Reverse-throwing cavity type microwave plasma resonant cavity device with novel structure
By designing a new anti-throwing microwave plasma resonant cavity and water-cooling design in the MPCVD device, the microwave energy inhomogeneity and plasma instability caused by the resonant cavity structure are solved, and high-density, uniform plasma generation and high-efficiency diamond are achieved. Film deposition improves film quality and equipment stability.
Patent Information
- Application Number
- CN202411089777.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-09
- Publication Date
- 2024-12-13
AI Technical Summary
During the deposition of diamond films, the existing MPCVD resonant cavity devices have problems such as reduced plasma density and uniformity, decreased deposition rate, deterioration of film quality, reduced process stability, shortened equipment life and reduced energy efficiency. This is mainly due to the structure of the resonant cavity. The defects in the design lead to uneven distribution of microwave energy and plasma instability.
A new structural anti-throwing cavity microwave plasma resonant cavity device is designed, including a resonant cavity, a lower cylinder, a coaxial waveguide converter, a deposition part and a quartz part, adopting a unique anti-throwing cavity structure and water-cooled design. Ensure microwave energy concentration, plasma stability, and avoid plasma erosion and thermal radiation through the quartz window.
The high density and uniform distribution of plasma are achieved, the growth rate and quality of diamond film is improved, the equipment life is extended, and the energy utilization efficiency is improved, and it can operate stably under high microwave power, which promotes the deposition of high-efficiency diamond film.
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Figure CN119121196A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of plasma deposition, and relates to a novel structure reverse-throwing cavity type microwave plasma resonant cavity device. Background Art
[0002] Microwave plasma chemical vapor deposition (MPCVD) is currently the best method for manufacturing diamond films in terms of the shape and density of the generated plasma, its controllability, and its special discharge form. The efficiency of MPCVD diamond film deposition and the quality of the finished product are closely related to the resonant cavity structure. The early MPCVD resonant cavity device structure is relatively simple and easy to design, but it has many disadvantages such as slow deposition rate and small deposition area of the formed diamond film; and some MPCVD resonant cavity devices developed later and currently have greatly improved the deposition rate of diamond films, but basically have some problems, such as the generation of secondary plasma during the deposition process and the lack of microwave energy concentration.
[0003] The resonant cavity structure in the prior art has at least the following defects:
[0004] (1) Reduced plasma density and uniformity: Design defects in the resonant cavity may result in the microwave energy not being evenly distributed in the reaction cavity, thus affecting the density and uniformity of the plasma. This will directly affect the growth rate and quality of the diamond film.
[0005] (2) Decreased deposition rate: Due to the uneven distribution of microwave energy, the deposition rate of the diamond film may decrease, resulting in reduced production efficiency.
[0006] (3) Deterioration of film quality: Defects in the resonant cavity may lead to uneven distribution of active particles in the plasma, making the growth process of the diamond film uneven, resulting in defects in the crystal structure, such as cracks, holes or amorphous areas, thus affecting the quality of the film.
[0007] (4) Reduced process stability: Structural defects in the resonant cavity may cause microwave plasma instability, making the growth process of the diamond film difficult to control, affecting the repeatability and reliability of the deposition process.
[0008] (5) Shortened equipment life: Imperfect resonant cavity design may lead to microwave leakage or local overheating, which may accelerate the wear of internal components of the device, especially quartz windows or other metal parts, thereby shortening the life of the equipment.
[0009] (6) Reduced energy efficiency: Defects in the resonant cavity may lead to a waste of microwave energy, because part of the energy may be used to generate secondary plasma that does not participate in the growth reaction, thereby reducing the overall energy utilization efficiency. Summary of the invention
[0010] In order to solve the defects in the prior art, the present invention provides a novel structure anti-reflection cavity type microwave plasma resonant cavity device, and the technical solution is:
[0011] It includes a resonant cavity, a lower cylinder, a coaxial waveguide converter, a deposition part and a quartz part, wherein:
[0012] The resonant cavity comprises a top cover, a throwing cavity, a middle cylinder, an air inlet, an air outlet, a temperature measuring hole and an observation window, wherein the top cover, the throwing cavity and the middle cylinder are arranged in sequence from top to bottom, the air inlet is arranged at the top cover, the air outlet is arranged at the outer wall of the middle cylinder, the temperature measuring hole is arranged at the throwing cavity, and the observation window is arranged at the outer wall of the middle cylinder; the lower cylinder is arranged below the resonant cavity, and a ring antenna is arranged inside the lower cylinder; the coaxial waveguide converter is connected to the lower cylinder, which is the transmission path of microwaves; the deposition part is arranged at the bottom of the resonant cavity; the quartz part is arranged between the coaxial waveguide converter and the lower cylinder to provide vacuum protection for the resonant cavity.
