JP2005340964A - Microwave supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave supply system wherein a transmission means with an excellent transmission characteristic and almost without causing deterioration or the like to a microwave supplies the stable microwave to a movable microwave processing section which efficiently therein generating plasma. <P>SOLUTION: A microwave transmission section A for transmitting a microwave from a microwave generator 20 to the microwave processing section 10 is provided with a pad flange 30 and a choke flange 40. The radius of the choke flange 40 or the like is defined by a formula of (radius of flange [mm]) ≥ä(length of short side of rectangular waveguide [mm])/2}+ä(guide wavelength [mm])/4}+12 [mm] and a width of a microwave seal face of the choke flnage 40 (outward opposite face 47) is selected to be 12 [mm] or over. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a microwave supply system that supplies microwaves to a microwave processing unit that generates plasma therein. In particular, the present invention relates to a microwave supply system that reduces transmission loss and supplies stable microwaves, and is efficient in the microwave processing unit. The present invention relates to a microwave supply system suitable for generating plasma well.

Chemical vapor deposition (CVD) is a technology for depositing reaction products in the form of a film on the surface of an object to be processed by vapor phase growth in a high-temperature atmosphere using a processing gas that does not react at room temperature. It is widely used in the manufacture of metal and surface modification of metals and ceramics.
Recently, CVD has also been applied as a low-pressure plasma CVD for surface modification of plastic containers, particularly for improving gas barrier properties.

Plasma CVD is a method for growing thin films using plasma. Basically, it is generated by dissociating and combining gases containing a processing gas under a reduced pressure with electric energy of a high electric field. This is a method of depositing the processed material on the processing object by chemical reaction in the gas phase or on the processing object.
The plasma state is realized by glow discharge, corona discharge, arc discharge, etc. For example, as a method of glow discharge, a method using direct current glow discharge, a method using high frequency glow discharge (high frequency plasma CVD). Further, a method using microwave discharge (microwave plasma CVD) is known.

  Among these, the microwave plasma CVD can greatly simplify the structure of the apparatus, and the degree of decompression in the apparatus can be reduced only when the inner surface of the plastic container is processed. Therefore, it is not necessary to maintain the entire apparatus in a high vacuum, which is excellent in terms of ease of operation and productivity.

  As a microwave plasma process for a plastic container, for example, a bottle is disposed in a cylindrical microwave processing unit coaxially with the central axis of the microwave processing unit, and the space inside the bottle and outside the bottle Are simultaneously evacuated, and a processing gas is allowed to flow into the bottle for a predetermined processing time, and a microwave is introduced into the microwave processing unit, the microwave is set to the TM resonance mode, and the plasma is ignited and maintained inside the bottle. Thus, there is a technique for processing a bottle (see, for example, Patent Document 1).

In this plasma processing technique, a microwave generator for supplying a microwave to the microwave processing unit is provided outside the microwave processing unit, and these are connected by a waveguide (for example, , See Patent Document 2).
The waveguide constitutes a microwave transmission path, and generally has a three-dimensional shape in which a radial cross section is formed in a rectangular shape or a circular shape. Examples of the material forming the waveguide include aluminum, copper, and stainless steel.

However, when the microwave processing unit and the microwave generation device are connected by a waveguide, they are fixed, so that it is difficult to move the microwave processing unit.
Here, when the microwave processing unit is used as a performance test (test machine) for the deposited film, it may be used. However, when the microwave processing unit is used as a production machine for mass production of the product with the deposited film, the microwave processing unit is moved. There is a need.

Therefore, for example, it is conceivable to use a high-frequency (microwave) coaxial cable instead of the waveguide (see, for example, Patent Documents 3 and 4).
A coaxial cable is, for example, a cable having a structure in which a core wire is wrapped around with an insulator, the outside is wrapped around with a net such as a copper wire, and a jacket is covered. By connecting this coaxial cable, the high frequency power from the microwave generator can be transmitted to the microwave processing unit. In addition, since the coaxial cable is flexible unlike the waveguide, the plasma processing unit can be moved.
Special table 2001-518685 gazette Japanese Patent Application No. 2003-116301 JP-A-10-303132 JP-A-11-354460

However, since the coaxial cable has poor microwave transmission characteristics as compared with the waveguide, there is a problem in that the microwave cannot be stably sent to the microwave processing unit. As a result, the microwave processing unit could not generate stable plasma efficiently.
Further, the coaxial cable has a problem in that it has a lifetime and is fatigued and deteriorated by repeated movement of the microwave processing section. For this reason, it has been troublesome to replace the coaxial cable which has been fatigued and deteriorated and has reached the end of its life.

