Ellipsoidal MPCVD device for diamond material growth

Abstract

The present invention relates to an ellipsoidal MPCVD device for growing diamond materials, which belongs to the field of diamond material growth equipment. The present invention aims to solve the problem of low microwave energy coupling efficiency during the operation of the existing MPCVD resonant cavity. A microwave power supply is provided at one end of the rectangular waveguide in the ellipsoidal MPCVD device for growing diamond materials of the present invention, a short-circuit piston is provided at the other end of the rectangular waveguide, an ellipsoidal resonant cavity is provided at the lower part of the rectangular waveguide, and one end of the microwave antenna extends into the ellipsoidal resonant cavity through the waveguide. The cavity wall of the ellipsoidal resonant cavity is ellipsoidal, and the interior of the cavity wall of the ellipsoidal resonant cavity is a hollow structure. The sample stage is provided at the bottom of the ellipsoidal resonant cavity, and the exhaust system and the air intake system are respectively connected to the ellipsoidal resonant cavity through pipelines. The present invention utilizes the dual-focus characteristics of the ellipsoid to achieve high-density plasma excitation and deposition growth of diamond.

Description

Technical Field

[0001] The invention belongs to the field of diamond material growth equipment, and in particular relates to an ellipsoidal MPCVD device for growing diamond materials. Background Art

[0002] Microwave plasma chemical vapor deposition (MPCVD) is a common method for preparing high-quality diamond materials. It can be used to prepare tool-grade, heat sink-grade, gem-grade, optical-grade and electronic-grade diamond single crystals and polycrystalline materials. The core of the MPCVD system is the microwave resonant cavity. The metal resonant cavity will reflect the input microwaves and eventually resonate at the deposition table to form a high microwave electric field area within a certain range. A well-designed MPCVD resonant cavity can ensure efficient coupling of microwave energy within a wide process range, while avoiding the excitation of secondary plasma and not etching the cavity and microwave window, thereby preparing high-quality diamond materials. However, different structural designs of the microwave resonant cavity will have a great impact on the microwave resonance effect, and at the same time, it is necessary to take into account the requirements of the diamond material growth process for the cavity, that is, it can operate stably for a long time at high power and pressure. Therefore, a reasonable microwave resonant cavity design is crucial for the controllable preparation of diamond materials. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of low microwave energy coupling efficiency, secondary plasma etching of quartz, difficulty in further increasing input power and gas pressure, etc. during the operation of the existing MPCVD resonant cavity, and to provide an ellipsoidal MPCVD device for the growth of diamond materials to ensure that efficient microwave energy coupling and long-term stable operation can be achieved at high power and gas pressure.

[0004] The ellipsoidal MPCVD device for growing diamond materials of the present invention comprises a microwave power supply, a rectangular waveguide, a microwave antenna, a short-circuit piston, an ellipsoidal resonant cavity and a sample stage. The microwave power supply is arranged at one end of the rectangular waveguide, the short-circuit piston is arranged at the other end of the rectangular waveguide, the ellipsoidal resonant cavity is arranged at the lower part of the rectangular waveguide, the rectangular waveguide and the ellipsoidal resonant cavity are connected through a circular waveguide, one end of the microwave antenna is fixed in the rectangular waveguide, the other end of the microwave antenna extends into the ellipsoidal resonant cavity through the circular waveguide, the cavity wall of the ellipsoidal resonant cavity is ellipsoidal, the interior of the cavity wall of the ellipsoidal resonant cavity is a hollow structure, the sample stage is arranged at the bottom of the ellipsoidal resonant cavity, and an exhaust system and an air intake system are respectively connected to the ellipsoidal resonant cavity through pipelines.

