JP2009171094A - Directional coupler and plasma generator using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a directional coupler that precisely allows microwaves propagating in a waveguide to diverge, and is miniaturized. <P>SOLUTION: In the directional coupler, the difference between the sum L1+L2 of distance L1 between probes 83A, 83B in the longitudinal direction of a waveguide and the path length L2 of a first transmission path of a microstrip line 82 including the projection length of the probe 83A, and the path length L3 of a second transmission path of the microstrip line 82 including the projection length of the probe 83B coincides with (2n-1)λ/2 (n: an integer, λ: the wavelength of microwaves), and the difference between the sum L1+L3 of the distance L1 and the path length L3 of the second transmission path and the path length L2 of the first transmission path does not coincide with (2n-1)λ/2. The probes 83A, 83B are guided to coupling length holes 84A, 84B having an arc shape with a middle point on a segment for connecting the probes 83A, 83B as a center for movement, and the distance L1 is changed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a directional coupler used in a microwave circuit and a plasma generator provided with the directional coupler.

  2. Description of the Related Art Plasma generators are known that irradiate an object to be processed with plasma and remove organic contaminants on the surface, surface modification, etching, thin film formation or thin film removal. Such a plasma generator is capable of generating plasma at normal temperature and pressure, and microwaves are used to generate the plasma. Usually, in the plasma generator as described above, the power of the microwave generated by the microwave generator is appropriately detected, and the output of the detection is fed back to the microwave generator to stabilize the output of the microwave power. Is planned.

  By the way, when detecting the microwave power, it is necessary to take out a part of the microwave power guided from the microwave generation means to the waveguide. It is common to use a vessel. The directional coupler is required to be downsized from the viewpoint of incorporation into the plasma generator. For example, Patent Document 1 discloses a directional coupler that has been downsized.

In the directional coupler disclosed in Patent Document 1, a printed circuit board having a microstrip line is arranged on a waveguide so that two probes connected to the microstrip line protrude into the waveguide. It is configured. Microwaves flowing in the waveguide from these two probes are taken into the microstrip line on the substrate, and a part of the microwave power traveling in one direction in the waveguide is branched.
JP-A-6-132710

  In the plasma generator as described above, one microwave is selected from the incident microwave guided from the microwave generating means to the waveguide and the reflected microwave returning to the waveguide without contributing to plasma generation. Only (for example, incident microwave) is branched through the directional coupler, and power detection of one of the microwaves is performed. Therefore, in the directional coupler disclosed in Patent Document 1, the amplitudes of the two microwaves taken out from the waveguide through the two probes are adjusted by the length protruding into the waveguides of the two probes. Therefore, only one of the microwaves can be branched by adjusting the amplitude. This branching of only one microwave is realized by a phase difference between two paths propagating through the two microwaves extracted through the two probes.

  By the way, the above-described path for propagating the microwave includes a design error and a temporal error, and the phase difference required for the two paths may not be obtained with high accuracy due to these errors. In this case, if the difference between the two paths can be finely adjusted during actual use, the phase difference error caused by the error can be eliminated. However, the directional coupler disclosed in Patent Document 1 does not have means for finely adjusting the difference between the two paths. As a result, the directional coupler disclosed in Patent Document 1 branches only one microwave with high accuracy. There is a problem that can not be.

  In view of the above problems, an object of the present invention is to divide a microwave propagating in a waveguide with high accuracy, to make a directional coupler that can be miniaturized, and to generate a plasma provided with the directional coupler. To provide an apparatus.

