Contact device, heating conductor holder, apparatus, and method for coating a substrate by means of CVD

Abstract

The invention relates to a contact device for an apparatus for coating a substrate (9) by means of CVD. The contact device comprises a heating conductor (5) and an electrode (1, 6) having a contact region. The heating conductor (5) is held mechanically tensioned by the action of a spring force and / or weight force and, due to the action of the spring force and / or weight force, experiences a contact force directed towards the electrode (1, 6), such that the heating conductor (5) touches the electrode (1, 6) in the contact region, forming a sliding contact (3a, 8a). The contact region consists of a first material and / or comprises the first material as a coating on a second material. The first material consists of 1 wt.% to 100 wt.% of metal which forms metastable carbides. The invention also relates to a heating conductor holder comprising at least one contact device according to the invention. Finally, the invention relates to: an apparatus comprising at least one contact device according to the invention or comprising at least one heating conductor holder according to the invention; and a method for coating a substrate (9) by means of CVD using the apparatus according to the invention.

Description

[0001] Contact device, heating conductor holder, device and method for coating a substrate by CVD

[0002] The invention relates to a contact device for a device for coating a substrate using CVD. Furthermore, the invention relates to a heating conductor holder comprising at least one contact device according to the invention. Finally, the invention relates to a device and a method for coating a substrate using CVD.

[0003] Devices and methods for coating substrates using CVD are known in the art. CVD stands for chemical vapor deposition. An exemplary device and method for coating substrates using CVD are known from German patent application DE 10 2008044 028 A1.

[0004] According to the state of the art, a heating element configured as a wire is heated using electrical power to activate the gas phase. This allows, for example, hydrogen radicals to be generated from hydrogen molecules on the hot surface of the wire. Due to the transfer of electrical power, a contact point or contact area of ​​an electrode that contacts the wire is also heated. This results in different thermal expansions and mechanical stresses between the wire and the contact point or contact area. To reduce these mechanical stresses, the wire is arranged in the state of the art so that it can move freely relative to the contact point or contact area.

[0005] However, the problem in the prior art is that sp can form on the surface of the wire and / or at the contact point or contact area of ​​the electrode in an activated carbon-containing gas atmosphere. 3-hybridized carbon accumulates in crystalline or amorphous form. Carbon crystals can accumulate in the form of diamond. sp 3 Hybridized carbon crystals have no or very low electrical conductivity. This undesirably increases the electrical resistance between the contact point or contact area and the wire. This makes the wire less effective at electrical heating. Using multiple wires results in an inhomogeneous current distribution among the individual wires, resulting in inhomogeneities when coating the substrate.

[0006] In the case of long-lasting coating processes or repeated coatings, the sp 3Crystals can form on the wire and the contact point or contact area. This limits the mobility of the wire relative to the contact point or contact area. This can lead to wire breakage. The wire's service life is thus limited. Frequent wire replacement is necessary. This is time-consuming and costly.

[0007] The object of the present invention is to eliminate the disadvantages of the prior art. In particular, a resource-saving, less complex, efficient and inexpensive method for coating a substrate by means of CVD is to be specified. Furthermore, a corresponding device for coating a substrate by means of CVD as well as a contact device and a heating conductor holder for such a device are to be provided. According to the invention, this object is achieved by a contact device according to the subject matter of claim 1, by a heating conductor holder according to the subject matter of claim 10, by a device according to the subject matter of claim 15 and by a method according to the subject matter of claim 17. Advantageous embodiments of the invention are specified in the dependent claims.

[0008] According to the invention, a contact device is claimed for a device for coating a substrate by means of CVD, in particular in a carbon-containing atmosphere with a carbon to oxygen ratio greater than 1 (i.e. C / O > 1) or a silicon-containing atmosphere with a silicon to oxygen ratio greater than 1 (i.e. Si / O > 1) or a carbon- and silicon-containing atmosphere with a total of more carbon and silicon than oxygen (i.e. (Si+C) / O > 1). The contact device comprises a heating conductor and an electrode. The electrode can be a positive or a negative pole. The polarity of the electrode can also change. For example, the electrode can alternate between being a positive and a negative pole. The electrode has a contact region.The heating conductor is held mechanically taut by the action of a spring force and / or weight and, due to the action of the spring force and / or weight, experiences a contact force directed towards the electrode, so that the heating conductor touches the electrode in the contact area, forming a sliding contact, in particular directly touches it. The heating conductor therefore forms an electrically conductive connection with the contact area of ​​the electrode. In particular, the contact device is designed such that a current can flow from the electrode via the contact area into the heating conductor, and / or that a current can flow from the heating conductor via the contact area into the electrode. The direction of the spring force and / or weight preferably forms an angle between 0° and 90°, more preferably an angle of 5 to 45°, particularly preferably an angle of 10 to 20°, with the direction of the longitudinal extent of the taut heating conductor.To generate the spring force, the heating conductor is preferably connected to a spring, preferably directly. Alternatively, the heating conductor can also be shaped into a spring at an initial section.

[0009] According to the invention, the contact area consists of a first material and / or the contact area has the first material as a coating on a second material.

[0010] The coating made of the first material can be provided all the way around the second material, for example in a cylindrical shape all the way around the second material. Furthermore, the coating made of the first material can be provided on one or more side surfaces of the second material over the entire area or in sections. Furthermore, the coating made of the first material can be provided on one or more edges of the second material all the way around or in sections. The edge or edges preferably run perpendicular or essentially perpendicular to the direction of the longitudinal extent of the heating conductor. The edge or one of the edges preferably directly touches the heating conductor. The heating conductor forms the sliding contact with the edge. In particular, the edge therefore forms the contact area.

[0011] The first material consists of 1 wt% to 100 wt% metal, which forms metastable carbides.

[0012] For the purposes of this application, "made of metal" is understood to mean "made of a metal and / or a metal alloy and / or a mixture of several metals." Instead of "metal that forms metastable carbides," the phrase "metal forming metastable carbides" is also used in this application. For the purposes of this application, a metal forming metastable carbides is understood to mean a metal and / or a metal alloy and / or a mixture of several metals that exhibits a positive carbide formation enthalpy, in particular a carbide formation enthalpy in the range of 0 to +40 kJ / mol, in a temperature range between 700°C and 1000°C, in particular at a temperature of 800°C. Metals with very large positive carbide formation enthalpies, in contrast, exhibit no carbide formation at all in the said temperature range.

[0013] The carbide formation enthalpy is a free enthalpy or Gibbs energy G. With a positive carbide formation enthalpy (AG > 0), metastable carbides can form in the coating atmosphere due to the high carbon activity, but immediately decompose back into the metal and graphite. This graphite formation has proven advantageous for the first contact material.

