JPH06128733A - Ion beam device - Google Patents

Abstract

PURPOSE:To form a wide-sheet heavy current ion beam increased in plasma density and excellent in uniformity of the lateral density by successively arranging plural rectangular-sectioned floating electrodes, a diffusion chamber, a slit electrode, an anode, etc., in the ion beam device. CONSTITUTION:A cathode 2 is arranged in a cathode housing chamber 1 in an ion beam device, and plural floating electrodes 3 and 4 having a rectangular- sectioned discharge passage 4b of the same width as an ion beam are furnished in succession in the chamber 1 through an insulator. An anode 5 provided with a rectangular-sectioned opening is provided in front of the electrodes 3 and 4 and a drawer electrode 6 in front of the anode, and sheet plasma producing magnets 7 and 8 are arranged around the electrodes 3 and 4. An electric discharge is generated by the potential difference between the cathode 2 and anode 5, plasma is produced in the chamber 1 and in the discharge passage 4b, the sheet plasma is formed over the entire width of the discharge passage 4b by the parallel magnetic fields in the discharge passage 4b resulting from the magnets 7 and 8, and a sheet ion beam is emitted from the drawer electrode 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam device capable of obtaining a wide sheet-shaped ion beam.

[0002]

2. Description of the Related Art A conventional ion beam apparatus is shown in FIG. 3, in which the horizontal direction is the z-axis and the vertical direction is the y-axis.
The x-axis is the direction perpendicular to the axis and the drawing. A cathode 2 is arranged in the cathode housing chamber 1, and a plurality of floating electrodes 3 each having a truncated pyramidal cavity are provided at the tip of the cathode housing chamber 1 via an insulator (not shown) along the z-axis. The insides of the plurality of floating electrodes 3 which are continuously provided coaxially in the direction are tapered hollows. A plurality of floating electrodes 4 of the same shape having a rectangular cross section slit 4a having a long side in the x-axis direction and a short side in the y-axis direction at the center of the tips of the plurality of floating electrodes 3
Are connected coaxially in the x-axis direction via an insulator (not shown), and each slit 4a forms a discharge path 4b having a rectangular cross section in the z-axis direction. An anode 5 is connected to the tip of the floating electrode 4 in the z-axis direction via an insulator (not shown), and an opening 5a having the same shape as the slit 4a of the floating electrode 4 is provided at the center of the anode 5. The opening 5a communicates with the discharge path 4b. An extraction electrode 6 is arranged in front of the anode 5, and an ion extraction port 6a is provided in the center of the extraction electrode 6. A sheet plasma forming magnet 7 is disposed above the plurality of floating electrodes 4 coaxially arranged in the z-axis direction, and a sheet plasma forming magnet 8 is disposed below the floating electrodes 4. The sheet plasma forming magnets 7 and 8 form a parallel magnetic field that is parallel to the z axis in the discharge path 4b. The sheet plasma forming magnet 7 is formed by winding a coil 7b around the U-shaped pole piece 7a, and the sheet plasma forming magnet 8 is also formed by winding a coil 8b around the U-shaped pole piece 8a. Has been done.

In the figure, 9 is a cusp magnetic field region on the cathode side, 10 is a cusp magnetic field region on the anode side, and 11 is a gas introducing pipe for introducing an operating gas into the cathode housing chamber 1.

In such an ion beam apparatus, discharge occurs due to the potential difference between the cathode 2 and the anode 5, and plasma is generated in the cathode housing chamber 1 and the discharge path 4b. However, the plasma in the discharge path 4b is formed by the rectangular cross section of the discharge path 4b and the sheet plasma forming magnets 7 and 8.
Due to the parallel magnetic field in b, the discharge path 4b becomes a thin sheet having a wide width. Then, by temporarily releasing the magnetic field constraint in the cusp magnetic field region 10 on the anode side, the density distribution in the width direction of the plasma is made uniform, and a high density plasma having good width direction uniformity is formed in the openings 5a of the anode 5. Form. After that, the ions in the high-density plasma are extracted by the extraction electrode 6 and pass through the ion extraction port 6a.

The plurality of floating electrodes 4 have a function of reducing the gas conductance of the discharge path 4b to reduce the amount of working gas introduced into the cathode housing chamber 1 from the gas introducing pipe 11.

