JP2909694B2 - Sheet plasma generation method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for generating a sheet plasma from a cylindrical plasma.

[0002]

2. Description of the Related Art When performing a surface treatment on a large-area workpiece using plasma, sheet plasma is extremely useful for performing uniform processing at high speed.

As a conventional sheet plasma generating method, there is known a method of flattening a cylindrical plasma into a sheet shape using a permanent magnet (Japanese Patent Publication No. 4-23400).
In the sheet plasma generation method, referring to FIGS. 9 and 10, a pair of permanent magnets 51 and 52 are arranged so as to sandwich a cylindrical plasma 50 formed by electric discharge in a magnetic field. , 52 with the same poles facing each other to form a strong repulsive magnetic field to compress and expand the columnar plasma 50, and to determine the magnitude of the magnetic field component of the permanent magnets 51, 52 in the axial direction of the columnar plasma 50 by the columnar plasma. By making it smaller than the co-directional magnetic field in the field of formation,
The sheet plasma flow 53 in the direction of the magnetic field in the field of the cylindrical plasma is formed.

In FIG. 1, B _Z0 is an initial axial magnetic field generated by a large-diameter magnetic field coil (not shown), and B _X , B _Y , and B _Z
Are the components of the magnetic field in the X, Y and Z axis directions by the permanent magnets 51 and 52, respectively.

[0005] Figure 11 is a diagram showing the magnetic field distribution in the Z-axis direction of the cylindrical plasma 50 side and the sheet plasma 53 side, the synthesis of the magnetic field B _Z of the Z-axis direction of the initial axial magnetic field B _Z0 and the permanent magnet It shows a magnetic field. Then, as the magnetic field distribution changes from (1) to (4), the initial axial magnetic field B _Z0
The strength has been increased.

By the way, in the conventional method, the cylindrical plasma 5
Z-axis direction of the magnetic field strength B _Z of the permanent magnets than the strength of the initial axial magnetic field B _Z0 in the region of 0 side is only small magnetic field distribution (2) Good a.

If the strength of the magnetic field in the same direction by the permanent magnets 51 and 52 is made smaller than the strength of the magnetic field in the axial direction of the cylindrical plasma 50 as described above, the magnetic field in the axial direction of the cylindrical plasma 50 becomes stronger. As shown in FIG.
A part of 0 runs straight in the Z-axis direction at the part indicated by arrow C.

[0008]

However, when a part of the columnar plasma runs in the Z-axis direction, as shown in FIG. 13, the formed sheet plasma has its central portion higher in the width direction and has a higher height in the width direction. There is a problem that uniformity cannot be obtained in the density distribution.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet plasma generating method and an apparatus thereof capable of making the density distribution particularly in the width direction uniform.

[0010]

According to the present invention, a permanent magnet is arranged so as to sandwich a cylindrical plasma formed by a discharge in a magnetic field, and the permanent magnets are made to face each other with the same polarity to generate a repulsive magnetic field. In the method for generating a sheet plasma, as the permanent magnets, a pair of first permanent magnets opposed to each other in a thickness direction of the sheet plasma and a pair of second permanent magnets opposed to both ends in a width direction of the sheet plasma. the first of these with bets, the plasma gun side slightly away from the second permanent magnets, these first, the intensity of the synthesized magnetic field with the magnetic field of the second magnetic field and a cylindrical plasma by the permanent magnets zero or zero with make close magnetic field region, to form a long cusp magnetic field region on the shaft in the width direction of the cylindrical plasma in that region, confining the plasma in the cusp magnetic field region, before confinement plasma First, which in the region of the second permanent magnet
It is characterized in that the sheet is formed into a sheet while being regulated by the first and second permanent magnets, and furthermore, the region is made equipotential to balance the magnetic field to form a sheet plasma having a uniform thickness.

