Patent Application: US-201013202828-A

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 .

Description:
turning now to the drawings , an aspect of an embodiment of the present invention , as shown in fig1 - 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 . 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 . 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 . 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 . still observing fig1 - 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 . 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 ). for example , referring to an embodiment as shown in fig8 , which is an alternative to fig3 ( discussed below ), it should be appreciated that such an approach may be applied to any of the embodiments disclosed or referenced herein . still referring to fig8 , the hollow cathode 360 and its cathode effect in an embodiment of the resent invention ma realized by positioning two coaxial cylinders , an inner cylinder 362 , and outer cylinder 363 of slightly different diameters to form there between a continuous annular slot 364 from which a plasma jet 300 could be emitted . one or more evaporant sources ( not shown ) may be substantially coaxially integrated inside the inner cylinder 362 . 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 &# 39 ; 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 &# 39 ; 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 &# 39 ; s low voltage electron beam ( not shown ). 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 . 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 ). 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 . the apparatus 10 may also comprise a means for initiating the emission of a plasma jet 100 from the hollow cathode &# 39 ; 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 . 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 ). 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 . 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 . as shown in fig1 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 fig6 , 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 . 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 . 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 . in an embodiment of the apparatus 310 having a nozzle 315 , shown in fig3 , 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 300 ( 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 . in an embodiment of the apparatus 410 having a nozzle 415 , shown in fig4 , 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 . also shown are a substrate 420 and vapor plume 490 . additionally , turning to an embodiment of the apparatus 510 , as shown in fig5 for use with a substrate 520 , 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 . 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 fig7 , 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 &# 39 ; s surface 785 ( f = e × 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 . 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 . 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 . 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 : international patent application no . pct / us2008 / 073071 , filed aug . 13 , 2008 , entitled “ thin film battery synthesis by directed vapor deposition ”; haydn n . g . wadley ; 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 ; 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 ; 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 ; international patent application no . pct / us2001 / 022266 , filed jul . 16 , 2001 , entitled “ method and apparatus for heat exchange using 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and non - line of sight coating at high rate ”; haydn n . g . wadley ; 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 ; 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 ; 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 ; 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 ; 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 ; u . s . 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electron beam evaporant ”; haydn n . g . wadley ; u . s . pat . no . 5 , 534 , 314 , issued jul . 9 , 1996 ; and u . s . pat . no . 5 , 635 , 087 , schiller , et al ., “ apparatus for plasma - assisted high rate electron beam vaporization ”, issued jun . 3 , 1997 . 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 . 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 .