Linear wide-width atmospheric pressure microwave plasma source based on rectangular waveguide and implementation method thereof

Abstract

The invention provides a linear wide-width atmospheric pressure microwave plasma source based on a rectangular waveguide and an implementation method thereof. The linear wide-width atmospheric pressure microwave plasma source comprises a first rectangular waveguide, a gradient impedance matcher, a second rectangular waveguide, a plasma reactor and a gas pipe which are connected in sequence, the height of the second rectangular waveguide is smaller than that of the first rectangular waveguide; the plasma reactor is suspended on the second rectangular waveguide, is perpendicular to the top surface of the second rectangular waveguide and is perpendicular to the microwave transmission direction, and at least part of the plasma reactor extends into the second rectangular waveguide from the top surface of the second rectangular waveguide; the gas pipe horizontally penetrates through the part, located in the second rectangular waveguide, of the plasma reactor and extends out of the two sides of the second rectangular waveguide by a preset length from the two sides of the plasma reactor, and vent holes are formed in the top of the section, located in the plasma reactor, of the gas pipe in an array mode. The wide plasma generated by the plasma source is more uniform, the maintenance time is long, and the effective area of the wide plasma is wide in convertibility.

Description

Technical Field

[0001] This application belongs to the technical field of microwave plasmas, and particularly relates to a linear wide-width atmospheric pressure microwave plasma source based on a rectangular waveguide and a method for realizing the same. Background Art

[0002] As an efficient, green, and controllable technology, microwave plasmas have been widely used in the industrial field. Currently, the maturely applied atmospheric pressure microwave plasma sources mainly include structures such as coaxial resonators, surface wave resonators, microstrip line resonators, hairpin-type exciters, and rectangular waveguides. Among them, the microwave plasma source based on a rectangular waveguide has been widely used in multiple fields because of its good coupling efficiency, good controllability, and ability to effectively transmit power, support specific modes, and generate uniform linear plasmas. However, the existing microwave plasma sources based on rectangular waveguides still face some challenges. Especially in large-area and large-scale applications, there are problems such as low microwave energy utilization rate and limited plasma area generated. These problems limit their further application in industry, especially in high-end manufacturing scenarios that require large-area uniform plasma coverage, and the existing technologies have not been able to fully meet the requirements. Therefore, how to break through these bottlenecks and design a microwave plasma source that can provide a large area, high uniformity, low energy consumption, and high efficiency is one of the key research directions at present.

[0003] In the prior art, the Chinese patent document with the publication number CN118019201A records a solution for a microwave plasma source system and its usage method. This solution effectively reduces microwave reflection and improves the transmission efficiency of microwave energy by adding a wedge-shaped dielectric plate in the rectangular waveguide. The Chinese patent document with the publication number CN116936329A records a solution for an atmospheric pressure microwave plasma double-waveguide coupling device. It uses a microwave plasma device with double-waveguide coupling, which significantly increases the energy density of the electromagnetic field, enhances the ionization ability of the plasma, and increases the content of active particles in the plasma. However, the processing areas of these two prior art solutions are limited and it is difficult to meet the large-scale application requirements. In this type of design, the reactor that confines the plasma is usually cylindrical, which makes the generated plasma jets all columnar.

[0004] In the prior art, a Chinese patent document with the publication number CN112616236 A discloses a scheme for a dual-antenna enhanced linear microwave plasma. Based on the existing linear microwave plasma source, this scheme effectively increases the transverse area of the plasma generated by the linear microwave plasma source by introducing a dual-antenna structure, ultimately achieving the goal of reducing the number of microwave power supplies. However, the dual-antenna design increases system complexity, including antenna layout, phase matching, and electromagnetic wave transmission. If the phase control or power distribution is improper, it may lead to low power transmission efficiency and uneven plasma, affecting its stability. Summary of the Invention

[0005] To address the deficiencies of the above-mentioned related prior art, the present application provides a method for realizing a linear wide-width atmospheric pressure microwave plasma source based on a rectangular waveguide, overcoming the defects of poor uniformity, stability, and energy utilization efficiency shown in large-scale applications due to the size limitations faced by traditional plasma sources, improving the performance of the microwave plasma source, generating a wider-width plasma that is more uniform and has a longer maintenance time, and having a wide variability in the effective area of the wider-width plasma, better meeting the industrial production requirements of microwave plasma sources in fields such as semiconductors and aerospace.

