JP2021048075A - Plasma generation device - Google Patents

Abstract

To provide a plasma generation device capable of efficiently irradiating an object to be treated with plasma while suppressing adverse influences upon the object to be treated.SOLUTION: A gas passage part 10 is provided with: a gas inlet T1 through which a gas is received; a gas outlet T2 through which the gas received from the gas inlet T1 is sent out; and a cavity part HL extending from the gas inlet T1 to the gas outlet T2 in a flow direction DF of the gas, and comprises a first dielectric part 11 and a second dielectric part 12 which are opposed to each other with the cavity part HL interposed therebetween. A first electrode 51 is to be impressed with a first potential and opposed to the cavity part HL via the first dielectric part 11. A second electrode 52 is to be impressed with a second potential which is different from the first potential, and opposed to the first electrode 51 via the first dielectric part 11, the cavity part HL and the second dielectric part 12 in at least one cross-sectional view that is vertical to the flow direction DF.SELECTED DRAWING: Figure 3

Description

The present invention relates to a plasma generator.

In recent years, the use of atmospheric pressure plasma has been promoted in various fields. For example, according to Patent Document 1, a non-equilibrium atmospheric pressure plasma is irradiated to the aqueous solution by a plasma generator for the purpose of obtaining an aqueous solution having an antitumor effect. One of the illustrated plasma generators has a pair of counter electrodes arranged to face each other inside the housing. When argon is introduced from the gas inlet of the housing and a voltage is applied between the electrodes, plasma is generated inside the housing. The plasma is applied to the outside of a large number of gas outlets formed in the housing. By forming these gas outlets along one direction, plasma can be ejected linearly.

Japanese Unexamined Patent Publication No. 2016-169164

The plasma generator ejects linear plasma instead of point-shaped plasma. Therefore, this device is suitable for efficient plasma processing over a wide area. On the other hand, in order to generate plasma, this device causes gas to flow inside the housing from the gas introduction port toward the gas outlet, and applies a voltage to a pair of counter electrodes arranged inside the housing. At this time, since the electrode is directly exposed to the plasma, foreign matter from the electrode is likely to be mixed into the plasma, and the foreign matter may adversely affect the object to be processed. Further, since both electrodes are inside the housing portion, the electrodes are not blocked by the housing portion. Therefore, a relatively large current easily flows between the electrodes via the object to be processed, and this current may adversely affect the object to be processed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a plasma generator capable of efficiently irradiating a processed object with plasma while suppressing an adverse effect on the object to be processed. To provide.

The first aspect is a plasma generator, which has a gas path portion, a first electrode, and a second electrode. The gas path portion is provided with a gas inlet that receives gas, a gas outlet that sends out the received gas from the gas inlet, and a cavity portion that extends from the gas inlet to the gas outlet along the gas flow direction. It has a first dielectric portion and a second dielectric portion that face each other via a cavity portion. The first electrode is to which the first potential is applied, and faces the cavity portion via the first dielectric portion. A second potential different from the first potential is applied to the second electrode, and in at least one cross-sectional view perpendicular to the flow direction, the first electrode has a first dielectric portion and a cavity portion. It faces the second dielectric portion via the second dielectric portion.

The second aspect is the plasma generator of the first aspect, wherein the first electrode has a flat first facing surface facing the first dielectric portion, and the second electrode is a second electrode. It has a flat second facing surface facing the dielectric portion, and each of the first facing surface and the second facing surface is parallel to one reference plane parallel to the flow direction.

The third aspect is the plasma generator of the second aspect, in which the cavity is sandwiched between the first electrode and the second electrode in the direction perpendicular to the flow direction in the plane layout parallel to the reference plane. It has an intermediate region, an inlet region extending from the gas inlet to the intermediate region, and an outlet region extending from the intermediate region to the gas outlet.

A fourth aspect is the plasma generator of the third aspect, wherein the intermediate region has a first position in the flow direction, a first dimension in a direction perpendicular to the flow direction, and a first dimension in the flow direction. The second position between the first position and the gas outlet has a second dimension in the direction perpendicular to the flow direction, and the first dimension is smaller than the second dimension.

