Novel resonant cavity microwave plasma diamond deposition device

Abstract

The invention relates to a novel resonant cavity microwave plasma diamond deposition device, which comprises a cavity body, the invention relates to a high-power microwave oven, which comprises a cavity, a plurality of air inlets, a plurality of temperature measurement observation windows, a plurality of horizontal observation windows, a quartz glass ring, a water cooling table, a molybdenum substrate table, plasma, an antenna, a microwave feed-in port and a plurality of exhaust ports, wherein the central wall surface of the top of the cavity is a curved surface protruding towards the inside of the cavity; microwaves in a cavity are reflected to the position above a substrate table in a concentrated mode through the unique cavity shape of a resonant cavity, resonance is generated, the diameter of an excited plasma area suitable for diamond growth is not smaller than 4 inches, the difference between the highest temperature of the center of a diamond sheet growth area of the substrate table and the temperature of the edge of the diamond sheet growth area is small, and a plasma fireball is close to a cake shape. According to the device, under the input power larger than or equal to 9 kW, plasmas in a diamond growth area over the molybdenum substrate table in the cavity are concentrated and uniform.

Description

Technical Field

[0001] The present invention belongs to the technical field of diamond preparation, and particularly relates to a novel resonant cavity microwave plasma diamond deposition device. Background Art

[0002] Diamond has extreme physical and chemical properties and is known as the "king of materials". It is the hardest material in nature, with excellent properties such as extremely high thermal conductivity, low thermal expansion coefficient, wide bandgap, high breakdown field strength, excellent optical transparency, and high refractive index. Due to these properties, diamond is widely used in superhard tools, high-power heat dissipation devices, optical fields, semiconductor devices, and biomedical fields. The harsh conditions for the formation of natural diamond make it extremely rare, which to a certain extent limits the practical application of diamond. However, the rapid development of diamond synthesis technology has made these applications possible.

[0003] The commonly used methods for preparing diamond include: high temperature and high pressure method and chemical vapor deposition method. Due to the advantages of high purity, large size, and strong controllability of the diamond prepared by the chemical vapor deposition method, it is gradually replacing the high temperature and high pressure method as the mainstream preparation method. Among them, compared with other types of chemical vapor deposition methods, the advantage of microwave plasma chemical vapor deposition method (MPCVD) is that it can prepare large-area high-quality diamond. It generally uses metal materials as the cavity, and there is no incorporation of catalysts and impurities during the preparation of single crystal diamond, which improves the quality of diamond.

[0004] With the progress of MPCVD technology and the growth of market demand, the microwave input power has begun to increase. The deposition device has developed from the initial quartz tube type, quartz bell jar type, and cylindrical resonant cavity to non-cylindrical multi-mode, ellipsoidal resonant cavity, and butterfly cavity. The single machine power has been increased from several hundred watts to several thousand watts or even dozens of kilowatts.

[0005] Currently, the 915 MHz MPCVD can grow high-quality diamond on a substrate table with a diameter greater than 8 inches, but its power is as high as dozens of kilowatts. The high cost of equipment and high energy consumption restrict the popularization speed of this type of MPCVD. Currently, the MPCVD with a power of 10 kW can grow high-quality diamond on a substrate table with a diameter of 3 inches. Under the same conditions of using a 2-inch substrate table, although its diamond production efficiency is higher than that of a 6 kW cylindrical resonant cavity device, due to the structure of its resonant cavity and the influence of the edge effect of the plasma, the effective area of the plasma that can meet the diamond growth conditions cannot completely cover the 4-inch substrate table, resulting in a not very high cost performance.

[0006] Therefore, it has become an urgent problem to be solved to manufacture an MPCVD device with a power of 9 kW to 15 kW, which can grow high-quality diamond on a substrate table with a diameter of 4 inches or more and has a high diamond growth rate. Summary of the Invention

[0007] The object of the present invention is to provide a novel resonant cavity microwave plasma diamond deposition device with a simple structure and reasonable design in order to solve the above problems.

