Plasma generating apparatus and plasma processing apparatus

Abstract

The present invention is provided with: an outer conductor (29) which is a conductive waveguide having an opening (34) on one end side; a first dielectric (31) that extends along the main axis of the outer conductor (29) inside the outer conductor (29), is connected to a microwave supply cable (5) for supplying microwaves, and propagates the supplied microwaves to one end side; and a second dielectric (33) that is disposed so as to close the opening (34) and generates plasma using the microwaves propagated by the first dielectric (31).

Description

Technical Field

[0001] The present invention relates to a plasma generating device for generating plasma and a plasma processing device equipped with the plasma generating device for performing plasma processing on a workpiece. Background Art

[0002] In the manufacturing process of semiconductor products, liquid crystal panels, etc., plasma is used in surface cleaning, etching, CVD treatment, etc. In addition to these, surface modification treatment, water repellent treatment, etc. using plasma are also performed on the object to be processed (hereinafter collectively referred to as "workpiece") in a wide range of fields.

[0003] The device for plasma processing a workpiece includes a microwave generating unit for generating microwaves, a plasma generating device for generating plasma using microwave energy, and a plasma processing unit connected to the plasma generating device and accommodating the workpiece. The plasma processing unit is, for example, a metal vacuum chamber, and one or more plasma generating devices are connected to the plasma processing unit.

[0004] As a plasma generating device used in a plasma processing device, there is known a device (coaxial irradiation device) having a coaxial tube structure and generating plasma at the tip (for example, Patent Document 1). Fig.17 or Fig.18 As shown, the conventional plasma generating device 100 of Patent Document 1 includes a central core 101, an outer shield 102, a connecting mechanism 105, and a dielectric 107. The central core 101 is composed of a conductive rod-shaped member and extends along the main axis AP of the plasma generating device 100. The central core 101 corresponds to a so-called internal conductor in the plasma generating device 100.

[0005] The outer shield 102 is a cylindrical member having electrical conductivity and is arranged so as to surround the central core 101. The outer shield 102 corresponds to a so-called external conductor in the plasma generating device 100. Fig.17 The base end side of the outer shield 102 (on the left side) is formed with an opening. Fig.17 The central core 101 and the outer shield 102 are closed by a partition wall 106. A propagation medium 103 for propagating microwave energy is provided between the central core 101 and the outer shield 102. An example of the propagation medium 103 is air.

[0006] The connection mechanism 105 connects the microwave generating unit (not shown) and the plasma device 100. As an example, Fig.17As shown, the connection mechanism 105 is disposed at a portion of the side wall of the outer shield 102 close to the partition wall 106. A microwave transmission cable 108 extending from a microwave generating unit (not shown) is guided into the plasma generating device 100 through the connection mechanism 105 formed as an opening.

[0007] The dielectric 107 is composed of an insulator that propagates microwaves, and is disposed so as to close the opening on the tip side of the outer shield 102. The dielectric 107 is connected to the central core 101. The dielectric 107 connects the propagation medium 103 of the plasma generating device 100 and the internal space of the plasma generating part. The outer surface 109 of the dielectric 107 is tapered and becomes thinner from the base end side to the tip end side of the outer shield 102.

[0008] In the conventional plasma generating device 100, plasma is generated by microwaves output from a microwave generating unit. That is, microwave energy input from a microwave transmission cable 108 is propagated into the interior of the plasma generating device 100 via a connecting mechanism 105. The microwave energy is propagated into the dielectric 107 in the plasma generating device 100, and the gas in contact with the outer surface 109 of the dielectric 107 is excited to generate plasma.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application No. 2018-530128 Summary of the invention

[0012] Problem that the invention aims to solve

[0013] However, in the case of the conventional example having such a structure, there are the following problems.

[0014] As a first problem in the conventional example, dielectric breakdown is likely to occur when a high-power microwave is input into the conventional plasma generator 100. Therefore, it is difficult for the conventional plasma generator 100 to generate high-power plasma.

[0015] The following reasons are conceivable as the causes of the problem of insulation breakdown in the conventional device. That is, in the conventional plasma generating device 100, since the conductive central core 101 is arranged at the center of the cylindrical outer shield 102, the insulation distance is the distance P1 from the inner surface of the outer shield 102 to the surface of the central core 101. That is, the insulation distance is limited to a distance shorter than the radius of the outer shield 102, so insulation breakdown is easy to occur in the plasma generating device 100. In order to ensure a sufficient insulation distance to avoid the occurrence of insulation breakdown, it is necessary to increase the diameter of the outer shield 102. Therefore, it is very difficult to both avoid insulation breakdown and miniaturize the plasma generating device 100.

[0016] As a second problem in the conventional example, the following aspects can be cited: heat is easily accumulated inside and difficult to release to the outside in the conventional plasma generating device 100. That is, in the plasma generating device 100, the output of microwaves needs to be suppressed to be low in order to suppress the accumulation of heat, so it is more difficult to generate high-output plasma.

[0017] The following reasons are conceivable as the reasons why the problem of heat accumulation is easy to occur in conventional devices. That is, in the plasma generating device 100, the portion where the central core 101 contacts the outer shield 102 is limited to a very small area. The central core 101 directly contacts the outer shield 102 only at the base end of the plasma generating device 100. Therefore, it is difficult to efficiently discharge the heat (Joule heat) generated on the surface of the central core 101 to the outside of the plasma generating device 100.

[0018] As a third problem in the conventional example, the manufacturing cost of the plasma generating device 100 is high. That is, in the plasma generating device 100, if the dielectric 107 is made into a simple cylindrical shape, the impedance matching property is reduced. In order to improve the impedance matching property in the plasma generating device 100, the outer surface 109 of the dielectric 107 needs to be processed into a tapered shape. That is, the manufacturing cost of the plasma generating device 100 increases due to processing the outer surface 109 of the dielectric 107.

[0019] In addition, in order to further increase the impedance of the plasma generating device 100, it is necessary to Fig.18 As shown, not only the outer surface 109 of the dielectric 107 but also the inner surface 110 of the dielectric 107 in contact with the propagation medium 103 is processed into a tapered shape. When the inner surface 110 is processed into a tapered shape in addition to the outer surface 109, the manufacturing cost of the plasma generation device 100 is further increased.

[0020] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plasma generating device and a plasma processing device capable of achieving an increase in plasma output and a reduction in the size of the device.

[0021] Solutions for solving problems

[0022] The present invention adopts the following structure to achieve such an object.

[0023] That is, the plasma generating device of the present invention is characterized in that:

[0024] The plasma generating device comprises:

[0025] A conductive waveguide having an opening at one end;

[0026] A first dielectric member extending inside the waveguide along the main axis of the waveguide, connected to a microwave supply cable for supplying microwaves, and propagating the supplied microwaves toward the one end side; and

[0027] The second dielectric member is disposed so as to close the opening and generates plasma using the microwave propagated by the first dielectric member.

[0028] (Function and Effect) According to this structure, a conductive waveguide having an opening at one end is used, and inside the waveguide, a first dielectric member extends along the main axis of the waveguide. In addition, the opening of the waveguide is closed by a second dielectric member, and microwaves propagated toward one end by the first dielectric member are received by the second dielectric member, and the second dielectric member generates plasma using the microwaves.

[0029] That is, the plasma generating device of the present invention has a waveguide structure as a whole, and has no conductor inside. By not having an internal conductor, it is possible to avoid the situation where the insulation distance of the plasma generating device is shortened due to the presence of the internal conductor, and thus, it is possible to avoid the occurrence of insulation breakdown even when high-output microwaves are supplied. Therefore, it is possible to more reliably prevent the occurrence of insulation breakdown and improve the output of plasma in the plasma generating device.

[0030] In addition, since the insulation distance of the plasma generator is prevented from being shortened due to the presence of the internal conductor, the occurrence of dielectric breakdown can be more reliably avoided even when the diameter of the waveguide is shortened. In other words, the plasma generator can be miniaturized while more reliably avoiding the occurrence of dielectric breakdown.

[0031] Furthermore, in the above invention, preferably, the first dielectric member extends along the main axis of the waveguide so as to fill the inside of the waveguide.