A fifth aspect is the plasma generator of any one of the first to fourth aspects, further comprising a first counter electrode. The first potential is applied to the first counter electrode, and the first counter electrode faces the first electrode via the second dielectric portion, the cavity portion, and the first dielectric portion.

A sixth aspect is the plasma generator of the fifth aspect, further comprising a second counter electrode. The second counter electrode is to which the second potential is applied, and faces the second electrode via the first dielectric portion, the cavity portion, and the second dielectric portion.

A seventh aspect is the plasma generator of any one of the first to sixth aspects, further comprising a third electrode. The first potential is applied to the third electrode, and the third electrode faces the cavity portion via the first dielectric portion.

The eighth aspect is the plasma generator of any one of the first to sixth aspects, further comprising a third electrode, a fourth electrode, a first power source, and a second power source. A third potential is applied to the third electrode, and the third electrode faces the cavity portion via the first dielectric portion. A fourth potential different from the third potential is applied to the fourth electrode, and the fourth electrode faces the third electrode via the second dielectric portion, the cavity portion, and the first dielectric portion. There is. The first power supply applies a first AC voltage between the first electrode and the second electrode. The second power source applies a second AC voltage between the third electrode and the fourth electrode.

According to the first aspect, each of the first electrode and the second electrode and the cavity portion through which the gas flows are separated by the first dielectric portion and the second dielectric portion. As a result, since the first electrode and the second electrode are not directly exposed to the plasma, it is possible to prevent foreign matter from the first electrode and the second electrode from adversely affecting the object to be processed. Further, since the space between the first electrode and the second electrode is blocked by the first dielectric portion and the second dielectric portion, it is difficult for a relatively large current to flow between the electrodes via the object to be processed. It is prevented that the electric current adversely affects the object to be processed. From the above, the adverse effect on the object to be irradiated with plasma can be suppressed. Further, according to the first aspect, in at least one cross-sectional view perpendicular to the gas flow direction, the first electrode and the second electrode have the first dielectric portion, the cavity portion, and the second dielectric portion. They are facing each other through. With this arrangement, an electric field perpendicular to the gas flow direction is generated in the cavity, and the plasma generated by this electric field is efficiently pushed out by the gas flowing along the flow direction. Therefore, the plasma to be processed can be efficiently irradiated. From the above, it is possible to efficiently irradiate the object to be processed with plasma while suppressing the adverse effect on the object to be processed.

According to the second aspect, the gas flow can be widely diffused in the direction parallel to the reference plane. As a result, it is possible to obtain a plasma that spreads widely in a line parallel to the reference plane.

According to the third aspect, in the plane layout parallel to the reference plane, the cavity is formed from the intermediate region sandwiched between the first electrode and the second electrode in the direction perpendicular to the flow direction and from the gas inlet. It has an inlet region extending to the intermediate region and an outlet region extending from the intermediate region to the gas outlet. As a result, the plasma generated in the intermediate region is pushed out to the outlet region by the gas flow from the inlet region. Therefore, plasma can be efficiently ejected from the gas outlet.

According to the fourth aspect, the intermediate region has a first dimension in the direction perpendicular to the flow direction at the first position in the flow direction, and is between the first position in the flow direction and the gas outlet. At the second position, it has a second dimension in the direction perpendicular to the flow direction, and the first dimension is smaller than the second dimension. As a result, the plasma can be easily ignited in the intermediate region where the first electrode and the second electrode face each other with a relatively small first dimension. Furthermore, the plasma ignited at the relevant location moves along the gas flow direction, so that plasma is generated even in the intermediate region where the first electrode and the second electrode face each other in a relatively large second dimension. Can be made to. Therefore, the size of the plasma between the first electrode and the second electrode can be increased while facilitating the ignition of the plasma.

According to the fifth aspect, the plasma can be ignited more reliably by further providing the first counter electrode.

According to the sixth aspect, the plasma can be ignited more reliably by further providing the second counter electrode.

According to the seventh aspect, plasma can be generated in a wider range by further providing the third electrode.

According to the eighth aspect, it becomes easy to adjust the distribution of the electric field by providing not only the first power source but also the second power source. This makes it possible to improve the stability of the plasma.

