014,889 (of which is hereby incorporated by reference). The
plasma-activated DVD process has proven to be capable of
high-efficient deposition and precise control of deposited
coatings' composition and morphology in a great variety of
applications including coatings of aircraft engine components and
semiconductor wafers, among other items. In aircraft applications,
coatings can be applied for both thermal and environmental
barriers, as well as oxidation and hot corrosion mitigation
coatings. Directed vapor deposition methods are also used to apply
titanium alloy coatings to silicon carbide monofilaments to make
titanium matrix composites, and to infiltrate silicon carbide fiber
performs with SiC to make (SiC/SiC) ceramic matrix composites. The
use of plasmas also greatly enhances vapor phase reaction rates
enabling the synthesis of hard materials such as titanium carbide
and various nitrides.
[0010] The conventional plasma assisted deposition process has
several drawbacks, however. First, the plasma source's working gas
emitted from the hollow cathode forms a high speed jet whose axis
is at right angles to the direction of vapor transport. Slow moving
or light (i.e. low momentum) vapor particles can be scattered away
from the substrate by the working gas jet of the hollow cathode.
Second, the conventional approach requires the use of high argon
working gas flow rates which has adverse economic consequences. It
also requires a more powerful vapor transporting gas jet which has
economic consequences because of the greater use of the helium gas
and need for higher capacity pumping systems. Third, there is no
means for sweeping the vapor plume from side to side (i.e. paint
spraying a large area surface) in the conventional arrangement
without significantly effecting the plasma properties. Fourth, the
conventional plasma generation approach provides inadequate
cleaning, etching, and heating properties for some applications
(i.e. the deposition of high temperature materials onto large area
substrates).
SUMMARY OF THE INVENTION
[0011] An embodiment of the present invention provides, among other
things, a plasma generation process that is more optimized for
vapor deposition processes in general, and particularly for
directed vapor deposition processing. An embodiment of the present
invention provides, among other things, the process of plasma
generation that is stable across a very wide range of background
pressures and in coexistence with the supersonic gas-vapor-jet. An
embodiment of the present invention is applicable to, among other
things, a very wide range of source materials and operates in the
presence of many different gases (both reactive and nonreactive)
including, but not limited to, inert gases, and inert gases doped
with nitrogen, methane, borane, etc.
[0012] In addition to these features, an embodiment of the present
invention provides, among other things, the approach that enables a
robust and reliable coaxial plasma capability in which the plasma
generating discharge is coaxial with the vapor plume, rather than
the orthogonal configuration creating the previous disadvantages.
In this way, the previous deformation of the vapor gas jet by the
work gas stream of the hollow cathode pipe is avoided and the
carrier gas consumption needed for shaping the vapor plume is
significantly decreased. Second, instead of only one large hollow
cathode pipe or slot, an annular arrangement of many small pipes
can be used. Individual control of working gas flow and current for
each pipe will enable the desired sweeping of the plasma plume in
sync with the vapor jet. Third, some of the design variants
described herein will contain means for magnetic tuning of the
discharge. This is aimed at further increasing the particle energy
as well as optimizing the spatial density distribution. Fourth, the
components of the new plasma system can be designed with enhanced
electric insulating capability up to the kV range. This will allow
for biasing the plasma source with respect to the chamber (and/or
substrate) and hence, performing heating or etching steps
conveniently.
[0013] An aspect of an embodiment of the present invention provides
an apparatus for applying at least one coating onto at least one
substrate. The apparatus may comprise: a deposition chamber; at
least one evaporant source, at least one energetic beam for
impinging the evaporant source; at least one hollow cathode aligned
at least substantially coaxially with the evaporant source for
delivering a discharge current; at least one plasma-forming gas
emitted from the hollow cathode; and at least one anode for
electrostatically attracting the discharge current from the hollow
cathode.
[0014] An aspect of an embodiment of the present invention provides
a method for depositing at least one evaporant onto at least one
substrate. The method may comprise: providing at least one
substrate; providing at least one evaporant source impinging the at
least one evaporant source with an energetic beam; discharging a
current that is aligned with the evaporant source; emitting a
plasma forming gas that is at least substantially aligned with the
evaporant source; electrostatically attracting the discharge
current; and interacting the plasma with the substrate.
