Microwave plasma chemical vapor deposition device based on quasi-optical mirror surface type 915MHz

Abstract

The invention discloses a microwave plasma chemical vapor deposition device based on a quasi-optical mirror surface type 915MHz, and a quasi-optical mirror surface type microwave resonant cavity utilizes good characteristics of a parabolic reflector and an elliptical reflector in a quasi-optical mode converter on microwave focusing and convergence. Compared with an existing ellipsoid type microwave resonant cavity, the ellipsoid type microwave resonant cavity is simpler in structure and smaller in size, and the problems that an ellipsoid type MPCVD resonant cavity is difficult to machine, complex in structure and large in size are effectively solved. Meanwhile, the quasi-optical mirror surface type microwave resonant cavity can remarkably improve the coupling efficiency of microwave energy in the operation process, ensure the stability of input power, the temperature in the cavity and the air pressure, and improve the cooling effect of the inner cavity wall and the sample table. Besides, the quasi-optical mirror surface type microwave resonant cavity is simple and convenient to design and process, can realize efficient microwave energy coupling under the conditions of high power and high air pressure, and can maintain stable operation at set temperature and air pressure for a long time.

Description

Technical Field

[0001] The invention belongs to the technical field of diamond material deposition and growth equipment, and in particular, relates to a 915MHz microwave plasma chemical vapor deposition device based on a quasi-mirror type. Background Art

[0002] Microwave plasma chemical vapor deposition (MPCVD) represents a widely adopted technology for the production of high-quality diamond materials. This method is capable of producing a variety of qualities of diamond single crystal and multicrystalline materials, including tool grade, heat sink grade, gem grade, optical grade and electronic grade diamond.

[0003] The core component of the MPCVD system is the microwave resonant cavity, which is usually made of metal material and is used to reflect the input microwave energy and ultimately establish a high-intensity microwave electric field in the sample platform area. The key is that a properly designed microwave resonant cavity can efficiently transmit microwave energy under a wide range of process conditions, while avoiding abnormal excitation of secondary plasma and etching of the cavity and microwave window. This design principle is a key factor in ensuring the production of high-quality diamond materials. However, it should be pointed out that microwave resonant cavities with different structural designs will have a significant impact on the microwave resonance effect. In addition, the design must also meet the growth process requirements of diamond materials, including stable operation at higher power and gas pressure. Therefore, a reasonable microwave resonant cavity design is crucial to ensure the controllable preparation of diamond materials.

[0004] Around 1997, the Fraunhofer Institute in Germany proposed the concept of an ellipsoidal resonant cavity MPCVD device. The design of this device is similar to that of a quartz bell-shaped MPCVD device, consisting of a metal resonant cavity and a quartz bell-shaped device, and using a coaxial antenna-type mode converter for microwave mode switching and excitation.

[0005] In the ellipsoidal microwave resonant cavity, the radiation point of the microwave antenna is located at the upper focus of the ellipsoid, while the position of the lower focus of the ellipsoid is the deposition platform of the diamond film. This design cleverly utilizes the focal convergence principle of the ellipsoid, so that the microwave is emitted from the antenna at the upper focus of the ellipsoid and then converges at the deposition position of the diamond film. Therefore, this device is said to have excellent microwave electric field focusing performance, which can effectively excite gas and generate high-density plasma.

[0006] However, the disadvantages of the ellipsoidal microwave resonant cavity are also prominent. Because of its complex structure, it is difficult to design and process, and the coaxial microwave antenna and the sample platform are located at the double focus of the ellipsoid, which requires precise positioning. Summary of the invention

[0007] The present invention provides a 915 MHz microwave plasma chemical vapor deposition device based on a collimated mirror type to solve the problems existing in the above-mentioned background technology.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present invention is: a quasi-mirror type 915MHz microwave plasma chemical vapor deposition device, including a microwave generator, a rectangular waveguide, a microwave antenna, a short-circuit piston, a circular waveguide, a quasi-mirror type microwave resonant cavity, a quartz cover, an exhaust system, a sample platform and an air intake system, one end of the rectangular waveguide is connected to the microwave generator, and the other end of the rectangular waveguide is connected to the short-circuit piston. A quasi-mirror type microwave resonant cavity is arranged at the lower part of the rectangular waveguide, and the rectangular waveguide and the quasi-mirror type microwave resonant cavity are connected through the circular waveguide. One end of the microwave antenna is fixed in the rectangular waveguide, and the other end of the microwave antenna passes through the circular waveguide and extends into the quasi-mirror type microwave resonant cavity. The quartz cover is connected to the bottom of the quasi-mirror type microwave resonant cavity. The sample platform is arranged inside the quartz cover and connected to the bottom of the quasi-mirror type microwave resonant cavity. The exhaust system and the air intake system are respectively connected to the quasi-mirror type microwave resonant cavity through pipelines.