[0014] The metal that forms metastable carbides is preferably iron and / or nickel and / or cobalt and / or rhodium. The metal forming metastable carbides can, in particular, be a mixture of two, three, or four of the aforementioned elements. The carbide formation enthalpy of iron at 800 °C is +3 kJ / mol. The carbide formation enthalpy of cobalt at 800 °C is +7 kJ / mol. The carbide formation enthalpy of nickel at 800 °C is +26 kJ / mol. The carbide formation enthalpies at 800 °C can be determined according to the scientific publication SR Shatynski: The thermochemistry of transition metal carbides; Oxidation of Metals 13 (1979) 105-118.

[0015] The first material preferably consists of 1 wt.% to 100 wt.% of one metal or of several metals selected from iron, nickel, cobalt, and rhodium. A sliding contact is understood in particular to mean a contact without a firm fixation of the two contact materials involved to one another or without a firm connection between the two contact materials involved. A sliding contact within the meaning of the present application ensures free mobility of the two contact materials involved relative to one another, at least in the pm range. Preferably, a maximum relative movement from heating conductor to electrode is in the range of 1 pm to 10 mm. This advantageously allows contact between heating conductor and electrode to be maintained despite thermal expansion of the heating conductor.

[0016] The electrode preferably comprises a contact rail that forms the contact area. In this case, the heating conductor contacts the electrode at the contact rail. The contact rail can be made of the first material and / or have the first material coated on the second material. Furthermore, the electrode can have a support structure that supports the contact rail. The support structure can be made, at least in sections, of the second material and / or, at least in sections, of a third material. The support structure preferably consists of the second material or a third material.

[0017] The side of the contact rail facing the heating conductor preferably runs obliquely with respect to the direction of the longitudinal extent of the heating conductor. The side of the contact rail facing the heating conductor preferably forms an angle between 0° and 90°, preferably an angle of 5° to 45°, particularly preferably an angle of 25° to 35°, with the direction of the longitudinal extent of the heating conductor. Therefore, the heating conductor preferably only comes into contact with a protruding edge of the contact rail facing the heating conductor. The side of the contact rail facing the heating conductor can also run obliquely with respect to the direction of the longitudinal extent of the heating conductor only in sections. The side of the contact rail facing the heating conductor can, for example, have a concave or convex shape in the direction of the longitudinal extent of the heating conductor.The side of the contact rail facing the heating conductor can, for example, be rounded in the direction of the longitudinal extension of the heating conductor or have an elliptical shape.

[0018] The contact bar preferably forms an edge that runs perpendicular or substantially perpendicular to the direction of the heating conductor's longitudinal extension. The contact bar preferably directly touches the heating conductor with this edge. The heating conductor forms the sliding contact with the edge of the contact bar. In particular, the edge of the contact bar thus forms the contact area.

[0019] Preferably, the heating conductor comes into contact with the contact area essentially at only one point. Therefore, the term "contact area" can also be used as a contact point.

[0020] Advantageously, by designing the contact area from the first material in contact with a carbon-containing atmosphere, the formation of sp 3 -hybridized carbon is significantly reduced, and instead mainly sp 2 -hybridized carbon is formed. Sp 2 - hybridized carbon has a much better electrical conductivity than graphite 3 -hybridized carbon. In addition, sp 2 -hybridized carbon in the graphite structure forms mutually movable layers and can thus advantageously prevent the sliding contact from sticking. Furthermore, the formed sp 2Carbon can be etched away again by activated species from the gas phase, such as hydrogen radicals or oxygen. This advantageously prevents the heating conductor from growing together and the contact point or contact area. This preserves the mobility of the heating conductor relative to the contact point or contact area. The risk of the heating conductor breaking is significantly reduced. The heating conductor has a long service life. Thus, the complex and costly replacement of the heating conductor is only rarely necessary.

[0021] The contact device according to the invention advantageously ensures high electrical conductivity and advantageously enables high long-term stability and improved homogeneity.

[0022] Further advantageous embodiments of the invention are specified in the dependent claims.

[0023] According to an advantageous embodiment of the invention, the first material consists of at least 5 wt.% to 100 wt.%, preferably 10 wt.% to 100 wt.%, particularly preferably 60 wt.% to 100 wt.%, of metal which forms metastable carbides.

[0024] According to a further advantageous embodiment of the invention, the first material consists of at least 5 wt.% to 100 wt.%, preferably 10 wt.% to 100 wt.%, particularly preferably 60 wt.% to 100 wt.%, of one metal or several metals selected from iron, nickel, cobalt and rhodium.

[0025] According to a further advantageous embodiment of the invention, the first material consists of steel, preferably austenitic steel, particularly preferably austenitic chromium-nickel steel. The first material consists, for example, of a steel with 70 wt.% iron, 10 wt.% nickel, and 18 wt.% chromium, in particular the steel with the material number 1.4301. In the examples mentioned, the first material consists of approximately 80 wt.% metal, which forms metastable carbides.

[0026] In another example, the first material is a powder metallurgical material with an iron matrix.

[0027] According to a further advantageous embodiment of the invention, the second material contains less than 1 wt.%, preferably less than 1 per mille, of metal forming metastable carbides.

[0028] Preferably, the electrode is made of the second material outside the contact area. For example, the electrode may be formed from the second material and have the first material as a coating on the second material only in the contact area.

[0029] Outside the contact area, the electrode may alternatively or additionally consist of a third material. The third material contains less than 1 wt.%, preferably less than 1 per mille, of metastable carbide-forming metal.

[0030] The second material is preferably made of a metal with a melting point of more than 800°C and good thermal conductivity. Optionally, the third material is also preferably made of a metal with a melting point of more than 800°C and good thermal conductivity. According to a further advantageous embodiment of the invention, the second material is made of copper, preferably pure copper and / or a dispersion-strengthened copper material.

[0031] The third material is preferably made of copper, preferably pure copper and / or a dispersion-strengthened copper material. For example, the second material is made of pure copper and the third material is made of a dispersion-strengthened copper material.

[0032] The proposed dispersion-strengthened copper material is extremely dimensionally stable even at high temperatures. Furthermore, workpieces, especially profiles or hollow sections, can be easily and cost-effectively extruded from such a material and subsequently machined.

[0033] According to a further advantageous embodiment of the invention, the heating conductor is made of a carbide-forming metal, preferably of W, Ta, Mo, Hf, Nb or an alloy thereof, and / or of a carbide formed from a carbide-forming metal.

[0034] Carbide-forming metals include refractory metals, along with rhenium, osmium, and indium. Refractory metals are the nine naturally occurring elements from transition groups 4, 5, and 6, namely Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. The proposed materials are advantageously suited for the production of particularly thin wires and can also withstand high thermal stresses.

[0035] An example of a heating element made from an alloy of carbide-forming metals is a heating element made from a tungsten-tantalum alloy.

[0036] The carbides formed from a carbide-forming metal advantageously enable the production of particularly stable heating conductors. The heating conductor is preferably more than 50 wt.% carbide, particularly preferably 80 wt.% to 100 wt.% carbide.