[0006] To achieve the above object, the present invention adopts the following technologies: A linear wide-width atmospheric pressure microwave plasma source based on a rectangular waveguide includes a first rectangular waveguide, a tapered impedance matcher, a second rectangular waveguide, a plasma reactor, and a gas tube; The height of the second rectangular waveguide is less than the height of the first rectangular waveguide; The tapered impedance matcher is connected between the first rectangular waveguide and the second rectangular waveguide; The plasma reactor is suspended at the second rectangular waveguide, perpendicular to the top surface of the second rectangular waveguide and perpendicular to the microwave transmission direction in the second rectangular waveguide, and at least part of the plasma reactor extends into the second rectangular waveguide from the top surface of the second rectangular waveguide; The gas tube horizontally penetrates through the part of the plasma reactor that is inside the second rectangular waveguide, extends a predetermined length from both sides of the plasma reactor, and extends outside both sides of the second rectangular waveguide. Vent holes are arrayed at the top of the section of the gas tube that is inside the plasma reactor.

[0007] Furthermore, one end of the first rectangular waveguide is open for feeding microwaves, and the other end is connected to the tapered impedance matcher; one end of the second rectangular waveguide is connected to the tapered impedance matcher, and the other end is closed; the tapered impedance matcher is used to achieve impedance matching of microwaves from the first rectangular waveguide to the second rectangular waveguide and compress the microwaves to enhance the internal field strength; at least one end of the gas tube is used for introducing air flow; the top of the plasma reactor is open for forming and outputting a wide-width plasma jet.

[0008] Furthermore, the part of the plasma reactor located inside the second rectangular waveguide has a predetermined spacing from the bottom surface of the second rectangular waveguide.

[0009] A method for realizing a linear wide-width atmospheric pressure microwave plasma source based on a rectangular waveguide, which is realized by using the linear wide-width atmospheric pressure microwave plasma source of the rectangular waveguide, includes the steps: The microwave entering the first rectangular waveguide is impedance-matched through a tapered impedance matcher and the TE 10 mode electric field is compressed and enhanced and then enters the second rectangular waveguide; The air flow enters from the end of the gas pipe and uniformly flows into the plasma reactor through the ventilation holes; The microwave electric field in the second rectangular waveguide acts on the air flow flowing into the plasma reactor and breaks it down, generating a linear wide-width plasma jet, which is output from the top of the plasma reactor.

[0010] By setting the aperture, spacing, and number of the ventilation holes, the uniformity of the air flow flowing into the plasma reactor is adjusted, and further the generation area and uniformity of the linear wide-width plasma jet are regulated.

[0011] The beneficial effects of the present invention are as follows: 1. The present invention effectively solves the problems that may occur when the existing plasma source contacts the object to be processed, such as insufficient plasma uniformity, difficult excitation, short maintenance time, or even discharge extinction, and energy loss during plasma generation; through the solution of the present invention, easy excitation, strong stability, high uniformity, and high microwave energy utilization rate of wide-width plasma can be achieved in the plasma reactor; 2. The solution of the present invention breaks through the traditional design, effectively expands the size of the plasma reactor, and the size can be adjusted according to the waveguide wavelength of the TE 10 mode in the rectangular waveguide, which can meet the requirements for the reactor size in different application scenarios. In addition, a wide-type suspended design of the plasma reactor is adopted, making it suspended inside the rectangular waveguide. Different from the traditional method of directly penetrating the cylindrical ceramic tube that confines the plasma through the entire rectangular waveguide, not only the plasma generation area is significantly increased, but also because it is not flush with the bottom surface of the second rectangular waveguide but has a gap, the microwave energy can be maximally utilized. And because the wide side of the plasma reactor is designed parallel to the wide side of the rectangular waveguide, and the TE 10Adapted to the characteristics of the mold, this design can not only ensure that the plasma reactor is at the strongest part of the electric field, enabling the gas to be effectively broken down, making the generated wide - range plasma more uniform and having a longer maintenance time, but also the effective area of the wide - range plasma has a wide variability. In addition, the present invention improves the previous air intake method by arranging ventilation holes in an array on the surface of the intake pipe, effectively ensuring the uniformity of the gas; 3. By using a gradient impedance matcher, not only can effective impedance matching be achieved, ensuring that microwave energy can be efficiently transmitted to the next - stage microwave device, but also by compressing the TE 10 mode, the microwave field strength is significantly increased, thus efficiently achieving the breakdown of the gas. Brief Description of the Drawings

