MPCVD online plasma ball position adjustment device and method

Abstract

The present invention proposes an MPCVD device and method for adjusting the position of a plasma ball online, the device comprises a bottom plate; a shell whose lower end face is fixed to the bottom plate, and an air hole is provided on the top; an inner cavity shell is used to generate a plasma ball and adjust the position of the plasma ball, which is located in the shell, and its lower end face is against the bottom plate and can move along the bottom plate, and the inner cavity shell, the shell and the bottom plate together form a sandwich space for gas flow, which comprises an upper cavity and a middle cavity connected in sequence; the lower cavity is used to feed microwaves into the middle cavity, which is located in the middle cavity and is surrounded by a circular quartz microwave window and a water-cooling platform; an outer cavity adjustment mechanism is used to adjust the position of the inner cavity shell in the shell, which is fixed to the outer wall of the shell, and its output end passes through the shell and is fixed to the inner cavity shell, and its output end can drive the inner cavity shell to move horizontally. The present invention can adjust the central position of the inner cavity at any time so that the plasma ball is located in the middle of the sample stage.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical vapor deposition diamond, and in particular is a device and a method for adjusting the position of a plasma ball online by MPCVD. Background Art

[0002] Chemical vapor deposition (CVD) diamond film has many advantages such as high hardness, good thermal conductivity, small thermal expansion coefficient, excellent optical and electrical properties, fast sound propagation speed, and good dielectric properties. It has broad application prospects in fields such as infrared optical windows, high-power LEDs, heat sinks for high-power and high-frequency electronic and optoelectronic devices and systems, high-performance radiation-resistant detectors and sensors. At present, the most commonly used methods for preparing diamond are hot wire chemical vapor deposition (HFCVD), DC arc plasma jet chemical vapor deposition (DC arc plasmajet CVD) and microwave plasma chemical vapor deposition (MPCVD). Among these three methods, the MPCVD method is characterized by good controllability of the diamond deposition process and no pollution of the discharge electrode. It is the preferred method for preparing high-quality diamonds internationally.

[0003] Carbon-based semiconductors can more effectively enhance chip performance. However, as the main artificial polycrystalline diamond manufacturing equipment, MPCVD is affected by many factors during diamond growth. One of the most important factors is the temperature balance of the diamond single crystal seed and the polycrystalline film. In the process of growing single crystal or polycrystalline diamond, the position of the plasma ball is not in the center, resulting in asymmetric energy distribution in various parts during polycrystalline coating or deposition of single crystals. The temperature difference between various parts is large, and the deposited film grows to a certain thickness, which often causes the substrate to break.

[0004] For the butterfly cavity, it is mainly used for high-power MPCVD equipment of 8KW and above. Compared with 6KW equipment, it has higher energy and temperature. If the position of the plasma ball is found to be offset after the plasma source is ignited, the cavity must be opened to adjust the position of the cavity cover. The process includes shutting down the plasma source, closing the air inlet line, and backfilling the vacuum system. The whole process takes a long time. This invention realizes a method for online adjustment of the center position of the plasma ball.

[0005] For MPCVD equipment, the deposition of polycrystalline and single crystal diamond is a long process, in which many factors affect the quality of deposited diamond, mainly temperature, gas pressure, gas flow, and microwave power. Traditional equipment defaults to the plasma ball being in the middle position, but in actual work, the position of the plasma ball is affected by many factors, such as the centering of the resonant cavity, the position of the reverse adjustment tuning knob, and whether the sample stage is level. Therefore, it is necessary to frequently open the cavity to adjust the center position of the sample stage so that the sample is located below the center of the plasma, so that the ideal diamond film or single crystal can be chemically deposited.