[0013] Preferably, the top cover is a circular metal cover, which is located at the top of the resonance cavity.
[0014] Preferably, the parabola cavity is a rotating body obtained by rotating a parabola around the central axis of the resonant cavity, and its parabola equation is y=0.0053x 2 , the range of x is -94~94mm.
[0015] Preferably, the coaxial waveguide converter comprises a coaxial outer conductor and a coaxial inner conductor, which together constitute a coaxial line and serve as a transmission path for microwaves.
[0016] Preferably, the ratio of the outer diameter to the inner diameter of the coaxial line is 2.3.
[0017] Preferably, the deposition part comprises a deposition platform and a substrate, wherein the deposition platform is arranged at the bottom of the resonance cavity, and the substrate is placed at the center of the deposition platform.
[0018] Preferably, the substrate is a circular silicon wafer with a radius of 35 mm and a thickness of 3 mm.
[0019] Preferably, the quartz portion includes a quartz ring and a quartz window.
[0020] Preferably, the thickness of the quartz ring is 6 mm.
[0021] Preferably, it also includes a water cooling part, specifically a cooling water path arranged inside the resonant cavity, the deposition platform, the lower cylinder and the coaxial waveguide converter.
[0022] Compared with the prior art, the present invention has at least the following beneficial effects:
[0023] 1. The quartz ring window of the device is located below the reaction chamber, thus effectively avoiding direct contact with the plasma. This design ensures that the microwave window will not be eroded by the plasma when the device is running at high power.
[0024] 2. In this device, the microwave energy in the resonant chamber is almost entirely concentrated above the central deposition platform, avoiding the deposition of surface carbon impurities caused by excessive dispersion of microwave energy near other components, thereby avoiding contamination of the diamond film deposition process.
[0025] 3. The device adopts a unique anti-throwing resonant cavity structure design, which is characterized by a concentrated electric field distribution in the microwave resonant cavity, which can excite a stable and high-density plasma.
[0026] 4. The device controls the distance between any point on the inner wall of the resonant cavity and the center point of the substrate to be greater than 6 / 7λg, where λg (12.2cm) is the wavelength of the introduced microwave, so that the inner wall of the resonant cavity in direct contact with the plasma in the device is far away from the high-temperature plasma area, thereby reducing the heat radiation to the inner wall of the chamber, avoiding the deposition of graphite and carbon compounds on the inner wall of the chamber, and avoiding the loss of the inner wall of the chamber.
[0027] 5. The main components of the device, such as the dome cover, the anti-throwing cavity wall, the outer wall of the middle cylinder, the deposition platform for depositing diamond film, the inner and outer walls of the lower cylinder, the rectangular waveguide, and the inner and outer conductors of the coaxial cable, are all made of metal and have cooling water channels designed inside. This design enables the equipment to be effectively water-cooled and dissipated, thereby maintaining the stability of the device under high microwave power operating conditions.
[0028] 6. This device is a high-power MPCVD device that can operate under higher microwave input power conditions (6kw), can handle higher power levels, achieve a more efficient diamond film deposition process, and produce a denser and more uniform plasma, thereby promoting the growth of diamond films. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 It is a schematic structural diagram of a novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to an embodiment of the present invention;
[0030] Figure 2 The electric field distribution diagram of the novel structure anti-repelling cavity type microwave plasma resonant cavity device simulated in COMSOL software according to an embodiment of the present invention;
[0031] Figure 3 This is a plasma distribution diagram simulated in COMSOL software of a novel structure reverse-projection-cavity microwave plasma resonant cavity device according to an embodiment of the present invention. DETAILED DESCRIPTION
[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0033] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.
[0034] See also Figure 1 , is a schematic structural diagram of a novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to an embodiment of the present invention, comprising a resonant cavity, a lower cylinder 4, a coaxial waveguide converter, a deposition part and a quartz part, wherein the resonant cavity comprises a top cover 1, a throwing cavity 2, a middle cylinder 3, an air inlet 18, an air outlet 12, a temperature measuring hole and an observation window 11, wherein the top cover 1, the throwing cavity 2 and the middle cylinder 3 are arranged in sequence from top to bottom, the air inlet 18 is arranged at the top cover 1, the air outlet 12 is arranged at the outer wall of the middle cylinder 3, the temperature measuring hole is arranged at the throwing cavity 2, and the observation window 11 is arranged at the outer wall of the middle cylinder 3; the lower cylinder 4 is arranged below the resonant cavity, and a ring antenna 6 is arranged inside the lower cylinder 4; the coaxial waveguide converter is connected to the lower cylinder 4, which is a transmission path for the microwave 9; the deposition part is arranged at the bottom of the resonant cavity; the quartz part is arranged between the coaxial waveguide converter and the lower cylinder 4, and the resonant cavity is vacuum protected.
