JP7042142B2 - Plasma generator - Google Patents

Description

The present invention relates to an inductively coupled plasma generator.

In the semiconductor manufacturing process, a film forming process and an etching process of a semiconductor wafer using plasma are performed. Patent Document 1 discloses an inductively coupled plasma (ICP) type plasma generator. In the plasma generator, a metal plate called a Faraday shield is inserted between the antenna coil and the vacuum tube in order to weaken the degree of electrostatic coupling between the antenna coil and the plasma.

Special Table 2002-537648

However, when a metal plate is inserted between the antenna coil and the vacuum tube, the antenna coil and plasma are separated by the thickness of the metal plate compared to the case where the antenna coil is wound around the outer circumference of the vacuum tube so as to come into contact with the vacuum tube. As the distance between the two increases, the degree of inductive coupling weakens and the power factor decreases. In order to compensate for this decrease, it is necessary to increase the output of the high frequency power supply that supplies voltage and current to the antenna coil. That is, there is a problem that the power loss becomes large. The thickness of the metal plate is generally about several mm. Further, when a refrigerant flow path through which the refrigerant flows is provided inside the metal plate to cool the vacuum tube, the thickness of the metal plate is about 10 mm even if it is thin.

Here, the above simulation of inductive coupling is performed, and the distance D between the antenna coil and the outer peripheral surface of the vacuum tube and the degree of inductive coupling R [%] when the degree of inductive coupling at a distance D = 0 mm is 100%. I investigated the relationship.
As a result, as shown in Table 1, when the distance D = 10 mm between the antenna coil and the outer peripheral surface of the vacuum tube (corresponding to the case where the thickness of the metal plate is 10 mm), the degree of inductive coupling R = about 53%. Therefore, it was found that the degree of inductive coupling was reduced by about 47%.
Further, when the distance D between the antenna coil and the outer peripheral surface of the vacuum tube is D = 1 mm (corresponding to the case where the thickness of the metal plate is 1 mm), the degree of inductive coupling R = about 90%, so that the degree of inductive coupling is high. It was found to decrease by about 10%.
As described above, when a metal plate is inserted between the antenna coil and the vacuum tube to form a Faraday shield, it has been found that the degree of inductive coupling is greatly reduced, which in turn causes a large power loss.

The above simulation was performed under the following conditions.
・ Vacuum tube shape: Cylindrical shape ・ Vacuum tube material: Non-conductive material such as quartz and alumina ・ Vacuum tube inner diameter: Approximately 76 mm
・ Outer diameter of vacuum tube: Approximately 80 mm
・ Thickness of vacuum tube: Approximately 2 mm
-Length of vacuum tube: Approximately 310 mm
・ Antenna coil material: Copper ・ Antenna coil: 10 mm square edgewise ・ Antenna coil inner diameter: Dimensions separated from the outer peripheral surface of the vacuum tube by a distance D (0 to 10 mm) ・ Frequency of current flowing through the antenna coil: 1 MHz

An object of the present invention is to provide a plasma generator capable of maximizing the degree of inductively coupled between an antenna coil and plasma while suppressing the degree of electrostatic coupling between the antenna coil and plasma.

The plasma generator according to the present invention is a plasma generator including a vacuum tube into which a material gas flows and an antenna coil wound around the outer periphery of the vacuum tube to generate plasma of the material gas in the vacuum tube. The plasma shield film made of a conductive material formed on the outer peripheral surface of the vacuum tube is provided.

In the present invention, the plasma generator has a Faraday shield film formed on the outer peripheral surface of the vacuum tube. Since the Faraday shield film is a thin film, the antenna coil can be arranged closer to the vacuum tube, and the degree of inductive coupling between the antenna coil and the plasma can be improved.

In the plasma generator according to the present invention, the Faraday shield film is formed by spraying or plating a conductive material.

In the present invention, a Faraday shield film is formed on the outer peripheral surface of the vacuum tube by thermal spraying of a conductive material. Therefore, the thickness of the film can be adjusted (for example, the thickness of the film can be adjusted on the order of 10 μm).

In the plasma generator according to the present invention, the thickness of the Faraday shield film is 10 μm or more and less than 300 μm.

In the present invention, since the Faraday shield film is 10 μm or more and less than 300 μm, the antenna coil can be arranged in the vicinity of the vacuum tube, and the degree of inductive coupling between the antenna coil and the plasma can be improved.

