CN109585250B - Plasma processing apparatus - Google Patents

Abstract

Provided is a plasma processing apparatus, comprising: a holding portion that holds a workpiece; and an electrode portion that is opposed to at least a part of an inner wall surface of the hole in a radial direction at least inside the hole of the workpiece.

Description

Plasma processing apparatus

Technical Field

The present invention relates to a plasma processing apparatus.

Background

Conventionally, a technique of generating plasma under atmospheric pressure has been developed, and in recent years, processing using plasma has been performed on workpieces of various shapes.

For example, japanese patent application laid-open No. 2009-272165 discloses an example of a plasma processing apparatus that generates plasma at atmospheric pressure. The plasma processing apparatus has a cylindrical space as a discharge space. The internal pressure of the cylindrical space is atmospheric pressure. The process gas is introduced into the cylindrical space from a process gas supply source. When a voltage is applied from a power supply to the electrodes, a discharge is formed in the cylindrical space under atmospheric pressure. Thereby, the processing gas introduced into the cylindrical space is converted into plasma. The plasma-converted processing gas is blown out from the cylindrical space toward the workpiece and contacts the surface of the workpiece. Thereby, a desired surface treatment can be performed.

The plasma processing apparatus disclosed in japanese patent application laid-open No. 2009-272165 is a so-called remote system apparatus as follows: plasma is generated in a space away from the workpiece, and the plasma is transferred to the workpiece, thereby performing a desired process on the workpiece.

Here, generally, when a metal workpiece is drilled, cutting oil adheres to and remains on the inner wall surface of the hole. Although the residual cutting oil is removed by a cleaning liquid or the like, particularly when the hole diameter is small, a sufficient cleaning effect may not be obtained, and the cutting oil may remain. In this case, when the member is fixed to the cleaned hole with an adhesive, wettability may be reduced due to surface contamination by the cutting oil, and sufficient adhesive strength may not be obtained.

Therefore, it is expected that the surface contamination caused by the cutting oil is removed by the plasma treatment. However, when the remote plasma processing apparatus as described in japanese patent application laid-open No. 2009-272165 is used, there is a problem in introducing active species by plasma into the hole, and it is difficult to efficiently perform plasma processing of the hole of the workpiece.

Disclosure of Invention

In view of the above circumstances, an object of the present invention is to provide a plasma processing apparatus capable of efficiently performing plasma processing on a hole of a workpiece.

An exemplary plasma processing apparatus according to the present invention includes: a holding portion that holds a workpiece; and an electrode portion that is opposed to at least a part of an inner wall surface of the hole in a radial direction at least inside the hole of the workpiece.

Effects of the invention

According to the exemplary plasma processing apparatus of the present invention, it is possible to efficiently perform the plasma processing on the hole of the workpiece.

The above and other features, elements, steps, features and advantages of the present invention will be more clearly understood from the following detailed description of preferred embodiments of the present invention with reference to the accompanying drawings.

Drawings

Fig. 1 is a diagram showing an overall configuration of a plasma processing apparatus according to an embodiment of the present invention.

Fig. 2 is a vertical cross-sectional view showing the structure of the holding portion and the electrode portion according to embodiment 1.

Fig. 3A is a diagram showing a state in which a workpiece is set in the holding portion shown in fig. 2.

Fig. 3B is a perspective view of the workpiece.

Fig. 4 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 2 of the present invention.

Fig. 5 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 3 of the present invention.

Fig. 6 is a plan view of the electrode portion according to embodiment 4 of the present invention as viewed from above the workpiece.

Fig. 7 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 5 of the present invention.

Fig. 8 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 6 of the present invention.

Fig. 9 is a diagram showing a configuration in a state where the workpiece is held by the workpiece holder in the configuration shown in fig. 8.

Fig. 10 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 7 of the present invention.

Fig. 11 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 8 of the present invention.

Fig. 12 is a longitudinal sectional view showing the structure of an embodiment of the present invention adopting the remote mode.

Fig. 13 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 9 of the present invention.

Fig. 14 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 10 of the present invention.

Fig. 15 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 11 of the present invention.

Fig. 16 is a vertical sectional view showing the structure of the holding portion and the electrode portion according to embodiment 12 of the present invention.

Detailed Description

Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Hereinafter, the direction in which the center axis C extends is referred to as "axial direction", the X1 side in the axial direction is referred to as "upper side", and the X2 side in the axial direction is referred to as "lower side". The direction around the central axis is referred to as "circumferential direction", and the radial direction of the central axis is referred to as "radial direction".

< Overall Structure of plasma processing apparatus >

First, the overall configuration of a plasma processing apparatus according to an exemplary embodiment of the present invention will be described with reference to fig. 1. Fig. 1 is a diagram schematically showing the overall configuration of a plasma processing apparatus 10 according to the present embodiment.

A plasma processing apparatus 10 shown in fig. 1 generates plasma under atmospheric pressure to perform plasma processing on a workpiece 1 made of metal as a processing object. More specifically, a through hole (not shown in fig. 1) provided in the workpiece 1 is subjected to plasma processing. The plasma processing apparatus 10 includes a holding unit 2, an electrode unit 3, a high-voltage power supply unit 4, a timer 5, an injector 6, an air supply unit 7, a flow meter 8, and a CCD camera 9.

The holding portion 2 holds the workpiece 1. As described later, the holding portion 2 forms a semi-closed space together with the workpiece 1. The electrode portion 3 is positioned with respect to the holding portion 2, and in a state where the workpiece 1 is held by the holding portion 2, the electrode portion 3 is inserted into the through hole of the workpiece 1.

The high-voltage power supply unit 4 applies a high-frequency high voltage to the electrode unit 3. That is, an alternating voltage is applied to the electrode portion 3. On the other hand, a ground potential is applied to the holding portion 2, and a ground potential is applied to the metal workpiece 1 via the holding portion 2. Since the process gas is introduced into the through-hole, discharge is generated inside the through-hole, and plasma is generated. The electrode portion 3 and the high-voltage power supply portion 4 constitute a plasma generating portion.

The frequency of the voltage applied by the high-voltage power supply unit 4 is, for example, 1kHz to 100 kHz. The waveform of the voltage applied by the high-voltage power supply unit 4 is desirably a pulse waveform, but may be a sine wave, a rectangular wave, or the like, and may be a known waveform used for atmospheric pressure plasma discharge. The voltage applied by the high-voltage power supply unit 4 is, for example, 5 to 20kVpp, and is appropriately set in accordance with a gap between the electrode unit 3 and the through hole or the like.

The timer 5 measures the time during which the high-voltage power supply unit 4 applies a voltage to the electrode unit 3. That is, the processing time for performing the plasma processing on the workpiece 1 can be controlled by the timer 5.

The ejector 6 is a negative pressure generator connected to the exhaust port of the holding portion 2. The ejector 6 generates a high-speed airflow of air supplied from the air supply portion 7, thereby generating a negative pressure in a direction perpendicular to the airflow by the venturi effect. The gas in the internal space of the holding portion 2 is discharged by generating a negative pressure by the ejector 6. That is, the injector 6 functions as an exhaust unit. In addition, for example, a vacuum pump may be used instead of the ejector 6.

The flow meter 8 is disposed in the flow path between the exhaust port of the holder 2 and the injector 6. The flow meter 8 measures the flow rate of the gas flow flowing in the flow path. The CCD camera 9 images the light emission state of the plasma generated inside the through hole of the workpiece 1.