[0035] In the specific embodiment, the resonant cavity is the core of the device. The top cover 1 is a circular metal cover with a radius of 25 mm, which is located above the parabola cavity 2. The parabola cavity 2 is a rotating body formed by a parabola rotating around the central axis of the resonant cavity. The overall shape is an inverted parabola, and its parabola equation is y=0.0053x 2 , x ranges from -94 to 94 mm. This design makes the electric field distribution in the resonant cavity concentrated, which is conducive to exciting a stable and high-density plasma 16, thereby improving the quality of the diamond film. The middle cylinder 3 is connected to the polishing cavity 2 and is located below it.
[0036] The lower cylinder 4 is composed of an outer wall 5, an inner wall and a cylindrical ring antenna 6, and is the lower extension of the resonant cavity. The coaxial waveguide converter includes a coaxial line composed of a coaxial outer conductor 7 and a coaxial inner conductor 8. The coaxial line constitutes a transmission path for microwaves 9, and microwaves 9 enter the resonant cavity through the transmission of the coaxial line and the ring antenna 6. In this device, the ratio of the outer diameter to the inner diameter of the coaxial line is 2.3, that is, the ratio of the diameter of the coaxial outer conductor 7 to the diameter of the coaxial inner conductor 8 is 2.3. In a specific embodiment, the outer diameter and inner diameter of the coaxial line are 46 mm and 20 mm, respectively, which can maintain a small transmission loss under high microwave 9 input power.
[0037] The deposition part includes a deposition platform 14 and a substrate 15: the deposition platform 14 is located at the bottom of the resonant cavity, the substrate 15 is a circular silicon wafer with a radius of 35 mm and a thickness of 3 mm, located at the center of the deposition platform 14, and is used to deposit a diamond film with a diameter of 70 mm. Plasma 16 is generated above the substrate 15 to promote the growth of the diamond film.
[0038] A quartz ring with a thickness of 6 mm is located inside the loop antenna 6 to maintain the vacuum environment in the reaction chamber. The location of the quartz window 13 is designed to prevent the quartz ring from contacting the plasma 16 and being etched by the plasma 16 during high power operation.
[0039] The air inlet 18 is located at the center of the top cover 1 and is connected to the air inlet duct 10, while the air outlets 12 are arranged on the side wall of the middle cylinder 3, and there are four air outlets 12 in total, which are evenly distributed.
[0040] The temperature measuring hole is located on the wall of the polishing chamber 2 and is connected to the temperature measuring instrument 17 for monitoring the temperature of the reaction chamber during the deposition process.
[0041] The observation window 11 is located on the side wall of the middle cylinder 3, providing a mechanism for observing the internal conditions of the chamber during the deposition process.
[0042] Through the above structural design, the device can achieve efficient deposition of large-area high-quality diamond films under high microwave input power conditions.
[0043] The device also includes a water cooling part, because the main components of the device, such as the top cover 1, the wall of the cavity 2, the outer wall of the middle cylinder 3, the deposition platform 14, the inner wall of the lower cylinder 4, the outer wall 5 of the lower cylinder 4, the cylindrical ring antenna 6, the coaxial inner conductor 8 and the coaxial outer conductor 7, are all made of metal materials. Cooling water channels are designed inside these components, so that the equipment can be effectively water-cooled and heat-dissipated. Such a design ensures that the entire device can operate stably under the condition of high microwave 9 power input, thereby achieving effective deposition of diamond film.
[0044] When operating the MPCVD apparatus of the present invention to deposit a diamond film, the following steps are followed:
[0045] 1. Prepare a 3 mm thick, 70 mm diameter single crystal silicon wafer as substrate 15 and place it on the deposition platform 14. Next, start the vacuum pump to evacuate the inside of the device to a vacuum state to ensure an oxygen-free and water-free environment during the deposition process;
[0046] 2. Once the required vacuum level is reached inside the device, a mixture of hydrogen (H2) and methane (CH4) is introduced. By adjusting the gas flow rate, the gas pressure inside the device can be controlled to achieve the optimal conditions for depositing diamond films.