[0008] The present invention achieves the above object through the following technical solutions:

[0009] A novel resonant cavity microwave plasma diamond deposition device includes a cavity, and also includes a plurality of gas inlets, a plurality of temperature measurement and observation windows, a plurality of horizontal observation windows, a quartz glass ring, a water-cooled table, a molybdenum substrate table, plasma, an antenna, a microwave feeding port and a plurality of exhaust ports. The central wall surface at the top of the cavity is a curved surface protruding towards the inside of the cavity. The side upper wall surface of the cavity is a frustum of a right circular cone inclined towards the inside of the cavity. The side middle wall surface of the cavity is a cylindrical wall surface. The side lower wall surface of the cavity is an inverted frustum of a right circular cone. The curved surface of the central wall surface at the top is a curved surface obtained by rotating a characteristic curve around the central axis of the cavity for one week. The curved surface of the central wall surface at the top is connected to the side upper wall surface through an annular wall surface.

[0010] As a further optimized scheme of the present invention, the included angle α between the side upper wall surface and the bottom plane of the cavity ranges from 30° to 55°, and the included angle β between the side lower wall surface and the bottom plane of the cavity ranges from 35° to 65°.

[0011] As a further optimized scheme of the present invention, a plurality of the gas inlets are opened on the annular wall surface at the top of the cavity. A plurality of the temperature measurement and observation windows and a plurality of the horizontal observation windows are all arranged on the side upper wall surface of the cavity. The quartz glass ring, the water-cooled table, the molybdenum substrate table and the plasma are all arranged inside the cavity. The antenna and the quartz glass ring are fixedly arranged at the bottom inside the cavity. The water-cooled table is located on the top of the antenna and the quartz glass ring. The molybdenum substrate table is located on the top of the water-cooled table. The plasma is located on the top of the substrate table with the spherical surface facing upwards. The microwave feeding port is arranged at the bottom of the cavity. A plurality of the exhaust ports are located at the bottom of the cavity. The plurality of gas inlets, the plurality of the temperature measurement and observation windows, the horizontal observation windows and the exhaust ports are all circumferentially distributed around the central axis of the cavity.

[0012] As a further optimized scheme of the present invention, the antenna has an inverted frustum of a right circular cone structure.

[0013] As a further optimized solution of the present invention, a plurality of the air inlets form an angle with the bottom plane of the cavity, and a plurality of the temperature measurement and observation windows form an angle with the bottom plane of the cavity.

[0014] As a further optimized solution of the present invention, the thickness range of the quartz glass ring is 5 mm - 10 mm.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. The device has a simple and compact structure, is easy to process and manufacture, and is mainly composed of two regular cones, a section of cylinder and a curved surface protruding towards the inside of the cavity. The overall shape is beautiful and simple;

[0017] 2. The curved surface protruding towards the inside of the cavity at the top of the cavity is a surface obtained by rotating a characteristic curve around the central axis of the cavity. The characteristic curve can include multiple line segments, parabolas, elliptical curves, circular curves or curves composed of two or more of them. By using different surfaces, the plasma morphology and coverage area can be effectively adjusted to meet the diamond growth requirements of different diameter substrate tables;

[0018] 3. The unique shape of the resonant cavity concentrates the microwaves in the cavity and reflects them above the substrate table, generating resonance. The diameter of the plasma region suitable for diamond growth excited is more than 4 inches. The plasma is uniform within 4 inches and there is no obvious edge effect. The temperature difference between the center and the edge of the diamond growth region on the 4-inch substrate table is less than 70°C. The plasma fireball is close to a round cake shape. When the input power is ≥9 kW, the plasma in the diamond growth region directly above the molybdenum substrate table in the cavity is concentrated and uniform;

[0019] 4. The bottom of the plasma generated by the device is flat, and the actual plasma coverage area is larger than the area of the molybdenum substrate table, making the overall temperature of the molybdenum substrate table more consistent, with high diamond growth quality and fast growth rate;

[0020] 5. The cavity adopts an overall water-cooling structure to avoid the problem of overheating of the cavity during high-power operation of the equipment;

[0021] 6. Inside the cavity, the quartz glass ring is fixedly arranged under the water-cooling table, and the water-cooling table isolates it from the plasma discharge area, effectively avoiding the situation of overheating and fragmentation of the quartz glass ring caused by direct thermal radiation and etching by the plasma;

[0022] 7. The antenna with an inverted round table surface structure can effectively guide the microwave transmission direction, facilitate the reflection of microwaves into the cavity, and combine with the cavity structure to converge them to the plasma excitation area above the molybdenum substrate table;

[0023] 8. Multiple air inlets are circumferentially distributed around the vertical central axis of the cavity and form a certain angle with the horizontal plane of the cavity. This angle can cause the process gas entering the cavity through the multiple air inlets to converge in the plasma region inside the cavity, making the air intake more uniform, promoting the gas exchange inside and outside the plasma, and being more conducive to the high-quality and uniform growth of diamond.