  The present invention has been made to solve the above-described problems. A stable microwave is supplied to a moving microwave processing unit by a transmission means having good transmission characteristics and almost no deterioration. An object of the present invention is to provide a microwave supply system that can efficiently generate plasma in the microwave processing section.

  In order to achieve this object, the microwave supply system of the present invention includes a flange connected to the microwave processing unit and a choke flange connected to the microwave generator, and the choke flange is in contact with the flange. Or it is set as the structure arrange | positioned in the position spaced apart from the said flange by predetermined distance.

When the microwave supply system has such a configuration, a flange is connected to the microwave generator, and a choke flange is connected to the microwave processing unit, and the flange and the choke flange are arranged at positions facing each other. Therefore, these flanges can be joined or separated. For this reason, the microwave processing unit can be moved.
Here, the “flange” includes a butt flange and a choke flange. The butt flange includes a flange called a flat flange or a plain flange.

In addition, the choke flange has a choke groove to form a choke circuit, which can reduce or prevent microwave leakage, so transmission loss is small and microwaves can be transmitted stably. Plasma can be generated efficiently in the chamber).
In addition, since a flange such as a choke flange or a butt flange does not bend when the microwave processing unit is moved, fatigue and deterioration hardly occur, and there is no particular life. For this reason, the choke flange or the like can be used for a long time and does not need to be replaced.

Moreover, the microwave supply system of this invention is set as the structure whose predetermined distance is 2 [mm] or less.
If the microwave supply system has such a configuration, the amount of microwave leakage in the gap between the choke flange and the flange opposite to the choke flange can be suppressed, and the microwave can be stably sent to the microwave processing unit. Plasma can be generated well. Also, if there is a gap, there is no risk of rubbing or collision during movement.

  In the microwave supply system of the present invention, the flange and / or the choke flange has a radius of (flange radius [mm]) ≧ {(length of rectangular waveguide short side [mm]) / 2} + {(inside the tube Wavelength [mm]) / 4} +12 [mm].

When the microwave supply system has such a configuration, a gap between the choke flange and the flange facing the choke flange can be allowed.
For example, when the diameters of the choke flange and the flange facing the choke flange are short, microwaves leak from the gap between the flanges, and the transmission efficiency decreases.
On the other hand, when the diameter of the choke flange or the like is a value obtained by the above formula, the gap can be allowed to suppress a decrease in the transmission efficiency of the microwave. For this reason, stable plasma can be generated in the microwave processing section.

  In the microwave supply system of the present invention, the choke flange includes a groove formed concentrically with a circular surface facing the flange, and a microwave seal in which the circular surface is a surface located radially outward of the groove. The microwave sealing surface has a width of 12 [mm] or more.

  If the microwave supply system has such a configuration, a gap between the choke flange and the flange facing the choke flange can be allowed by increasing the width of the microwave sealing surface. Therefore, microwave transmission efficiency is improved, and plasma can be efficiently generated in the microwave processing unit.

In the microwave supply system of the present invention, the microwave processing unit is configured by a chamber for generating plasma.
When the microwave supply system has such a configuration, plasma can be efficiently generated in the chamber by the microwaves stably transmitted through the choke flange or the like.

According to the present invention, the microwave can be stably transmitted by providing the butt flange and the choke flange in the transmission path for transmitting the microwave from the microwave generator to the microwave processing unit.
Moreover, the radius of the choke flange or the like is (flange radius [mm]) ≧ {(length of rectangular waveguide short side [mm]) / 2} + {(inner tube wavelength [mm]) / 4} +12 [mm] By defining the width of the microwave sealing surface of the choke flange to 12 mm or more, the gap between the butt flange and the choke flange can be allowed.
Thereby, in the microwave processing unit, plasma can be generated efficiently.

  Hereinafter, a preferred embodiment of a microwave supply system according to the present invention will be described with reference to the drawings.

First, an embodiment of a microwave supply system of the present invention will be described with reference to FIG.
This figure is a block diagram showing the configuration of the microwave supply system of the present embodiment.

