Plasma processing equipment

Abstract

The objective is to provide a plasma processing apparatus that allows the direction of application to each electrode and the direction of gas flow to be the same. [Solution] The invention is characterized by comprising a plasma generation unit 110 that generates plasma and includes at least a dielectric layer 111 and a plurality of electrode layers 112, 113 provided on the front and back surfaces of the dielectric layer 111; a power supply unit that applies an AC voltage to a pair of electrode layers 112, 113; and a gas flow unit 120 that includes one or more cylindrical bodies that penetrate the dielectric layer 111 and the pair of electrode layers 112, 113, and flows gas through the inside of the cylindrical bodies in order to process the gas with plasma.

Description

Technical Field

[0001] The present invention relates to a plasma processing apparatus. Background Art

[0002] In recent years, a technique called Dielectric Barrier Discharge has been developed for plasma processing technology, which makes it possible to generate low-temperature plasma under atmospheric pressure. As a result, the application scope of plasma processing has expanded, and its use is progressing in various applications. Purposes of plasma processing include sterilization, deodorization, surface modification, and decomposition of chemical substances. Further, the substance to be subjected to plasma processing may be any of solid, liquid, or gas.

[0003] Various plasma processing apparatuses have been developed for continuous plasma processing while flowing air. For example, Patent Document 1 discloses a plasma generator in which two or more layers of plasma generation units are arranged in a stacked manner, each plasma generation unit being provided with a flat first electrode and a flat second electrode facing each other with a gap therebetween. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2022-190472 Summary of the Invention Problem to be Solved by the Invention

[0005] Conventional plasma processing apparatuses have a configuration in which the direction in which an alternating voltage is applied is orthogonal to the flow direction of gas. Therefore, there is no other method but to flow gas in parallel to the in-plane direction of each electrode, which causes a problem of low design flexibility. Further, conventional plasma processing apparatuses impose great restrictions when combined with other apparatuses, so variations different from conventional ones have been desired.

[0006] In light of this background, the object of the present invention is to provide a plasma processing apparatus that can make the application direction of each electrode and the gas flow direction the same. [Means for solving the problem]

[0007] To solve the aforementioned problems, the present invention is characterized by comprising: a plasma generation unit that generates plasma and includes at least a dielectric layer and a plurality of electrode layers provided on the front and back surfaces of the dielectric layer; a power supply unit that applies an AC voltage to a pair of the electrode layers; and a gas flow unit that includes one or more cylindrical bodies that penetrate the dielectric layer and the pair of electrode layers, and flows gas through the inside of the cylindrical bodies in order to process the gas with plasma.

[0008] Furthermore, the present invention is characterized by comprising: a plasma generation unit that generates plasma and includes at least a dielectric layer and a plurality of electrode layers provided on the front and back surfaces of the dielectric layer; a power supply unit that applies an AC voltage to a pair of the electrode layers; and a gas flow unit that has communication holes communicating in the height direction of the dielectric layer and the electrode layers, and flows gas through the communication holes in order to process the gas with plasma.

[0009] According to the present invention, the degree of design flexibility can be increased by setting the device so that the direction in which the AC voltage is applied and the direction in which the gas flows are in the same direction.

[0010] Furthermore, it is preferable that the electrode layer is composed of three or more layers.

[0011] According to the present invention, increasing the number of electrode layers can further promote the reaction between the plasma and the gas, thereby improving the plasma generation efficiency.

[0012] Furthermore, it is preferable that the outer edge of the dielectric layer protrudes outward from the outer edge of the electrode layer to prevent abnormal discharge from occurring. Preferably, an inner edge of the dielectric layer projects inward beyond an inner edge of the electrode layer to prevent abnormal discharge, and an outer edge of the dielectric layer projects outward beyond an outer edge of the electrode layer to prevent abnormal discharge.

[0013] According to the present invention, occurrence of abnormal discharge can be prevented. [Effects of the Invention]

[0014] According to the plasma processing apparatus of the present invention, the application direction of voltage to each electrode and the flow direction of gas can be set to the same direction. [Brief Description of the Drawings]