[0005] The ellipsoidal resonant cavity of the present invention utilizes the dual-focus characteristics of the ellipsoid. The microwave antenna and the sample stage are respectively located at the upper and lower focuses of the ellipsoid, effectively converging microwave energy above the sample stage. Although there is also a strong microwave electric field at the microwave antenna, due to the existence of the quartz bell jar outside the microwave antenna, it is in the external atmospheric environment, so the plasma will not be excited at the microwave antenna, and the air pressure inside the ellipsoidal resonant cavity is much lower than the atmospheric pressure. The gas can be easily dissociated above the sample stage to achieve high-density plasma excitation and diamond deposition growth. The pin insertion depth of the three-pin tuner, the microwave antenna insertion depth, the short-circuit piston horizontal position and the sample stage height can adjust the microwave electric field within a certain range, thereby ensuring stable excitation of the plasma above the sample stage under different powers and air pressures.

[0006] The ellipsoidal MPCVD device described in the present invention can realize efficient coupling of microwave energy within the power range of 5 to 15 kW and the gas pressure range of 10 to 30 kPa, meeting the process requirements of continuous growth of diamond materials for 100 to 400 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a schematic structural diagram of an ellipsoidal MPCVD device for growing diamond materials according to the present invention;

[0008] Figure 2 It is a diagram of the internal microwave electric field distribution of the ellipsoidal MPCVD device for growing diamond materials of the present invention;

[0009] Figure 3 This is a photo of the diamond film prepared using the ellipsoidal MPCVD device in the example. DETAILED DESCRIPTION

[0010] Specific implementation method one: The ellipsoidal MPCVD device for growing diamond materials in this implementation method includes a microwave power supply 1, a rectangular waveguide 3, a microwave antenna 4, a short-circuit piston 5, an ellipsoidal resonant cavity 6 and a sample stage 8. The microwave power supply 1 is provided at one end of the rectangular waveguide 3, and the short-circuit piston 5 is provided at the other end of the rectangular waveguide 3. The ellipsoidal resonant cavity 6 is provided at the lower part of the rectangular waveguide 3. The rectangular waveguide 3 and the ellipsoidal resonant cavity 6 are connected through a circular waveguide 11. One end of the microwave antenna 4 is fixed in the rectangular waveguide 3, and the other end of the microwave antenna 4 extends into the ellipsoidal resonant cavity 6 through the circular waveguide 11. The cavity wall of the ellipsoidal resonant cavity 6 is ellipsoidal, and the interior of the cavity wall of the ellipsoidal resonant cavity 6 is a hollow structure. The sample stage 8 is arranged at the bottom of the ellipsoidal resonant cavity 6, and the exhaust system 9 and the air intake system 10 are respectively connected to the ellipsoidal resonant cavity 6 through pipelines.

[0011] In this embodiment, the insertion depth of the microwave antenna 4 can be adjusted; the sample stage 8 can be adjusted in height in the axial direction, and the allowable adjustment distance is 0 to 60 mm.

[0012] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that a three-pin tuner 2 is further provided in the rectangular waveguide 3 on the side close to the microwave power source 1 .

[0013] Specific embodiment three: This embodiment is different from specific embodiments one or two in that a quartz bell jar 7 is provided on the outer cover of the microwave antenna 4, the quartz bell jar 7 is located on the top of the ellipsoidal resonant cavity 6, and the distance between the bottom surface of the quartz bell jar 7 and the sample stage 8 is 300 to 400 mm.

[0014] In this embodiment, the quartz bell jar 7 disposed outside the microwave antenna 4 is far away from the sample stage 8. Even at a relatively high microwave input power, the plasma excited at the sample stage 8 will not etch the quartz bell jar 7, thereby avoiding the situation where the plasma etches the quartz and causes diamond contamination. High microwave input power will effectively increase the deposition rate of the diamond film and improve the material preparation efficiency.

[0015] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that the hollow structure of the cavity wall of the ellipsoidal resonant cavity 6 is filled with cooling water.

[0016] Specific implementation method 5: This implementation method is different from specific implementation method 4 in that the material of the cavity wall is stainless steel.

