Coaxial Hollow Cathode Plasma Assisted Directed Vapor Deposition and Related Method Thereof
20170236692 ยท 2017-08-17
Assignee
Inventors
- Haydn N. G. Wadley (Keswick, VA, US)
- Goesta Mattausch (Ullersdorf, DE)
- Henry Morgner (Dresden, DE)
- Frank-Holm Roegner (Dresden, DE)
Cpc classification
H01J37/32568
ELECTRICITY
H01J37/32357
ELECTRICITY
International classification
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.
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
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]
[0022]
[0023]
[0024]
[0025]
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[0027]
DETAILED DESCRIPTION OF THE INVENTION
[0028] Turning now to the drawings, an aspect of an embodiment of the present invention, as shown in
[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
[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
[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
[0046] In an embodiment of the apparatus 410, shown in
[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
[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;
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[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;
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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.