[0032] (Function and Effect) According to this structure, the first dielectric member fills the inside of the waveguide. That is, the entire surface of the first dielectric member is in contact with the waveguide. By filling the inside of the waveguide with the first dielectric member, the first dielectric member that propagates microwaves is in contact with the waveguide as an external conductor over a large area. Therefore, the heat generated in the first dielectric member can be efficiently conducted to the waveguide and released to the outside of the plasma generating device. As a result, even when a high-output microwave is supplied, it is possible to avoid heat accumulation in the first dielectric member, so that the temperature of the plasma generating device can be prevented from increasing and the output of the plasma in the plasma generating device can be increased.

[0033] Furthermore, in the above invention, it is preferable that the first dielectric member includes a relative dielectric constant buffer portion for relieving a change in relative dielectric constant at a connection portion with the microwave supply cable.

[0034] (Function and Effect) According to this structure, the first dielectric member has a relative dielectric constant buffer. The relative dielectric constant buffer mitigates the change in relative dielectric constant at the connection portion between the microwave supply cable and the first dielectric member. By connecting the microwave supply cable and the first dielectric member via the relative dielectric constant buffer, the change in relative dielectric constant of the portion from the microwave supply cable to the first dielectric member becomes smaller. Therefore, by having the relative dielectric constant buffer, the decrease in impedance matching caused by the rapid change in relative dielectric constant can be avoided.

[0035] Furthermore, in the above invention, it is preferred that

[0036] The relative dielectric constant buffer portion is a recessed portion formed in the first dielectric member.

[0037] The microwave supply cable is inserted in the direction in which the recess extends.

[0038] (Function and Effect) According to this structure, a recess is formed in the first dielectric member, and the microwave supply cable is inserted into the recess. In this case, in the area of ​​the recess where the microwave supply cable is inserted, the area filled with the first dielectric member and the area filled with gas around the microwave supply cable are mixed. That is, the relative dielectric constant at the recess where the microwave supply cable is inserted is lower than the relative dielectric constant of the first dielectric member and higher than the relative dielectric constant of the gas around the microwave supply cable. Therefore, the change in the relative dielectric constant of the portion from the microwave supply cable to the first dielectric member becomes smaller. Therefore, by performing a simple design of forming a recess, the decrease in impedance matching caused by a sharp change in the relative dielectric constant can be avoided.

[0039] Furthermore, in the above invention, it is preferred that

[0040] The relative dielectric constant buffer portion is a connecting member made of a material having a lower relative dielectric constant than that of the first dielectric member.

[0041] The first dielectric member is connected to the microwave supply cable via the connecting member.

[0042] (Function and Effect) According to this structure, a connection member composed of a material having a lower relative dielectric constant than the first dielectric member is provided, and the first dielectric member is connected to the microwave supply cable via the connection member. Since the connection member is composed of a material having a lower relative dielectric constant than the first dielectric member, the change in the relative dielectric constant of the portion from the microwave supply cable to the first dielectric member becomes smaller. Therefore, by arranging the connection member between the microwave supply cable and the first dielectric member, which is a simple structure, the decrease in impedance matching caused by a sharp change in the relative dielectric constant can be avoided.

[0043] Furthermore, in the above invention, it is preferable that the first dielectric member includes a second relative dielectric constant buffer portion for buffering a change in relative dielectric constant at a connection portion with the second dielectric member.

[0044] (Function and Effect) According to this structure, the first dielectric member includes the second relative dielectric constant buffer portion. The second relative dielectric constant buffer portion mitigates the change in relative dielectric constant at the connection portion between the first dielectric member and the second dielectric member. By connecting the first dielectric member and the second dielectric member via the second relative dielectric constant buffer portion, the change in relative dielectric constant of the portion from the first dielectric member to the second dielectric member becomes smaller. Therefore, by including the second relative dielectric constant buffer portion, the decrease in impedance matching caused by the rapid change in relative dielectric constant can be more reliably avoided.

[0045] In order to achieve such an object, the present invention may adopt the following configuration.

[0046] That is, the plasma processing apparatus of the present invention is characterized in that:

[0047] The plasma processing device comprises:

[0048] a microwave supplying unit that supplies microwaves;

[0049] a plasma generating unit that generates plasma using the microwaves supplied from the microwave supplying unit; and

[0050] a plasma processing unit for processing a workpiece using the plasma generated by the plasma generating unit,

[0051] The plasma generating unit is the plasma generating device according to any one of claims 1 to 5.

[0052] (Function and Effect) According to this structure, microwaves are supplied to the plasma generating device of the present invention to generate plasma, and the plasma is used to perform plasma treatment on the workpiece. Therefore, the effect of the present invention can be achieved in the device for performing plasma treatment on the workpiece. That is, for the plasma generating device of the present invention, even if high-output microwaves are supplied, the occurrence of insulation breakdown and the like can be more reliably avoided, so that the occurrence of insulation breakdown and the like can be prevented while achieving plasma treatment of the workpiece with high-output plasma.

[0053] Effects of the Invention

[0054] According to the plasma generating device and the plasma processing device of the present invention, a conductive waveguide having an opening at one end is used, and inside the waveguide, a first dielectric member extends along the main axis of the waveguide. In addition, the opening of the waveguide is closed by a second dielectric member, and microwaves propagated toward one end by the first dielectric member are received by the second dielectric member, and the second dielectric member generates plasma using the microwaves.

[0055] That is, microwaves are supplied to a waveguide having no conductor inside but a dielectric member to generate plasma. By not having an internal conductor, it is possible to avoid the situation where the insulation distance is shortened due to the presence of the internal conductor, and thus, it is possible to avoid the occurrence of insulation breakdown even when high-output microwaves are supplied. Therefore, it is possible to more reliably prevent the occurrence of insulation breakdown and improve the output of plasma in the plasma generating device.

[0056] In addition, since it is possible to avoid the situation where the insulation distance is shortened due to the presence of the internal conductor, the occurrence of insulation breakdown can be more reliably avoided even when the diameter of the waveguide is shortened. That is, it is possible to more reliably avoid the occurrence of insulation breakdown and to miniaturize the plasma generating device. Thus, a plasma generating device and a plasma processing device with improved plasma output and miniaturized device can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a schematic diagram illustrating the overall structure of the plasma processing apparatus of Example 1.

[0058] Figure 2 It is a longitudinal sectional view explaining the structure of the plasma generating portion of the first embodiment.

[0059] Figure 3 It is a perspective view illustrating the structure of the plasma generating portion of Example 1.

[0060] Figure 4 This is a diagram showing a state where a plasma generating unit and a plasma processing unit of the plasma processing apparatus according to Example 1 are combined.

[0061] Figure 5 This is a diagram showing a state where a first dielectric, a second dielectric, and an external conductor are combined in the plasma generating portion of Example 1.

[0062] Figure 6 1 and 2 are diagrams showing changes in relative dielectric constant in a plasma generating unit of a comparative example. (a) is a longitudinal cross-sectional view showing the base end side of the plasma generating unit, and (b) is a graph showing changes in relative dielectric constant in the input direction of microwaves on the base end side of the plasma generating unit.

[0063] Figure 7 The figures show the change of relative dielectric constant in the plasma generating part of Example 1. (a) is a longitudinal cross-sectional view showing the base end side of the plasma generating part, and (b) is a graph showing the change of relative dielectric constant in the input direction of microwaves on the base end side of the plasma generating part.

[0064] Figure 8 1 and 2 are diagrams for explaining the effects achieved by the structure of Example 1. (a) is a longitudinal sectional view showing the heat dissipation efficiency in a conventional example, and (b) is a longitudinal sectional view showing the heat dissipation efficiency in Example 1.

[0065] Fig. 9 (a) is a diagram showing a modified example in which the tip of the second dielectric is cylindrical, and (b) is a diagram showing a modified example in which the tip of the second dielectric is tapered and becomes thicker toward the tip side.

[0066] Fig.10 It is a longitudinal sectional view for explaining the structure of the plasma generating portion of the second embodiment.

[0067] Fig.11 1 and 2 are diagrams showing changes in relative dielectric constant in the plasma generating section of Example 2. (a) is a longitudinal sectional view showing the base end side of the plasma generating section, and (b) is a graph showing changes in relative dielectric constant in the input direction of microwaves on the base end side of the plasma generating section.

[0068] Fig.12 It is a longitudinal sectional view for explaining the structure of the plasma generating portion of the third embodiment.

[0069] Fig.131 and 2 are diagrams showing changes in relative dielectric constant in the plasma generating section of Example 3. (a) is a longitudinal sectional view showing the base end side of the plasma generating section, and (b) is a graph showing changes in relative dielectric constant in the input direction of microwaves on the base end side of the plasma generating section.