As shown in FIG. 1, the microwave supply system 1 includes a microwave processing unit 10, a microwave generator 20, a butt flange 30, a choke flange 40, and a waveguide 50.
The microwave processing unit 10 is a device that receives a microwave supplied from the microwave generator 20 and performs a predetermined process on an object, and includes, for example, a chamber that generates plasma by microwaves.
The microwave generator 20 is a device that supplies microwaves to the microwave processing unit 10.

The butt flange 30 is provided together with the choke flange 40 in the microwave transmission unit A that transmits the microwave generated by the microwave generator 20 to the microwave processing unit 10. The butt flange refers to a flange having a flat flange portion having a diameter corresponding to the choke flange. The butt flange includes a flange called a flat flange or a plain flange.
The structure of the butt flange 30 is shown in FIGS. 4A is a front view of the butt flange 40, FIG. 2B is a left side view, FIG. 3C is a bottom view, and FIG.

As shown in FIGS. 3A to 3D, the butt flange 30 is provided so as to protrude vertically outward from the center of a disk member 31 having a predetermined thickness and one circular surface 32a of the disk member 31. The rectangular waveguide member 33 is formed.
An opening 35 is formed in the middle of each of the circular surfaces 32a and 32b of the disk member 31 so as to pass therethrough. The opening 35 is formed so as to match the shape of the hollow 34 of the rectangular waveguide member 33 projecting from one circular surface 32a. The hollow 34 of the rectangular waveguide member 33 and the opening 35 of the disk member 31 constitute a microwave waveguide through which the microwave from the microwave generator 20 is transmitted.

The choke flange 40 is a flange that constitutes a choke circuit (series branch circuit with a short-circuited tip) to reduce or prevent leakage of microwaves and increase transmission efficiency.
The structure of the choke flange 40 is shown in FIGS. 4A is a front view of the choke flange 40, FIG. 4B is a right side view thereof, FIG. 3C is a bottom view thereof, and FIG.

As shown in FIGS. 4A to 4D, the choke flange 40 includes a cylindrical member 41 and a rectangular waveguide projecting vertically outward from the middle of one circular surface 42a of the cylindrical member 41. And a member 43.
An opening 45 is formed in the middle of each of the circular surfaces 42a and 42b of the cylindrical member 41 so as to pass therethrough. The opening 45 is formed so as to match the shape of the hollow 44 of the rectangular waveguide member 43 projecting from one circular surface 42a. The hollow 44 of the rectangular waveguide member 43 and the opening 45 of the cylindrical member 41 constitute a microwave waveguide through which the microwave from the microwave generator 20 is transmitted.

Of the two circular surfaces 42 a and 42 b, the circular surface 42 b on which the rectangular waveguide member 43 is not provided is a surface facing the butt flange 30.
As shown in FIG. 3A, a groove (choke groove) 46 formed concentrically with the circular shape of the circular surface 42b is formed on the circular surface 42b.
The groove 46 is formed at a predetermined position at a predetermined depth.
For example, the position where the groove 46 is formed is the next position. When a perpendicular bisector is drawn on the long side of the opening 45 toward the outside of the opening 45, the intersection of the long side of the opening 45 and the vertical bisector is defined as an intersection point a, and the perpendicular bisector Assuming that the intersection point of the groove 46 with the outer circumference circle is the intersection point b, the distance between the intersection point a and the intersection point b is λ / 4 (λ is the wavelength of the microwave passing through the opening 45 (in-tube wavelength)).
The depth of the groove 46 is λ / 4, which is the same as the distance between the intersection point a and the intersection point b.

The radius of the circular surface 42b is defined by the following equation.
(Flange radius [mm]) ≧ {(Length of rectangular waveguide short side [mm]) / 2} + {(In-tube wavelength [mm]) / 4} +12 [mm] (Equation 1)
Here, the “flange radius” corresponds to the radius of the circular surface 42b. The “rectangular waveguide short side” corresponds to the length of each short side in the opening 45 of the cylindrical member 41 of the choke flange 40 or the hollow 44 of the rectangular waveguide member 43. “12 [mm]” corresponds to the width of the outer facing surface 47 (the surface of the circular surface 42b located on the radially outer side with respect to the groove 46, the microwave sealing surface). That is, in the present embodiment, the width of the outer facing surface 47 is 12 [mm] or more.

