METHODS AND APPARATUSES FOR DEPOSITION OF ADHERENT CARBON COATINGS ON INSULATOR SURFACES

Abstract

Deposition of adherent carbon coating(s) on insulator surface(s) can include pretreatment of the insulator surface(s) in a pretreatment plasma (15) generated by a second power generator (11) in an auxiliary magnetic field in a second gas (14), and deposition of carbon coatings onto pretreated insulator surface(s) with the aid of a hollow cathode. The deposition onto the pretreated insulator surface(s) can include deposition by PVD from the hollow cathode simultaneously with PE CVD in a hollow cathode plasma (16) generated in a second gas (13). The second gas 13 can comprise one or more hydrocarbons. The insulator surfaces can include glass or ceramics.

Claims

1. A method of deposition, comprising: in a first phase, performing a plasma pretreatment of a surface of an insulator substrate (8) positioned on a substrate holder (7) in a pretreatment plasma (15) generated by a second power generator (11) electrically connected to said substrate holder (7) in an auxiliary magnetic field of at least about 0.01 Tesla generated by magnets (9) in a second gas (14), thereby forming a pretreated surface of said insulator substrate (8); and in a second phase, using a hollow cathode (3) electrically connected to a first power generator (5) to deposit a carbon coating on said pretreated surface of said insulator substrate (8) by at least one of physical vapor deposition (PVD) from said hollow cathode and plasma enhanced chemical vapor deposition (PE CVD) from a hollow cathode plasma (16) generated in a first gas (13) comprising one or more hydrocarbons and flowing through said hollow cathode (3), thereby forming an adherent carbon coating on said surface of said insulator substrate (8).

2. A method according to claim 1, wherein said insulator substrate (8) is positioned on a shielding (10) on said substrate holder (7) to shield a surface of said substrate holder (7) from said pretreatment plasma (15) and/or from said hollow cathode plasma (16).

3. A method according to claim 1, further comprising depositing said carbon coating on said pretreated surface of said insulator substrate (8) by said PVD and said PE CVD, wherein said PVD and said PE CVD are simultaneous.

4. A method according to claim 1, wherein said plasma pretreatment creates unsaturated bonds of surface atoms on said insulator substrate (8), and wherein said surface atoms include silicon, aluminum, or any combination thereof.

5. A method according to claim 1, further comprising (i) providing AC power having a frequency higher than about 1 kHz from said second power generator, and/or (ii) providing DC, pulsed DC, AC, pulsed AC, radio frequency or pulsed radio frequency power from said first power generator.

6. A method according to claim 1, wherein said second phase is continued until said adherent carbon coating has a coating thickness of greater than or equal to about 0.01 micrometers.

7. A method according to claim 1, wherein said insulator substrate (8) is part of a plurality of insulator substrates (8), and wherein said plurality of insulator substrates (8) are positioned on said substrate holder (7) and subjected to said first and second phases.

8. A method according to claim 1, further comprising maintaining a total gas pressure greater than about 0.01 Torr.

9. A method according to claim 1, wherein said insulator substrate is glass or a ceramic.

10. An apparatus for deposition, comprising (a) a chamber (1) containing a substrate holder (7) holding one or more insulator substrates (8), and at least one hollow cathode (3), and (b) magnets (9), wherein said apparatus is configured to deposit an adherent carbon coating on a surface of an insulator substrate (8) among said one or more insulator substrates (8) by implementing a method comprising: in a first phase, performing a plasma pretreatment of a surface of said insulator substrate (8) on said substrate holder (7) in a pretreatment plasma (15) generated by a second power generator (11) electrically connected to said substrate holder (7) in an auxiliary magnetic field of at least about 0.01 Tesla generated by said magnets (9) in a second gas (14) admitted into said chamber (1), thereby forming a pretreated surface of said insulator substrate (8); and in a second phase, using said at least one hollow cathode (3) electrically connected to a first power generator (5) to deposit a carbon coating on said pretreated surface of said insulator substrate (8) by at least one of physical vapor deposition (PVD) from said at least one hollow cathode and plasma enhanced chemical vapor deposition (PE CVD) from a hollow cathode plasma (16) generated in a first gas (13) comprising one or more hydrocarbons and flowing into said chamber (1) through said at least one hollow cathode (3), thereby forming said adherent carbon coating on said surface of said insulator substrate (8).

