JP2007157535A - Traveling wave microwave plasma generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a traveling wave microwave plasma generating device capable of forming plasma with wide and uniform density distribution by steadily supplying microwave power. <P>SOLUTION: In the traveling wave microwave plasma generating device, a microwave supply means 1 supplies the microwave power for plasma excitation. A plasma generation means 2 comprising a central conductor 2D and a dielectric tube 2C surrounding the conductor receives the supply of the microwave power from the microwave supply means 1 at one end of the conductor. In an operating state, highly conductive plasma is generated in the outer periphery of the dielectric tube 2C, and the plasma forms an outer conductor of a microwave transmission path. A microwave terminating means 8 is connected with the other end of the central conductor 2D of the plasma generation means 2 and terminates the microwave power passing the microwave transmission path formed by the plasma generation means 2. A plasma source gas supply means 9 supplies plasma source gas to the periphery of the dielectric tube 2C of the plasma generation means 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microwave plasma generator, more specifically, a traveling waveform microwave supplies a microwave power to a plasma generator, thereby forming a uniform plasma density distribution in a large area, and a stable microwave. The present invention relates to a traveling waveform microwave plasma generator capable of generating plasma.

  Microwave plasmas are used in surface treatment, sterilization, vapor deposition and other fields, and there is a demand for stable generation of plasma over a wide area, and many studies have been made. In particular, for uniform cleaning of the surface of a semiconductor wafer, cleaning under a uniform plasma state is indispensable. However, it is difficult to realize a plasma generator for a large area because the electric field strength distribution varies depending on the position due to the restrictions on the antenna arrangement and the presence of standing waves at the time of microwave resonance inside the cavity. there were.

  The surface wave excitation plasma apparatus disclosed in Patent Document 1 is configured to introduce a gas into the chamber from the gas introduction unit 3 and supply microwave power from the slot antenna 6 through the quartz plate window 4. . In this apparatus, the shape of the slot antenna is processed in advance, and the shape and dimension cannot be changed later, so the intensity distribution of the surface wave cannot be finely adjusted. Therefore, it is difficult to make the plasma intensity distribution uniform.

  The plasma processing apparatus disclosed in Patent Document 2 guides a microwave M propagating in a waveguide 2 from a first and a second slot antenna provided with a magnetic field surface H to a microwave introduction window 3, The process gas in the chamber 4 is excited by the wave S to generate a surface wave excited plasma P, and the object to be processed is processed by the plasma P. In this apparatus, the shape of the slot antenna is processed in advance, and the shape and dimension cannot be changed later. Similarly, the intensity distribution of the surface wave cannot be finely adjusted. Therefore, it is difficult to make the plasma intensity distribution uniform.

The plasma processing apparatus disclosed in Patent Document 3 is an apparatus that uses a method of generating surface wave-excited plasma in a region close to a conductor. In particular, a surface wave-excited plasma phenomenon that does not intervene a dielectric is generated in the vicinity of a target made of a conductor. Therefore, the feature is that the target made of a conductor is in direct contact with the gas.
And, the surface wave is not described in the specification at all about active operation as a traveling wave to increase power efficiency.

According to each of the above documents, the structure of the microwave plasma generator is constituted by an antenna or an opening that receives power from the input end and a cavity that confines the microwave in a limited space. Therefore, the microwave is reflected by the wall surface of the cavity and a standing wave is generated inside. The presence of such a standing wave has a different electric field strength distribution depending on the position inside the cavity. For this reason, it is difficult to make the plasma intensity distribution uniform over a wide area.
JP 2000-348898 A JP 2004-235562 A JP 2004-47207 A

  An object of the present invention is to provide a traveling waveform in which a traveling waveform microwave forms a plasma having a large area and a uniform density distribution by supplying microwave power to a plasma generation unit, and can generate a stable microwave plasma. The object is to provide a microwave plasma generator.

In order to achieve the above object, a traveling waveform microwave plasma generator according to claim 1 according to the present invention comprises a microwave supply means for supplying microwave power for plasma excitation,
A plasma having high conductivity is formed on the outer periphery of the dielectric tube in an operating state in which the center conductor and a dielectric tube surrounding the conductor are provided and microwave power is supplied from the microwave supply means to one end of the conductor. And plasma generating means for forming an outer conductor of the microwave transmission path.
Microwave terminating means for terminating microwave power that is connected to the other end of the central conductor of the plasma generating means and that has passed through a microwave transmission path formed by the plasma generating means;
Plasma source gas supply means for supplying a plasma source gas around the dielectric tube of the plasma generating means.