In terms of specific numerical values, when the length of the short side of the rectangular waveguide is 27 [mm] and the guide wavelength is 157.6 [mm], the radius (flange radius) of the circular surface 42 is as follows. It can be calculated.
(Flange radius [mm]) ≧ {(27 [mm]) / 2} + {(157.6 [mm]) / 4} +12 [mm] → 64.9 [mm]
In this case, the flange radius is 64.9 [mm] or more (the flange diameter is 129.8 [mm] or more).

By setting the width of the outer facing surface 47 to 12 [mm] or more, even if there is a gap between the choke flange 40 and the butt flange 30, leakage of microwaves can be reduced or prevented.
The measurement result of the leakage amount of the microwave when the width of the outer facing surface 47 is set to 12 [mm] or more will be described in [Example 1] described later.

In the circular surface 42b, when the radially inner surface with respect to the groove 46 is an inner facing surface 48, the inner facing surface 48 can be formed at a position recessed with respect to the outer facing surface 47. It can also be formed on the same plane.
When the inner facing surface 48 is formed at a position recessed with respect to the outer facing surface 47, the choke circuit is formed by bringing the outer facing surface 47 into contact with the circular surface 32b of the butt flange 30 to stabilize the microwave. Can be transmitted. This technique is disclosed in, for example, “Wave Choke Flange” described in JP-A-10-224101 and “Choke Flange” described in JP-A-2002-374101.

On the other hand, when the width of the outer facing surface 47 is 12 mm or more, the inner facing surface 48 can be formed on the same plane as the outer facing surface 47.
In addition, in this case, the circular surface 42b of the choke flange 40 and the circular surface 32b of the butt flange 30 can be brought into contact with each other, or can be arranged at a predetermined interval (for example, 2 [mm]).

As shown in FIG. 1, the choke flange 40 and the microwave generator 20 can be connected via a waveguide 50. Further, the butt flange 30 and the microwave processing unit 10 can also be connected via a waveguide.
Further, as shown in the figure, the butt flange 30 and the microwave processing unit 10 can be directly connected without using a waveguide, and between the choke flange 40 and the microwave generator 20. In this case, direct connection can be made without using the waveguide 50.

[Example 1]
Next, Embodiment 1 of the microwave supply system of the present invention will be described.
In this example, the relationship between the diameter of the choke flange 40 (the width of the outer facing surface 47) and the amount of microwave leakage was examined.
In this embodiment, the system configuration is as shown in FIG. That is, the microwave processing part (chamber) 10, the microwave generator 20, the butt flange 30, and the choke flange 40 were prepared.

Choke flanges 40 having the following diameters were prepared. In the present embodiment, for each flange diameter, the length of the short side of the rectangular waveguide is 27 [mm], the guide wavelength is 157.6 [mm], and the width of the outer facing surface 47 is It was set to 12 [mm] or more.
(1) Flange diameter: 130 [mm] (width of outer facing surface 47: 12.1 [mm])
(2) Same diameter: 136 [mm] (Same width: 15.1 [mm])
(3) Same diameter: 140 [mm] (Same width: 17.1 [mm])
(4) Same diameter: 150 [mm] (Same width: 22.1 [mm])

The clearance between the choke flange 40 and the butt flange 30 was set to the following values.
0.2 [mm], 0.5 [mm], 1.0 [mm], 1.5 [mm], 2.0 [mm], 2.5 [mm], 3.0 [mm]
Under these conditions, the amount of microwave leaking from the gap between the choke flange 40 and the butt flange 30 was measured.

The measurement results are shown in FIG.
In the figure, the horizontal axis indicates the gap [mm] between the choke flange 40 and the butt flange 30, and the vertical axis indicates the amount of microwave leakage [mW / cm ² at5cm] when the gap is widened.
As shown in the figure, by increasing the flange diameter of the choke flange 40, the leakage amount of the microwave became 5 [mW / cm ² at5 cm] or less, which is the “safety standard for leakage”.
Thus, by setting the width of the outer facing surface 47 to 12 [mm] or more, the amount of microwave leakage can be suppressed, the gap between the butt flange and the choke flange is allowed, and the microwave can be stably transmitted. It was confirmed that it could be supplied to the processing unit 10.