< embodiment of holding section and electrode section >

< embodiment 1>

Hereinafter, each embodiment of the specific configuration of the holding portion 2 and the electrode portion 3 in the plasma processing apparatus 10 described above will be described. In addition, the holding portion, the electrode portion, the workpiece, and the like in fig. 1 are appropriately changed in reference to the following modifications of the embodiment. Here, embodiment 1 will be described with reference to fig. 2, 3A, and 3B.

Fig. 2 is a vertical sectional view showing the structure of the holding portion 2 and the electrode portion 3 according to embodiment 1. As shown in fig. 2, the holding portion 2 has a work holder 21 and a housing 22. The work holder 21 has a substantially cylindrical shape and has an opening 211. The opening 211 is formed to penetrate in the axial direction around the center axis C. The work holder 21 is made of metal, and a ground potential is applied thereto.

The housing 22 is cylindrical with an upper opening, and supports the holding portion 2 from below. The work holder 21 and the housing 22 enclose an internal space 2S. That is, the holding portion 2 has an internal space 2S. Further, an exhaust port 221 is formed on a side surface of the housing 22.

The electrode portion 3 extends in the axial direction around the center axis C. The electrode portion 3 has a cylindrical portion 31 at the upper side. The entire outer peripheral surface of the cylindrical portion 31 is covered with the insulating material 15. That is, the insulating material 15 has a cylindrical shape. The insulating material 15 is preferably made of a ceramic material such as alumina or zirconia, or a free-cutting ceramic.

Both the cylindrical portion 31 and the insulating material 15 penetrate from the lower side of the opening 211 to the upper side of the opening 211.

Fig. 3A is a diagram showing a state in which the workpiece 1 is set in the holding portion shown in fig. 2. In this state, a semi-closed space is formed by the work 1 and the holding portion 2. Further, fig. 3B is a perspective view of the workpiece 1. The workpiece 1 is a metal member having: a substantially cylindrical base 11; a cylindrical protrusion 12 located below the base 11; and a flange portion 13 formed in an annular shape so as to protrude radially outward from an upper end portion of an outer peripheral surface of the base 11.

The workpiece 1 has a recess 1A, a recess 1B, and a through hole 1C penetrating in the axial direction. The upper end position of the columnar recess 1A coincides with the upper end position of the flange 13. The columnar recess 1B is disposed below the recess 1A so as to be continuous with the recess 1A. The columnar through-hole 1C is arranged below the recess 1B and continuous with the recess 1B. That is, the recess 1A, the recess 1B, and the through hole 1C communicate with each other.

The base 11 has an annular surface 111 as an annular surface at a lower end. The projection 12 projects downward from the radially inner side of the annular surface 111. The workpiece 1 is held by the holding portion 2 by placing the annular surface 111 on the upper end surface of the workpiece holder 21. At this time, the protrusion 12 is fitted into the opening 211.

The contact inner wall surface 211A, which is an inner wall surface of the opening 211 extending in the axial direction, is arranged to be able to contact the contact outer peripheral surface 121, which is an outer peripheral surface of the protrusion 12, thereby preventing the workpiece 1 from moving on a plane perpendicular to the axial direction.

Both the columnar portion 31 and the insulating material 15 pass through the through-hole 1C from the lower side of the through-hole 1C to the upper side of the through-hole 1C. That is, both the columnar portion 31 and the insulating member 15 face the entire inner wall surface of the through-hole 1C in the axial direction and the circumferential direction. In other words, the electrode portion 3 is radially opposed to the entire inner wall surface of the through hole 1C in the workpiece 1. In this case, it is desirable that the distance between the inner wall surface of the through hole 1C of the workpiece 1 and the insulating material 15, that is, the discharge gap is maintained uniform in the entire circumferential direction, and is set to be substantially equal to or smaller than 1mm, more preferably 0.1mm to 0.7 mm. This enables the plasma to maintain stable discharge even under atmospheric pressure. In addition, in the case where the distance is not uniform, plasma concentrates on a short-distance portion, and thus plasma processing performance is not uniform.

When the gas in the internal space 2S is discharged from the exhaust port 221 to the outside by the ejector 6 (fig. 1) connected to the exhaust port 221, the inside of the internal space 2S becomes a negative pressure. The upper side of the through hole 1C is the outside air side under atmospheric pressure. An air flow is generated which flows from the outside air side through the through-hole 1C to the internal space 2S. The process gas is guided from the outside air side to the through-holes 1C by the gas flow. In the present embodiment, the process gas is an external gas, but a desired gas may be ejected from above in fig. 3A by a gas supply means not shown, if necessary. For example, in the case of removing residues such as cutting oil adhering to a metal workpiece, a gas obtained by adding a slight amount of oxygen to nitrogen is desirable, but the type of gas is not limited in the present invention.

Since the metal workpiece holder 21 is applied with the ground potential and the workpiece 1 is in contact with the workpiece holder 21, the metal workpiece 1 is applied with the ground potential. On the other hand, a high frequency high voltage is applied to the electrode portion 3 by the high voltage power supply portion 4. The gap between the columnar portion 31 and the inner wall surface of the through-hole 1C is narrow, and discharge is generated between the columnar portion 31 and the inner wall surface under atmospheric pressure, thereby generating plasma in the space formed by the gap between the insulating material 15 and the inner wall surface. The plasma is generated in the entire axial direction and the entire circumferential direction of the space.

In this way, the inner wall surface of the through-hole 1C can be directly treated with the plasma generated inside the through-hole 1C. Here, when it is assumed that a through-hole is processed using the remote plasma processing apparatus as described in patent document 1, the ratio of active species generated by plasma directly escaping to the outside without touching the inner wall surface of the through-hole is high, and thus sufficient processing may not be performed. In particular, in the case of a through hole having a long depth, the more the active species are deactivated, the more the active species travel to the depth of the through hole, and thus sufficient treatment may not be performed. In this way, in the remote system, it is difficult to efficiently perform the plasma processing of the through hole of the workpiece, but in the present embodiment, the plasma processing can be efficiently performed because the inner wall surface of the through hole 1C is directly processed.

For example, when the through-hole 1C is formed in the workpiece 1, the cutting oil remaining on the inner wall surface of the through-hole 1C can be removed by the plasma treatment. This improves the wettability of the through-hole 1C and improves the adhesive strength when the member is fixed to the through-hole 1C with the adhesive. The plasma treatment of the through-hole is not limited to the above-described application of removing the residual cutting oil, and may be applied to, for example, introducing an appropriate material gas to form a thin film on the inner wall surface of the through-hole.

Further, by generating the gas flow, it is possible to suppress leakage of gas (for example, nitrogen oxide, ozone, or the like) generated by converting the processing gas into plasma inside the through-holes 1C to the outside gas side. In order to prevent the gas from leaking to the outside, the flow rate may be set to be substantially equal to or larger than 1 m/sec. Further, since the discharge gap is generally as narrow as 1mm or less, the flow path resistance when passing through the discharge gap becomes large, and therefore a negative pressure is likely to be generated in the internal space 2S. Therefore, a pressure difference can be formed with the outside air, and therefore the workpiece 1 is pressed against the workpiece holder 21 and held, and the positional displacement of the workpiece 1 can also be suppressed.

In particular, if the gap between the insulating material 15 and the through-hole 1C is narrowed, the cross-sectional area of the space formed by the gap can be reduced, and the flow velocity of the gas flow passing through the space can be increased even at the same flow rate. This can further suppress leakage of the predetermined gas to the outside air side. In this case, although the air flow is increased in speed, the workpiece 1 is pressed against the workpiece holder 21 as described above, and therefore, the positional displacement of the workpiece 1 is suppressed.