  In order to achieve the above object, a directional coupler according to one aspect of the present invention includes a directional coupling circuit board and a waveguide through which microwaves propagate, and the directional coupling circuit board includes: The first and second transmission paths arranged on the substrate portion and connected to each other at one end are connected to the other ends of the first and second transmission paths in a one-to-one correspondence. A first probe and a second probe protruding into the waveguide at a predetermined distance along the longitudinal direction of the waveguide, which is the direction in which the microwave propagates. A sum L1 + L2 of a predetermined distance L1 between the first and second probes in the longitudinal direction of the tube and a path length L2 of the first transmission path including a protruding length of the first probe; The difference from the path length L3 of the second transmission path including the protruding length of the second probe is (2n-1) λ / (N: integer, λ: wavelength of microwave), the sum L1 + L3 of the predetermined distance L1 and the path length L3 of the second transmission path, and the path length L2 of the first transmission path The difference does not coincide with (2n−1) λ / 2, and the waveguide corresponds to each of the first and second probes of the directional coupling circuit board on a one-to-one basis, and the first A first and second coupling elongated holes for projecting the first and second probes into the waveguide; and the first and second coupling elongated holes are the first and second coupling elongated holes. And has a circular arc shape centering on a midpoint on a line segment connecting the two probes, and the first and second probes are guided and moved by the first and second coupling slots. As a result, the predetermined distance L1 changes.

  In the directional coupler described above, the first and second probes are guided and moved by the first and second coupling elongated holes to change the predetermined distance L1, so that the path length L1 + L2 and the path length L1 + L3 are Fine adjustment is possible. For this reason, said conditions required for the difference of path length can be satisfy | filled completely, As a result, the directionality of a directional coupler can be improved.

  The directional coupling circuit board is further interposed on at least one of the first and second transmission paths, and the first and second transmission paths at a connection point of the first and second transmission paths. It is preferable to have an amplitude attenuating means having an attenuation amount set so that the amplitudes of the microwaves propagating through the above substantially coincide with each other.

  In this case, the amplitudes of the microwaves propagating on the first and second transmission paths are substantially matched at the connection points of the first and second transmission paths, and are opposed to each other along the longitudinal direction of the waveguide. Since the amplitude of one of the two microwaves propagating in the direction can be reliably made zero at the connection point of the first and second transmission paths, only the other microwave can be reliably Can be branched.

  In a plasma generator according to another aspect of the present invention, microwave generation means for generating a microwave, and the microwave generated by the microwave generation means are received, and plasma is generated using energy of the microwave The directional coupler for extracting a part of the microwave propagating through the waveguide disposed between the microwave generating means and the plasma generating means, and the direction A detector that detects the electric power extracted by the sex coupler and outputs the detection result to the microwave generation means, the microwave generation means based on the detection result output from the detector, Controls the microwave output that it generates.

  In the above plasma generator, the amplitude of the reflected microwave of the incident microwave and the reflected microwave propagating in the opposite directions along the longitudinal direction of the waveguide is determined by the connection point of the first and second transmission paths. Therefore, only the incident microwave can be reliably branched. For this reason, since the power of the incident microwave can be detected without being affected by the reflected microwave, the output of the microwave can be controlled based on the detection result, and the output can be stabilized.

  ADVANTAGE OF THE INVENTION According to this invention, the directional coupler which can branch the microwave which propagates a waveguide with sufficient precision, and can be reduced in size, and a plasma generator using the same can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar elements are denoted by the same or similar reference numerals, and description thereof may be omitted.

  FIG. 1 is a partially transparent side view showing the entire configuration of a plasma generator in which a directional coupler according to an embodiment of the present invention is incorporated. The plasma generator PU according to the present embodiment is a device that generates plasma to irradiate a workpiece or the like to be processed with plasma, and can generate plasma at normal temperature and normal pressure using a microwave. . As shown in FIG. 1, the plasma generator PU according to the present embodiment includes first, second, and third waveguides 11, 12, and 13, a microwave generator 20, and a plasma generator 30. The sliding short 40, the circulator 50, the dummy load 60, the stub tuner 70, the directional coupler 10, and the detector 86 are provided.

  The first, second, and third waveguides 11, 12, and 13 are made of a nonmagnetic metal such as aluminum, have an elongated tubular shape with a rectangular cross section, and are generated by the microwave generator 20. A wave is propagated in the longitudinal direction toward the plasma generation unit 30. Each of the first, second, and third waveguides 11, 12, and 13 is connected to each other through the flange portions, and the microwave generator 20 is mounted on the first waveguide 11. . In addition, a stub tuner 70 is assembled in the second waveguide 12, and a plasma generator 30 is provided in the third waveguide 13. Further, as shown in FIG. 1, a circulator 50 and a directional coupler 10 are interposed between the first waveguide 11 and the second waveguide 12, and one end of the third waveguide 13 is disposed. A sliding short 40 is connected to the side.