11. An apparatus according to claim 10, wherein said apparatus further comprises rotatable magnets (4) configured to generate a magnetic field in which said at least one hollow cathode (3) is positioned.

12. An apparatus according to claim 10, wherein (i) said second gas (14) comprises argon, neon, krypton, xenon, helium, hydrogen, or any combination thereof, or (ii) said first gas (13) is composed of a mixture of at least one noble gas with acetylene, methane, ethane and/or one or more other volatile hydrocarbons.

13. An apparatus according to claim 10, wherein said magnets (9) are embedded in said substrate holder (7).

14. An apparatus according to claim 10, wherein at least a portion of said second gas (14) is admitted into said chamber (1) through said hollow cathode (3).

15. An apparatus according to claim 10, wherein said hollow cathode (3) is electrically connected to said first power generator (5) by a first power switch (6), and/or wherein said second power generator (11) is electrically connected to said substrate holder (7) by a second power switch (12).

16. An apparatus according to claim 10, wherein said at least one hollow cathode (3) forms a system shaped to follow surface geometry of said one or more insulator substrates (8).

17. An apparatus according to claim 10, wherein said substrate holder (7) is configured to perform one or more motions with respect to said hollow cathode (3), and wherein said one or more motions include linear motion, rotational motion, stepwise motion, or any combination thereof.

18. An apparatus according to claim 10, wherein said at least one hollow cathode (3) includes a graphite hollow cathode.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0016] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings or figures (also “FIG.” and “FIGs.” herein), of which:

[0017] FIG. 1 is a schematic view of an example of an apparatus for application of a method of deposition of, for example, adherent carbon coatings on surfaces of insulator substrates.

[0018] FIG. 2a is a schematic view of an example of an apparatus for application of a method of deposition of, for example, adherent carbon coatings on surfaces of insulator substrates in a surface pretreatment phase of the method according to this invention.

[0019] FIG. 2b is a schematic view of an example of an apparatus for application of a method of deposition of, for example, adherent carbon coatings on surfaces of insulator substrates in a hollow cathode deposition of carbon films in a second phase of the method according to this invention.

[0020] FIG. 3 is a schematic view of an example of an apparatus for application of a method of deposition of, for example, adherent carbon coatings on surfaces of insulator substrates, where rotatable magnets at the hollow cathode are removed.

[0021] FIG. 4 is a schematic view of an example of an apparatus for application of a method of deposition of, for example, adherent carbon coatings on surfaces of insulator substrates, where a hollow cathode or several hollow cathodes form a system shaped to follow surface geometry of an insulator substrate.

[0022] FIG. 5 is a schematic view of an example of an apparatus for application of a method of deposition of, for example, adherent carbon coatings on surfaces of insulator substrates, where a rotatable substrate holder contains a system of embedded magnets.

DETAILED DESCRIPTION

[0023] Provided herein are methods and apparatuses for deposition of, for example, adherent carbon coatings on surfaces of insulator substrates (e.g., particularly on glass or ceramics, at gas pressure higher than about 0.01 Torr in a vacuum chamber, where simple mechanical pumps are sufficient to maintain the gas pressure). The methods described in the present disclosure are based on two subsequent phases, plasma pretreatment and plasma-assisted deposition of carbon coating. During plasma pretreatment the surface atoms on insulator substrates may acquire unsaturated bonds, which may lead to high surface reactivity and/or enhanced bonding with carbon particles formed during plasma deposition of carbon coatings in a dense hollow cathode generated plasma. The adherent carbon films can reach thicknesses of even more than ten micrometers, which is almost impossible without interface films in other methods. An additional advantage of the methods described herein is deposition by the hollow cathode plasma, which produces typically high density of charged particles and can perform very high rate of both PVD and PE CVD processes. Use of magnetic field causes better confinement of the plasma with reduced loss of charged particles. For the sake of purity of the coated films the interactions of plasmas with the substrate holder can be avoided or minimized in both pretreatment and deposition phases of the methods according to this invention. The substrate holder with substrates, the hollow cathodes or both can be moved with respect to each other, which can provide better uniformity of coating process. It is also possible to apply the pretreatment phase and the deposition phase of the present disclosure simultaneously, using an in-line arrangement of the plasma system with successively moving substrates on a moving holder. The substrate holder can also be provided with cooling and/or heating means.