It is a top view which shows roughly the structure of the plasma generator in Embodiment 1 of this invention. FIG. 5 is a schematic cross-sectional view taken along line II-II of FIG. It is a top view explaining the plane layout of the plasma generator of FIG. It is a top view which shows roughly the structure of the plasma generator in Embodiment 2 of this invention. It is a schematic cross-sectional view along the line VV of FIG. It is a top view which shows roughly the structure of the plasma generator in Embodiment 3 of this invention. FIG. 6 is a schematic cross-sectional view taken along the line VII-VII of FIG. It is a top view which shows roughly the structure of the plasma generator in Embodiment 4 of this invention. FIG. 5 is a schematic cross-sectional view taken along the line IX-IX of FIG. FIG. 5 is a plan view schematically showing the configuration of the plasma generator according to the fifth embodiment of the present invention. FIG. 5 is a schematic cross-sectional view taken along the line XI-XI of FIG. It is a top view which shows roughly the structure of the plasma generator in Embodiment 6 of this invention. It is a schematic cross-sectional view along the line XIII-XIII of FIG. It is a top view which shows roughly the structure of the plasma generator in the reference example. FIG. 6 is a schematic cross-sectional view taken along the line XV-XV of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience of explanation of the direction, the xyz Cartesian coordinate system is shown in each figure. In the drawings below, the same or corresponding parts will be given the same reference number and the explanation will not be repeated.

<Embodiment 1>
FIG. 1 is a plan view schematically showing the configuration of the plasma generator 91 according to the first embodiment. FIG. 2 is a schematic cross-sectional view taken along line II-II of FIG. The plasma generator 91 includes a gas path portion 10, a first electrode 51, a second electrode 52, a first counter electrode 51p, a second counter electrode 52p, a gas supply unit 20, and a power supply 61 (first power supply). ) And.

The gas supply unit 20 supplies gas to the gas path unit 10. The gas is, for example, a rare gas, a nitrogen gas, or air, preferably a rare gas such as argon gas or helium gas. By using the rare gas, it becomes easy to ignite the plasma, and it becomes easy to eject the plasma to the outside of the plasma generator 91.

The gas path portion 10 has a gas inlet T1 that receives gas from the gas supply unit 20, a gas outlet T2 that sends out the received gas from the gas inlet T1, and a gas flow direction DF from the gas inlet T1 to the gas outlet T2. A cavity HL extending along (in the y direction in FIG. 2) is provided. The gas path portion 10 has a first dielectric portion 11, a second dielectric portion 12, and a spacer 13 in order to obtain this configuration. The first dielectric portion 11 and the second dielectric portion 12 face each other via the cavity portion HL. Specifically, each of the first dielectric portion 11 and the second dielectric portion 12 is a flat plate that spreads parallel to the xy plane and has a thickness in the z direction, and these are opposed to each other at intervals in the z direction. ing. The spacer 13 seals a portion of the edge of the cavity HL other than the gas inlet T1 and the gas outlet T2, thereby defining the flow direction DF.

The gas from the gas supply unit 20 is preferably a rare gas as described above. In that case, it is desired to suppress the gas flow rate in order to suppress the process cost. The gas flow rate can be suppressed as the thickness (dimension in the z direction) of the cavity HL becomes smaller. From this viewpoint, the thickness of the cavity HL is preferably 0.1 mm or more and 1 mm or less.

The first dielectric portion 11 and the second dielectric portion 12 are made of a dielectric having high plasma resistance, for example, quartz or ceramic. The spacer 13 may be made of the same material. The first dielectric portion 11, the second dielectric portion 12, and the spacer 13 do not necessarily have to be separate members. For example, the entire first dielectric portion 11, the second dielectric portion 12, and the spacer 13 may be one member made of the same material.

The power supply 61 generates a first potential and a second potential different from the first potential from each of the first terminal and the second terminal. Specifically, the power source 61 is an AC power source, and generates an AC voltage between the first potential and the second potential.

The first electrode 51 is to which the first potential is applied by the power source 61. The first electrode 51 faces the cavity HL via the first dielectric portion 11. In FIG. 2, the first electrode 51 is provided directly on the upper surface of the first dielectric portion 11.