[0024] 9. By setting multiple temperature measurement and observation windows that are circumferentially distributed around the vertical central axis of the cavity, and the temperature measurement and observation windows form a certain angle with the horizontal plane of the cavity. Through the cooperative observation of the multiple temperature measurement and observation windows, the molybdenum substrate table can be covered without dead angles, providing a more comprehensive temperature observation range.

[0025] 10. Multiple exhaust ports are opened at the bottom of the cavity and are circumferentially distributed around the central axis of the cavity, enabling the gas in the cavity to be discharged evenly, greatly reducing the disturbance of the gas flow during discharge to the diamond located on the molybdenum substrate table.

[0026] 11. This equipment can grow high-quality diamond on a substrate table with a diameter of 4 inches or more under the condition of a microwave input power of 9KW - 15kW. Description of the Drawings

[0027] Figure 1 It is the overall device structure diagram of the present invention;

[0028] Figure 2 It is the schematic diagram of the cavity shape elements of the present invention;

[0029] Figure 3 It is the cross-sectional structure diagram of the complete cavity of the present invention;

[0030] Figure 4 It is the axonometric view of the appearance of the cavity of the present invention;

[0031] Figure 5 It is the diagram of the electric field distribution inside the cavity of the present invention;

[0032] Figure 6 It is the diagram of the diamond growth state and plasma state photographed from the horizontal observation window towards the front of the molybdenum substrate table of the present invention;

[0033] Figure 7 It is the diagram of the diamond growth state and plasma state photographed from the horizontal observation window towards one side edge of the molybdenum substrate table of the present invention;

[0034] Figure 8 It is the diagram of the diamond growth state and plasma state photographed from the horizontal observation window towards the other side edge of the molybdenum substrate table of the present invention;

[0035] Figure 9 It is the diagram of the diamond growth state photographed from the temperature measurement and observation window on the cavity of the present invention.

[0036] In the figure: 1. Cavity; 2. Air inlet; 3. Temperature measurement and observation window; 4. Horizontal observation window; 5. Quartz glass ring; 6. Water-cooled table; 7. Molybdenum substrate table; 8. Plasma; 9. Antenna; 10. Microwave feeding port; 11. Exhaust port; 12. Top center wall surface; 13. Circular wall surface; 14. Side upper wall surface; 15. Side middle wall surface; 16. Side lower wall surface; 17. Inverted truncated cone surface. Detailed implementation manners

[0037] The present application will be further described in detail below with reference to the accompanying drawings. It is necessary to point out here that the following specific implementation manners are only used to further illustrate the present application and cannot be construed as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0038] Embodiment

[0039] As Figure 1 - Figure 4 shown, a novel resonant cavity microwave plasma diamond deposition device includes a cavity 1. The top center wall surface 12 of the cavity 1 is a curved surface protruding towards the inside of the cavity 1. The side upper wall surface 14 of the cavity 1 is a regular truncated cone surface inclined towards the inside of the cavity 1. The side middle wall surface 15 of the cavity 1 is a cylindrical wall surface. The side lower wall surface 16 of the cavity 1 is an inverted truncated cone surface. The curved surface of the top center wall surface 12 of the cavity 1 is a curved surface obtained by rotating a characteristic curve around the central axis of the cavity 1 for one week. The characteristic curve can include multiple line segments, parabolas, elliptical curves, regular circular curves, or a smooth curve composed of two or more of them. The spherical surface is connected to the side upper wall surface 14 through the circular wall surface 13;

[0040] And the included angle α between the side upper wall surface 14 and the bottom plane of the cavity 1 ranges from 30° to 55°, and the included angle β between the side lower wall surface 16 and the bottom plane of the cavity 1 ranges from 35° to 65°;