[0012] Figure 1 is a schematic structural diagram of a linear wide - range atmospheric - pressure microwave plasma source according to an embodiment of the present application.

[0013] Figure 2 is a partial cross - sectional view of the plasma reactor and the intake pipe of the embodiment of the present application provided at the second rectangular waveguide.

[0014] Figure 3 is a partial cross - sectional view of the intake pipe provided in the plasma reactor of the embodiment of the present application.

[0015] Figure 4 is a schematic top - view electric - field distribution diagram of the cross - section of the linear wide - range atmospheric - pressure microwave plasma source according to an embodiment of the present application.

[0016] Figure 5 is a schematic longitudinal - cross - sectional electric - field distribution diagram of the cross - section of the linear wide - range atmospheric - pressure microwave plasma source according to an embodiment of the present application.

[0017] Reference Numerals: 1 - First rectangular waveguide, 2 - Gradient impedance matcher, 3 - Second rectangular waveguide, 4 - Plasma reactor, 5 - Gas pipe, 6 - Ventilation hole. Detailed Embodiments

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will describe the embodiments of the present invention in detail with reference to the drawings. However, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0019] An embodiment of the present application provides a linear wide - range atmospheric - pressure microwave plasma source based on a rectangular waveguide, as Figures 1-3 shown, including a first rectangular waveguide 1, a gradient impedance matcher 2, a second rectangular waveguide 3, a plasma reactor 4, and a gas pipe 5.

[0020] The height of the second rectangular waveguide 3 is less than that of the first rectangular waveguide 1; the tapered impedance matcher 2 is connected between the first rectangular waveguide 1 and the second rectangular waveguide 3. Specifically, the top surfaces of the first rectangular waveguide 1, the tapered impedance matcher 2, and the second rectangular waveguide 3 are flush and connected in sequence along their respective length directions, as Figure 1 shown.

[0021] The plasma reactor 4 can be a quartz plasma reactor, suspended at the second rectangular waveguide 3, preferably located at the center of the second rectangular waveguide 3, which is the place where the electric field of the second rectangular waveguide 3 is the strongest, mainly to make it easier for microwaves to break down the gas to form plasma. The plasma reactor 4 is arranged parallel to the width direction of the second rectangular waveguide 3, perpendicular to the top surface of the second rectangular waveguide 3 and perpendicular to the microwave transmission direction in the second rectangular waveguide 3. This arrangement can be used to generate a large area of plasma.

[0022] Moreover, at least a part of the plasma reactor 4 extends into the second rectangular waveguide 3 from the top surface of the second rectangular waveguide 3, as Figure 2 shown. The upper part of the plasma reactor 4 is above the top surface of the second rectangular waveguide 3, and the lower part of the plasma reactor 4 is inside the second rectangular waveguide 3 below the top surface of the second rectangular waveguide 3. At the same time, the part of the plasma reactor 4 located inside the second rectangular waveguide 3 has a predetermined distance from the bottom surface of the second rectangular waveguide 3, that is, the bottom surface of the lower part of the plasma reactor 4 is not flush with the bottom surface of the second rectangular waveguide 3.