The portion of the columnar portion 31 facing the inner wall surface of the through-hole 1C is covered with the insulating material 15. This enables so-called dielectric barrier discharge to be performed, and discharge under atmospheric pressure can be stabilized even when the gap between the columnar portion 31 and the inner wall surface of the through-hole 1C is narrowed. Further, the flow velocity of the gas flow can be increased by narrowing the gap between the insulating material 15 and the inner wall surface of the through hole 1C. In addition, the insulating material 15 is not necessarily provided.

The electrode portion 3 penetrates through the through-hole 1C from the lower side of the through-hole 1C to the upper side of the through-hole 1C. That is, the electrode portion 3 protrudes outward from both opening ends of the through hole 1C. The inside of the through-hole 1C is the inside, and the outside of the through-hole 1C is the outside. This stabilizes the generation of plasma at both opening ends of the through-hole 1C.

The columnar portion 31 faces the inner wall surface of the through-hole 1C. That is, the outer peripheral surface of the portion of the electrode portion 3 facing the inner wall surface is circular when viewed in the axial direction. This makes it possible to make the gap between the circular inner wall surface of the through-hole 1C and the electrode portion 3 uniform in the circumferential direction when viewed in the axial direction. Therefore, the treatment of the inner wall surface of the through hole 1C can be made uniform.

Further, since the portion of the electrode portion 3 facing the inner wall surface of the through-hole 1C is constituted by the columnar portion 31, the electrode portion 3 can be easily formed even when the diameter of the through-hole 1C is small.

In a state where the ground potential is applied to the workpiece 1, a high voltage is applied to the electrode portion 3 by the high voltage power supply portion 4. This makes it possible to set the workpiece 1, which is located outside the electrode portion 3 and is easily touched by a person, to the ground potential, thereby improving safety. In order to generate plasma, a high voltage may be applied to the workpiece 1 side and a ground potential may be applied to the electrode portion 3 side.

Further, by providing the workpiece 1 in the workpiece holder 21, the workpiece 1 is positioned on a plane perpendicular to the axial direction with respect to the workpiece holder 21 by the contact outer peripheral surface 121 and the contact inner wall surface 211A. Since the positional relationship between the workpiece holder 21 and the electrode portion 3 is predetermined, the positional relationship between the workpiece 1 and the electrode portion 3 is also defined by the installation of the workpiece 1. This makes it easy to manage the gap between the through-hole 1C and the inner wall surface of the electrode portion 3. By controlling the gap, the plasma treatment of the inner wall surface of the through hole 1C can be made uniform. Further, the workpiece 1 can be attached to and detached from the workpiece holder 21 in the axial direction.

Further, since the flow meter 8 is disposed in the flow path between the exhaust port 221 and the ejector 6, the flow rate of the air flow flowing out from the exhaust port 221 to the outside can be measured. This makes it possible to detect an abnormality in the fixing state of the workpiece 1 and the workpiece holder 21 based on the pressure difference.

The CCD camera 9 is disposed above the electrode portion 3 and the workpiece 1, and the light emission state of the plasma generated between the insulating material 15 and the inner wall surface of the through hole 1C can be imaged by the CCD camera 9. This makes it possible to detect, for example, an abnormality in the plasma generation state.

< embodiment 2 >

Fig. 4 is a vertical sectional view showing the structure of the holding portion 2 and the electrode portion 301 according to embodiment 2 of the present invention. The structure of the present embodiment is different from that of embodiment 1 (fig. 3A) in the electrode portion 301.

The electrode portion 301 has a cylindrical portion 301A. The columnar portion 301A extends and is disposed from the lower side of the through hole 1C of the workpiece 1 to the middle of the through hole 1C in the axial direction. That is, the columnar portion 301A is opposed to the inner wall surface of the through-hole 1C in a part of the axial direction and the entire circumferential direction inside the through-hole 1C. In other words, the electrode portion 301 is opposed to a part of the inner wall surface of the through-hole 1C in the radial direction inside the through-hole 1C.

The insulating material 15 covers the outer peripheral surface of the cylindrical portion 301A, and is disposed to penetrate axially from the lower side of the through hole 1C to the upper side of the through hole 1C. That is, the insulating material 15C is opposed to the inner wall surface of the through-hole 1C in the entire axial direction and the entire circumferential direction inside the through-hole 1C.

Thus, by applying a high-frequency high voltage to the electrode portion 301, plasma is generated inside the through-hole 1C in the space S1 between the insulating material 15 and the inner wall surface of the through-hole 1C where the columnar portion 301A faces the inner wall surface. The space S1 is a part of the space formed by the gap between the insulating material 15 and the inner wall surface.

According to the present embodiment, a part of the inner wall surface of the through hole 1C can be directly and selectively treated by the plasma generated in the space S1. For example, when a member is fixed to the through-hole 1C with an adhesive, when an adhesive is used in a part of the through-hole 1C, the plasma treatment may be selectively performed only at a portion to which the adhesive is to be applied according to the present embodiment. This can suppress discharge power during plasma processing. In the present embodiment, other effects can be obtained as in embodiment 1.

< embodiment 3>

Fig. 5 is a vertical sectional view showing the structure of the holding portion 2 and the electrode portion 301 according to embodiment 3 of the present invention. The present embodiment is a modification of embodiment 2, and differs from embodiment 2 in the structure of an insulating material 151 covering the outer peripheral surface of a cylindrical portion 301A.

The insulating material 151 extends axially from the lower side of the through-hole 1C to a middle of the through-hole 1C in the axial direction. That is, the insulating material 151 is opposed to the inner wall surface of the through-hole 1C in a part of the axial direction and the entire circumferential direction inside the through-hole 1C.

Thereby, as in embodiment 2, plasma is generated in the through-hole 1C in the space S1 between the insulating material 151 and the inner wall surface of the through-hole 1C where the columnar portion 301A faces the inner wall surface.

According to the present embodiment, a part of the inner wall surface of the through-hole 1C can be directly treated by the plasma generated in the space S1, and the efficiency of the plasma treatment can be improved. In the present embodiment, other effects can be obtained as in embodiment 1.

< 4 th embodiment >

Fig. 6 is a plan view of the electrode portion 302 according to embodiment 4 of the present invention as viewed from above the workpiece 1. The electrode portion 302 has a cylindrical portion 302A and a protruding portion 302B.

The columnar portion 302A extends in the axial direction, and penetrates from the lower side of the through hole 1C of the workpiece 1 to the upper side of the through hole 1C. The columnar portion 302A may extend from the lower side of the through-hole 1C to the middle of the through-hole 1C in the axial direction.

The four protruding portions 302B protrude radially outward from the outer peripheral surface of the cylindrical portion 302A and are arranged at equal intervals in the circumferential direction. For example, the protruding portion 302B extends in the axial direction and is formed in the entire axial direction of the cylindrical portion 302A. Thus, the protruding portion 302B penetrates from the lower side of the through-hole 1C to the upper side of the through-hole 1C or is disposed from the lower side of the through-hole 1C to the middle of the through-hole 1C in the axial direction. In other words, the electrode portion 302 is opposed to a part of the inner wall surface of the through-hole 1C in the radial direction inside the through-hole 1C.

The insulating material 152 is disposed to cover the electrode portion 302. The insulating material 152 is cylindrical and extends in the axial direction. The inner peripheral surface of the insulating member 152 contacts the arc-shaped outer peripheral surface of the protrusion 302B. For example, the insulating material 152 is disposed in the entire axial direction of the protruding portion 302B. Thus, the insulating material 152 penetrates from the lower side of the through-hole 1C to the upper side of the through-hole 1C or is disposed from the lower side of the through-hole 1C to the middle of the axial direction of the through-hole 1C.

