JPH04368754A - Ion source - Google Patents

Abstract

PURPOSE:To sufficiently enhance an ionization efficiency (gas efficiency) and a power efficiency. CONSTITUTION:A partition member 6 containing a slit 8 is provided in an ion formation space in such a way that the ion formation space is divided into a gas introducing space 13, in which an ionized gas is introduced, and an ion extracting space 14, in which the generated ion being extracted; permanent magnets 7 are mounted on the partition member 6 in such a way that lines-of-magnetic-force 12 pass through the slit 8. When an ion source gas flows from the gas introducing space 13 to the ion extracting space 14, it is throttled in such a way that the flow of the ion source gas passes through the slit 8 in the partition member 6. The flow of a plasma formed in the gas introducing space 13 is also throttled by the action of the lines-of-magnetic-force 12 in such a way that it passes through the slit 8 in the partition member 6. As a result, when an arc discharge takes place through the slit 8 in the partition member 6, ionization of the ion source gas is accelerated at and about the slit 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a long type or large area type ion source that ionizes an ion source gas by low-pressure arc discharge.

0002

2. Description of the Related Art FIG. 5 shows a so-called bucket-type ion source as a conventional example of a large-area ion source. In FIG. 5, an arc chamber (anode) 81 has a gas inlet 84 and an ion extraction port 88, and has a rod-shaped permanent magnet 8 on its outer wall.
2 are arranged in a row to create a local multipolar magnetic field near the inner wall surface.

Inside the arc chamber (anode) 81,
A filament (cathode) for thermionic emission that serves as a primary electron source
One or more 83 are provided. Arc chamber (
An ion extraction electrode system 87 is disposed in front of an ion extraction port 88 in the anode (anode) 81 . Filament (cathode)
83 is connected to a filament power source 85 for thermionic emission, and a discharge power source 86 for arc discharge is connected between the arc chamber (anode) 81 and the filament (cathode) 83.

In the ion source configured as described above, in order to generate plasma, the filament (cathode) 83 is made red hot while introducing the ion source gas from the gas inlet 84, and the arc chamber (anode) 81 and A low-pressure arc discharge is caused between the filament (cathode) 83 and the filament (cathode) 83. As a result, the primary electrons (thermoelectrons) emitted from the filament (cathode) 83 collide with atoms or molecules of the ion source gas, turning the ion source gas into plasma. At this time, the primary electrons (thermoelectrons) are transferred to the arc chamber (anode) 81
Confinement of electrons is good because they cannot reach in a straight line due to the action of an external magnetic field, increasing their effective range.

[0005]

However, in the above-mentioned ion source, the range of electrons is linear in the non-magnetic field region at the center of the arc chamber (anode) 81, and the ionization efficiency (gas efficiency) and power It has been difficult to sufficiently increase efficiency. Therefore, an object of the present invention is to provide an ion source that can sufficiently increase ionization efficiency (gas efficiency) and power efficiency.

[0006]

[Means for Solving the Problems] The ion source of the present invention includes:
A partition member having a small hole or slit is arranged in the ion generation space so as to partition the ion generation space into a gas introduction space into which an ion source gas is introduced and an ion extraction space from which generated ions are extracted. A magnet is provided in the partition member so that lines of magnetic force pass through the slit, and a cathode and an anode are arranged so that the small hole or slit becomes part of the discharge path.

[0007]

[Operation] According to the configuration of the present invention, the ion generation space is divided into a gas introduction space where the ion source gas is introduced and an ion extraction space where the generated ions are extracted.
Since the partition member having small holes or slits is arranged in the ion generation space, when the ion source gas flows from the gas introduction space to the ion extraction space, the flow of the ion source gas passes through the small holes or slits in the partition member. The density increases at these small holes or slits. In addition, by providing a magnet in the partition member so that the lines of magnetic force pass through the small holes or slits, the flow of plasma generated in the gas introduction space also passes through the small holes or slits in the partition member due to the action of the lines of magnetic force. Narrowed down. As a result, when arc discharge is performed between the cathode and the anode through the small holes or slits of the partition member, ionization of the ion source gas is promoted in the small holes or slits.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An ion source according to a first embodiment of the present invention will be explained based on FIG. This example shows an ion source that generates a slit beam. In FIG. 1, a cathode chamber 1 is open at the front, and has a filament (cathode) 2 disposed therein and a gas inlet 3. A metal partition member (to serve as an intermediate electrode) 6 having a slit 8 is arranged at the front position of the cathode chamber 1, and a magnet (permanent magnet) 7 is placed in the partition member 6 so that the lines of magnetic force 12 pass through the slit 8. It has a built-in location.