A traveling waveform microwave plasma generator according to a second aspect of the present invention is the apparatus according to the first aspect, wherein the microwave supply means and the plasma generation means, and the coupling portion between the plasma generation means and the microwave termination means. Is a structure in which the central conductor of the plasma generating means is integrally connected electrically or mechanically, and the coupling portion has a structure in which impedance matching in an operating state is established.
According to a third aspect of the present invention, there is provided the traveling waveform microwave plasma generator according to the first aspect, wherein the microwave supply means and the microwave termination means have a waveguide line, and the center of the plasma generation means. Both ends of the conductor are configured to be antenna-coupled within each waveguide.

According to a fourth aspect of the present invention, there is provided the traveling waveform microwave plasma generator according to the first aspect, wherein the plasma source gas is introduced into the central conductor and the dielectric tube of the plasma generator by the plasma source gas supply unit. It arrange | positions spirally in the arbitrary planes in the made container, and is comprised so that planar plasma may be generated.
The traveling waveform microwave plasma generator according to claim 5 of the present invention is the apparatus according to claim 1, wherein the plasma source gas is introduced into the central conductor and the dielectric tube of the plasma generator by the plasma source gas supply unit. It is configured to be bent and folded a plurality of times in an arbitrary plane in the container and generate planar plasma.

A traveling waveform microwave plasma generator according to claim 6 of the present invention comprises a microwave supply means for supplying microwave power for plasma excitation,
A plasma having high conductivity is formed on the outer periphery of the dielectric tube in an operating state in which the center conductor and a dielectric tube surrounding the conductor are provided and microwave power is supplied from the microwave supply means to one end of the conductor. First plasma generating means in which the plasma forms an outer conductor of the microwave transmission path;
In an operating state in which the first plasma generating means is located at a distance from the center conductor and a dielectric tube surrounding the conductor, and is supplied with microwave power from the microwave supplying means at one end of the conductor. Second plasma generating means for forming a plasma having high conductivity on the outer periphery of the dielectric tube, and the plasma forms an outer conductor of the microwave transmission path;
Microwave termination means for terminating microwave power that is connected to the other end of the central conductor of each plasma generation means and that has passed through a microwave transmission path formed by each plasma generation means;
The plasma source gas supply means supplies plasma source gas around the dielectric tube of each plasma generating means.
According to the present invention, the traveling waveform microwave plasma generator according to claim 7,
In addition to the first and second plasma generation means of the sixth aspect, another plasma generation means is additionally provided so that the microwave supply means and the microwave termination means are shared.
A traveling waveform microwave plasma generator according to an eighth aspect of the present invention is the apparatus according to the sixth or seventh aspect, wherein the microwave supply means and the microwave termination means are coupled to the microwave generation means. The part is composed of a waveguide, and the degree of coupling of each coupling part can be adjusted.
A traveling waveform microwave plasma generator according to a ninth aspect of the present invention is the apparatus according to the sixth or seventh aspect, wherein the microwave supply means and the microwave termination means are coupled to the microwave generation means. The part is composed of a coaxial distributor.
A traveling waveform microwave plasma generator according to a tenth aspect of the present invention is the apparatus according to the first, sixth or seventh aspect, wherein a first microwave source and a first load are provided at one end of the microwave generating means. Connected through a first circulator,
A second microwave source and a second load are connected to the other end of the microwave generating means via a second circulator,
The microwave generating means is configured to generate microwave plasma by opposing traveling waves.
According to the eleventh aspect of the present invention, there is provided the traveling waveform microwave plasma generator according to the first, sixth or seventh aspect, wherein the dielectric tube before plasma generation is formed on the surface of the dielectric tube of the plasma generating means. A chevron-shaped protrusion for concentrating the electric field locally on the surface is provided.

According to the configuration of the present invention, there is no reflected wave in the plasma generating means 2 shown in FIG. 1, and only a traveling wave is generated, and this electromagnetic field energy promotes the gasification of the gas. Of course, since no standing wave is generated, the electric field strength does not increase by concentrating on a part of the plasma generating means 2, so that the density of the plasma gas is uniform over a wide area.
In the state in which the gasification of the gas is promoted, since the plasmaizing gas having good conductivity is covered in the vicinity of the outer wall of the dielectric tube 2C of the plasma generating means, the plasmaizing gas is just the same as the conductor outside the coaxial cable. Work. That is, the outer conductor of the microwave transmission path is formed. Therefore, microwave power is efficiently supplied to the plasma generating means 2. Therefore, when matching the characteristic impedance of the circuit described above, a power generating plasma generating apparatus can be realized by setting the characteristic impedance Z of the plasma generating means 2 in consideration of the conductivity of the plasma gas. Become.