[0017] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that the microwave antenna 4 and the sample stage 8 are respectively located at two foci of the ellipsoid.

[0018] Specific embodiment 7: This embodiment is different from any one of specific embodiments 1 to 6 in that the air intake system 10 provides gas raw materials for diamond growth, and the gas raw materials include hydrogen and methane.

[0019] Specific implementation eight: This implementation is different from specific implementation seven in that the gas raw material also includes one or more mixed gases of nitrogen, oxygen, and argon.

[0020] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 7 in that the air extraction system 9 is composed of a rotary vane mechanical pump and a molecular pump.

[0021] Specific embodiment ten: This embodiment is different from specific embodiments one to nine in that the major axis of the ellipsoidal resonant cavity 6 is 500 mm to 800 mm, the minor axis is 280 mm to 480 mm, and the length ratio of the major axis to the minor axis is controlled to be 1.4 to 1.6.

[0022] This embodiment optimizes the structural dimensions of the ellipsoidal resonant cavity to be suitable for the deposition of diamond films under high microwave input power.

[0023] Embodiment: The ellipsoidal MPCVD device for growing diamond materials in this embodiment comprises a microwave power supply 1, a rectangular waveguide 3, a microwave antenna 4, a short-circuit piston 5, an ellipsoidal resonant cavity 6, a sample stage 8, an exhaust system 9 and an air intake system 10. The microwave power supply 1 is provided at one end of the rectangular waveguide 3, and the microwave power supply 1 is used to output microwave energy. The short-circuit piston 5 is provided at the other end of the rectangular waveguide 3. The three-pin tuner 2 is provided in the rectangular waveguide 3. The three-pin tuner 2 and the rectangular waveguide 3 are used for microwave transmission. The specification is BJ26; the rectangular waveguide 3 An ellipsoidal resonant cavity 6 is arranged at the lower part, the rectangular waveguide 3 is connected to the ellipsoidal resonant cavity 6 through a circular waveguide 11, one end of the microwave antenna 4 is fixed in the rectangular waveguide 3, and the other end of the microwave antenna 4 extends into the ellipsoidal resonant cavity 6 through the circular waveguide 11, and a quartz bell jar 7 is arranged on the outer cover of the microwave antenna 4. The quartz bell jar 7 is a bell-shaped part made of high-purity quartz, which is used to maintain the vacuum inside the ellipsoidal resonant cavity 6 and serves as a microwave input window, with a diameter in the range of 100mm to 200mm and a height of 120 to 200mm;

[0024] The cavity wall of the ellipsoidal resonant cavity 6 is ellipsoidal, and the cavity wall of the ellipsoidal resonant cavity 6 is a double-layer 316L stainless steel. Cooling water flows through the hollow structure between the double layers to effectively cool the cavity. The sample stage 8 is arranged at the bottom of the ellipsoidal resonant cavity 6, and the substrate material required for diamond growth is placed above the sample stage 8. The top diameter is 50 to 80 mm. The microwave electric field resonates here to excite plasma and realize the deposition and growth of diamond materials. The exhaust system 9 and the air intake system 10 are respectively connected to the ellipsoidal resonant cavity 6 through pipelines.

[0025] The top of the ellipsoidal resonant cavity 6 of this embodiment is a flat top, on which a quartz bell jar 7 is fixed. The microwave antenna 4 and the sample stage 8 are respectively located at the upper and lower foci of the ellipsoid (ellipsoidal resonant cavity). The major axis of the ellipsoidal resonant cavity of this embodiment is 600 mm, the minor axis is 400 mm, the length ratio of the major axis to the minor axis is 1.5, and the distance between the bottom surface of the quartz bell jar 7 and the sample stage 8 is 350 mm.

