CN112501582B

CN112501582B - Hot wire chemical vapor deposition device and metal support

Info

Publication number: CN112501582B
Application number: CN202011360023.5A
Authority: CN
Inventors: 满卫东; 朱长征; 龚闯; 吴剑波; 蒋剑宏
Original assignee: Shanghai Zhengshi Technology Co Ltd
Current assignee: Shanghai Zhengshi Technology Co Ltd
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2021-06-11
Anticipated expiration: 2040-11-27
Also published as: WO2022111182A1; CN112501582A

Abstract

The invention provides a hot wire chemical vapor deposition device and a metal bracket thereof, wherein the metal bracket is connected with a power supply to conduct current to a hot wire supported on the metal bracket, the top surface of the metal bracket is provided with a plurality of grooves, the upper surfaces of the grooves are provided with conductive diamond film layers, each hot wire is independently placed on the diamond film layer in each groove, and the hot wire in a working state converts diamond contacted with the hot wire into graphite so as to reduce the friction force between the hot wire and the diamond film layer. According to the invention, the friction between the hot wire and the metal bracket is reduced through the formed graphite, so that the pulling force required for tightening the hot wire can be reduced, and the service life of the hot wire is prolonged.

Description

Hot wire chemical vapor deposition device and metal support

Technical Field

The invention relates to the field of chemical vapor deposition, in particular to a hot wire chemical vapor deposition device and a metal support therein.

Background

The diamond has excellent force, heat, light, electricity and acoustic properties and has wide application prospect. The hot metal wire chemical vapor deposition (hot wire CVD) method adopts hydrogen and carbon-containing gas or liquid as raw materials, prepares the diamond film by pyrolyzing the raw material gas at high temperature through the hot metal wire, has the advantages of low cost, high growth speed, easy enlargement of the device and the like, and is a commonly adopted method for preparing the diamond film at present. The diamond film is prepared by a hot wire CVD method, a plurality of metal wires are required to be assembled on a pair of electrodes which are communicated with direct current, when the direct current flows through the metal wires, the metal wires generate heat because of self resistance of the metal wires, and the temperature of the metal wires is controlled to reach the required temperature by controlling the current, so the metal wires usually adopt metal with high melting point (such as W, Ta and the like), and the diameter of the metal wires is generally not more than 1.5 mm. The hot wire stretches due to high temperature creep when heated from room temperature to operating temperature. In addition, the hot wire is carbonized by reaction with the raw material carbon at a high temperature, and the hot wire is elongated by carburization during the carbonization. The length of the hot wire will generally be extended by about 5-20% depending on the length of time required to grow the CVD diamond. Because the two ends of the hot wire are fixed, the middle section of the hot wire can fall down due to the elongation of the hot wire, and the distance between the hot wire and the substrate material is changed, so that the surface temperature of the substrate material is increased to deviate from the optimal growth condition of the diamond film, and the quality of the deposited diamond film is influenced.

Aiming at the phenomenon that the length of the hot wire is increased after the hot wire creeps, the method which is generally adopted at present mainly maintains the hot wire in a straightening state by applying tension on the hot wire. The tension is mainly generated in two ways, one is that one end of the metal wire is pulled by a high-temperature spring or a shrapnel, and the hot metal wire is always in a straightened state by the tension generated by the deformation of the spring, such as U.S. Pat. nos. 4953499, 4958592, 5833753 and 4970986, and chinese patent ZL 98205844.6. Because the tension provided by the spring is variable force, the spring is shortened along with the extension of the hot wire in the working process and the provided tension is reduced, according to Hooke's law. In addition, when the spring works in a high-temperature environment (generally, the environment temperature is hundreds of degrees centigrade), the spring is annealed, the coefficient of stiffness is reduced, on one hand, the elasticity is reduced, and on the other hand, the service life of the spring is influenced. Thus, high temperature springs have significant disadvantages. In addition, after the hot wire is carbonized, the tensile strength is greatly reduced, the tension applied to the hot wire is limited, the hot wire can be broken when the tension is applied too much, but if the tension is applied too little, the elongation caused by high-temperature creep cannot be compensated, and the hot wire cannot be ensured to be always in a straight state, so that the uniformity of the deposited diamond film is influenced, therefore, when the high-temperature spring is used, the elasticity of the spring must be carefully adjusted every time, which is troublesome.