[0023] As Figures 2-3 shown, the gas pipe 5 horizontally penetrates through the part of the plasma reactor 4 located inside the second rectangular waveguide 3, and extends a predetermined length from both sides of the plasma reactor 4 and extends outside both sides of the second rectangular waveguide 3. The top of the section of the gas pipe 5 located in the plasma reactor 4 is provided with ventilation holes 6 in an array, and the ventilation holes 6 communicate with the inside of the plasma reactor 4. The top of the plasma reactor 4 is open to form and output a wide plasma jet.

[0024] Specifically, one end of the first rectangular waveguide 1 is open for feeding microwaves, and the other end is connected to the tapered impedance matcher 2; the tapered impedance matcher 2 is used to achieve impedance matching of microwaves from the first rectangular waveguide 1 to the second rectangular waveguide 3 and compress the microwaves to enhance the internal field strength; specifically, the first rectangular waveguide 1 can adopt a BJ22 standard rectangular waveguide. Here, a TE 10 mode with low loss can be generated, and the TE 10The compression of the mode electric field generates a stronger microwave electric field within the second rectangular waveguide 3. The tapered impedance matcher 2 enables, through impedance matching, the microwave energy introduced from the first rectangular waveguide 1 to be fed into the second rectangular waveguide 3 without reflection and efficiently. Meanwhile, through the compression of the rectangular waveguide, the microwave electric field entering the second rectangular waveguide 3 is enhanced, thereby enabling the gas to obtain higher energy here and ensuring effective breakdown.

[0025] One end of the second rectangular waveguide 3 is connected to the tapered impedance matcher 2, and the other end is closed, which allows the microwave reaching the other end of the second rectangular waveguide 3 to be reflected back to the plasma reactor 4. Here, the microwave energy can be absorbed by the plasma reactor 4 again, avoiding waste of microwave energy.

[0026] The gas tube 5 is cylindrical, and at least one end is used for introducing gas flow; specifically, it can be that one end is closed and the other end is used for introducing gas flow, or both ends are used for introducing gas flow. After the gas flow enters, it will uniformly enter the interior of the plasma reactor 4 through the ventilation holes 6.

[0027] The plasma reactor 4 is arranged parallel to the width direction of the second rectangular waveguide 3, which is adapted to the characteristics of the TE 10 mode. When the wavelength of the microwave changes, the size of the plasma reactor 4 can also be designed and adjusted accordingly. Therefore, the effective treatment area of the plasma source provided in this example can vary with the waveguide wavelength of the TE 10 mode according to different application scenarios. In addition, the entire plasma reactor 4 can always be located at the center of the TE 10 mode, where the electric field is the strongest and uniform, enabling the plasma to utilize more microwave energy and be effectively broken down. This not only enables the generated wide - amplitude plasma jet to be more uniform and linear, but also, due to the stronger microwave electric field, the plasma can maximize the absorption of energy, so that the formed wide - amplitude plasma can be maintained for a longer time.

[0028] In addition, in this example, the setting that the bottom surface of the lower part of the plasma reactor 4 is not flush with the bottom surface of the second rectangular waveguide 3 can prevent most of the energy from being directly reflected and wasted when the microwave energy reaches the surface of the plasma reactor 4. Furthermore, it helps the microwave energy reflected back after the generated electric field is transmitted to the end of the second rectangular waveguide 3 to be reused by the plasma reactor 4, making it have a higher energy utilization rate, and also ensuring the continuity of the electric field, making the electric field distribution around the plasma reactor 4 more uniform, thus being more conducive to generating a plasma with higher uniformity.

[0029] Preferably, as Figure 3As shown, the outer wall of the gas tube 5 is attached to the front and rear side walls of the plasma reactor 4, and is also attached to the bottom wall of the plasma reactor 4. This structural design ensures that the outer wall of the gas tube 5 is tightly fitted with the front and rear walls and the bottom wall of the plasma reactor 4. Firstly, the spatial positioning of the vent 6 can be effectively performed, so that it is always parallel to the plane extending from the plasma reactor 4 to the top of the second rectangular waveguide 3; secondly, the gas flow direction is strictly perpendicular to the axis of the plasma reactor 4 to form a stable laminar flow; and finally a uniformly distributed linear wide plasma jet is generated. If the gas tube 5 fails to keep a close fit with the reactor wall, on the one hand, it will cause a deviation in the spatial positioning of the vent 6, thereby causing a deflection in the direction of the airflow; on the other hand, it will destroy the stability of the flow field and seriously affect the uniformity of the linear wide plasma.

