KR20030064125A - High efficient-atmospheric microwave plasma system - Google Patents

Abstract

PURPOSE: A high efficiency atmospheric pressure microwave plasma system is provided to increase the efficiency of the energy transmission by having the double resonance structure and inserting the resonance tuner into the resonance. CONSTITUTION: A high efficiency atmospheric pressure microwave plasma system includes a power block(202), a magnetron(204), a controller(206), an isolator(208), a directional coupler(210), a triple rod tuner(212), a plasma reaction block(220) and an automatic transfer system(230). The plasma reaction block(220) includes a first resonator(221), a second resonator(222), a plasma reaction tube(223) and a resonance tube(224). The high efficiency atmospheric pressure microwave plasma system is capable of exciting various modes in response to the hole to transmit the energy from the first resonator(221) to the second resonator(222) or the position or the type of the antenna.

Description

High efficient-atmospheric microwave plasma system

The present invention relates to an atmospheric pressure plasma system, and more particularly, to a high-efficiency atmospheric microwave plasma system having a high energy transfer efficiency by using a dual resonator.

In general, plasma refers to an ionized gas state composed of ions, electrons, radicals, and the like, which is generated by a very high temperature, a strong electric field, or an RF electromagnetic field. Particularly, plasma generation by glow discharge is performed by free electrons excited by direct current (DC) or high frequency electric field (RF). The excited free electrons collide with gas molecules to generate active species such as ions, radicals, and electrons. active species). And such active species physically or chemically act on the surface of the material to change the surface properties. In this way, intentionally changing the surface properties of the material by the active species (plasma) is called 'surface treatment'.

Representative methods for generating a plasma include a dielectric barrier discharge (Dielectric Barrier Discharge) for generating a plasma using a dielectric film at room temperature / atmospheric pressure (760torr) and a microwave plasma system using a microwave.

As shown in FIG. 1, the conventional microwave torch, which is a microwave plasma system, controls the magnitude of the voltage applied to the magnetron 104 and the magnetron 104 as a source of microwaves. A controller 106 for controlling the output, a power supply 102 for generating the high voltage required for the magnetron 104, for protecting the magnetron 104 from reflection of microwaves generated in the magnetron 104 and propagating through the waveguide. Isolator 108, directional coupler 110 capable of detecting outputs of incidence and reflection directions, 3-stub tuner 112 for impedance matching, waveguide The tapered waveguide 114, a tapered continuous waveguide that increases the electric field strength of the TE01 mode excited by the waveguide, Contained consists of a hole in the waveguide 116, quartz tube 118, a gas supply device (not shown), the ignition electrode (igniter) (120) or the like.

By the way, the conventional microwave plasma system that can operate at normal pressure has been using a simple torch (torch) form, rather than a resonant structure, but such a torch type has a problem that the plasma flame is limited to a very small area. In order to overcome this problem, when a resonant structure is adopted, there is a problem in that discharge characteristics are very sensitively affected by changes in resonator dimensions, structures included in the resonator, and a medium. In other words, when the oscillation frequency of the magnetron changes depending on the pressure or temperature or the output of the microwave, various plasma parameters are changed to escape the stable operating point, which makes it difficult to apply to a wide pressure range and various process conditions. .

In order to solve the above problems, the present invention provides a high-efficiency atmospheric pressure microwave plasma system having a double resonator structure and including a resonator tuner in a reactor, which can be adapted to process conditions to form a more stable plasma. The purpose is to provide.

1 is a schematic diagram showing a conventional microwave plasma system;

2 is a schematic view showing an atmospheric microwave plasma system according to the present invention;

3 is a cross-sectional view showing a first embodiment of the plasma reaction unit according to the present invention;

4 is a perspective view showing a first embodiment of a plasma reaction unit according to the present invention;

5 shows an example of a resonator tuner according to the present invention;

6 is a cross-sectional view showing a second embodiment of the plasma reaction unit according to the present invention;

* Explanation of simple symbols for main parts of the drawings

202: power supply 204: magnetron

206: controller 208: separator

210: Directional coupler 212: Triple bar tuner

220: plasma reaction unit 221: primary resonator

222: secondary resonator 223: plasma reaction tube

224: resonator tuner

In order to achieve the above object, the system of the present invention, in the microwave plasma system having a microwave generating unit for generating a microwave, and a plasma reaction unit for generating a plasma from the reaction gas by receiving the microwave The plasma reactor may include a plasma reaction tube made of a dielectric material through which the reaction gas passes, and a resonator tuner included in a dual resonator structure to optimize a resonance mode and a frequency.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, the atmospheric pressure microwave plasma system according to the present invention includes a microwave generator, an separator (208), a directional coupler (210), a triple bar tuner (212), and a plasma reaction. The unit 220 is composed of an automatic transfer system 230 for a continuous process.