[0037] The heating conductor can be made of a plurality of carbide-forming metals and / or a plurality of carbides each formed from a carbide-forming metal. In particular, the heating conductor can consist of a mixture or combination of at least two carbide-forming metals, a mixture or combination of at least two carbides formed from a carbide-forming metal, or a mixture or combination of at least one carbide-forming metal and at least one carbide formed from a carbide-forming metal.

[0038] According to a further advantageous embodiment of the invention, the heating conductor consists of a mixture or combination of a carbide-forming metal and / or a carbide formed therefrom with another carbide-forming metal and / or a carbide formed therefrom. The mixture or combination can be in the form of a coating. In particular, the heating conductor can have a coating of a carbide-forming metal and / or a carbide formed therefrom on another carbide-forming metal and / or a carbide formed therefrom. For example, the heating conductor has a coating of tantalum and / or tantalum carbide on tungsten and / or tungsten carbide.

[0039] For example, the heating conductor may have a coating of tantalum carbide on tungsten carbide. As another example, the heating conductor may have a coating of tantalum on tungsten. In this example, carbide formation may occur, so that the tantalum coating is converted to tantalum carbide on its outer surface or completely. As another example, the heating conductor may have a coating of tantalum on tungsten carbide. In this example, carbide formation may also occur, so that the tantalum coating is converted to tantalum carbide on its outer surface or completely.

[0040] Heating conductors made of tantalum or tantalum carbide, or heating conductors coated with tantalum or tantalum carbide, advantageously enable the achievement of high temperatures with comparatively low thermal radiation. This allows hydrogen radicals to be generated particularly efficiently.

[0041] According to a further advantageous embodiment of the invention, the heating conductor has a circular or polygonal, in particular rectangular, cross-section.

[0042] The heating conductor is preferably designed as a wire. However, it can also be designed as a strip, rod, plate, sheet, or foil.

[0043] The heating conductor, particularly one designed as a strip, rod, plate, sheet, or foil, can have a plurality of holes. The heating conductor can be designed, for example, as a perforated sheet or expanded metal. Gas can flow through a perforated heating conductor. This allows for improved transport of an activated process gas. This can advantageously further improve the homogeneity when coating a substrate using CVD.

[0044] A diameter or cross-sectional area of ​​the heating conductor does not have to be the same over its entire longitudinal extent.

[0045] The heating conductor preferably does not have a smooth surface. The heating conductor may have a rough surface structure with notches and / or cracks. It has been shown that such a rough surface structure advantageously increases the efficiency of a process for coating a substrate using CVD. This may be due to the fact that such a rough surface structure increases the effective surface area of ​​the heating wire, thereby increasing the formation of hydrogen radicals.

[0046] According to a further advantageous embodiment of the invention, the heating conductor has a maximum cross-sectional dimension and / or a diameter of less than 1 cm, preferably from 5 to 500 μm, particularly preferably from 100 to 300 μm. The heating conductor preferably has a length of 5 cm to 100 cm, preferably the heating conductor has a length of 10 cm to 60 cm, particularly preferably the heating conductor has a length of 15 cm to 40 cm.

[0047] According to a further advantageous embodiment of the invention, the heating conductor configured as a strip, rod, plate, sheet, or foil has a maximum cross-sectional dimension of less than 100 cm, preferably 10 cm, particularly preferably 100 μm to 1 cm. Preferably, the heating conductor configured as a strip, rod, plate, sheet, or foil also has a maximum length of 100 cm.

[0048] For example, the heating conductor is designed as a 5 mm wide foil. In another example, the heating conductor is designed as a 200 μm thick wire with a circular or substantially circular cross-section.

[0049] Especially when using heating conductors with a small diameter or a small maximum cross-section, a high heating conductor temperature can be achieved at low current flows, which promotes the formation of hydrogen radicals. Particularly good long-term stability and homogeneity can be achieved.

[0050] According to the invention, a heating conductor holder for a device for coating a substrate by means of CVD, in particular in a carbon-containing atmosphere with a carbon to oxygen ratio greater than 1 (ie C / O > 1) or a silicon-containing atmosphere with a silicon to oxygen ratio greater than 1 (ie Si / O > 1) or a carbon- and silicon-containing atmosphere with a total of more carbon and silicon than oxygen (ie (Si+C) / O > 1)) is claimed. The heating conductor holder comprises at least one contact device according to the invention.

[0051] The heating conductor holder preferably comprises a plurality of contact devices according to the invention, preferably 2 to 200, particularly preferably 20 to 140 contact devices according to the invention. The heating conductor holder preferably comprises two electrodes and a plurality of heating conductors. The two electrodes preferably form a contact device with each heating conductor. However, for example, only one of the two electrodes can form a contact device with each heating conductor. Contact devices can therefore be formed on both electrodes or only on one electrode of the heating conductor holder.

[0052] Furthermore, not every heating conductor has to form a contact device with one electrode or each has to form a contact device with both electrodes.

[0053] The two electrodes preferably run parallel to each other.

[0054] In particular, contact rails formed by both electrodes preferably run parallel to one another. Furthermore, edges formed by both contact rails preferably run parallel to one another. The two edges preferably protrude from the respective contact rail and each face the heating conductors. Each heating conductor preferably forms a sliding contact with each of the two edges.

[0055] Thanks to the contact device(s) according to the invention, the heating conductor holder according to the invention advantageously also ensures permanently high electrical conductivity. Providing multiple heating conductors results in a homogeneous current distribution among the individual heating conductors. This advantageously allows the substrate to be coated homogeneously.

[0056] Advantageously, the fusion of the heating conductor and the contact point or contact area can be prevented. This preserves the flexibility of the heating conductor relative to the contact point or contact area. The heating conductors therefore have a long service life. This advantageously means that the time-consuming and costly replacement of the heating conductors in the heating conductor holder is rarely necessary.

[0057] The inventive design of the contact device or the heating conductor holder allows for a very long operating time when coating a substrate using CVD, ranging from 100 to 500 hours, particularly from 200 to 500 hours. The operating time can refer to a single individual run, with the operating time being equal to the dwell time of the individual run, or to several individual runs, with the operating time being the sum of the respective dwell times. This advantageously allows coatings with diamond, silicon, or silicon carbide to be produced with little effort and low cost.

[0058] According to an advantageous embodiment of the invention, the heating conductor holder comprises a first and a second electrode and a plurality of heating conductors each extending between the first and the second electrode. The first and / or the second electrode has a plurality of contact areas. The heating conductors are each held mechanically tensioned by the action of a spring force and / or weight and, due to the action of the spring force and / or weight, each experience a contact force directed towards the first electrode and / or a contact force directed towards the second electrode, so that each individual heating conductor touches, in particular directly touches, the first and / or the second electrode in a contact area assigned to that heating conductor, forming a sliding contact. Each heating conductor therefore forms an electrically conductive connection with the contact area of ​​the first and / or second electrode assigned to it.In particular, the heating conductor holder is designed such that a current can flow from the first and / or second electrode via the respectively assigned contact area into the respective heating conductors, and / or that a current can flow from the respective heating conductor via the respectively assigned contact area into the first and / or second electrode.