[0070] Fig.14 It is a longitudinal sectional view for explaining the structure of a plasma generating portion according to a modified example.

[0071] Fig.15 It is a longitudinal sectional view for explaining the structure of a plasma generating portion according to a modified example.

[0072] Fig.16 It is a longitudinal sectional view for explaining the structure of a plasma generating portion according to a modified example.

[0073] Fig.17 It is a longitudinal sectional view explaining the structure of a plasma generating device of a conventional example.

[0074] Fig.18 It is a longitudinal sectional view explaining the structure of a plasma generating device of a conventional example.

[0075] Fig.19 1 and 2 are diagrams showing changes in relative dielectric constant in a plasma generating unit of a modified example. (a) is a longitudinal cross-sectional view showing a plasma generating unit, and (b) is a graph showing changes in relative dielectric constant in a microwave input direction of the plasma generating unit. DETAILED DESCRIPTION

[0076] [Example 1]

[0077] Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. Figure 1 This is a schematic diagram of the plasma processing apparatus 1 of the first embodiment.

[0078] <Description of overall structure>

[0079] The plasma processing device 1 of the first embodiment includes a microwave generating unit 3, a microwave supply cable 5, a plasma generating unit 7 and a plasma processing unit 9. Figure 1 and Figure 4 In FIG. 1 , a longitudinal sectional view of the plasma processing unit 9 is shown.

[0080] The microwave generating unit 3 can oscillate microwaves of a specific frequency by making the frequency variable. In the present embodiment, the microwave generating unit 3 oscillates microwaves of 2.45 GHz. The microwave supply cable 5 is connected to the microwave generating unit 3 and the plasma generating unit 7, respectively, and transmits the microwaves oscillated from the microwave generating unit 3 and supplies them to the plasma generating unit 7.

[0081] The plasma generating unit 7 generates plasma at the tip portion using the energy of the microwave supplied from the microwave generating unit 3. The plasma generating unit 7 is connected to the plasma processing unit 9, and the tip portion where the plasma is generated is configured to contact the internal space L of the plasma processing unit 9.

[0082] In this embodiment, the plasma processing device 1 is provided with three plasma generating units 7, but the number of the plasma generating units 7 can be changed appropriately. The plasma processing device 1 is provided with microwave supply cables 5 corresponding to the number of the plasma generating units 7. The microwave supply cables 5 are connected to each plasma generating unit 7. The structure of the plasma generating unit 7 will be described later. The plasma generating unit 7 is equivalent to the plasma generating device in the present invention.

[0083] The plasma processing unit 9 performs plasma processing on the workpiece W. That is, the plasma processing unit 9 performs a predetermined processing on the workpiece W using the plasma generated by the plasma generating unit 7. Examples of the workpiece W include semiconductor products, liquid crystal panels, and solar cell arrays.

[0084] The plasma processing unit 9 includes a chamber 11 and a workpiece holding unit 13. The chamber 11 includes a connecting plate 15 such as Figure 1 As shown, the chamber 11 is connected to the exhaust device 19 via the exhaust flow path 17 having the electromagnetic valve 16. When the exhaust device 19 is operated, the internal space L of the chamber 11 is degassed and depressurized.

[0085] The chamber 11 is connected to a gas supply device 23 via a supply flow path 21 having an electromagnetic valve 20. The gas supply device 23 supplies a predetermined gas G to the internal space L of the chamber 11. Examples of the gas G supplied by the gas supply device 23 include rare gases such as argon gas, oxygen, and the like.

[0086] In addition, the chamber 11 includes an opening and closing door 25. The opening and closing door 25 is formed on the side of the chamber 11 as an example, and is configured to be openable and closable. When the opening and closing door 25 is in an open state, the workpiece W can be transported into or out of the chamber 11 by a workpiece transport mechanism (not shown). The opening and closing of the electromagnetic valve 16 and the electromagnetic valve 20, the operation of the exhaust device 19 and the gas supply device 23, and the opening and closing of the opening and closing door 25 are uniformly controlled by a control mechanism (not shown) including a computer or the like. The control mechanism also uniformly controls various other operations in the plasma processing device 1.

[0087] The workpiece holding unit 13 is accommodated in the internal space L of the chamber 11 and holds the workpiece W. Examples of the workpiece holding unit 13 include a holding plate. The workpiece W carried into the chamber 11 through the opening and closing door 25 is stably held by the workpiece holding unit 13 .

[0088] The connecting plate 15 constitutes one surface of the outer wall portion (shell) of the chamber 11. In this embodiment, the connecting plate 15 is arranged on the upper surface of the chamber 11. Like the shell of the chamber 11, the connecting plate 15 is made of a conductive material such as metal. The plasma generating portion 7 is connected to the plasma processing portion 9 via the connecting plate 15. That is, Figure 4 As shown, the connecting plate 15 is formed with a through hole 27 corresponding to the shape of the top end of the plasma generating portion 7, and the top end of each plasma generating portion 7 is configured to be able to fit into the through hole 27. By fitting the top end of each plasma generating portion 7 into the through hole 27, as shown in FIG. Figure 1 As shown, the space on the front side of the connection plate 15 and the space on the back side of the connection plate 15 (the internal space L of the cavity 11) are partitioned, and the internal space L is in a sealed state.

[0089] Here, the structure of the plasma generating unit 7 will be described. Figure 2 7 is a longitudinal sectional view of the plasma generating section 7. Figure 2 As shown in FIG. 1 , the plasma generating unit 7 includes an outer conductor 29, a first dielectric 31, a second dielectric 33, and a microwave supply port 35. The outer conductor 29 is a cylindrical member made of a conductive material such as metal. The outer conductor 29 is a waveguide having a shape corresponding to the propagation mode of the microwave, and an opening 34 is formed at the top end side. The base end side ( Figure 2 The right side of the outer conductor 29 is closed by the partition wall 36. In the first embodiment, as the outer conductor 29, a cylindrical waveguide for propagating TM mode microwaves is described as an example.

[0090] The first dielectric 31 is disposed in the direction of the main axis of the outer conductor 29 (in Figure 2 The first dielectric 31 is a rod-shaped member extending in the x direction (in the x direction, etc.) and is disposed inside the outer conductor 29. The first dielectric 31 is composed of a dielectric material that propagates microwaves, and an example of the constituent material is alumina or quartz. The first dielectric 31 is connected to the microwave supply cable 5 at the base end side, and propagates the microwave supplied by the microwave supply cable 5 from the base end side to the top end side.

[0091] In addition, in the first embodiment, the first dielectric 31 is specified in diameter and shape so as to fill the inside of the outer conductor 29. In the present embodiment, the first dielectric 31 is a cylindrical member made of aluminum oxide, and is configured so that the outer diameter of the first dielectric is equal to the inner diameter of the outer conductor 29. A recess 37 is formed on the base end side of the first dielectric 31. In the first embodiment, the recess 37 extends in the x direction and is configured so that the microwave supply cable 5 can be inserted in the x direction.

[0092] The second dielectric 33 is disposed on the tip side of the outer conductor 29 in a manner to close the opening 34, and is connected to the first dielectric 31. The second dielectric 33 is made of a dielectric material that propagates microwaves, similarly to the first dielectric 31. An example of the material thereof is alumina or quartz. In the present embodiment, the second dielectric 33 is made of alumina.

[0093] like Figure 2 and Figure 4 As shown, the first dielectric 31 and the second dielectric 33 are connected via a connecting portion 39. The connecting portion 39 is composed of a first connecting portion 39A formed at the top end of the first dielectric 31 and a second connecting portion 39B formed at the base end of the second dielectric 33. The connecting portion 39 can be used as a structure for connecting the first dielectric 31 and the second dielectric 33 by screwing, fitting or snapping, etc. as appropriate.

[0094] In the first embodiment, the connection part 39 connects the first dielectric 31 and the second dielectric 33 by screwing. As a specific structural example, the first connection part 39A is a concave part formed with a female thread, and the second connection part 39B is a convex part formed with a male thread. Figure 5 As shown, the first connecting portion 39A and the second connecting portion 39B are screwed together, so that the first dielectric 31 and the second dielectric 33 are stably connected.