The microwave generating unit supplies power to the magnetron 204 for oscillating microwaves in the 2.45 GHz band, which is the energy source of the plasma, and the controller 206 and the magnetron 204 for controlling the output of the magnetron 204. It consists of a high voltage power supply (202) to supply the oscillation of microwaves in the 2.45 GHz band. In this case, as the microwave generation source, Klystron which can change the wavelength in addition to the magnetron 204 may be used, and all energy sources in other microwave frequency regions may be used according to the application. In addition, the type of microwave signal can be selected according to the purpose, whether it is a pulse or continuous output.

The separator 208 serves to protect the reflected microwaves from returning to the microwave generator to damage the magnetron 204, and the directional coupler 210 detects the strength of the microwave traveling in the forward and reverse directions. This configuration is basically used in the existing microwave plasma system, so further description thereof will be omitted.

As illustrated in FIG. 2, the structural features distinguished by the present invention include a plasma type reactor 220 having dual coupling resonators 221 and 222 having high coupling efficiency, and a suitable type of resonator tuner in the resonator. The position 224 can be well matched to various resonance characteristic changes that occur when the conditions of the medium or microwave source change. Therefore, according to the present invention, stable plasma generation is possible in a wide pressure range from low pressure of several tens of mtorr to normal pressure (1 atm). And the plasma reaction tube 223 maintains the mode selected in the design, and the microwave is well Dielectric is used to transmit and can be arbitrarily selected according to the application considering the relative dielectric constant and temperature characteristics as design variables. At this time, if the dielectric constant is too large as the material of the plasma reaction tube 223, the energy stored in the dielectric becomes large, so that the dielectric constant is 2 or more and less than 10, and the melting point is high (for example, 600 degrees). Choose materials that do not deform even at hundreds of degrees.

Referring to FIG. 2, microwaves oscillated from commercially available microwave sources (eg, magnetrons or klystrons), including microwave bands ranging from several hundred MHz to several tens of GHz, in addition to the commonly used 2.45 GHz band. Is propagated along the waveguide and delivered to the microwave resonators 221 and 222 including the plasma reaction tube 223 to generate plasma discharge. The waveguide propagation path of the microwave includes a separator 208, a directional coupler 210, and a triple bar tuner 212 for impedance matching. Here, the separator 208 serves to protect the magnetron 204 when the microwave is reflected back from the reactor 220. Directional coupler 210 is a device for sensing the microwave strength in the direction of the tuner 212 and the reflected direction is essential for impedance matching in the direction of minimizing the output of the reflected wave when the process variable changes. . The triple bar tuner 212 serves to tune the impedance of the tuner to the microwave generator so that the maximum microwave output is delivered into the plasma reactor 220. In place of the triple bar tuner 212, other types of tuners, such as the E-H tuner, are often used in high-power microwave systems.

The plasma reactor 220 illustrated in FIG. 2 includes a primary resonator 221, a secondary resonator 222, a plasma reaction tube 223, and a resonator tuner 224. Various modes can be excited depending on the shape, location or method of the hole or antenna for energy transfer from the primary resonator 221 to the secondary resonator 222. In the embodiment of the present invention, the first embodiment in which the resonator tuner 224 of the plasma reactor 220 is included in the reaction tube 223 and the resonator tuner 224 may include the secondary resonator 222 and the reaction tube 223. The description will be made separately according to the second embodiment located in between.

The reaction tube 223 commonly uses a dielectric material that is well resistant and transparent at high temperatures such as quartz or sapphire, and various dielectrics may be selected according to a purpose.

The shapes of the primary resonator 221 and the secondary resonator 222 may be variously designed such as a cylindrical shape, a rectangular parallelepiped, a sphere, a flat plate, and a concave mirror shape to suit an application purpose, but in the embodiment of the present invention, a cylindrical shape is provided for convenience. Based on the dual resonator structure of the operation principle of the present invention will be described.

The dual resonator structure of the present invention requires a primary resonator (an outer coaxial cavity (221)) serving as a kind of mode filter to maximize mode purity and maximize energy transfer efficiency. Since the energy is transmitted to the central secondary resonator 222 including the reaction tube 223 through a hole or antenna of a predetermined position.

Referring to FIG. 2, the microwaves transmitted from the waveguide 221a resonate in a mode determined in the design of the primary resonator 221, and energy installed on a common wall of the primary resonator 221 and the secondary resonator 222. Finally, the secondary resonator that will cause the plasma discharge through the antenna of the coupling slot or loop shape or probe shape for the delivery finally reaches the secondary resonator to cause the plasma discharge 225 in the reaction tube 223. do. At this time, the inside of the secondary resonator 222 includes a plasma reaction tube 223 which is a dielectric tube and a disc-shaped or rod-shaped resonator tuner 224. The structure of the microwave resonator affects the resonator response characteristics of the dielectric or conductor, that is, the resonant frequency, mode, Q factor, etc., but is more sensitive to conductors such as metals. ) Is preferably made of a metal, it is included in the plasma reaction tube 223 is not affected even if the temperature is greatly increased, it is necessary to select a material having a low reactivity with the reactor used.

Figure 3 is a cross-sectional view showing a first embodiment of the plasma reaction unit according to the present invention (a) is a side view and (b) is a plan view. 4 is a perspective view of a first embodiment of a plasma reaction unit according to the present invention.