The other is to hang a heavy object by one end of the hot metal wire and straighten the hot metal wire by the gravity action of the heavy object. To facilitate the drawing of the hot wire, patent CN201102987Y applies a pulling force to the wire by means of a pulley set to keep the hot wire straight. However, the patent has the defects that the structure of the pulley block is complex, the pulley block is placed in a high-temperature environment, and the rotation of the pulley is not lubricated by a traditional liquid lubrication system, so that the stability and the consistency of the rotation of the pulley are difficult to maintain at high temperature. It can be said that, the current hot wire suspension system has a complex structure.

However, in any of the above methods, in order to maintain the straightened state of the hot wire, it is necessary to support and fix the position of the hot wire by a pair of metal electrode holders. In the process of depositing CVD diamond by hot wire CVD, the length of the hot wire at high temperature can be lengthened due to carbide generated by high-temperature creep and combination with carbon in reaction raw materials, the hot wire can slide on the surface of the metal electrode support under the action of tension at one end of the hot wire, sliding friction can be generated, and the hot wire can be gradually lengthened at high temperature, so that the diameter can be reduced. Meanwhile, the thickness of the carbide generated on the surface is increased along with the prolonging of time, so that the sliding friction force generated by the sliding of the hot wire on the surface of the metal electrode support is a constantly changing process. To maintain sufficient tension to ensure that the filament is always in a "tight" condition, it is often necessary to apply a greater tension to the filament. The greater tension will make the filament more "easily" elongated, making the elongated filament smaller in diameter and more prone to breakage, terminating the CVD process of depositing diamond. If the hot wire can slide "easily" over the surface of the electrode holder, the tension exerted on the wire can be reduced, which is important to extend the life of the hot wire.

In view of the above, it is desirable to provide a hot wire chemical vapor deposition apparatus and a metal support thereof, which can reduce friction between a hot wire and the support, reduce tension required for tightening the hot wire, and thus prolong the service life of the hot wire.

Disclosure of Invention

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

As described above, in order to solve the problems of the prior art that the diameter of the hot wire is reduced and the service life of the hot wire is not long due to the fact that a large tensile force for tightening the hot wire is applied to keep the hot wire straight all the time, the present invention provides a metal bracket, wherein the metal bracket is connected with a power supply to conduct current to the hot wire supported on the metal bracket, the top surface of the metal bracket is provided with a plurality of grooves, the upper surfaces of the grooves are provided with conductive diamond films, each hot wire is separately placed on the diamond film in each groove, and the hot wire in an operating state converts diamond in contact with the hot wire into graphite so as to reduce the friction force between the hot wire and the diamond films.

In an embodiment of the metal support, optionally, the diamond film layer is a nano-diamond film layer with a grain size of less than 100 nm. Because the diamond film layer is a diamond film with the grain size of nanometer level, the surface of the diamond film layer has high smoothness and small friction coefficient, and the sliding friction force generated when the hot wire slides on the surface of the nanometer diamond film layer can be further reduced. Therefore, the pulling force required to be applied to the hot wire can be reduced, and the service life of the hot wire is prolonged.

In an embodiment of the metal support, optionally, the resistivity of the diamond film layer is 4.3 × 10^-4Ω.cm-7.8*10^-2Omega cm. It will be appreciated that the metal support described above is required to be electrically conductive and supportive. In order to ensure good conductivity, the power supply current can smoothly flow through the hot wire, the resistance of the diamond film layer needs to be reduced, the metal support with low resistivity can reduce the self-heating problem of the metal support, and the self-temperature of the metal support is reduced.

In an embodiment of the metal stent, optionally, the diamond film layer is a boron-doped diamond film layer, and a hole carrier concentration of the boron-doped diamond film layer is 8.7 × 10¹⁹-4.6*10²¹cm^-3In the meantime. In the aboveIn an embodiment, the reduction of the resistance of the diamond film layer is achieved by doping the diamond film layer with boron. By controlling the hole carrier concentration of the diamond film after boron doping to be 8.7 x 10¹⁹-4.6*10²¹cm^-3The resistivity of the diamond film layer is ensured.