[0095] The surface on the top side of the second dielectric 33 is set as the outer surface 41. Figure 1 and Figure 4 As shown, the second dielectric 33 at the top of the plasma generating unit 7 is engaged with the through hole 27, and the outer surface 41 of the second dielectric 33 extends through the connecting plate 15 to the inner space L of the cavity 11. That is, the first dielectric 31 and the inner space L of the cavity 11 are connected via the second dielectric 33.

[0096] By connecting the first dielectric 31 and the second dielectric 33, the microwave energy propagating from the base end portion to the top end portion of the first dielectric 31 is further propagated to the base end portion of the second dielectric 33. In addition, the microwave energy is propagated to the top end portion of the second dielectric 33, that is, the outer surface 41, and plasma can be generated around the outer surface 41. It should be noted that in the present embodiment, the outer surface 41 (the surface on the top end side) of the second dielectric 33 is a tapered shape that becomes thinner from the base end side of the outer conductor 29 toward the top end side.

[0097] In the first embodiment, the first dielectric 31 and the second dielectric 33 are connected via the connection portion 39, thereby forming a dielectric member 43 as a whole. The dielectric member 43 composed of the first dielectric 31 and the second dielectric 33 functions as a dielectric member that propagates microwaves from the base end side to the tip end side. In addition, by forming a structure in which the first dielectric 31 and the second dielectric 33 are connected, the shape of the tip end portion of the dielectric member 43 can be appropriately changed by appropriately replacing and installing a plurality of second dielectrics 33 having different shapes of the outer surface 41 relative to the first dielectric 31.

[0098] As an example, the second dielectric 33 having the outer surface 41 tapering toward the tip side can be removed from the first dielectric 31 and Fig. 9 As shown in (a), the second dielectric 33A having a cylindrical shape is connected to the first dielectric 31 to form a dielectric member 43. The outer diameter of the second dielectric 33A is constant from the base end side to the tip end side, and the outer diameter of the outer surface 41A is substantially the same as the outer diameter of the outer conductor 29. The second dielectric 33A, unlike the second dielectric 33, does not need to be processed into a tapered shape. Therefore, when the plasma generating portion 7 is a structure including the second dielectric 33A, the manufacturing cost of the plasma generating portion 7 can be suppressed to a lower level.

[0099] In addition, as another example, Fig. 9 As shown in (b), the second dielectric 33B having a shape tapering from the tip side toward the base side can also be connected to the first dielectric 31 to form a dielectric member 43. The diameter of the outer surface 41B provided by the second dielectric 33B is configured to be longer than the diameter of the outer conductor 29. That is, the outer surface 41B has a plane with a larger area than the outer surface 41 and the outer surface 41A. Thus, by performing plasma treatment using the plasma generating portion 7 provided with the second dielectric 33B, plasma treatment can be performed on a wider range of the workpiece W. Therefore, the plasma treatment efficiency in the plasma treatment device 1 can be further improved.

[0100] like Fig. 9 (a) and Fig. 9 As shown in (b), the plasma generating unit 7 of the first embodiment can appropriately replace the second dielectrics 33, 33A, 33B etc. with different shapes of the mounting outer surface 41 according to the range of plasma generation and the purpose of plasma treatment. Therefore, the versatility of the plasma generating unit 7 can be further improved.

[0101] An annular stopper 40 is provided on the outer peripheral surface at the tip end of the outer conductor 29. Figure 1 and Figure 4As shown, by fitting the plasma generating unit 7 into the through hole 27 provided in the connecting plate 15, the stopper 40 provided on the outer peripheral portion of the outer conductor 29 abuts against the outer surface of the connecting plate 15. By abutting the stopper 40 against the connecting plate 15, the posture of the plasma generating unit 7 connected to the plasma processing unit 9 can be stably maintained.

[0102] The microwave supply port 35 is disposed at the base end of the outer conductor 29, and guides the microwave supply cable 5 to the first dielectric 31. In the first embodiment, since the microwave of the TM mode is propagated, the microwave supply port 35 is configured to extend in the axial direction at the base end side (bottom surface) of the outer conductor 29 as a waveguide. That is, the microwave supply port 35 is configured to penetrate the partition wall 36 of the outer conductor 29 in the x direction. The microwave cable 5 is guided to the recess 37 of the first dielectric 31 through the inside of the microwave supply port 35, and is inserted in the extension direction of the recess 37 (x direction in the first embodiment) and connected to the first dielectric 31.

[0103] In the first embodiment, the recess 37 at the connection portion between the microwave supply cable 5 and the first dielectric 31 functions as a gap portion for impedance matching. That is, the recess 37 moderates the change in the relative dielectric constant in the direction of input (supply) microwaves, thereby more appropriately matching impedance. Here, regarding the effect of the structure in which the recess 37 is formed in the first dielectric 31 and the microwave supply cable 5 is connected to the first dielectric 31 via the recess 37, the following is described using Figure 6 and Figure 7 To explain.

[0104] Figure 6 The figures show the structure of a comparative example in which the first dielectric 31 does not have the recess 37. Figure 7 The figures show the structure of the first embodiment in which the first dielectric 31 has a recess 37. Figure 6 The plasma generating portion of the comparative example shown is denoted by reference numeral 7F to be distinguished from the plasma generating portion 7 of the first embodiment.

[0105] Figure 6 (a) is a longitudinal sectional view showing a base end portion of a plasma generating portion 7F of a comparative example, Figure 6 (b) is a graph showing the change in relative dielectric constant in the input direction of microwaves. Figure 6 As shown in (a), in the structure of the comparative example without the recess 37, the microwave supply cable 5 is connected to the bottom surface of the first dielectric 31 as a cylindrical member by abutting against the microwave supply cable 5. In this case, the medium existing around the microwave supply cable 5 is generally air. In addition, the relative dielectric constant (relative dielectric constant ε) of air is 1.0. Therefore, in the direction of input microwaves, i.e., in the x direction, in the region R1 where the microwave supply cable 5 extends, as shown in FIG. Figure 6 As shown in (b), ε=1.0. It should be noted that, when the medium existing around the microwave supply cable 5 is a substance different from air, the relative dielectric constant in the region R1 changes according to the relative dielectric constant of the medium.

[0106] On the other hand, the relative dielectric constant of aluminum oxide constituting the first dielectric 31 is 9.8. Therefore, in the region R2 where the first dielectric 31 is arranged in the x direction, ε=9.8. As a result, Figure 6 As shown in (b), the relative dielectric constant changes sharply from 1.0 to 9.8 at the connection portion (boundary portion between region R1 and region R2) between the microwave supply cable 5 and the first dielectric 31. If the relative dielectric constant changes sharply in the direction of input microwaves like this, it is difficult to match the impedance of the input side and the output side in the plasma generating section 7F.

[0107] In contrast to the structure without the recessed portion 37 , the plasma generating portion 7 having the recessed portion 37 is divided into three regions in the x direction which is the direction in which microwaves are input. Figure 7 (a) is a longitudinal sectional view showing the base end portion of the plasma generating portion 7 of Example 1, Figure 7 (b) is a graph showing the change in relative dielectric constant in the input direction of microwaves. The plasma generating portion 7 having the recess 37 is divided into a region R1 where the microwave supply cable 5 extends, a region R2 where the recess 37 is not extended in the first dielectric 31, and a region R3 where the recess 37 extends in the first dielectric 31. The region R3 where the recess 37 is arranged is a region existing between the region R1 and the region R2.

[0108] exist Figure 7 In the region R1, the medium around the microwave supply cable 5 is air. Figure 7 In, also with Figure 6 Similarly, the relative dielectric constant in region R1 is 1.0. In region R2, the first dielectric 31 fills the interior of the outer conductor 29. Figure 6 same, Figure 7 The relative dielectric constant in the region R2 of the plasma generating portion 7 is also equivalent to the relative dielectric constant of the material (here, aluminum oxide) constituting the first dielectric 31. That is, the relative dielectric constant in the region R2 is 9.8.

[0109] Here, the relative dielectric constant in the region R3 where the recess 37 is formed is higher than the relative dielectric constant in the region R1, and lower than the relative dielectric constant in the region R2. That is, in the region R3, in the radial direction (y direction) of the outer conductor 29, the medium (air) filling the recess 37 and the material (aluminum oxide) constituting the first dielectric 31 are mixed. As a result, the relative dielectric constant ε3 in the region R3 becomes a value between the relative dielectric constant 1.0 of air and the relative dielectric constant 9.8 of aluminum oxide. By adjusting the ratio of the portion where the recess 37 is arranged to the portion where the first dielectric 31 is arranged in the region R3, the specific value of the relative dielectric constant ε3 can be set to an arbitrary value.