3 and 4, in the structure of the plasma reaction unit of the first embodiment, both the primary resonator 221 and the secondary resonator 222 are cylindrical, and the primary resonator 221 is the secondary resonator 222. The diameter of the secondary resonator 222 is greater than or equal to or higher than that of the primary resonator 221, and the reaction tube 223 is positioned inside the secondary resonator 222. The resonator tuner 224 is located inside.

5 is a diagram showing an example of a resonator tuner according to the present invention, (a) is a disc-shaped resonator tuner with a hollow central portion, (b) is a disc-shaped resonator tuner with a rod, and (c) is a disc A resonator tuner with a hole in it. (D) is a cylindrical resonator tuner, and (E) is a polygonal resonator tuner.

Referring to FIG. 5, (a) is a resonator tuner of a type suitable for the second embodiment, and (b) to (e) are resonator tuners of a type suitable for the first embodiment. In particular, a columnar tuner may be inserted in the center of the resonator for the purpose of capacitor tuning in place of the discs, such as (d) and (d), as shown in (c). At this time, the cross section of the bar tuner may have an arbitrary polygonal shape, and the tuner in any form should be manufactured to enable vertical movement in the axial direction of the resonator.

Figure 6 is a cross-sectional view showing a second embodiment of the plasma reaction unit according to the present invention, (a) is a side cross-sectional view, (b) a planar cross-sectional view.

Referring to FIG. 6, the structure of the plasma reactor 220 of the second embodiment is similar to that of the first embodiment of the first resonator 221 and the second resonator 222, but the position of the resonator tuner 224 is plasma-reacted. There is a difference in that it is located outside the tube 223. That is, in the structure of the second embodiment, the plasma reaction tube 223 is positioned at the center, and the resonator tuner 224 is positioned between the plasma reaction tube 223 and the secondary resonator 222 to tune. In this case, in the case of the disc-shaped resonator tuner 224, the resonator length tuning effect can be appropriately utilized only when the resonator cross section other than the plasma reaction tube 223 is filled.

That is, when the diameter of the reaction tube 223 is similar to the diameter of the secondary resonator 222, it is preferable that the outer diameter of the disc tuner is made to fit the inner diameter of the reactor as in the first embodiment, and the reaction tube ( If the diameter of the second resonator 222 is much smaller than the diameter of the second resonator 222 and the volume of most of the second resonator 222 lies outside the reaction tube 223, the center of the disc tuner 224 as in the second embodiment is used. A hole having the same size as the outer diameter of the reaction tube 223 is designed so that the outer diameter of the disk tuner 224 fits the inner wall of the secondary resonator 223.

As described above, the microwave plasma system of the present invention is a dual resonator type with high energy coupling efficiency, and the conventional low pressure system can be utilized because an atmospheric pressure plasma discharge can be stably maintained under various process variables through a tuner in the resonator. It is possible to obtain higher density neutral active species than in one case, thereby increasing the efficiency and thus the processing speed. That is, by using the atmospheric pressure microwave plasma system of the present invention, it is possible to obtain a high-density neutral active species incomparable with the conventional low pressure system, so that it can be variously applied to coating, synthesis process, waste gas purification, etc. have.

In addition, since the conventional atmospheric pressure plasma system discharges only in a very limited area, the area that can be processed during coating or synthesis process is limited, and uniformity is greatly reduced. However, when using the dual resonator structure including the tuner of the present invention, a diameter of about 10 cm The abnormal discharge area can be widened, and stable surface treatment is possible by compensating for various error factors that may occur in the actual process through the tuner.

Claims (7)

In the microwave plasma system having a microwave generating unit for generating a microwave, and a plasma reaction unit for generating a plasma from the reaction gas by receiving the microwave, The plasma reaction unit A primary resonator receiving the microwave through a waveguide; A secondary resonator for causing a plasma to be microwaved from the primary resonator; Coupling means for transferring microwaves between the primary resonator and the secondary resonator; A plasma reaction tube made of a dielectric and positioned in the secondary resonator to cause a plasma reaction from a reaction gas by the microwave; And And a resonator tuner positioned in the reaction tube or outside the reaction tube to optimize a resonance mode and frequency. The microwave plasma system according to claim 1, wherein the resonator tuner is one of a disk or a porous disk with an upright support, or a cylindrical or polygonal rod-shaped tuner. The microwave plasma system of claim 1, wherein an outer diameter of the resonator tuner is a shape that matches a diameter of a plasma reaction tube. The method of claim 1 wherein the resonator tuner is And a cross section of a space between the plasma reaction tube and a resonator adjacent to the plasma reaction tube. The microwave plasma system according to claim 1, wherein the coupling means is a hole or an antenna. The microwave plasma system of claim 1, wherein the plasma reaction tube has a dielectric constant in a range of 2 to 10 and a melting point of 600 degrees or more. According to claim 1, wherein the shape of the primary resonator and the secondary resonator is characterized in that any one of the form of a cylinder, a rectangular parallelepiped, a flat plate, a sphere in order to improve the input frequency and resonance characteristics of the microwave Wave Plasma System.