[0015] [Figure 1] It is a perspective view for explaining a plasma generation unit. [Figure 2] It is a perspective view for explaining a plasma generation unit. [Figure 3] It is a cross-sectional view for explaining a plasma generation unit. [Figure 4] It is a perspective view for explaining a plasma generation unit according to a first modified example. [Figure 5] It is a perspective view for explaining a plasma generation unit according to a second modified example. [Figure 6] It is a perspective view showing the plasma processing apparatus according to a first embodiment of the present invention. [Figure 7] It is a cross-sectional view of Fig. 6. [Figure 8] It is a perspective view showing the plasma processing apparatus according to a second embodiment of the present invention. [Figure 9] It is a plan view showing the plasma processing apparatus according to the second embodiment. [Figure 10] It is a cross-sectional view of Fig. 8. [Figure 11] It is a perspective view showing the plasma processing apparatus according to a third embodiment of the present invention. [Figure 12] It is a plan view of Fig. 11. [Figure 13] It is a perspective view showing the plasma processing apparatus according to a fourth embodiment of the present invention. [Figure 14] It is a cross-sectional view of Fig. 13. MODES FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments of the present invention are not limited to the embodiments described below. Each embodiment and modified example can be applied in appropriate combination. In addition, directions such as "up and down" in the description are used for convenience of explanation, and do not limit the direction of the present invention.

[0017] To continuously perform plasma treatment on gas, the plasma treatment apparatus of the present embodiment includes a plasma generation unit having a multilayer structure including a dielectric layer, an electrode layer and an optional mask layer, a power supply unit capable of applying an alternating voltage between a pair of electrode layers, and a gas flow unit capable of flowing gas through the plasma generation unit. In dielectric barrier discharge, a dielectric layer is provided between two electrode layers, and by applying an alternating voltage between the two electrode layers, plasma can be generated in the dielectric layer sandwiched between the two electrode layers. First, the plasma generation unit will be described.

[0018] <Basic Structure of Plasma Generation Unit> As shown in Figs. 1 and 2, the plasma generation unit 10 includes a dielectric layer 11, an upper electrode 12, a lower electrode 13, an upper mask layer 14, and a lower mask layer 15. The plasma generation unit 10 is a thin-film member and has flexibility.

[0019] As shown in Figures 1-3, the dielectric layer 11 is a layered member placed between the upper electrode 12 and the lower electrode 13. The material of the dielectric layer 11 is an insulating material with a high dielectric breakdown voltage to prevent easy discharge between the upper electrode 12 and the lower electrode 13. Furthermore, since the material of the dielectric layer 11 will be exposed to the generated plasma, it is preferable that it is a material that has durability against active substances generated in the plasma. The material of the dielectric layer 11 is preferably a material mainly selected from glass, ceramics, and synthetic resins. "Mainly" means that the component composition is 50% by mass or more (the same applies hereinafter).

[0020] Examples of glass include soda-lime glass (soda glass), borosilicate glass, quartz glass, lead glass, and oxide glass. Synthetic resins include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include general-purpose resins such as polyolefins, polystyrene, polyvinyl acetate, polyurethane, polylactic acid, ABS resin, AS resin, acrylic resin, polyvinyl chloride, and polyvinylidene chloride; engineering plastics such as polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyester, and cyclic polyolefin; polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, liquid crystal polymer, polyetheretherketone, polyimide, polyamideimide, polyetherimide, fluororesins, unsaturated polyester resins, and polyurethane resins. Among these synthetic resins, silicone-based resins, which have excellent durability, are particularly preferred. The thickness of the dielectric layer 11 is not particularly limited, but to achieve lightness and miniaturization, it is preferably 0.1 mm to 5.0 mm, more preferably 0.1 mm to 3.0 mm, and even more preferably 0.1 to 1.0 mm.

[0021] As shown in Figures 2 and 3, the upper electrode (electrode layer) 12 and the lower electrode (electrode layer) 13 are layered members installed on the front and back surfaces of the dielectric layer 11. The upper electrode 12 and the lower electrode 13 are each provided with through holes 16 that penetrate in the thickness direction. In this embodiment, the through holes 16 are elongated and five are formed, but their shape and number are not limited. The through holes 16 may also be omitted.

[0022] The upper electrode (electrode layer) 12 and the lower electrode (electrode layer) 13 are formed of a conductive material, and can be made of a metal plate (including metal foil), conductive paint, conductive polymer, conductive film, etc. The thickness of the upper electrode 12 and the lower electrode 13 is not particularly limited, but in order to provide a flexible, lightweight, and compact processing apparatus, they are preferably 5 μm to 1.0 mm, more preferably 5 μm to 0.2 mm, and even more preferably 5 μm to 0.1 mm, respectively.