Embodiments of an apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing a first embodiment using a single plasma generating means in a traveling waveform microwave plasma generator according to the present invention. In order to facilitate understanding of the internal structure, the dielectric tube of the plasma generating means and a part of the plasma excitation chamber are cut away.
Microwave power for plasma excitation from the microwave power source 6 is supplied via the microwave supply means 1. The plasma generating means 2 includes a center conductor 2D and a dielectric tube 2C made of quartz surrounding the conductor. In an operation state in which microwave power is supplied from the microwave supply means to one end of the conductor, a plasma gas 5 having high conductivity is formed on the outer periphery of the dielectric tube 2C. This plasma gas 5 forms the outer conductor of the microwave transmission path. The microwave termination means 8 includes a termination-side coaxial cable 7. The microwave terminating means 8 is connected to the other end of the central conductor of the plasma generating means 2 and terminates the microwave power that has passed through the microwave transmission path formed by the plasma generating means. The plasma source gas supply means 9 supplies a plasma source gas around the dielectric tube 2C of the plasma generating means 2.

The microwave supply means includes a central conductor 1A of the microwave supply means, an outer conductor tube 1C of the microwave supply means, and a coaxial dielectric 1B of the microwave supply means sandwiched therebetween.
The coaxial dielectric 1B of the microwave supply means is a Teflon (registered trademark) dielectric that has a low dielectric loss relative to the microwave, and its dielectric constant is ε ₁ .

The central conductor 1A of the microwave supply means is connected to the tapered portion 2A of the plasma generating means.
Further, the tapered portion 2A of the plasma generating means is connected to the central conductor 2D of the plasma generating means.
A dielectric tube 2C of plasma generating means made of quartz is disposed outside the central conductor 2D of the plasma generating means connected to the tapered portion 2A of the plasma generating means.
Here, the dielectric constant of the dielectric tube 2C of the plasma generating means made of quartz is ε ₂ .
The outside of the dielectric tube 2C of the plasma generating means is in contact with a plasma gas 5 filling the plasma excitation chamber 4.
The right end of the central conductor 2D of the plasma generating means is connected to the tapered portion 2B of the plasma generating means. The tapered portion 2B of the plasma generating means is connected to the central conductor 1A of the microwave supplying means arranged on the right side. A coaxial dielectric 1B of Teflon (registered trademark) microwave supply means is disposed outside the taper portion 2B of the plasma generating means, and an outer conductor tube 1C of the microwave supply means is disposed further outside.
The plasma gas is supplied from the gas introduction tube 4A of the plasma excitation chamber and is discharged from the gas discharge tube 4B of the plasma excitation chamber. The gas is excited through a dielectric by a microwave electromagnetic field induced in the central conductor 2D of the plasma generating means to be turned into plasma.

FIG. 2 is a schematic cross-sectional view for explaining a connecting portion between the plasma generating means 2 and the microwave supplying means of the embodiment. The coaxial cable forming the microwave supply means 1 is a microwave supply comprising a central conductor 1A of a microwave supply means having a radius r ₁ , a Teflon (registered trademark) dielectric having an inner diameter r ₁ and an outer diameter r _2. It comprises a coaxial dielectric 1B of the means and an outer conductor tube 1C of the microwave supply means.
FIG. 2 particularly shows an example in which Teflon (registered trademark) is used as the dielectric of the tapered portion 2A of the plasma generating means. Although not described in detail here, a structure in which the coaxial dielectric portion having an inner radius r ₁ is air (dielectric constant is ε ₀ ) and the dielectric of the tapered portion of the plasma generating means is made of Teflon (registered trademark) is also possible. is there.
The length of the taper portion 2A of the plasma generating means is 1 and is sufficiently longer than λ / 2. As a result, impedance matching is achieved.
Plasma generating means 2 of the plasma generating means 2 of radius R ₁ centered conductor 2D, the tapered portion 2A and the outer diameter R ₂ of the plasma generating means, and a dielectric tube 2C of the plasma generating means 1 of the inner diameter R _1.
The dielectric tube 2C of the plasma generating means 2 is made of a quartz tube. Its dielectric constant is ε ₂ .
The outside of the dielectric tube 2 </ b> C of the plasma generating means 2 is filled with plasma gas, and the excitation microwave excites the gas to change it into plasma gas 5.