[0006]

In the conventional ion beam apparatus, the discharge path 4b is formed by the rectangular cross section of the discharge path 4b and the parallel magnetic field in the discharge path 4b by the sheet plasma forming magnets 7 and 8 as described above. A thin sheet-like plasma that spreads over the entire width of the plasma is formed, and the magnetic field is once restrained in the cusp magnetic field region 10 on the anode side to make the density distribution of the plasma uniform in the width direction and to open the anode 5 In 5a, a high density plasma having good uniformity in the width direction is formed.

In this case, in order to form a thin sheet-like plasma that spreads to the full width of the discharge path 4b, the plane including the central axis of the discharge path 4b (XZ plane) and the central axis of the magnetic field. It is necessary to exactly match the plane including X (XZ plane) so that the bias of the plasma due to the interaction between the magnetic field and the electric field does not occur.

However, in the discharge path 4b having a width of several tens of cm, it is very difficult to make the above two surfaces coincide with each other over the entire area of the discharge path 4b, so that the plasma is biased to a part of the discharge path 4b. . In addition, since the anode-side cusp magnetic field region 10 is located in the middle of the plurality of floating electrode groups 4 in series, a region for sufficiently diffusing the plasma is not secured, and the plasma density distribution in the width direction can be made uniform. It wasn't done enough. As a result, the density distribution of the plasma in the width direction has a shape shown by the broken line in FIG. 3, and there is a problem that an ion beam with good uniformity in the width direction cannot be obtained.

It is an object of the present invention to provide an ion beam device which solves the conventional problems and is capable of obtaining a large current ion beam with good uniformity in the width direction.

[0010]

In order to achieve the above object, the present invention provides a discharge passage having a rectangular cross section having the same width as the ion beam width in an inside of a cathode accommodating chamber in which a cathode is arranged via an insulator. A plurality of floating electrodes are provided in series, an anode having an opening with a rectangular cross section is arranged in front of the floating electrode group, and an extraction electrode is arranged in front of the anode. In the ion beam device in which the sheet plasma forming magnets are arranged above and below or on the left and right to form a magnetic field in the discharge path having a rectangular cross section, a diffusion chamber and a slit electrode are provided between the plurality of floating electrodes and the anode, It is characterized in that the floating electrode, the diffusion chamber, the slit electrode and the anode are arranged in this order.

[0011]

In the present invention, a discharge is generated due to the potential difference between the cathode and the anode, and plasma is generated in the cathode accommodating chamber and the discharge path. The plasma is generated in the cusp magnetic field region near the diffusion chamber. Since the magnetic field restraining force is reduced in, the magnetic field restraint force is once expanded in the vertical direction (y-axis direction) and the horizontal direction (x-axis direction), and then converges again toward the anode to form a sheet. At that time, by adjusting the potential difference between the diffusion chamber and the anode,
The plasma becomes dense. Further, by disposing the slit electrode between the diffusion chamber and the anode, the density of the plasma becomes higher and the uniformity of the lateral density is improved. In the discharge state, the plasma in the cathode storage chamber and the discharge passage is biased. Utilizing this phenomenon, the discharge path is made into a narrow rectangular cross section or circular cross section shape to further reduce the gas conductance of the discharge path.
The amount of working gas can be reduced.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. An ion beam device according to an embodiment of the present invention is shown in FIG. In the figure, the horizontal direction is z
The axis is perpendicular to the y-axis, and the direction perpendicular to the drawing is the x-axis. A cathode 2 is arranged in the cathode housing chamber 1, and a plurality of floating electrodes 3 each having a truncated pyramidal cavity are provided at the tip of the cathode housing chamber 1 via an insulator (not shown) along the z-axis. The insides of the plurality of floating electrodes 3 which are continuously provided coaxially in the direction are tapered hollows. At the tips of the floating electrodes 3, a plurality of floating electrodes 4 of the same shape having a slit 4a having a rectangular cross section having a long side in the x-axis direction and a short side in the y-axis direction at the center are made of an insulator (not shown). Via a plurality of the floating electrodes 4 connected coaxially in the z-axis direction, a discharge path 4b having a rectangular cross section is formed by the slits 4a in the z-axis direction. An anode 5 is arranged in front of the floating electrode 4 in the z-axis direction.
It has an opening 5a having the same shape as the slit 4a. A diffusion chamber 21 is arranged between the floating electrode 4 and the anode 5, and a slit electrode 22 is arranged between the diffusion chamber 21 and the anode 5. for that reason,
Floating electrode 4, diffusion chamber 21, slit electrode 22,
The anodes 5 are arranged in the z-axis direction in this order. An extraction electrode 6 is arranged in front of the anode 5, and an ion extraction port 6a is provided in the center of the extraction electrode 6. A sheet plasma forming magnet 7 is disposed above the plurality of floating electrodes 4 coaxially arranged in the z-axis direction, and a sheet plasma forming magnet 8 is disposed below the floating electrodes 4. A parallel magnetic field is formed in the discharge path 4b by the sheet plasma forming magnets 7 and 8. The sheet plasma forming magnet 7 is formed by winding a coil 7b around the U-shaped pole piece 7a, and the sheet plasma forming magnet 8 is also formed by winding a coil 8b around the U-shaped pole piece 8a. Has been done.