The plasma generator according to the present invention includes a plurality of the Faraday shield films, each Faraday shield film is long in the axial direction of the vacuum tube and is separated from each other in the circumferential direction, and some of the Faraday shield films have a reference potential. It is connected.

In the present invention, a plurality of strip-shaped Faraday shield films extending in the longitudinal direction of the vacuum tube are formed at intervals in the circumferential direction of the vacuum tube. Therefore, the eddy current induced by the magnetic field formed by the antenna coil can be prevented from flowing in the circumferential direction of the vacuum tube. In addition, the degree of electrostatic coupling between the antenna coil and the plasma can be weakened as a whole.
Further, since the configuration is such that not all of the plurality of Faraday shield films are connected to the reference potential, but some of the Faraday shield films are connected to the reference potential, the degree of electrostatic coupling can be adjusted.

The plasma generator according to the present invention includes a switch for opening and closing the ground wire connecting the Faraday shield film and the reference potential.

In the present invention, since the switch for opening and closing the ground wire connecting the Faraday shield film and the reference potential is provided, the presence or absence of the connection to the reference potential of the Faraday shield film can be switched to determine the degree of electrostatic coupling. Can be adjusted.

The plasma generator according to the present invention includes an insulating film that covers the Faraday shield film.

In the present invention, since the insulating film covering the Faraday shield film is provided, the discharge between the antenna coil and the Faraday shield can be suppressed, and the antenna coil can be arranged closer to the vacuum tube. It is also possible to bring the antenna coil into contact with the outer peripheral surface of the vacuum tube and wind it around the vacuum tube. Therefore, the degree of inductively coupled between the antenna coil and the plasma can be improved.

In the plasma generator according to the present invention, the insulating film is formed by spraying a non-conductive material.

In the present invention, an insulating film is formed on the outer peripheral surface of the vacuum tube by thermal spraying of a non-conductive material. Therefore, an insulating film on the order of 10 μm can be formed on the outer peripheral surface of the vacuum tube.

In the plasma generator according to the present invention, the total thickness of the Faraday shield film and the insulating film is less than 300 μm.

In the present invention, the Faraday shield film and the insulating film can be formed by thermal spraying and can be formed thinner than the conventional one, so that the thickness can be made less than 300 μm. Therefore, the degree of decrease in inductive coupling can be significantly reduced.

In the plasma generator according to the present invention, the antenna coil is in contact with the insulating film.

In the present invention, the antenna coil is in contact with the insulating film. Therefore, the distance between the antenna coil and the vacuum tube is the shortest, and the degree of inductive coupling between the antenna coil and the plasma can be maximized.

In the plasma generator according to the present invention, the antenna coil is in thermal contact with the insulating film, and the antenna coil has a refrigerant flow path through which the refrigerant flows.

In the present invention, the antenna coil having the refrigerant flow path is in thermal contact with the insulating film. Therefore, the vacuum tube can be cooled by passing the refrigerant through the antenna coil.

In the plasma generator according to the present invention, the antenna coil is an edgewise coil having a square cross section, and is in direct or indirect surface contact with the insulating film.

In the present invention, the antenna coil is an edgewise coil and is in direct or indirect surface contact with the insulating film. Therefore, the vacuum tube can be cooled more efficiently.

In the plasma generator according to the present invention, the insulating film covers the entire circumference of the vacuum tube in the circumferential direction.

In the present invention, the insulating film covers the entire circumference of the vacuum tube in the circumferential direction. Therefore, the outer peripheral surface of the vacuum tube can be uniformly leveled as compared with the case where the insulating film is formed only on the Faraday shield film portion. Therefore, the contact area between the antenna coil and the vacuum tube can be increased, and the cooling performance can be improved.

The plasma generator according to the present invention includes a heat radiating member which is arranged in the gap of the antenna coil in the axial direction of the vacuum tube and dissipates heat from the antenna coil or the vacuum tube.

In the present invention, the heat radiating member is arranged in the gap of the conducting wire portion constituting the antenna coil. Therefore, the heat of the vacuum tube is released through the antenna coil and the heat dissipation member. Therefore, the vacuum tube can be cooled more efficiently.

In the plasma generator according to the present invention, the heat radiating member is an elastic silicon resin.