[0015] An aspect of an embodiment of the present invention provides
a method or apparatus for depositing at least one evaporant onto at
least one substrate. The method may comprise (or the apparatus may
be configured for) the following: providing at least one
substrate;
[0016] providing at least one evaporant source; impinging the at
least one evaporant source with an energetic beam, providing a
plasma source and discharging a current that is at least
substantially coaxially aligned with the evaporant source; emitting
a plasma forming gas that is at least substantially coaxially
aligned with the evaporant source; electrostatically attracting the
discharge current; and interacting the plasma with the
substrate.
[0017] An aspect of an embodiment of the present invention provides
a method or apparatus for depositing at least one evaporant onto at
least one substrate. The method may comprise (or the apparatus may
be configured for) the following: providing at least one substrate;
providing at least one evaporant source; impinging the at least one
evaporant source with an energetic beam to generate a vapor plume;
generating a plasma and discharging a current that is aligned with
said vapor plume; emitting the generated plasma that is at least
substantially aligned with the vapor plume; electrostatically
attracting the discharge current; and interacting the plasma with
the substrate. Further, the discharge current may be changed as
desired to modulate and/or control the plasma density.
[0018] An aspect of an embodiment of the present invention provides
a method or apparatus for depositing at least one evaporant onto at
least one substrate. The method may comprise (or the apparatus may
be configured for) the following: providing at least one substrate;
providing at least one evaporant source; impinging the at least one
evaporant source with an energetic beam to generate a vapor plume;
generating a plasma and discharging a current that is aligned with
the vapor plume; emitting at least one plasma forming gas in a
direction that is at least substantially aligned with the vapor
plume; electrostatically attracting the discharge current towards
at least one anode; and interacting the plasma with the
substrate.
[0019] These and other objects, along with advantages and features
of various aspects of embodiments of the invention disclosed
herein, will be made more apparent from the description, drawings
and claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated into and
form a part of the instant specification, illustrate several
aspects and embodiments of the present invention and, together with
the description herein, serve to explain the principles of the
invention. The drawings are provided only for the purpose of
illustrating select embodiments of the invention and are not to be
construed as limiting the invention.
[0021] FIG. 1 is a longitudinal sectional schematic view of an
embodiment of the coaxial vapor deposition apparatus and
assembly.
[0022] FIG. 2 is a sectional schematic view of an embodiment of the
evaporation and plasma generation aspect of the plasma deposition
system.
[0023] FIG. 3 is a sectional schematic view of an embodiment where
the anode is positioned above the substrate.
[0024] FIG. 4 is a sectional schematic view of an embodiment where
the anode is positioned in the plane of the hollow cathode pipe
exits into the deposition chamber.
[0025] FIG. 5 is a sectional schematic view of an embodiment where
the anode is segmented to force individual discharges across the
central axis.
[0026] FIG. 6 is a sectional schematic view of an embodiment where
individual gas lines to each hollow cathode pipe are shown and a
coil is used for magnetic enhancement of the plasma.
[0027] FIG. 7 is a longitudinal schematic cross sectional view of
an embodiment of the coaxial vapor deposition apparatus and
assembly in a working form.
DETAILED DESCRIPTION OF THE INVENTION
[0028] Turning now to the drawings, an aspect of an embodiment of
the present invention, as shown in FIGS. 1-2, is a method and
apparatus 10 for applying at least one coating onto at least one
substrate 20 (e.g., sample), utilizing a plasma assisted directed
vapor deposition process. The apparatus 10 may include a deposition
chamber 30, having an upstream area 33, and downstream area 35, at
least one evaporant source 40, at least one energetic beam 50 for
impinging the evaporant source 40, at least one hollow cathode 60
aligned at least substantially coaxially with the evaporant source
40 for delivering a discharge current (not shown), at least one
plasma-forming gas 70 (e.g., working gas) emitted from the hollow
cathode 60, and at least one anode 80 for electrostatically
attracting the discharge current from the hollow cathode 60. At
least some of the elements included in the apparatus 10 may
comprise a "nozzle" 15, which may participate in applying at least
one coating to at least one substrate 20.
[0029] The energetic beam 50 may be produced by an electron beam
gun, a laser source, or any other device now or later appreciated
in the art. In the case of an electron beam gun, it may be operated
in either a low vacuum state, or at a reduced background pressure
(i.e. a high vacuum state). The electron beam gun may be
approximately a 70 kV/10 kW type, but not necessarily.