In order for the excitation microwave in the plasma generating means 2 to efficiently supply electromagnetic energy to the plasma gas, a traveling wave is particularly used as the microwave propagating on the surface of the dielectric tube 2C. In order to propagate the traveling wave, as a necessary condition, impedance matching between the coaxial cable of the microwave supply means 1 and the plasma generation means 2 is established.
The plasma generator of the present invention is configured in consideration of this point.
The characteristic impedance Z ₀ of the coaxial cable of the microwave supply means 1 is that of the coaxial dielectric 1B of the microwave supply means constituted by a dielectric of Teflon (registered trademark) where the radius of the central conductor 1A of the microwave supply means is r ₁ . Assume that the inner and outer diameters are r ₁ and r ₂ , and are expressed by the following equations.

Z ₀ = (μ ₀ / ε ₁ ) ^1/2 · ln (r ₂ / r ₁ )

On the other hand, the characteristic impedance Z of the plasma generating means 2 is that the radius of the central conductor 2D of the plasma generating means is R ₁ , the outer diameter of the dielectric tube 2C of the plasma generating means is R ₂ , the inner diameter is R ₁ , and the dielectric constant is ε _2. Is approximately expressed by the following equation.

Z ₀ ≈ (μ ₀ / ε ₂ ) ^1/2 · ln (R ₂ / R ₁ )

As described above, the radius R ₁ of the central conductor 2D of the plasma generating means, the outer diameter R ₂ of the dielectric tube 2C of the plasma generating means, the inner diameter r ₁ and the outer diameter r of the coaxial dielectric 1B of the microwave supplying means. By setting each value of ₂ optimally, the characteristic impedance Z of the plasma generating means 2 can be made equal to the characteristic impedance Z ₀ of the coaxial cable of the microwave supplying means 1.
That is, Z = Z ₀
If this condition is satisfied, there is no reflected wave in the plasma generating means 2 and only a traveling wave is generated, and this electromagnetic field energy promotes the gasification of the gas. Naturally, since no standing wave is generated, the electric field strength does not increase in a part of the plasma generating means 2, so that the density of the plasma gas tends to be uniform over a wide area.
In the state in which the gasification of the gas is promoted, since the plasmaizing gas having good conductivity covers the vicinity of the outer wall of the dielectric tube 2C of the plasma generating means, the plasmaizing gas has the same function as the conductor outside the coaxial cable. do. That is, the outer conductor of the microwave transmission path is formed.
Therefore, microwave power is efficiently supplied to the plasma generating means 2. Therefore, when matching the characteristic impedance of the circuit described above, it is possible to obtain a plasma generator with higher power efficiency by setting the characteristic impedance Z of the plasma generating means 2 in consideration of the conductivity of the plasma gas. become.
In addition, high power can be supplied because of its good consistency.
The outer surface of the dielectric tube 2C of the generating means is in contact with the gas, but when a part of the P point is enlarged, the surface of the quartz tube constituting the dielectric tube 2C has a mountain shape as shown in the figure. Has been processed. This chevron is processed into a ring shape on the circumference of the quartz tube. The height of the mountain is about 100 microns.
When the traveling waveform microwave propagates to the dielectric tube 2C, the electric field of the microwave is concentrated in this mountain-shaped portion, so that the gas is turned into plasma in this portion and the plasma is transmitted to the surroundings. In particular, there are advantages of shortening the time for starting the plasma generation when the power is turned on and facilitating the ignition of the plasma generation.

FIG. 3A is a relationship diagram in the case where the microwave supply unit of the traveling waveform microwave plasma generator using the single plasma generation unit according to the present invention is a waveguide.
The microwave is input to the waveguide 34. A coaxial antenna 31A is disposed inside the waveguide 34 and absorbs microwaves. The coaxial antenna 31 </ b> A is connected to the central conductor 31 </ b> C of the microwave supply means in the plasma generation means 31 and supplies microwave power to the plasma generation means 31. Microwave power is applied to the gas via a coaxial dielectric (quartz) 32 to generate a plasma gas 35. In this case, the microwave operates as a traveling wave because the impedance is matched. The remaining power other than the power consumed for the plasma generation is consumed by an external load (not shown) from the coaxial antenna 31B through the waveguide 34.