In the present invention, since the heat radiating member has elasticity, it is possible to cope with the thermal expansion of the antenna coil. Further, since the heat radiating member is made of silicon resin, it is possible to secure the insulating property and the required thermal conductivity.

The plasma generator according to the present invention has an intermediate layer between the Faraday shield film and the insulating film.

In the present invention, the bondability between the Faraday shield film and the insulating film can be improved by providing the intermediate layer. The intermediate layer is a material having intermediate physical properties between the Faraday shield film and the insulating film.

The plasma generator according to the present invention has an intermediate layer between the vacuum tube and the Faraday shield film.

In the present invention, the bondability between the vacuum tube and the Faraday shield film can be improved by providing the intermediate layer. The intermediate layer is a material having intermediate physical properties between the vacuum tube and the Faraday shield film.

According to the present invention, it is possible to maximize the degree of inductively coupled between the antenna coil and plasma while suppressing the degree of electrostatic coupling between the antenna coil and plasma.
Note that maximizing inductive coupling does not necessarily mean the degree of maximum inductive coupling that can be ideally realized and the degree of maximum inductive coupling that can be achieved in simulation. Nor does it necessarily mean the maximum degree of inductive coupling designed or feasible in prototypes and actual products. The effect of the above invention is not intended to exclude from the present invention a plasma generator in which the degree of inductive coupling is not maximized due to cost, product design, balance with other functions, and various other reasons.
It is sufficient that the present invention has the effect of suppressing the degree of electrostatic coupling between the antenna coil and plasma without reducing the degree of inductively coupled between the antenna coil and plasma as much as possible.

It is a block diagram which shows the structural example of the plasma generator which concerns on this Embodiment 1. It is a perspective view which shows the structural example of a vacuum tube and an antenna coil. It is a perspective view which shows the structural example of the Faraday shield film. It is a side sectional view which shows the structural example of a vacuum tube and an antenna coil. It is a shaft sectional view which shows the structural example of a vacuum tube and an antenna coil. It is a conceptual diagram which shows the flattening processing method of a Faraday shield film and an insulating film. It is a perspective view which shows the structural example of the vacuum tube and the antenna coil which concerns on Embodiment 2. FIG. It is a perspective view which shows the other structural example of the vacuum tube and the antenna coil which concerns on Embodiment 2. FIG.

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments thereof.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration example of a plasma generator according to the first embodiment. The plasma generator according to the first embodiment is an ICP type plasma generator. The plasma generator includes an antenna coil 2 for generating plasma in the vacuum tube 1, a high frequency power supply 3 for applying a high frequency voltage to the antenna coil 2, and an impedance matching circuit 4 provided between the antenna coil 2 and the high frequency power supply 3. And.
In such a plasma generator, the high frequency voltage and high frequency current output from the high frequency power supply 3 are supplied to the antenna coil 2 via the impedance matching circuit 4, so that the high frequency current flows through the antenna coil 2. On the other hand, the material gas is supplied into the vacuum tube 1 as described later. As a result, the material gas is turned into plasma by inductively coupled by the high frequency current flowing through the antenna coil 2, and plasma is generated. Various processes (etching, etc.) are performed using this plasma.
The frequency of the high frequency voltage output from the high frequency power supply 3 is about 1 to 3 MHz. However, the frequency is not limited to this, and any frequency other than those shown above may be used as long as the frequency is suitable for generating plasma.

FIG. 2 is a perspective view showing a configuration example of the vacuum tube 1 and the antenna coil 2, FIG. 3 is a perspective view showing a configuration example of the Faraday shield film 5, and FIG. 4 is a side sectional view showing a configuration example of the vacuum tube 1 and the antenna coil 2. FIG. 5 is a cross-sectional view of a shaft showing a configuration example of the vacuum tube 1 and the antenna coil 2. The vacuum tube 1 has a tubular shape having an inflow port 1a into which the material gas flows in and an outflow port 1b from which the plasmatized gas flows out on both ends (see FIG. 1). The vacuum tube 1 is made of a non-conductive material such as quartz or alumina. The inner and outer diameters of the vacuum tube 1 are, for example, about 76 mm and about 80 mm, and the thickness is about 2 mm. The length of the vacuum tube 1 in the longitudinal direction is, for example, about 310 mm.