  Each of the first waveguide 11, the second waveguide 12, and the third waveguide 13 is assembled into a rectangular tube shape using an upper plate, a lower plate, and two side plates made of a metal flat plate. The flange plate is attached to both ends thereof. In addition, you may make it use the rectangular waveguide formed by extrusion molding, the bending process of a plate-shaped member, etc., or an undivided type | mold waveguide irrespective of the assembly of such a flat plate. In addition, the waveguide is not limited to a rectangular cross section, and for example, a waveguide having an elliptical cross section can be used. Furthermore, not only a nonmagnetic metal but a waveguide can be comprised with the various members which have a waveguide effect | action.

  The microwave generator 20 includes, for example, an apparatus main body 21 including a magnetron microwave generation source that generates a microwave of 2.45 GHz, and the microwave generated by the apparatus main body 21 is introduced into the waveguide 10. And a microwave transmitting antenna 22 that emits light. In the plasma generator PU according to the present embodiment, a continuously variable microwave generator capable of outputting, for example, microwave energy of 1 to 3000 W is suitably used as the microwave generator 20.

  The microwave generator 20 has a configuration in which a microwave transmission antenna 22 protrudes from the apparatus main body portion 21 and is fixed in a manner of being placed on the first waveguide 11. Specifically, the apparatus main body 21 is placed on the upper surface plate 11U of the first waveguide 11, and the microwave transmission antenna 22 is inside the first waveguide 11 through the through hole 111 formed in the upper surface plate 11U. The waveguide space 110 is fixed so as to protrude. With this configuration, the microwaves emitted from the microwave transmission antenna 22 are propagated in the first, second, and third waveguides 11, 12, and 13 toward the plasma generation unit 30. The

  The plasma generation unit 30 has eight plasma generation nozzles 31 that protrude from the lower surface plate 13B of the third waveguide 13 so as to be aligned in a line in the left-right direction. The width of the plasma generation unit 30, that is, the arrangement width of the eight plasma generation nozzles 31 in the left-right direction substantially matches the maximum size in the width direction orthogonal to the conveyance direction of the workpiece to be processed by the plasma from the plasma generation unit 30. It is said to be wide. Thereby, plasma processing can be performed on the entire surface of the workpiece (the surface facing the lower surface plate 13B) while conveying the workpiece to be processed. Note that the arrangement interval of the eight plasma generation nozzles 31 is preferably determined according to the wavelength λ of the microwave to be propagated. For example, it is desirable to arrange the plasma generating nozzles 31 at ½ pitch and ¼ pitch of the wavelength λ, and the cross-sectional size of the rectangular waveguides 11, 12, 13 is 2 using microwaves of 2.45 GHz. In the case of .84 inch × 1.38 inch, since λ = 230 mm, the plasma generating nozzles 31 may be arranged at a pitch of 115 mm (λ / 2) or 57.5 mm (λ / 4).

  The plasma generation nozzle 31 has a conductor 32 that penetrates the lower surface plate 13B of the third waveguide 13 and projects into the waveguide space 130 by a predetermined length. The plasma generating nozzle 31 can receive the microwave propagating in the third waveguide 13 through the conductor 32 and can generate plasma using the microwave energy (microwave power).

  The sliding short 40 is provided in order to optimize the coupling state between the conductor 32 provided in each plasma generation nozzle 31 and the microwave propagated inside the third waveguide 13. Therefore, it is connected to one end side of the third waveguide 13 so that the standing wave pattern portion can be adjusted by changing the reflection position of the microwave. In addition, when not using a standing wave, it replaces with the sliding short 40 and the dummy load which has an electromagnetic wave absorption effect | action is attached.

