MPCVD dish-shaped cavity structure and method for enlarging diamond deposition area

Abstract

The present invention proposes a structure and method for expanding diamond deposition area of ​​an MPCVD dish-shaped cavity, the structure comprising: a bottom plate; a shell, the lower end face of which is fixed to the bottom plate, and the top of which is provided with air holes; the shell is surrounded by an upper cavity and a middle cavity which are connected in sequence; the upper cavity is a resonant cavity; the middle cavity is used to introduce microwaves, and its inner wall reflects the microwaves to feed them into the upper cavity, in which a diamond deposition substrate is arranged, and the diamond deposition substrate is placed on a sample platform; and a wave cutting platform is used to reflect the microwaves fed into the upper cavity, which is located in the upper cavity and above the diamond deposition substrate; the wave cutting platform is fixed to a mounting rod, and the mounting rod is mounted on the shell and its height is adjustable. In the present invention, plasma can be deposited along the entire diamond deposition substrate, thereby increasing the deposition area.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical vapor deposition diamond, and in particular is an MPCVD dish-shaped cavity structure and method for expanding diamond deposition area. Background Art

[0002] Chemical vapor deposition (CVD) diamond films offer numerous advantages, including high hardness, good thermal conductivity, low thermal expansion coefficient, excellent optical and electrical properties, fast acoustic propagation velocity, and good dielectric properties. These advantages hold great promise for applications in fields such as infrared optical windows, high-power LEDs, heat sinks for high-power and high-frequency electronic and optoelectronic devices and systems, and high-performance radiation-resistant detectors and sensors. Currently, the most commonly used methods for producing diamond are hot-filament chemical vapor deposition (HFCVD), direct current arc plasma jet chemical vapor deposition (DC arc plasma jet CVD), and microwave plasma chemical vapor deposition (MPCVD). Of these three methods, MPCVD is characterized by its highly controllable diamond deposition process and its lack of discharge electrode contamination, making it the preferred method for producing high-quality diamond internationally.

[0003] Microwave plasma-assisted chemical vapor deposition (MPCVD) is currently the most popular and promising method for epitaxially growing large, high-quality diamond single crystals. This method involves directing microwaves generated by a microwave generator through a waveguide into a specially designed reaction chamber, where they resonate and generate an electromagnetic field with a uniform frequency and intensity distribution. This field excites the gas feedstock (typically a mixture of H₂ and CH₄) within the reaction chamber, generating a uniform and stable plasma on the sample stage. The ionized gas molecules are then deposited on the substrate, achieving epitaxial growth of diamond. Deposition of polycrystalline and single-crystal diamond using MPCVD equipment is a lengthy process, influenced by numerous factors, including temperature, pressure, gas flow rate, and microwave power. Another key factor is the conditions under which the resonant microwave reflections form standing waves. These conditions directly determine plasma ignition, plasma stability, and the size of the deposition area. The size of the deposition area determines diamond deposition efficiency and productivity, impacting the company's profitability and production capacity.

[0004] Traditional polycrystalline diamond deposition has been unable to break through the limitations of large-area polycrystalline diamond deposition. Currently, the mainstream polycrystalline diamonds on the market are mostly 2-3 inches. With the increasing application of diamond in various fields, especially the semiconductor field, the market demand for large-area polycrystalline diamonds is rapidly increasing. For companies, it is necessary to produce large-area diamond films as soon as possible. Summary of the Invention

[0005] The present invention aims to provide a structure and method for expanding the diamond deposition area in an MPCVD dish-shaped cavity, optimizing the position and area of ​​the wave-chopping platform within the cavity, achieving stable microwave resonance, and forming a high-energy and stable plasma ball, thereby obtaining a larger diamond deposition area on the diamond deposition plate 14. To achieve the above objectives, the following technical solutions are adopted:

[0006] An MPCVD dish-shaped cavity structure for expanding diamond deposition area, comprising:

[0007] Bottom plate 5;

[0008] The housing 12 has a lower end surface fixed to the bottom plate 5 and an air hole 13 formed on the top. The housing 12 encloses an upper cavity 1 and a middle cavity 2 that are connected in sequence.