As shown in FIG. 3, a Faraday shield film 5 made of a conductive material is formed on the outer peripheral surface of the vacuum tube 1. The Faraday shield film 5 is formed by spraying a conductive material such as copper onto the outer peripheral surface of the vacuum tube 1. The thickness of the Faraday shield film 5 is, for example, about 10 μm or more and less than 300 μm, preferably about 10 μm or more and less than 100 μm. The range of the film thickness is 10 μm, 100 μm, and 300 μm as reference values, and tolerances are allowed. For example, the range of about 10 μm or more and less than 300 μm includes a Faraday shield film 5 thinner than 10 μm and a Faraday shield film 5 thicker than 300 μm within the tolerance range. Further, the range of about 10 μm or more and less than 100 μm includes a Faraday shield film 5 thinner than 10 μm and a Faraday shield film 5 thicker than 100 μm within the tolerance range.
Further, the thickness of the Faraday shield film 5 can be adjusted on the order of 10 μm.

If the thickness of the Faraday shield film 5 is about 10 μm, it is possible to suppress the degree of electrostatic coupling between the antenna coil 2 and the plasma.
Further, as the thickness of the Faraday shield film 5 increases, the degree of inductively coupled between the antenna coil 2 and the plasma decreases, and when the thickness of the Faraday shield film 5 becomes about 100 μm or more, the degree of inductively coupled decreases. start. However, if the thickness of the Faraday shield membrane 5 is up to about 100 μm, the degree of decrease in inductive coupling is at a level at which there is almost no need to worry.

On the other hand, when the thickness of the Faraday shield film 5 is about 300 μm, it becomes difficult to form a film by thermal spraying. Even if the thickness is about 300 μm, it is effective because the Faraday shield can be made thinner than before, but it is difficult to manufacture and the yield is poor. Therefore, the upper limit is about 300 μm. If the thickness is about 100 μm, it is easy to form a film by thermal spraying.

Here, referring to Table 1, when the distance between the antenna coil 2 and the outer peripheral surface of the vacuum tube 1 is 300 μm (when the thickness of the Faraday shield film 5 is 300 μm, the antenna coil 2 and the antenna coil 2 in the place where the Faraday shield film 5 is not present. The degree of inductive coupling is reduced by only about 3% on the outer peripheral surface of the vacuum tube 1).
Similarly, referring to Table 1, when the distance between the antenna coil 2 and the outer peripheral surface of the vacuum tube 1 is 100 μm (when the thickness of the Faraday shield film 5 is 100 μm, the antenna coil 2 and the antenna coil 2 in the place where the Faraday shield film 5 is not present. The degree of inductive coupling is reduced by only about 0.7% on the outer peripheral surface of the vacuum tube 1).
As a matter of course, when the distance between the antenna coil and the outer peripheral surface of the vacuum tube is less than 100 μm, the degree of decrease in inductive coupling is further reduced.

The Faraday shield film 5 has a long strip in the axial direction of the vacuum tube 1, and a plurality of the Faraday shield films 5 are formed. For example, five Faraday shield films 5 are formed, and the Faraday shield films 5 are separated from each other in the circumferential direction. The number of Faraday shield films 5 is an example and is not particularly limited. The length of the Faraday shield film 5 in the longitudinal direction is wider than the length of the antenna coil 2 wound around the vacuum tube 1 in the longitudinal direction.

Further, the Faraday shield film 5 formed on the vacuum tube 1 is covered with the insulating film 6 as shown in FIG. The insulating film 6 is formed by spraying a non-conductive material such as ceramic or alumina (aluminum oxide) onto the outer peripheral surface of the vacuum tube 1. If the insulating film 6 has a thickness of about 10 μm, it is possible to suppress the discharge of the antenna coil 2 and the Faraday shield film 5.
For example, the volume resistivity of alumina at 20 ° C is more than 10 ¹⁴ [Ω · cm], so when a thin film of alumina with a thickness of 10 μm is formed into a 20 cm × 10 cm square, the resistance value is about 500 [MΩ]. It can be seen that it has a sufficient function as an insulating material.

On the other hand, when the thickness of the insulating film 6 is about 300 μm, it becomes difficult to form a film by thermal spraying. Therefore, the upper limit is about 300 μm. If the thickness is about 100 μm, it is easy to form a film by thermal spraying.
The range of the film thickness of the insulating film 6 is 100 μm and 300 μm as reference values, and tolerances are allowed. For example, about 100 μm includes an insulating film 6 thinner or thicker than 100 μm within the tolerance range. Further, the film thickness of about 300 μm includes the insulating film 6 thinner or thicker than 300 μm within the tolerance range.