In an embodiment of the metal support, optionally, the thickness of the diamond film layer is 3 to 15 micrometers. The reason why the thickness of the diamond film layer is set to be 3-15 micrometers is that the thickness of the diamond film layer cannot be too thin, and if the thickness of the diamond film layer is too thin, enough diamond film layer cannot be converted into graphite under the working state of the hot wire. On the other hand, the thickness of the diamond film layer cannot be too thick, and because the diamond film layer is formed on the metal support, if the thickness is too thick, the adhesive force between the diamond film layer and the metal cannot be ensured, and the diamond film layer is easy to fall off. Therefore, it is necessary to set the thickness of the diamond film layer to 3 to 15 μm.

In an embodiment of the metal bracket, optionally, the working temperature of the hot wire is 1800-.

In an embodiment of the metal bracket, optionally, the metal bracket includes a metal tungsten bracket and a metal molybdenum bracket. Since the metal support is required to withstand a high temperature in the hot-wire chemical vapor deposition, it is required to ensure thermal stability and chemical stability of other materials except for reaction raw materials in the reaction chamber in order to ensure purity of a product of the hot-wire chemical vapor deposition, and thus, tungsten metal and molybdenum metal are preferable materials for the metal support.

In another aspect of the present invention, there is provided a hot wire chemical vapor deposition apparatus, including a plurality of hot wires horizontally disposed, and two ends of each of the plurality of hot wires are respectively supported on a pair of brackets, wherein at least one of the brackets is a metal bracket as described in any one of the above embodiments, and a weight is suspended at one end of each of the hot wires supported on the metal bracket, so as to straighten the hot wire by using the gravity of the weight.

In an embodiment of the hot wire chemical vapor deposition apparatus, each of the pair of holders is a metal holder as described in any one of the above embodiments, and both ends of the hot wire are respectively suspended by a weight and supported by the metal holder.

In an embodiment of the hot wire chemical vapor deposition apparatus, optionally, the other of the pair of supports is a fixed metal support, and the other end of the hot wire is fixed to the fixed metal support by a clamp.

According to the hot wire chemical vapor deposition device and the metal support thereof provided by the invention, the friction between the hot wire and the metal support is reduced through the formed graphite, the pulling force required for tightening the hot wire can be reduced, and the service life of the hot wire is prolonged.

Drawings

The above features and advantages of the present disclosure will be better understood upon reading the detailed description of embodiments of the disclosure in conjunction with the following drawings. In the drawings, components are not necessarily drawn to scale, and components having similar relative characteristics or features may have the same or similar reference numerals.

Fig. 1 shows a top view of a metal stent provided by the present invention.

Fig. 2 shows a schematic sectional view in the direction of a-a' of the groove of the metal bracket provided by the present invention.

Fig. 3 shows a schematic cross-sectional view in the direction of B-B' of the groove of the metal bracket provided by the present invention.

FIG. 4 shows a laser Raman spectrum of the surface of the diamond film layer formed on the grooves of the metal support provided by the invention before hot wire chemical vapor deposition.

Fig. 5 shows a laser raman spectrum of the surface of the diamond film layer formed on the grooves of the metal support provided by the present invention after hot wire chemical vapor deposition.

Reference numerals

110 metal support

111 groove

112 diamond film layer

120 fixed support

200 power supply

300 hot wire

400 support column

410 insulator

420 weight

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. It is noted that the aspects described below in connection with the figures and the specific embodiments are only exemplary and should not be construed as imposing any limitation on the scope of the present invention.

The following description is presented to enable any person skilled in the art to make and use the invention and is incorporated in the context of a particular application. Various modifications, as well as various uses in different applications will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to a wide range of embodiments. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the practice of the invention may not necessarily be limited to these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.

The reader's attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All the features disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Note that where used, the designations left, right, front, back, top, bottom, positive, negative, clockwise, and counterclockwise are used for convenience only and do not imply any particular fixed orientation. In fact, they are used to reflect the relative position and/or orientation between the various parts of the object.