[0023] The dielectric layer 11, the upper electrode 12, and the lower electrode 13 may be laminated without using an adhesive, or they may be bonded together with an adhesive. The adhesive is preferably made of a material that is resistant to active substances generated in the plasma. Adhesives include epoxy, acrylic, urethane, phenol, urea, silicone, cyanoacrylate, rubber, and vinyl acetate types. Among these, silicone adhesives and UV-curing epoxy adhesives are preferred in terms of durability, with silicone adhesives being more preferred. The thickness of the adhesive is preferably 0.01 to 0.2 mm, and more preferably 0.01 to 0.1 mm.

[0024] As shown in Figure 3, the upper mask layer 14 and the lower mask layer 15 are components installed on the outside of the upper electrode 12 and the lower electrode 13, respectively. More specifically, the upper mask layer 14 is installed on the upper surface of the upper electrode 12. The lower mask layer 15 is installed on the lower surface of the lower electrode 13. The upper mask layer 14 and the lower mask layer 15 are each provided with through holes 17. In this embodiment, the through holes 17 are elongated and there are five of them, but the shape and number are not limited. The through holes 17 may be omitted.

[0025] As shown in Figures 2 and 3, the through-hole 17 has the same shape as the through-hole 16 and is in communication with it. The dielectric layer 11 is exposed to the outside through the through-holes 16 and 17. In other words, the surface of the dielectric layer 11 is exposed to the outside at multiple locations where the through-holes 16 and 17 are formed. The holes (cross-sectional portions) 16a and 17a of the through-holes 16 and 17 are also exposed to the outside, respectively.

[0026] The upper mask layer 14 and the lower mask layer 15 are made of an insulating material. Furthermore, it is preferable that the hardness of the upper mask layer 14 and the lower mask layer 15 be equal to or less than the hardness of the upper electrode 12 and the lower electrode 13. Although the plasma generation unit 10 is a thin component and therefore difficult to handle, the provision of the upper mask layer 14 and the lower mask layer 15 improves handling. The thicknesses of the upper mask layer 14 and the lower mask layer 15 are not particularly limited, but in order to provide a flexible, lightweight, and compact processing apparatus, they are preferably 5 μm to 1.0 mm, more preferably 5 μm to 0.2 mm, and even more preferably 5 μm to 0.1 mm, respectively. The thicknesses of the upper mask layer 14 and the lower mask layer 15 can be set as appropriate, but in this embodiment, they are formed to be greater than the thicknesses of the upper electrode 12 and the lower electrode 13.

[0027] The plasma generation unit 10 is very thin and flexible, which presents problems such as difficulty in handling during assembly. Furthermore, the upper electrode 12 and lower electrode 13 are made of conductive materials such as conductive metals or conductive dielectrics, and may be corroded by liquids or gases. For example, the upper electrode 12 and lower electrode 13 will oxidize with highly oxidizing gases and be corroded by sulfuric acid or hydrochloric acid. Additionally, while the plasma generation unit 10 is installed to conform to the shape of the object it is attached to, if only the upper electrode 12 and lower electrode 13 are present without the upper mask layer 14 and lower mask layer 15, problems arise, such as wrinkles forming in the metal electrodes or gaps forming between them and the dielectric layer 11, especially if the electrodes are made of thin metal. Gaps between the upper electrode 12 and lower electrode 13 and the dielectric layer 11 can also cause abnormal discharge. In this respect, according to this embodiment, the upper mask layer 14 and the lower mask layer 15 can protect the upper electrode 12 and the lower electrode 13, and the plasma generation unit 10 becomes easier to handle, improving workability and assembly. Furthermore, by providing the upper mask layer 14 and the lower mask layer 15, it can be installed on the object to be mounted without forming wrinkles or gaps. In addition, when multiple pairs of electrodes are provided to create a multi-stage system, the upper mask layer 14 and the lower mask layer 15 also become part of the dielectric that constitutes the barrier discharge, so even if gaps are created during installation, abnormal discharge is less likely to occur. Depending on the situation, the same effect can be obtained by using either the upper or lower mask layer.

[0028] Furthermore, the outer edges of the upper electrode 12 and the lower electrode 13 may be sealed with an insulator (not shown) to prevent their outer edges from being exposed to the outside environment and deteriorating over time, and to prevent discharge from occurring through the outer edges other than the through-hole 16. Similarly, the upper mask layer 14 and the lower mask layer 15 may have their outer edges sealed with an insulator (not shown) to prevent them from being exposed to the outside environment and reacting with external substances to deteriorate over time, and to prevent discharge from occurring through the outer edges other than the through-holes 17.