By applying a high-frequency high voltage to the electrode portion 302, plasma is generated inside the through-hole 1C in the space S2 between the insulating material 152 and the inner wall surface of the through-hole 1C where the protruding portion 302B faces the inner wall surface. When the protruding portion 302B penetrates from the lower side of the through hole 1C to the upper side of the through hole 1C, the space S2 is a part of the space formed by the gap between the insulating material 152 and the inner wall surface in the circumferential direction and the entire space in the axial direction. When the protruding portion 302B is disposed from the lower side of the through-hole 1C to the middle of the through-hole 1C in the axial direction, the space S2 is a part in the circumferential direction and a part in the axial direction of the space formed by the gap between the insulating material 152 and the inner wall surface.

According to the present embodiment, a part of the inner wall surface of the through-hole 1C can be directly treated by the plasma generated in the space S2, and the efficiency of the plasma treatment can be improved. In the present embodiment, other effects can be obtained as in embodiment 1.

< embodiment 5 >

Fig. 7 is a vertical sectional view showing the structure of the holding portion 2 and the electrode portion 303 according to embodiment 5 of the present invention. This embodiment is a modification of embodiment 1 (fig. 3A), and is different from embodiment 1 in the structure of the electrode portion 303 and the insulating material 153.

The insulating material 153 is cylindrical and extends in the axial direction, and penetrates from the lower side of the through hole 1C of the workpiece 1 to the upper side of the through hole 1C. The electrode portion 303 is formed as a metal film formed on the inner peripheral surface of the insulating material 153. The electrode portion 303 covers the entire circumferential direction and the entire axial direction of the inner circumferential surface of the insulating material 153. In other words, the electrode portion 303 is radially opposed to the entire inner wall surface of the through hole 1C in the workpiece 1.

With such a configuration, by applying a high-frequency high voltage to the electrode portion 303, plasma is generated inside the through-hole 1C in a space between the insulating material 153 where the electrode portion 303 faces the inner wall surface of the through-hole 1C and the inner wall surface. The inner wall surface of the through hole 1C can be directly treated by the generated plasma. In the present embodiment, it is not necessary to fill the electrode portion on the radially inner side with a metal as in embodiment 1.

The electrode portion 303 and the insulating material 153 may be disposed from the lower side of the through hole 1C to the middle of the through hole 1C in the axial direction. In this case, a part of the inner wall surface of the through hole 1C can be plasma-treated.

< embodiment 6 >

Fig. 8 is a vertical sectional view showing the structure of the holding portion 201 and the electrode portion 304 according to embodiment 6 of the present invention. The present embodiment is an embodiment in the case where a workpiece made of an insulating material is to be processed as described later.

The holding portion 201 has a work holder 23 and a housing 24. The work holder 23 is disposed above the housing 24. The work holder 23 has a metal portion 231 and a base portion 232.

The base portion 232 is fixed to the housing 24. The metal part 231 is fixed to the base part 232. The metal part 231 has a substantially cylindrical shape extending in the axial direction, and has an opening 231A penetrating in the axial direction. The base portion 232 is made of resin and has insulation properties. The base portion 232 has a substantially disk shape and has an opening portion 232A penetrating therethrough in the axial direction. The opening 232A is located below the opening 231A and communicates with the opening 231A.

The electrode portion 304 has a cylindrical shape extending in the axial direction, and penetrates from the lower side of the opening 232A to the upper side of the opening 231A. The insulating material 154 covers the entire outer peripheral surface of the electrode portion 304.

Fig. 9 shows a structure in which the workpiece 101 is held by the workpiece holder 23 in the structure shown in fig. 8. The work 101 is made of a resin material and has insulation properties. The workpiece 101 is cylindrical and extends in the axial direction, and has a through hole 101A penetrating in the axial direction. The workpiece 101 is held by the metal portion 231 so that the outer peripheral surface 101B of the workpiece 101 contacts the outer peripheral surface of the opening 231A.

Since the diameter of the opening 232A is smaller than the diameter of the opening 231A, the lower surface of the workpiece 101 can be placed on the upper surface of the base portion 232. The electrode portion 304 and the insulating material 154 penetrate the opening 232A and the through hole 101A. The electrode portion 304 is radially opposed to the entire inner wall surface of the through-hole 101A inside the through-hole 101A.

A semi-closed space is formed by the work 101 and the holding portion 201. The upper portion of the through hole 101A is the outside air side. The process gas is introduced into the through-hole 101A from the outside gas side under atmospheric pressure. The gas in the internal space 2S is discharged from the gas discharge port 241 of the casing 24, so that the internal space 2S becomes a negative pressure. This generates an air flow flowing from the outside air side to the internal space 2S through the through hole 101A and the opening 232A.

The metal part 231 is applied with a ground potential, and the electrode part 304 is applied with a high-frequency high voltage by the high-voltage power supply part 4. Thereby, dielectric barrier discharge is performed between the electrode portion 304 and the metal portion 231 by the insulating material 154 and the workpiece 101 as an insulating material. Therefore, plasma is generated in the space formed between the insulating material 154 and the inner wall surface of the through-hole 101A. The inner wall surface of the through hole 101A can be directly treated by the generated plasma. As described above, in the present embodiment, the plasma processing can be efficiently performed on the workpiece 101 as the insulating material.

Further, the flow velocity of the gas flow can be increased by narrowing the gap between the workpiece 101 and the electrode portion 304. This can suppress leakage of the predetermined gas generated by the plasma to the outside gas side. Even if the gas flow is increased, the workpiece 101 can be pressed and fixed against the base portion 232 by the pressure difference between the outside air and the negative pressure, and therefore, the positional displacement of the workpiece 101 is suppressed.

Further, since the base portion 232 is made of an insulating material, unnecessary discharge can be suppressed from occurring between the base portion 232 and the electrode portion 304.

In the present embodiment, the electrode portion 304 and the insulating material 154 may extend from the lower side of the through-hole 101A to an axial middle of the through-hole 101A. In this case, plasma processing can be performed on a part of the inner wall surface of the through hole 101A.

Further, the insulating material 154 is not essential, and even if the insulating material 154 is not provided, dielectric barrier discharge can be performed using the workpiece 101 as an insulating material.

< embodiment 7 >

Fig. 10 is a vertical sectional view showing the structure of the holding portion 202 and the electrode portion 3 according to embodiment 7 of the present invention. In the present embodiment, the workpiece 1 is held by the holding portion 202 in the vertical direction opposite to that of embodiment 1.

The holding portion 202 has a work holder 25 and a housing 22. The work holder 25 has an opening 251 that penetrates in the axial direction. The work holder 25 has a mounting surface 25A having an annular shape when viewed in the axial direction at the upper portion, and an annular protrusion 252 protruding upward from the radially inner edge of the mounting surface 25A. The outer peripheral surface of the annular protrusion 252 is a contact outer wall surface 25B extending in the axial direction.

Since the vertical direction of the workpiece 1 is opposite to that of embodiment 1, the recess 1B is located below the through hole 1C, and the recess 1A is located below the recess 1B. The inner peripheral surface of the recess 1B is the contact inner peripheral surface 113 of the workpiece 1. The workpiece 1 is placed on the placement surface 25A so that the contact outer wall surface 25B can contact the contact inner circumferential surface 113. Thereby, the workpiece 1 is prevented from moving on a plane perpendicular to the axial direction.