[Example 2]
Next, a second embodiment of the microwave supply system of the present invention will be described.
In the present embodiment, a change in the amount of microwave leakage due to a difference in the gap between the choke flange 40 and the butt flange 30 and a change in the emission intensity of the plasma in the microwave processing unit 10 (chamber) due to the difference in the gap. I investigated the relationship with.
In this embodiment, the system configuration is as shown in FIG. That is, the microwave processing part (chamber) 10, the microwave generator 20, the butt flange 30, and the choke flange 40 were prepared.

The diameter of the butt flange 30 and the choke flange 40 is 130 [mm], the length of the short side of the rectangular waveguide is 27 [mm], the guide wavelength is 157.6 [mm], and the choke flange 40 and the butt flange 30 are The gap was set to the following values.
0.0 [mm], 0.2 [mm], 0.3 [mm], 0.5 [mm]
Under these conditions, the leakage amount of microwave leaking from the gap between the choke flange 40 and the butt flange 30 and the emission intensity of plasma in the microwave processing unit 10 (chamber) due to the difference in the gap were measured.

The measurement results are shown in FIG.
In the figure, the horizontal axis is the gap [mm] between the choke flange 40 and the butt flange 30, the right vertical axis is the amount of microwave leakage [mW / cm ² at5cm] when the gap is widened, The vertical axis on the left indicates the emission intensity of plasma in the microwave processing unit 10 (chamber) when the gap is widened.
As shown in the figure, the amount of microwave leakage and the light emission intensity of plasma are within the range of good values, but when the gap between the choke flange 40 and the butt flange 30 is widened, the amount of microwave leakage is reduced. On the other hand, there was a tendency that the emission intensity of the plasma was weakened.
As a result, the amount of microwave leakage could be suppressed by setting the gap between the choke flange and the butt flange to 2 mm or less and the width of the outer facing surface 47 to 12 mm or more. Was able to be supplied to the microwave processing unit 10, and it was confirmed that plasma could be generated efficiently.

The preferred embodiment of the microwave supply system of the present invention has been described above. However, the microwave supply system according to the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. It goes without saying that it is possible.
For example, in FIG. 1, the butt flange 30 and the choke flange 40 are provided in a position near the microwave processing unit 10 in the microwave transmission unit A, but they are not necessarily provided in a position close to the microwave processing unit 10. It can also be provided at a position close to the microwave generator 20.
Further, the butt flange 30 and the choke blanke 40 are each formed in a circular outer periphery in FIGS. 2 (a) and 3 (a), but are not limited to a circular shape. It can also be formed. Also, the butt flange can be replaced with a choke flange.

  Since the present invention is a technique for increasing the transmission efficiency of microwaves, the present invention can be used for an apparatus or system having a microwave transmission path.

It is a block diagram which shows the structure of the microwave supply system of this invention. It is the front view (a), side view (b), bottom view (c), and back view (d) which show the structure of a butt flange. It is the front view (a) which shows the structure of a choke flange, a side view (b), a bottom view (c), and a rear view (d). It is a graph which shows the relationship between the width of the clearance gap between a choke flange and a butt flange, and the amount of leakage of a microwave. It is a graph which shows each change of the amount of leakage of a microwave, and the emitted light intensity of the plasma in a chamber with respect to the wide and narrow of the clearance gap between a choke flange and a butt flange.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microwave supply system 10 Microwave processing part 20 Microwave generator 30 Butt flange 40 Choke flange 41 Cylindrical member 42a, 42b Circular surface 43 Rectangular waveguide member 46 Groove 47 Outer facing surface 48 Inner facing surface

Claims (5)

A flange connected to the microwave processing section;
A choke flange connected to the microwave generator,
The microwave supply system, wherein the choke flange is disposed in contact with the flange or at a position separated from the flange by a predetermined distance. The microwave supply system according to claim 1, wherein the predetermined distance is 2 [mm] or less. The flange and / or choke flange radius is
(Flange radius [mm]) ≧ {(Length of short side of rectangular waveguide [mm]) / 2} + {(In-tube wavelength [mm]) / 4} +12 [mm]
The microwave supply system according to claim 1, wherein the value is defined by the following formula. The choke flange is
A groove formed concentrically with a circular surface facing the flange;
A microwave sealing surface which is a surface located on the radially outer side with respect to the groove among the circular surfaces;
The width of this microwave sealing surface is 12 [mm] or more. The microwave supply system according to any one of claims 1 to 3. The microwave supply system according to any one of claims 1 to 4, wherein the microwave processing unit includes a chamber that generates plasma.

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