[0047] 3. Input microwaves 9 with a frequency of 2.45 GHz and a power of 6000 W. The microwaves 9 excite plasma 16 above the deposition platform 14 in the device. The plasma 16 region is a key region for the growth of diamond films. The presence of the plasma 16 promotes the reaction between carbon atoms and hydrogen atoms in methane, thereby starting to deposit diamond films on the substrate 15.
[0048] 4. The deposition process continues for a period of time to achieve the required diamond film thickness;
[0049] 5. After the deposition is completed, turn off the gas source, microwave 9 power supply and vacuum pump in the reverse order. First, turn off the gas supply, stop the microwave 9 input, and then turn off the vacuum pump to restore the pressure inside the device to atmospheric pressure. Finally, take out the substrate 15 with the diamond film deposited, and complete the deposition process of the entire diamond film.
[0050] See also Figure 2 This is an electric field distribution diagram of the novel structure anti-repelling cavity type microwave plasma resonant cavity device simulated in COMSOL software according to an embodiment of the present invention.
[0051] Through the electric field distribution diagram, the specific TM032 mode in the resonant cavity can be observed, and the excitation and suppression of the specific mode can be achieved, thereby optimizing the generation and maintenance of the plasma. It is verified that the resonant frequency of the resonant cavity, 2.45 GHz, matches the frequency of the microwave source, which means higher energy transmission efficiency and more stable plasma operation. The electric field distribution diagram shows that the electric field is concentrated in the reaction area, indicating that the microwave energy utilization efficiency of the device is high, the energy is effectively utilized, and unnecessary energy loss is reduced.
[0052] See also Figure 3 This is a plasma distribution diagram simulated in COMSOL software of a novel structure reverse-projection-cavity microwave plasma resonant cavity device according to an embodiment of the present invention.
[0053] From the plasma distribution diagram, it can be observed that the secondary plasma is small, the plasma distribution is relatively concentrated, stable and high-density, indicating that the energy can be as low as possible during the deposition process and the deposition efficiency can be as high as possible. At the same time, the plasma distribution diagram shows that the plasma is stable, indicating that the new structure helps to maintain a stable plasma state, which is very beneficial for continuous production and high-quality thin film deposition.
[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A novel structure reverse-throwing cavity type microwave plasma resonant cavity device, characterized in that: It includes a resonant cavity, a lower cylinder, a coaxial waveguide converter, a deposition part and a quartz part, wherein: The resonant cavity comprises a top cover, a throwing cavity, a middle cylinder, an air inlet, an air outlet, a temperature measuring hole and an observation window, wherein the top cover, the throwing cavity and the middle cylinder are arranged in sequence from top to bottom, the air inlet is arranged at the top cover, the air outlet is arranged at the outer wall of the middle cylinder, the temperature measuring hole is arranged at the throwing cavity, and the observation window is arranged at the outer wall of the middle cylinder; the lower cylinder is arranged below the resonant cavity, and a ring antenna is arranged inside the lower cylinder; the coaxial waveguide converter is connected to the lower cylinder, which is the transmission path of microwaves; the deposition part is arranged at the bottom of the resonant cavity; the quartz part is arranged between the coaxial waveguide converter and the lower cylinder to provide vacuum protection for the resonant cavity.
2. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 1 is characterized in that: The top cover is a circular metal cover, which is located at the top of the resonance cavity.
3. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 1 is characterized in that: The parabola cavity is a rotating body obtained by rotating a parabola around the central axis of the resonant cavity. The parabola equation is y=0.0053x 2 , the range of x is -94~94mm.
4. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 1 is characterized in that: The coaxial waveguide converter comprises a coaxial outer conductor and a coaxial inner conductor, which form a coaxial line and serve as a transmission path for microwaves.
5. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 4 is characterized in that: The ratio of the outer diameter to the inner diameter of the coaxial line is 2.
3.
6. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 1 is characterized in that: The deposition part comprises a deposition platform and a substrate, wherein the deposition platform is arranged at the bottom of the resonance cavity, and the substrate is placed at the center of the deposition platform.
7. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 6 is characterized in that: The substrate is a circular silicon wafer with a radius of 35 mm and a thickness of 3 mm.
8. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 1 is characterized in that: The quartz portion includes a quartz ring and a quartz window.
9. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 8 is characterized in that: The thickness of the quartz ring is 6 mm.
10. The novel structure reverse-throwing cavity type microwave plasma resonant cavity device according to claim 6 is characterized in that: It also includes a water cooling part, specifically a cooling water path arranged inside the resonance cavity, the deposition platform, the lower cylinder and the coaxial waveguide converter.