[0029] When the longitudinal direction of the through-holes 16 and 17 is parallel to the direction of gas flow, the resistance to gas flow is reduced, and the gas flow becomes smoother. On the other hand, when the longitudinal direction of the through-holes 16 and 17 is perpendicular to the direction of gas flow, the resistance to gas flow increases, the gas flow is disturbed, and the gas is agitated.

[0030] The shape, number, and orientation of the through-holes 16 and 17 relative to the gas flow can be appropriately selected and implemented according to the purpose of the plasma treatment, the effects of the plasma treatment, etc. Furthermore, the shape of the through-holes may differ between the front and back sides of the plasma generation unit 10. Alternatively, through-holes may be provided on the front side of the plasma generation unit 10, but not on the back side.

[0031] <First modified example of the plasma generation section> Figure 4 is a perspective view illustrating the plasma generation unit according to the first modified example. The plasma generation unit 10A according to the first modified example differs from the basic structure described above in that it does not have an upper mask layer 14. As in the plasma generation unit according to the first modified example, the mask layer may be provided only on one side of the plasma generation unit 10A.

[0032] <Second modified example of the plasma generation section> Figure 5 is a perspective view illustrating the plasma generation unit according to the second modified example. The plasma generation unit 10B according to the second modified example differs from the basic structure described above in that it does not have an upper mask layer 14 and a lower mask layer 15. The upper mask layer 14 and the lower mask layer 15 may be omitted, as in the plasma generation unit according to the second modified example. In other words, by configuring the plasma generation unit 10B with a dielectric layer 11, an upper electrode 12, and a lower electrode 13, it is possible to further miniaturize the unit and reduce the number of parts.

[0033] Furthermore, as in the first and second modified examples, by omitting both or one of the upper mask layer 14 and the lower mask layer 15, the upper electrode 12 and the lower electrode 13 can be brought into direct contact with the gas, allowing the plasma to come into contact with the gas at the ends of the electrodes and the plasma gas to be easily extracted.

[0034] <First Embodiment> Next, a plasma processing apparatus according to the first embodiment of the present invention will be described. The plasma processing apparatus 100 according to this embodiment comprises a plasma generation unit 110, a gas flow unit 120, and a power supply unit (not shown). The plasma generation unit 110 in this embodiment is in a form without both an upper mask layer and a lower mask layer, as in the second modified example described above.

[0035] The plasma generation unit 110 comprises a dielectric layer 111, an upper electrode (electrode layer) 112, and a lower electrode (electrode layer) 113. As shown in Figures 6 and 7, the dielectric layer 111 is layered and donut-shaped, with a communication hole 111a formed in the center that penetrates in the thickness direction of the layer. Furthermore, the outer diameter of the dielectric layer 111 is set to be larger than the outer diameters of the upper electrode 112 and the lower electrode 113 to prevent abnormal discharge. In other words, the dielectric layer 111 protrudes outward from the upper electrode 112 and the lower electrode 113.

[0036] The upper electrode 112 is placed on top of the dielectric layer 111. The upper electrode 112 has a smaller outer diameter than the dielectric layer 111. A communication hole 112a is formed in the center of the upper electrode 112, penetrating in the thickness direction of the layer.

[0037] The lower electrode 113 is placed on top of the dielectric layer 111. The lower electrode 113 has an outer diameter smaller than the dielectric layer 111 and larger than the upper electrode 112. A communication hole 113a is formed in the center of the lower electrode 113, penetrating in the thickness direction of the layer.

[0038] The gas flow section (cylindrical body) 120 is made of an insulator and has a cylindrical shape, and is arranged to penetrate the dielectric layer 111, the upper electrode 112, and the lower electrode 113 in the thickness direction. The outer surface of the gas flow section 120 is in contact with the communication hole 111a, but is spaced apart from the communication holes 112a and 113a.

[0039] The outer diameter and thickness of the dielectric layer 111, the upper electrode 112, and the lower electrode 113 can be appropriately modified within a range that does not cause abnormal discharge. For example, the outer diameters of the upper electrode 112 and the lower electrode 113 may be set to be the same.

[0040] The gas flow section 120 is a component that can flow gas inside the plasma generation section 110 in order to continuously process the gas with plasma. The gas flow section 120 allows gas to flow in from one end, along the axial direction, and discharges the gas from the other end. There are no particular restrictions on the gas flow section 120 as long as it is a component that can supply gas to the plasma generation section 110, allow the gas to pass through the space inside the plasma generation section 110, and then discharge the plasma-treated gas.