First, consider the plasma density distribution on the XY plane (see the right side of FIG. 3B) of the cross section orthogonal to the axis of the microwave plasma generating means shown in FIG. 3A.
The diagram on the right side of FIG. 3B shows the plasma density distribution generated by the plasma generating means 31.
When the position of X is increased from the zero point of the X axis at the height of y = R _{1 and} the plasma density at each position is measured, the plasma density distribution shown as the parameter of y = R ₁ shown in the right diagram of FIG. 3B. become. That is, the plasma density distribution increases from the zero point of the X axis, reaches a maximum in the vicinity of the plasma generating means 31, and decreases again as the distance from the plasma generating means 31 increases.
The plasma density distribution at each point moved in the X-axis direction at a height away from y = 4R ₁ and the plasma generating means 31 is added with a gas diffusion effect as shown in the figure, resulting in a uniform plasma density distribution. It is shown that.
Naturally, the intensity distribution in the Z-axis direction is also uniform.
Therefore, the plasma density distribution is uniform over a wide area at a certain distance.

FIG. 4 is a schematic diagram showing a modification of the first embodiment.
In the traveling waveform microwave plasma generator according to the present invention, the conductor of the plasma generating means and the dielectric tube are spirally arranged in one plane of the plasma generating space. Microwaves from the microwave source 47 are supplied from the input end 41 of the coaxial cable to the central conductor 45 disposed inside the plasma excitation chamber 40. The outer side of the central conductor 45 is covered with a coaxial dielectric (not shown). The microwave excites the gas filling the plasma excitation chamber 40 through the coaxial dielectric, and the gas is turned into plasma. Part of the microwave is consumed by a load (dummy load) 46 disposed at the output terminal 42 of the coaxial cable.

FIG. 5 is a schematic view showing still another modification of the first embodiment. In this modified example, in the traveling waveform microwave plasma generator according to the present invention, the conductor and the dielectric tube of the plasma generating means are arranged in a plane of the plasma generating space with a plurality of parallel portions and a bent back portion connecting them. It is.
The microwave for plasma excitation from the microwave source 55 is supplied from the input end 51 of the coaxial cable to the center conductor 54 disposed inside the plasma excitation chamber 50. The outer side of the center conductor 54 is covered with a coaxial dielectric (not shown). The microwave excites the gas filling the plasma excitation chamber 50 through the coaxial dielectric, and the gas is turned into plasma.
A part of the microwave is consumed by a load (dummy load) 56 disposed at the output terminal portion 52 of the coaxial cable.

A traveling wave microwave plasma generator according to a second embodiment of the present invention uses at least a pair of plasma generating means, and the plasma generated by each plasma generating means cooperates to form a large area plasma generating region. It is.
FIG. 6 shows n examples of generalizing the second embodiment of the traveling waveform microwave plasma generator according to the present invention.
The plasma excitation chamber 60 is supplied with plasma gas from the source gas supply means 630. Microwaves are input from the microwave source 610 to the input 600in of the waveguide. The microwave mode at this time is the TE ₀₁ mode. Inside the waveguide 600, plasma generating means are arranged in parallel as indicated by 61, 62, 63, 64, 65, 66, 6n. An antenna (for example, 61C) of each plasma generating means is arranged on the wall surface of the waveguide 600. The length of each antenna increases in order as it advances from the side closer to the input unit. This is because the microwave power attenuates as it goes deeper into the waveguide 600. In order to compensate for the attenuation, the power entering the plasma generating means is made constant by changing the length of the antenna. It is designed to keep the plasma intensity distribution uniform. An antenna (61D or the like) is also disposed at the end of each plasma generating means, and surplus power is output to the outside from the right waveguide.
The microwave mode generated by each of the plasma generating means is a TEM mode. This microwave propagates along the central axis of the plasma generating means, and the wave becomes a traveling wave by matching the input coaxial and the characteristic impedance of each plasma generating means as described above. Further, as a fine adjustment method for making the electric power input to each plasma generating means uniform, a method of adjusting each tuner (601A to 60nA and 601B to 60nB) arranged on the side surface of the waveguide 600 is used.
With this tuner fine adjustment method, the input power can be finely adjusted. That is, it is possible to further improve the accuracy of uniforming the intensity distribution of the plasma generated in each plasma generating means.

Next, when the guide wavelength of the microwave propagating in the waveguide portion and lambda _g, the interval of the plasma generating means is a λ _g / 2. For example, if the microwave frequency to be excited is 2.450 GHz, λ _g ≈15 cm. The plunger 602 installed in the waveguide is used for adjusting the amplitude of the standing wave of each antenna portion inside the waveguide.
This configuration enables a large-area plasma generator.
The remainder of the microwave power consumed by each of the plasma generating units 61 to 6n is coupled to the output-side waveguide 600 via a coaxial antenna (for example, 61D). The collected remaining power is consumed by the load 620.