As described above, the Faraday shield film 5 and the insulating film 6 can each be formed up to a thickness of about 300 μm, but as the thickness of the film increases, the distance between the antenna coil and the outer peripheral surface of the vacuum tube increases. As a result, the degree of inductive coupling decreases.
Therefore, the upper limit of the thickness of the Faraday shield film 5 and the insulating film 6 may be set so that the total thickness of the films is, for example, less than 300 μm. Preferably, the total thickness of each film is set to be less than 200 μm.

Under the simulation conditions shown in Table 1, if the total thickness of each membrane is 300 μm, the degree of decrease in inductive coupling can be suppressed to about 3%. Further, when the total thickness of each film is 100 μm, the degree of decrease in inductively coupled can be suppressed to about 0.7%.

The Faraday shield film 5 may be formed not only by thermal spraying but also on the outer peripheral surface of the vacuum tube 1 by plating or the like. Also in the case of plating, a conductive material such as copper is used. In the case of plating, a Faraday shield film 5 having a thickness of 10 μm or more and 100 μm or less can be formed. Further, in the case of plating, the same effect as thermal spraying can be obtained. The above 10 μm indicates a reference value for the film thickness, and the Faraday shield film 5 thinner than 10 μm within the tolerance range is also included in the first embodiment. Similarly, 100 μm indicates a reference value for the film thickness, and the Faraday shield film 5 thicker than 100 μm within the tolerance range is also included in the first embodiment.
Further, the thickness of the Faraday shield film 5 can be adjusted on the order of 10 μm.

The insulating film 6 covers the entire circumference of the vacuum tube 1 in the circumferential direction, and the length in the longitudinal direction is longer than the length in the longitudinal direction of the Faraday shield film 5, and covers the entire Faraday shield. Further, at least a part of the insulating film 6 formed between the two Faraday shield films 5 in the circumferential direction of the vacuum tube 1 is in contact with the antenna coil 2. As will be described later, a refrigerant flows inside the antenna coil 2, and by improving the contact property between the insulating film 6 and the antenna coil 2, the heat of the vacuum tube 1 can be radiated more efficiently. The insulating film 6 may be formed so as to cover the entire axial direction of the vacuum tube 1.

Further, it is desirable that the axial cross section when the Faraday shield film 5 and the insulating film 6 are formed on the outer peripheral surface of the vacuum tube 1 is as perfect as possible, but the insulating film 6 is formed after the Faraday shield film 5 is formed. Therefore, unevenness may occur.

FIG. 6 is a conceptual diagram showing a method for flattening the Faraday shield film 5 and the insulating film 6. Note that FIG. 6 is an image diagram in which a part of the shaft cross section is enlarged and the outer peripheral surface of the vacuum tube 1 is linearly represented.

FIG. 6A shows the ideal state of the Faraday shield film 5 and the insulating film 6. As shown in FIG. 6A, it is ideal that the surfaces of the formed Faraday shield film 5 and the insulating film 6 have almost no unevenness.
However, as shown in FIG. 6B, when the degree of unevenness on the surface of the insulating film 6 is large, it is preferable to perform the flattening treatment shown in FIGS. 6C to 6E.

FIG. 6C shows a state in which a flattening treatment is performed to reduce the degree of unevenness by polishing the surface of the insulating film 6 from the state shown in FIG. 6B. In this case, since the thickness of the insulating film 6 is reduced by polishing, it is preferable to form the insulating film 6 thicker in anticipation of polishing.

FIG. 6D shows a state in which a second insulating film 6a is further formed in the concave portion so that the degree of unevenness is reduced from the state shown in FIG. 6B. Since the unevenness is considered to have a thickness close to the thickness of the Faraday shield film 5, the thickness of the insulating film 6 to be further formed may be based on the thickness of the Faraday shield film 5.

FIG. 6E shows a state in which a flattening treatment is performed to reduce the degree of unevenness by polishing the surface of the insulating film 6 from the state shown in FIG. 6D. The surface of the insulating film 6 shown in FIG. 6D can be further flattened. The process of FIG. 6E is not essential, but such process may be performed.