[0026] The ellipsoidal resonant cavity utilizes the double-focus characteristics of the ellipsoid, with the microwave antenna at the upper focus and the sample stage at the lower focus. Figure 2It can be clearly seen that the microwave antenna and the sample stage below are brighter, indicating that there are strong microwave electric fields at these two locations. However, due to the sealing effect of the quartz bell jar, high-density plasma can only be excited above the sample stage inside the low-pressure cavity, while the microwave antenna in the atmospheric environment and other areas with weak electric fields (darker) inside the cavity will not excite plasma, thereby ensuring the stable operation capability of the MPCVD device. It also shows that the cavity has a high microwave energy coupling efficiency (plasma is only excited at the required position without generating additional energy loss). If there is also a high microwave electric field in the air pressure area inside the ellipsoidal cavity, secondary plasma will be excited, causing the plasma to etch the cavity wall, affecting the stable operation capability of the equipment.

[0027] The ellipsoidal MPCVD device of this embodiment is used to deposit diamond film, and the growth conditions are controlled as follows: hydrogen flow rate 400sccm, methane flow rate 20sccm, microwave power 10kW, gas pressure 20kPa, stable growth for 360h, effective deposition area greater than 2 inches, Figure 3 This is a photo of the 2-inch high-quality diamond film prepared.

Claims

1. Ellipsoidal MPCVD device for growing diamond material, characterized in that The ellipsoidal MPCVD device for growing diamond materials comprises a microwave power supply (1), a rectangular waveguide (3), a microwave antenna (4), a short-circuit piston (5), an ellipsoidal resonant cavity (6) and a sample stage (8); one end of the rectangular waveguide (3) is provided with the microwave power supply (1); the other end of the rectangular waveguide (3) is provided with the short-circuit piston (5); the lower part of the rectangular waveguide (3) is provided with the ellipsoidal resonant cavity (6); the rectangular waveguide (3) and the ellipsoidal resonant cavity (6) are connected via a circular waveguide (11); one end of the microwave antenna (4) is fixed in the rectangular waveguide (3); 4) extends into the ellipsoidal resonant cavity (6) through a circular waveguide (11); a quartz bell jar (7) is provided on the outer cover of the microwave antenna (4); the quartz bell jar (7) is located at the top of the ellipsoidal resonant cavity (6); the distance between the bottom surface of the quartz bell jar (7) and the sample stage (8) is 350 mm; the cavity wall of the ellipsoidal resonant cavity (6) is ellipsoidal; the cavity wall of the ellipsoidal resonant cavity (6) is a hollow structure; the sample stage (8) is arranged at the bottom of the ellipsoidal resonant cavity (6); and the exhaust system (9) and the intake system (10) are respectively connected to the ellipsoidal resonant cavity (6) through pipelines; The microwave antenna (4) and the sample stage (8) are respectively located at two foci of the ellipsoid; the major axis of the ellipsoidal resonant cavity (6) is 600 mm, the minor axis is 400 mm, and the length ratio of the major axis to the minor axis is controlled to be 1.

5.

2. The ellipsoidal MPCVD device for growing diamond material according to claim 1, characterized in that A three-pin tuner (2) is also provided on one side of the rectangular waveguide (3) close to the microwave power source (1).

3. The ellipsoidal MPCVD device for growing diamond material according to claim 1, characterized in that The hollow structure of the cavity wall of the ellipsoidal resonant cavity (6) is filled with cooling water.

4. The ellipsoidal MPCVD device for growing diamond material according to claim 3, characterized in that The cavity wall is made of stainless steel.

5. The ellipsoidal MPCVD device for growing diamond material according to claim 1, characterized in that The gas inlet system (10) provides gas raw materials for diamond growth, and the gas raw materials include hydrogen and methane.

6. The ellipsoidal MPCVD device for growing diamond material according to claim 5, characterized in that The gas raw material also includes one or more mixed gases of nitrogen, oxygen and argon.

7. The ellipsoidal MPCVD device for growing diamond material according to claim 1, characterized in that The air extraction system (9) is composed of a rotary vane mechanical pump and a molecular pump.

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