A microwave plasma device

Abstract

This invention relates to the field of plasma physics and applied science research, and discloses a microwave plasma device, including a resonant cavity, a vacuum cavity, and a microwave generator, a circulator, a three-pin microwave tuner, a microwave mode converter, and a short-circuit piston connected in sequence. The two ends of the resonant cavity are connected to the microwave mode converter and the vacuum cavity, respectively. A microwave antenna extending into the resonant cavity is provided on the microwave mode converter. A quartz window is provided between the resonant cavity and the vacuum cavity to isolate them. Along the axial direction of the vacuum cavity, the dimensions at both ends are larger than the dimensions at the center. This design ensures the strongest electric field distribution at the center of the vacuum cavity, thereby generating stable plasma at that location and preventing the generation of secondary plasma in other areas. Furthermore, the microwave plasma device of this application does not require ignition, avoiding the problem of introducing impurities due to ignition.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of plasma physics and applied science research, and in particular to a microwave plasma device. Background Technology

[0002] Microwave plasma technology is a relatively new technology that has been developed in recent years and has been widely used in fields such as semiconductors and waste treatment. Its principle involves using high-energy microwaves to ionize gas, generating a large number of active ions. These active ions react with each other to regenerate new materials, or the energy of the active ions is used for cleaning and etching processes.

[0003] Microwave plasma typically has two important technical indicators: the size of the generated plasma and the ion concentration of the plasma. Generally, the higher the gas pressure, the higher the ion concentration of the generated plasma, the higher the microwave energy required, and the faster the material synthesis or other processing steps. The size of the plasma is often limited by the microwave wavelength; typically, the diameter of the generated plasma is no larger than half a wavelength. When the gas pressure is low or the microwave energy is high, multiple plasmas may be generated around multiple wavelength periods, with the plasmas diffusing to form a large plasma region.

[0004] However, in the process of developing this application, the inventors discovered that existing microwave plasma devices mainly fall into the following two categories: 1. Atmospheric pressure plasma torches, which generate a large electric field by compressing a waveguide and "igniting" with a metal tip to produce plasma inside a quartz tube. Gas is continuously introduced to maintain the gaseous composition of the plasma and to dissipate heat by carrying away a large amount of heat, thus protecting the quartz tube from melting at high temperatures. 2. Low-pressure plasma, which requires maintaining the cavity at a certain low pressure and then forming a certain standing wave mode within the cavity, or placing a metal structure inside the cavity to generate a localized strong electric field region to ionize the gas inside the cavity and produce stable plasma.

[0005] Deficiencies of existing technology:

[0006] 1. Atmospheric pressure plasma torches are unstable and contain many impurities in the synthesized materials. In particular, the need for a metal wire for ignition can easily introduce contaminants.

[0007] 2. When atmospheric pressure plasma microwaves are fed in from the side of the glass tube, the electric field distribution is uneven, which easily leads to carbon buildup on the quartz glass tube wall. Regular cleaning is required; otherwise, the equipment cannot be used for a long time.

[0008] 3. Low-pressure plasma has a low density, multiple modes within the cavity are uncontrollable, and the ion density is uneven, which can easily lead to local overheating or the generation of secondary plasma.

[0009] Therefore, it is necessary to invent a microwave plasma device to solve the above-mentioned technical problems. Summary of the Invention

[0010] To address the aforementioned technical problems, embodiments of the present invention provide a microwave plasma device to generate stable plasma and reduce contamination from introduced impurities.

[0011] The present invention provides the following technical solution to solve its technical problem: a microwave plasma device is provided, including a resonant cavity, a vacuum cavity, and a microwave generator, a circulator, a three-pin microwave tuner, a microwave mode converter, and a short-circuit piston connected in sequence. The two ends of the resonant cavity are respectively connected to the microwave mode converter and the vacuum cavity. The microwave mode converter is provided with a microwave antenna extending into the resonant cavity. A quartz window is provided between the resonant cavity and the vacuum cavity. The quartz window is used to isolate the resonant cavity and the vacuum cavity. Along the axial direction of the vacuum cavity, the dimensions at both ends of the vacuum cavity are larger than the dimensions at the middle of the vacuum cavity.