[0110] The results, such as Figure 7 As shown in (b), at the portion where the microwave supply cable 5 is inserted into the recess 37 (the boundary between the region R1 and the region R3), the relative dielectric constant changes from 1.0 to ε3. Furthermore, at the connection portion between the microwave supply cable 5 inserted into the recess 37 and the first dielectric 31 (the boundary between the region R3 and the region R2), the relative dielectric constant changes from ε3 to 9.8. The difference between 1.0 and ε3 and the difference between 9.8 and ε3 are both smaller than the difference between 9.8 and 1.0. That is, in the structure having the recess 37, the region R3 where the recess 37 is provided acts as a region for buffering the change in the relative dielectric constant, and the relative dielectric constant changes gently in the microwave input direction.

[0111] By using the structure including the recessed portion 37, the change of the relative dielectric constant in the direction of input microwaves can be mitigated. That is, by providing the region R3 corresponding to the buffer region, a sharp change of the relative dielectric constant can be prevented, so that the impedance matching between the input side and the output side is made easier in the plasma generating unit 7 of the first embodiment. In the first embodiment, the recessed portion 37 corresponds to the relative dielectric constant buffer portion in the present invention.

[0112] <Description of the action>

[0113] Here, the operation of the plasma processing device 1 is described. First, the workpiece W is transported from the opening and closing door 25 into the chamber 11 using a workpiece conveying mechanism (not shown), and the workpiece W is placed on the workpiece holding portion 13. The workpiece holding portion 13 stably holds the workpiece W by means of adsorption holding or the like. Then, the workpiece holding portion 13 is appropriately moved so that the area of ​​the workpiece W to be subjected to plasma processing approaches the outer surface 41 of the plasma generating portion 7.

[0114] When the workpiece W is arranged close to the outer surface 41, the internal space L of the cavity 11 is adjusted. That is, after the control mechanism closes the opening and closing door 25 to make the cavity 11 sealed, the solenoid valve 16 is opened to operate the exhaust device 19. When the exhaust device 19 is operated, the air retained in the internal space L of the cavity 11 is exhausted.

[0115] After exhausting the internal space L of the chamber 11, the control mechanism closes the electromagnetic valve 16 and opens the electromagnetic valve 20 to operate the gas supply device 23. When the gas supply device 23 is operated, the excitation gas G is supplied to the internal space L of the chamber 11.

[0116] When the gas G is supplied to the internal space L of the cavity 11, the microwave generating unit 5 is operated to oscillate microwaves. The oscillated microwaves are supplied to the plasma generating unit 7 by the microwave supply cable 5. The supplied microwaves are propagated to the first dielectric 31 at the connection mechanism 35. That is, the microwaves are propagated from the microwave supply cable 5 inserted into the recess 37 to the base end of the first dielectric 31.

[0117] At this time, the change in relative dielectric constant in the input direction of microwaves is mitigated by inserting the microwave supply cable 5 into the recess 37 formed in the first dielectric 31. Therefore, the impedance of microwaves is more appropriately adjusted, and thus the generation of unwanted reflected power can be more reliably prevented.

[0118] The microwave supplied to the base end of the first dielectric 31 propagates inside the first dielectric 31. That is, the microwave propagates in the x direction in which the first dielectric 31 extends, and propagates from the top end of the first dielectric 31 to the base end of the second dielectric 33. The microwave propagated to the base end of the second dielectric 33 propagates toward the outer surface 41 of the second dielectric 33. When the second dielectric 33 receives the supply of microwaves, the gas G is excited around the outer surface 41 in the internal space L of the cavity 11 to generate plasma. Under the action of the plasma generated by the plasma generating unit 7, the workpiece W disposed close to the outer surface 41 is subjected to a predetermined treatment. After the plasma treatment of the workpiece W is completed, the control mechanism opens the opening and closing door 25 to transport the workpiece W out of the cavity 11, and a series of processes related to the plasma treatment of the workpiece W are completed.

[0119] <Effects Achieved by the Structure of Example 1>

[0120] In the plasma processing device 1 of the first embodiment, the plasma generating part 7 has a waveguide structure as a whole, and the first dielectric 31 made of a dielectric material is arranged inside the outer conductor 29 as a waveguide. Then, microwaves are propagated from the base end to the tip end using the first dielectric 31 and the second dielectric 33 connected to the first dielectric 31. That is, the plasma generating part 7 of the first embodiment does not have a conductor inside the outer conductor 29, so the insulation distance can be made long.

[0121] Here, the effects achieved by the structure of Example 1 will be described while comparing with the conventional device. The conventional plasma generating device 100 uses a coaxial tube structure. That is, in the plasma generating device 100, Fig.17 As shown in FIG. 1 , a central core 101 as a conductor is disposed inside an outer shield 102 corresponding to an outer conductor. Therefore, the insulation distance P1 of the conventional plasma generating device 100 corresponds to the distance from the outer shield 102 to the central core 101, and thus the insulation distance P1 becomes a distance shorter than half of the inner diameter of the outer shield 102. As a result, the insulation distance P1 is shorter than the diameter of the outer shield 102, so insulation breakdown is likely to occur in the plasma generating device 100. In order to increase the insulation distance P1 in order to avoid insulation breakdown, the diameter of the outer shield 102 needs to be increased, and thus it is difficult to avoid the increase in size of the plasma generating device 100.

[0122] In addition, as another method of avoiding insulation breakdown in conventional devices, a method of reducing the output of the supplied microwaves is cited. However, if the output of the microwaves is reduced, the output of the plasma in the plasma generating device 100 is reduced, so there is a problem that the efficiency of the plasma processing using the plasma generating device 100 is reduced.

[0123] On the other hand, in the plasma processing apparatus 1 of the first embodiment, the microwave is propagated toward the top end using the first dielectric 31 and the second dielectric 33 made of dielectric material. Figure 2 As shown in the figures, since there is no need to arrange a conductor inside the outer conductor 29, the insulation distance P2 of the plasma generating part 7 is equivalent to the inner diameter of the outer conductor 29. That is, compared with the conventional device, in the plasma generating part 7 of the first embodiment, even if the inner diameter of the outer conductor 29 is the same, the insulation distance can be ensured to be more than twice the length. Therefore, it is possible to avoid insulation breakdown and realize compactness of the outer conductor 29.

[0124] In addition, since high-power microwaves can be supplied to plasma generating unit 7 while avoiding dielectric breakdown, the output of plasma in plasma generating unit 7 can be increased. Thus, the plasma processing efficiency in plasma processing apparatus 1 can be improved while preventing dielectric breakdown.

[0125] In particular, when microwaves are propagated only in the TE11 mode as the main propagation mode or the TM01 mode as the first high-order mode, it is necessary to arrange the first dielectric 31 composed of a dielectric material inside the outer conductor 29 and reduce the outer conductor 29 in the radial direction. Thus, by having the structure of Example 1, it is possible to prevent insulation breakdown and propagate microwaves only in the main propagation mode or the first high-order mode.

[0126] In addition, in the plasma generating unit 7 of the first embodiment, the first dielectric 31 for propagating microwaves from the base end side to the tip end side is filled inside the outer conductor 29. With such a structure, it is possible to prevent the accumulation of heat in the plasma generating unit 7. Figure 8 , while comparing with the conventional example, the effect of preventing heat accumulation in the structure of Example 1 is described.

[0127] In the conventional plasma generating device 100, Fig.17 As shown in FIG. 1 , a propagation medium 103 such as air is disposed between the side surface of the central core 101 and the outer shield 102. Therefore, the central core 101 is structured to be in contact with the outer shield 102 corresponding to the outer conductor only at the base end. Therefore, in the conventional plasma generating device 100, the contact area between the central core 101 and the outer shield 102 is very small.

[0128] In such a conventional plasma generating device 100, it is difficult to release the heat generated by the central core 101 to the outside. The propagation medium 103 that contacts most of the central core 101 is generally air, which has low thermal conductivity. Figure 8 As shown in (a), the heat H generated in the central core 101 that propagates the microwave is conducted to the outer shield 102 and discharged to the outside of the plasma generating device 100. However, in the conventional plasma generating device 100, since the contact area between the central core 101 and the outer shield 102 is small, the discharge efficiency of the heat H is very low. As a result, the heat generated in the central core 101 is accumulated inside the outer shield 102 and easily becomes high-heat. Therefore, even when the output of the microwave supplied to the plasma generating device 100 is low, problems caused by high heat generation are easily generated.