Further, in the sheet plasma generating apparatus according to the present invention, a permanent magnet is arranged so as to sandwich a cylindrical plasma formed by a discharge in a magnetic field, and the permanent magnets are made to have the same poles opposed to each other by a repulsive magnetic field. In an apparatus for generating sheet plasma from plasma, an electromagnet that guides plasma generated from a plasma gun in a fixed direction and controls the strength of a magnetic field is disposed in a vacuum container, and a pair of sheets facing the thickness direction of the sheet plasma is provided. And a pair of second permanent magnets facing each other at both ends in the width direction of the sheet plasma are disposed in a vacuum vessel.
An equipotential metal plate is arranged near the first and second permanent magnets so as to surround the sheet plasma.

[0012]

An embodiment of the present invention will be described below.
FIG. 1 is a sectional view of a sheet plasma generating apparatus of the present invention, and FIG.
FIG. 2 is a sectional view taken along line AA in FIG. 1. 1 and 2, 1 is a base, 2 is a vacuum vessel mounted on the base 1, 3
Is a plasma gun that produces a cylindrical plasma, 4 is a ring-shaped external electromagnet that can control the strength of magnetic force, 5 is also a ring-shaped internal electromagnet that can control the strength of magnetic force, 1
Reference numeral 0 denotes a permanent magnet mounting device for forming a cylindrical plasma into a sheet plasma. Reference numeral 6 denotes an anode incorporating a permanent magnet provided on the side opposite to the plasma gun 3 in the vacuum vessel 2. Both the external electromagnet 4 and the internal electromagnet 5 generate a magnetic flux from right to left in FIG. 1 along a center line connecting the plasma gun 3 and the anode 6.

The permanent magnet mounting device 10 supports a table 11 fixed to the floor of the vacuum vessel 2, two guide columns 12 erected on the table 11, and an upper end of each of the guide columns 12. A connecting plate 13, two first supporting members 13 provided substantially at the center of the guide column 12 and supporting the left and right permanent magnets 15, and sandwiching the first supporting member 13; , Two second support members 14 slidably supported by the guide columns 12 and supporting the upper and lower permanent magnets 16, and a drive for moving the two second support members 14 closer to or farther away from each other. Mechanism 17 and the permanent magnet 1
And a metal plate 18 attached to the magnetic pole surfaces 5 and 16 via an insulator. The metal plates 18 are connected by metal wires or the like so as to be short-circuited to each other. Opposing permanent magnet 1
5, 5 are arranged so that the same polarity faces each other.

In the present embodiment, permanent magnets 15 and 16 having magnetic poles of the same polarity facing each other are arranged in four directions so as to surround the cylindrical plasma from the plasma gun 3. A cusp magnetic field is created by the magnetic field of the external electromagnet 4 and the internal electromagnet 5 to confine the plasma beam and perform plasma diffusion in the width direction. The magnetic field gradient for confinement at this time is 0.2 × 10 ^{3 to} 5.0 × 10 ⁴ (G
/ M).

A metal plate 18 is arranged so as to surround the plasma confined in the vicinity of the permanent magnets 15 and 16, and all the metal plates 18 facing the plasma are short-circuited so as to have the same potential. Is connected to the vacuum vessel 2 via a resistor so that it can be separated from the potential.

Referring to FIG. 3, in the present embodiment, the current of the external electromagnet 4 is controlled to determine the strength of the magnetic field in the region A on the side of the plasma gun 3 slightly away from the permanent magnets 15 and 16 so as to determine the strength of the cylindrical plasma. And the strength of the magnetic field in the same direction by the permanent magnets 15 and 16 is made substantially equal to zero or near zero.

In the embodiment, the metal plate 18 is provided with the permanent magnets 15 and 1.
6 are provided individually, but may be made of a single plate. In addition, in order to finely adjust the density near the edge of the sheet plasma, electrodes for fine adjustment are installed at both ends in the width direction of the portion flowing out of the plasma confinement portion in a sheet shape, and this potential is changed by changing the potential. It is possible to change the density in the vicinity.

In this embodiment, the metal plate 18 is made to have the same potential to form a sheet plasma having a more uniform thickness. May be added to make it possible to change the shape of the sheet plasma by giving a potential difference to the metal plate 18 in the vertical direction. Also, without making each metal plate 18 equal potential,
The potential of each metal plate 18 may be changed.