In a state where the workpiece 1 is held by the workpiece holder 25, the columnar portion 31 of the electrode portion 3 penetrates from the lower side of the through hole 1C of the workpiece 1 to the upper side of the through hole 1C. In other words, the electrode portion 3 is radially opposed to the entire inner wall surface of the through hole 1C in the workpiece 1. The insulating material 15 covers the entire outer peripheral surface of the cylindrical portion 31.

The upper side of the through hole 1C is the outside air side. The gas in the internal space 2S is discharged from the gas outlet 221 of the casing 22, and the internal space 2S becomes a negative pressure. This generates an air flow flowing from the outside air side to the internal space 2S through the through-hole 1C and the opening 251. The work holder 25 is made of metal, and a ground potential is applied thereto. Therefore, the workpiece 1 is applied with the ground potential via the workpiece holder 25. By applying a high-frequency high voltage to the electrode portion 3, discharge is generated in the gap between the columnar portion 31 and the inner wall surface of the through-hole 1C, and plasma is generated in the space between the insulating material 15 and the inner wall surface. The inner wall surface can be directly treated by the generated plasma. The workpiece 1 is pressed and fixed to the workpiece holder 25 by a pressure difference between the outside air and the negative pressure.

< 8 th embodiment >

In the embodiments described above, the object of plasma processing is a through hole, but in the present invention, the object of processing may be a bottomed hole that does not penetrate. Fig. 11 is a vertical cross-sectional view showing the structure of the holding portion 2 and the electrode portion 3 according to embodiment 8 of the present invention. In the present embodiment, the work 100 is held by the work holder 21.

The workpiece 100 has a bottomed hole 100A. The bottomed hole 100A is open at the lower side, and has a hole bottom 100A1 at the upper end and an inner wall surface 100A2 extending downward from the hole bottom 100A1 in the axial direction. That is, the bottomed hole 100A is a hole that does not penetrate therethrough. The tip of the columnar portion 31 of the electrode portion 3 and the tip of the insulating material 15 are disposed inside the bottomed hole 100A. A gap is provided between the upper end of the cylindrical portion 31 and the upper end of the insulating material 15 and the hole bottom 100a 1. The columnar portion 31 and the insulating material 15 are radially opposed to a part of the inner wall surface 100a 2.

By applying a ground potential to the workpiece 100 and applying a high-frequency high voltage to the electrode portion 3, plasma is generated in the gap between the insulating material 15 and the inner wall surface 100a2, and the inner wall surface 100a2 is treated with the generated plasma.

In this way, the plasma treatment can be efficiently performed on the inner wall surface of the bottomed hole 100A which is a hole that does not penetrate therethrough.

< effects of the present embodiment >

As described above, the plasma processing apparatus (10) of the present embodiment includes the electrode portion (3, etc.) and the holding portion (2, etc.) that holds the workpiece (1, etc.). The electrode portion is opposed to at least a part of an inner wall surface of a hole (1C, etc.) of the workpiece in a radial direction at least inside the hole.

According to such a configuration, by applying a predetermined voltage to the electrode portion, plasma can be generated between the workpiece and the electrode portion under atmospheric pressure. This enables the inner wall surface of the hole, which is in contact with the generated plasma, to be treated. This enables the inner wall surface of the hole to be treated at a higher speed than in the remote system.

The hole is a through hole (1C, etc.), and the electrode portion (3, etc.) protrudes outward from both open ends of the through hole. This stabilizes the generation of plasma at both opening ends of the through hole.

The outer peripheral surface of at least a portion of the electrode portion (3, etc.) facing the inner wall surface is circular when viewed in the axial direction. This makes it possible to make the gap between the electrode section and the inner wall surface of the circular hole uniform in the circumferential direction when viewed in the axial direction, and to make the treatment of the inner wall surface of the hole uniform.

The electrode portion (3, etc.) has a cylindrical portion (31, etc.), and at least a portion of the electrode portion facing the inner wall surface is included in the cylindrical portion. This makes it easy to mold the electrode portion even when the hole is small.

Further, an alternating voltage is applied to the electrode portion (3, etc.) in a state where a ground potential is applied to the workpiece (1, etc.). This makes it possible to set the workpiece side, which is located outside the electrode portion and is easily touched by a person, to the ground potential, thereby improving safety.

The holding portion (2, etc.) has a grounded metal portion (21, etc.), and the workpiece can be brought into contact with the metal portion. Thus, by providing the metal workpiece in the holding portion, the ground potential can be applied to the workpiece through the metal portion.

The holding portion (201) has a metal portion (231) that comes into contact with the outer peripheral surface of the workpiece (101) made of an insulating material when the workpiece is held. This enables dielectric barrier discharge to be performed between the workpiece made of an insulating material and the electrode portion.

The holding portion (201) has a base portion (232) that is positioned below the metal portion (231) and on which the workpiece (101) can be placed. The base portion is made of an insulating material and has an opening (232A), and the electrode portion (304) penetrates through the opening. This suppresses unnecessary discharge from occurring between the base portion and the electrode portion.

< suppression of gas leakage >

Conventionally, the following techniques have been widely used: the inside of the closed container is depressurized and plasma is generated, thereby performing plasma processing on the workpiece disposed in the closed container. However, in recent years, a technique for stably performing plasma discharge under atmospheric pressure has been established, and plasma treatment in an open space has been put to practical use. Thus, a strong closed container resistant to pressure reduction is not required, and a low-cost plasma processing apparatus is realized.

However, when the plasma processing is performed in an open-air system, a predetermined gas generated by the plasma discharge may leak into the external gas. For example, when plasma discharge is performed in a gas containing oxygen and nitrogen as main components, such as air, nitrogen oxides and ozone are generated, and there is a concern that these may leak into the outside air.

Therefore, for example, japanese patent application laid-open No. 2009-129997 discloses the following technique: a suction port is provided together with an ejection port for ejecting a process gas for performing plasma processing, and leakage of the process gas into an external gas is suppressed. In the japanese patent application laid-open No. 2009-129997, in order to further suppress the leakage of the process gas, a double-walled housing is formed as a semi-closed container having a narrow opening communicating with the outside air, and a suction duct is separately provided independently from the suction port, thereby completely preventing the leakage.

However, it is effective to use a double or triple leakage suppressing means for the process gas leakage as in the above-mentioned japanese patent application laid-open No. 2009-129997, but the apparatus structure becomes complicated, which becomes a factor of increasing the apparatus cost.

In view of the above, in another embodiment, a plasma processing apparatus is provided that can simplify a means for suppressing gas leakage generated by plasma.

A plasma processing apparatus (10) according to another embodiment includes: a holding section (2, etc.) for holding a workpiece (1, etc.); a plasma generation unit (3, 4, 16, etc.) that generates plasma; and an exhaust unit (6) that exhausts the gas in the internal space (2S) of the holding unit. The internal space communicates with an external gas via a through hole (1C, etc.) provided in the workpiece, and the plasma generating section generates plasma inside the through hole or on the external gas side.

According to this configuration, the gas in the internal space of the holding portion is discharged by the gas discharge portion, so that a negative pressure is generated in the internal space, and a gas flow is generated that flows from the outside air side to the internal space through the through hole. The through-hole is processed by plasma generated inside the through-hole or active species guided from the outside gas side to the through-hole by the negative pressure. By forming the gas flow, leakage of the gas generated by the plasma to the outside gas side can be suppressed, and the structure of the leakage suppressing means can be simplified. Further, the position of the workpiece can be suppressed from becoming unstable by the pressure difference between the outside air and the negative pressure.

The plasma generation unit has an electrode unit (3) or the like, and the electrode unit is opposed to at least a part of the inner wall surface of the through hole in the radial direction at least inside the through hole (1C or the like).