Further, an anode 9 is disposed in front of the partition member 6, and an extraction electrode 11 is further disposed in front of the anode 9. A filament power source 4 for thermionic emission is connected to the filament (cathode) 2, a discharge power source 5 is connected between the filament (cathode) 2 and the anode 9, and a resistor 10 is connected between the anode 9 and the partition member 6. Connected via. The partition member 6 has a function of partitioning the ion generation space into a space in the cathode chamber 1, that is, a gas introduction space 13, and a space in the center of the anode 9, that is, an ion extraction space 14. Further, the magnets 7 are rod-shaped and have magnetic poles on two opposing faces parallel to the longitudinal direction, and are arranged on both sides with the slit 8 in between, with the same poles of the two magnets 7 facing forward. There is. Furthermore, the slit 8 is part of the discharge path between the filament (cathode) 2 and the anode 9.

In the ion source configured as described above, the ion source gas is introduced from the gas inlet 3 provided in the cathode chamber 1, and the ion source gas is fed between the red-hot filament (cathode) 2 and the anode 9 by the filament power source 4. Then, arc discharge is started by the discharge power source 5. When a discharge occurs, when the ion source gas flows from the gas introduction space 13 to the ion extraction space 14, the flow of the ion source gas is narrowed to the slit 8 of the partition member 6, which becomes a part of the discharge path, and the ion source gas flows through the slit 8. At the same time, the plasma flow generated in the gas introduction space 13 due to the magnetic field (indicated by magnetic lines of force 12) generated by the magnet 7 embedded in the partition member 6 also increases through the slit 8.
It will be narrowed down to. Therefore, when arc discharge is performed between the filament (cathode) 2 and the anode 9 through the slit 8 of the partition member 6, ionization of the ion source gas is promoted inside the slit 8 of the partition member 6.

According to the ion source of this embodiment, the ion generation space is divided into a gas introduction space 13 into which the ion source gas is introduced and an ion extraction space 14 into which the generated ions are extracted.
Since the partition member 6 having the slit 8 is arranged in the ion generation space so as to partition the ion generation space into two parts, the flow of the ion source gas in the ion generation space can be narrowed down so as to pass through the slit 8 of the partition member 6. Furthermore, since the magnet 7 is provided on the partition member 6 so that the magnetic lines of force 12 pass through the slit 8, the flow of plasma generated in the gas introduction space 13 is also caused to pass through the slit 8 of the partition member 6 by the action of the magnetic lines of force 12. can be narrowed down to.

As a result, when arc discharge occurs between the filament (cathode) 2 and the anode 9 through the slit 8 of the partition member 6, ionization of the gas can be promoted at the slit 8 of the partition member 6, resulting in less It becomes possible to operate with a small gas flow rate and low electric power. In other words, ionization efficiency and power efficiency can be improved. Furthermore, since the gas flow rate can be reduced, the capacity of the evacuation pump can be reduced, and the cost of the device can be reduced.

In the above embodiment, the partition plate 6 having the slits 8 is used, but instead of the slits 8, a partition plate having a large number of small holes arranged in a row may be used. An ion source according to a second embodiment of the invention will be explained based on FIG. This example shows an ion source that generates a plane beam. In FIG. 2, 21 is a cathode chamber, 22 is a filament (cathode), 23 is a gas inlet, 24 is a filament power source, 25 is a discharge power source, 26 is a metal partition member (becomes an intermediate electrode), and 27 is a permanent magnet. 28 is a slit, 29 is an anode, 3 is a large number of bar-shaped magnets arranged in parallel.
0 is a resistance, 31 is an ion extraction electrode system, 32 is a line of magnetic force,
33 is a gas introduction space, and 34 is an ion extraction space.

The difference in structure from the first embodiment is that the slits (of course, rows of small holes may also be used) 2 provided in the partition member 26
8 are provided in parallel, and a rod-shaped magnet 27 is inserted into each slit 2.
8 is placed between them, and the opening area is increased.Other than that, the other configuration is the same as that of the embodiment shown in FIG. The operation and effect are also similar to the embodiment shown in FIG. A third embodiment of this invention will be described based on FIG. This embodiment shows an ion source that generates a plane beam like the second embodiment. In FIG. 3, 41 is a cathode chamber, 42 is a filament (cathode), 43 is a gas inlet, 44 is a filament power source, 45 is a discharge power source, 46 is a metal partition member (becomes an intermediate electrode), and 47 is an electromagnet. The electrical wires to be formed include a slit 48, an anode 49, a resistor 50, an ion extraction electrode system 51, lines of magnetic force 52, a gas introduction space 53, and an ion extraction space 54.