[0024] Various aspects of the invention described herein may be applied to any of the particular applications set forth below or in any other type of plasma processing including, but not limited to combinations of several apparatuses according to this invention, or combinations with other types of plasma systems, such as, for example, with microwave plasma systems for plasma pretreatments and for assistance in carbon coating, or with arc evaporators, laser plasma sources, etc. The methods and systems described herein may be applied as a standalone method or system, or as part of an integrated processing system. It shall be understood that different aspects of the invention can be appreciated individually, collectively, or in combination with each other.

[0025] Adherent carbon coatings (also “adherent carbon films” herein) described herein may refer to carbon coatings comprising primarily carbon (e.g., greater than or equal to about 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5% or 99.9% carbon (C) content by weight, mole or volume). Such carbon coatings may comprise less than or equal to about 15%, 10%, 5%, 4%, 3%, 2%, 1%, 0.5% or 0.1% of an individual non-carbon material or of non-carbon materials in total (e.g., by weight, mole or volume). Further, such carbon coatings can display improved adherence (e.g., as measured by scratch tests performed, for example, by an indenter in progressive load mode, and analyzed using, for example, an optical microscope). For example, the carbon coatings described herein may withstand critical loads related to first damage(s) and/or to a complete coating failure of greater than or equal to about 1 Newton (N), 2 N, 5 N, 10 N, 15 N, 20 N, 25 N, 30 N, 35 N, 40 N, 45 N, 50 N, 55 N, 60 N, 65 N, 70 N, 75 N, 80 N, 85 N, 90 N, 95 N, 100 N, 110 N, 120 N, 130 N, 140 N, 150 N, 160 N, 170 N, 180 N, 190 N or 200 N. The adherent carbon coatings described herein may display such adherences at a thickness of greater than or equal to about 0.01 micrometer, 0.05 micrometer, 0.1 micrometer, 0.5 micrometer, 1 micrometer, 2 micrometers, 3 micrometers, 4 micrometers, 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 12 micrometers, 14 micrometers, 16 micrometers, 18 micrometers, 20 micrometers, 22 micrometers, 24 micrometers, 26 micrometers, 28 micrometers, 30 micrometers, 35 micrometers, 40 micrometers, 45 micrometers, 50 micrometers, 55 micrometers, 60 micrometers, 65 micrometers, 70 micrometers or 75 micrometers.

[0026] Reference will now be made to the drawings. Throughout the drawings, the same reference numbers refer to similar or corresponding elements or parts. It will be appreciated that the drawings and features therein are not necessarily drawn to scale.