The antenna coil 2 is wound from the outer peripheral side of the vacuum tube 1, the inflow port 1a side to the outflow port 1b side. The antenna coil 2 is an edgewise coil made of a conductive material such as copper, and as shown in FIG. 3, the cross section of the conducting wire constituting the antenna coil 2 is rectangular. A refrigerant flow path 2a through which the refrigerant flows is formed inside the conducting wire constituting the antenna coil 2, and the refrigerant is configured to flow from one end to the other end of the antenna coil 2.
The conducting wire constituting the antenna coil 2 is in thermal contact with the insulating film 6. More specifically, the conductor is in surface contact with the insulating film 6. The antenna coil 2 may be in direct contact with the insulating film 6 or may be in contact with the insulating film 6 via a heat conductive material. The heat conductive material is a non-conductive material, and preferably has elasticity.

Further, a heat radiating member 7 that dissipates heat from the antenna coil 2 or the vacuum tube 1 is provided in the gap of the conducting wire portion of the antenna coil 2 in the axial direction of the vacuum tube 1. The heat radiating member 7 is in thermal contact with the antenna coil 2 and the insulating film 6. The heat radiating member 7 is preferably a non-conductive material having elasticity (for example, silicon resin), but it is also possible to use a non-conductive material having no elasticity (for example, an adhesive in which ceramic is melted). When a silicon resin is used as the heat radiating member 7, for example, a silicon-based thermosetting resin is applied to the gap of the lead wire portion of the antenna coil 2 and heat-cured to form the heat radiating member 7.

According to the plasma generator according to the first embodiment configured as described above, by forming the Faraday shield film 5 on the outer peripheral surface of the vacuum tube 1, the antenna coil 2 is brought closer to the vacuum tube 1 than in the case of the conventional metal plate. be able to. As a result, the antenna coil 2 can be brought closer to the plasma generated in the vacuum tube 1 than in the case of the conventional metal plate. Therefore, it is possible to maximize the degree of inductive coupling between the antenna coil 2 and the plasma while suppressing the degree of electrostatic coupling between the antenna coil 2 and the plasma.

Further, since the Faraday shield film 5 is a thin film layer having a thickness of 10 μm or more and less than 100 μm formed by thermal spraying, the antenna coil 2 can be arranged in the vicinity of the vacuum tube 1, and the antenna coil 2 and the plasma are inductively coupled. The degree of can be improved.

Further, since the Faraday shield film 5 is covered with the insulating film 6, the discharge between the antenna coil 2 and the Faraday shield can be suppressed, and the antenna coil 2 can be arranged closer to the vacuum tube 1. Therefore, the degree of inductively coupled between the antenna coil 2 and the plasma can be improved.

Furthermore, since the insulating film 6 is a thin film layer having a thickness of 10 μm or more and less than 100 μm formed by thermal spraying, the antenna coil 2 can be arranged in the vicinity of the vacuum tube 1, and the antenna coil 2 and the plasma are inductively coupled. The degree of can be improved.

Furthermore, since a plurality of Faraday shield films 5 are formed apart in the circumferential direction, it is possible to prevent the eddy current induced by the magnetic field formed by the antenna coil 2 from flowing in the circumferential direction of the vacuum tube 1. ..

Furthermore, the antenna coil 2 having the refrigerant flow path 2a is in thermal contact with the insulating film 6. Therefore, the vacuum tube 1 can be cooled by passing the refrigerant through the antenna coil 2.

Furthermore, the antenna coil 2 is an edgewise coil and is in direct or indirect surface contact with the insulating film 6. Therefore, the vacuum tube 1 can be cooled more efficiently.

Furthermore, the insulating film 6 covers the entire circumference of the vacuum tube 1 in the circumferential direction. Therefore, the outer peripheral surface of the vacuum tube 1 can be uniformly leveled as compared with the case where the insulating film 6 is formed only on the Faraday shield film 5. Therefore, the contact area between the antenna coil 2 and the vacuum tube 1 can be increased to improve the cooling property.

Furthermore, the heat radiating member 7 is arranged in the gap of the conducting wire portion constituting the antenna coil 2. Therefore, the heat of the vacuum tube 1 is released through the antenna coil 2 and the heat radiating member 7. Therefore, the vacuum tube 1 can be cooled more efficiently.

Furthermore, since the heat dissipation member 7 has elasticity, it can cope with the thermal expansion of the antenna coil 2.