[0129] On the other hand, in the plasma generating unit 7 of the first embodiment, the first dielectric 31 fills the interior of the outer conductor 29. That is, the first dielectric 31 that propagates microwaves is in contact with the outer conductor 29 over the entire outer peripheral surface, so the contact area between the first dielectric 31 and the outer conductor 29 is very large. Figure 8 As shown in (b), the heat H generated in the first dielectric 31 is widely conducted to the outer conductor 29 and released to the outside of the plasma generating section 7. As a result, the heat removal efficiency of the plasma generating section 7 can be greatly improved, so that the heat can be more reliably prevented from accumulating inside the outer conductor 29. Therefore, high-output microwaves can be supplied to the plasma generating section 7 while avoiding high heating of the plasma generating section 7, so the output of the plasma in the plasma generating section 7 can be increased.

[0130] Furthermore, in the plasma generating unit 7 of the first embodiment, since the heat H of the first dielectric 31 is conducted to the entire outer conductor 29, the first dielectric 31 can be quickly cooled by arranging a cooling member outside the outer conductor 29. As an example, the first dielectric 31 can be quickly cooled by water cooling the outer conductor 29. Thus, the heat removal efficiency in the plasma generating unit 7 can be further improved, and the heat removal of the plasma generating unit 7 can be easily performed.

[0131] Moreover, in the plasma generating unit 7 of the first embodiment, the shape of the outer surface 41 can be appropriately changed, so the versatility of the plasma treatment can be improved. In the conventional plasma generating device 100 having a coaxial tube structure, from the viewpoint of impedance matching, the outer surface 109 of the dielectric 107 needs to be tapered from the base end side toward the tip side. That is, in the conventional plasma generating device 100, since the shape of the outer surface 109 is limited, the versatility of the plasma treatment is low. In addition, by making the dielectric 107 tapered, the area of ​​the top end of the outer surface 109 becomes smaller. As a result, the area that can be treated by performing one plasma treatment on the workpiece W becomes smaller, so the efficiency of the plasma treatment decreases.

[0132] On the other hand, the plasma generating unit 7 of the first embodiment has a waveguide structure as a whole, so even if the top end of the dielectric member 43 is a shape other than a cone, impedance matching can be achieved. Therefore, the top end of the dielectric member 43 (the top end of the second dielectric 33) can be formed into various shapes such as a cylindrical shape or a shape that becomes thicker toward the top end. That is, in the plasma generating unit 7 of the first embodiment, it is possible to achieve impedance matching and appropriately change the top end of the dielectric member 43 according to the range and purpose of plasma processing, so the versatility of the plasma generating unit 7 can be improved.

[0133] It should be noted that, in the conventional plasma generating device 100, the dielectric 107 is disposed only on the tip side of the outer shield 102. Therefore, in order to achieve more appropriate impedance matching, not only the outer surface 109 on the tip side of the dielectric 107 but also the outer surface 110 on the base side needs to be processed into a tapered shape. On the other hand, in the plasma generating unit 7 of the first embodiment, since the inside of the outer conductor 29 is filled with the first dielectric 31, the impedance can be appropriately matched without processing the first dielectric 31 into a tapered shape inside the outer conductor 29. That is, in the plasma generating unit 7, since it is not necessary to process both surfaces of the dielectric member 43 into a tapered shape, it is possible to reduce the manufacturing cost of the plasma generating unit 7 while ensuring the impedance matching efficiency.

[0134] [Example 2]

[0135] Next, the second embodiment of the present invention will be described. It should be noted that the same components as those of the plasma processing device 1 described in the first embodiment are denoted by the same reference numerals, and different components are described in detail. The plasma generating unit 7A of the second embodiment is different from the plasma generating unit 7 of the first embodiment in the structure of the portion connected to the microwave supply cable 5.

[0136] In the plasma generating unit 7A of the second embodiment, as Fig.10 As shown in the figure, the first dielectric 31 includes a connecting member 45 instead of the recess 37. The connecting member 45 is disposed at the portion where the first dielectric 31 is connected to the microwave supply cable 5. In the second embodiment, the connecting member 45 is disposed at the base end side of the first dielectric 31. In the second embodiment, a structure in which the diameter of the connecting member 45 is the same as the diameter of the first dielectric 31 is illustrated, but a structure in which the diameter of the connecting member 45 is smaller than the diameter of the first dielectric 31 may also be illustrated. As an example, the connecting member 45 may include a connecting member 45 having a diameter similar to that of the first dielectric 31. Figure 2 The diameter of the recess 37 shown is approximately the same diameter.

[0137] The connecting member 45 is made of a dielectric material having a relative dielectric constant lower than that of the first dielectric 31. As an example, when the first dielectric 31 is made of aluminum oxide (ε=9.8), quartz (ε=3.78) can be cited as a constituent material of the connecting member 45. In addition, the connecting member 45 is made of a dielectric material having a relative dielectric constant higher than that of a medium existing around the microwave supply cable 5. In Example 2, as in Example 1, the medium of the microwave supply cable 5 is air (ε=1.0), and therefore, as a constituent material of the first dielectric 31 in Example 2, quartz is an example of a preferred dielectric material.

[0138] In the second embodiment, the connection member 45 forms a region where the change of the relative dielectric constant is moderated at the connection portion between the microwave supply cable 5 and the first dielectric 31. That is, the connection member 45 makes the impedance matching more suitable by making the change of the relative dielectric constant in the direction of the input microwave moderated. Figure 6 and Fig.11 The effect of the structure in which the microwave supply cable 5 and the first dielectric 31 are connected via the connecting member 45 will be described.

[0139] like Figure 6 As shown in (a), in the structure in which the microwave supply cable 5 is connected to the first dielectric 31 without the connecting member 45, the relative dielectric constant changes sharply. That is, the medium existing around the microwave supply cable 5 is air. Figure 6 As shown in (b), in the x direction, which is the direction of input microwaves, in the region R1 where the microwave supply cable 5 extends, the relative dielectric constant ε is 1.0. On the other hand, since the first dielectric 31 is made of aluminum oxide, the relative dielectric constant ε is 9.8 in the region R2 where the first dielectric 31 is arranged. As a result, the relative dielectric constant changes sharply from 1.0 to 9.8 at the connection portion between the microwave supply cable 5 and the first dielectric 31 (the boundary portion between the region R1 and the region R2).

[0140] On the other hand, the plasma generating portion 7A having the connecting member 45 is divided into three regions in the x direction which is the direction in which microwaves are input. Fig.11 (a) is a longitudinal sectional view showing the base end portion of the plasma generating portion 7A of Example 2, Fig.11 (b) is a graph showing the change in relative dielectric constant in the microwave input direction. The plasma generating part 7 having the recess 37 is divided into a region R1 where the microwave supply cable 5 extends, a region R2 where the first dielectric 31 is arranged, and a region R3 where the connecting member 45 is arranged.

[0141] exist Fig.11 In the region R1, the medium around the microwave supply cable 5 is air. Fig.11 As shown in (b), the relative dielectric constant in region R1 is 1.0. In addition, in region R2, the first dielectric 31 fills the interior of the outer conductor 29. Therefore, the relative dielectric constant in region R2 is equivalent to the relative dielectric constant of the material constituting the first dielectric 31 (here, aluminum oxide), that is, 9.8. Furthermore, the relative dielectric constant in region R3 is equivalent to the relative dielectric constant of the material constituting the connecting member 45 (here, quartz), that is, 3.78.

[0142] The results, such as Fig.11As shown in (b), at the portion where the microwave supply cable 5 and the connecting member 45 are connected (the boundary portion between the region R1 and the region R3), the relative dielectric constant changes from 1.0 to 3.78. Also, at the connection portion between the connecting member 45 and the first dielectric 31 (the boundary portion between the region R3 and the region R2), the relative dielectric constant changes from 3.78 to 9.8. That is, in the structure having the connecting member 45 made of a material having a relative dielectric constant lower than that of the first dielectric 31 and higher than that of the medium existing around the microwave supply cable 5, the region R3 where the connecting member 45 is provided functions as a region for buffering the change in the relative dielectric constant, and the relative dielectric constant changes gently in the input direction of the microwave.