As described above, in order to solve the problems that the diameter of the hot wire is reduced and the service life is not long due to the fact that a large tensile force for tightening the hot wire is applied to keep the hot wire in a straight state all the time in the prior art, the invention provides a hot wire chemical vapor deposition device and a metal bracket thereof.

Please refer to fig. 1-3 for understanding the hot-wire chemical vapor deposition apparatus and the metal support thereof provided in the present invention. As shown in fig. 1, a pair of brackets, including the metal bracket 110 and the fixing bracket 120 provided in the present invention, are connected to a power source 200 to conduct current to a hot wire 300 supported on the metal bracket 110 and the fixing bracket 120. Referring to fig. 2, fig. 2 is a cross-sectional view of the metal bracket 100 along a direction a-a'. The top surface of the metal holder 110 has a plurality of grooves 111, the upper surfaces of the grooves are formed with conductive diamond films 112, each hot wire 300 is individually placed on the diamond film 112 in each groove 111, and the hot wire 300 in an operating state converts diamond in contact with the hot wire into graphite, so as to reduce friction between the hot wire 300 and the diamond film 112.

In the above-described embodiment, the overall shape of the metal bracket 110 may be a conventional or future shape, such as a long cube or other cylindrical shape. The overall shape of the metal bracket provided by the invention can be adjusted according to actual needs, and the protection scope of the invention is not limited properly.

The upper surface of the metal bracket 110 is required to be provided with a plurality of grooves 111, and each groove is provided with a hot wire 300. It can be understood that the number of the grooves 111 can be set according to actual needs, the grooves are parallel to each other, and the grooves are arranged at equal distances from one another, so as to ensure the uniformity of the arrangement of the hot wire. In addition, it should be noted that if the actual number of the grooves is larger than the number of the hot wires to be arranged, the hot wires are only required to be uniformly arranged in a plurality of the grooves.

In the above embodiment, optionally, the diamond film layer is a nano-diamond film layer with a grain size of less than 100 nm. Because the diamond film layer is a diamond film with the grain size of nanometer level, the surface of the diamond film layer has high smoothness and small friction coefficient, and the sliding friction force generated when the hot wire slides on the surface of the nanometer diamond film layer can be further reduced. Therefore, the pulling force required to be applied to the hot wire can be reduced, and the service life of the hot wire is prolonged.

In the above embodiment, optionally, the resistivity of the diamond film layer is 4.3 × 10^-4Ω.cm-7.8*10^-2Omega cm. It will be appreciated that the metal support described above is required to be electrically conductive and supportive. In order to ensure good conductivity, the power supply current can smoothly flow through the hot wire, the resistance of the diamond film layer needs to be reduced, the metal support with low resistivity can reduce the self-heating problem of the metal support, and the self-temperature of the metal support is reduced.

Further, the diamond film layer is a boron-doped diamond film layer, and the hole carrier concentration of the boron-doped diamond film layer is 8.7 x 10¹⁹-4.6*10²¹cm^-3In the meantime. In the above embodiment, the reduction of the resistance of the diamond film layer is achieved by doping boron in the diamond film layer. In the present invention, the hole carrier concentration of the boron-doped diamond film is controlled to be 8.7 x 10¹⁹-4.6*10²¹cm^-3The resistivity of the diamond film layer is ensured.

The above-mentioned nano-crystalline boron-doped diamond film formed on the upper surface of the groove is prepared by a microwave plasma CVD method, and those skilled in the art can realize the preparation of the above-mentioned nano-crystalline boron-doped diamond film according to the existing or future techniques, for example, details on the preparation of a highly boron-doped diamond film (Si/BDD) and the study of electrochemical properties (chenpeng, man-weidong, 2011) disclose a method for preparing a boron-doped diamond film capable of preparing the above-mentioned nano-crystalline.

In the above embodiment, the working temperature of the hot wire is 1800-. Further, the metal bracket comprises a metal tungsten bracket and a metal molybdenum bracket. Since the metal support is required to withstand a high temperature in the hot-wire chemical vapor deposition, it is required to ensure thermal stability and chemical stability of other materials except for reaction raw materials in the reaction chamber in order to ensure purity of a product of the hot-wire chemical vapor deposition, and thus, tungsten metal and molybdenum metal are preferable materials for the metal support.