Furthermore, since the heat radiating member 7 is made of silicon resin, it is possible to secure the insulating property and the required thermal conductivity.

In the first embodiment, an example in which the insulating film 6 is directly sprayed onto the Faraday shield film 5 has been described, but when a non-conductive material (insulating film 6) is formed on the conductive material (Faraday shield film 5), heterogeneous bonding occurs. Therefore, it may be difficult to form the insulating film 6 in a wide range. In such a case, an intermediate layer made of a functionally graded material having intermediate physical properties between the conductive material of the Faraday shield film 5 and the non-conductive material of the insulating film 6 is formed between the Faraday shield film 5 and the insulating film 6. May be. The intermediate layer may also be formed by spraying the functionally graded material.
Similarly, when the Faraday shield film 5 (conductive material) is formed on the vacuum tube 1 (non-conductive material), it becomes a heterogeneous bond, so that it is intermediate between the non-conductive material of the vacuum tube 1 and the conductive material of the Faraday shield film 5. An intermediate layer made of a functionally graded material having physical properties may be formed between the vacuum tube 1 and the Faraday shield film 5.

Although the edgewise coil is exemplified as the antenna coil 2, the cross-sectional shape of the conducting wire constituting the antenna coil 2 is not particularly limited, and may be any other shape. The cross-sectional shape of the antenna coil 2 is preferably a shape that can increase the contact area between the antenna coil 2 and the insulating film 6 by using a heat conductive material.

(Embodiment 2)
Since the plasma generator according to the second embodiment has a different configuration from that of the first embodiment in that the Faraday shield film 5 is connected to the reference potential, the above differences will be mainly described below. Since other configurations and actions and effects are the same as those in the first embodiment, the corresponding parts are designated by the same reference numerals and detailed description thereof will be omitted.

FIG. 7 is a perspective view showing a configuration example of the vacuum tube 1 and the antenna coil 2 according to the second embodiment. The plasma generator according to the second embodiment has the same vacuum tube 1, antenna coil 2, Faraday shield film 5, insulating film 6 and the like as in the first embodiment. Of the plurality of Faraday shield films 5, only a part of the Faraday shield films 5 is connected to the housing (not shown) having a reference potential via the ground wire 8.

As described above, the Faraday shield film 5 is used to weaken the degree of electrostatic coupling between the antenna coil 2 and the plasma, but the degree of electrostatic coupling differs depending on whether or not the antenna coil 2 is connected to the reference potential.

Since the potential of the Faraday shield film 5 connected to the reference potential is determined by the reference potential (usually 0 [V]), there is no temporal change. That is, since the potential is always a constant value regardless of the change in the potential of the antenna coil 2, the high frequency electric field does not enter the inside of the vacuum tube 1 at the portion where the Faraday shield film 5 connected to the reference potential is formed.

On the other hand, since the potential of the Faraday shield film 5 that is not connected to the reference potential has not been determined, the potential changes according to the change in the potential of the antenna coil 2.
Therefore, in the portion where the Faraday shield film 5 not connected to the reference potential is formed, a high frequency electric field enters the inside of the vacuum tube 1. Of course, the magnitude of the high-frequency electric field that enters the inside of the vacuum tube 1 is smaller than that of the portion where the Faraday shield film 5 is not formed, but it enters the inside of the vacuum tube 1 more than the case of the Faraday shield film 5 connected to the reference potential. The magnitude of the high frequency electric field is large.

Therefore, for the purpose of weakening the degree of electrostatic coupling between the antenna coil 2 and the plasma, it is more effective to use the Faraday shield film 5 connected to the reference potential.
However, as the degree of electrostatic coupling weakens, the ignitability of the plasma decreases. Therefore, in order to achieve the purpose of weakening the degree of electrostatic coupling between the antenna coil 2 and the plasma while ensuring the ignitability of the plasma, the Faraday shield film 5 may be connected to the reference potential as necessary. Just do it.
For example, by adjusting the number of Faraday shield films 5 connected to the reference potential among the plurality of Faraday shield films 5, the ignitability of the plasma and the degree of electrostatic coupling can be adjusted.