[0059] The direction of the spring force and / or weight force preferably forms an angle between 0° and 90°, preferably an angle of 5 to 45°, particularly preferably an angle of 10 to 20°, with the direction of the longitudinal extension of the respective heating conductor. To generate the spring force, each heating conductor is preferably connected to a spring, preferably directly connected. However, several heating conductors, preferably two heating conductors, can also be connected to a common spring, preferably directly connected. Alternatively, the heating conductors can also be formed into a spring at an initial section.

[0060] The contact areas each consist of the first material and / or have the first material as a coating on the second material. The coating made of the first material can be provided circumferentially around the second material, for example cylindrically circumferentially around the second material. Furthermore, the coating made of the first material can be provided over the entire area or in sections on one or more side surfaces of the second material. Furthermore, the coating made of the first material can be provided completely or in sections on one or more edges of the second material. The first material consists of 1% to 100% by weight of metal, which forms metastable carbides. Each individual heating conductor forms a contact device according to the invention with the first and / or the second electrode.With N heating conductors, 2N contact devices according to the invention (in the event that both electrodes each form contact devices according to the invention with the heating conductors) or N contact devices according to the invention (in the event that only one of the two electrodes forms contact devices according to the invention with the heating conductors) are formed in the heating conductor holder. The first and / or the second electrode can have several or all of the optional features listed for the electrode of the contact device. The first and the second electrode can have the same features. Preferably, the first electrode has different features than the second electrode. The heating conductors can have several or all of the optional features listed for the heating conductor of the contact device. Different heating conductors can have different features. Preferably, all heating conductors have the same features.

[0061] Preferably, the first and / or second electrode is made of the second material outside the contact areas. The first and / or second electrode can, for example, be formed from the second material and have the first material as a coating on the second material only in the contact areas.

[0062] The first and / or the second electrode may alternatively or additionally consist of a third material outside the contact areas, wherein the third material contains less than 1 wt.%, preferably less than 1 per mille, of metal forming metastable carbides.

[0063] Preferably, the first electrode comprises a contact rail and / or the second electrode comprises a contact rail. The contact rail forms (in each case) the contact areas. The contact rail can (in each case) consist of the first material and / or have the first material as a coating on the second material. Furthermore, the first and / or the second

[0064] The electrode may have a support structure that supports the contact rail. The support structure is preferably made of the second and / or third material.

[0065] The side of the contact rail facing the heating conductors preferably runs at least partially obliquely with respect to the direction of the longitudinal extension of the respective heating conductor. The side of the contact rail facing the heating conductors preferably forms an angle between 0° and 90°, preferably an angle of 5° to 45°, and particularly preferably an angle of 25° to 35°, with the direction of the longitudinal extension of the respective heating conductor. Therefore, the heating conductors preferably only come into contact with a protruding edge of the contact rail facing the heating conductors.

[0066] It is possible for the first or second electrode not to form a contact device according to the invention. The electrode not forming a contact device according to the invention is preferably formed from the second and / or third material.

[0067] It is possible for the first electrode to comprise a first contact rail and the second electrode to comprise a second contact rail, wherein the first contact rail is made of the first material and / or has the first material as a coating on the second material, and wherein the second contact rail is made of the second and / or a third material. Alternatively, it is possible for the second contact rail to be made of the first material and / or has the first material as a coating on the second material, and for the first contact rail to be made of the second and / or the third material.

[0068] Furthermore, it is possible for the first electrode to comprise a first support structure and the second electrode to comprise a second support structure. The first support structure supports the first contact rail. The second support structure supports the second contact rail. Preferably, the first support structure consists at least in sections of the second and / or at least in sections of the third material. Preferably, the second support structure consists at least in sections of the second and / or at least in sections of the third material.

[0069] For example, the first contact rail is made of the second material, e.g. pure copper, the first support structure is made of the third material, e.g. a dispersion-strengthened copper material, the second contact rail is made of the first material, e.g. austenitic chromium-nickel steel, and the second support structure is made of the third material, e.g. a dispersion-strengthened copper material.

[0070] Two or more adjacent heating conductors can be formed integrally together. In particular, all heating conductors of the plurality of heating conductors can be formed integrally together. In this case, several or all heating conductors of the plurality of heating conductors can be formed from just one wire. For this purpose, the wire preferably has a bend beyond the sliding contact. The bend preferably has an LI shape. Preferably, the bend is connected to one or more springs for exerting the spring force on the wire or to a weight for exerting the weight force on the wire. For the purposes of this application, each individual section of such a wire extending from the first to the second electrode is referred to as a heating conductor.

[0071] The heating conductors can each consist of individual wires. For example, it is also possible for some heating conductors to be formed from a single wire, while the remaining heating conductors each consist of individual wires. The heating conductor holder preferably has 1 to 100 heating conductors; more preferably, the heating conductor holder has 10 to 70 heating conductors.

[0072] Adjacent heating conductors preferably run parallel to each other. Particularly preferably, all heating conductors run parallel to each other. However, it is also possible for heating conductors to be aligned at different angles. Adjacent heating conductors are preferably spaced between 0.5 cm and 4 cm, particularly preferably between 1 cm and 2 cm.

[0073] According to a further advantageous embodiment of the invention, the heating conductor holder is designed as a module. The first and second electrodes are preferably firmly connected relative to one another and form a structural unit. Such a structural unit is expediently designed so that it can be arranged in a conventional housing of a CVD coating device.

[0074] For this purpose, the heating conductor holder preferably comprises supports and electrical insulation means. The first and second electrodes are preferably mechanically connected to one another via the supports and with the interposition of the electrical insulation means. For this purpose, the supports and the electrical insulation means are attached, for example, laterally to the first and second electrodes. The supports are preferably formed from the second material and / or the third material. For example, the supports are made from a dispersion-strengthened copper material.

[0075] The heating conductor holder preferably forms a frame structure comprising the first and second electrodes, the supports, and the electrical insulation means. The frame structure is preferably formed at least partially from the second material and / or at least partially from the third material. For example, the frame structure is made of a dispersion-strengthened copper material. The proposed dispersion-strengthened copper material is extremely dimensionally stable even at high temperatures. Furthermore, workpieces, in particular profiles or hollow profiles, can be easily and cost-effectively extruded from such a material and subsequently machined.

[0076] According to a further advantageous embodiment of the invention, a cooling device is provided for cooling the first and / or second electrode.

[0077] For this purpose, the first and / or second electrode and / or the supports and / or the frame structure of the heating conductor holder can, for example, at least partially comprise a hollow profile through which a cooling fluid flows. The cooling fluid is expediently water.