In this way, the inner wall surface of the through hole is directly treated by the plasma generated between the through hole and the electrode portion, and therefore, the treatment efficiency of the inner wall surface can be improved. Further, since the gap between the inner wall surface of the through hole and the electrode portion is narrow, the cross-sectional area of the space formed by the gap can be reduced, and the flow velocity of the gas flow passing through the space can be increased. Therefore, leakage of the gas generated by the plasma to the outside gas side is easily suppressed.

At least a portion of the electrode portion (3, etc.) facing the inner wall surface is covered with an insulating material (15, etc.).

This enables dielectric barrier discharge to be performed, and discharge under atmospheric pressure to be stabilized. Further, the gap between the insulating material and the inner wall surface of the through hole is narrowed, whereby the flow velocity of the air flow can be increased.

The electrode portion (3, etc.) protrudes outward from both open ends of the through-hole (1C, etc.). This stabilizes the generation of plasma at both opening ends of the through hole.

The outer peripheral surface of at least a portion of the electrode portion (3, etc.) facing the inner wall surface is circular when viewed in the axial direction. This makes it possible to make the gap between the through-hole having a circular shape when viewed in the axial direction and the electrode portion uniform in the circumferential direction, and to make the treatment of the inner wall surface of the through-hole uniform.

The electrode portion (3, etc.) has a cylindrical portion (31, etc.), and at least a portion of the electrode portion facing the inner wall surface is included in the cylindrical portion. This makes it easy to form the electrode portion even when the through hole is small.

Further, an alternating voltage is applied to the electrode portion (3, etc.) in a state where a ground potential is applied to the workpiece (1, etc.). This makes it possible to set the workpiece side, which is located outside the electrode portion and is easily touched by a person, to the ground potential, thereby improving safety.

The holding portion (2, etc.) has a grounded metal portion (21, etc.), and the work (1, etc.) can be brought into contact with the metal portion. Thus, by providing the metal workpiece in the holding portion, the ground potential can be applied to the workpiece through the metal portion.

The holding portion (201) has a metal portion (231) that comes into contact with the outer peripheral surface of the workpiece (101) made of an insulating material when the workpiece is held. This enables dielectric barrier discharge to be performed between the workpiece made of an insulating material and the electrode portion. Therefore, the gap between the workpiece and the electrode portion can be narrowed, and the flow velocity of the gas flow can be increased.

The holding portion (201) has a base portion (232) that is positioned below the metal portion (231) and on which the workpiece (101) can be placed, and the base portion has an opening (232A) that communicates with the through-hole (101A). As a result, the internal space of the holding portion is made negative pressure by the exhaust portion, and the workpiece is pressed against the base portion by the pressure difference between the outside air and the negative pressure, thereby fixing the workpiece.

The base portion (232) is made of an insulating material, and the electrode portion (304) penetrates the opening (232A). This suppresses unnecessary discharge from occurring between the base portion and the electrode portion.

The exhaust device further comprises a flow rate measuring unit (8) for measuring the flow rate of the gas discharged from the exhaust unit (6). Thus, it is possible to detect an abnormality in the fixed state of the workpiece and the holding portion from the state of the gas flow rate.

< implementation based on remote mode >

In the other embodiments described above, the electrode portion is disposed in the through hole of the workpiece, but here, an embodiment using a so-called remote system is described with reference to fig. 12.

In the configuration shown in fig. 12, the configuration of the workpiece 1 and the holding portion 2 is the same as that of embodiment 1 described above. However, in the plasma processing apparatus shown in fig. 12, the plasma generating section 16 is used. The plasma generation unit 16 is located above the through hole 1C of the workpiece 1 and on the outside air side.

The plasma generating unit 16 has at least a pair of electrodes, not shown, and the plasma generating unit 16 generates plasma by discharge between the electrodes under atmospheric pressure. That is, the plasma generating unit 16 generates plasma on the outside gas side. The gas in the internal space 2S is discharged through the gas outlet 221, and the internal space 2S becomes a negative pressure. This generates a gas flow flowing from the outside air side through the through hole 1C and the opening 211 into the internal space 2S, and introduces the active species blown out from the blow-out port 161 of the plasma generation portion 16 into the through hole 1C. Therefore, the inner wall surfaces of the through-holes 1C can be treated with the active species.

At this time, since a predetermined gas (for example, nitrogen oxide, ozone, or the like) based on the plasma generated by the plasma generating portion 16 is discharged from the internal space 2S to the outside through the through hole 1C, the predetermined gas can be suppressed from leaking to the outside gas side. Therefore, the gas leakage prevention means can be simplified.

Embodiment 9 and the following background

Conventionally, a technique of generating plasma under atmospheric pressure has been developed, and in recent years, processing using plasma has been performed on workpieces of various shapes.

For example, japanese patent application laid-open No. 2009-272165 discloses an example of a plasma processing apparatus that generates plasma at atmospheric pressure. The plasma processing apparatus has a cylindrical space as a discharge space. The internal pressure of the cylindrical space is atmospheric pressure. The process gas is introduced into the cylindrical space from a process gas supply source. When a voltage is applied from a power supply to the electrodes, a discharge is formed in the cylindrical space under atmospheric pressure. Thereby, the processing gas introduced into the cylindrical space is converted into plasma. The plasma-converted processing gas is blown out from the cylindrical space toward the workpiece and contacts the surface of the workpiece. Thereby, a desired surface treatment can be performed.

The plasma processing apparatus disclosed in japanese patent application laid-open No. 2009-272165 is a so-called remote system apparatus as follows: plasma is generated in a space away from the workpiece, and the plasma is transferred to the workpiece, thereby performing a desired process on the workpiece.

Here, generally, when a metal workpiece is drilled, cutting oil adheres to and remains on the inner wall surface of the hole. Although the residual cutting oil is removed by a cleaning liquid or the like, particularly when the hole diameter is small, a sufficient cleaning effect may not be obtained, and the cutting oil may remain. In this case, when the member is fixed to the cleaned hole with an adhesive, wettability may be reduced due to surface contamination by the cutting oil, and sufficient adhesive strength may not be obtained.

Therefore, it is expected that the surface contamination caused by the cutting oil is removed by the plasma treatment. However, when the remote plasma processing apparatus as described in japanese patent application laid-open No. 2009-272165 is used, there is a problem in introducing active species by plasma into the hole, and it is difficult to efficiently perform plasma processing of the hole of the workpiece.

In view of the above circumstances, it is an object of embodiment 9 and the following to provide a plasma processing apparatus capable of efficiently and uniformly performing plasma processing on a workpiece.

< embodiment 9 >

Fig. 13 is a vertical sectional view showing the structure of the holding portion 203 and the electrode portion 3 according to embodiment 9 of the present invention. This embodiment is a modification of embodiment 1.

The holding portion 203 has a work holder 26 and a housing 22. The work holder 26 has a1 st opening 261 and a2 nd opening 262. The 1 st opening 261 opens toward the lower side of the work holder 26 and extends in the axial direction. The 2 nd opening 262 is disposed above the 1 st opening 261, communicates with the 1 st opening 261, and opens toward the upper side of the work holder 26.

The work holder 26 has a contact inner wall surface 262A as an outer peripheral surface of the 2 nd opening portion 262. The contact inner wall surface 262A extends in the axial direction. The tapered surface 262B is continuously connected to the upper portion of the contact inner wall surface 262A and extends to the upper end surface of the work holder 26. The diameter of the tapered surface 262B decreases downward.