According to the metal support, when the temperature of the diamond film exceeds 900 ℃, the surface of the diamond film can be graphitized, and a thin graphite layer can be formed on the surface of the graphitized boron-doped diamond film, so that the frictional resistance between frictional surfaces can be further reduced. The graphitized surface can continuously generate graphite between the contact surfaces of the diamond film and the hot wire, and the lubricating effect is constantly kept. The graphite added manually is elongated, so that the graphite added between the friction surfaces is gradually reduced along with the movement of the surfaces of the hot wires, and finally the graphite is possibly disappeared, so that the lubricating effect is lost.

According to the preferred embodiment of the invention, the diamond film is doped with boron, has conductivity and does not influence the conductive function of the metal bracket. Meanwhile, the formed graphite is also conductive, and the electric conduction state between the electrode bracket and the hot metal wire is not influenced.

According to another preferred embodiment, when the nano-crystalline diamond film is adopted, the surface smoothness is high, the friction coefficient is small, and the hot wire can slide on the surface conveniently, so that the pulling force applied to the hot wire can be reduced, and the service life of the hot wire can be prolonged.

Another aspect of the present invention provides a hot-filament chemical vapor deposition apparatus, as will be understood with reference to fig. 1 and 3. The hot wire chemical vapor deposition device comprises a plurality of hot wires 300 which are horizontally arranged, two ends of the plurality of hot wires are respectively supported on a pair of brackets (comprising a metal bracket 110 and a fixed bracket 120 in fig. 1), at least one bracket of the pair of brackets is the metal bracket 110, and a weight 420 is hung at one end of the hot wire 300 supported on the metal bracket 110, so that the hot wire is straightened by the gravity of the weight 420.

In an embodiment of the hot wire chemical vapor deposition apparatus, as shown in fig. 1, optionally, the other of the pair of supports is a fixed metal support 120, and the other end of the hot wire is fixed to the fixed metal support 120 by a clamp. It is to be understood that the above-mentioned fixed metal bracket means that the end of the hot wire supported on the fixed metal bracket does not hang a weight, but is fixed to the fixed metal bracket. The fixing manner of the above-mentioned clamp may be one of the manners. Other materials can also be fixed in the holes and the like arranged in the fixed bracket.

In the embodiment shown in fig. 1 to 3, a pair of

supports

110 and 120 of the filament cvd apparatus are made of mo metal and are respectively connected to two poles of an external dc power supply 200, and the metal support 100 and the support 200 are electrically insulated from the support column 400 by an insulator 410. The tantalum metal wire, namely the hot wire 300, of the fixed support 120 is fixed through a clamp, the diameter of the metal wire is 0.5 mm, a groove 111 is formed in the metal support 110, the metal wire, namely the hot wire 300, is placed in the groove 111, a layer of boron-doped diamond film 112 with nano crystal grains is prepared on the surface of the groove, and the hot wire at the end of the metal support 110 is straightened in a tension mode of hanging a heavy object 420.

The following provides a method for manufacturing the metal holder 110 and a working process of a hot-wire CVD apparatus having the metal holder mounted thereon.

The surface of the metal support 110, especially the surface of the groove 111, is prepared into a layer of boron-doped CVD diamond film with a thickness of 6.5 microns by a microwave CVD method, and the preparation process comprises the following steps:

TABLE 1 Process for preparing boron-doped CVD diamond film with nanocrystalline particles

Note: sccm is standard cubic centimeter per minute; b is₂H₆Is pure B₂H₆Diluting in H according to 1 ‰ volume ratio₂Of the flow rate of (c).

The resistivity of the resulting boron-doped CVD diamond film 112 was 2.6X 10^-3Omega cm. The grain size of the prepared CVD diamond film is less than 100nm, and belongs to the size of nanometer grains. FIG. 4 is a laser Raman spectrum of the surface of the CVD diamond film, and it can be seen that the characteristic peak position of the diamond is from 1332cm^-1Moved to 1326.6cm^-1Indicating that boron is incorporated into the lattice of diamond.