[0078] Alternatively or additionally, the first and / or second electrode and / or the supports and / or the frame structure of the heating conductor holder may have cooling fins.

[0079] Furthermore, the cooling device can comprise a cooling element which is in direct thermal contact with the first and / or second electrodes, or which cools the first and / or second electrodes via thermal radiation.

[0080] According to a further advantageous embodiment of the invention, the heating conductor holder extends in a plane or has a bend and / or a cylindrical shape and / or a conical shape.

[0081] The heating conductor holder can be adapted to the shape of the substrate to be coated. Advantageously, differently shaped substrates can thus be coated. According to the invention, a device for coating a substrate by means of CVD, in particular for coating with diamond or silicon or silicon carbide, in particular in a carbon-containing atmosphere with a carbon to oxygen ratio greater than 1 (i.e. C / O > 1) or a silicon-containing atmosphere with a silicon to oxygen ratio greater than 1 (i.e. Si / O > 1) or a carbon- and silicon-containing atmosphere with a total of more carbon and silicon than oxygen (i.e. (Si+C) / O > 1) is claimed. The device comprises a housing in which at least one contact device according to the invention and / or at least one heating conductor holder according to the invention are provided.

[0082] Preferably, heating conductor holders according to the invention are provided in the housing of the device according to the invention 1 to 12. Particularly preferably, one heating conductor holder according to the invention or two or four heating conductor holders according to the invention are provided.

[0083] Preferably, 1 to 2000 contact devices according to the invention and / or 1 to 1000 heating conductors according to the invention are provided in the housing of the device according to the invention.

[0084] The housing is preferably designed to be gas-tight. A pump is preferably provided for evacuating the housing. Furthermore, the housing preferably comprises a gas inlet for introducing the reaction gases.

[0085] The heating conductor holder(s) is / are preferably connected (each) to a power source for heating the heating conductors. The power source(s) preferably provides a power such that a power per mm averaged over the longitudinal extent of the heating conductor(s) 2 at a height of 0.5 W / mm 2 up to 10 W / mm 2 , particularly preferably at a level of 1 W / mm 2 up to 2.5 W / mm 2, on the surface of the heating conductor(s). The device according to the invention advantageously enables a permanently high electrical conductivity when coating a substrate using CVD by providing the contact device(s) according to the invention and / or the heating conductor holder(s) according to the invention. This results in a homogeneous current distribution among the individual heating conductors. This advantageously allows the gas surrounding the heating conductors to be homogeneously excited and the substrate to be homogeneously coated.

[0086] Advantageously, the fusion of the heating conductor and the contact point or contact area can be prevented. This preserves the flexibility of the heating conductor relative to the contact point or contact area. The heating conductors therefore have a long service life. This advantageously means that the time-consuming and costly replacement of the heating conductors in the heating conductor holder is rarely necessary.

[0087] The device according to the invention allows for a very long operating time when coating a substrate using CVD, ranging from 100 to 500 hours, particularly from 200 to 500 hours. The operating time can refer to a single individual run, where the operating time is equal to the dwell time of the individual run, or to several individual runs, where the operating time is the sum of the respective dwell times. This advantageously allows coatings with diamond, silicon, or silicon carbide to be produced with little effort and low cost.

[0088] According to a further advantageous embodiment of the invention, at least one heating conductor holder is arranged in the device in such a way that the direction of the longitudinal extension of the heating conductors runs along the direction of gravity.

[0089] Preferably, all heating conductors run parallel to each other.

[0090] For example, one heating conductor holder can be provided in the device and arranged such that the direction of the longitudinal extension of the heating conductors runs along the direction of gravity. In another example, several heating conductor holders can be provided in the device and arranged such that the direction of the longitudinal extension of the heating conductors runs along the direction of gravity. For example, two heating conductor holders are provided in the device and arranged such that the direction of the longitudinal extension of the heating conductors runs along the direction of gravity. In this example, the substrate can be arranged between the two heating conductor holders in such a way that it can be coated on both sides.

[0091] According to a further advantageous embodiment of the invention, at least one heating conductor holder is arranged in the device such that the longitudinal extension of the heating conductors runs transversely to the direction of gravity. In this case, the longitudinal extension and the direction of gravity are at an angle of 90°.

[0092] The at least one heating conductor holder can be arranged in the device in such a way that the electrodes and / or the contact rails formed by the electrodes and / or the edges formed by the contact rails run along the direction of gravity. In another embodiment, the at least one heating conductor holder can be arranged in the device in such a way that the electrodes and / or the contact rails formed by the electrodes and / or the edges formed by the contact rails run transversely to the direction of gravity. For example, a heating conductor holder can be provided in the device and arranged in such a way that the direction of the longitudinal extent of the heating conductors runs transversely to the direction of gravity, and that the two electrodes and / or the two contact rails formed by the electrodes and / or the two edges formed by the contact rails run transversely to the direction of gravity.In this example, the heating conductor holder is arranged horizontally. In this example, the substrate can be arranged below the heating conductor holder in the direction of gravity, so that it can be coated on one side. However, it is also possible for the at least one heating conductor holder to be arranged in the device such that the electrodes and / or the contact rails formed by the electrodes and / or the edges formed by the contact rails extend at an angle between 0° and 90° to the direction of gravity.

[0093] According to a further advantageous embodiment of the invention, at least one heating conductor holder is arranged in the device such that the longitudinal extension of the heating conductors forms an angle between 0° and 90° with the direction of gravity. Several heating conductor holders can also be arranged in the device such that the heating conductor holders are each tilted toward a centrally located substrate.

[0094] According to the invention, a method for coating a substrate by CVD, in particular for coating with diamond or silicon or silicon carbide, is claimed. The following steps are carried out using an apparatus according to the invention: a) generating a reactive gas atmosphere containing hydrogen and a gaseous carbon and / or silicon carrier in the housing; b) heating the heating conductors from ambient temperature to a temperature in the range of 1500°C to 2600°C for a holding time of 0.1 to 500 hours by applying electrical power to the heating conductors; c) removing the electrical power.

[0095] The steps mentioned are preferably carried out in the order mentioned. The reactive gas atmosphere containing a gaseous carbon carrier and produced in step a) preferably has a carbon to oxygen ratio greater than 1 (i.e. C / O > 1). The reactive gas atmosphere containing a gaseous silicon carrier and produced in step a) preferably has a silicon to oxygen ratio greater than 1 (i.e. Si / O > 1). The reactive gas atmosphere containing a gaseous carbon carrier and a gaseous silicon carrier and produced in step a) preferably has a total of more carbon and silicon than oxygen (i.e. (Si+C) / O > 1).

[0096] Preferably, a heating conductor originally consisting of a carbide-forming metal or a heating conductor comprising a carbide-forming metal as a coating is converted during step b) on its outer surface or completely into a carbide formed from the carbide-forming metal. Heating conductors made of carbides formed from a carbide-forming metal are advantageously particularly stable.