[0009] Preferably, a cavity heat dissipation water inlet is provided on the upper side of the outer cavity wall of the quasi-mirror type microwave resonant cavity, and a cavity heat dissipation water outlet is provided on the lower side; a sample platform cooling water inlet and a sample platform cooling water outlet are respectively provided in the middle of the lower end of the sample platform.

[0010] Preferably, a three-pin tuner is provided on one side of the microwave generator in the rectangular waveguide.

[0011] Preferably, the outer cavity wall of the quasi-mirror type microwave resonant cavity is cylindrical; and the inner cavity wall of the quasi-mirror type microwave resonant cavity is ellipsoidal.

[0012] Preferably, the inner cavity wall of the quasi-optical mirror type microwave resonant cavity is composed of a parabolic reflector and an elliptical reflector in a quasi-optical mode converter.

[0013] Preferably, the material of the outer cavity wall of the quasi-mirror type microwave resonant cavity is stainless steel; the material of the parabolic reflector and the elliptical reflector of the inner cavity wall of the quasi-mirror type microwave resonant cavity is oxygen-free copper.

[0014] Preferably, a hollow structure is formed between the outer cavity wall and the inner cavity wall of the quasi-mirror type microwave resonant cavity, and the hollow structure is filled with cooling water through a cavity heat dissipation water inlet and a cavity heat dissipation water outlet.

[0015] Preferably, the distance between the bottom of the microwave antenna and the sample platform is 343 mm.

[0016] Preferably, the pumping system is composed of a rotary vane mechanical pump and a molecular pump; the air intake system provides gas raw materials for preparing diamond materials, and the gas raw materials include hydrogen and methane.

[0017] Preferably, the gas raw material also includes one or more mixed gases of nitrogen, oxygen and argon.

[0018] The beneficial effects of adopting the above technical solution are:

[0019] 1. The quasi-mirror-type 915MHz microwave plasma chemical vapor deposition device of the present invention, the quasi-mirror-type microwave resonant cavity, utilizes the good characteristics of the parabolic reflector and the elliptical reflector in the quasi-optical mode converter to focus and converge microwaves, and has a simple structure, so as to solve the problems of the existing ellipsoidal resonant cavity, such as the difficulty in processing, the complex structure, the low microwave energy coupling efficiency during the operation of the device, the difficulty in maintaining the stability of the input power and the temperature and pressure in the cavity, and the insufficient cooling of the inner cavity wall and the sample stage.

[0020] 2. The quasi-mirror type 915MHz microwave plasma chemical vapor deposition device of the present invention has the characteristics of simple structure, easy design and processing. Compared with the ellipsoidal resonant cavity, the device is significantly smaller in size and no longer needs to strictly control the precise position of the dual focus. This enables the device to achieve efficient coupling of microwave energy under high power and high pressure conditions, and can maintain stable operation for a long time at the set temperature and pressure.

[0021] 3. The quasi-mirror-type 915MHz microwave plasma chemical vapor deposition device of the present invention can realize efficient coupling of microwave energy within the power range of 15 to 75kW and the gas pressure range of 10 to 40kPa, meeting the process requirements of continuous growth of diamond film for 100 to 800h. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of a 915MHz microwave plasma chemical vapor deposition device based on a quasi-mirror type;

[0023] Figure 2 It is a schematic diagram of the structure of a quasi-mirror type microwave resonant cavity based on a quasi-mirror type 915MHz microwave plasma chemical vapor deposition device;

[0024] Figure 3 This is the internal electric field distribution diagram of the quasi-mirror microwave resonant cavity based on the quasi-mirror 915MHz microwave plasma chemical vapor deposition device;

[0025] Figure 4 This is a diagram of the internal plasma electron density distribution of a quasi-mirror microwave resonant cavity based on a quasi-mirror 915MHz microwave plasma chemical vapor deposition device;

[0026] in:

[0027] 1. Microwave power supply; 2. Three-pin tuner; 3. Rectangular waveguide; 4. Microwave antenna; 5. Short-circuit piston; 6. Circular waveguide; 7. Parabolic reflector; 8. Elliptical reflector; 9. Quartz cover; 10. Exhaust system; 11. Sample platform; 12. Air intake system; 13. Quasi-mirror type microwave resonant cavity; 14. Cavity heat dissipation water injection port; 15. Cavity heat dissipation water outlet; 16. Sample platform cooling water injection port; 17. Sample platform cooling water outlet. DETAILED DESCRIPTION