After the metal support 110 is prepared, the metal support 110 is used in the process of preparing a diamond film by hot wire chemical vapor deposition. A hot wire array composed of 11 tantalum wires with the diameter of 0.8 mm can be selected, the hot wires are placed in the grooves 111 of the metal electrodes 110 as shown in figures 1 and 3, the center distance between the hot wires is 10 mm, the length of the hot wire between the two electrodes is 120 mm, the substrate material for depositing the CVD diamond film is a metal molybdenum sheet with the diameter of 100 mm, the thickness is 4 mm, the distance between the hot wire array and the molybdenum substrate material is 8 mm, the temperature of the hot wire is 2300 ℃, and the reaction gas is 96% (Vol.) H₂And 4% (Vol.) CH₄And growing for 200 hours to prepare a CVD diamond film with the diameter of 100 mm and the thickness of 1.5mm, wherein the hot wire array is in a straight state in the whole growing process.

After the CVD diamond film deposition using the metal support 110 is completed, raman spectroscopy is performed on the surface of the CVD diamond film doped with boron nanocrystals on the surface of the metal support 110, and the result is shown in fig. 5. It can be seen that the boron-doped nano-diamond film surface forms non-diamond carbon components (1350 cm) through the high-temperature long-time contact of the hot wire^-1Characteristic peak in the vicinity) of the graphite component (1580 cm)^-1A characteristic peak in the vicinity). Graphite components are formed between the surface of the boron-doped nano diamond film and the hot metal wires, so that the sliding of the hot metal wires on the surface of the electrode frame can be improved, and the hot wire array can be kept in a straight state all the time.

The hot wire chemical vapor deposition apparatus and the metal support thereof provided by the present invention have been described so far. According to the hot wire chemical vapor deposition device and the metal support thereof provided by the invention, the friction between the hot wire and the metal support is reduced through the formed graphite, the pulling force required for tightening the hot wire can be reduced, and the service life of the hot wire is prolonged.

It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Furthermore, in the foregoing detailed description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Reference in the specification to one embodiment or an embodiment is intended to include within at least one embodiment of a circuit or method a particular feature, structure, or characteristic described in connection with the embodiment. The appearances of the phrase one embodiment in various places in the specification are not necessarily all referring to the same embodiment.

Claims

1. A metal holder connected to a power source to conduct an electric current to a heater supported on the metal holder, wherein the metal holder has a plurality of grooves on a top surface thereof, conductive diamond films are formed on upper surfaces of the grooves, each heater is separately placed on the diamond films in each groove, and the heater in an operating state converts diamond in contact therewith into graphite to reduce friction between the heater and the diamond films.

2. The metal stent of claim 1, wherein the diamond film layer is a nanodiamond film layer having a grain size of less than 100 nanometers.

3. The metal stent of claim 1, wherein the diamond film layer has a resistivity of 4.3 x 10^-4Ω.cm-7.8*10^-2Ω.cm。

4. The metal stent of claim 3, wherein the diamond film layer is a boron-doped diamond film layer having a hole carrier concentration of 8.7 x 10¹⁹-4.6*10²¹cm^-3In the meantime.

5. The metal stent of claim 1, wherein the diamond film layer has a thickness of 3 to 15 microns.

6. The metal stent of claim 1, wherein the working temperature of the hot wire is 1800-.

7. The metal stent of claim 1, wherein the metal stent comprises a metal tungsten stent, a metal molybdenum stent.

8. A hot wire chemical vapor deposition device, comprising a plurality of hot wires horizontally placed, wherein both ends of the plurality of hot wires are respectively supported on a pair of brackets, characterized in that at least one bracket of the pair of brackets is a metal bracket according to any one of claims 1 to 7, and a weight is hung at one end of the hot wire supported on the metal bracket so as to straighten the hot wire by using the gravity of the weight.

9. The hot-wire chemical vapor deposition apparatus according to claim 8, wherein each of the pair of holders is the metal holder according to any one of claims 1 to 7, and both ends of the hot wire are supported by the metal holder after hanging a weight respectively.

10. The hot-wire chemical vapor deposition apparatus according to claim 8, wherein the other of the pair of holders is a fixed metal holder, and the other end of the hot wire is fixed to the fixed metal holder by a jig.