[0041] It also includes a plurality of air inlets 2. The plurality of air inlets 2 are located on the circular wall surface 13 at the top of the cavity 1 for users to introduce gas into the cavity 1;

[0042] A plurality of temperature measurement and observation windows 3 located on the side upper wall surface 14 of the cavity 1. By setting a plurality of temperature measurement and observation windows 3 for cooperative observation, the molybdenum substrate table can be covered without dead angles, providing a more comprehensive temperature observation range;

[0043] A plurality of horizontal observation windows 4. The plurality of horizontal observation windows 4 are located on the side upper wall surface 14 of the cavity 1, facilitating the observation of the growth condition of diamonds;

[0044] A quartz glass ring 5, a water-cooling table 6, a molybdenum substrate table 7, a plasma 8, and an antenna 9 are arranged inside the cavity 1. The antenna 9 and the quartz glass ring 5 are fixedly arranged at the bottom inside the cavity 1. The water-cooling table 6 is located above the antenna 9 and the quartz glass ring 5. The molybdenum substrate table 7 is located above the water-cooling table 6. The plasma 8 is located above the substrate table 7 with its spherical surface facing upward.

[0045] A microwave feeding port 10 located at the bottom position of the cavity 1 and an exhaust port 11 located at the bottom position of the cavity 1. Moreover, a plurality of gas inlet ports 2, a plurality of temperature measurement and observation windows 3, a plurality of horizontal observation windows 4, and a plurality of exhaust ports 11 are all circumferentially distributed around the central axis of the cavity 1.

[0046] The antenna 9 has a structure of an inverted truncated cone surface 17, which can effectively guide the microwave transmission direction and reflect the microwave into the cavity 1. Combining with the internal structure of the cavity 1, the microwave is converged on the excitation region of the plasma 8 above the molybdenum substrate table 7.

[0047] The plurality of gas inlet ports 2 form a certain angle with the horizontal plane of the cavity 1, and this angle can make the process gas entering the cavity 1 through the plurality of gas inlet ports 2 converge on the excitation region of the plasma 8 inside the cavity 1.

[0048] The plurality of temperature measurement and observation windows 3 form a certain angle with the horizontal plane of the cavity 1, enabling the staff to observe without dead angles through the cooperation of the plurality of temperature measurement and observation windows 3, covering the molybdenum substrate table 7 and providing a more comprehensive temperature observation range.

[0049] The thickness of the quartz glass ring 5 is 5 mm - 10 mm, which can ensure sufficient mechanical strength and vacuum sealing reliability without affecting microwave transmission.

[0050] It should be noted that for this new type of resonant cavity microwave plasma diamond deposition device, the cavity 1 is installed on an external device. After powering on the device, the water-cooling circulation system is turned on, and then the cavity 1 is opened. The molybdenum substrate table 7 containing diamond is placed on the water-cooling table 6 inside the cavity 1, and the cavity 1 is closed. Then, the cavity 1 is evacuated to 5 Pa by an external vacuum pump, and hydrogen is introduced. After the pressure inside the cavity 1 is stable, the 2.45 GHz microwave source is started. The microwave enters the cavity 1 from the microwave feeding port 10. The high-intensity electric field generated by the microwave excites a plasma 8 above the molybdenum substrate table 7. In a pure hydrogen state, the internal pressure of the cavity 1 and the power of the microwave source are gradually increased until the diamond deposition conditions are reached. After the temperature rise is completed, the process gas is introduced. The growth rate of diamond can be controlled by adjusting the proportion of the process gas, thereby balancing the quality and growth rate of diamond, achieving the purpose of rapidly growing high-quality diamond within a certain reasonable range. The thickness of the grown diamond depends on the deposition time, and the state of the plasma 8 and diamond can be judged through the temperature measurement and observation windows 3 and the horizontal observation windows 4.