[0028] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0029] like Figures 1 to 4 As shown, the present invention is a 915MHz microwave plasma chemical vapor deposition device based on a quasi-optical mirror. The quasi-optical mirror microwave resonant cavity utilizes the good characteristics of the parabolic reflector and the elliptical reflector in the quasi-optical mode converter to focus and converge microwaves, and has a simple structure. It solves the problems of the existing ellipsoidal MPCVD resonant cavity, such as the difficulty in processing, the complex structure, the low microwave energy coupling efficiency during the operation of the device, the difficulty in maintaining the stability of the input power and the temperature and pressure in the cavity, and the insufficient cooling of the inner cavity wall and the sample stage. It has a simple structure, is easy to design and process, can ensure the efficient coupling of microwave energy at high power and pressure, and can maintain the set temperature and pressure for a long time.

[0030] Specifically, Figures 1 to 4 As shown, it includes a microwave generator 1, a rectangular waveguide 3, a microwave antenna 4, a short-circuit piston 5, a circular waveguide 6, a quasi-mirror type microwave resonant cavity 13, a quartz cover 9, an exhaust system 10, a sample platform 11 and an air intake system 12, one end of the rectangular waveguide 3 is connected to the microwave generator 1, and the other end of the rectangular waveguide 3 is connected to the short-circuit piston 5. The lower part of the rectangular waveguide 3 is provided with a quasi-mirror type microwave resonant cavity 13, and the rectangular waveguide 3 is connected to the quasi-mirror type microwave resonant cavity 13 through the circular waveguide 6. One end of the microwave antenna 4 is fixed in the rectangular waveguide 3. The other end of the microwave antenna 4 passes through the circular waveguide 6 and extends into the quasi-mirror type microwave resonant cavity 13, and the insertion depth of the microwave antenna 4 can be adjusted. The quartz cover 9 is connected to the bottom of the quasi-mirror type microwave resonant cavity 13. The sample platform 11 is arranged inside the quartz cover 9 and connected to the bottom of the quasi-mirror type microwave resonant cavity 13. The sample platform 11 can be height-adjusted in the axial direction, and the allowable adjustment distance is 0 to 25 mm. The exhaust system 10 and the air intake system 12 are respectively connected to the quasi-mirror type microwave resonant cavity 13 through pipelines.

[0031] A cavity heat dissipation water inlet 14 is provided on the upper side of the outer cavity wall of the quasi-mirror type microwave resonant cavity 13 to inject cooling water, and a cavity heat dissipation water outlet 15 is provided on the lower side to discharge cooling water, thereby achieving the effect of heat dissipation for the quasi-mirror type microwave resonant cavity 13; a sample platform cooling water inlet 16 and a sample platform cooling water outlet 17 are respectively provided in the middle of the lower end of the sample platform 11.

[0032] A three-pin tuner 2 is provided on one side of the microwave generator 1 in the rectangular waveguide 3 .

[0033] The outer cavity wall of the quasi-mirror type microwave resonant cavity 13 is cylindrical; the inner cavity wall of the quasi-mirror type microwave resonant cavity 13 is ellipsoidal.

[0034] The inner cavity wall of the quasi-optical mirror type microwave resonant cavity 13 is composed of a parabolic reflector 7 and an elliptical reflector 8 in a quasi-optical mode converter; compared with an ellipsoidal microwave resonant cavity, the quasi-optical mirror type microwave resonant cavity 13 has a simpler structure, lower processing and manufacturing difficulty, and has a good focusing and converging effect on microwaves.

[0035] The material of the outer cavity wall of the quasi-mirror type microwave resonant cavity 13 is stainless steel; the material of the parabolic reflector 7 and the elliptical reflector 8 of the inner cavity wall of the quasi-mirror type microwave resonant cavity 13 is oxygen-free copper.

[0036] The quasi-mirror type microwave resonant cavity 13 has a hollow structure between the outer cavity wall and the inner cavity wall, and the hollow structure is filled with cooling water through the cavity heat dissipation water inlet 14 and the cavity heat dissipation water outlet 15 .

[0037] The distance between the bottom of the microwave antenna 4 and the sample platform 11 is 343 mm.

[0038] The pumping system 10 is composed of a rotary vane mechanical pump and a molecular pump; the air intake system 12 provides gas raw materials for preparing diamond materials, and the gas raw materials include hydrogen and methane.