[0006] In the existing dish-shaped cavity MPCVD device, if the position of the plasma ball is found to be offset, the position of the outer shell is generally adjusted. Because the outer shell vacuum seals the cavity, each time the position of the outer shell is adjusted, the vacuum needs to be unloaded, the outer shell position is adjusted according to visual inspection, and then the vacuum is restarted. If the position is not ideal, this step needs to be repeated until the plasma ball is centered. Therefore, the whole process takes a lot of time and the adjustment accuracy cannot be guaranteed. As a butterfly cavity MPCVD, its advantage is that the waveguide antenna is placed under the cavity, so that the microwave power can be increased without corroding the quartz window. However, the higher the power, the higher the temperature. Due to the high temperature in the center of the plasma ball and the low temperature in the periphery, the higher the temperature, the more likely it is to cause temperature unevenness. If the plasma ball is not in the center, the diamond is heated unevenly, which will cause the diamond to break during the deposition process.

[0007] In summary, up to now, various types of microwave plasma reaction devices for chemical vapor deposition of diamond films used and proposed by people all have different factors that are not conducive to the preparation of high-quality diamond films under high-power conditions. Therefore, there is an urgent need to design a high-power reaction device with perfect structure and performance to meet the rapid preparation of high-quality diamonds. Summary of the invention

[0008] The purpose of the present invention is to provide an MPCVD online plasma ball position adjustment device and method, which can adjust the center position of the inner cavity at any time so that the plasma ball is located in the middle of the sample stage. To achieve the above purpose, the technical solution adopted is as follows:

[0009] An MPCVD device for adjusting the position of a plasma ball online, comprising:

[0010] Bottom plate 5;

[0011] The housing 12 has a lower end surface fixed to the bottom plate 5 and a vent 13 formed on the top;

[0012] The inner cavity shell 18 is used to generate the plasma ball 15 and adjust the position of the plasma ball 15. The inner cavity shell 18 is located in the outer shell 12, and its lower end face abuts against the bottom plate 5 and can move along the bottom plate 5. The inner cavity shell 18, the outer shell 12, and the bottom plate 5 together form a sandwich space for gas flow, which includes an upper cavity 1 and a middle cavity 2 that are connected in sequence; the inner cavity shell 18 has an inner cavity air hole 19 at the top;

[0013] The lower cavity 3 is used to feed microwaves into the middle cavity 2. The lower cavity 3 is located in the middle cavity 2 and is surrounded by a circular quartz microwave window 6 and a water-cooling platform 4. The circular quartz microwave window 6 is fixed between the bottom plate 5 and the lower end surface of the water-cooling platform 4.

[0014] The extracavity adjustment mechanism is used to adjust the position of the inner cavity shell 18 in the outer shell 12. It is fixed to the outer wall of the outer shell 12. Its output end passes through the outer shell 12 and is fixed to the inner cavity shell 18. Its output end can drive the inner cavity shell 18 to move horizontally.

[0015] Preferably, the extracavitary adjustment mechanism comprises:

[0016] a knob bracket 24 fixed to the outer wall of the housing 12;

[0017] The driving unit 22 is fixed to the knob bracket 24, and its output end is connected to a screw rod, and the screw rod is threadedly connected to the movable connecting plate 26;

[0018] The sealing flange 25 has one side fixed to the movable connecting plate 26 and the other side fixed to the first open end of the bellows 21. The second open end of the bellows 21 is connected to the housing 12. The bellows 21 is retractable.

[0019] And an adjusting rod 20 , which is located in the bellows 21 , one end of which passes through the housing 12 and forms the output end of the extracavity adjusting mechanism, and the other end is fixed to the sealing flange 25 .

[0020] Preferably, a sealing rubber 17 is provided between the annular quartz microwave window 6 and the water-cooling platform 4 , and between the annular quartz microwave window 6 and the bottom plate 5 ; and a sealing ring 27 is provided between the housing 12 and the bottom plate 5 .

[0021] Preferably, a shell waveguide 11 is installed on the outer bottom surface of the bottom plate 5, and the shell waveguide 11 is sleeved on the outer water pipe 8, and the inner water pipe 16 and the central water pipe 9 are sequentially sleeved in the outer water pipe 8;

[0022] The shell waveguide 11 is provided with a microwave feed port 10, and a channel for microwave transmission is formed between the shell waveguide 11 and the outer water pipe 8; the bottom of the channel is closed, and the top thereof is connected to the bottom plate 5 and the lower cavity 3;

[0023] The outer water pipe 8, the inner water pipe 16 and the central water pipe 9 are all fixed to the water-cooling platform 4. The gap between the outer water pipe 8 and the inner water pipe 16 is used for cooling water to be introduced into the internal water circuit of the water-cooling platform 4. The internal water circuit of the water-cooling platform 4 is connected to the top of the central water pipe 9; the bottom end of the central water pipe 9 is open for cooling water to flow out.