Compared with the conventional method, in the conventional method, the cylindrical plasma is converted into the sheet plasma using the permanent magnet, but the magnetic field distribution at this time restricts the trajectory of the electrons in the plasma. It is flattened so that the bundle of lines of magnetic force that are present is pushed out to the side. On the other hand, in the present invention, the permanent magnet 1
After a long cusp magnetic field region is created in the axial direction on the axis of the cylindrical plasma on the side of the plasma gun 3 slightly away from 5 and 16, electrons are once confined in this cusp magnetic field region and diffused in the width direction to form a plasma pool. It is characterized in that the electron flow leaking uniformly from the region along the cusp magnetic field in the width direction generates sheet plasma. The magnetic field distribution at this time is as shown in FIG. FIG. 3 shows permanent magnets 15 and 16.
The magnetic flux from the external electromagnet 4 and the internal electromagnet 5 as well as the magnetic flux from the external electromagnet 4 are shown.

The iron core of the permanent magnet is not divided, but is made into a cylindrical iron core 20 as seen from the axial direction of the cylindrical plasma as shown in FIG. 4, and permanent magnets 15 'and 16' are provided on the outer periphery of the iron core 20. May be. In this case, the strength of the magnetic field around the sheet plasma tends to be uniform.

Although the permanent magnets 15 and 16 are formed as a single unit, as shown in FIG. 5, the permanent magnets 15 "and 16"
May be divided into plural parts, and these permanent magnets 15 ″, 16 ″ may be sandwiched between iron cores 21, 22. The iron core 22 does not necessarily have to be a magnetic material, and may be a non-magnetic material such as SUS. The iron core 21 is on the side where the plasma passes, and the iron core 22 is on the support members 13 and 14 side.

When a large permanent magnet cannot be manufactured by itself, a plurality of small permanent magnets can be sandwiched between iron cores to have the same performance as a single large permanent magnet. In any case, by providing the iron core, the magnetic force of each small permanent magnet is made uniform by the iron core.

FIG. 6 is a diagram showing the measurement results of the magnetic field distribution shown in FIG. 3. The magnetic field distribution curve C1 is obtained when only the permanent magnets 15 and 16 are used without using the external electromagnet 4 and the internal electromagnet 5. It is the characteristic of. On the other hand, the magnetic field distribution curve C2 is a characteristic when the external electromagnet 4 and the internal electromagnet 5 are added. In the present embodiment, the magnetic field is controlled so that the magnetic field is close to zero in the area A shown in FIG. In this way, a cusp magnetic field is created on the axis of the cylindrical plasma in the region A. The resulting density distribution in the width direction of the sheet plasma is as shown in FIG. The magnetic field distribution is the same as that of FIG. 3, and FIG. 8 shows the density distribution of the sheet plasma in the width direction when the potentials of the metal plates 18 are made independent and each has a different potential.

In this embodiment, since the magnetic field is close to zero in the region A and a cusp magnetic field is formed, the plasma is confined in the region A before the cylindrical plasma is compressed between the permanent magnets 15 and 16, The confined plasma becomes a sheet while its outer shape is regulated by the permanent magnets 15 and 16.

On the other hand, in the conventional method, since the columnar plasma runs in the axial direction, the central portion in the width direction of the sheet is high.

In addition, in this embodiment, since the permanent magnets are used not only in the thickness direction but also in the width direction, the cylindrical plasma compressed by the permanent magnets in the vertical direction is restricted in the width direction within a certain range. Therefore, the thickness of the sheet becomes more uniform.

Further, a support member 13 for supporting a permanent magnet,
Since the electrodes 14 or the metal plates 18 are at the same potential, the plasma in the vicinity is not concentrated and drawn in one direction. In addition, if the metal plate 18 is provided, diffusion of plasma can be prevented.

[0028]

As described above, according to the present invention, it is possible to obtain a sheet plasma having higher uniformity in the density distribution in the width direction of the sheet plasma.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing a magnetic field distribution in a main part of the device of the present invention.