[0041] As a method for flowing the gas, any known method can be appropriately selected and used. As a drive device for flowing the gas, known devices such as centrifugal fans (sirocco fans, radial fans, turbo fans, etc.), axial flow fans (propeller fans, etc.), mixed flow fans (line fans, etc.), cross flow fans, and blowers can be used as appropriate.

[0042] Because the plasma processing apparatus 100 experiences temperature changes during use, there is a concern that problems such as delamination may occur over time if there are large differences in the coefficients of thermal expansion between the materials constituting the multilayer structure. Therefore, it is preferable that the materials and adhesives constituting the dielectric layer 111, which is laminated with the upper electrode 112 and the lower electrode 113, are made of highly flexible materials that can follow the dimensional changes of the upper electrode 112 and the lower electrode 113. As such materials, synthetic resin-based materials are preferred, and it is even more preferable to select and use an appropriate material from among synthetic resin-based materials.

[0043] To manufacture the plasma generation unit 110 of the plasma processing apparatus 100 in this embodiment, materials such as a dielectric layer 111, an upper electrode 112, and a lower electrode 113 are laminated. There are known methods for laminating each layer, such as pressure bonding, heat bonding, and adhesive application, and these can be selected and used as appropriate.

[0044] The power supply unit (not shown) applies an AC voltage between the upper electrode 112 and the lower electrode 113, which face each other with a dielectric layer 111 in between. The power supply unit is not particularly limited as long as it can apply an AC voltage of a predetermined voltage at a predetermined frequency to each electrode of the plasma generation unit 110; known power supply devices can be used. The frequency of the AC voltage is preferably 50Hz to 30MHz, more preferably 50Hz to 100kHz. Furthermore, the AC voltage is preferably 0.1 to 50kV, more preferably 0.2 to 10kV.

[0045] <Effects and Effects> Next, the effects of the plasma processing apparatus 100 according to this embodiment will be described. When an AC voltage is applied between the upper electrode 112 and the lower electrode 113 that sandwich the dielectric layer 111, plasma is generated within the dielectric layer 111 sandwiched between them. Furthermore, plasma is also generated near the walls (cross-sections) of each of the communication holes 112a and 113a. When an AC voltage is applied between two electrode layers, plasma is generally more likely to be generated from the protruding edges of the electrode layers than from the flat surfaces of the electrode layers. Therefore, in the plasma generation unit 110, more plasma is more likely to be generated near the walls (cross-sections) of the communication holes 112a and 113a than inside the dielectric layer 111 between the two electrode layers.

[0046] While applying an AC voltage between each electrode layer flanking the dielectric layer 111, the gas to be processed by the plasma is flowed through the gas flow section 120 located inside the plasma generation section 110. The gas is processed by the plasma generated near the surface of the dielectric layer 111 exposed to the outside within the communication holes 112a and 113a, and near the hole walls (cross-sections) within the communication holes 112a and 113a. In particular, the gas is processed more strongly by the plasma generated near the hole walls (cross-sections) of the communication holes 112a and 113a.

[0047] The functions exhibited by plasma treatment of a gas using the plasma treatment apparatus 100 of this embodiment include sterilization, virus inactivation, deodorization, surface modification, and decomposition of chemical substances. The mechanism by which these functions are exhibited is thought to be that plasma treatment generates reactive oxygen species such as singlet oxygen, hydrogen peroxide, OH radicals, peroxide radicals, and ozone in the gas, and these then kill target microorganisms or decompose and modify chemical substances through oxidation reactions. Examples of microorganisms include various bacteria, viruses, and fungi.

[0048] In the plasma processing apparatus 100 of this embodiment, the plasma-treated gas is sterilized and deodorized by the reactive oxygen species generated by the plasma, which kill microorganisms present in the gas and decompose chemical substances. Furthermore, in the plasma processing apparatus 100 of this embodiment, reactive oxygen species are present (residual) in the plasma-treated gas. Therefore, by blowing the plasma-treated gas generated by the plasma processing apparatus of this embodiment onto an object, microorganisms present in the object are killed or chemical substances are decomposed, thereby sterilizing and deodorizing the object.

[0049] The plasma processing apparatus 100 of this embodiment can be used in many industrial fields such as medicine (fiberscopes, endoscopes, various small cameras, etc.), housing, civil engineering, construction, agriculture, fisheries, livestock farming, food processing, transportation, storage, and retail for purposes such as deodorization, odor removal, sterilization and disinfection, and air purification.