[0024] Preferably, the vacuum port 23 is opened on the bottom plate 5 , communicated with the middle cavity 2 and located outside the lower cavity 3 .

[0025] Preferably, the sample stage 28 is installed on the water-cooling platform 4 , and the diamond deposition substrate 14 is placed on the sample stage 28 .

[0026] Preferably, the housing 12 is a disc-shaped cavity or a cylindrical cavity.

[0027] A method for adjusting the position of a plasma ball in MPCVD online comprises the following steps:

[0028] The driving unit 22 is started, and the driving unit drives the screw to rotate;

[0029] The movable connecting plate 26 moves in the horizontal direction under the drive of the screw rod, and the movable connecting plate 26 drives the sealing flange 25 to move, the bellows 21 expands and contracts, and the adjusting rod 20 moves with the sealing flange 25. The movement of the adjusting rod 20 drives the inner cavity shell 18 to move, thereby realizing the position adjustment of the inner cavity shell 18, so that the plasma sphere 15 is located in the middle of the sample stage.

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] 1. It includes an external vacuum cavity and an internal disc-shaped resonant cavity. The top of the external cavity is circular and a water-cooling pipeline and an air intake pipeline are installed in the cavity. The inner cavity has an air intake pipeline, and a microwave antenna, a microwave waveguide, and a sample table water cooling mechanism are provided at the bottom. The inner cavity and the adjustment knob outside the equipment are connected by a connecting rod, which can adjust the front and back and left and right positions of the inner cavity.

[0032] 2. The center position of the inner cavity can be adjusted at any time so that the plasma ball is located in the middle of the sample stage, achieving uniform temperature and adjustable position, achieving ideal uniformity in the diamond deposition process, and controllable high-energy center position. The reaction gas is evenly distributed, and high-purity, uniform-thickness polycrystalline diamond film materials and single-crystal diamonds can be prepared with high temperature uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Structural diagram of the device for online adjustment of plasma ball position for MPCVD;

[0034] Figure 2 This is a diagram of the process of plasma ball formation;

[0035] Figure 3 A top view of the device when the housing is a cylindrical structure;

[0036] Figure 4 This is a structural diagram of the extracavity adjustment mechanism.

[0037] Among them, 1-upper cavity, 2-middle cavity, 3-lower cavity, 4-water cooling platform, 5-bottom plate, 6-annular quartz microwave window, 7-base fixing plate, 8-outer water pipe, 9-center water pipe, 10-microwave feed port, 11-shell waveguide, 12-shell, 13-air hole, 14-diamond deposition substrate, 15-plasma ball, 16-inner water pipe, 17-sealing rubber, 18-inner cavity shell, 19-inner cavity air hole, 20-adjusting rod, 21-bellows, 22-driving unit, 23-vacuum outlet, 24-knob bracket, 25-sealing flange, 26-movable connecting plate, 27-sealing ring, 28-sample platform. DETAILED DESCRIPTION

[0038] The following will be described in more detail with reference to the schematic diagram of the MPCVD on-line plasma ball position adjustment device and method of the present invention, wherein the preferred embodiment of the present invention is shown, and it should be understood that the present invention described herein can be modified by a person skilled in the art, while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as being widely known to a person skilled in the art, and not as a limitation of the present invention.

[0039] like Figure 1 As shown in the figure, the MPCVD equipment for adjusting the position of the plasma ball online adopts a double cavity structure of inner cavity and outer cavity while maintaining the traditional resonant cavity shape. The inner cavity is used as the resonant cavity, replacing the traditional mode of using the outer cavity as the resonant cavity, and then the position of the inner cavity is adjusted through an external adjustment device, thereby realizing the function of adjusting the position of the plasma ball online.