The difference in structure from the second embodiment is that an insulated electric wire 47 is built into the partition member 46 instead of a permanent magnet, and by energizing the electric wire 47, an electromagnet is created by the electric wire 47 and a magnetic field is generated. The other configuration is the same as that of the embodiment shown in FIG. 2, and the operation and effect are also the same as those of the embodiment shown in FIG. The electric wire 47 described above is a continuous wire that is folded back, and the current direction is alternately reversed, so that the direction of the magnetic lines of force 52 is alternately reversed in each slit 48. .

A fourth embodiment of the present invention will be explained based on FIG. 4. This embodiment shows an ion source that generates a plane beam like the second and third embodiments. In FIG. 4, 61 is a discharge chamber, 62 is an antenna for microwave radiation, 63 is a gas inlet, 64 is a microwave source, 65 is a discharge power source, and 66 is a metal partition member (cathode).
, 67 is a magnet (permanent magnet), 68 is a slit, 69 is an anode, 70 is an ion extraction electrode system, 71 is a line of magnetic force, 72 is a gas introduction space, and 73 is an ion extraction space.

The difference between this embodiment and the second embodiment is that the primary electron source for arc discharge is replaced with a filament.
The antenna 62 is excited by a microwave source 64, and a discharge power source 6 is connected between the partition member 66 and the anode 69.
5 are connected to cause arc discharge to occur using the partition member 66 as a cathode. Other configurations are similar to the embodiment shown in FIG.

In this embodiment, by supplying microwave power from the microwave source 64 to the antenna 62, a microwave discharge is generated within the gas introduction space 72, and primary electrons for arc discharge are generated by the microwave discharge. It is something. Other operations are similar to the embodiment shown in FIG.
The effects are also the same as in each of the above embodiments.

The cathode for causing arc discharge may have any structure such as a hot cathode, a cold cathode, or a plasma cathode.

[0020]

Effects of the Invention According to the ion source of the present invention, a small space is provided in the ion generation space so as to divide the ion generation space into a gas introduction space into which ion source gas is introduced and an ion extraction space from which generated ions are extracted. Since the partition member having holes or slits is disposed, the flow of the ion source gas in the ion generation space can be narrowed down so as to pass through the small holes or slits of the partition member. In addition, since a magnet is installed in the partition member so that the lines of magnetic force pass through the small holes or slits, the flow of plasma generated in the gas introduction space is also narrowed down so that it passes through the small holes or slits in the partition member due to the action of the magnetic lines of force. be able to.

As a result, when arc discharge occurs between the cathode and the anode through the small holes or slits of the partition member,
Ionization of gas can be promoted in the small holes or slits of the partition member, and operation can be performed with a small gas flow rate and with low electric power. In other words, ionization efficiency and power efficiency can be improved. moreover,
Since the gas flow rate can be reduced, the capacity of the evacuation pump can be reduced, and the cost of the device can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view showing the configuration of a first embodiment of the present invention.

FIG. 2 is a schematic plan view showing the configuration of a second embodiment of the invention.

FIG. 3 is a schematic plan view showing the configuration of a third embodiment of the invention.

FIG. 4 is a schematic plan view showing the configuration of a fourth embodiment of the invention.

FIG. 5 is a schematic plan view showing the configuration of an example of a conventional bucket-type ion source.

[Explanation of symbols]

1 Cathode chamber 2 Filament (cathode) 3 Gas inlet 4 Filament power supply 5 Discharge power supply 6 Partition member 7 Magnet 8 Slit 9 Anode 10 Resistance 11 Extraction electrode 12. Lines of magnetic force 13 Gas introduction space 14 Ion extraction space

Claims (1)

[Claims] 1. In an ion source that generates ions by ionizing an ion source gas by arc discharge between a cathode and an anode in an ion generation space, the ion generation space is used as a gas introduction space into which the ion source gas is introduced. A partition member having a small hole or slit is arranged in the ion generation space so as to partition it into an ion extraction space from which generated ions are extracted, and a magnet is attached to the partition member so that lines of magnetic force pass through the small hole or slit. An ion source characterized in that the cathode and the anode are arranged such that the small hole or slit is part of a discharge path.