ここでＰ（ｚ）はＺの位置における電力の大きさ、Ｐ₀ は前記プラズマ発生手段７０２の左端の入力電力の大きさ、αは減衰定数である。
前記プラズマ発生手段７０２のＺ軸方向の長さをＬとすると、
マイクロ波の電力が前記プラズマ発生手段７０２を右から左に伝播するとその電力は次式で示す割合で減衰する。

ここでＰ（ｚ）はＺの位置における電力の大きさ、Ｐ₀ は前記プラズマ発生手段７０２の右端の入力電力の大きさ、αは減衰定数である。
よってＺ軸のＺの位置における電力は次式で示される。

これによって前記プラズマ発生手段７０２におけるＺ軸方向の電力分布は一様に改善される。同様に前記プラズマ発生手段の７０３、７０４、７０５についても同じ方法で調整することにより、広い面積の領域でプラズマの強度分布が一様になるプラズマ発生装置が可能になる。 FIG. 7 is a circuit diagram that enables bidirectional excitation of the apparatus of the second embodiment of the traveling waveform microwave plasma generator.
This circuit includes two microwave sources 700A and 700B.
Power is supplied to the plasma generating means from both microwave sources. That is, the microwave source 700A supplies microwave power to the circulator 701A.
A traveling-wave microwave propagating in the direction indicated by the solid line of the arrow to the output of the circulator 701A supplies power to the plasma generating means (702, 703, 704, 705). The remaining electric power is supplied to the circulator 701B on the right side, and the electric power of the microwave is consumed by the load (dummy load) 711 by the circulator 701B.
On the other hand, the microwave source 700B supplies microwave power to the circulator 701B.
A traveling-wave microwave propagating to the output of the circulator 701B in the direction indicated by the broken line of the arrow supplies power to the plasma generating means (702, 703, 704, 705). The remaining electric power is supplied to the left circulator 701A, and the electric power of the microwave is consumed by the load (dummy load) 710 by the circulator 701A.
By using this method, the power distribution of the plasma generating means becomes more uniform in the Z-axis direction.
When the microwave power propagates through the plasma generating means 702 from left to right, the power is attenuated at a rate represented by the following equation.

Here, P (z) is the magnitude of power at the position Z, P ₀ is the magnitude of input power at the left end of the plasma generating means 702, and α is an attenuation constant.
When the length of the plasma generating means 702 in the Z-axis direction is L,
When microwave power propagates through the plasma generating means 702 from right to left, the power is attenuated at a rate represented by the following equation.

Here, P (z) is the magnitude of power at the position Z, P ₀ is the magnitude of input power at the right end of the plasma generating means 702, and α is an attenuation constant.
Therefore, the power at the Z position on the Z axis is expressed by the following equation.

As a result, the power distribution in the Z-axis direction in the plasma generating means 702 is uniformly improved. Similarly, by adjusting the plasma generating means 703, 704, and 705 by the same method, a plasma generating apparatus in which the plasma intensity distribution is uniform over a wide area can be realized.

  FIG. 8A is a schematic diagram for explaining the intensity distribution of plasma in the second embodiment, and is a schematic layout diagram showing the relationship between coordinates and the embodiment. FIG. 8B is a diagram showing the plasma density in the x, y plane. The microwave is input to the waveguide 84. A coaxial antenna 81A is disposed inside the waveguide 84 and absorbs microwaves. The coaxial antenna 81 </ b> A is connected to the central conductor 81 </ b> C of the microwave supply means in the plasma generation means 81 and supplies microwave power to the plasma generation means 81. Microwave power is applied to the gas via a coaxial dielectric (quartz) 82, and a plasma gas 85 is generated. In this case, since the impedance matching is performed by the above method, the microwave operates as a traveling wave. The remaining power other than the power consumed for the plasma generation is emitted to the outside through the waveguide 84 from the coaxial antenna 81B. Similarly, the other plasma generating means 81 performs the same operation.

FIG. 8B shows the plasma density distribution in a cross section orthogonal to the axis of the microwave plasma generation means in the above configuration example. As shown in the figure, the density distribution of the plasma gas generated by the plasma generating means 81 is high in the vicinity of the plasma generating means 81. Naturally, the width L at which the peak of the density distribution repeats is the interval between the plasma generating means 81.
It shows that the density distribution becomes uniform with respect to the change in the position in the X-axis direction as it moves away from the plasma generating means 81 in the Y-axis direction. In particular, since the plasma generating means 81 is composed of a plurality, it is clear that the density distribution is set uniformly over a wide region in the X-axis direction. Naturally, the density distribution in the Z-axis direction is also uniform. Therefore, the density distribution is constant over a wide area at positions separated by a certain distance.