[0039] The gas raw material also includes one or more mixed gases of nitrogen, oxygen and argon.

[0040] The specific working method is described below with specific embodiments:

[0041] Embodiment 1:

[0042] The present invention is based on a quasi-mirror type 915MHz microwave plasma chemical vapor deposition device, comprising a microwave generator 1, a rectangular waveguide 3, a microwave antenna 4, a short-circuit piston 5, a circular waveguide 6, a quasi-mirror type microwave resonant cavity 13, a quartz cover 9, an exhaust system 10, a sample platform 11 and an air intake system 12, wherein one end of the rectangular waveguide 3 is connected to the microwave generator 1, and the other end of the rectangular waveguide 3 is connected to the short-circuit piston 5, a microwave power supply 1 is used to output microwave energy, a three-pin tuner 2 is arranged on one side of the microwave power supply 1 in the rectangular waveguide 3, and the three-pin tuner 2 and the rectangular waveguide 3 are used for microwave transmission; a quasi-mirror type microwave resonant cavity 13 is arranged at the lower part of the rectangular waveguide 3, the rectangular waveguide 3 is connected to the quasi-mirror type microwave resonant cavity 13 through the circular waveguide 6, one end of the microwave antenna 4 is fixed on the rectangular waveguide 3, the other end of the microwave antenna 4 passes through the circular waveguide 6 and extends into the quasi-mirror type microwave resonant cavity 13, and the insertion depth of the microwave antenna 4 can be adjusted, the quartz cover 9 is connected to the bottom of the quasi-mirror type microwave resonant cavity 13, the sample platform 11 is arranged inside the quartz cover 9, and is connected to the bottom of the quasi-mirror type microwave resonant cavity 13, the quartz cover 9 is a bell-shaped part made of high-purity quartz, which is used to maintain the vacuum degree in the quasi-mirror type microwave resonant cavity 13 and also serves as a microwave input window, the quartz cover 9 has a diameter of 150 to 330 mm and a height of 150 to 230 mm; the sample platform 11 can be adjusted in height in the axial direction, and the allowable adjustment distance is 0 to 25 mm, and the exhaust system 10 and the air intake system 12 are respectively connected to the quasi-mirror type microwave resonant cavity 13 through pipelines.

[0043] like Figure 1 and Figure 2 The present invention provides a schematic structural diagram of a quasi-mirror-type 915MHz microwave plasma chemical vapor deposition device and a schematic structural diagram of a quasi-mirror-type microwave resonant cavity. The quasi-mirror-type microwave resonant cavity 13 utilizes the focusing and converging characteristics of the parabolic reflector 7 and the elliptical reflector 8 in the quasi-optical mode converter on microwaves. The bottom of the microwave antenna 4 is 343mm away from the sample platform 11. Figure 3 It can be clearly seen that the electric field intensity is the largest in the area above the sample platform 11, so high-density plasma can be excited above the sample platform 11. It also shows that the cavity designed in the present invention has a high microwave energy coupling efficiency, that is, plasma is only excited at the required position, no additional energy loss is generated, and the quasi-mirror type 915MHz microwave plasma chemical vapor deposition device can be ensured to operate stably. Figure 4 : is the distribution diagram of plasma above the sample platform. It can be clearly seen that the plasma completely wraps the sample platform 11, which is beneficial for the preparation of diamond materials.

[0044] Embodiment 2:

[0045] On the basis of Example 1, the outer cavity wall of the quasi-mirror type microwave resonant cavity 13 is cylindrical; the inner cavity wall of the quasi-mirror type microwave resonant cavity 13 is ellipsoidal. The inner cavity wall of the quasi-mirror type microwave resonant cavity 13 is composed of a parabolic reflector 7 and an ellipsoidal reflector 8 in a quasi-optical mode converter; compared with the ellipsoidal microwave resonant cavity, the quasi-mirror type microwave resonant cavity 13 has a simple structure, low difficulty in processing and manufacturing, and has a good focusing and converging effect on microwaves. The material of the outer cavity wall of the quasi-mirror type microwave resonant cavity 13 is stainless steel; the material of the parabolic reflector 7 and the ellipsoidal reflector 8 of the inner cavity wall of the quasi-mirror type microwave resonant cavity 13 is oxygen-free copper. There is a hollow structure between the outer cavity wall and the inner cavity wall of the quasi-mirror type microwave resonant cavity 13, and the hollow structure is filled with cooling water through the cavity heat dissipation water inlet 14 and the cavity heat dissipation water outlet 15.