[0012] In some embodiments, along the axial direction of the vacuum cavity, the vacuum cavity includes a first vacuum cavity, a second vacuum cavity, and a third vacuum cavity connected in sequence. The end of the first vacuum cavity opposite to the second vacuum cavity is connected to the quartz window, wherein the inner diameter of the first vacuum cavity and the inner diameter of the third vacuum cavity are both larger than the inner diameter of the second vacuum cavity.

[0013] In some embodiments, the inner diameter of the first vacuum cavity gradually increases from one end toward the second vacuum cavity to the other end of the first vacuum cavity, and / or the inner diameter of the third vacuum cavity gradually increases from one end toward the second vacuum cavity to the other end of the third vacuum cavity.

[0014] In some embodiments, the vacuum cavity includes a transition cavity connected between the quartz window and the first vacuum cavity, and the transition cavity communicates with the first vacuum cavity.

[0015] In some embodiments, the inner wall of the second vacuum chamber is provided with a quartz tube.

[0016] In some embodiments, the microwave generator is configured to generate microwaves with a wavelength of L, and the inner diameter of the second vacuum cavity ranges from L / 1.31 to L / 0.82, and / or

[0017] The inner wall of the second vacuum chamber is provided with a quartz tube, and the microwave generator is configured to generate microwaves with a wavelength of L. The inner diameter of the second vacuum chamber is in the range of L / (1.31*1.87) to L / 0.82.

[0018] In some embodiments, a vacuum pump is also included, and an exhaust port is provided at one end of the vacuum chamber away from the resonant cavity, and the vacuum pump is connected to the exhaust port.

[0019] In some embodiments, a collection tank is provided at one end of the vacuum cavity away from the resonant cavity, the collection tank is connected to the vacuum cavity, and the exhaust port is provided in the collection tank.

[0020] In some embodiments, a separator is included, which is connected between the collection tank and the vacuum pump.

[0021] In some embodiments, the outer wall of the vacuum chamber is provided with a water-cooling channel.

[0022] Beneficial effects of the embodiments of the present invention:

[0023] Compared with the prior art, the dimensions at both ends of the vacuum cavity in the microwave plasma device provided in this application are larger than the dimensions in the middle of the vacuum cavity, thereby making the electric field strength strongest in the middle of the vacuum cavity, so as to generate stable plasma at this location and avoid secondary plasma generation in other areas of the vacuum cavity; the electric field mode of microwaves in the vacuum cavity is the TM01 mode, in which the electric field is strongest at the center of the cavity, and the electric field of the cavity wall and the quartz glass tube wall is almost zero, which can effectively prevent the plasma from etching the cavity wall and the quartz glass tube; the electric field of the quartz glass tube wall is extremely small and uniform, and no carbon deposits are generated; in addition, the microwave plasma device of this application does not require ignition, avoiding the problem of introducing impurities due to ignition. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of a microwave plasma device provided in one embodiment of the present invention;

[0026] Figure 2 yes Figure 1 The diagram shows the electric field distribution of the microwave plasma device.

[0027] The attached figures are labeled as follows:

[0028] 1. Microwave generator; 2. Circulator; 3. Three-pin microwave tuner; 4. Microwave mode converter; 5. Short-circuit piston; 6. Microwave cavity; 61. Resonant cavity; 62. Vacuum cavity; 621. First vacuum cavity; 622. Second vacuum cavity; 623. Third vacuum cavity; 624. Transition cavity; 7. Microwave antenna; 8. Quartz window; 9. Air inlet; 10. Quartz tube; 11. First water-cooling channel; 12. Second water-cooling channel; 13. First water inlet / outlet; 14. Second water inlet / outlet; 15. Vacuum pump; 16. Exhaust port; 17. Collection tank; 18. Separator. Detailed Implementation