[0143] By using the structure of the second embodiment having the connection member 45, the change of the relative dielectric constant in the direction of input microwaves can be mitigated, similarly to the structure of the first embodiment having the recess 37. That is, by providing the region R3 corresponding to the buffer region, a sharp change of the relative dielectric constant can be prevented, so that it is easier to match the impedance of the input side and the output side in the plasma generating unit 7A of the second embodiment. In the second embodiment, the connection member 45 corresponds to the relative dielectric constant buffer portion in the present invention. The operation of the plasma processing device 1 having the plasma generating unit 7A of the second embodiment is the same as that of the first embodiment, and therefore the description of the operation is omitted.

[0144] [Example 3]

[0145] Next, the third embodiment of the present invention will be described. It should be noted that the same reference numerals are used for the same structures as the plasma processing apparatus 1 described in the first embodiment, and the different components will be described in detail. The configuration of the plasma generating unit 7B of the third embodiment is different from that of the plasma generating unit 7 of the first embodiment. Fig.12 It is a longitudinal sectional view of the plasma generating unit 7B of the third embodiment.

[0146] In the first embodiment, a cylindrical waveguide for propagating microwaves in the TM mode (specifically, the TM01 mode) is used as the outer conductor 29. On the other hand, in the plasma generating unit 7B of the third embodiment, a cylindrical waveguide for propagating microwaves in the TE mode (specifically, the TE11 mode) is used as the outer conductor 29B. Fig.12 As shown, the microwave supply port 35 for guiding the microwave supply cable 5 is disposed on the side surface of the outer conductor 29B. In the third embodiment, the microwave supply port 35 is disposed on the side surface of the outer conductor 29B at a portion close to the base end.

[0147] In the third embodiment, a recess 37B is formed on the side of the first dielectric 31. The recess 37B is arranged at a position connected to the microwave supply port 35, in the radial direction of the first dielectric 31 (in Fig.12 The microwave supply cable 5 is guided by the microwave supply port 35 and inserted into the recess 37B. Since the recess 37B extends in the y direction, the microwave supply cable 5 is inserted in the y direction and connected to the first dielectric 31. That is, the input direction of the microwave in Example 3 is the y direction.

[0148] In Example 3, the change in the relative dielectric constant in the input direction of the microwave is Fig.13 As shown. Fig.11 (a) is a longitudinal sectional view showing the base end portion of the plasma generating portion 7B of Example 3, Fig.11 (b) is a graph showing the change in relative dielectric constant in the input direction of microwaves. In the plasma generating section 7B having the recess 37B, it is divided into three regions in the y direction, which is the direction in which microwaves are input. That is, it is divided into a region R1 where the microwave supply cable 5 extends, a region R2 filled with the first dielectric 31, and a region R3 where the recess 37B is arranged.

[0149] As in the first embodiment, etc., in the third embodiment, the medium existing around the microwave supply cable 5 is air. Fig.13 As shown in (b) of FIG. 1 , the relative dielectric constant in region R1 is 1.0. In region R2, the first dielectric 31 fills the interior of the outer conductor 29. Therefore, the relative dielectric constant in region R2 is 9.8.

[0150] In the region R3, in the main axis direction (x direction) of the outer conductor 29, the medium (air) filling the recess 37 and the material (alumina) constituting the first dielectric 31 are mixed. As a result, the relative dielectric constant ε3 in the region R3 becomes a value between the relative dielectric constant of 1.0 of air and the relative dielectric constant of 9.8 of alumina. That is, the relative dielectric constant in the region R3 where the recess 37 is formed is higher than the relative dielectric constant in the region R1, and lower than the relative dielectric constant in the region R2.

[0151] The results, such as Fig.13 As shown in (b), at the portion where the microwave supply cable 5 is inserted into the recess 37B (the boundary portion between the region R1 and the region R3), the relative dielectric constant changes from 1.0 to ε3. Furthermore, at the connection portion between the microwave supply cable 5 inserted into the recess 37B and the first dielectric 31 (the boundary portion between the region R3 and the region R2), the relative dielectric constant changes from ε3 to 9.8. Thus, in the structure having the recess 37B, the region R3 provided with the recess 37 acts as a region for buffering the change in the relative dielectric constant, and in the microwave input direction (y direction), the relative dielectric constant changes gently, so that it is easier to match the impedance of the input side and the output side.

[0152] In the plasma processing device 1 having the plasma generating portion 7B of the third embodiment, the microwave oscillated by the microwave generating portion 3 is input to the plasma generating portion 7B in the y direction. At this time, by having the recess 37B, the change in the relative dielectric constant when the microwave is input to the dielectric member 43 (the first dielectric 31) is mitigated. The microwave input to the dielectric member 43 propagates from the base end side to the top end side along the x direction in which the dielectric member 43 (the first dielectric 31 and the second dielectric) extends. And, on the outer surface 41 disposed at the top end portion of the dielectric member 43 (the top end portion of the second dielectric 33), the gas G inside the cavity 11 is excited to generate plasma. In this way, in the plasma generating portion of the present invention, plasma can be generated using microwaves of more diverse propagation modes compared to conventional devices.

[0153] <Other Embodiments>

[0154] It should be noted that the embodiments disclosed this time are illustrative and non-restrictive in all aspects. The scope of the present invention includes the claims and all changes within the meaning and scope equivalent to the claims. As an example, the present invention can be implemented in the following modified forms.

[0155] (1) In the above-mentioned embodiments, the outer conductor 29 is a cylindrical waveguide structure, but the outer conductor 29 is not limited to a cylindrical shape. As an example, when the plasma generating unit 7 propagates microwaves in the TE10 mode, a rectangular waveguide can be used as the outer conductor 29. Unlike the conventional plasma generating device 100 that uses a coaxial tube as an outer conductor, the cross-sectional shape of the outer conductor 29 having a waveguide structure is not limited to a cylindrical shape. Therefore, in the plasma processing device 1 of each embodiment, plasma processing can be performed in response to microwaves in a wider variety of propagation modes.

[0156] (2) In the above-mentioned embodiments, the microwave supply cable 5 is not limited to the structure in which the microwave supply cable 5 abuts against the first dielectric 31 or the connecting member 45. Fig.14 As shown, the microwave supply cable 5 may be arranged with a gap KP of a predetermined distance relative to the first dielectric 31. The distance of the gap KP is specified to be a value that allows microwaves to propagate from the microwave supply cable 5 to the first dielectric 31 or the connecting member 45. By forming a predetermined gap KP between the microwave supply cable 5 and the first dielectric 31, impedance matching can be achieved more appropriately. It should be noted that in the present invention, the so-called "microwave supply cable 5 is connected to the first dielectric 31" includes not only Figure 2 The structure in which the microwave supply cable 5 abuts against the first dielectric 31 as shown in the example of FIG. Fig.14 As shown, the microwave supply cable 5 is structured to be close to the first dielectric 31 to such an extent that microwave energy can propagate.

[0157] (3) In the above-mentioned embodiments, the dielectric member 43 is exemplified as a structure in which the first dielectric member 31 and the second dielectric member 33 are combined. However, the present invention is not limited thereto, and the first dielectric member 31 and the second dielectric member 33 may be integrated. Fig.15 As shown, the following structure may be adopted: the dielectric member 43 is a single member and has the outer surface 41 at the top end.

[0158] (4) In the above-mentioned embodiments, as long as the outer conductor 29 has a waveguide structure and has no conductor inside, it is not limited to the structure in which the first dielectric 31 fills the inside of the outer conductor 29. Fig.16 As shown, the structure in which the outer diameter of the first dielectric 31 is smaller than the inner diameter of the outer conductor 29 and the inner medium 47 is disposed between the first dielectric 31 and the outer conductor 29 is also included in the structure of the present invention. An example of the inner medium 47 is air.

[0159] (5) In the above-mentioned embodiments, as long as the outer conductor 29 has a waveguide structure and has no conductor inside, Figure 6 The plasma generating portion 7F shown is also included in the structure of the present invention. That is, as long as the outer conductor 29 has a waveguide structure and has no conductor inside, it is not limited to the structure in which the recess 37 or the connecting member 45 is provided in the first dielectric 31 .

[0160] (6) In the above-mentioned embodiments, the first dielectric 31 and the second dielectric 33 are not limited to being made of the same material, but may be made of different materials. That is, the first dielectric 31 may be made of a first material L1 having dielectricity and a relative dielectric constant of ε4, and the second dielectric 33 may be made of a second material L2 having dielectricity and a relative dielectric constant of ε5.