[0030] The linear wide-band atmospheric pressure microwave plasma source based on a rectangular waveguide provided in this example comprises the following steps: Microwaves enter the first rectangular waveguide 1 and are impedance matched and TE matched by the gradient impedance matcher 2. 10 The compression of the mode electric field is enhanced and then enters the second rectangular waveguide 3; The gas flow enters from the end of the gas pipe 5 and flows evenly into the plasma reactor 4 through the vent hole 6; The microwave electric field in the second rectangular waveguide 3 acts on the gas flow flowing into the plasma reactor 4 and breaks through it, generating a linear wide plasma jet output from the top of the plasma reactor 4 .

[0031] In the above implementation process, the gas flow can be argon, hydrogen, oxygen and other working gases. Different from the previous gas intake method, in this example, the gas intake pipe 5 is directly inserted into the plasma reactor 4, and the gas flow is introduced from both ends of the gas pipe 5. Then, under the action of the gas pressure at both ends, the gas flows out from the vents 6. The uniformity of the gas flow into the plasma reactor 4 is adjusted by setting the aperture, spacing and number of the vents 6, thereby adjusting the generation area and uniformity of the linear wide plasma jet.

[0032] like Figure 4 and Figure 5 The schematic diagram of the electric field distribution of the cross section of the linear wide-band atmospheric pressure microwave plasma source based on the rectangular waveguide of the present embodiment is shown, wherein: Figure 4 The schematic diagram of the electric field distribution from a top view shows the electric field distribution of the plasma reactor 4 along the axial direction; Figure 5It is a schematic diagram of the longitudinal cross-sectional electric field distribution, which intuitively presents the variation trend of the electric field strength in the height direction. It can be seen that the electric field distribution shows significant periodic characteristics, and this periodicity reflects the standing wave characteristics of microwaves, indicating the rationality of the plasma source in this embodiment in terms of microwave mode matching design. Among them, the colors from light to dark (from blue to red) successively represent the change of the electric field strength from low to high. Through analysis, it can be known that the electric field strength reaches the maximum value inside the second rectangular waveguide 3 and is evenly distributed, demonstrating excellent electric field aggregation characteristics. This design can provide sufficient excitation energy for the plasma and significantly reduce the ineffective loss of microwave power. In addition, the entire plasma reactor 4 is located in the region with the highest and evenly distributed electric field strength. When the gas enters from both ends of the intake pipe 5, the high-intensity electric field can ensure that the plasma fully absorbs energy, thereby realizing the efficient excitation of the gas and finally generating a uniform wide-width plasma. Figure 4 and Figure 5 The blue line with the weakest electric field outlined by the red frame in the figure is the wide-width plasma jet generated by this Drude simulation model. When the electron density is high enough, due to the skin effect of the plasma, the microwave field is confined to the surface layer of the plasma, and the plasma boundary is equivalent to a new conductive interface, forming a typical surface wave sustained discharge mode. As can be seen from the simulation results (the part marked by the red frame), the generated wide-width plasma jet shows good uniformity.

[0033] The physical object of the linear wide-width atmospheric pressure microwave plasma source based on a rectangular waveguide in this example was tested. In an argon environment at normal pressure, it successfully achieved stable plasma discharge, had a large effective discharge area, the discharge region presented a uniform glow discharge morphology, and the wide-width microwave plasma was evenly distributed, demonstrating excellent discharge uniformity and stability, which is highly consistent with the wide-width plasma jet predicted by Figure 4 and Figure 5 numerical simulation, providing important technical support for industrial plasma applications.

[0034] The above are only the preferred embodiments of the present application and are not used to limit the present application. Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application..