[0030] The anode 80 may be ring-shaped or annular, and may be
placed in an elevated position above the hollow cathode 60, which
may be inside a downstream chamber area 35 from the nozzle 15. This
positioning may prevent the anode 80 from being coated by vapor
from the vapor plume 90. Additionally, the anode 80 may be
positioned at an inclined angle, facing away from the vapor plume
90, which may advantageously prevent contamination from the vapor
plume 90. Additionally, the elevated positioning of the anode 80
may advantageously aid in attracting plasma in the direction of the
substrate 20, thus enhancing the overall efficiency of the vapor
deposition process.
[0031] A vapor plume 90 may be created by evaporation, via the
energetic beam 50, of a source material (the evaporant source) 40
which may be contained in a cooling device 42 for cooling the
evaporant source 40. The cooling device 42 may be a crucible, or
any other means now known or later appreciated in the art. While
the evaporant source 40 may generally be a solid, it should be
appreciated that it could also be in the form of a liquid. As a
solid, the evaporant source 40 may turn locally into a liquid upon
impingement of the energetic beam 50. Then, vaporization may occur
from a resulting "melt pool" (not shown). Some solid materials may
be vaporized by sublimation directly (i.e. without forming a melt
pool), and may not require a cooling device 42. Possible
modifications to the evaporant source 40 may include wires, bars,
granulates, or any other modification now known or later
appreciated. In a case where more than one evaporant source 40 may
be used, the evaporant source 40 may consist of different materials
in order to deposit compounds onto the substrate 20 via
"co-evaporation." Additionally, multiple evaporant sources 40 may
also exist if necessary.
[0032] Still observing FIGS. 1-2, the hollow cathode 60 may be
designed as the source of plasma, and may be designed to operate in
a high-current, low voltage arc mode and may be additionally
designed to emit electrons forming a low-voltage electron beam
(also known as the "cathode effect"). The cathode effect may be
created by arranging two or more hollow cathodes 60 substantially
coaxially around at least one evaporant source 40. In other words,
one or more evaporant sources 40 may be substantially coaxially
integrated inside the perimeter outlined by the two or more hollow
cathodes 60. The two or more hollow cathodes may be positioned in
an annular configuration around at least one evaporant source. For
example, the annular configuration may be any desired array. It
should be appreciated that the hollow cathodes may be a variety of
structures, including, but not limited to any one of the
followings: pipes, conduits, tubes, channels, hose, stems, ducts,
ports, grooves, passages, tunnels, ports, or the like as
desired.
[0033] In an embodiment (not shown), the hollow cathode 60 and its
cathode effect in the present invention may be realized by
positioning two coaxial cylinders, an inner cylinder (not shown),
and outer cylinder (not shown) of slightly different diameters to
form a continuous annular slot (not shown) from which a plasma jet
100 could be emitted. One or more evaporant sources 40 may be
substantially coaxially integrated inside the inner cylinder (not
shown).
[0034] The plasma forming gas 70, when emitted from the hollow
cathode 60, may form a plasma jet 100 (e.g., plasma region), which
may stream off of the hollow cathode's orifice 61. The axis 101
and/or momentum of the plasma jet 100 as well as the axis and/or
momentum of the hollow cathode's low voltage electron beam (not
shown) may be at least substantially aligned with the axis 64 of
the hollow cathode 60. When the hollow cathode 60 and corresponding
axis 64 are aligned with the evaporant-source-to-substrate vector
66, the plasma jet 100 may at least partially assist the
axisymmetric entrainment and transport of the vapor plume 90 to the
substrate 20, which may allow for the total gas that must be pumped
in the system (for high efficiency deposition) to be significantly
reduced. As discussed above, the plasma jet 100 may at least
partially entrain the vapor plume 90 and may at least partially
assist in transporting the vapor plume 90 towards the substrate 20.
The plasma jet 100 may also partially shape the vapor plume 90. At
least some of the vapor plume 90 may be ionized by the plasma jet
100 and by the hollow cathode's low voltage electron beam (not
shown).
[0035] An aspect of an embodiment of the present invention may also
include a bias voltage 57 applied to the substrate 20. By applying
a bias voltage 57 to the substrate 20, plasma particles from the
vapor plume 90 can be accelerated toward the substrate 20 to
enhance or perform various kinds of beneficial interactions with
the substrate 20. The bias voltage 57 may be DC, AC, unipolar or
bipolar pulsed voltage, or any other means now known or later
appreciated in the art.