A second potential is applied to the second electrode 52 by the power supply 61. The second electrode 52 is connected to the first electrode 51 via the first dielectric portion 11, the cavity portion HL, and the second dielectric portion 12 in at least one cross-sectional view (FIG. 2) perpendicular to the flow direction DF. Opposing. As shown in FIG. 2, the direction in which the first electrode 51 and the second electrode 52 face each other is preferably inclined with respect to the thickness direction (z direction). In FIG. 2, the second electrode 52 is provided directly on the lower surface of the second dielectric portion 12.

The first potential is applied to the first counter electrode 51p. The first counter electrode 51p faces the first electrode 51 via the second dielectric portion 12, the cavity portion HL, and the first dielectric portion 11. The direction in which the first electrode 51 and the first counter electrode 51p face each other is preferably along the thickness direction (z direction) as shown in FIG. In FIG. 2, the first counter electrode 51p is provided directly on the lower surface of the second dielectric portion 12.

A second potential is applied to the second counter electrode 52p. The second counter electrode 52p faces the second electrode 52 via the first dielectric portion 11, the cavity portion HL, and the second dielectric portion 12. The direction in which the second electrode 52 and the second counter electrode 52p face each other is preferably along the thickness direction (z direction) as shown in FIG. In FIG. 2, the second counter electrode 52p is provided directly on the upper surface of the first dielectric portion 11.

The first electrode 51 has a flat first facing surface (lower surface in FIG. 2) facing the first dielectric portion 11. The second electrode 52 has a flat second facing surface (upper surface in FIG. 2) facing the second dielectric portion 12. Each of the first facing surface (lower surface in FIG. 2) of the first electrode 51 and the second facing surface (upper surface in FIG. 2) of the second electrode 52 is a reference plane parallel to the flow direction DF, that is, an xy plane. Is parallel to. The first counter electrode 51p has a flat surface (upper surface in FIG. 2) facing the second dielectric portion 12, and this surface is parallel to the reference plane (xy plane). The second counter electrode 52p has a flat surface (lower surface in FIG. 2) facing the first dielectric portion 11, and this surface is parallel to the reference plane (xy plane).

FIG. 3 is a plan view showing a plane layout of the plasma generator 91 parallel to the xy plane (reference plane). In FIG. 3, the cavity HL has an inlet region HL1, an outlet region HL2, an intermediate region HL3, and a peripheral region HL4. The intermediate region HL3 is sandwiched between the first electrode 51 and the second electrode 52 in the x direction (direction perpendicular to the flow direction DF). The inlet region HL1 extends from the gas inlet T1 to the intermediate region HL3. The outlet region HL2 extends from the intermediate region HL3 to the gas outlet T2. The peripheral region HL4 is a region outside the inlet region HL1, the exit region HL2, and the intermediate region HL3, and may be omitted.

The larger the width (dimension in the x direction) of the intermediate region HL3, the larger the width of the plasma PL can be. On the other hand, if this width is excessively large, it becomes difficult to ignite the plasma. From this point of view, the width of the intermediate region HL3 is preferably 10 mm or more and 30 mm or less. In this case, a jet of plasma PL having a width of 10 mm or more and 30 mm or less can be obtained.

According to the present embodiment, each of the first electrode 51 and the second electrode 52 and the cavity portion HL through which the gas flows are separated by the first dielectric portion 11 and the second dielectric portion 12. .. As a result, the first electrode 51 and the second electrode 52 are not directly exposed to the plasma, so that foreign matter from the first electrode 51 and the second electrode 52 is prevented from adversely affecting the object to be processed. Further, since the space between the first electrode 51 and the second electrode 52 is blocked by the first dielectric portion 11 and the second dielectric portion 12, a relatively large current flows between the electrodes via the object to be processed. It is difficult, and thus it is prevented that this current adversely affects the object to be processed. From the above, the adverse effect on the object to be irradiated with the plasma PL can be suppressed. Further, according to the present embodiment, in at least one cross-sectional view (FIG. 2) perpendicular to the gas flow direction DF, the first electrode 51 and the second electrode 52 are the first dielectric portion 11 and the cavity portion. The HL and the second dielectric portion 12 face each other via the second dielectric portion 12. With this arrangement, an electric field perpendicular to the gas flow direction DF is generated in the cavity HL, and the plasma generated by this electric field is efficiently pushed out by the gas flowing along the flow direction DF. Therefore, the plasma PL can be efficiently irradiated to the object to be processed. From the above, it is possible to efficiently irradiate the object to be processed with plasma while suppressing the adverse effect on the object to be processed.

