MPCVD device and its application

Abstract

The present invention provides an MPCVD device and its application, relating to the technical field of microwave plasma. The device comprises a coaxial line, an amplifying coaxial line, a first tapered impedance matcher, a second tapered impedance matcher, a plasma reaction chamber, a base, and a coaxial inner conductor suspended therein. The amplifying coaxial line converts the TEM mode in the coaxial line into a stable TEM mode in the amplifying coaxial line. The first tapered impedance matcher converts the TEM mode in the amplifying coaxial line into a TM01 mode within the cavity of the first tapered impedance matcher. The cavity of the plasma reaction chamber can amplify and maintain the TM01 mode and generate the TM02 mode, forming a mixed mode and enlarging the plasma generation area. The present invention solves the problems of a small microwave plasma area, low energy utilization, and small diamond production size, achieving simple operation, wide applicability, and the effect of producing more uniform and larger-area diamond films.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave plasma, and in particular to an MPCVD device and applications thereof. Background Art

[0002] Diamond is the hardest naturally occurring material and possesses exceptional physical and chemical properties in thermal, acoustic, optical, and electrical fields. Synthetic, high-quality diamond films possess numerous properties comparable to those of natural diamond, including high hardness, high thermal conductivity, low thermal expansion coefficient, and high light transmittance. Consequently, they have a wide range of industrial applications, such as in the manufacture of wear-resistant cutting tools, acoustic diaphragms, optical windows, and chip heat sinks. Furthermore, with traditional silicon-based semiconductors approaching their physical limits, diamond, with its ultra-wide bandgap and extremely high carrier mobility, has become a popular choice for next-generation semiconductors. To achieve these applications, not only high diamond quality is required, but also a large surface area is required. However, natural diamond reserves are limited, and large areas of high-quality diamond are rare and expensive. Therefore, the synthesis of high-quality diamond films has been a hot topic of research.

[0003] Currently, the main methods for preparing diamond films include combustion flame, hot filament plasma CVD, DC arc plasma torch, laser-assisted electron-enhanced CVD, radio frequency plasma CVD, and microwave plasma CVD. Microwave plasma chemical vapor deposition (MPCVD) not only produces high plasma density, a wide operating pressure range, high film quality, and fast speed, but also does not require electrodes during plasma generation, eliminating the introduction of electrode impurities, making it the optimal choice for preparing high-quality diamond films. Its operating principle is that microwaves generated by a microwave source are transmitted through a waveguide to a mode converter or directly coupled into a resonant cavity. They are then focused at the center above the substrate to form a strong electromagnetic field. The strong electromagnetic field excites the reactive gas in the vacuum reaction chamber, consisting of the resonant cavity and dielectric window, to produce plasma, thereby depositing the diamond film.

[0004] However, the preparation and application of high-quality diamond films still face several technical difficulties and challenges. For example, how to effectively improve the uniformity of large-area diamond films during the preparation process, how to significantly increase the deposition rate of diamond films, and how to reduce the surface roughness and defects of micron-scale diamond films are all technical difficulties that need to be solved urgently. To address these issues, researchers have developed many different types of high-power MPCVD devices, but these devices still have some shortcomings that limit their application and promotion. Therefore, it is necessary to develop MPCVD devices with higher performance.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] One of the purposes of the present invention is to provide an MPCVD device with a unique structural design, simple operation, wide applicability, the ability to operate in any microwave frequency band, and a special mode of mixing TM01 and TM02, which can produce more uniform and larger diamond films.

[0007] The second object of the present invention is to provide an application of an MPCVD device that can solve the problems of small and uneven microwave plasma area, low energy utilization, and small diamond preparation size, and can achieve outstanding application effects.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0009] In a first aspect, an MPCVD device includes an exterior portion of the device consisting of a coaxial line 1, an amplifying coaxial line 2, a first tapered impedance matcher 3, a second tapered impedance matcher 6, and a plasma reaction chamber 7 connected in sequence, and a coaxial inner conductor 4 passing through the coaxial line 1, the amplifying coaxial line 2, and the first tapered impedance matcher 3;

[0010] Wherein, the coaxial inner conductor 4 is suspended inside the device;

[0011] The amplifying coaxial line 2 adopts a stepped structure to convert the TEM mode in the coaxial line 1 into the amplifying coaxial line 2 to form a stable amplified TEM mode;

[0012] The first tapered impedance matcher 3 adopts a tapered structure to convert the TEM mode in the amplifying coaxial line 2 into the cavity of the first tapered impedance matcher 3 to form a TM01 mode;

[0013] A quartz plate 5 is provided between the first tapered impedance matcher 3 and the second tapered impedance matcher 6 to prevent contaminated gas from entering the plasma reaction chamber 7;

[0014] The cavity of the plasma reaction chamber 7 is a gradient structure under the quartz plate 5, which is used to amplify and maintain the TM01 mode and generate the TM02 mode, and finally form a mixed mode to enlarge the plasma generation area.