[0036] A negative potential difference between the substrate 20 and
the plasma bulk will accelerate ions towards the substrate 20.
During a vapor deposition process and with the bias voltage 57 in
the range of approximately 0 V to approximately 250 V, one can
increase the mean energy of condensing particles aimed at improved
adhesion and quality (as measured, e.g., by packing factor,
density, degree of crystallinity) of the grown layer (plasma
activated deposition). When applied prior to a physical vapor
deposition (PVD), for example, coating process in a suitable gas
atmosphere (mostly Ar at approximately 0.5 Pa, for example) and
with the bias voltage 57 in the range of approximately 500 to
approximately 1000 V, sputtering occurs and removes impurities or
adsorbed layers thus cleaning the substrate surface (ion etching).
With specific parameter combinations, however, it is also possible
to embed (reactive) gaseous species into near-surface layers of the
substrate thus forming special interfaces for subsequent coating
(ion implantation).
[0037] If the substrate 20 is positively biased, plasma electrons
may be accelerated toward the substrate 20, providing a power
source for advantageous heating of the substrate 20.
[0038] The apparatus 10 may also comprise a means for initiating
the emission of a plasma jet 100 from the hollow cathode's orifice
61. The means may comprise a heat source based on Ohmic heating of
a current conductor, a heat source based on an auxiliary gas
discharge, a "kicker" circuit to ignite the hollow cathode plasma
emission via a high voltage impulse, or any other means now known
or later appreciated.
[0039] The desired arc discharge from the hollow cathode 60 may be
significantly sustained by thermionic and thermally-assisted field
emission of electrons from the hollow cathode 60. These means for
initiating plasma emission may require a high work temperature of
the hollow cathode 60 which may be established first to enable the
operation in arc mode afterwards. Initial heating of the cathode
may be achieved by resistive heating of the hollow cathode 60
itself or of an auxiliary radiation heater (not shown).
[0040] Alternatively, the hollow cathode 60 may be heated slowly by
a glow discharge which may burn at voltages comparable to or
slightly higher than the later arc mode voltage. Glow discharge may
require high plasma gas flows or an elevated pressure within the
deposition chamber 30 during the ignition phase.
[0041] Alternatively, the arc discharge from the hollow cathode 60
may also be initiated via a glow discharge heating phase at a later
desired gas flow and chamber pressure. There, the discharge may be
ignited by applying a voltage significantly higher (kV range) than
the final burning voltage in the arc mode. After ignition, the
transition to the low-voltage arc mode may occur rapidly. In that
situation, the high voltage usually may be provided as a short
impulse. This procedure may generally be referred to as a "kicker"
circuit. In that situation, after ignition, the cathode temperature
may be maintained by the arc discharge itself, and the additional
means for heating may be turned off.
[0042] As shown in FIGS. 1, 2 and 6, the apparatus 10 may further
comprise a solenoid 55 (e.g., solenoid coil) positioned coaxially
and at least partially proximal to the at least one hollow cathode
60. The solenoid 55 may be capable of at least partially bending
the energetic beam 50, and most effectively if the energetic beam
is, for example, an electron beam. The solenoid 55 may be
positioned and energized such as to magnetically enhance the
efficiency of the hollow cathode 60. Additionally, the solenoid 55
may at least partially increase plasma density and facilitate an
axial potential gradient for accelerating positive ions of the
plasma jet 100, or the vapor plume 90, or both toward the substrate
20. The solenoid 55 may also provide the ability to alter the beam
impingement points for the energetic beam 50 among one or more
evaporant sources 40. The use of a solenoid coil 55 may allow the
evaporation geometry to be changed to advantageously increase the
space available for positioning and manipulating complex shaped
substrates 20 and auxiliary heating 59 and biasing 57 subsystems.
Additionally, the placement of the solenoid 55 near the anode 80
may advantageously enhance the discharge voltage, and hence, the
particle energy. An embodiment of the apparatus 10, as shown in
FIG. 6, is arranged whereby individual gas lines providing the
plasma forming gas 70 (e.g., working gas) to each hollow cathodes
60 are shown and a coil 55 is used for magnetic enhancement of the
plasma.