The first electrode 51 and the second counter electrode 52p have a flat surface facing the first dielectric portion 11, and the second electrode 52 and the first counter electrode 51p face the second dielectric portion 12. When the flat surface is provided, a flat plate can be used as each of the first dielectric portion 11 and the second dielectric portion 12. Thereby, the gas flow can be widely diffused in the direction parallel to the flat plate, specifically, the x direction. As a result, it is possible to obtain a plasma PL (FIG. 1) that spreads widely in a line parallel to the x direction.

In the plane layout (FIG. 2), the cavity HL has an intermediate region HL3 sandwiched between the first electrode 51 and the second electrode 52 in a direction perpendicular to the flow direction DF, and from the gas inlet T1 to the intermediate region HL3. It has an extending inlet region HL1 and an outlet region HL2 extending from the intermediate region HL3 to the gas outlet T2. As a result, the plasma generated in the intermediate region HL3 is pushed out to the outlet region HL2 by the gas flow from the inlet region HL1. Therefore, the plasma PL can be efficiently ejected from the gas outlet T2. In other words, the plasma jet can be obtained efficiently.

By further providing the first counter electrode 51p in addition to the first electrode 51 as the electrode to which the first potential is applied, the ignition of the plasma can be performed more reliably. Further, by further providing the second counter electrode 52p in addition to the second electrode 52 as the electrode to which the second potential is applied, the ignition of the plasma can be performed more reliably.

<Embodiment 2>
FIG. 4 is a plan view schematically showing the configuration of the plasma generator 92 according to the second embodiment. FIG. 5 is a schematic cross-sectional view taken along the line VV of FIG.

The plasma generator 92 further includes a third electrode 51A and a third counter electrode 51Ap in addition to the configuration of the plasma generator 91 according to the first embodiment described above. Like the first electrode 51, the third electrode 51A is to which the first potential is applied, and faces the cavity portion HL via the first dielectric portion 11.

As with the first counter electrode 51p, the first potential is applied to the third counter electrode 51Ap. The third counter electrode 51Ap faces the third electrode 51A via the second dielectric portion 12, the cavity portion HL, and the first dielectric portion 11. The direction in which the third electrode 51A and the third counter electrode 51Ap face each other is preferably along the thickness direction (z direction) as shown in FIG. In FIG. 5, the third electrode 51A is provided directly on the upper surface of the first dielectric portion 11, and the third counter electrode 51Ap is provided directly on the lower surface of the second dielectric portion 12.

According to the present embodiment, the plasma PL can be generated in a wider range by further providing the third electrode 51A and the third counter electrode 51Ap as compared with the first embodiment. Specifically, the width of the plasma PL in the x direction can be doubled or more as compared with the first embodiment.

<Embodiment 3>
FIG. 6 is a plan view schematically showing the configuration of the plasma generator 93 according to the third embodiment. FIG. 7 is a schematic cross-sectional view taken along line VII-VII of FIG. The plasma generator 93 corresponds to a configuration in which the first counter electrode 51p, the second counter electrode 52p, and the third counter electrode 51Ap are omitted from the plasma generator 92 (FIGS. 4 and 5) according to the second embodiment described above. are doing. According to the present embodiment, the electrode structure and the wiring structure can be simplified as compared with the second embodiment.

<Embodiment 4>
FIG. 8 is a plan view schematically showing the configuration of the plasma generator 94 according to the fourth embodiment. FIG. 9 is a schematic cross-sectional view taken along the line IX-IX of FIG. The plasma generator 94 further includes a fourth electrode 52A and a fourth counter electrode 52Ap in addition to the configuration of the plasma generator 92 (FIGS. 4 and 5) according to the second embodiment described above.