[0040] The device can overcome the shortcomings of various existing reaction devices to varying degrees, such as lack of adjustment mechanism, poor focusing ability, difficulty in water cooling of key components, energy dispersion, and uneven temperature distribution on the substrate surface. Therefore, it can be used for uniform and rapid deposition of high-quality diamond films under high-power conditions.

[0041] The equipment specifically includes:

[0042] The bottom plate 5 and the vacuum extraction port 23 (connected to the vacuum pump) are opened on the bottom plate 5 , which are connected to the middle cavity 2 and are located outside the lower cavity 3 .

[0043] The outer bottom surface of the bottom plate 5 is provided with a shell waveguide 11, the shell waveguide 11 is sleeved on the outer water pipe 8, and the inner water pipe 16 and the central water pipe 9 are sleeved in sequence in the outer water pipe 8;

[0044] A microwave feed port 10 is provided on the shell waveguide 11, and a channel for microwave transmission is formed between the shell waveguide 11 and the outer water pipe 8; the bottom of the channel is closed (so that the microwaves go upward along the outer wall of the outer water pipe 8), and the top thereof is connected to the bottom plate 5 and the lower cavity 3;

[0045] The outer water pipe 8, the inner water pipe 16 and the central water pipe 9 are all fixed to the water cooling platform 4. The gap between the outer water pipe 8 and the inner water pipe 16 is used for cooling water to be introduced into the internal water circuit of the water cooling platform 4. The internal water circuit of the water cooling platform 4 is connected to the top of the central water pipe 9; the bottom end of the central water pipe 9 is open for cooling water to flow out.

[0046] The housing 12 has a lower end surface fixed to the bottom plate 5 and a vent 13 formed on the top. The housing 12 is a disc-shaped cavity (in this embodiment) or a cylindrical cavity. A cylindrical inner cavity structure is installed inside the cylindrical cavity, such as Figure 3 shown.

[0047] The mainstream equipment on the market now is still a cylindrical resonant cavity (with a diameter of about 120-160mm). At this time, a cylindrical inner cavity with a smaller diameter can be added inside the cylindrical cavity, and then the same external adjustment structure of the present invention is used to adjust the inner cavity, thereby achieving the adjustment of the plasma ball position.

[0048] The inner cavity shell 18 is used to generate the plasma ball 15 and adjust the position of the plasma ball 15. It is located in the outer shell 12, and its lower end face is against the bottom plate 5 and can move along the bottom plate 5. The inner cavity shell 18, the outer shell 12, and the bottom plate 5 together form an interlayer space for gas flow, which includes an upper cavity 1 and a middle cavity 2 connected in sequence; an inner cavity air hole 19 is opened at the top of the inner cavity shell 18.

[0049] The upper cavity 1 and the middle cavity 2 are sealed by the outer shell 12 and the bottom plate 5 through the sealing strip 27 to form a vacuum cavity.

[0050] The inner cavity is inside the outer cavity and independently bears the function of reflecting microwaves (used to reflect microwaves). Moreover, it is used independently of the entire system inside the vacuum. Because of its thin wall thickness, it can be processed into various shapes according to simulation requirements. For example, stamping and then polishing can obtain various extremely low-cost, different shapes, and more complex structures, making it possible to explore more ideal resonant cavity structures.

[0051] Therefore, the inner cavity does not have the function of sealing the vacuum inside the vacuum, so the position can be adjusted arbitrarily, but at the same time the inner cavity replaces the role of the outer cavity in reflecting microwaves to form plasma.

[0052] Therefore, the inner cavity shell 18 has a simple structure. Compared with the traditional outer cavity, it eliminates the complex water cooling structure (distributed inside the outer shell cavity wall) and the air intake structure, has a low manufacturing cost, replaces the outer cavity to reflect and resonate microwaves to form a plasma ball, and the shape optimization is simple and changeable, saving a lot of costs.