[0009] The upper cavity 1 is a resonant cavity;

[0010] The middle cavity 2 is used to introduce microwaves, and its inner wall reflects the microwaves to feed them into the upper cavity 1, in which a diamond deposition substrate 14 is arranged. The diamond deposition substrate 14 is placed on the sample platform 28;

[0011] and a wave cutting platform 21 for reflecting the microwave fed into the upper cavity 1 to form a resonant wave, which is located in the upper cavity 1 and above the diamond deposition substrate 14;

[0012] The chopping platform 21 is fixed to a mounting rod 19 , and the mounting rod 19 is mounted on the housing 12 and its height is adjustable.

[0013] Preferably, the height difference h1 between the wave cutting platform 21 and the sample platform 28 is in the range of 50-75 mm;

[0014] The area A of the lower surface of the wave chopping platform 21 and the diameter of the lower surface range are: 50-100 mm.

[0015] Preferably, the height difference h2 between the wave cutting platform 21 and the bottom plate 5 is in the range of 100-130 mm.

[0016] Preferably, the side of the wave cutting platform 21 facing the diamond deposition substrate 14 is a plane, and uniformly distributed uniform air holes are provided on the plane.

[0017] Preferably, a water cooling system 22 is provided in the mounting rod 19 .

[0018] Preferably, the mounting rod 19 is threadedly connected to the housing 12 .

[0019] Preferably, it further comprises: a lower cavity 3 for feeding 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;

[0020] The annular quartz microwave window 6 is fixed between the bottom plate 5 and the lower end surface of the water-cooling platform 4 .

[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 sleeved in sequence inside the outer water pipe 8;

[0022] 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 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] A method for expanding the diamond deposition area of ​​an MPCVD dish-shaped cavity comprises the following steps:

[0025] Step 1: The microwaves are reflected by the inner wall of the middle cavity 2 and gathered above the diamond deposition substrate 14;

[0026] The microwave is then reflected at the chopping stage 21, forming a resonant wave between the deposition substrate 14 and the chopping stage 21;

[0027] At the same time, the mixed gas enters the upper cavity 1 through the air holes 13 of the shell 12;

[0028] Step 2: The resonant wave and the introduced mixed gas resonate to form a plasma ball 15 . The deposition range of the plasma ball 15 is the entire large-area diamond deposition substrate 14 .

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] Through the cooperation of the middle cavity 2 and the wave cutting platform 21, the shape of the resonant cavity is optimized to the greatest extent, and the electric field pattern is optimized ( Figure 3 ), so that the energy distribution and shape distribution of the plasma ball are improved, and the deposition area of ​​the plasma ball 15 on the diamond deposition substrate 14 is increased.

[0031] Specifically, the middle cavity 2 reflects microwaves and gathers microwave energy (electric field) directly above the diamond deposition substrate 14 .

[0032] Therefore, a chopped wave platform 21 is added directly above the diamond deposition substrate 14, and the position of the lower surface of the chopped wave platform 21 is adjusted to optimize the diameter of the chopped wave platform 21 so as to most effectively reflect microwaves and form a resonant wave between the deposition substrate 14 and the chopped wave platform 21, thereby exciting the mixed gas to form a plasma ball 5, ensuring that the deposition range of the plasma ball 15 is the entire large area of ​​the diamond deposition substrate 14. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the MPCVD dish-shaped chamber structure to expand the diamond deposition area;

[0034] Figure 2 Schematic diagram of the parameters of the MPCVD dish-shaped chamber to expand the diamond deposition area;

[0035] Figure 3 Electric field distribution diagram of the MPCVD dish-shaped cavity structure to expand the diamond deposition area.

[0036] 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-external 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, 19-mounting seat, 21-waveguide cutoff platform, 22-water cooling system; 27-sealing ring, 28-sample platform. DETAILED DESCRIPTION

[0037] The following schematic diagrams provide a more detailed description of the present invention's structure and method for expanding diamond deposition area using a disc-shaped MPCVD chamber. These schematic diagrams illustrate preferred embodiments of the present invention. It should be understood that those skilled in the art may modify the present invention described herein while still achieving its beneficial effects. Therefore, the following description should be understood as a general guideline for those skilled in the art and not as a limitation of the present invention.