However, if the degree of electrostatic coupling in the circumferential direction of the vacuum tube 1 is not uniform, the state of the plasma generated inside the vacuum tube 1 is biased, and a portion having a high plasma density and a portion having a low plasma density are generated. The more non-uniform it is, the more the plasma density will be different. Further, since the inner wall of the vacuum tube 1 has a higher degree of wear in the portion having a high plasma density than in the portion having a low plasma density, the larger the difference in plasma density, the shorter the life of the vacuum tube 1.

However, due to the structure, there are a portion where the Faraday shield film 5 is formed and a portion where the Faraday shield film 5 is not formed, so that the degree of electrostatic coupling cannot be made uniform. Therefore, even when the Faraday shield film 5 connected to the reference potential is provided, it is preferable to devise a device to make the degree of electrostatic coupling in the circumferential direction of the vacuum tube 1 as close as possible.

For example, the Faraday shield film 5 connected to the reference potential and the Faraday shield film 5 not connected to the reference potential may be alternately provided along the circumferential direction of the vacuum tube 1.
At this time, it is preferable that a plurality of Faraday shield films 5 connected to the reference potential and a plurality of Faraday shield films 5 not connected to the reference potential are provided at equal intervals in the circumferential direction of the vacuum tube 1, respectively. By doing so, the isotropic property of the vacuum tube 1 in the circumferential direction can be improved, and the uniformity of the plasma can be improved.

Even in the configuration as in the first embodiment, it is preferable that a plurality of Faraday shield films 5 are provided at equal intervals in the circumferential direction of 1.

In the second embodiment, an example in which a part of the Faraday shield film 5 is constantly connected to the reference potential by the ground wire 8 has been described, but as shown in FIG. 8, the space between the Faraday shield film 5 and the reference potential is opened and closed. A switch 81 is provided on the ground wire 8, and a control unit 82 for controlling the opening and closing of the switch is provided so as to connect the Faraday shield film 5 to a housing (not shown) serving as a reference potential at an arbitrary timing. Is also good. In this embodiment, the configuration in which the switch 81 and the control unit 82 are combined is the switching means.

For example, when the plasma is ignited, a relatively large high-frequency electric field is required, but after the plasma is ignited, the magnitude of the high-frequency electric field is not required as much as when the plasma is ignited. Therefore, after ignition of the plasma, it may be desirable to make the magnitude of the high-frequency electric field entering the inside of the vacuum tube 1 smaller than that at the time of ignition of the plasma.

Such a case can be dealt with by reducing the output of the high frequency power supply 3 after ignition of the plasma, but it can also be adjusted by the presence or absence of connection to the reference potential of the Faraday shield film 5.

Specifically, when the plasma is ignited, the switch 81 is opened so that the Faraday shield film 5 is not connected to the housing (not shown) having a reference potential via the ground wire 8. Further, after the plasma is ignited, the switch 81 may be closed so that the Faraday shield film 5 is connected to the housing (not shown) having a reference potential via the ground wire 8. The switch 81 is opened and closed by the control unit 82.

Further, in FIG. 8, although one Faraday shield film 5 is connected to the reference potential via the ground wire 8, a plurality of Faraday shield films 5 may be connected to the reference potential via the ground wire 8. Further, since there is a switching means, all the Faraday shield films 5 may be connected to the reference potential via the ground wire 8.

The embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims, not the above-mentioned meaning, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Vacuum tube 1a Inlet 1b Outlet 2 Antenna coil 2a Refrigerant flow path 3 High frequency power supply 4 Impedance matching circuit 5 Faraday shield film 6 Insulation film 7 Heat dissipation member 8 Ground wire 81 Switch 82 Control unit

Claims (3)

A plasma generator including a vacuum tube into which a material gas flows and an antenna coil wound around the outer circumference of the vacuum tube to generate plasma of the material gas in the vacuum tube.
A Faraday shield film made of a conductive material formed on the outer peripheral surface of the vacuum tube is provided .
It has an intermediate layer between the vacuum tube and the Faraday shield film.
Plasma generator. A plasma generator including a vacuum tube into which a material gas flows and an antenna coil wound around the outer circumference of the vacuum tube to generate plasma of the material gas in the vacuum tube.
A Faraday shield film made of a conductive material formed on the outer peripheral surface of the vacuum tube, and
With the insulating film covering the Faraday shield film
Equipped with
It has an intermediate layer between the Faraday shield film and the insulating film.
Plasma generator. It has an intermediate layer between the vacuum tube and the Faraday shield film.
The plasma generator according to claim 2.

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