  The sliding short 40 includes a casing structure having a rectangular cross section similar to that of the third waveguide 13, and houses a cylindrical reflection block 42 therein. The standing wave pattern portion is optimized by the movement of the reflection block 42.

  The circulator 50 is composed of, for example, a waveguide-type three-port circulator with a built-in ferrite column. Of the microwaves once propagated toward the plasma generator 30, the circulator 50 returns without being consumed by the plasma generator 30. The incoming reflected microwave is directed to the dummy load 60 without returning to the microwave generator 20. By arranging such a circulator 50, the microwave generator 20 is prevented from being overheated by the reflected microwave.

  The dummy load 60 is a water-cooled (or air-cooled) radio wave absorber that absorbs the reflected microwave and converts it into heat. The dummy load 60 is provided with a cooling water circulation port for circulating cooling water therein, and heat generated by heat-converting the reflected microwave is exchanged with the cooling water. .

  The stub tuner 70 is for impedance matching between the second waveguide 12 and the plasma generating nozzle 31, and is arranged in series on the upper surface plate 12 U of the second waveguide 12 at a predetermined interval. Two stub tuner units 70A to 70C are provided. The three stub tuner units 70 </ b> A to 70 </ b> C have the same structure and have a stub 71 protruding into the waveguide space 120 of the second waveguide 12.

  The stub 71 provided in each of the stub tuner units 70 </ b> A to 70 </ b> C can be adjusted in its protruding length into the waveguide space 120. The protruding lengths of the stubs 71 are determined by searching for a point where the power consumption by the conductor 32 is maximized (a point where the reflected microwave is minimized) while monitoring the microwave power. Such impedance matching is executed in conjunction with the sliding short 40 as necessary.

  Next, the directional coupler 10 according to the present embodiment will be described. As shown in FIG. 1, the directional coupler 10 according to the present embodiment is disposed between the circulator 50 and the second waveguide 12, and is connected from the micro generator 20 to the plasma generator 30. A part of the incident microwave power propagating through the first, second, and third waveguides 11, 12, and 13 is branched. FIG. 2 is an exploded perspective view showing the configuration of the directional coupler 10 according to the present embodiment.

  The directional coupler 10 according to the present embodiment includes a directional coupler waveguide 80 and a directional coupling circuit board 81. Similar to the first, second, and third waveguides 11, 12, and 13, the directional coupler waveguide 80 is made of a nonmagnetic metal such as aluminum and has a long tubular shape with a rectangular cross section. Then, the microwave generated by the microwave generator 20 is propagated in the longitudinal direction toward the plasma generator 30. Further, the directional coupler waveguide 80 is a reflection that returns to the microwave generator 20 side without being consumed in the plasma generator 30 among the microwaves once propagated toward the plasma generator 30. Microwaves are similarly propagated.

  As shown in FIG. 2, the directional coupler waveguide 80 of the present embodiment has two long coupling holes 84A and 84B. Each of the two coupling elongated holes 84A and 84B has a one-to-one correspondence with each of the two probes 83A and 83B of the directional coupling circuit board 81, and the corresponding probes 83A and 83B can be inserted. ing. The directional coupling circuit board 81 has the probes 83A and 84B of the directional coupling circuit board 81 protruding into the waveguide space inside the directional coupler waveguide 80 through the coupling elongated holes 84A and 84B. It is placed on the waveguide 80. The coupling elongated holes 84A and 84B have an arc shape, and the probes 83A and 83B are guided by the coupling elongated holes 84A and 84B and can move in the clockwise direction. Of course, the directional coupling circuit board 81 simultaneously rotates clockwise as the probes 83A and 83B move. The shapes of the coupling elongated holes 84A and 84B and the effects resulting from the shapes will be described in detail later.

  As shown in FIG. 2, the directional coupling circuit board 81 has a microstrip line 82 having a predetermined path. The microstrip line 82 is connected to the two probes 83A and 83B, and a part of each of the incident microwave and the reflected microwave propagating in the directional coupler waveguide 80 is the probe 83A. It is transmitted to the microstrip line 82 through 83B.