[0038] The present invention mainly solves the problem of large-area diamond deposition. By optimizing traditional equipment, an MPCVD device that can achieve large-area diamond deposition is obtained. The improvement to the equipment mainly adds a microwave-reflecting chopper and optimizes the height and area of ​​the chopper to obtain a stable and high-energy microwave plasma ball, thereby obtaining an MPCVD device for large-area diamond deposition.

[0039] like Figures 1 to 3 , an MPCVD dish-shaped cavity structure for expanding diamond deposition area, comprising:

[0040] Bottom plate 5;

[0041] The housing 12 has its lower end surface fixed to the bottom plate 5 and an air hole 13 formed on its top. The housing 12 encloses an upper cavity 1 and a middle cavity 2 that are connected in sequence.

[0042] The upper cavity 1 is a resonant cavity;

[0043] The middle cavity 2 is used to introduce microwaves. The inner wall of the middle cavity 2 reflects the microwaves to feed them into the upper cavity 1. A diamond deposition substrate 14 is disposed therein and is placed on a sample platform 28.

[0044] The wave cutting platform 21 is used to reflect the microwave fed into the upper cavity 1 to form a resonant wave. The wave cutting platform 21 is located in the upper cavity 1 and above the diamond deposition substrate 14 .

[0045] The chopped wave platform 21 is placed concentrically with the diamond deposition substrate 14. By optimizing the area and optimal position of the chopped wave platform 21, the field pattern of the dish-shaped cavity is improved ( Figure 3 ), which increases the deposition area.

[0046] The chopping stage 21 is fixed to the mounting rod 19 .

[0047] The mounting rod 19 is mounted on the housing 12 and its height is adjustable. The mounting rod 19 is threadedly connected to the housing 12, and a water cooling system 22 is arranged therein.

[0048] like Figure 2 As shown, the height difference h2 between the height of the wave cutting platform 21 and the bottom plate 5 is: 110mm.

[0049] The lower surface of the chopping stage 21 has a diameter of 60 mm.

[0050] Optimize the backfield simulation Figure 3 .

[0051] Furthermore, a side surface of the wave cutting platform 21 facing the diamond deposition substrate 14 is a plane, on which uniformly distributed gas holes are provided, and the gas holes are blind holes.

[0052] According to the prior art: it also includes a lower cavity 3 for feeding 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;

[0053] The annular quartz microwave window 6 is fixed between the bottom plate 5 and the lower end surface of the water-cooling platform 4 .

[0054] The outer bottom surface of the bottom plate 5 is provided with a shell waveguide 11, which is sleeved on the outer water pipe 8, and the inner water pipe 16 and the central water pipe 9 are sleeved in sequence inside the outer water pipe 8;

[0055] 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 thereof is connected to the bottom plate 5 and the lower cavity 3;

[0056] 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.

[0057] The method for expanding the diamond deposition area of ​​an MPCVD dish-shaped cavity comprises the following steps:

[0058] Step 1: The microwaves are reflected by the inner wall of the middle cavity 2 and gathered above the diamond deposition substrate 14;

[0059] The microwave is then reflected at the chopping stage 21, forming a resonant wave between the deposition substrate 14 and the chopping stage 21;

[0060] At the same time, the mixed gas enters the upper cavity 1 through the air holes 13 of the shell 12;

[0061] Step 2: The resonant wave and the introduced mixed gas resonate to form a plasma ball 15 . The deposition range of the plasma ball 15 is the entire large-area diamond deposition substrate 14 .

[0062] The steps of forming the plasma ball 15 in MPCVD are as follows:

[0063] First, microwaves are fed in from below, converted into the middle cavity 2 by the antenna housing waveguide 11, reflected by the inner wall of the middle cavity 2, focused above the diamond deposition substrate 14, and then reflected at the wave cutting platform 21 to form a resonant wave.

[0064] Then, the resonant wave resonates with the introduced mixed gas. The mixed gas is mainly H2, and also includes CH4 and O2. The mixed gas is excited by microwaves to form a plasma ball, and under a specific vacuum environment, a diamond chemical deposition environment is formed.