Like the second electrode 52, the fourth electrode 52A is to which the second potential is applied. The fourth electrode 52A faces the third electrode 51A via the second dielectric portion 12, the cavity portion HL, and the first dielectric portion 11. A second potential is applied to the fourth counter electrode 52Ap as in the case of the second counter electrode 52p. The fourth counter electrode 52Ap faces the fourth electrode 52A via the first dielectric portion 11, the cavity portion HL, and the second dielectric portion 12. The direction in which the fourth electrode 52A and the fourth counter electrode 52Ap face each other is preferably along the thickness direction (z direction) as shown in FIG. In FIG. 9, the fourth electrode 52A is provided directly on the lower surface of the second dielectric portion 12, and the fourth counter electrode 52Ap is provided directly on the upper surface of the first dielectric portion 11.

According to the present embodiment, the plasma PL can be generated in a wider range by further providing the fourth electrode 52A and the fourth counter electrode 52Ap as compared with the second embodiment. Specifically, the width of the plasma PL in the x direction can be 1.5 times or more that of the second embodiment. It is also possible to further increase the width of the plasma PL by adding more electrodes.

<Embodiment 5>
FIG. 10 is a plan view schematically showing the configuration of the plasma generator 95 according to the fifth embodiment. FIG. 11 is a schematic cross-sectional view taken along the line XI-XI of FIG. In addition to the configuration of the plasma generator 91 according to the first embodiment, the plasma generator 95 further includes a third electrode 53, a fourth electrode 54, a third counter electrode 53p, and a fourth counter electrode 54p. It has a power source 62 (second power source).

The third electrode 53 faces the cavity HL via the first dielectric portion 11. The fourth electrode 54 faces the third electrode 53 via the second dielectric portion 12, the cavity portion HL, and the first dielectric portion 11. The power supply 61 applies a first AC voltage between the first electrode 51 and the second electrode 52. The power supply 62 applies a second AC voltage between the third electrode 53 and the fourth electrode 54. The first AC voltage and the second AC voltage may be different from each other. It is preferable that the power supply 61 and the power supply 62 are configured to be able to control the voltage independently of each other.

A first potential is applied to the third counter electrode 53p as in the case of the first counter electrode 51p. The third counter electrode 53p faces the third electrode 53 via the second dielectric portion 12, the cavity portion HL, and the first dielectric portion 11. The direction in which the third electrode 53 and the third counter electrode 53p face each other is preferably along the thickness direction (z direction) as shown in FIG. In FIG. 11, the third electrode 53 is provided directly on the upper surface of the first dielectric portion 11, and the third counter electrode 53p is provided directly on the lower surface of the second dielectric portion 12.

A second potential is applied to the fourth counter electrode 54p as in the case of the second counter electrode 52p. The fourth counter electrode 54p faces the fourth electrode 54 via the first dielectric portion 11, the cavity portion HL, and the second dielectric portion 12. The direction in which the fourth electrode 54 and the fourth counter electrode 54p face each other is preferably along the thickness direction (z direction) as shown in FIG. In FIG. 11, the fourth electrode 54 is provided directly on the lower surface of the second dielectric portion 12, and the fourth counter electrode 54p is provided directly on the upper surface of the first dielectric portion 11.

In a plane layout parallel to the xy plane (reference plane), the third electrode 53 and the fourth electrode 54 may be arranged between the first electrode 51 and the second electrode 52 in the x direction. In that case, the third electrode 53 is preferably arranged between the second electrode 52 and the fourth electrode 54 in the x direction, and the fourth electrode 54 is the first electrode 51 and the third electrode 53 in the x direction. It is preferable that it is arranged between and.

According to the present embodiment, as compared with the first embodiment, the plasma PL is provided in a wider range by further providing the third electrode 53, the fourth electrode 54, the third counter electrode 53p, and the fourth counter electrode 54p. Can be generated. Further, by providing the power supply 62 as well as the power supply 61, it becomes easy to adjust the distribution of the electric field. Thereby, the stability of the plasma PL can be improved.