[0029] To facilitate understanding of the present invention, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" / "connected to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as "connected to" another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "top," "bottom," etc., used in this specification indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "first" and "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0031] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0032] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] Please see Figure 1 , Figure 1One embodiment of the present invention provides a microwave plasma device, which includes a microwave generator 1, a circulator 2, a three-pin microwave tuner 3, a microwave mode converter 4, and a short-circuit piston 5 connected in sequence. Below the microwave mode converter 4 is a microwave cavity 6, which includes a resonant cavity 61 and a vacuum cavity 62. The two ends of the resonant cavity 61 are connected to the microwave mode converter 4 and the vacuum cavity 62, respectively. A microwave antenna 7 extending into the resonant cavity 61 is provided on the microwave mode converter 4. A quartz window 8 is provided between the resonant cavity 61 and the vacuum cavity 62 to isolate them. Along the axial direction H of the vacuum cavity 62, the dimensions at both ends of the vacuum cavity 62 are larger than the dimensions at the middle of the vacuum cavity 62. The axial direction H of the vacuum cavity 62 is the direction in which the microwave mode converter 4, the resonant cavity 61, and the vacuum cavity 62 are sequentially distributed.

[0034] It should be noted that the middle part of the vacuum cavity mentioned above refers to the part located between the two ends of the vacuum cavity, such as the part located between the top and bottom ends of the vacuum cavity.

[0035] Microwave generator 1 is used to emit microwave power. Circulator 2 is a device for microwave isolation, isolating the output from the reflected microwaves to prevent reflected microwaves from entering microwave generator 1 and causing damage to the microwave power source. Three-pin microwave tuner 3 adjusts the load impedance matching to reduce microwave reflection. Microwave mode converter 4 and microwave antenna 7 are used to convert microwaves in TE01 mode in the rectangular waveguide into microwaves in TEM mode on the coaxial line. Short-circuit piston 5 adjusts the energy transmission power of microwave mode converter 4. By adjusting the three-pin tuner 3 and short-circuit piston 5, the microwave reflection power can be controlled to ensure optimal microwave transmission.

[0036] The microwave power source couples microwave energy to the microwave mode converter 4 via the circulator 2, the three-pin microwave tuner 3 and the short-circuit piston 5. The TEM wave in the coaxial line is coupled into the resonant cavity 61 of the cylindrical cavity through the microwave antenna 7 to form the TM01 mode in the circular waveguide. Then it is coupled to the vacuum cavity 62 through the quartz window 8 to generate plasma.

[0037] In some embodiments, the short-circuit piston 5 is a piston structure that can be adjusted by a screw.

[0038] It is understandable that the resonant cavity 61 is at constant pressure.

[0039] In some embodiments, the resonant cavity 61 is typically made of a metal material such as stainless steel, and the vacuum cavity 62 is typically made of a metal material such as aluminum alloy or stainless steel.

[0040] In some embodiments, along the axial direction H of the vacuum cavity 62, the vacuum cavity 62 includes a first vacuum cavity 621, a second vacuum cavity 622 and a third vacuum cavity 623 connected in sequence, and the end of the first vacuum cavity 621 facing away from the second vacuum cavity 622 is connected to a quartz window 8.

[0041] In some embodiments, along the axial direction H of the vertical vacuum cavity 62, the inner diameter of the first vacuum cavity 621 and the inner diameter of the third vacuum cavity 623 are both greater than the inner diameter of any part of the second vacuum cavity 622.

[0042] In some embodiments, the second vacuum cavity 622 is a cylindrical cavity (that is, the inner diameter of any part of the second vacuum cavity is the same), and the first vacuum cavity 621 and / or the third vacuum cavity 623 are frustoconical cavities. Specifically, the first vacuum cavity 621 is a frustoconical cavity, and along the axial direction H of the vacuum cavity 62, the inner diameter of the first vacuum cavity 621 gradually increases from one end toward the second vacuum cavity 622 to the other end of the first vacuum cavity 621; the third vacuum cavity 623 is a frustoconical cavity, and the inner diameter of the third vacuum cavity 623 gradually increases from one end toward the second vacuum cavity 622 to the other end of the third vacuum cavity.

[0043] In some embodiments, the vacuum cavity 62 further includes a transition cavity 624, which is connected between the quartz window 8 and the first vacuum cavity 621, and the transition cavity 624 is in communication with the first vacuum cavity 621.

[0044] In some embodiments, along the axial direction H of the vertical vacuum cavity 621, the inner diameter of the transition cavity 624 is the same as the inner diameter of the resonant cavity 61, that is, the transition cavity 324 is a cylindrical cavity.