[0161] Furthermore, when the first dielectric 31 and the second dielectric 33 are made of different materials, the connection portion 39 functions as a region that moderates the change in relative dielectric constant. That is, the connection portion 39 functions as a region that moderates the change in relative dielectric constant when microwaves are input from the first dielectric 31 to the second dielectric 33. In particular, when the connection portion 39 is a structure that connects a concave portion and a convex portion, the connection portion 39 functions more preferably as a region that moderates the change in relative dielectric constant.

[0162] The structure of the plasma generating portion 7C of this modification is the same as that of the plasma generating portion 7 of the first embodiment, except that the first dielectric 31 and the second dielectric 33 are made of different materials. That is, in the plasma generating portion 7C of the modification, the connecting portion 39 is composed of a first connecting portion 39A which is a concave portion formed with a female thread, and a second connecting portion 39B which is a convex portion formed with a male thread. It should be noted that, here, the case where the relative dielectric constant ε5 of the second material L2 is higher than the relative dielectric constant ε4 of the first material L1 is described as an example.

[0163] In this modification, the relative dielectric constant in the input direction of the microwave changes as shown in Fig.19 shown. Fig.19 (a) is a longitudinal sectional view showing a plasma generating portion 7C of a modified example. Fig.19 (b) is a graph showing the change of the relative dielectric constant in the input direction of the microwave. In the plasma generating part 7C having the recess 37 and the connecting part 39, it is divided into five regions in the x direction, which is the direction in which the microwave is input. That is, it is divided into a region R1 where the microwave supply cable 5 extends, a region R2 filled with the first dielectric 31, a region R3 where the recess 37 is arranged, a region R4 where the connecting part 39 is arranged, and a region R5 where the second dielectric 33 is arranged.

[0164] exist Fig.19 In (a), in region R1, the medium around the microwave supply cable 5 is air. Fig.19 In (b), it is also related to Figure 6 Similarly, the relative dielectric constant in region R1 is 1.0. In addition, in region R2, the first dielectric 31 fills the inside of the outer conductor 29. Therefore, the relative dielectric constant in region R2 is equivalent to the relative dielectric constant ε4 of the first material L1 constituting the first dielectric 31. In addition, in region R5, the second dielectric 33 is filled in the y direction. Therefore, the relative dielectric constant in region R5 is equivalent to the relative dielectric constant ε5 of the second material L2 constituting the second dielectric 33.

[0165] Here, the relative dielectric constant in the region R3 where the recess 37 is formed is higher than the relative dielectric constant in the region R1, and lower than the relative dielectric constant in the region R2. That is, in the region R3, in the radial direction (y direction) of the outer conductor 29, the medium (air) filling the recess 37 and the first material L1 constituting the first dielectric 31 are mixed. As a result, the relative dielectric constant ε3 in the region R3 becomes a value between the relative dielectric constant 1.0 of air and the relative dielectric constant ε4 of the first material L1.

[0166] Furthermore, the relative dielectric constant in the region R4 where the connection portion 39 is formed is higher than the relative dielectric constant in the region R2, and lower than the relative dielectric constant in the region R5. That is, in the region R4, in the radial direction (y direction) of the outer conductor 29, the second material L2 constituting the connection portion 39 (first connection portion 39B) and the first material L1 constituting the first dielectric 31 are mixed. As a result, the relative dielectric constant ε6 in the region R4 becomes a value between the relative dielectric constant ε4 of the first material L1 and the relative dielectric constant ε5 of the second material L2. By adjusting the ratio of the portion where the connection portion 39 is arranged to the portion where the first dielectric 31 is arranged in the region R4, the specific value of the relative dielectric constant ε6 can be specified to an arbitrary value.

[0167] The results, such as Fig.19 As shown in (b), at the portion where the microwave supply cable 5 is inserted into the recess 37 (the boundary between the region R1 and the region R3), the relative dielectric constant changes from 1.0 to ε3. Furthermore, at the connection portion between the microwave supply cable 5 inserted into the recess 37 and the first dielectric 31 (the boundary between the region R3 and the region R2), the relative dielectric constant changes from ε3 to ε4. The difference between 1.0 and ε3 and the difference between ε4 and ε3 are both smaller than the difference between ε4 and 1.0. That is, in the structure having the recess 37, the region R3 where the recess 37 is provided acts as a region for buffering the change in the relative dielectric constant, and the relative dielectric constant changes gently in the microwave input direction.

[0168] Moreover, in this modified example, the connection portion 39 functions as a second region that moderates the change in the relative dielectric constant. That is, at the boundary portion between the region R2 and the region R4, the relative dielectric constant changes from ε4 to ε6. And, at the boundary portion between the region R4 and the region R5, the relative dielectric constant changes from ε6 to ε5. The difference between ε4 and ε6 and the difference between ε6 and ε5 are both smaller than the difference between ε4 and ε5. That is, in the structure having the connection portion 39, the region R4 provided with the connection portion 39 functions as a region that buffers the change in the relative dielectric constant, and the relative dielectric constant changes more moderately in the microwave input direction.

[0169] As described above, in the plasma generating unit 7C of this modification, the change in relative dielectric constant can be mitigated by the recess 37, and the change in relative dielectric constant can also be mitigated by the connecting portion 39. That is, by providing the region R4 corresponding to the second buffer region, a sharp change in relative dielectric constant can be prevented, so that the impedance matching between the input side and the output side is made easier in the plasma generating unit 7 of the first embodiment. In this modification, the connecting portion 39 corresponds to the second relative dielectric constant buffer portion in the present invention.

[0170] It should be noted that, in the modified example, the plasma generating portion 7C is not limited to the structure with the recessed portion 37, and the recessed portion 37 may be omitted. In addition, in the modified example, the plasma generating portion 7C may be configured such that the relative dielectric constant ε5 of the second material L2 is lower than the relative dielectric constant ε4 of the first material L1. Regardless of the magnitude relationship between the relative dielectric constant ε4 and the relative dielectric constant ε5, by providing the connecting portion 39 corresponding to the second relative dielectric constant buffer portion, it is possible to avoid a sharp change in the relative dielectric constant at the boundary between the first dielectric 31 and the second dielectric 33.

[0171] Description of Reference Numerals

[0172] 1. Plasma processing device; 3. Microwave generating unit; 5. Microwave supply cable; 7. Plasma generating unit (plasma generating device); 9. Plasma processing unit; 11. Cavity; 13. Workpiece holding unit; 15. Connecting plate; 29. ​​External conductor; 31. First dielectric; 33. Second dielectric; 34. Opening; 35. Microwave supply port; 36. Partition wall; 37. Recess; 39. Connecting unit; 41. External surface; 43. Dielectric member; 45. Connecting member.

Claims

1. A plasma generating device, characterized in that: The plasma generating device comprises: A conductive waveguide having an opening at one end; A first dielectric member extending inside the waveguide along the main axis of the waveguide, connected to a microwave supply cable for supplying microwaves, and propagating the supplied microwaves toward the one end side; and The second dielectric member is disposed so as to close the opening and generates plasma using the microwave propagated by the first dielectric member.

2. The plasma generating device according to claim 1, characterized in that: The first dielectric member extends along the main axis of the waveguide so as to fill the interior of the waveguide.

3. The plasma generating device according to claim 1, characterized in that: The first dielectric member includes a relative dielectric constant buffer portion for buffering a change in relative dielectric constant at a connection portion with the microwave supply cable.

4. The plasma generating device according to claim 3, characterized in that: The relative dielectric constant buffer portion is a recessed portion formed in the first dielectric member. The microwave supply cable is inserted in the direction in which the recess extends.

5. The plasma generating device according to claim 3, characterized in that: The relative dielectric constant buffer portion is a connecting member made of a material having a lower relative dielectric constant than that of the first dielectric member. The first dielectric member is connected to the microwave supply cable via the connecting member.

6. The plasma generating device according to any one of claims 1 to 5, characterized in that: The first dielectric member includes a second relative dielectric constant buffer portion for buffering a change in relative dielectric constant at a connection portion with the second dielectric member.

7. A plasma processing device, characterized in that: The plasma processing device comprises: a microwave supplying unit that supplies microwaves; a plasma generating unit that generates plasma using the microwaves supplied from the microwave supplying unit; and a plasma processing unit for processing a workpiece using the plasma generated by the plasma generating unit, The plasma generating unit is the plasma generating device according to any one of claims 1 to 5.

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