  Next, the coupling elongated holes 84A and 84B of the directional coupler waveguide 80 and the microstrip line 82 of the directional coupling circuit board 81 will be described in more detail. FIG. 3 is a diagram for explaining the coupling elongated holes 84A and 84B of the directional coupler waveguide 80 and the microstrip line 82 of the directional coupling circuit board 81. FIG.

  As shown in FIG. 3, the coupling elongated holes 84 </ b> A and 84 </ b> B of the directional coupler waveguide 80 are separated by a predetermined distance L <b> 1 along the longitudinal direction of the directional coupler waveguide 80. Similarly, the probes 83A and 83B of the directional coupling circuit board 81 are also separated by the distance L1, and the inside of the directional coupler waveguide 80 is passed through the coupling elongated holes 84A and 84B of the directional coupler waveguide 80. A part of each of the incident microwave and the reflected microwave propagating into the waveguide space 80 and propagating in the directional coupler waveguide 80 is transmitted to the microstrip line 82. In the present embodiment, a detector 86 capable of detecting microwave power is connected to the coupling point X of the microstrip line 82, and the microwave power output via the coupling point X of the microstrip line 82 is detected. It can be detected.

  The microstrip line 82 has a first transmission path from the tip P1 of the probe 83A to the coupling point X, and a second transmission path from the tip P3 of the probe 83B to the coupling point X. In each of the first and second transmission paths, attenuators 85A and 85B as amplitude attenuating means are interposed. Each of the attenuators 85A and 85B can set the attenuation amount independently of each other, and the amplitudes of incident microwaves and reflected microwaves transmitted on the first and second transmission paths on which the respective attenuators are disposed. Is attenuated according to the set attenuation amount. Further, the shape of the microstrip line 82 is formed such that the first transmission path of the microstrip line 82 has a predetermined distance L2 and the second transmission path has a predetermined distance L3.

  For example, the attenuators 85A and 85B may be constituted by three chip resistors. As shown in FIG. 3, the attenuator 85A has three chip resistors R11, R12, and R13 connected in a π-type, and the attenuator 85B has three chip resistors R21, R22, and R23 connected in a π-type. It is configured. The attenuators 85A and 85B can realize a desired attenuation amount by changing the resistance values of the chip resistors R11, R12, R13, R21, R22, and R23 constituting each of the attenuators 85A and 85B. The conditions required between the attenuation amounts of the attenuators 85A and 85B will be described later.

  Here, of the incident microwaves propagating in the waveguide 80 for the directional coupler, the incident microwaves transmitted to the microstrip line 82 through the probe 83A are transmitted from the tip P1 of the probe 83A via the position P2. Take the first path to the connection point X. The path length of the first path is L2. Further, the incident microwave transmitted to the microstrip line 82 through the probe 83B propagates through the directional coupler waveguide 80 from the tip P1 of the probe 83A when the tip P1 of the probe 83A is used as a reference. A second path is reached which reaches the tip P3 of the probe 83B and reaches the coupling point X via the tip P3. The path length of the second path is L1 + L3.

  On the other hand, of the reflected microwaves propagating in the waveguide 80 for the directional coupler, the reflected microwaves transmitted to the microstrip line 82 through the probe 83B are the third from the tip P3 of the probe 83B to the coupling point X. Take the journey. The path length of the third path is L3. Further, the reflected microwave transmitted to the microstrip line 82 through the probe 83A propagates through the directional coupler waveguide 80 from the tip P3 of the probe 83B when the tip P3 of the probe 83B is used as a reference. A fourth path is reached which reaches the tip P1 of the probe 83A and reaches the coupling point X via the tip P1 and the position P2. The path length of the fourth path is L1 + L2.

  Next, the condition required between the distances L1, L2, and L3 and the condition required between the attenuation amounts of the attenuators 85A and 85B will be described. In the directional coupler 10 according to the present embodiment, since the power of the incident microwave is detected without detecting the power of the reflected microwave propagating through the waveguide 80 for the directional coupler, the distance L1 described above is used. , L2, L3 and the attenuations of the attenuators 85A, 85B satisfy the conditions described below. The wavelengths of the incident microwave and the reflected microwave propagating in the directional coupler waveguide 80 are both λ.