[0015] As a further technical solution, the coaxial inner conductor 4 is suspended above the first tapered impedance matcher 3 to better and more optimally convert the TEM mode into the TM01 mode.

[0016] As a further technical solution, the coaxial inner conductor 4 adopts a gradient structure.

[0017] As a further technical solution, the quartz plate 5 is placed in the middle of the cavity to pump the interior of the plasma reaction chamber 7 to a low pressure, reaching a vacuum state to facilitate the generation of plasma, and to isolate air from entering the plasma reaction chamber 7 to prevent the plasma from being contaminated.

[0018] As a further technical solution, the base 8 of the MPCVD device is arranged at the center of the plasma reaction chamber 7 to generate plasma at a location with a stronger electric field distribution, thereby depositing a diamond film over a larger area.

[0019] As a further technical solution, the base 8 includes but is not limited to a cylindrical structure, or a structure composed of at least two cylinders stacked up and down.

[0020] As a further technical solution, the coaxial inner conductor 4 is replaced as the internal pattern of the device changes, including but not limited to an elliptical structure.

[0021] In a second aspect, an MPCVD device as described in any one of the above items is used in the preparation of diamond films.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The MPCVD device provided by the present invention has a unique structural design. With the coordinated cooperation of various components, the device not only has the advantages of excellent vacuum performance and uniform deposition, but also has a special mode of mixing TM01 and TM02, thereby being able to produce more uniform and larger diamond films, solving the technical problems of the small and uneven microwave plasma area generated at the current stage, low energy utilization rate and small diamond preparation size.

[0024] The excitation principle of the MPCVD device of the present invention is to replace the traditional TEM mode and compressed TM01 mode excitation with a more uniform and higher power density TM01 and TM02 mixed mode, thereby realizing large-scale microwave plasma chemical vapor deposition through the TM02 and TM01 mixed mode; the plasma source and implementation method of the present invention have the characteristics of simple operation and strong theoretical basis; at the same time, the MPCVD device of the present invention has a wide applicability and can operate in any microwave frequency band. The only difference is that the device size is different in different frequency bands, while the implementation principle and method do not change at all.

[0025] The application of the MPCVD device provided by the present invention can avoid the problems of small and uneven microwave plasma area, low energy utilization, and small diamond preparation size, and can achieve outstanding application effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 A structural diagram of a microwave plasma chemical vapor deposition device (MPCVD device) provided in Example 1 of the present invention;

[0028] Figure 2 Schematic diagram of a microwave plasma chemical vapor deposition device (MPCVD device) provided in Example 1 of the present invention.

[0029] Icons: 1-coaxial line; 2-amplifying coaxial line; 3-first tapered impedance matching device; 4-coaxial inner conductor; 5-quartz plate; 6-second tapered impedance matching device; 7-plasma reaction chamber; 8-base. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] According to a first aspect of the present invention, there is provided an MPCVD apparatus, comprising an apparatus exterior consisting of a coaxial line 1, an amplifying coaxial line 2, a first tapered impedance matcher 3, a second tapered impedance matcher 6, and a plasma reaction chamber 7 connected in sequence, and a coaxial inner conductor 4 passing through the coaxial line 1, the amplifying coaxial line 2, and the first tapered impedance matcher 3;

[0032] Wherein, the coaxial inner conductor 4 is suspended inside the device;

[0033] The amplifying coaxial line 2 may adopt a stepped structure, which is used to convert the TEM mode in the coaxial line 1 into the amplifying coaxial line 2 to form a stable amplified TEM mode;

[0034] The first tapered impedance matcher 3 adopts a tapered structure to convert the TEM mode in the amplifying coaxial line 2 into the cavity of the first tapered impedance matcher 3 to form a TM01 mode;

[0035] A quartz plate 5 is provided between the first tapered impedance matcher 3 and the second tapered impedance matcher 6 to prevent contaminant gases from entering the plasma reaction chamber 7. The quartz plate 5 can isolate the plasma reaction chamber 7 from the air, thereby preventing contaminants in the air, such as oxygen and argon, from entering the plasma reaction chamber 7 and causing uneven diamond film formation. Quartz, as a high-temperature resistant material, can withstand the plasma temperature after plasma generation.