Claims

1. A linear wide-band atmospheric pressure microwave plasma source based on a rectangular waveguide, characterized in that: It comprises a first rectangular waveguide (1), a gradient impedance matcher (2), a second rectangular waveguide (3), a plasma reactor (4), and a gas tube (5); The height of the second rectangular waveguide (3) is smaller than the height of the first rectangular waveguide (1); The gradient impedance matcher (2) is connected between the first rectangular waveguide (1) and the second rectangular waveguide (3); The plasma reactor (4) is suspended on the second rectangular waveguide (3), perpendicular to the top surface of the second rectangular waveguide (3) and perpendicular to the microwave transmission direction in the second rectangular waveguide (3), and at least part of the plasma reactor (4) extends from the top surface of the second rectangular waveguide (3) into the second rectangular waveguide (3); The gas pipe (5) is horizontally arranged through the portion of the plasma reactor (4) located in the second rectangular waveguide (3), and extends from both sides of the plasma reactor (4) to a predetermined length, and extends to the outside of both sides of the second rectangular waveguide (3); a top array of ventilation holes (6) is provided on the section of the gas pipe (5) located in the plasma reactor (4).

2. The linear wide-band atmospheric pressure microwave plasma source based on rectangular waveguide according to claim 1, characterized in that: One end of the first rectangular waveguide (1) is open for feeding microwaves, and the other end is connected to a gradient impedance matcher (2); One end of the second rectangular waveguide (3) is connected to the gradient impedance matcher (2), and the other end is closed; The gradient impedance matcher (2) is used to achieve impedance matching of microwaves from the first rectangular waveguide (1) to the second rectangular waveguide (3), and to compress the microwaves so as to enhance the field strength inside the microwaves; At least one end of the gas pipe (5) is used for introducing gas flow; The plasma reactor (4) is provided with an opening at the top, and is used to form and output a wide plasma jet.

3. The linear wide-band atmospheric pressure microwave plasma source based on rectangular waveguide according to claim 1, characterized in that: The top surfaces of the first rectangular waveguide (1), the tapered impedance matcher (2), and the second rectangular waveguide (3) are arranged flush with each other.

4. The linear wide-band atmospheric pressure microwave plasma source based on rectangular waveguide according to claim 1, characterized in that: The portion of the plasma reactor (4) located inside the second rectangular waveguide (3) has a predetermined distance from the bottom surface of the second rectangular waveguide (3).

5. The linear wide-band atmospheric pressure microwave plasma source based on rectangular waveguide according to claim 1, characterized in that: The gas pipe (5) is arranged on the front and rear side walls of the plasma reactor (4).

6. The linear wide-band atmospheric pressure microwave plasma source based on rectangular waveguide according to claim 5, characterized in that: The gas pipe (5) is also arranged on the bottom wall of the plasma reactor (4).

7. The linear wide-band atmospheric pressure microwave plasma source based on rectangular waveguide according to claim 1, characterized in that: The gas pipe (5) is cylindrical.

8. The linear wide-band atmospheric pressure microwave plasma source based on rectangular waveguide according to claim 2, characterized in that: Both ends of the gas pipe (5) are used for introducing gas flow.

9. A method for realizing a linear wide-band atmospheric pressure microwave plasma source based on a rectangular waveguide, characterized in that: The method is implemented by using a linear wide-band atmospheric pressure microwave plasma source of a rectangular waveguide as claimed in any one of claims 1 to 8, comprising the steps of: The microwave entering the first rectangular waveguide (1) is subjected to impedance matching and TE matching through the gradient impedance matching device (2). 10 The compression of the mode electric field is enhanced and then enters the second rectangular waveguide (3); The gas flow enters from the end of the gas pipe (5) and flows evenly into the plasma reactor (4) through the vent hole (6); The microwave electric field in the second rectangular waveguide (3) acts on the gas flow flowing into the plasma reactor (4) and breaks through it, thereby generating a linear wide plasma jet, which is output from the top of the plasma reactor (4).

10. The method for realizing a linear wide-band atmospheric pressure microwave plasma source based on a rectangular waveguide according to claim 9, characterized in that: The uniformity of the air flow flowing into the plasma reactor (4) is adjusted by setting the aperture, spacing and number of the vent holes (6), thereby adjusting the generation area and uniformity of the linear wide plasma jet.

Images