<Embodiment 6>
FIG. 12 is a plan view schematically showing the configuration of the plasma generator 96 according to the sixth embodiment. FIG. 13 is a schematic cross-sectional view taken along line XIII-XIII of FIG.

As described with reference to FIG. 3, the plasma generator 91 according to the first embodiment described above has an inlet region HL1, an outlet region HL2, and an intermediate region HL3. On the other hand, the plasma generator 96 in the present embodiment has an inlet region HLC1, an outlet region HLC2, and an intermediate region HLC3. The intermediate region HLC3 has the first dimension ST1 in the x direction (that is, the direction perpendicular to the flow direction DF) at the first position in the y direction (that is, the flow direction DF), and has the first dimension ST1 in the y direction. It has a second dimension ST2 in the x direction at a second position between and the gas outlet T2. The first dimension ST1 is smaller than the second dimension ST2.

As the position in the y direction approaches the exit region HLC2, the dimensions of the intermediate region HLC3 at that position in the x direction change continuously rather than discontinuously. Specifically, as the position in the y direction approaches the exit region HLC2, the dimension of the intermediate region HLC3 at that position in the x direction gradually increases. As a modification, the intermediate region may include a portion whose dimensions are constant with respect to a change in position in the y direction.

In the plasma ignition step of the plasma generator 96, ignition occurs first in the portion of the intermediate region HLC3 having the first dimension ST1 (the portion having a relatively small dimension in the x direction). As a result, first, of the portion of the first dimension ST1 and the portion of the second dimension ST2, plasma is generated only in the former. When this plasma is pushed by the gas flowing in the flow direction DF, the plasma spreads to the portion of the second dimension ST2. As a result, the plasma PL having a width of about the second dimension ST2 is ejected from the gas outlet T2 of the plasma generator 96.

According to the plasma generator 96 of the present embodiment, the plasma can be easily ignited in the intermediate region HLC3 where the first electrode 51C and the second electrode 52C face each other in the relatively small first dimension ST1. be able to. Further, the plasma ignited at the relevant portion moves along the gas flow direction DF, so that the portion where the first electrode 51C and the second electrode 52C face each other in the relatively large second dimension ST2 in the intermediate region HLC3. However, plasma can be generated. Therefore, the size of the plasma between the first electrode 51C and the second electrode 52C can be increased while facilitating the ignition of the plasma. For example, by doubling or more of the second dimension ST2 as compared with the first dimension ST1, the width of the plasma PL in the x direction can be doubling or more as compared with the first embodiment.

Further, according to the present embodiment, unlike the plasma generator 92 (FIGS. 4 and 5) of the second embodiment, the distribution of plasma in the width direction (x direction) is not divided by the electrodes. Therefore, it is possible to obtain a jet of plasma PL having high uniformity in the width direction. On the other hand, in the case of the plasma generator 92 (FIGS. 4 and 5), the second electrode 52 and the second counter electrode 52p divide the distribution of plasma in the width direction (x direction), and as a result, plasma. This leads to uneven strength of the PL jet in the width direction. If the widths of the second electrode 52 and the second counter electrode 52p are reduced, this strength unevenness can be suppressed.

FIG. 14 is a plan view schematically showing the configuration of the plasma generator 96R in the reference example. FIG. 15 is a schematic cross-sectional view taken along the line XV-XV of FIG. The plasma generator 96R includes a first rear-stage electrode 51J, a first rear-stage counter electrode 51Jp, a second rear-stage electrode 52J, a second rear-stage counter electrode 52Jp, a first front-stage electrode 51K, and a first front-stage counter electrode 51Kp. It has a second front-stage electrode 52K and a second front-stage counter electrode 52Kp.

In the planar layout, the gas flowing along the flow direction DF (FIG. 14) passes through the region of the first dimension ST1 to which the voltage is applied, and then passes through the region of the second dimension ST2 to which the voltage is applied in the same manner. Therefore, for the gas flowing in the flow direction DF, the magnitude of the dimension to which the voltage is applied increases discontinuously from the first dimension ST1 to the second dimension ST2.