[0036] The tapered impedance matcher not only eliminates reflections but also suppresses interference from other modes on the working mode during mode conversion. Furthermore, the discontinuity between the circular waveguide and the coaxial line causes microwave energy reflection. The tapered impedance matcher can efficiently transfer the microwave energy from the coaxial line to the circular waveguide, thus achieving highly efficient energy utilization.

[0037] The plasma reaction chamber 7 has a cavity with a gradient structure under the quartz plate 5. Its function is to amplify and maintain the TM01 mode and generate the TM02 mode, and finally form a mixed mode to enlarge the plasma generation area, so that a large area of ​​diamond film can be deposited on the substrate.

[0038] The MPCVD device provided by the present invention is a microwave plasma device for diamond deposition. It has a unique structural design. With the coordinated cooperation of various components, the device not only has the advantages of excellent vacuum performance and uniform deposition, but also has a special mode of mixing TMO1 and TMO2, thereby being able to produce more uniform and larger diamond films, solving the technical problems of the small and uneven microwave plasma area, low energy utilization and small diamond preparation size at the current stage.

[0039] In a preferred embodiment, the coaxial inner conductor 4 can be suspended above the first tapered impedance matcher 3 to better and more optimally convert the TEM mode into the TM01 mode.

[0040] In a preferred embodiment, the coaxial inner conductor 4 can use a gradient structure, and the quartz plate 5 can be placed in the middle of the cavity to pump the interior of the plasma reaction chamber 7 to a low pressure and reach a vacuum state, thereby making it easier to generate plasma. At the same time, the plasma can be generated farther away from the quartz plate to avoid contamination caused by etching of the quartz plate, thereby producing higher quality diamonds.

[0041] In a preferred embodiment, the base 8 of the MPCVD device can be set at the center of the plasma reaction chamber 7. The base 8 can generate plasma at a stronger electric field distribution and make it more uniform for depositing diamond films, thereby producing diamond films of a larger area.

[0042] In a preferred embodiment, the base 8 includes a cylindrical structure, or may be a structure composed of at least two cylinders stacked up and down, but is not limited thereto.

[0043] In a preferred embodiment, the coaxial inner conductor 4 can be replaced as the internal pattern of the device changes, including but not limited to an elliptical structure.

[0044] To sum up, the excitation principle of the MPCVD device of the present invention is to convert the TM01 mode in the circular waveguide into the TEM mode through a waveguide coaxial converter, and then excite a more uniform, larger area, and higher power density TM01 and TM02 mixed mode above the base in the cylindrical cavity. Large-scale microwave plasma chemical vapor deposition is achieved through the TM02 and TM01 mixed mode. It not only has the characteristics of simple operation and strong theoretical basis of the plasma source and implementation method, but also has a wide applicability and can work in any microwave frequency band. The only difference is that the device size is different in different frequency bands, while the implementation principle and method do not change at all.

[0045] According to a second aspect of the present invention, there is provided a use of any of the above-mentioned MPCVD devices in the preparation of diamond films.

[0046] The application of the MPCVD device provided by the present invention can avoid the problems of small and uneven microwave plasma area, low energy utilization, and small diamond preparation size, and can achieve outstanding application effects.

[0047] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0048] Example 1

[0049] An MPCVD device, the structure diagram is shown in Figure 1 , see the schematic diagram Figure 2 , including an apparatus exterior consisting of a coaxial line 1, an amplifying coaxial line 2, a first tapered impedance matcher 3, a second tapered impedance matcher 6, and a plasma reaction chamber 7 connected in sequence, a coaxial inner conductor 4 passing through the coaxial line 1, the amplifying coaxial line 2, and the first tapered impedance matcher 3, and a base 8 with a stepped structure placed in the center of the plasma reaction chamber 7;

[0050] The amplifying coaxial line 2 adopts a stepped structure, which converts the TEM mode in the coaxial line 1 into the amplifying coaxial line 2 to form a stable amplified TEM mode;

[0051] The first tapered impedance matcher 3 adopts a tapered structure to convert the TEM mode in the amplifying coaxial line 2 into the cavity of the first tapered impedance matcher 3 to form a TM01 mode;

[0052] A quartz plate 5 is provided between the first tapered impedance matcher 3 and the second tapered impedance matcher 6. The quartz plate 5 can separate the plasma reaction chamber 7 from the air to prevent polluting gases in the air, such as oxygen and argon, from entering the plasma reaction chamber 7.