[0045] Please see Figure 2 In this embodiment, the second vacuum cavity 622 has the smallest inner diameter in the vacuum cavity, so the electric field strength at that location is the largest. Therefore, stable plasma can be generated at this location throughout the entire pressure range from high vacuum to standard atmospheric pressure, and secondary plasma will not be generated in other cavities of the vacuum cavity 62.

[0046] Please refer to the following: Figure 1 In some embodiments, the vacuum chamber 62 is provided with an air inlet 9 near the quartz window 8. Process gas is injected into the vacuum chamber 62 through the air inlet 9, and microwave energy excites the low-pressure gas to generate plasma. Process gases include CH4, H2, CO2, O2, N2, Ar, etc.

[0047] It is understood that multiple air inlets can be provided, or the air inlet can surround the vacuum chamber, that is, the air inlet is an annular air inlet.

[0048] In some embodiments, the microwave generator 1 is configured to generate microwaves with a wavelength of L. To ensure that the second vacuum cavity 622 in the vacuum cavity 62 is in TM01 mode and at maximum electric field strength, the inner diameter of the second vacuum cavity 622 ranges from L / 1.31 to L / 0.82. For example, for microwaves with a frequency of 4250MHz and a wavelength of 122mm, the inner diameter of the second vacuum cavity 622 ranges from 93mm to 148mm.

[0049] In some embodiments, in order to prevent impurities from being introduced by plasma etching of the metal cavity wall, the inner wall of the second vacuum cavity 622 is provided with a quartz tube 10.

[0050] In some embodiments, considering the influence of the quartz tube 10 on the wavelength, to ensure that the second vacuum cavity 622 in the vacuum cavity 62 is in TM01 mode and at the maximum electric field strength, the inner diameter range of the second vacuum cavity 622 is L / (1.31*1.87) to L / 0.82. For example, for microwaves with a frequency of 4250MHz and a wavelength of 122mm, the inner diameter range of the second vacuum cavity 622 is 49.8mm to 148mm. Furthermore, when the electric field mode in the second vacuum cavity 622 is TM01 mode, the electric field strength is strongest at the center of the quartz tube 10, while the electric field strength on the tube wall is extremely small and uniform, reducing the etching of the quartz tube wall by the plasma and effectively preventing carbon buildup on the tube wall.

[0051] In some embodiments, a water-cooling channel is provided on the outer wall of the vacuum chamber 62 to dissipate heat.

[0052] Specifically, the water-cooling channel includes a first water-cooling channel 11, a second water-cooling channel 12, a first inlet / outlet 13, and a second inlet / outlet 14. The first water-cooling channel 11 is connected to the first inlet / outlet 13, and the second water-cooling channel 12 is connected to the second inlet / outlet 14. The first water-cooling channel 11 and the second water-cooling channel 12 are wound around the outer wall of the vacuum chamber 62 and are connected. Cooling water enters from the first inlet / outlet 13 and the second inlet / outlet 14 respectively, and then flows in the first water-cooling channel 11 and the second water-cooling channel 12. After heat exchange, the cooling water is discharged from the first inlet / outlet 13 and the second inlet / outlet 14.

[0053] In some embodiments, the microwave plasma device includes a vacuum pump 15 connected to a vacuum chamber 62. Specifically, the vacuum chamber 62 has an exhaust port 16 at one end away from the resonant cavity 61. The vacuum pump 15 is connected to the exhaust port 16 and is used to evacuate the vacuum chamber 62 and adjust the gas pressure inside the vacuum chamber 62.

[0054] The microwave plasma device in this embodiment adjusts the gas pressure of the vacuum chamber by a vacuum pump and adjusts the energy transmission power of the microwave mode converter by a short-circuit piston, so that the vacuum chamber spontaneously generates plasma in the second vacuum chamber without the need for an ignition device, thus avoiding the introduction of impurities and contamination.

[0055] In some embodiments, a collection tank 17 is provided at one end of the vacuum chamber 62 away from the resonant cavity 61. The vacuum pump 15 is connected to the vacuum chamber 62 via the collection tank 17. The collection tank 17 is used to collect some of the heavier products in the reaction products in the vacuum chamber 62.