[0043] Overall, the use of a solenoid coil 55 at least partially
proximal to at least one hollow cathode 60 may allow for an
increased ion saturation current at low gas flow through the hollow
cathode 60. The use may also provide elevated discharge voltages,
and therefore, higher electron temperatures, which is generally
advantageous for low-vacuum applications. Additionally, by
adjusting the current in the solenoid 55, it may be possible to
manipulate not only the ion saturation current, but also the
spatial distribution of the ions in the deposition chamber 30.
[0044] An aspect of an embodiment of the present invention may also
comprise means for the inlet of at least one secondary gas forming
at least one jet positioned at least substantially coaxially with
said at least one evaporant source and at least one hollow cathode.
The at least one secondary gas jets may at least partially assist
in shaping and transporting the vapor plume to the substrate. The
at least one secondary gas jets may also introduce reactant gases
for creating compounds with the evaporated material. Possible
embodiments include, but are not limited to, concentric arrangement
around the hollow cathode slot/multi jets, multi-jet array where
plasma and secondary gas jets alternate along a common circle line
around the evaporant sources, or slot-type or multi-jet gas nozzles
integrated into the annular anodes.
[0045] In an embodiment of the apparatus 310, shown in FIG. 3, the
anode 380 may be annular, and may be configured in an elevated
position above the at least one hollow cathodes 360. The plasma
forming gas 370 (e.g., working gas), when emitted from the hollow
cathode 360, may form a plasma jet 100 (e.g., plasma region). A
source material (not shown) such as the evaporant source, may be
contained in a cooling device 342. Furthermore, the anode 380 may
be positioned above the substrate 320 (for example, as shown), or
between the substrate 320 and hollow cathode 360 (not shown). This
later configuration may allow for the anode 380 to be
advantageously shielded from the vapor plume 390 by the substrate
320.
[0046] In an embodiment of the apparatus 410, shown in FIG. 4, the
anode 480 may be annular, and may be positioned at least coaxially
and in the same plane as the at least one hollow cathode 460. The
plasma forming gas 470 (e.g., working gas), when emitted from the
hollow cathode 460, may form a plasma jet 400 (e.g., plasma
region). A source material (not show), such as the evaporant
source, may be contained in a cooling device 442. Additionally, an
embodiment of the apparatus 510, shown in FIG. 5, the anode 580 may
be bisected radially, forming anode segments 581. The anode 580 may
be bisected into the same number (but not necessarily) of anode
segments 581 as the number of hollow cathodes 560. This may allow
for the emissions from the hollow cathodes 560 to burn
diametrically across the vapor plume 590 between each one of the
hollow cathodes 560 and the corresponding anode segment 581
situated at the opposite position. This diametric burning may drive
the emission of the hollow cathode 560 across the center of the
nozzle 515, which may increase the plasma density in regions where
the concentration of the vapor plume 590 is the highest. The plasma
forming gas 570 (e.g., working gas), when emitted from the hollow
cathode 560, may form a plasma jet 500 (e.g., plasma region). A
source material (not shown), such as the evaporant source, may be
contained in a cooling device 542.
[0047] The above configurations may provide the ability to control
the relative intensity of the plasma jets 100 generated by the
hollow cathodes 60 for optional directional aerodynamic sweeping
either of the plasma jet 100, or vapor plume 90, or both, from side
to side (i.e. spray coat a large surface area or different areas)
without significantly affecting the plasma properties This
directional aerodynamic sweeping may be accomplished by
systematically controlling the pressure or gas flow rates
individually in each hollow cathode 60, or any other means now
known or later appreciated in the art. In an embodiment of the
apparatus 710, as shown in FIG. 7, the anode 780 may further
comprise a means for magnetic plasma confinement by creating a
magnetic field (not shown) and guiding a magnetic flux (not shown)
such that the magnetic field lines in front of the anode 780 may be
substantially parallel to its surface and radially directed. This
is an exemplary embodiment of a working form wherein two or more
hollow cathode pipes are positioned in the upstream chamber of a
directed vapor deposition apparatus and the annular anode comprises
a magnetic circuit facilitating an anodic plasma layer. The
described magnetic field arrangement together with the electric
field strength directed substantially normal to the surface of the
anode 780 may produce a circular Lorentz force parallel to the
anode's surface 785 (F=E.times.B) which may advantageously create a
closed circumferential electron drift track. Along this track,
intensive ionization of the gas and vapor particles may occur. In
the vicinity of the anode 780, the magnetic field (not shown) will
diverge and may facilitate via ambipolar diffusion an axial
potential gradient for accelerating positive ions toward the
substrate (not shown). Furthermore, the use of magnetic plasma
confinement may advantageously provide for enhanced discharge
voltage resulting in an increase in the mean energy of the
discharge electrons to values which are close to the maximum in the
energy dependence of the cross section for electron impact
ionization. Suitable inclination angle of the anode 780,
appropriate shielding (not shown) and use of a clear gas flow (not
shown) shall ensure protection against contamination of the anode
surface 785 by stray vapor. As discussed previously, this
embodiment may include a deposition chamber 730, at least one
evaporant source 740, at least one energetic beam 750 for impinging
the evaporant source 740, at least one hollow cathode 760 for
delivering a discharge current (not shown), and at least one anode
780 for electrostatically attracting the discharge current from the
hollow cathode 760. At least some of the elements included in the
apparatus 710 may comprise a "nozzle" 715 acting as a flow resistor
which pressure-wise separates the upstream area 733 from the
downstream area 735, thus facilitating the generation of a directed
carrier gas stream as needed for vapor entrainment and for applying
at least one coating to at least one substrate 20. The plasma
forming gas 770 may be emitted from the hollow cathode 760.