[0097] When the electrical power is removed, the heating elements cool down. Preferably, the heating elements cool down to ambient temperature.

[0098] Preferably, the housing is evacuated during or after the cooling of the heating conductors. Alternatively to evacuating the housing or after evacuating the housing, the housing is preferably ventilated. After ventilating the housing, the coated substrate(s) are preferably removed.

[0099] The heating elements can be cooled in a reactive gas atmosphere. Alternatively, the heating elements can be cooled using a cooling gas. The cooling gas can be, for example, nitrogen, helium, hydrogen, and / or argon. Alternatively, the heating elements can be cooled to ambient temperature in a vacuum. After the heating elements have cooled to ambient temperature, the housing is preferably ventilated. The coated substrate(s) are then removed.

[0100] In the method according to the invention, a high level of electrical conductivity can advantageously be permanently provided at the contact device(s) according to the invention or at the heating conductor holder(s) according to the invention. This results in a homogeneous current distribution among the individual heating conductors. This advantageously allows the gas surrounding the heating conductors to be homogeneously excited and the substrate to be coated homogeneously.

[0101] Advantageously, the fusion of the heating conductor and the contact point or contact area can be prevented. This preserves the flexibility of the heating conductor relative to the contact point or contact area. The heating conductors therefore have a long service life. This advantageously means that the time-consuming and costly replacement of the heating conductors in the heating conductor holder is rarely necessary.

[0102] The inventive design of the contact device(s) or the heating conductor holder(s) allows a very long operating time in the range of 100 to 500 hours, in particular in the range of 200 to 500 hours. The operating time can refer to a single individual run, whereby the operating time is equal to the holding time of the individual run, or to several individual runs, whereby the operating time is the sum of the respective holding times. This advantageously enables coatings with diamond or silicon or silicon carbide to be produced with little effort and at low cost. According to an advantageous embodiment of the invention, the reactive gas atmosphere contains boron and / or phosphorus and / or nitrogen and / or oxygen.

[0103] According to a further advantageous embodiment of the invention, the reactive gas atmosphere has a pressure of less than 1000 mbar, preferably a pressure of 1 to 100 mbar, particularly preferably a pressure of 1 to 20 mbar.

[0104] According to a further advantageous embodiment of the invention, the reactive gas atmosphere contains 90 vol.% to 99.5 vol.% of hydrogen.

[0105] To produce a diamond layer, methane, for example, can be used as the carbon carrier in a concentration of 0.5 vol.% to 10 vol.%. To produce a silicon layer, the reactive gas atmosphere can contain a gaseous silicon carrier instead of the gaseous carbon carrier. The gaseous silicon carrier is preferably used in a concentration of 0.5 vol.% to 10 vol.%. To produce a silicon carbide layer, the reactive gas atmosphere can contain a gaseous carbon carrier and a gaseous silicon carrier. The gaseous carbon carrier and the gaseous silicon carrier are preferably used in a total concentration of 0.5 vol.% to 10 vol.%.

[0106] According to a further advantageous embodiment of the invention, the heating conductors are heated in step b) to a temperature in the range of 1800°C to 2500°C, preferably to a temperature in the range of 1900°C to 2300°C. According to a further advantageous embodiment of the invention, the heating conductors are heated in step b) for a holding time of 1 to 100 hours, preferably for a holding time of 3 to 50 hours.

[0107] It goes without saying that the features mentioned above for the contact device and / or the heating conductor holder can also be used analogously in the method. Accordingly, the above-mentioned method features can also be used analogously to specify the contact device and / or the heating conductor holder.

[0108] The invention is explained below using exemplary embodiments with the aid of the accompanying figures. The exemplary embodiments shown are therefore not to be understood as limiting.

[0109] Fig. 1 Schematic representation of an inventive

[0110] Heating element holder in cross section.

[0111] Fig. 2 Schematic representation of various inventive

[0112] Design of the heating conductor in top view.

[0113] Fig. 3 Schematic perspective view of the heating conductor holder according to the invention.

[0114] Fig. 4 Schematic perspective view of an arrangement of two heating conductor holders according to the invention in a device according to the invention for coating a substrate by means of CVD.

[0115] Fig. 5 Schematic perspective view of an arrangement of a heating conductor holder according to the invention in a device according to the invention for coating a substrate by means of CVD.

[0116] Fig. 6 Flowchart for the process of an inventive

[0117] procedure.

[0118] Fig. 1 shows a schematic representation of a heating conductor holder according to the invention in cross-section. A first electrode 1 comprises a first support structure 2 and a first contact bar 3. The first support structure 2 is made of a dispersion-strengthened copper material or of pure copper. A first support structure 2 made of the dispersion-strengthened copper material remains extremely dimensionally stable even at high temperatures. A first support structure 2 made of pure copper is cooled, for example, by cooling fins and / or with the aid of a cooling fluid. According to the invention, the first contact bar 3 consists of 1 wt.% to 100 wt.% metal which forms metastable carbides. For example, the first contact bar 3 consists of austenitic chromium-nickel steel with 70 wt.% iron, 10 wt.% nickel, and 18 wt.% chromium.Since iron and nickel are among the metals that form metastable carbides, the first contact rail 3 in the example mentioned consists of approximately 80 wt.% of metal that forms metastable carbides.

[0119] A spring 4 is attached at one end to the first support structure 2 and at its other end to a heating conductor 5. The heating conductor 5 is held mechanically tensioned by a spring force exerted by the spring 4. Furthermore, the spring force has a component running perpendicular to the direction of the longitudinal extension of the heating conductor 5, which is directed in the direction of the first electrode 1. Therefore, due to the effect of the spring force, the heating conductor 5 experiences a contact force directed towards the first electrode 1, so that the heating conductor 5 touches the first electrode 1 in a contact area formed by the first contact rail 3, forming a sliding contact 3a. In the example shown, the direction of the spring force forms an angle of 20° with the direction of the longitudinal extension of the heating conductor 5.

[0120] The side of the first contact rail 3 facing the heating conductor 5 runs obliquely with respect to the direction of the longitudinal extension of the heating conductor 5. The side facing the heating conductor 5 forms an angle of, for example, 30° with the direction of the longitudinal extension of the heating conductor 5. Therefore, the heating conductor 5 only comes into contact with the tip of the first contact rail 3 facing the heating conductor 5 in the sectional view shown.

[0121] The electrical resistance of the spring 4 is preferably comparatively high. Therefore, the current flows through the first support structure 2 and is conducted into the heating conductor 5 at the tip of the first contact rail 3 facing the heating conductor 5 in the sectional view shown, or at the sliding contact 3a.

[0122] The spring 4 can be attached to the first support structure 2 directly (i.e., electrically conductive) or electrically insulated. The spring 4 can be attached to the heating conductor 5 directly (i.e., electrically conductive) or electrically insulated.

[0123] Deviating from the example shown, the spring 4 can also be formed integrally with the heating conductor 5.