[0053] The lower cavity 3 is connected to the atmosphere and is used to feed microwaves into the middle cavity 2. It is located in the middle cavity 2 and is surrounded by a circular quartz microwave window 6 and a water-cooled platform 4. The circular quartz microwave window 6 is fixed between the bottom plate 5 and the lower end surface of the water-cooled platform 4. The sample stage 28 is installed on the water-cooled platform 4, and the diamond deposition substrate 14 (4-6 inch single crystal silicon wafer or molybdenum wafer) is placed on the sample stage 28.

[0054] Below the water-cooling platform 4 is a base fixing plate 7, which is provided with screw step holes and connected to the water-cooling platform 4. The base fixing plate 7 is provided with holes for the outer water pipe 8, the inner water pipe 16 and the central water pipe 9 to pass through.

[0055] Sealing rubbers 17 are provided between the annular quartz microwave window 6 and the water-cooling platform 4 and between the annular quartz microwave window 6 and the bottom plate 5 for sealing the vacuum (the upper cavity 1 and the middle cavity 2 ); a sealing ring 27 is provided between the housing 12 and the bottom plate 5 .

[0056] like Figure 4 The extracavity adjustment mechanism is used to adjust the position of the inner cavity shell 18 in the outer shell 12. It is fixed to the outer wall of the outer shell 12. Its output end passes through the outer shell 12 and is fixed to the inner cavity shell 18. Its output end can drive the inner cavity shell 18 to move horizontally.

[0057] Specifically, the extracavitary adjustment mechanism includes:

[0058] a knob bracket 24 fixed to the outer wall of the housing 12;

[0059] The driving unit 22 (knob or motor) is fixed to the knob bracket 24, and its output end is connected to the screw rod, which is threadedly connected to the movable connecting plate 26;

[0060] The sealing flange 25 has one side surface fixed to the movable connecting plate 26 and the other side surface fixed to the first open end of the bellows 21. The second open end of the bellows 21 is connected to the housing 12. The bellows 21 is retractable.

[0061] The sealing flange 25 and the bellows 21 are sealed and welded to form a vacuum sealing structure.

[0062] Due to the expansion and contraction characteristics of the bellows, the vacuum sealing is ensured, and the expansion and contraction can be used to relatively move the position. This external adjustment system has one in each of the two vertical directions X and Y of the shell 12, which can adjust the position of the inner cavity in the X and Y directions.

[0063] The regulating rod 20 is located in the bellows 21 , one end of which passes through the housing 12 and forms the output end of the extracavity regulating mechanism, and the other end of which is fixed to the sealing flange 25 .

[0064] The movable connecting plate 26 will move horizontally under the drive of the screw, and the movable connecting plate drives the sealing flange to move. At this time, the bellows will expand and contract, and the adjusting rod will also move. Because the adjusting rod is connected to the inner cavity, the movement of the adjusting rod drives the movement of the inner cavity, thereby realizing the adjustment of the inner cavity position, making the energy distribution uniform and more reasonable and symmetrical.

[0065] In actual application, a linear guide should be used between the movable connecting plate and the knob bracket to avoid tilting of the movable connecting plate.

[0066] like Figure 2 As shown, microwaves are fed in from below, converted by the antenna (shell waveguide 11) and introduced into the inner cavity, and are focused above the diamond deposition substrate 14 after being reflected by the inner cavity, and resonate with the introduced mixed gas. The mixed gas is mainly H2, and also includes CH4 and O2, etc. The mixed gas is excited by microwaves to form a plasma ball, and a diamond chemical deposition environment is formed under a specific vacuum environment.

[0067] Preferably, the entire extracavity adjustment mechanism is installed one each in the X and Y directions (horizontal direction) of the external cavity (see Figure 3 ) can show the adjustment of the inner cavity front and back and left and right.

[0068] In this embodiment, without changing the outer shell 12, if the accuracy of the entire device is relatively high and the adjustment distance requirement for the inner cavity shell 18 is relatively low, the wall thickness of the inner cavity shell 18 can be processed very thin, such as about 0.5 mm, and the distance between the inner cavity shell 18 and the outer shell 12 is 5 mm.