First, as described above, the path to the coupling point X of the microstrip line 82 in the reflected microwave includes the third path and the fourth path. The path length of the third path is L3, and the path length of the fourth path is L1 + L2. Here, the path length difference between the third path and the fourth path is (2n−1) λ / 2, and the reflected microwaves transmitted through the third path and the fourth path are respectively If the amplitudes are equal, the reflected microwaves transmitted through each other cancel each other, and no reflected microwave is output at the coupling point X. That is, the following two conditions are required for the reflected microwave.
(1) The path length difference between the path length L3 of the third path and the path length L1 + L2 of the fourth path is (2n−1) λ / 2 (n is an integer), that is, the third path, The reflected microwaves transmitted on each of the four paths are out of phase.
(2) The amplitudes of the reflected microwaves transmitted through the third path and the fourth path are equal.

  The above condition (2) can be satisfied by separately adjusting the attenuation amounts of the attenuators 85A and 85B.

Next, as the path to the coupling point X of the microstrip line 82 in the incident microwave, as described above, the first path and the second path described above can be cited. The path length of the first path is L2, and the path length of the second path is L1 + L3. Here, if the path length difference between the first path and the second path does not satisfy at least (2n−1) λ / 2, the incident microwaves transmitted through the first path and the second path do not cancel each other and are coupled. At point X, the incident microwave is output. That is, the conditions required for incident microwaves are as follows.
(3) The path length difference between the path length L2 of the first path and the path length L1 + L3 of the second path is not (2n−1) λ / 2 (n is an integer).

  As the condition (3) above, for example, the path length difference between the path length L2 of the first path and the path length L1 + L3 of the second path may be nλ (n is an integer). In this case, the incident microwaves transmitted through the first path and the second path are in phase, and the amplitude of the incident microwave output at the coupling point X propagates through the directional coupler waveguide 80. As a result, the coupling degree of the directional coupler 10 is improved.

  For example, the distance L1 between the coupling elongated holes 84A and 84B of the waveguide 80 for directional coupler is λ / 4, and the distance L2 of the first transmission path and the distance L3 of the second transmission path of the microstrip line 82 When the difference is λ / 4, the path length difference between the path length L3 of the third path and the fourth path L1 + L2 is λ / 2, and is transmitted through the third path and the fourth path, respectively. The reflected microwave is out of phase. On the other hand, the path length of the path length L2 of the first path and the path length L1 + L3 of the second path is equal, and the incident microwaves transmitted through the first path and the second path are in phase. Become.

  The detector 86 detects the incident microwave power output via the coupling point X of the microstrip line 82 and outputs the detection result to the device main body 21 of the microwave generator 20. The apparatus main body 21 controls the microwave generation source based on the detection result, and stabilizes the output of the microwave generated from the microwave generation source.

  Next, a specific structure of the directional coupling circuit board 81 will be described. FIG. 4 is a plan view showing a schematic configuration of the directional coupling circuit board 81. In the directional coupling circuit board 81 shown in FIG. 4, the microstrip line 82 is branched at the coupling point X, the probe 83A is connected to the tip of one branch path (first transmission path), and the other A probe 83B is connected to the tip of the second branch path (second transmission path). Specifically, one end of each of the three microstrip lines 82A, 82B, and 82C constituting the microstrip line 82 is coupled at the coupling point X. The microstrip line 82A serving as the first transmission path is for transmitting the microwave taken through the probe 83A connected to the other end to the coupling point X, and the microstrip line serving as the second transmission path. 82B is for transmitting the microwave taken in through the probe 83B connected to the other end to the coupling point X. The microwaves transmitted on each of the first and second transmission paths are combined at the coupling point X, and the combined microwaves are transmitted on the microstrip line 82C, which is the third transmission path, and the detector. 86.