[0056] By setting up the collection tank 17, the collection tank 17 can initially separate the components in the reaction products according to the weight of the reaction products in the vacuum chamber 62, and can also prevent large particles from entering the vacuum pump 15 at the rear end, thus extending the service life of the vacuum pump 15.

[0057] In some embodiments, the vent 16 is located in the collection tank 17.

[0058] In some embodiments, the microwave plasma device further includes a separator 18 connected between the collection tank 17 and the vacuum pump 15, and the separator 18 is used to separate solids from the extracted gas.

[0059] In the microwave plasma device provided in this application embodiment, the dimensions at both ends of the vacuum cavity are larger than the dimensions at the center of the vacuum cavity, thereby making the electric field strength strongest at the center of the vacuum cavity. This allows for the generation of stable plasma at that location, preventing the generation of secondary plasma in other areas of the vacuum cavity. The electric field mode of the microwave in the vacuum cavity is the TM01 mode, in which the electric field is strongest at the center of the cavity, while the electric field on the cavity wall and the quartz glass tube wall is almost zero, which can effectively prevent the plasma from etching the cavity wall and the quartz glass tube. The electric field on the quartz glass tube wall is extremely small and uniform, and no carbon buildup will occur. In addition, the microwave plasma device of this application does not require ignition, avoiding the problem of introducing impurities due to ignition.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; under the concept of the present invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the present invention as described above, which are not provided in detail for the sake of brevity; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microwave plasma device, characterized by, The device includes a resonant cavity, a vacuum cavity, and a microwave generator, a circulator, a three-pin microwave tuner, a microwave mode converter, and a short-circuit piston connected in sequence. The two ends of the resonant cavity are respectively connected to the microwave mode converter and the vacuum cavity. The microwave mode converter is provided with a microwave antenna extending into the resonant cavity. A quartz window is provided between the resonant cavity and the vacuum cavity to isolate the resonant cavity and the vacuum cavity. Along the axial direction of the vacuum cavity, the dimensions at both ends of the vacuum cavity are larger than the dimensions at the middle of the vacuum cavity; Along the axial direction of the vacuum cavity, the vacuum cavity includes a first vacuum cavity, a second vacuum cavity, and a third vacuum cavity connected in sequence, and the end of the first vacuum cavity opposite to the second vacuum cavity is connected to the quartz window; Wherein, the inner diameter of the first vacuum chamber and the inner diameter of the third vacuum chamber are both larger than the inner diameter of the second vacuum chamber, and the second vacuum chamber is a cylindrical cavity; The inner diameter of the first vacuum chamber gradually increases from one end toward the second vacuum chamber to the other end of the first vacuum chamber, and the inner diameter of the third vacuum chamber gradually increases from one end toward the second vacuum chamber to the other end of the third vacuum chamber.

2. The microwave plasma device according to claim 1, characterized in that, The vacuum cavity includes a transition cavity, which is connected between the quartz window and the first vacuum cavity, and the transition cavity is in communication with the first vacuum cavity.

3. The microwave plasma device according to claim 1 or 2, characterized in that, The inner wall of the second vacuum chamber is provided with a quartz tube.

4. The microwave plasma device according to claim 1 or 2, characterized in that, The microwave generator is configured to generate microwaves with a wavelength of L, and the inner diameter of the second vacuum cavity ranges from L / 1.31 to L / 0.82; or The inner wall of the second vacuum chamber is provided with a quartz tube, and the microwave generator is configured to generate microwaves with a wavelength of L. The inner diameter of the second vacuum chamber ranges from L / (1.31*1.87) to L / 0.

82.

5. The microwave plasma apparatus of claim 1, wherein, It also includes a vacuum pump, and the end of the vacuum chamber away from the resonant cavity is provided with an exhaust port, and the vacuum pump is connected to the exhaust port.

6. The microwave plasma device according to claim 5, characterized in that, A material collection tank is provided at one end of the vacuum cavity away from the resonant cavity. The material collection tank is connected to the vacuum cavity, and the exhaust port is located in the material collection tank.

7. The microwave plasma apparatus of claim 6, wherein, Includes a separator, which is connected between the collection tank and the vacuum pump.

8. The microwave plasma device according to claim 1, characterized in that, The outer wall of the vacuum chamber is provided with a water-cooling channel.

Images