[0027] Referring to FIGS. 1, 2a and 2b, an example of an apparatus for application of a method of deposition (e.g., at gas pressure higher than about 0.01 Torr) of adherent carbon coatings on surfaces of insulator substrates (e.g., particularly on glass or ceramics) in accordance with the present invention is described. The apparatus can comprise a chamber (e.g., vacuum chamber or hermetic chamber) 1. The chamber 1 may be pumped by one or more mechanical pumps 2 to a given gas pressure (e.g., total gas pressure). For example, the chamber 1 may be pumped by the one or more mechanical pumps 2 to a gas pressure of at least about 0.01 Torr. The apparatus comprises (e.g., the chamber 1 contains) a substrate holder 7 with insulator substrates 8, and a hollow cathode (e.g., graphite hollow cathode) 3 in a magnetic field generated by rotatable magnets 4. The insulator substrates 8 can be positioned on or carried by the substrate holder 7. The hollow cathode 3 can have an opening or outlet oriented toward the insulator substrates 8. The rotatable magnets 4 can be provided on opposite lateral sides of the hollow cathode 3. The substrate holder 7 can be movable (e.g., linearly) with respect to the hollow cathode 3. Moving members (not shown) may therefore be provided for moving any one or both of the substrate holder 7 and the hollow cathode 3. The holder 7 can be arranged with magnets 9 that create an auxiliary magnetic field of at least about 0.01 Tesla at surfaces (e.g., upper surfaces) of the insulator substrates 8. The magnets 9 may be provided, for example, adjacent to or as part of (e.g., embedded in) the holder 7. The holder 7 can be provided with cooling and/or heating means (not shown). The holder 7 is electrically connected to a second power generator 11 by a switch for the second power (also “second power switch” herein) 12 for generation of a pretreatment plasma 15 on the surfaces of the insulator substrates 8. The pretreatment plasma 15 is generated in at least one second gas 14 provided to the apparatus (e.g., admitted into the chamber 1). The apparatus comprises (e.g., the chamber 1 contains) at least one hollow cathode (e.g., graphite hollow cathode) 3 facing the insulator substrates 8. The cathode 3 is connected to a first power generator 5 by a switch for the first power (also “first power switch” herein) 6 to generate a hydrocarbon-containing hollow cathode plasma 16 in a hydrocarbon-containing first gas 13 provided to the apparatus (e.g., admitted into the chamber 1) through the hollow cathode (e.g., graphite hollow cathode) 3. The hydrocarbon-containing hollow cathode plasma 16 may be composed of carbon particles formed from the hollow cathode (e.g., graphite hollow cathode) 3, of hydrogen and/or carbon atoms and/or molecules and/or hydrocarbon radicals in neutral, ionized and/or excited states (e.g., formed from the first gas 13), or of any combination thereof. In the pretreatment phase of the methods described herein the second gas 14 for the pretreatment plasma 15 can be provided to the apparatus (e.g., admitted into the chamber 1) by a separate inlet or through the hollow cathode (e.g., graphite hollow cathode) 3 (e.g., instead of the first gas 13), or in parts using both ways. The second gas 14 admitted through each inlet may or may not be the same. The second gas (e.g., an individual second gas among several second gases) 14 can comprise one or more noble gases (e.g., argon, neon, krypton, xenon, and/or helium), hydrogen, or any combination thereof. The second gas 14 can be a mixture (e.g., a mixture containing one or more noble gases, hydrogen, or any combination thereof). The second gas 14 can comprise, for example, hydrogen, argon and/or other noble gases. The second gas 14 can comprise, for example, argon, neon, krypton, xenon, helium, hydrogen, or any combination thereof. For plasma pretreatment of insulator substrates 8 the second power generator 11 can deliver an AC power preferably with a frequency higher than about 1 kilohertz (kHz), 10 kHz, 100 kHz, 250 kHz, 500 kHz, 750 kHz, 1 megahertz (MHz), 5 MHz or 10 MHz. The first power generator 5 for generation of hydrocarbon-containing hollow cathode plasma 16 in the hollow cathode (e.g., graphite hollow cathode) 3 can be configured to generate DC, pulsed DC, AC, pulsed AC, radio frequency or pulsed radio frequency power.