[0124] In the example shown, the heating conductor 5 is designed as a 200 μm thick tungsten carbide wire with a substantially circular cross-section. Such a thin heating conductor 5 essentially only comes into contact with the contact area at one point. Therefore, the term "contact area" can also be used as a contact point instead. The first electrode 1 forms a contact device according to the invention with the heating conductor 5. Likewise, a second electrode 6 can form a contact device according to the invention with the heating conductor 5.

[0125] The second electrode 6 comprises a second support structure 7 and a second contact rail 8. The second support structure 7 is made of a dispersion-strengthened copper material. Therefore, the second support structure 7 remains extremely dimensionally stable even at high temperatures. According to the invention, the second contact rail 8 consists of 1 wt.% to 100 wt.% metal that forms metastable carbides. For example, the second contact rail 8 consists of austenitic chromium-nickel steel with 70 wt.% iron, 10 wt.% nickel, and 18 wt.% chromium. Since iron and nickel are among the metals that form metastable carbides, the second contact rail 8 in the example mentioned consists of approximately 80 wt.% metal that forms metastable carbides.

[0126] In the example shown, the heating conductor 5 is mechanically attached directly to the second support structure 8. Thus, due to the effect of the spring force, the heating conductor 5 experiences a contact force directed toward the second electrode 6, so that the heating conductor 5 touches the second electrode 6 in a contact area formed by the second contact rail 8, forming a sliding contact 8a.

[0127] The side of the second contact rail 8 facing the heating conductor 5 runs obliquely with respect to the direction of the longitudinal extension of the heating conductor 5. The side facing the heating conductor 5 forms an angle of, for example, 30° with the direction of the longitudinal extension of the heating conductor 5. Therefore, the heating conductor 5 only comes into contact with the tip of the second contact rail 8 facing the heating conductor 5 in the sectional view shown. Here, too, given that the heating conductor 5 is designed as a thin wire, the term "contact area" can be used instead of "contact point". Deviating from the example shown, the heating conductor 5 can also be attached to the second support structure 8 with the interposition of an additional spring. In this case, the directions of the forces acting on the heating conductor 5 remain the same.

[0128] Deviating from the previous description of the figures, the second electrode 6 may, for example, not form a contact device according to the invention with the heating conductor 5. The second electrode 6, including the second contact rail 8, may, for example, be made of pure copper.

[0129] Fig. 2 shows a schematic representation of various designs of the heating conductor in plan view. The plan view in Fig. 2 corresponds to the sectional view in Fig. 1. To avoid repetition, reference is made to the explanations for Fig. 1.

[0130] The left half of Fig. 2 shows a spring 4 to which exactly one heating conductor 5, designed as a wire, is attached. The right half of Fig. 2 shows a spring 4 to which another wire is attached. The additional wire has a bend 5a into which the spring 4 is hooked. Starting at the bend 5a, the additional wire forms two parallel heating conductors 5.

[0131] The design shown in the right half of Fig. 2 requires a smaller number of springs and is therefore advantageously particularly material-efficient. Furthermore, the bend 5a can be hooked into the spring 4 particularly easily in this design.

[0132] Fig. 3 shows a schematic perspective view of the heating conductor holder according to the invention. The perspective view in Fig. 3 corresponds to the sectional view in Fig. 1. To avoid repetition, reference is therefore made to the explanations for Fig. 1. The heating conductor holder has nine heating conductors 5 running parallel to one another.

[0133] Each of the heating conductors 5 is held individually tensioned by a spring 4 attached to its upper end.

[0134] The first electrode 1 and the second electrode 6 can additionally be firmly connected to one another via supports and with the interposition of electrical insulation means. The supports and the electrical insulation means are not shown in Fig. 3. In this case, the first electrode 1, the second electrode 6, the supports, and the electrical insulation means, together with the attached springs 4 and heating conductors 5, form a structural unit referred to as a module. The module is expediently designed so that it can be arranged in a conventional housing of a CVD coating device.

[0135] The first 1 and the second electrode 6 are connected to a power source (not shown) to heat the heating conductor 5.

[0136] The heating conductor holder may have a cooling device for cooling the first and / or second electrode.

[0137] Fig. 4 schematically shows an arrangement of two heating conductor holders according to the invention in a device according to the invention for coating a substrate 9 by means of CVD. The substrate 9 is surrounded by the two heating conductor holders in such a way that it can be coated on both sides. The substrate 9 and the two heating conductor holders are each arranged vertically, for example. The other apparatus features of the device are not shown. The arrangement is accommodated in a gas-tight housing. A pump is provided for evacuating the housing. Reaction gas can optionally be fed into the housing through a nozzle. Fig. 5 schematically shows a horizontal arrangement of a heating conductor holder according to the invention in a device according to the invention for coating a substrate 9 by means of CVD. The heating conductors 2 extend within a plane running transversely to the direction of gravity.In the example shown, the substrate 9 is arranged below the heating element holder in the direction of gravity.

[0138] Fig. 6 shows a flowchart of an exemplary method according to the invention for coating one or more substrates with a diamond layer using CVD. The following steps are preferably performed sequentially.

[0139] In step S01 the housing is evacuated.

[0140] In step S02, a reactive gas atmosphere containing hydrogen and a gaseous carbon carrier is generated in the housing. The reactive gas atmosphere has a pressure of, for example, 10 mbar. The reactive gas atmosphere contains, for example, 95 vol.% hydrogen. Methane, for example, is used as the carbon carrier to produce the diamond layer at a concentration of 5 vol.%.

[0141] In step S03, the heating conductors are heated from the ambient temperature to a temperature of, for example, 2100°C for a holding time of, for example, 150 hours.

[0142] In step S04, the heating elements are cooled to ambient temperature.

[0143] In step S05 the housing is evacuated.

[0144] In step S06, the housing is ventilated. In step S07, the diamond-coated substrate(s) are removed.

[0145] In the method according to the invention, a high level of electrical conductivity can advantageously be permanently provided at the contact device(s) according to the invention or at the heating conductor holder(s) according to the invention. This results in a homogeneous current distribution among the individual heating conductors. This advantageously allows the gas surrounding the heating conductors to be homogeneously excited and the substrate to be coated homogeneously.

[0146] Advantageously, the fusion of the heating conductor and the contact point or contact area can be prevented. This preserves the flexibility of the heating conductor relative to the contact point or contact area. The heating conductors therefore have a long service life. This advantageously means that the time-consuming and costly replacement of the heating conductors in the heating conductor holder is rarely necessary.

[0147] The inventive design of the contact device(s) or the heating conductor holder(s) allows for a very long operating time in the range of 100 to 500 hours, particularly in the range of 200 to 500 hours. The operating time can refer to a single individual run, where the operating time is equal to the holding time of the individual run, or to several individual runs, where the operating time is the sum of the respective holding times. This advantageously allows coatings with diamond, silicon, or silicon carbide to be produced with little effort and low cost.