FIG. 4 is a view showing another example of the permanent magnet shown in FIG. 1;

FIG. 5 is a view showing still another example of the permanent magnet shown in FIG. 1;

6 is a diagram showing a measurement result of the magnetic field distribution shown in FIG.

FIG. 7 is a view showing a measurement result of a density distribution in a width direction of a sheet plasma obtained by the present invention.

FIG. 8 is a view showing a measurement result of a density distribution in a width direction of a sheet plasma obtained by a modification of the present invention.

FIG. 9 is a schematic configuration diagram for explaining a conventional sheet plasma generation method.

FIG. 10 is a diagram of the configuration shown in FIG. 9 as viewed from another direction.

FIG. 11 is a diagram showing the measurement results of the magnetic field distribution in the Z direction, which was tested by changing the strength of the initial axial magnetic field B _Z0 .

FIG. 12 is a diagram showing a magnetic field distribution in a main part of a conventional example.

FIG. 13 is a diagram showing a measurement result of a density distribution in a width direction of a sheet plasma obtained by a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Vacuum container 3 Plasma gun 4 External electromagnet 5 Internal electromagnet 6 Permanent magnet 10 Permanent magnet mounting device 11 Unit 12 Guide pillar 13 First support member 14 Second support member 15, 16 Permanent magnet 17 Drive mechanism 18 Metal Board

Claims (5)

(57) [Claims] 1. A method of generating a sheet plasma from a columnar plasma by disposing a permanent magnet so as to sandwich a columnar plasma formed by a discharge in a magnetic field, causing the permanent magnets to face each other with the same polarity, and using a repulsive magnetic field. As the permanent magnets, a pair of first permanent magnets opposed to each other in the thickness direction of the sheet plasma and a pair of second permanent magnets opposed to both ends in the width direction of the sheet plasma are used .
1. On the plasma gun side, which is slightly away from the second permanent magnet,
The magnetic field generated by the first and second permanent magnets and the magnetic field of the columnar plasma are used to form a magnetic field region of zero or near zero, and a cusp magnetic field that is long in the width direction on the axis of the columnar plasma in that region. Forming a region, confining the plasma in the cusp field region, and confining the confined plasma to the first,
In the area of the second permanent magnet, the first and second permanent magnets are regulated to form a sheet while being regulated by the first and second permanent magnets, and the area is equipotential to balance the magnetic field to generate a sheet plasma having a uniform thickness. Forming a sheet plasma. 2. A pre-Symbol first, second permanent magnet is provided around the tubular core when viewed from the axial direction of the circular pillar plasma
Cage, these first sheet plasma generating method according to claim 1, wherein also form cusp magnetic field region by applying a magnetic field of the second permanent magnet as a magnetic field in the thickness direction and the width direction by using the core. 3. A sheet is provided by independently providing a metal member to the first and second permanent magnets via an insulator so as to make the region have the same potential, and adjusting the potential of each metal member. 2. The sheet plasma generation method according to claim 1, wherein the density distribution near the edge of the plasma is finely adjusted. 4. An apparatus for generating a sheet plasma from a cylindrical plasma by a repulsive magnetic field by disposing a permanent magnet so as to sandwich a cylindrical plasma formed by a discharge in a magnetic field and facing the permanent magnets with the same poles facing each other. An electromagnet that guides plasma generated from a plasma gun in a certain direction and controls the strength of a magnetic field is disposed in a vacuum vessel, and a pair of first permanent magnets and a pair of sheet magnets facing in a thickness direction of the sheet plasma. And a pair of second permanent magnets facing each other at both ends in the width direction are disposed in a vacuum vessel, and an equipotential metal plate is arranged near the first and second permanent magnets so as to surround the sheet plasma. A sheet plasma generating apparatus, wherein: 5. Before Symbol first, second permanent magnet is provided around the tubular core when viewed from the axial direction of the cylinder plasma
Sheet plasma generating apparatus according to claim 4, wherein there.