[0046] The substrate material required for preparing diamond material is placed above the sample platform 11, and its top diameter is 80 to 216 mm. The microwave electric field resonates here to excite plasma and realize the deposition and growth of diamond material. The air intake system 12 and the exhaust system 10 are connected to the quasi-mirror microwave resonant cavity 13 through pipelines respectively.

[0047] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. Based on the 915MHz microwave plasma chemical vapor deposition device with quasi-mirror surface, it is characterized by: The invention comprises a microwave generator (1), a rectangular waveguide (3), a microwave antenna (4), a short-circuit piston (5), a circular waveguide (6), a quasi-mirror type microwave resonant cavity (13), a quartz cover (9), an exhaust system (10), a sample platform (11) and an air intake system (12); one end of the rectangular waveguide (3) is connected to the microwave generator (1), the other end of the rectangular waveguide (3) is connected to the short-circuit piston (5), a quasi-mirror type microwave resonant cavity (13) is provided at the bottom of the rectangular waveguide (3), and the rectangular waveguide (3) and the quasi-mirror type microwave resonant cavity (13) are connected via a The circular waveguide (6) is connected, one end of the microwave antenna (4) is fixed in the rectangular waveguide (3), the other end of the microwave antenna (4) passes through the circular waveguide (6) and extends into the quasi-mirror type microwave resonant cavity (13), the quartz cover (9) is connected to the bottom of the quasi-mirror type microwave resonant cavity (13), the sample platform (11) is arranged inside the quartz cover (9) and connected to the bottom of the quasi-mirror type microwave resonant cavity (13), and the exhaust system (10) and the intake system (12) are respectively connected to the quasi-mirror type microwave resonant cavity (13) through pipelines.

2. The 915MHz microwave plasma chemical vapor deposition device based on the collimated mirror type according to claim 1 is characterized in that: The upper side of the outer cavity wall of the quasi-mirror type microwave resonant cavity (13) is provided with a cavity heat dissipation water injection port (14), and the lower side is provided with a cavity heat dissipation water outlet (15); the lower middle of the sample platform (11) is provided with a sample platform cooling water injection port (16) and a sample platform cooling water outlet (17).

3. The 915MHz microwave plasma chemical vapor deposition device based on the collimated mirror type according to claim 1 is characterized in that: A three-pin tuner (2) is provided on one side of the microwave generator (1) in the rectangular waveguide (3).

4. The 915MHz microwave plasma chemical vapor deposition device based on the collimated mirror type according to claim 1 is characterized in that: The outer cavity wall of the quasi-mirror type microwave resonant cavity (13) is cylindrical; and the inner cavity wall of the quasi-mirror type microwave resonant cavity (13) is ellipsoidal.

5. The 915MHz microwave plasma chemical vapor deposition device based on the collimated mirror type according to claim 1 is characterized in that: The inner cavity wall of the quasi-optical mirror type microwave resonant cavity (13) is composed of a parabolic reflector (7) and an elliptical reflector (8) in a quasi-optical mode converter.

6. The 915MHz microwave plasma chemical vapor deposition device based on the collimated mirror type according to claim 5 is characterized in that: The material of the outer cavity wall of the quasi-mirror type microwave resonant cavity (13) is stainless steel; the material of the parabolic reflector (7) and the elliptical reflector (8) of the inner cavity wall of the quasi-mirror type microwave resonant cavity (13) is oxygen-free copper.

7. The 915MHz microwave plasma chemical vapor deposition device based on the collimated mirror type according to claim 7 is characterized in that: The quasi-mirror type microwave resonant cavity (13) has a hollow structure between the outer cavity wall and the inner cavity wall, and the hollow structure is filled with cooling water through the cavity heat dissipation water injection port (14) and the cavity heat dissipation water outlet (15).

8. The 915MHz microwave plasma chemical vapor deposition device based on a collimated mirror type according to claim 1, characterized in that: The distance between the bottom of the microwave antenna (4) and the sample platform (11) is 343 mm.

9. The 915MHz microwave plasma chemical vapor deposition device based on a collimated mirror type according to claim 1, characterized in that: The gas extraction system (10) is composed of a rotary vane mechanical pump and a molecular pump; the gas intake system (12) provides gas raw materials for preparing diamond materials, and the gas raw materials include hydrogen and methane.

10. The 915MHz microwave plasma chemical vapor deposition device based on the collimated mirror type according to claim 9, characterized in that: The gas raw material also includes one or more mixed gases of nitrogen, oxygen and argon.

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