[0050] According to the plasma processing apparatus 100 of this embodiment described above, the gas flow section 120 is positioned in the center of the plasma generation section 110 in the same direction (generally parallel) as the direction in which the alternating current is applied, and the gas can be circulated in the same direction (generally parallel) as the thickness direction of the upper electrode 112 and the lower electrode 113. This increases the degree of design flexibility.

[0051] Furthermore, when polyimide is used as the dielectric layer 111, the manufacturing process for commonly used flexible substrates can be utilized, thereby significantly reducing manufacturing costs.

[0052] Furthermore, the pair of electrode layers (upper electrode 112 and lower electrode 113) are each provided with communication holes 112a and 113a through which the dielectric layer 111 is exposed. This allows the plasma generated near the hole walls (cross-sections) of the electrode layers within the communication holes 112a and 113a to efficiently plasma-treat the gas flowing through the plasma generation unit 110.

[0053] Furthermore, the upper electrode 112 and the lower electrode 113 may have one or more through holes, for example, as shown in Figure 3. Also, a mask layer may be provided on the outside of the upper electrode 112 and the lower electrode 113. While the upper electrode 112 and the lower electrode 113 are shown as donut-shaped, equivalent effects can be obtained by using triangular or square shapes. Additionally, if the dielectric material constituting the gas flow section 120 is made too thin, discharge may begin between the upper electrode 112 and the lower electrode 113, for example. Therefore, the structure of the gas flow section 120 must be set to prevent abnormal discharge. In other words, to prevent abnormal discharge, a certain thickness of the dielectric material constituting the gas flow section 120 must be ensured, and this thickness is set according to the dielectric constant of the gas flow section 120 and the applied voltage.

[0054] <Second Embodiment> Next, a plasma processing apparatus according to the second embodiment of the present invention will be described. As shown in Figure 8, the plasma processing apparatus 200 according to this embodiment comprises a plasma generation unit 210, a gas flow unit 220, and a power supply unit (not shown). The plasma generation unit 210 of this embodiment is in a form without both an upper mask layer and a lower mask layer, as in the second modified example described above. The second embodiment will be described focusing on the differences from the first embodiment.

[0055] The plasma generation unit 210 comprises dielectric layers 211 and 214, an upper electrode (electrode layer) 212, a middle electrode (electrode layer) 213, and a lower electrode (electrode layer) 215. As shown in Figures 9 and 10, the dielectric layer 211 is layered and donut-shaped, with a communication hole 211a formed in the center. The dielectric layer 214 is layered and donut-shaped, with a communication hole 214a formed in the center. The outer diameters of the dielectric layers 211 and 214 are the same. The outer diameters of the dielectric layers 211 and 214 are set to be larger than the outer diameters of the upper electrode 212, the middle electrode 213, and the lower electrode 115 in order to prevent abnormal discharge. In other words, the outer edges of the dielectric layers 211 and 214 protrude outward from the outer edges of the upper electrode 212, the middle electrode 213, and the lower electrode 115.

[0056] The upper electrode 212 is placed on top of the dielectric layer 211. The upper electrode 212 has a smaller outer diameter than the dielectric layer 211. A communication hole 212a is formed in the center of the upper electrode 212.

[0057] The intermediate electrode 213 is placed in overlapping position between the dielectric layer 211 and the dielectric layer 214. The outer diameter of the intermediate electrode 213 is smaller than the outer diameters of the dielectric layers 211 and 214, but larger than the outer diameters of the upper electrode 212 and the lower electrode 215. A communication hole 213a is formed in the center of the intermediate electrode 213.

[0058] The lower electrode 215 is placed on top of the dielectric layer 214. The lower electrode 215 has a smaller outer diameter than the dielectric layer 214. A communication hole 215a is formed in the center of the lower electrode 215.

[0059] The gas flow section (cylindrical body) 220 is made of an insulator and has a cylindrical shape, and is arranged to penetrate the dielectric layers 211, 214, the upper electrode 212, the middle electrode 213, and the lower electrode 215 in the thickness direction. The outer surface of the gas flow section 220 is in contact with the communication holes 211a and 214a, respectively, but is spaced apart from the communication holes 212a, 213a, and 215a.