  Attenuators 85A and 85B are provided on each path of the microstrip lines 82A and 82B. The attenuators 85A and 85B attenuate the microwaves transmitted on the paths by a preset attenuation amount. The attenuator 85A is configured by connecting three chip resistors R11, R12, and R13 in a π type, and the attenuator 85B is configured by connecting three chip resistors R21, R22, and R23 in a π type. A ground line 87 is disposed in the vicinity of the microstrip lines 82A and 82B, and chip resistors R12, R13, R22, and R23 constituting the attenuators 85A and 85B are grounded through the ground line 87.

  As described above, the attenuators 85A and 85B have the effect of attenuating the amplitude of the microwave power transmitted from the probes 83A and 83B, but also have the following effects. The characteristic impedance of the transmission path changes at the coupling point X where the plurality of microstrip lines 82A, 82B, and 82C shown in FIG. 4 are coupled. For this reason, from the probe 83A and the probe 83B to the microstrip lines 82A and 82B. A part of the microwave transmitted above is reflected at the coupling point X, transmitted again on the microstrip lines 82A and 82B, and returned to the probe 83A and probe 83B side. Further, a part of the microwaves returned to the probe 83A, 83B side is reflected by the other end of the microstrip lines 82A, 82B and transmitted again to the coupling point X side. Here, let us consider a case where the attenuators 85A and 85B are not present. When the reflection is repeated as described above, the reflected wave due to the reflection as described above is added to the microwave that should be transmitted on the microstrip lines 82A and 82B, and the microwave taken in from the probes 83A and 83B is changed. It becomes difficult to detect accurately.

  On the other hand, in the present embodiment, attenuators 85A and 85B are interposed on the respective paths of the microstrip lines 82A and 82B, and the attenuators 85A and 85B attenuate the reflected waves caused by such reflection. Can do. Therefore, the influence of the reflected wave as described above on the output of the microwave power at the coupling point X detected by the detector 86 can be suppressed at the same time.

  Next, the shape of the coupling long holes 84A and 84B of the waveguide 80 for directional coupler and the effects resulting from the shape will be described. FIG. 5 is a view of the coupling elongated holes 84A and 84B of the directional coupler waveguide 80 as viewed from above. As described above, the coupling elongated holes 84A and 84B have an arc shape centered on the point O, and the probes 83A and 84B are guided by the coupling elongated holes 84A and 84B and can move in the clockwise direction. It is. Point O is a midpoint on a line segment connecting the probes 83A and 84B.

  Here, the rotation angle θ is set as shown in FIG. When the rotation angle θ is 0 degree, the distance between the probe 83A and the probe 83B is L1. On the other hand, the distance gradually decreases as the rotation angle θ increases. That is, the distance L1 ′ between the probe 83A and the probe 83B at the rotation angle θ is L1 cos θ, and the distance between the probe 83A and the probe 83B can be changed by changing the rotation angle θ. it can. FIG. 6 shows the relationship between the rotation angle θ and the shortening rate of the distance between the probe 83A and the probe 83B. As shown in FIG. 6, it can be seen that the shortening rate decreases as the rotation angle θ increases. The shortening rate is the ratio of the distance after rotation to the distance when the rotation angle θ is 0 degree.

  On the other hand, as described above, the directional coupling circuit board 81 according to the present embodiment is required to satisfy the conditions required between the distances L1, L2, and L3. By the way, each value of the distances L1, L2, and L3 usually includes a design error at the time of designing the directional coupling circuit board 81 and a temporal error after long-term use. For this reason, in actual use, it is difficult to completely satisfy the above-described conditions without fine adjustment of the path length such as the path length of the first path and the path length of the second path. There are many cases. Therefore, in the present embodiment, by changing the distance between the probe 83A and the probe 83B, that is, the length of the L1, the path length of the first path described above, The path length such as the path length of the path can be finely adjusted, and by doing so, the conditions required between the distances L1, L2, and L3 can be completely satisfied, and as a result, the directional coupler The directionality of 10 can be improved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, For example, the following embodiment can be taken.

  In the directional coupling circuit board 81 according to the above-described embodiment, the attenuators 85A and 85B are interposed in the first transmission path and the second transmission path of the microstrip line 82, respectively. An attenuator may be interposed only in one of the path and the second transmission path.