[0028] Referring to FIG. 2a, an example of a first phase of the method of deposition of adherent carbon coatings on surfaces of insulator substrates (e.g., particularly on glass or ceramics) is described. In the first phase (also “pretreatment phase” herein) a plasma pretreatment of surfaces of the insulator substrates 8 on the substrate holder 7 can create unsaturated bonds of surface atoms, particularly silicon or aluminum, on the insulator substrates 8 in the pretreatment plasma 15 generated by the second power generator 11 delivering an AC power to the substrate holder 7 in an auxiliary magnetic field of at least about 0.01 Tesla generated by the magnets 9 in the at least one second gas 14. In this first phase the second power generator 11 is connected to the substrate holder 7 by the switch for the second power 12, and the first power generator 5 is disconnected from the hollow cathode (e.g., graphite hollow cathode) 3. To avoid possible contamination of surfaces of the insulator substrates 8 by particles from the substrate holder 7 during pretreatment in the pretreatment plasma 15, for example by sputtering of the surface of the substrate holder 7, the insulator substrates 8 can be positioned on a shielding 10 on the substrate holder 7 to shield the surface of the substrate holder 7 from the pretreatment plasma 15. The shielding (also “shielding on the substrate holder” herein) 10 can comprise or be of the same material as the insulator substrates 8 and/or one or more other suitable materials (e.g., any other material capable of preventing release of and/or contamination by particles from the substrate holder 7).

[0029] Referring to FIG. 2b, an example of a second phase of the method of deposition of adherent carbon coatings on surfaces of insulator substrates (e.g., particularly on glass or ceramics) is described. In the second phase (also “deposition phase” herein) a deposition of carbon coatings is performed on pretreated surfaces (e.g., the upper surfaces) of the insulator substrates 8 using the hollow cathode (e.g., graphite hollow cathode) 3 connected to the first power generator 5 by the switch for the first power 6, by, for example, physical vapor deposition (PVD) where carbon particles from the hollow cathode (e.g., graphite hollow cathode 3) are depositing (e.g., forming a coating) on the insulator substrates 8, simultaneously with plasma enhanced chemical vapor deposition (PE CVD) from the hydrocarbon-containing hollow cathode plasma 16 generated in the first gas 13 containing hydrocarbons and flowing through the hollow cathode (e.g., graphite hollow cathode) 3. The first gas 13 can comprise one or more noble gases, one or more hydrocarbons (e.g., volatile hydrocarbons), or any combination thereof. The first gas 13 can comprise, for example, argon, neon, krypton, xenon, helium, acetylene, methylacetylene, methane, ethane, propane, butane, ethylene, propylene, or any combination thereof. The first gas 13 can be composed of, for example, a mixture of at least one noble gas with acetylene, methane, ethane and/or one or more other volatile hydrocarbons. In the second phase the second power generator 11 is disconnected from the substrate holder 7 by the switch for the second power 12. To avoid possible contamination of growing films on surfaces of the insulator substrates 8 by particles from the substrate holder 7 during deposition in the hydrocarbon-containing hollow cathode plasma 16, for example by sputtering of the surface of the substrate holder 7 or by plasma reactive processes on the holder, the insulator substrates 8 can be positioned on the shielding 10 on the substrate holder 7 to shield the surface of the substrate holder 7 from the plasma 16. The second phase of the method can be started at the end of the first phase, or even before finishing of the first phase. In some cases both phases of the method according to this invention can be carried out simultaneously. In this case the second power generator 11 forms an AC bias on the surfaces of the insulator substrates 8 during deposition of carbon films. The second power generator 11 can deliver less than or equal to about 50% of the power from the first power generator 5.

[0030] Referring to FIG. 3, a schematic view of an example of an apparatus for application of a method of deposition of adherent carbon coatings on surfaces of insulator substrates 8 (e.g., particularly on glass or ceramics) in accordance with the present invention is explained. In this example the rotatable magnets 4 at the hollow cathode (e.g., graphite hollow cathode) 3 are removed and the cathode works without variable focusing magnetic field. This example also shows that the magnets 9 can be rotatable magnets in place of stationary magnets. Changes in intensity and geometry of magnetic field (e.g., generated by the magnets 9) can improve uniformity of the plasma pretreatment of substrates 8.