The work holder 26 has an annular mounting surface 263 when viewed in the axial direction at a boundary position between the 1 st opening 261 and the 2 nd opening 262. The workpiece 1 is held by the workpiece holder 26 by placing the circular ring surface 111 of the workpiece 1 on the placing surface 263. At this time, the contact inner wall surface 262A is arranged to be able to contact the contact outer peripheral surface 11A, which is the outer peripheral surface of the base body 11, in the workpiece 1, thereby preventing the workpiece 1 from moving on a plane perpendicular to the axial direction.

This makes it easy to manage the gap between the inner wall surface of the through hole 1C of the workpiece 1 and the electrode portion 3. Therefore, the inner wall surface of the through hole 1C can be uniformly treated by the plasma generated between the inner wall surface and the electrode portion 3.

When the workpiece 1 is set to the workpiece holder 26 from above the workpiece holder 26, the workpiece 1 is easily guided by the tapered surface 262B to a position where the contact inner wall surface 262A and the contact outer peripheral surface 11A can contact each other. If the tapered surface 262B is provided in advance, for example, when the workpiece 1 is set by a conveying device, the conveying device can select a low-cost device because the workpiece 1 can be guided even if the precision of the repeat position of the conveying device is not high.

As shown in fig. 13, the electrode body E is composed of the electrode portion 3 and the insulating material 15. When the axial length from the lower end of the contact outer peripheral surface 11A of the held workpiece 1 to the upper end of the tapered surface 262B is L1 and the axial length from the lower end of the held workpiece 1 to the upper end of the electrode body E is L2, L1> L2 are satisfied.

When the gap between the upper end of the tapered surface 262B and the contact outer peripheral surface 11A is G1 and the gap between the through-hole 1C and the electrode body E is G2, G1< G2 is satisfied.

By satisfying the above-described relationship, the workpiece 1 can be attached to and detached from the workpiece holder 26 without bringing the workpiece 1 into contact with the electrode body E.

Further, the formation unevenness of the through-holes 1C may be strictly considered. In this case, assuming that the circularity of the through hole 1C is γ, the relationship between G1 and G2 satisfies G1+ γ < G2. This allows the workpiece 1 to be attached to and detached from the workpiece holder 26 without bringing the workpiece 1 into contact with the electrode body E, taking into account the unevenness in formation of the through holes.

< 10 th embodiment >

Fig. 14 is a vertical sectional view showing the structure of the holding portion 204 and the electrode portion 3 according to embodiment 10 of the present invention. This embodiment is a modification of embodiment 1.

The holding portion 204 includes the work holder 27 and the housing 22. The work holder 27 has a1 st opening 271 and a2 nd opening 272. The 1 st opening 271 opens toward the lower side of the work holder 27 and extends in the axial direction. The 2 nd opening 272 is disposed above the 1 st opening 271, communicates with the 1 st opening 271, and opens toward the upper side of the work holder 27.

The work retainer 27 has a contact inner wall surface 272A as an inner peripheral surface of the 2 nd opening 272. The contact inner wall surface 272A extends to the upper end of the work holder 27 in the axial direction.

The work holder 27 has a mounting surface 273 having an annular shape when viewed in the axial direction at a boundary position between the 1 st opening 271 and the 2 nd opening 272. The workpiece 1 is inserted into the 2 nd opening 272 from above, and the circular ring surface 111 of the workpiece 1 is placed on the placing surface 273, whereby the workpiece 1 is held by the workpiece holder 27. At this time, the contact inner wall surface 272A is arranged to be able to contact the contact outer peripheral surface 13A, which is the outer peripheral surface of the flange portion 13, in the workpiece 1, thereby preventing the workpiece 1 from moving on a plane perpendicular to the axial direction.

This makes it easy to manage the gap between the inner wall surface of the through hole 1C of the workpiece 1 and the electrode portion 3. Therefore, the inner wall surface of the through hole 1C can be uniformly treated by the plasma generated between the inner wall surface and the electrode portion 3.

Further, as shown in fig. 14, when the axial length from the lower end of the held workpiece 1, which is in contact with the outer peripheral surface 13A, to the upper end of the contact inner wall surface 272A is set to L3 and the axial length from the lower end of the held workpiece 1 to the upper end of the electrode body E is set to L4, L3> L4 are satisfied.

When the gap between the contact inner wall surface 272A and the contact outer peripheral surface 13A is G3 and the gap between the through-hole 1C and the electrode body E is G4, G3< G4 is satisfied.

By satisfying the above-described relationship, the workpiece 1 can be attached to and detached from the workpiece holder 27 without bringing the workpiece 1 into contact with the electrode body E.

When the workpiece 1 is removed from the workpiece holder 27, for example, the workpiece 1 may be sucked and pulled upward by using a suction nozzle that sucks air, or the workpiece 1 may be held and pulled upward by using a jig while the jig is used to apply a force to the inner wall of the workpiece 1 in the radial direction outward.

< embodiment 11 >

In the above-described embodiment, the inner wall surface of the through hole of the workpiece is the workpiece surface facing the electrode portion in the radial direction, but in embodiment 11 to be described here, the workpiece surface is not the inner wall surface of the through hole. That is, in the present invention, the through hole is not essential in the workpiece.

Fig. 15 is a vertical sectional view showing the structure of the holding portion 28 and the electrode portion 305 according to embodiment 11 of the present invention. The holding portion 28 is a metal member that holds the workpiece 1, and is applied with a ground potential. The holding portion 28 has a recess 28A on the cylindrical upper end surface, and the outer peripheral surface of the recess 28A is a contact inner wall surface 281.

The electrode portion 305 is annular and extends in the axial direction, and is held by the electrode holding portion 29. The resin portion 291 included in the electrode holding portion 29 holds the electrode portion 305. The electrode unit holding unit 29 has an exhaust port 292 on a side surface.

The outer peripheral surface of the projection 12 of the workpiece 1 is a contact outer peripheral surface 121. The work 1 is held by the holding portion 28 by disposing the projection 12 inside the recess 28A. At this time, the workpiece surface 11A of the workpiece 1, which is the outer peripheral surface of the lower end portion of the base 11, is radially opposed to the inner peripheral surface of the electrode portion 305 with a gap therebetween inside the electrode portion 305. The contact inner wall surface 281 is configured to be able to contact the contact outer peripheral surface 121, thereby preventing the workpiece 1 from moving on a plane perpendicular to the axial direction.

When the gas in the internal space 2S of the electrode holding portion 29 is discharged from the gas discharge port 292, a negative pressure is generated in the internal space 2S, and a gas flow flowing from the outside to the internal space 2S through the gap is generated. The workpiece 1 is applied with a ground potential via the holding portion 28. By applying a high frequency high voltage to the electrode portion 305 by the high voltage power supply portion 4, plasma is generated in the gap, and plasma processing of the workpiece surface 11A can be performed.

Since the movement of the workpiece 1 is prevented as described above, the gap is managed, and the plasma processing can be performed uniformly on the workpiece surface 11A.

< embodiment 12 >

In the present invention, the workpiece surface may be provided not only in the through hole but also in a hole that is not penetrated. Fig. 16 is a vertical sectional view showing the structure of the holding portion 2 and the electrode portion 3 according to embodiment 12 of the present invention. In the present embodiment, the work 100 is held by the work holder 21.

The workpiece 100 has a bottomed hole 100A. The bottomed hole 100A is open at the lower side, and has a hole bottom 100A1 at the upper end and an inner wall surface 100A2 extending downward from the hole bottom 100A1 in the axial direction. That is, the bottomed hole 100A is a hole that does not penetrate therethrough. The tip of the columnar portion 31 of the electrode portion 3 and the tip of the insulating material 15 are disposed inside the bottomed hole 100A. A gap is provided between the upper end of the cylindrical portion 31 and the upper end of the insulating material 15 and the hole bottom 100a 1. The columnar portion 31 and the insulating member 15 are radially opposed to a workpiece surface that is a part of the inner wall surface 100a 2.