[0053] The coaxial inner conductor 4 is suspended inside the device, suspended above the first tapered impedance matcher 3, to better and more optimally convert the TEM mode into the TM01 mode. The coaxial inner conductor 4 uses a tapered structure, and the quartz plate 5 is placed in the middle of the cavity to pump the interior of the plasma reaction chamber 7 to a low pressure, achieving a vacuum state to facilitate plasma generation, and to prevent air from entering the plasma reaction chamber 7 to prevent plasma contamination.

[0054] The coaxial inner conductor 4 is replaced as the internal mode of the device changes. In this embodiment, the coaxial inner conductor 4 may be an elliptical structure.

[0055] The plasma reaction chamber 7 has a gradually changing structure under the quartz plate 5, which is used to amplify and maintain the TM01 mode and generate the TM02 mode, and finally form a mixed mode to enlarge the plasma generation area, thereby enabling the deposition of a large area of ​​diamond film on the base 8;

[0056] The base 8 is arranged at the center of the plasma reaction chamber 7. The base 8 can generate plasma at a location with a stronger electric field distribution and make it more uniform. In this embodiment, the base 8 can be a structure composed of two cylinders stacked up and down.

[0057] The MPCVD device provided in this embodiment has an excitation principle of converting the TM01 mode in the circular waveguide into the TEM mode through a waveguide coaxial converter, and then exciting a more uniform, larger-area, and higher-power-density TM01 and TM02 mixed mode in the cylindrical cavity, thereby achieving large-scale microwave plasma chemical vapor deposition through the TM02 and TM01 mixed mode. The device not only has the characteristics of simple operation and strong theoretical basis of the plasma source and implementation method, but also has a wide applicability and can operate in any microwave frequency band. The only difference is the device size in different frequency bands, while the implementation principle and method do not change at all.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An MPCVD device, characterized in that: The device comprises an outer portion of a coaxial line (1), an amplifying coaxial line (2), a first tapered impedance matching device (3), a second tapered impedance matching device (6), and a plasma reaction chamber (7) connected in sequence, and a coaxial inner conductor (4) passing through the coaxial line (1), the amplifying coaxial line (2), and the first tapered impedance matching device (3); Wherein, the coaxial inner conductor (4) is suspended inside the device; The amplifying coaxial line (2) adopts a stepped structure, so as to convert the TEM mode in the coaxial line (1) into a stable amplified TEM mode in the amplifying coaxial line (2); The first tapered impedance matcher (3) adopts a tapered structure to convert the TEM mode in the amplified coaxial line (2) into the cavity of the first tapered impedance matcher (3) to form a TM 01 model; A quartz plate (5) is provided between the first tapered impedance matcher (3) and the second tapered impedance matcher (6) to prevent contaminated gas from entering the plasma reaction chamber (7); The second gradient impedance matcher (6) is located below the quartz plate (5), the chamber of the plasma reaction chamber (7) is located below the second gradient impedance matcher (6), and TM 01 The mode is amplified by the second tapered impedance matching device (6) and generates TM 02 model.

2. The MPCVD device according to claim 1, wherein The coaxial inner conductor (4) adopts a gradient structure.

3. The MPCVD device according to claim 1, wherein The base (8) of the MPCVD device is arranged at the center of the plasma reaction chamber (7) and is used to generate plasma at a location with a strong electric field distribution, thereby depositing a diamond film over a larger area.

4. The MPCVD device according to claim 3, characterized in that The base (8) comprises a cylindrical structure.

5. The MPCVD device according to claim 3, characterized in that The base (8) comprises a structure consisting of at least two cylinders stacked up and down.

6. The MPCVD device according to claim 2, wherein: The coaxial inner conductor (4) comprises an elliptical structure.

7. Use of the MPCVD device according to any one of claims 1 to 6 in the preparation of diamond films.

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