In the figure, 9 is a cathode side cusp magnetic field region and 10 is an anode side cusp magnetic field region, which is formed near the diffusion chamber 21. Reference numeral 11 is a gas introduction pipe for introducing the working gas into the cathode housing chamber 1.

In such an embodiment, the cathode 2
Discharge occurs due to the potential difference between the anode 5 and the anode 5, and plasma is generated in the cathode storage chamber 1 and the discharge path 4b.
Since the magnetic field restraint force decreases in the anode-side cusp magnetic field region 10 in the vicinity of 1, the magnetic field restraining force once spreads in the vertical direction (y-axis direction) and the horizontal direction (x-axis direction) and then converges again toward the anode 5 to form a sheet. become. At that time, the plasma has a high density by adjusting the potential difference between the diffusion chamber 21 and the anode 5. Further, by disposing the slit electrode 22 between the diffusion chamber 21 and the anode 5, the density of plasma is further increased and the uniformity of the density in the lateral direction (x-axis direction) is improved. . The solid line in FIG. 3 shows the density distribution in the width direction of plasma in the example.

By the way, in the above embodiment, the discharge path 4b has a wide rectangular cross section. However, since the plasma in the discharge path 4b is concentrated in a part of the discharge path, a narrow rectangular shape is used instead. It may have a cross section or a circular cross section. By doing so, it becomes possible to reduce the amount of working gas. A plurality of floating electrodes 3 are connected to the tip of the cathode housing chamber 1 to form a hollow space inside the plurality of floating electrodes 3. However, instead of the plurality of floating electrodes 3, the cathode housing chamber 1 itself. Alternatively, the tip may be a cavity of a rectangular support.

[0016]

According to the present invention, the diffusion chamber and the slit electrode are provided between the plurality of floating electrodes and the anode as described above, and the floating electrode, the diffusion chamber, the slit electrode and the anode are arranged in this order. A wide sheet-like plasma having a high plasma density and good lateral density uniformity is generated, and a wide high-current ion beam with good uniformity can be obtained.

[Brief description of drawings]

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

FIG. 2 is an explanatory view showing a conventional ion source for sheet plasma formation.

FIG. 3 is a graph showing the density distribution of plasma in the width direction.

[Explanation of symbols]

1 Cathode storage chamber 2 Cathode 3 Floating electrode 4 Floating electrode 4a ... Slit 5 ... Anode 6 ... Extractor electrode 6a ... Ion extraction Mouth 7: Magnet for sheet plasma formation 7a: C-shaped pole piece 7b: Coil 8:・ ・ ・ ・ Sheet plasma forming magnet 8a ・ ・ ・ ・ ・ ・ ・ C-shaped pole piece 8b ・ ・ ・ ・ ・ Coil 9 ・ ・ ・ ・ ・ ・ ・ ・ Cathode side cusp magnetic field Area 10 ・ ・ ・ ・ ・ ・ Anode side cusp magnetic field area 11 ・ ・ ・ ・ ・ ・ ・ Gas introduction tube 21 ・ ・ ・ ・ ・ ・ ・ Diffusion chamber Over 22 ......... slit electrode

Claims (1)

[Claims] 1. A plurality of floating electrodes having a discharge path of a rectangular cross section having the same width as the ion beam width are connected in series to a cathode housing chamber having a cathode inside through an insulator and in front of the floating electrode group. Arrange an anode with an opening of rectangular cross section,
Further, an extraction electrode is arranged in front of the anode, and further, sheet plasma forming magnets are arranged above and below or on the left and right of the floating electrode group to form a magnetic field in a discharge path having a rectangular cross section. 2. An ion beam apparatus, wherein a diffusion chamber and a slit electrode are provided between the plurality of floating electrodes and the anode, and the floating electrode, the diffusion chamber, the slit electrode and the anode are arranged in this order.