[0051] The observation results are as follows Figures 5 - 9 as shown below: Figure 5 Figure 5 is the electric field distribution during diamond deposition inside the cavity 1 of this device. When diamond deposition is carried out, the growth state of diamond and the plasma can be photographed through one of the horizontal observation windows 4 towards the front of the molybdenum substrate table 7, such as Figure 6 as shown below. The growth state of diamond and the plasma state photographed through one of the horizontal observation windows 4 towards one side edge of the molybdenum substrate table 7 are as Figure 7 shown below. The growth state of diamond and the plasma state photographed from the horizontal observation window 4 towards the other side edge of the molybdenum substrate table 7 are as Figure 8 shown below. The growth state of diamond photographed from the temperature measurement observation window 3 on the cavity 1 is as Figure 9 shown below;

[0052] According to the observation results, it can be concluded that the bottom of the plasma generated by this device is flat, and the actual coverage area of the plasma is larger than the area of the 4-inch molybdenum substrate table used in this example, making the overall temperature consistency of the molybdenum substrate table better, the diamond growth quality high, and the growth rate fast.

[0053] When the diamond deposition process ends, gradually reduce the internal pressure of the cavity 1 and the power of the microwave source until the microwave source is turned off and the process gas supply is stopped. Then, restore the inside of the cavity to atmospheric pressure, and the cavity 1 can be opened to take out the diamond.

[0054] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A novel resonant cavity microwave plasma diamond deposition device, comprising a cavity (1), characterized in that: It also includes a plurality of air inlets (2), a plurality of temperature measurement observation windows (3), a plurality of horizontal observation windows (4), a quartz glass ring (5), a water-cooling table (6), a molybdenum substrate table (7), a plasma (8), an antenna (9), a microwave feeding port (10) and a plurality of exhaust ports (11). The top central wall surface (12) of the cavity (1) is a curved surface protruding towards the interior of the cavity. The upper side wall surface (14) of the cavity (1) is a frustum of a right circular cone inclined towards the interior of the cavity. The middle side wall surface (15) of the cavity (1) is a cylindrical wall surface. The lower side wall surface (16) of the cavity (1) is an inverted frustum of a right circular cone. The curved surface of the top central wall surface (12) is a curved surface obtained by rotating a characteristic curve around the central axis of the cavity for one week. The curved surface of the top central wall surface (12) is connected to the upper side wall surface (14) through an annular wall surface (13).

2. A novel resonant cavity microwave plasma diamond deposition device according to claim 1, wherein: The angle α between the upper side wall surface (14) and the bottom plane of the cavity (1) ranges from 30° to 55°. The angle β between the lower side wall surface (16) and the bottom plane of the cavity (1) ranges from 35° to 65°.

3. A novel resonant cavity microwave plasma diamond deposition device according to claim 1, characterized in that: A plurality of the air inlets (2) are opened on the annular wall surface (13) at the top of the cavity (1). A plurality of the temperature measurement observation windows (3) and a plurality of the horizontal observation windows (4) are both arranged on the upper side wall surface (14) of the cavity (1). The quartz glass ring (5), the water-cooling table (6), the molybdenum substrate table (7) and the plasma (8) are all arranged inside the cavity (1). The antenna (9) and the quartz glass ring (5) are fixedly arranged at the bottom inside the cavity (1). The water-cooling table (6) is located above the antenna (9) and the quartz glass ring (5). The molybdenum substrate table (7) is located above the water-cooling table (6). The plasma (8) is located above the substrate table (7) with the spherical surface facing upwards. The microwave feeding port (10) is arranged at the bottom of the cavity (1). A plurality of the exhaust ports (11) are located at the bottom of the cavity (1). The plurality of air inlets (2), the plurality of the temperature measurement observation windows (3), the horizontal observation windows (4) and the exhaust ports (11) are all circumferentially distributed around the central axis of the cavity (1).

4. A novel resonant cavity microwave plasma diamond deposition device according to claim 1, characterized in that: The antenna (9) has a structure of an inverted frustum of a right circular cone (17).

5. A novel resonant cavity microwave plasma diamond deposition device according to claim 4, characterized in that: A plurality of the air inlets (2) form an angle with the bottom plane of the cavity (1). A plurality of the temperature measurement observation windows (3) form an angle with the bottom plane of the cavity (1).

6. A novel resonant cavity microwave plasma diamond deposition device according to claim 1, characterized in that: The thickness range of the quartz glass ring (5) is 5 mm - 10 mm.

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