[0048] Two or more hollow cathodes 760 of the plasma source may be
arranged around the evaporant source 740 as an annular multi-jet
array and placed below the nozzle 715 inside the upstream area 733.
The plasma forming gas 770 streaming off the hollow cathode 760 is
released into the upstream area 733 and acts then as a carrier gas
for vapor plume shaping upon directed expansion downstream into the
deposition chamber 730. Also provided may be any of the following
modules 795: power cable, water cooling, purging gas and coil
current. Also provided may be any of the following modules 797:
power cable and water cooling.
[0049] It should be appreciated that aspects of various embodiments
of the present invention system and method may be utilized for
applying a large variety of coatings, barriers, layers, films,
packaging, or other desired materials, or structures for, but not
limited thereto, the following: electronics, optics, engine
components, rotors, blades, desired structures or components,
packaging films, metalizing plastics for flexible electronics or
EMI shielding purposes, nanostructures, for depositing
scratch-proof, corrosion protection or decorative layers on various
raw materials, for controlling the electrical, optical and
tribological properties of components, tools and machine parts,
coatings of aircraft (or land or watercraft) engine components and
semiconductor wafers, among other items. In aircraft (or sea or
land crafts) applications, coatings can be applied for both thermal
and environmental barriers. Further, aspects of various embodiments
of the present invention system and method may be utilized for:
metalizing ceramic or other non-metallic (organic) metal matrix
composite reinforcing fibers; coating nanomaterials (particles,
rods, wires, and fibers, or the like); and growing nanowires for
opto-electric sensors.
[0050] The devices, systems, compositions, apparatuses, and methods
of various embodiments of the invention disclosed herein may
utilize aspects disclosed in the following references,
applications, publications and patents and which are hereby
incorporated by reference herein in their entirety:
[0051] International Patent Application No. PCT/US2008/073071,
filed Aug. 13, 2008, entitled "Thin Film Battery Synthesis by
Directed Vapor Deposition"; Haydn N. G. Wadley;
[0052] U.S. patent application Ser. No. 12/733,160, filed Feb. 16,
2010, entitled "Thin Film Battery Synthesis by Directed Vapor
Deposition"; Haydn N. G. Wadley;
[0053] International Patent Application No. PCT/US2006/025978,
filed Jun. 30, 2006, entitled "Reliant Thermal Barrier Coating
System and Related Methods and Apparatus of Making the Same"; Haydn
N. G. Wadley;
[0054] U.S. patent application Ser. No. 11/917,585, filed Dec. 14,
2007, entitled "Reliant Thermal Barrier Coating System and Related
Methods and Apparatus of Making the Same"; Haydn N. G. Wadley;
[0055] International Patent Application No. PCT/US2001/022266,
filed Jul. 16, 2001, entitled "Method And Apparatus For Heat
Exchange Using Hollow Foams and Interconnected Networks and Method
of Making the Same"; Haydn N. G. Wadley;
[0056] U.S. patent application Ser. No. 10/333,004, filed Jan. 14,
2003, entitled "Heat Exchange Foam"; Haydn N. G. Wadley, U.S. Pat.