FIG. 9 is a schematic diagram for explaining a modification in which a plurality of plasma generating means are coupled using a coaxial distributor in the second embodiment. The microwave is output from the microwave source 91. The microwave is first input to a coaxial distributor 92 that divides the microwave power into two. Further, the microwave is distributed by the coaxial distributor 93 and is eventually divided into four by the coaxial distributor 94. Then, electric power is supplied to the four plasma generating means. If the number of coaxial distributors is increased, the plasma generation means becomes larger.
This method is disadvantageous in that the cost of the coaxial distributor is disadvantageous, but there is no problem that the distance between the plasma generating means explained in FIG. 6 is limited to the width of λ _g / 2, so it is used properly depending on the application. be able to.

  (Modifications, etc.) The embodiment of the traveling waveform microwave plasma generator and its modification have been described above. These can be further modified and combinations can be changed within the scope of the present invention. Although explanation of bidirectional excitation is omitted in the case of one plasma generating means, those skilled in the art can easily realize it by referring to the example of FIG.

  In the microwave plasma generator of the present invention, the traveling waveform microwave forms a uniform plasma density distribution in a large area by supplying microwave power to the plasma generator, and stably generates microwave plasma. It is a traveling waveform microwave plasma generator capable of Recent plasma displays and liquid crystal televisions require large-area glass and films as materials due to the trend toward higher image quality. Cleaning these materials is important to maintain the high quality of the display. The traveling waveform microwave plasma generator of the present invention is relatively inexpensive and has a feature that can cope with this increase in size, and has wide applications in the field of surface treatment techniques using microwaves.

1 is a schematic diagram showing a first embodiment using a single plasma generating means in a traveling waveform microwave plasma generator according to the present invention. It is sectional drawing for demonstrating the connection part at the time of making the plasma generation means and microwave supply means of the said embodiment into a coaxial cable. It is the schematic for demonstrating the coupling | bonding state of the microwave plasma generation means when the microwave supply means of the traveling waveform microwave plasma generator using the said single plasma generation means by this invention is made into a waveguide. It is a graph which shows the intensity distribution of the plasma in the cross section orthogonal to the axis | shaft of a microwave plasma generation means in the Example shown to FIG. 3A. 6 is a schematic view showing a modified example in which the conductor of the plasma generating means and the dielectric tube are spirally arranged in one plane of the plasma generation space in the traveling waveform microwave plasma generator according to the present invention. In the traveling waveform microwave plasma generator according to the present invention, a modification in which a conductor and a dielectric tube of the plasma generator are arranged in a plane of a plasma generation space with a plurality of parallel portions and a bent back portion connecting them is shown. It is a schematic diagram. 6 is a schematic diagram showing an example in which the second embodiment of the traveling waveform microwave plasma generator according to the present invention is further generalized and three or more plasma generating means are used. It is a circuit diagram at the time of transforming the embodiment shown in FIG. 6 into bidirectional excitation. 6 is a schematic diagram showing a relationship between an arrangement and a coordinate system for explaining a plasma intensity distribution in the second embodiment (and a generalized example). It is a figure which shows the plasma density in embodiment shown to FIG. 8A. In the said 2nd Embodiment (and the generalized example), it is the schematic for demonstrating the modification which couple | bonds several plasma generation means using a coaxial divider | distributor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microwave supply means 1A Center conductor of microwave supply means 1B Coaxial dielectric of microwave supply means 1C External conductor tube of microwave supply means 2 Plasma generation means 2A Tapered portion of plasma generation means 2B Taper of plasma generation means Part 2C Dielectric tube of plasma generating means 2D Central conductor of plasma generating means 4 Plasma excitation chamber 4A Gas introduction tube of plasma excitation chamber 4B Gas exhaust tube of plasma excitation chamber 5 Plasma gas 6 Microwave power supply 7 End side coaxial cable 8 Micro Wave terminating means 9 Raw material gas supplying means 31 Plasma generating means 31A Coaxial antenna 31B Coaxial antenna 31C Central conductor of plasma generating means 32 Dielectric tube of plasma generating means 34 Waveguide 35 Plasma gas 40 Plasma excitation chamber 41 Input end 42 Output Termination part 45 Center conductor 4 Load (dummy load)
47 microwave source 50 plasma excitation chamber 51 input end 52 output termination 54 central conductor 60 plasma excitation chamber 61, 62, 63, 64, 65, 66, 6n plasma generation means 61A, 62A central conductors 61C, 61D of plasma generation means Coaxial antenna 600 Waveguide 601A, 602A, 603A, 604A, 605A, 606A, 60nA Tuner 601B, 602B, 603B, 604B, 605B, 606B, 60nB Tuner 602 Plunger 610 Microwave source 620 Load (dummy load)
630 Source gas supply means 700A, 700B Microwave sources 701A, 701B Circulators 702, 703, 704, 705 Plasma generation means 702A Dielectric tube of plasma generation means 702B Central conductor of plasma generation means 81 Plasma generation means 81A, 81B Coaxial antenna 81C Plasma Central conductor of generating means 82 Coaxial dielectric 84 Waveguide 85 Plasma gas 91 Microwave source 92, 93, 94 Coaxial distributor 95 Plasma generating means