[0069] For high-power dish-shaped cavities, since the diameter of the cavity itself is very large (generally above 300 mm), adding an inner cavity inside the outer cavity will hardly change the shape of the entire resonant cavity and will not affect the shape and focusing effect of the resonant cavity.

[0070] The key component of the device proposed in the present invention is the inner cavity, which is extremely low compared to the outer shell cavity, which is conducive to matching a variety of electric field simulations, processing different inner cavity shapes, and using inner cavity tests of various shapes.

[0071] Another practical application of the present invention is that the microwave reflection function of the outer cavity is replaced by the inner cavity, and the performance of the microwave resonant cavity is closely related to the shape of the cavity. Previous experiments have shown that in order to obtain an ideal electric field distribution of the resonant cavity, the shape optimization of the resonant cavity often requires many computer simulations and actual tests. For a traditional resonant cavity, since the outer cavity has air guide holes and heat conduction grooves, the structure of the outer cavity is extremely complex and the processing cost is very high. Each experiment requires a high cost.

[0072] The present invention replaces the outer cavity with an inner cavity of a relatively simple structure. During the experiment, multiple shapes of inner cavities can be processed at a very low cost to achieve inner cavity structures of different shapes, which is conducive to more economical optimization of the shape of the resonant cavity.

[0073] Working principle:

[0074] 1. Steps for forming the plasma ball 15:

[0075] The microwaves are fed into the outer shell waveguide 11 through the microwave feeding port 10. The outer water pipe 8 inside the outer shell waveguide 11 also serves as a conversion antenna (the microwaves go upward along the outer wall of the outer water pipe 8), and the fed microwaves are introduced into the lower cavity 3. Then, the microwaves pass through the annular quartz window 6 into the middle cavity 2, and after being reflected by the inner wall of the middle cavity 2, they enter the upper cavity 1, which is also called a resonant cavity, and a plasma ball 15 is subsequently formed here.

[0076] The gas enters the interlayer between the inner cavity shell 18 and the outer cavity 12 through the air hole 13 of the outer cavity 12 , and then is introduced into the upper cavity 1 through the inner cavity air hole 19 .

[0077] Under a certain gas pressure and after microwave resonance, the gas forms a plasma ball 15 in the upper cavity 1, and the plasma ball acts on the polycrystalline or single crystal substrate on the sample stage 14 to perform chemical deposition to form polycrystalline or single crystal diamond.

[0078] 2. When the plasma ball 15 is not located in the middle of the sample stage (observe the center position of the plasma ball, or observe the temperature color of the deposition substrate, the higher the temperature, the brighter the substrate), the steps for adjusting the position of the inner cavity shell 18 are as follows:

[0079] The movable connecting plate 26 moves in the horizontal direction under the action of the screw and the driving unit, and the movable connecting plate drives the sealing flange to move. At this time, the bellows will expand and contract, and the adjusting rod will also move with it. Because the adjusting rod is connected to the inner cavity, the movement of the adjusting rod drives the movement of the inner cavity, thereby realizing the adjustment of the position of the inner cavity. Therefore, the mechanism can adjust the center position of the inner cavity at any time, so that the plasma sphere is located in the middle of the sample stage, and the diamond deposition substrate 14 is always located in the middle of the sample stage.

[0080] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. An MPCVD device for adjusting the position of a plasma ball online, characterized in that: include: Bottom plate (5); The outer shell (12) has a lower end surface fixed to the bottom plate (5) and an air hole (13) formed on the top; An inner cavity shell (18) is used to generate a plasma ball (15) and adjust the position of the plasma ball (15). The inner cavity shell (18) is located inside the outer shell (12). Its lower end face abuts against the bottom plate (5) and can move along the bottom plate (5). The inner cavity shell (18), the outer shell (12) and the bottom plate (5) together form an interlayer space for gas flow, and the inner cavity shell (18) comprises an upper cavity (1) and a middle cavity (2) which are connected in sequence. An inner cavity air hole (19) is provided at the top of the inner cavity shell (18); A lower cavity (3) is used to feed microwaves into the middle cavity (2), which is located in the middle cavity (2) and is surrounded by a circular quartz microwave window (6) and a water-cooling platform (4), wherein the circular quartz microwave window (6) is fixed between the bottom plate (5) and the lower end surface of the water-cooling platform (4); The extracavity adjustment mechanism is used to adjust the position of the inner cavity shell (18) in the outer cavity shell (12). The mechanism is fixed to the outer wall of the outer cavity shell (12). The output end of the mechanism passes through the outer cavity shell (12) and is fixed to the inner cavity shell (18). The output end of the mechanism can drive the inner cavity shell (18) to move horizontally.