[0148] It is clear to the person skilled in the art that the above-mentioned embodiments of the contact device, the heating conductor holder, the device and the method can be combined with each other as desired and do not represent any restriction, in particular not in their design and combination.

[0149] List of reference symbols

[0150] 1 first electrode

[0151] 2 first supporting structure

[0152] 3 first contact rail

[0153] 3a Sliding contact on first contact rail

[0154] 4 spring

[0155] 5 heating conductors

[0156] 5a Bending of the heating element

[0157] 6 second electrode

[0158] 7 second supporting structure

[0159] 8 second contact rail

[0160] 8a Sliding contact on second contact rail

[0161] 9 Substrat

Claims

Claims 1. Contact device for a device for coating a substrate (9) by means of CVD, comprising a heating conductor (5) and an electrode (1, 6), wherein the electrode (1, 6) has a contact region, wherein the heating conductor (5) is held mechanically tensioned by the action of a spring force and / or weight and experiences a contact force directed towards the electrode (1, 6) due to the action of the spring force and / or weight, so that the heating conductor (5) touches the electrode (1, 6) in the contact region to form a sliding contact (3a, 8a), wherein the contact region consists of a first material and / or has the first material as a coating on a second material, and wherein the first material consists of 1 wt.% to 100 wt.% metal which forms metastable carbides.

2. Contact device according to claim 1, wherein the first material consists of at least 5 wt.% to 100 wt.%, preferably 10 wt.% to 100 wt.%, particularly preferably 60 wt.% to 100 wt.%, of metal which forms metastable carbides, and / or wherein the first material consists of 1 wt.% to 100 wt.% of one metal or of several metals selected from iron, nickel, cobalt and rhodium, and / or wherein the first material consists of at least 5 wt.% to 100 wt.%, preferably 10 wt.% to 100 wt.%, particularly preferably 60 % to 100 % by weight, of one or more metals selected from iron, nickel, cobalt and rhodium.

3. Contact device according to claim 1 or 2, wherein the first material consists of steel, preferably austenitic steel, particularly preferably austenitic chromium-nickel steel.

4. Contact device according to one of the preceding claims, wherein the second material contains less than 1 wt.%, preferably less than 1 per mille, of metal forming metastable carbides.

5. Contact device according to one of the preceding claims, wherein the second material is made of copper, preferably of pure copper and / or of a dispersion-strengthened copper material.

6. Contact device according to one of the preceding claims, wherein the heating conductor (5) is made of a carbide-forming metal, preferably of W, Ta, Mo, Hf, Nb or an alloy thereof, and / or of a carbide formed from a carbide-forming metal.

7. Contact device according to one of the preceding claims, wherein the heating conductor (5) consists of a mixture or combination of a carbide-forming metal and / or a carbide formed therefrom with another carbide-forming metal and / or a carbide formed therefrom, and / or wherein the heating conductor (5) has a coating of a carbide-forming metal and / or a carbide formed therefrom on another carbide-forming metal and / or a carbide formed therefrom, wherein the heating conductor (5) preferably has a coating of tantalum and / or tantalum carbide on tungsten and / or tungsten carbide.

8. Contact device according to one of the preceding claims, wherein the heating conductor (5) has a circular or polygonal, in particular rectangular, cross-section.

9. Contact device according to one of the preceding claims, wherein the heating conductor (5) has a greatest extension in cross section and / or a diameter of less than 1 cm, preferably from 5 to 500 pm, particularly preferably from 100 to 300 pm.

10. Heating conductor holder for a device for coating a substrate (9) by means of CVD, comprising at least one contact device according to one of claims 1 to 9.

11. Heating conductor holder according to claim 10, wherein the heating conductor holder comprises a first (1) and a second electrode (6) as well as a plurality of heating conductors (5) each extending between the first (1) and the second electrode (6), wherein the first (1) and / or the second electrode (6) has a plurality of contact areas, wherein the heating conductors (5) are each held mechanically tensioned by the action of a spring force and / or weight force and each experience a contact force directed towards the first electrode (1) and / or a contact force directed towards the second electrode (6) due to the action of the spring force and / or weight force, so that each individual heating conductor (5) touches the first (1) and / or the second electrode (6) in a contact area assigned to this heating conductor (5), forming a sliding contact (3a, 8a).wherein the contact areas each consist of the first material and / or have the first material as a coating on the second material, and that the first material consists of 1 wt.% to 100 wt.% metal which forms metastable carbides., 12. Heating conductor holder according to claim 10 or 11, wherein the heating conductor holder is designed as a module.

13. Heating conductor holder according to one of claims 10 to 12, wherein a cooling device is provided for cooling the first (1) and / or second electrode (6).

14. Heating conductor holder according to one of claims 10 to 13, wherein the heating conductor holder extends in a plane or has a bend and / or a cylindrical shape and / or a conical shape.

15. Device for coating a substrate (9) by means of CVD, in particular for coating with diamond or silicon or silicon carbide, wherein the device comprises a housing in which at least one contact device according to one of claims 1 to 9 and / or at least one heating conductor holder according to one of claims 10 to 14 are provided.

16. Device according to claim 15, wherein at least one heating conductor holder is arranged in the device such that the direction of the longitudinal extent of the heating conductors (5) runs along the direction of gravity, and / or wherein at least one heating conductor holder is arranged in the device such that the direction of the longitudinal extent of the heating conductors (5) runs transversely to the direction of gravity, and / or wherein at least one heating conductor holder is arranged in the device such that the direction of the longitudinal extent of the heating conductors (5) forms an angle between 0° and 90° with the direction of gravity.

17. Method for coating a substrate (9) by means of CVD, in particular for coating with diamond or silicon or silicon carbide, wherein using a device according to claim 15 or 16, the following steps are carried out: a) generating a reactive gas atmosphere containing hydrogen and a gaseous carbon and / or silicon carrier in the housing, b) heating the heating conductors (5) from ambient temperature to a temperature in the range from 1500°C to 2600°C for a holding time of 0.1 to 500 hours by applying an electrical power to the heating conductors (5), c) removing the electrical power.

18. The method according to claim 17, wherein the reactive gas atmosphere contains boron and / or phosphorus and / or nitrogen and / or oxygen, and / or wherein the reactive gas atmosphere has a pressure of less than 1000 mbar, preferably a pressure of 1 to 100 mbar, particularly preferably a pressure of 1 to 20 mbar, and / or wherein the reactive gas atmosphere contains 90 to 99.5 vol.% of hydrogen.

19. The method according to claim 17 or 18, wherein the heating conductors (5) are heated in step b) to a temperature in the range of 1800°C to 2500°C, preferably to a temperature in the range of 1900°C to 2300°C, and / or wherein the heating conductors (5) are heated in step b) for a holding time of 1 to 100 hours, preferably for a holding time of 3 to 50 hours.

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