  A directional coupler and a plasma generator using the same according to the present invention include an etching processing apparatus and a film forming apparatus for a semiconductor substrate such as a semiconductor wafer, a glass substrate or printed substrate cleaning processing apparatus such as a plasma display panel, and a medical device. The present invention can be suitably applied to a sterilization apparatus for equipment and the like, a protein decomposition apparatus, and the like.

It is a partially transparent side view which shows the whole structure of the plasma generator which concerns on embodiment of this invention. It is a disassembled perspective view which shows the structure of the directional coupler 10 which concerns on this Embodiment. It is a figure for demonstrating the waveguide 80 for directional couplers, and the directional coupling circuit board 81. FIG. 3 is a plan view showing a schematic configuration of a directional coupling circuit board 81. FIG. It is the figure which looked at the coupling long holes 84A and 84B of the waveguide 80 for directional couplers from the top. It is a figure which shows the relationship between rotation angle (theta) and the shortening rate of the distance between the probe 83A and the probe 83B.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Directional coupler 11 1st waveguide 11U, 12U Upper surface board 12 2nd waveguide 13 3rd waveguide 13B Lower surface board 20 Microwave generator 21 Apparatus main-body part 22 Microwave transmission antenna 30 Plasma Generator 31 Plasma generating nozzle 32 Conductor 40 Sliding short 42 Reflecting block 50 Circulator 60 Dummy load 70 Stub tuner 70A, 70B, 70C Stub tuner unit 71 Stub 80 Directional coupler waveguide 81 Directional coupling circuit boards 82, 82A , 82B, 83C Microstrip lines 83A, 83B Probes 84A, 84B Coupling elongated holes 85A, 85B Attenuator 86 Detector 87 Ground lines 110, 120, 130 Waveguide space 111 Through hole

Claims (3)

A directional coupling circuit board;
A waveguide through which microwaves propagate,
The directional coupling circuit board includes a board part, first and second transmission paths arranged on the board part, each end of which is connected to each other, and each of the first and second transmission paths. A first and a second are connected to the other end in a one-to-one correspondence, and protrude into the waveguide at a predetermined distance along the longitudinal direction of the waveguide, which is the direction in which the microwave propagates. A probe and
The sum L1 + L2 of the predetermined distance L1 between the first and second probes in the longitudinal direction of the waveguide and the path length L2 of the first transmission path including the protruding length of the first probe And the path length L3 of the second transmission path including the protruding length of the second probe is (2n-1) λ / 2 (n: integer, λ: wavelength of microwave) And the difference between the sum L1 + L3 of the predetermined distance L1 and the path length L3 of the second transmission path and the path length L2 of the first transmission path is equal to (2n-1) λ / 2 Do not
The waveguide corresponds to each of the first and second probes on the directional coupling circuit board on a one-to-one basis, and the first and second probes protrude into the waveguide. And a side surface portion on which a second coupling slot is formed,
The first and second coupling elongated holes have an arc shape centering on a midpoint on a line segment connecting the first and second probes, and the first and second probes are The directional coupler is characterized in that the predetermined distance L1 is changed by being guided and moved by the first and second coupling elongated holes.   The directional coupling circuit board is further interposed on at least one of the first and second transmission paths, and the first and second transmission paths at a connection point of the first and second transmission paths. 2. The directional coupler according to claim 1, further comprising amplitude attenuating means having an attenuation amount set so that the amplitudes of the microwaves propagating through each of the microwaves substantially coincide with each other. Microwave generation means for generating microwaves;
Plasma generating means for receiving the microwave generated by the microwave generating means and generating plasma using energy of the microwave;
The directional coupler according to claim 1 or 2, wherein a part of the microwave propagating through the waveguide disposed between the microwave generation unit and the plasma generation unit is extracted.
A detector that detects the electric power extracted by the directional coupler and outputs the detection result to the microwave generation means;
The microwave generation unit controls the output of the microwave generated by itself based on the detection result output from the detector.

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