2. The MPCVD on-line plasma ball position adjustment device according to claim 1, characterized in that: The extracavity adjustment mechanism comprises: A knob bracket (24) fixed to the outer wall of the housing (12); A driving unit (22) is fixed to the knob bracket (24), and an output end thereof is connected to a screw rod, and the screw rod is threadedly connected to the movable connecting plate (26); A sealing flange (25), one side of which is fixed to the movable connecting plate (26), and the other side of which is fixed to the first open end of the bellows (21), the second open end of the bellows (21) being connected to the housing (12); the bellows (21) is retractable; and an adjusting rod (20), which is located in the bellows (21), one end of which passes through the housing (12) and forms the output end of the extracavity adjusting mechanism, and the other end of which is fixed to the sealing flange (25).

3. The MPCVD on-line plasma ball position adjustment device according to claim 1, characterized in that: Sealing rubber (17) is provided between the annular quartz microwave window (6) and the water-cooling platform (4), and between the annular quartz microwave window (6) and the bottom plate (5); and a sealing ring (27) is provided between the housing (12) and the bottom plate (5).

4. The MPCVD on-line plasma ball position adjustment device according to claim 1, characterized in that: An outer bottom surface of the bottom plate (5) is provided with an outer shell waveguide (11), the outer shell waveguide (11) is sleeved on an outer water pipe (8), and an inner water pipe (16) and a central water pipe (9) are sleeved in sequence inside the outer water pipe (8); A microwave feed port (10) is provided on the shell waveguide (11), and a channel for microwave transmission is formed between the shell waveguide (11) and the outer water pipe (8); the bottom of the channel is closed, and the top is connected to the bottom plate (5) and the lower cavity (3); The outer water pipe (8), the inner water pipe (16) and the central water pipe (9) are all fixed to the water cooling platform (4); the gap between the outer water pipe (8) and the inner water pipe (16) is used to introduce cooling water into the internal water circuit of the water cooling platform (4); the internal water circuit of the water cooling platform (4) is connected to the top end of the central water pipe (9); the bottom end of the central water pipe (9) is open to allow cooling water to flow out.

5. The MPCVD on-line plasma ball position adjustment device according to claim 1, characterized in that: The vacuum extraction port (23) is opened on the bottom plate (5), communicates with the middle cavity (2) and is located outside the lower cavity (3).

6. The MPCVD on-line plasma ball position adjustment device according to claim 1, characterized in that: The sample stage (28) is installed on the water-cooling platform (4), and the diamond deposition substrate (14) is placed on the sample stage (28).

7. The MPCVD on-line plasma ball position adjustment device according to claim 1, characterized in that: The housing (12) is a disc-shaped cavity or a cylindrical cavity.

8. A method for adjusting the position of a plasma ball in MPCVD online, based on the device for adjusting the position of a plasma ball in MPCVD online according to claim 2, characterized in that: The following steps are involved, including: Starting the driving unit (22), which drives the screw to rotate; The movable connecting plate (26) moves in a horizontal direction under the drive of the screw rod, the movable connecting plate (26) drives the sealing flange (25) to move, the bellows (21) expands and contracts, the adjusting rod (20) moves along with the sealing flange (25), and the movement of the adjusting rod (20) drives the inner cavity shell (18) to move, thereby realizing the position adjustment of the inner cavity shell (18), so that the plasma sphere (15) is located in the middle of the sample stage.

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