[0065] Specifically:

[0066] The microwaves are fed into the outer shell waveguide 11 through the microwave feed port 10. The outer water pipe 8 inside the outer shell waveguide 11 also serves as a conversion antenna. The microwaves move upward along the outer wall of the outer water pipe 8, guiding the fed microwaves into the lower cavity 3. Then, the microwaves pass through the annular quartz window 6 into the middle cavity 2. After being reflected by the inner wall of the middle cavity 2, they form a resonant wave in the upper cavity 1. The upper cavity 1 is also called a resonant cavity, and a plasma ball 15 is subsequently formed here.

[0067] The gas enters the upper cavity 1 through the air holes 13 of the outer shell 12 .

[0068] The resonant wave resonates with the introduced mixed gas, and the gas forms a plasma ball 15 in the upper cavity 1. The plasma ball acts on the diamond deposition substrate 14 to perform chemical deposition to form polycrystalline or single crystal diamond.

[0069] In this embodiment, the plasma ball 15 deposits a polycrystalline diamond film with uniform thickness (thickness uniformity error within 10%) on a 4-inch diamond deposition substrate 14, and the thickness can reach between 0.3-1 mm.

[0070] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any person skilled in the art who, without departing from the scope of the present invention, makes any equivalent substitution, modification, or other changes to the technical solution and technical content disclosed in the present invention shall be deemed to be within the scope of the present invention and still fall within the scope of protection of the present invention.

Claims

1. An MPCVD disc-shaped cavity structure for enlarging diamond deposition area, 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; the outer shell (12) encloses an upper cavity (1) and a middle cavity (2) which are connected in sequence; The upper cavity (1) is a resonant cavity; The middle cavity (2) is used to introduce microwaves, and its inner wall reflects the microwaves to feed them into the upper cavity (1), in which a diamond deposition substrate (14) is arranged, and the diamond deposition substrate (14) is placed on a sample platform (28); and a wave cutting platform (21), used for reflecting the microwave fed into the upper cavity (1) to form a resonant wave, which is located in the upper cavity (1) and above the diamond deposition substrate (14); The chopping platform (21) is separated from the air hole (13) and is located below the air hole (13), and there is a gap between the chopping platform (21) and the upper cavity (1); The wave cutting platform (21) is fixed to a mounting rod (19), and the mounting rod (19) is mounted on the housing (12) and its height is adjustable.

2. The MPCVD disc-shaped cavity structure for enlarging diamond deposition area according to claim 1, characterized in that: The height difference h1 between the wave cutting platform (21) and the sample platform (28) is in the range of 50-75 mm; The area A of the lower surface of the wave cutting platform (21) is 50-100 mm in diameter.

3. The MPCVD disc-shaped cavity structure for enlarging diamond deposition area according to claim 1, characterized in that: The height difference h2 between the wave cutting platform (21) and the bottom plate (5) is in the range of 100-130 mm.

4. The MPCVD disc-shaped cavity structure for enlarging diamond deposition area according to claim 1, characterized in that: The side surface of the wave cutting platform (21) facing the diamond deposition substrate (14) is a plane, and uniformly distributed uniform air holes are provided on the plane.

5. The MPCVD disc-shaped cavity structure for enlarging diamond deposition area according to claim 1, characterized in that: A water cooling system (22) is arranged inside the mounting rod (19).

6. The MPCVD dish-shaped cavity structure for enlarging diamond deposition area according to claim 1, characterized in that: The mounting rod (19) is threadedly connected to the housing (12).

7. The MPCVD disc-shaped cavity structure for enlarging diamond deposition area according to claim 1, characterized in that: Also includes: 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); The annular quartz microwave window (6) is fixed between the bottom plate (5) and the lower end surface of the water-cooling platform (4).

8. The MPCVD disc-shaped cavity structure for enlarging diamond deposition area according to claim 7, 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.

9. A method for enlarging diamond deposition area by using a MPCVD dish-shaped cavity, based on the MPCVD dish-shaped cavity enlarging diamond deposition area structure according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1, microwaves are reflected by the inner wall of the middle cavity (2) and gathered above the diamond deposition substrate (14); The microwave is then reflected at the wave-cutting platform (21), forming a resonant wave between the deposition substrate (14) and the wave-cutting platform (21); At the same time, the mixed gas enters the upper cavity (1) through the air hole (13) of the outer shell (12); Step 2: The resonant wave and the introduced mixed gas resonate to form a plasma ball (15), and the deposition range of the plasma ball (15) is the entire large-area diamond deposition substrate (14).

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