[0060] The upper electrode 212 and lower electrode 215 have different polarities from the middle electrode 213, allowing plasma to be generated in the respective dielectric layers 211 and 214. The upper electrode 212 and lower electrode 215 are at the same potential. On the other hand, the middle electrode 213 is at a different potential than the upper electrode 212 and lower electrode 215. The outer diameters and thicknesses of the dielectric layers 211 and 214, the upper electrode 212, the middle electrode 213, and the lower electrode 215 can be appropriately modified within a range that does not cause abnormal discharge. For example, the outer diameters of the upper electrode 212, the middle electrode 213, and the lower electrode 215 may be set to be the same. A slight potential difference may also be provided between the upper electrode 212 and the lower electrode 215. This can induce electron flow.

[0061] The gas flow section 220 is a component that can flow gas inside the plasma generation section 210 in order to continuously process the gas with plasma. The gas flow section 220 allows gas to flow in from one end, along the axial direction, and discharges the gas from the other end. There are no particular restrictions on the gas flow section 220 as long as it is a component that can supply gas to the plasma generation section 210, allow the gas to pass through the space inside the plasma generation section 210, and then discharge the plasma-treated gas.

[0062] The power supply unit (not shown) applies an AC voltage between the upper electrode 212 and the middle electrode 213, which face each other with the dielectric layer 211 in between, and also applies an AC voltage between the middle electrode 213 and the lower electrode 215, which face each other with the dielectric layer 214 in between. The power supply unit is not particularly limited as long as it can apply an AC voltage of a predetermined voltage at a predetermined frequency to each electrode of the plasma generation unit 210; known power supply devices can be used. The frequency of the AC voltage is preferably 50Hz to 30MHz, more preferably 50Hz to 100kHz. Furthermore, the AC voltage is preferably 0.1 to 50kV, more preferably 0.2 to 10kV.

[0063] <Effects and Effects> Next, the effects of the plasma processing apparatus 200 according to this embodiment will be described. When an AC voltage is applied between the upper electrode 212 and the middle electrode 213 that sandwich the dielectric layer 211, plasma is generated within the dielectric layer 211 sandwiched between them. Also, when an AC voltage is applied between the middle electrode 213 and the lower electrode 215 that sandwich the dielectric layer 214, plasma is generated within the dielectric layer 214 sandwiched between them.

[0064] Furthermore, plasma is also generated near the walls (cross-sections) of each of the communication holes 212a, 213a, and 215a. When an AC voltage is applied between two electrode layers, plasma is generally more easily generated from the protruding edges of the electrode layers than from the flat surfaces of the electrode layers. Therefore, in the plasma generation unit 210, more plasma is more easily generated near the walls (cross-sections) of the communication holes 212a and 213a than from inside the dielectric layer 211 between the two electrode layers. Also, in the plasma generation unit 210, more plasma is more easily generated near the walls (cross-sections) of the communication holes 213a and 215a than from inside the dielectric layer 214 between the two electrode layers.

[0065] According to the plasma processing apparatus 200 of this embodiment described above, a gas flow section 220 is arranged in the center of the plasma generation section 210 parallel to the direction in which the alternating current is applied, and gas can be circulated in the same direction (generally parallel) as the layer thickness direction of the upper electrode 212, middle electrode 213, and lower electrode 215. This increases the degree of design freedom.

[0066] Furthermore, the electrode layers (upper electrode 212, middle electrode 213, and lower electrode 215) are provided with communication holes 212a, 213a, and 215a, respectively, through which the dielectric layers 211 and 214 are exposed. This allows the plasma generated near the hole walls (cross-sections) of the electrode layers within the communication holes 212a, 213a, and 215a to efficiently plasma-treat the gas flowing inside the plasma generation unit 210.

[0067] Furthermore, in this embodiment, since three electrode layers are provided to create a multi-stage structure, the plasma reaction can be promoted. This increases the plasma generation efficiency. The electrode layers may be set to four or more layers. This further increases the plasma generation efficiency.

[0068] <Third Embodiment> Next, a plasma processing apparatus according to the third embodiment of the present invention will be described. As shown in Figures 11 and 12, the plasma processing apparatus 300 according to this embodiment comprises a plasma generation unit 110, a gas flow unit 320, and a power supply unit (not shown). The plasma generation unit 110 in this embodiment is the same as in the first embodiment. The third embodiment will be described focusing on the differences from the first embodiment.

[0069] The gas flow section 320 in this embodiment is composed of a plurality of cylindrical bodies 321. The cylindrical bodies 321 are made of an insulator, have a cylindrical shape, and are arranged to penetrate the dielectric layer 111, the upper electrode 112, and the lower electrode 113 in the thickness direction. The outer surface of each cylindrical body 321 is in contact with the dielectric layer 111 and is spaced apart from the inner edges of the upper electrode 112 and the lower electrode 113.