No. 7,401,643, issued Jul. 22, 2008;
[0057] U.S. patent application Ser. No. 11/928,161, filed Oct. 30,
2007, entitled "Method and Apparatus for Heat Exchange Using Hollow
Foams and Interconnected Networks and Method of Making the Same";
Haydn N. G. Wadley;
[0058] International Patent Application No. PCT/US2005/000606,
filed Jan. 10, 2005, entitled "Apparatus and Method for Applying
Coatings onto the Interior Surfaces of Components and Related
Structures Produced Therefrom"; Haydn N. G. Wadley;
[0059] U.S. patent application Ser. No. 10/584,682, filed Jun. 28,
2006, entitled "Apparatus and Method for Applying Coatings onto the
Interior Surfaces of Components and Related Structures Produced
Therefrom"; Haydn N. G. Wadley;
[0060] International Patent Application No. PCT/US2004/024232,
filed Jul. 28, 2004, entitled "Method for Application of a Thermal
Barrier Coating and Resultant Structure Thereof"; Haydn N. G.
Wadley;
[0061] U.S. patent application Ser. No. 10/566,316, filed Feb. 14,
2006, entitled "Method for Application of a Thermal Barrier Coating
and Resultant Structure Thereof"; Haydn N. G. Wadley;
[0062] International Patent Application No. PCT/US2003/037485,
filed Nov. 21, 2003, entitled "Bond Coat for a Thermal Barrier
Coating System and Related Method Thereof"; Haydn N. G. Wadley;
[0063] U.S. patent application Ser. No. 10/535,364, filed May 18,
2005, entitled "Bond Coat for a Thermal Barrier Coating System and
Related Method Thereof"; Haydn N. G. Wadley;
[0064] International Patent Application No. PCT/US2003/036035,
filed Nov. 12, 2003, entitled "Extremely Strain Tolerant Thermal
Protection Coating and Related Method and Apparatus Thereof"; Haydn
N. G. Wadley;
[0065] U.S. patent application Ser. No. 10/533,993, filed May 5,
2005, entitled "Extremely Strain Tolerant Thermal Protection
Coating and Related Method and Apparatus Thereof"; Haydn N. G.
Wadley;
[0066] International Patent Application No. PCT/US2003/023111,
filed Jul. 24, 2003, entitled "Method and Apparatus for Dispersion
Strengthened Bond Coats for Thermal Barrier Coatings"; Haydn N. G.
Wadley;
[0067] U.S. patent application Ser. No. 10/522,076, filed Jan. 21,
2005, entitled "Method and Apparatus for Dispersion Strengthened
Bond Coats for Thermal Barrier Coatings"; Haydn N. G. Wadley;
[0068] International Patent Application No. PCT/US2003/012920,
filed Apr. 25, 2003, entitled "Apparatus and Method for Uniform
Line of Sight and Non-Line of Sight Coating at High Rate"; Haydn N.
G. Wadley;
[0069] U.S. patent application Ser. No. 10/512,161, filed Oct. 15,
2004, entitled "Apparatus and Method for Uniform Line of Sight and
Non-Line of Sight Coating at High Rate"; Haydn N. G. Wadley;
[0070] International Patent Application No. PCT/US2002/28654, filed
Sep. 10, 2002, entitled "Method and Apparatus for Application of
Metallic Alloy Coatings"; Haydn N. G. Wadley;
[0071] U.S. patent application Ser. No. 10/489,090, filed Mar. 9,
2004, entitled "Method and Apparatus Application of Metallic Alloy
Coatings"; Haydn N. G. Wadley;
[0072] International Patent Application No. PCT/US2002/13639, filed
Apr. 30, 2002, entitled "Method and Apparatus for Efficient
Application of Substrate Coating"; Haydn N. G. Wadley;
[0073] U.S. patent application Ser. No. 10/476,309, filed Oct. 29,
2003, entitled "Method and Apparatus for Efficient Application of
Substrate Coating"; Haydn N. G. Wadley;
[0074] International Patent Application No. PCT/US2001/16693, filed
May 23, 2001, entitled "A Process and Apparatus for Plasma
Activated Deposition In Vacuum"; Haydn N. G. Wadley;
[0075] U.S. patent application Ser. No. 10/297,347, filed Nov. 21,
2002, entitled "Process and Apparatus for Plasma Activated
Deposition in a Vacuum"; Haydn N. G. Wadley; U.S. Pat. No.