By applying a ground potential to the workpiece 100 and applying a high-frequency high voltage to the electrode portion 3, plasma is generated in the gap between the insulating material 15 and the inner wall surface 100a2, and the workpiece surface is processed by the generated plasma.

In this way, the plasma processing can be efficiently performed on the surface of the workpiece having the bottomed hole 100A as a hole which does not penetrate therethrough. Further, since the contact inner wall surface 211A is disposed so as to be able to contact the contact outer peripheral surface 121, and the workpiece 100 is prevented from moving on a plane perpendicular to the axial direction, the gap between the workpiece surface of the bottomed hole 100A and the electrode portion 3 is controlled, and the processing of the workpiece surface can be made uniform.

In the 9 th and 10 th embodiments (fig. 13 and 14), the workpiece 100 may be used as the workpiece. That is, in embodiments 9 and 10, the workpiece may have a hole that does not penetrate therethrough.

< effects of the present embodiment >

As described above, the plasma processing apparatus (10) of the present embodiment includes the electrode portion (3, etc.) extending in the axial direction and the holding portion (2, etc.) holding the workpiece (1, etc.). The electrode portion is opposed to a workpiece surface of the workpiece in a radial direction, and the holding portion has a contact wall surface (211A, etc.) extending in an axial direction, and the contact wall surface is arranged so as to be capable of contacting a contact peripheral surface (121, etc.) of the workpiece, thereby preventing the workpiece from moving in a plane perpendicular to the axial direction.

According to this configuration, by providing the workpiece in the holding portion, the workpiece is positioned on the plane perpendicular to the axial direction with respect to the holding portion by the contact circumferential surface and the contact wall surface. Thus, once the positional relationship between the holding portion and the electrode portion is determined, the positional relationship between the workpiece and the electrode portion is also defined. Therefore, the gap between the workpiece surface and the electrode portion is easily managed. Further, since plasma can be generated between the workpiece surface and the electrode portion, the workpiece surface is directly processed by the generated plasma, and the processing speed is increased. By controlling the gap as described above, the treatment of the workpiece surface by the plasma can be made uniform.

The electrode unit (3, etc.) is arranged so as to be radially opposed to the workpiece surface, which is at least a part of the inner wall surface of a hole (1C, etc.) extending in the axial direction of the workpiece (1, etc.), at least in the interior of the hole.

This makes it easy to control the gap between the inner wall surface of the hole and the electrode portion, and makes it possible to uniformize the plasma treatment of the inner wall surface by the plasma generated between the inner wall surface and the electrode portion.

The contact wall surface (262A) is an inner wall surface, the contact circumferential surface (11A) is an outer circumferential surface, and the holding portion (203) has a tapered surface (262B) that is continuously connected to the upper portion of the contact inner wall surface and extends to the end surface of the holding portion, and the diameter of the tapered surface decreases downward.

Thus, the workpiece can be easily guided to the position where the contact circumferential surface and the contact wall surface can be brought into contact with each other by the tapered surface.

Further, the following expressions (1) and (2) are satisfied.

L1>L2 (1)

Wherein, L1: axial length from the lower end of the contact peripheral surface of the held workpiece (1) to the upper end of the tapered surface (262B), L2: the axial length from the lower end of the held workpiece to the upper end of the electrode body (E) including the electrode section (3).

G1<G2 (2)

Wherein, G1: gap between the upper end of the tapered surface and the contact circumferential surface, G2: and a gap between the hole (1C) and the electrode body.

This allows the workpiece to be attached to and detached from the holding portion without bringing the workpiece into contact with the electrode body.

Alternatively, the following formulas (1) and (3) may be satisfied.

L1>L2 (1)

Wherein, L1: axial length from the lower end of the contact peripheral surface of the held workpiece (1) to the upper end of the tapered surface (262B), L2: the axial length from the lower end of the held workpiece to the upper end of the electrode body (E) including the electrode section (3).

G1+γ<G2 (3)

Wherein, G1: gap between the upper end of the tapered surface and the contact circumferential surface, G2: a gap between the hole (1C) and the electrode body, γ: the roundness of the hole.

Thus, the workpiece can be attached to and detached from the holding portion without contacting the electrode body, taking into account the uneven formation of the holes.

The contact wall surface (272A) is an inner wall surface extending to the upper end of the holding portion (204), and the contact circumferential surface (13A) is an outer circumferential surface, and satisfies the following expressions (4) and (5).

L3>L4 (4)

Wherein, L3: axial length from the lower end of the contact peripheral surface to the upper end of the contact wall surface of the held workpiece (1), L4: the axial length from the lower end of the held workpiece to the upper end of the electrode body (E) including the electrode section (3).

G3<G4 (5)

Wherein, G3: gap between the contact wall surface and the contact circumferential surface, G4: a gap between the hole (1C) and the electrode body,

this allows the workpiece to be attached to and detached from the holding portion without bringing the workpiece into contact with the electrode body.

Further, the gas discharge device is provided with a gas discharge unit (6) for discharging gas in an internal space (2S, etc.) of the holding unit (2, etc.), and the internal space communicates with the outside air via the hole (1C).

As a result, the internal space of the holding portion becomes a negative pressure due to the exhaust of the exhaust portion, and a gas flow is generated from the outside air side through the hole to the internal space. Leakage of the gas generated by the plasma to the outside gas side can be suppressed by the gas flow. At this time, since the workpiece is fixed to the holding portion by the pressure difference between the outside air and the negative pressure, the positional deviation of the workpiece can be suppressed.

< others >

While the embodiments of the present invention have been described above, the embodiments can be variously modified within the scope of the present invention.

The present invention can be used, for example, for plasma treatment of cutting oil adhering to a through hole of a workpiece.

Claims (6)

1. A plasma processing apparatus, comprising:

a holding portion that holds a workpiece; and

an electrode portion having a cylindrical portion at an upper portion thereof,

the plasma processing apparatus is characterized in that,

the holding part is provided with an opening part,

the electrode portion is positioned with respect to the holding portion,

the electrode unit is opposed to at least a part of an inner wall surface of a hole of the workpiece in a radial direction at least inside the hole,

at least a portion of the electrode portion facing the inner wall surface is included in the columnar portion,

the cylindrical portion penetrates from the lower side to the upper side of the opening portion,

the contact inner wall surface of the opening portion extending in the axial direction is arranged to be capable of contacting a contact outer circumferential surface of the workpiece.

2. The plasma processing apparatus according to claim 1,

the holes are through-holes which are,

the electrode portion protrudes outward from both opening ends of the through hole.

3. The plasma processing apparatus according to claim 1 or 2,

an alternating voltage is applied to the electrode portion in a state where a ground potential is applied to the workpiece.

4. The plasma processing apparatus according to claim 1 or 2,

the holding portion has a metal portion that is grounded,

the workpiece is contactable with the metal portion.

5. The plasma processing apparatus according to claim 1 or 2,

the holding portion has a metal portion that comes into contact with an outer peripheral surface of the workpiece when holding the workpiece made of an insulating material.

6. The plasma processing apparatus according to claim 5,

the holding part has a base part which is positioned below the metal part and on which the workpiece can be placed,

the base part is made of an insulating material and has an opening,

the electrode portion penetrates through the opening of the base portion.

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