[0031] Referring to FIG. 4, a schematic view of another example of an apparatus for application of a method of deposition of adherent carbon coatings on surfaces of insulator substrates 8 (e.g., particularly on glass or ceramics) in accordance with the present invention is explained. This example shows a deposition phase of the method where the apparatus comprises four hollow cathodes (e.g., graphite hollow cathodes) 3 forming a system shaped to follow a curved (e.g., convex up) surface geometry of axially symmetric insulator substrate 8 positioned at substrate holder (also “holder” herein) 7 with geometry adjusted to the shape of the substrate 8. For example, the hollow cathodes may have openings or outlets oriented toward the insulator substrate(s) 8 and the geometry of the openings or outlets may correspond to (e.g., follow) the geometry of the insulator substrate(s) 8. The holder 7 can be rotatable. The holder 7 can be rotated (e.g., around an axis of the substrate holder 7) in order to improve spatial uniformity of at least one (e.g., both) of the pretreatment phase and the deposition phase of the coating process.

[0032] Referring to FIG. 5, a schematic view of another example of an apparatus for application of a method of deposition of adherent carbon coatings on surfaces of insulator substrates 8 (e.g., particularly on glass or ceramics) in accordance with the present invention is explained. This example shows a cross-sectional top view of an apparatus with rotatable substrate holder 7 with embedded regularly distributed magnets 9 and with four hollow cathodes (e.g., graphite hollow cathodes) 3 facing the holder. During rotation of the holder 7 the uniformity of both the pretreatment plasma 15 and the hydrocarbon-containing hollow cathode plasma 16 can be improved in both the pretreatment and the deposition phase of the coating process.

[0033] Implementations of the methods and apparatuses of the present disclosure can include maintaining a given gas pressure (or range of gas pressures). For example, the gas pressure (e.g., total gas pressure) can be greater than or equal to about 0.01 Torr, 0.02 Torr, 0.05 Torr, 1 Torr, 10 Torr, 50 Torr, 100 Torr, 200 Torr, 300 Torr, 400 Torr, 500 Torr, 600 Torr, 700 Torr, 760 Torr (1 atmosphere (atm)), 1.5 atm, 2 atm, 3 atm, 4 atm or 5 atm. The apparatuses described herein may comprise one or more components provided outside of a chamber. For example, the magnets 9 and/or the rotatable magnets 4 may be provided outside of a chamber. Any aspects of the present disclosure described in relation to such components contained in a chamber may equally apply to such components provided outside (or in absence) of a chamber.

[0034] The apparatuses of the present disclosure can comprise greater than or equal to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30, 40 or 50 hollow cathodes (also “cathodes” herein). The hollow cathode(s) (e.g., one hollow cathode or a plurality of hollow cathodes) may be shaped to complex geometri(es) and/or arranged in pattern(s) (e.g., in an array). The substrate holder may perform linear, rotational, stepwise, or other combined motions with respect to the hollow cathode(s). The hollow cathode(s) may perform linear, rotational, stepwise, or other combined motions with respect to the substrate holder. The substrate holder and the hollow cathode(s) may be movable with respect to each other through linear motion(s), rotational motion(s), stepwise motion(s), or any combination thereof. Such motion(s) may be in one, two or three dimensions (e.g., vertically, horizontally or a combination thereof). Any aspects of the present disclosure described in relation to surfaces of insulator substrates and/or adherent carbon coatings thereon may equally apply to a surface of an insulator substrate and/or an adherent carbon coating thereon, respectively, at least in some configurations, and vice versa.

[0035] It is to be understood that the terminology used herein is used for the purpose of describing specific embodiments, and is not intended to limit the scope of the present invention. It should be noted that as used herein, the singular forms of “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. In addition, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0036] While preferable embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

LIST OF USED REFERENCE NUMBERS

[0037] 1—chamber

[0038] 2—pumps

[0039] 3—hollow cathode

[0040] 4—rotatable magnets

[0041] 5—first power generator

[0042] 6—switch for the first power

[0043] 7—substrate holder

[0044] 8—insulator substrate(s)

[0045] 9—magnets

[0046] 10—shielding on the substrate holder

[0047] 11—second power generator

[0048] 12—switch for the second power

[0049] 13—first gas

[0050] 14—second gas

[0051] 15—pretreatment plasma

[0052] 16—hydrocarbon-containing hollow cathode plasma