[0070] Thus, even if the gas flow section 320 is composed of multiple cylindrical bodies 321, substantially the same effects as those of the first embodiment described above can be obtained.

[0071] <Fourth Embodiment> Next, a plasma processing apparatus according to the fourth embodiment of the present invention will be described. As shown in Figures 13 and 14, the plasma processing apparatus 400 according to this embodiment comprises a plasma generation unit 410, a gas flow unit 420, and a power supply unit (not shown). The plasma generation unit 410 of this embodiment is in a form without both an upper mask layer and a lower mask layer, as in the second modified example described above. The plasma processing apparatus of this embodiment differs from the first embodiment in that it does not have a cylindrical body. This embodiment will be described mainly in terms of the parts that differ from the first embodiment.

[0072] The dielectric layer 411 has a layered and donut-shaped structure. A communication hole 411a is formed in the center of the dielectric layer 411, penetrating in the direction of the layer thickness. The upper electrode 412 is laminated on top of the dielectric layer 411 and has a layered and donut-shaped structure. A communication hole 412a is formed in the upper electrode 412, penetrating in the direction of the layer thickness. The lower electrode 413 is laminated below the dielectric layer 411 and has a layered and donut-shaped structure. A communication hole 413a is formed in the lower electrode 413, penetrating in the direction of the layer thickness.

[0073] The gas flow section 420 is formed by interconnected communication holes 411a, 412a, and 413a, and is a region through which air flows in the thickness direction of the layer. As shown in Figure 14, the distance D1 from the inner edge of the dielectric layer 411 to the inner edge of the upper electrode 412 is set to an extent that does not cause abnormal discharge. Similarly, the distance D2 from the inner edge of the dielectric layer 411 to the inner edge of the lower electrode 413 is set to an extent that does not cause abnormal discharge. Distances D1 and D2 may be set to the same dimension.

[0074] As in this embodiment, the gas flow section 420 may not have a cylindrical body and may be configured so that air flows through a plurality of communication holes. Even in this configuration, the gas passing through the gas flow section 420 can be plasma-treated, thus achieving substantially the same effects as in the first embodiment. Furthermore, this embodiment reduces the number of parts.

[0075] Although embodiments and modifications of the present invention have been described above, the design can be modified as appropriate without violating the spirit of the invention. For example, in the fourth embodiment, the electrode layer may be composed of three or more layers, similar to the third embodiment. This makes it possible to further increase the plasma generation efficiency. [Explanation of Symbols]

[0076] 10 Plasma generation unit 11 Dielectric layer 12 Upper layer electrode (electrode layer) 13 Lower electrode (electrode layer) 14 Upper mask layer (mask layer) 15 Lower mask layer (mask layer) 16 Through holes 17 Through hole 100 Plasma Processing Equipment 110 Plasma generation unit 111 Dielectric layer 112 Upper layer electrode (electrode layer) 113 Lower electrode (electrode layer) 120 Gas fluid section

Claims

1. A plasma generation unit that generates plasma, comprising at least a dielectric layer and a plurality of electrode layers provided on the front and back surfaces of the dielectric layer, A power supply unit that applies an AC voltage to the pair of electrode layers, A plasma processing apparatus comprising one or more cylindrical bodies penetrating the dielectric layer and the pair of electrode layers in the thickness direction, and a gas flow section through which gas flows in order to process the gas with plasma.

2. A plasma generation unit that generates plasma, comprising at least a dielectric layer and a plurality of electrode layers provided on the front and back surfaces of the dielectric layer, A power supply unit that applies an AC voltage to the pair of electrode layers, A plasma processing apparatus characterized by having communication holes that communicate in the thickness direction of the dielectric layer and the electrode layer, and a gas flow section for flowing gas inside the communication holes in order to process the gas with plasma.

3. The plasma processing apparatus according to claim 1 or 2, characterized in that the electrode layer is composed of three or more layers.

4. The plasma processing apparatus according to claim 1 or 2, characterized in that the outer edge of the dielectric layer protrudes outward from the outer edge of the electrode layer to prevent abnormal discharge from occurring.

5. The plasma processing apparatus according to claim 2, characterized in that the inner edge of the dielectric layer protrudes inward from the inner edge of the electrode layer to prevent abnormal discharge, and the outer edge of the dielectric layer protrudes outward from the outer edge of the electrode layer to prevent abnormal discharge.

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