In the plasma ignition step of the plasma generator 96R, ignition occurs at the portion of the first dimension ST1 (the portion where the dimension in the x direction is relatively small). As a result, plasma is generated only in the former of the portion of the first dimension ST1 and the portion of the second dimension ST2. Although this plasma is pushed by the gas flowing in the flow direction DF, it is difficult to spread to the portion of the second dimension ST2 due to the discontinuity of the dimensions. As a result, it may be possible to obtain only a plasma PL having a width of about the first dimension ST1 instead of the second dimension ST2.

On the other hand, according to the plasma generator 96 of the present embodiment, as described above, the dimensions of the intermediate region HLC3 in the x direction change continuously rather than discontinuously. As a result, unlike the plasma generator 96R, the width of the plasma is smoothly increased after the plasma is ignited. Therefore, the width of the plasma PL can be expanded more reliably.

Although the present invention has been described in detail, the above description is exemplary in all aspects and the invention is not limited thereto. It is understood that innumerable variations not illustrated can be assumed without departing from the scope of the present invention. The configurations described in the above embodiments and the modifications can be appropriately combined or omitted as long as they do not conflict with each other.

10: Gas path part 11: First dielectric part 12: Second dielectric part 13: Spacer 20: Gas supply part 51, 51C: First electrode 51A, 53: Third electrode 51Ap, 53p: Third counter electrode 51p : 1st counter electrode 52, 52C: 2nd electrode 52A, 54: 4th electrode 52Ap, 54p: 4th counter electrode 52p: 2nd counter electrode 61: Power supply (1st power supply)
62: Power supply (second power supply)
91-96: Plasma generator DF: Flow direction HL: Cavity HL1, HLC1: Inlet area HL2, HLC2: Outlet area HL3, HLC3: Intermediate area HL4: Peripheral area

Claims (8)

A gas inlet that receives gas, a gas outlet that sends out the gas received from the gas inlet, and a cavity extending from the gas inlet to the gas outlet along the gas flow direction are provided. A gas path portion having a first dielectric portion and a second dielectric portion facing each other via a cavity portion,
A first potential is applied, and the first electrode facing the cavity via the first dielectric portion and the first electrode
A second potential different from the first potential is applied, and in at least one cross-sectional view perpendicular to the flow direction, the first dielectric portion and the cavity portion are attached to the first electrode. With the second electrode facing the second dielectric portion,
A plasma generator equipped with. The first electrode has a flat first facing surface facing the first dielectric portion, and the second electrode has a flat second facing surface facing the second dielectric portion. The plasma generator according to claim 1, wherein each of the first facing surface and the second facing surface is parallel to one reference plane parallel to the flow direction. In a plane layout parallel to the reference plane, the cavity is an intermediate region sandwiched between the first electrode and the second electrode in a direction perpendicular to the flow direction, and an intermediate region from the gas inlet to the intermediate region. The plasma generator according to claim 2, further comprising an inlet region extending to and an outlet region extending from the intermediate region to the gas outlet. The intermediate region
At the first position in the flow direction, it has the first dimension in the direction perpendicular to the flow direction.
A second position between the first position and the gas outlet in the flow direction has a second dimension in a direction perpendicular to the flow direction, and the first dimension is smaller than the second dimension. ,
The plasma generator according to claim 3. The first potential is applied, and the first counter electrode facing the first electrode is further provided via the second dielectric portion, the cavity portion, and the first dielectric portion. The plasma generator according to any one of claims 1 to 4. The second potential is applied, and a second counter electrode facing the second electrode is further provided via the first dielectric portion, the cavity portion, and the second dielectric portion. The plasma generator according to claim 5. The invention according to any one of claims 1 to 6, wherein the first potential is applied, and a third electrode facing the cavity via the first dielectric portion is further provided. Plasma generator. A third electrode facing the cavity via the first dielectric,
A fourth electrode facing the third electrode via the second dielectric portion, the cavity portion, and the first dielectric portion,
A first power source that applies a first AC voltage between the first electrode and the second electrode, and
A second power source that applies a second AC voltage between the third electrode and the fourth electrode, and
The plasma generator according to any one of claims 1 to 6, further comprising.

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