Claims (11)

Microwave supply means for supplying microwave power for plasma excitation;
A plasma having high conductivity is formed on the outer periphery of the dielectric tube in an operating state in which the center conductor and a dielectric tube surrounding the conductor are provided and microwave power is supplied from the microwave supply means to one end of the conductor. And plasma generating means for forming an outer conductor of the microwave transmission path.
Microwave terminating means for terminating microwave power that is connected to the other end of the central conductor of the plasma generating means and that has passed through a microwave transmission path formed by the plasma generating means;
Plasma source gas supply means for supplying a plasma source gas around the dielectric tube of the plasma generating means;
A traveling waveform microwave plasma generator comprising:   The coupling portion between the microwave supply unit and the plasma generation unit, and the plasma generation unit and the microwave termination unit is obtained by electrically or mechanically connecting a central conductor of the plasma generation unit, The traveling waveform microwave plasma generating apparatus according to claim 1, wherein the portion has a structure in which impedance matching is established in an operating state.   2. The traveling waveform microwave plasma according to claim 1, wherein said microwave supply means and said microwave termination means have waveguide lines, and both ends of a central conductor of said plasma generation means are antenna-coupled in each of said waveguides. Generator.   The central conductor and the dielectric tube of the plasma generating means are arranged in a spiral shape in an arbitrary plane in the container into which the plasma raw material gas has been introduced by the plasma raw material gas supply means so as to generate a planar plasma. The traveling waveform microwave plasma generator of Claim 1 comprised.   The central conductor and the dielectric tube of the plasma generating means are arranged by being bent and folded several times in an arbitrary plane in the container into which the plasma raw material gas has been introduced by the plasma raw material gas supply means to generate a planar plasma. The traveling waveform microwave plasma generator of Claim 1 comprised so that it may do. Microwave supply means for supplying microwave power for plasma excitation;
A plasma having high conductivity is formed on the outer periphery of the dielectric tube in an operating state in which the center conductor and a dielectric tube surrounding the conductor are provided and microwave power is supplied from the microwave supply means to one end of the conductor. First plasma generating means in which the plasma forms an outer conductor of the microwave transmission path;
In an operating state in which the first plasma generating means is located at a distance from the center conductor and a dielectric tube surrounding the conductor, and is supplied with microwave power from the microwave supplying means at one end of the conductor. Second plasma generating means for forming a plasma having high conductivity on the outer periphery of the dielectric tube, and the plasma forms an outer conductor of the microwave transmission path;
Microwave termination means for terminating microwave power that is connected to the other end of the central conductor of each plasma generation means and that has passed through a microwave transmission path formed by each plasma generation means;
A traveling waveform microwave plasma generator comprising plasma source gas supply means for supplying a plasma source gas around the dielectric tube of each plasma generating means.   7. The traveling waveform microwave plasma generator further includes another plasma generator in addition to the first and second plasma generators, and shares a microwave supply unit and a microwave termination unit. The traveling waveform microwave plasma generator described.   The said microwave supply means and the said microwave termination | terminus means comprised the coupling | bond part with each said microwave generation means with the waveguide, and enabled it to adjust the coupling | bonding degree of each coupling | bond part. Traveling waveform microwave plasma generator.   The traveling waveform microwave plasma generator according to claim 6 or 7, wherein the microwave supply means and the microwave termination means are configured by a coaxial distributor at a coupling portion between the microwave generation means. In the traveling waveform microwave plasma generator of Claim 1, 6, or 7,
A first microwave source and a first load are connected to one end of the microwave generating means via a first circulator,
A second microwave source and a second load are connected to the other end of the microwave generating means via a second circulator,
The microwave generation means is a traveling waveform microwave plasma generator that generates microwave plasma by opposing traveling waves. In the traveling waveform microwave plasma generator of Claim 1, 6, or 7,
A traveling waveform microwave plasma generating apparatus comprising a surface of a dielectric tube of the plasma generating means provided with a mountain-shaped projection for locally concentrating an electric field on the surface of the dielectric tube before plasma generation.

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