7,014,889, issued Mar. 21, 2006.
[0076] U.S. patent application Ser. No. 09/634,457, filed Aug. 7,
2000, entitled "Apparatus and Method for Intra-Layer Modulation of
the Material Deposition and Assist Beam and the Multilayer
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6,478,931, issued Nov. 12, 2002.
[0077] U.S. patent application Ser. No. 10/246,018, filed Sep.18,
2002, entitled "Apparatus and Method for Intra-layer Modulation of
the Material Deposition and Assist Beam and the Multilayer
Structure Produced Therefrom"; Haydn N. G. Wadley;
[0078] International Patent Application No. PCT/US2001/025158,
filed Aug. 10, 2001, entitled "Multifunctional Battery And Method
Of Making The Same"; Haydn N. G. Wadley;
[0079] U.S. patent application Ser. No. 10/110,368, filed Jul. 22,
2002, entitled "Multifunctional Battery and Method of Making the
Same"; Haydn N. G. Wadley; U.S. Pat. No. 7,211,348, issued May 1,
2007;
[0080] International Patent Application No. PCTUS1999/13450, filed
Jun. 15, 1999, entitled "Apparatus And Method For Producing Thermal
Barrier Coatings"; Haydn N. G. Wadley;
[0081] International Patent Application Publication No.
PCT/US1997/11185, filed Jul. 8, 1997, entitled "Production Of
Nanometer Particles By Directed Vapor Deposition Of Electron Beam
Evaporant"; Haydn N. G. Wadley;
[0082] U.S. patent application Ser. No. 08/679,435, filed Jul. 8,
1996, entitled "Production of Nanometer Particles by Directed Vapor
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Pat. No. 5,736,073, issued Apr. 7, 1998;
[0083] U.S. patent application Ser. No. 08/298,614, filed Aug. 31,
1994, entitled "Directed Vapor Deposition of Electron Beam
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[0084] U.S. Pat. No. 5,635,087, Schiller, et al., "Apparatus for
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[0085] In summary, while the present invention has been described
with respect to specific embodiments, many modifications,
variations, alterations, substitutions, and equivalents will be
apparent to those skilled in the art. The present invention is not
to be limited in scope by the specific embodiment described herein.
Indeed, various modifications of the present invention, in addition
to those described herein, will be apparent to those of skill in
the art from the foregoing description and accompanying drawings.
Accordingly, the invention is to be considered as limited only by
the spirit and scope of the following claims, including all
modifications and equivalents.
[0086] Still other embodiments will become readily apparent to
those skilled in this art from reading the above-recited detailed
description and drawings of certain exemplary embodiments. It
should be understood that numerous variations, modifications, and
additional embodiments are possible, and accordingly, all such
variations, modifications, and embodiments are to be regarded as
being within the spirit and scope of this application. For example,
regardless of the content of any portion (e.g., title, field,
background, summary, abstract, drawing figure, etc.) of this
application, unless clearly specified to the contrary, there is no
requirement for the inclusion in any claim herein or of any
application claiming priority hereto of any particular described or
illustrated activity or element, any particular sequence of such
activities, or any particular interrelationship of such elements.
Moreover, any activity can be repeated, any activity can be
performed by multiple entities, and/or any element can be
duplicated. Further, any activity or element can be excluded, the
sequence of activities can vary, and/or the interrelationship of
elements can vary. Unless clearly specified to the contrary, there
is no requirement for any particular described or illustrated
activity or element, any particular sequence or such activities,
any particular size, speed, material, dimension or frequency, or
any particularly interrelationship of such elements. Accordingly,
the descriptions and drawings are to be regarded as illustrative in
nature, and not as restrictive. Moreover, when any number or range
is described herein, unless clearly stated otherwise, that number
or range is approximate. When any range is described herein, unless
clearly stated otherwise, that range includes all values therein
and all sub ranges therein. Any information in any material (e.g.,
a United States/foreign patent, United States/foreign patent
application, book, article, etc.) that has been incorporated by
reference herein, is only incorporated by reference to the extent
that no conflict exists between such information and the other
statements and drawings set forth herein. In the event of such
conflict, including a conflict that would render invalid any claim
herein or seeking priority hereto, then any such conflicting
information in such incorporated by reference material is
specifically not incorporated by reference herein.
* * * * *