JP2671733B2 - ECR type ion source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ECR type ion source utilizing electron cyclotron resonance (ECR), and more particularly to means for suppressing the spread of an ion beam extracted therefrom.

[0002]

2. Description of the Related Art A conventional example of this type of ECR type ion source is shown in FIG. The ECR type ion source includes a plasma generation container 2 that is a container for generating plasma 18, a magnetic coil 16 that generates a magnetic field in the plasma generation container 2 in the extraction direction of the ion beam 24, and a plasma generation container 2 of the plasma generation container 2. The ion beam 24 is provided from the plasma 18 in the plasma generation container 2 by the action of the electric field provided near the outside of the opening 4.
And an extraction electrode system 20 that draws out.

In the plasma generation container 2, for example, 2.45 GH is passed through the waveguide 6 and the microwave introduction window 8.
A microwave 10 of z is introduced. Also, the gas introduction pipe 1
The desired gas 14 to be ionized is introduced via 2.

In this example, the extraction electrode system 20 is composed of a suppression electrode 21 having a negative potential by a suppression power source 28 and a ground electrode 22 having a ground potential. These electrodes 21 and 22 are made of a non-magnetic material such as stainless steel or carbon. The plasma power generation container 2 has a drawing power source 26.
A positive voltage is applied.

A predetermined intensity (for example, microwave 10 of 2.45 GH) is generated in the plasma generating chamber 2 by the magnetic coil 16.
In the case of z, a magnetic field of about 875 Gauss) is generated, and when the microwave 10 and the gas 14 are introduced into the plasma generation container 2, the gas 14 is excited by microwave discharge and electron cyclotron resonance, and the plasma generation container 2 is excited. A plasma 18 is created inside. At this time, if the above voltage is applied to the plasma generation container 2 and the extraction electrode system 20, the action of the electric field causes
An ion beam 24 is extracted from the plasma 18. The negative potential suppression electrode 21 suppresses the backward flow of electrons from the downstream side toward the plasma generation container 2 when the ion beam 24 is extracted.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the CR type ion source, for example, as shown in FIG.
Although the magnetic field lines 17 generated by the magnetic coil 16 are configured to be substantially parallel to the extraction direction of the ion beam 24 in the plasma generation chamber 2, in a region slightly apart from the magnetic coil 16, more specifically, plasma generation is performed. On the downstream side of the vicinity of the opening 4 of the container 2, the magnetic field lines 17
Has a distribution spread in a direction perpendicular to the extraction direction of the ion beam 24.

Therefore, the ions in the plasma 18 in the plasma generating chamber 2 spread along the magnetic field lines 17 near the opening 4, and the ion beam 24 extracted from the opening 4 also near the extraction electrode system 20. 17 and spread, resulting in plasma 1
Ions and ion beams 24 in the plasma generation container 2
There is a problem that the ion beam 24 cannot be efficiently extracted because the ratio of collision with the structures such as the extraction electrode system 20 and the extraction electrode system 20 increases.

Therefore, according to the present invention, the distribution of the lines of magnetic force from the vicinity of the opening of the plasma generation container to the vicinity of the most downstream electrode of the extraction electrode system is made parallel to the extraction direction of the ion beam, so that the plasma in the plasma generation container ECR that suppresses the spread of the ion in the vicinity of the opening of the ion and the spread of the ion beam in the vicinity of the extraction electrode system to enable efficient extraction of the ion beam.
The main purpose is to provide a type ion source.

[0009]

In order to achieve the above object, the ECR type ion source of the present invention comprises an electrode on the most downstream side of a plurality of electrodes constituting the extraction electrode system as described above.
It is characterized in that only the poles are made of a magnetic material.

[0010]

[Operation] Of the plurality of electrodes forming the extraction electrode system, the maximum
By making only the electrode on the downstream side with a magnetic material, the magnetic force lines emitted from the magnetic coil are not disturbed by other electrodes.
In addition, it is drawn into the most downstream electrode made of this magnetic material and passes through it. As a result, the distribution of the magnetic field lines from the vicinity of the opening of the plasma generation vessel to the vicinity of the most downstream electrode of the extraction electrode system. Approaches parallel to the extraction direction of the ion beam. As a result, it is possible to suppress the spread of the ions in the plasma in the plasma generation container near the opening and the spread of the ion beam near the extraction electrode system, and to efficiently extract the ion beam.

[0011]

1 is a sectional view showing an ECR type ion source according to an embodiment of the present invention. Parts that are the same as or correspond to those in the conventional example of FIG. 3 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

In this embodiment, only the ground electrode 22a, which is the most downstream electrode of the electrodes constituting the extraction electrode system 20 as described above, is made of a magnetic material. More specifically, although the ground electrode 22a is made of iron plated with nickel in this embodiment, it may be made of ferritic stainless steel or the like.

By making only the ground electrode 22a from the magnetic material in this way, the magnetic force lines 17 emitted from the magnetic coil 16 are not disturbed by other electrodes as shown in FIG.
First, the magnetic field lines 17 are drawn into the ground electrode 22a and pass through the ground electrode 22a. As a result, the distribution of the magnetic field lines 17 from the vicinity of the opening 4 of the plasma generation container 2 to the vicinity of the most downstream electrode of the extraction electrode system 20 is The beam 24 approaches the direction parallel to the extraction direction of the beam 24.

As a result, it is possible to suppress the spread of the ions in the plasma 18 in the plasma generation container 2 near the opening 4 and the spread of the ion beam 24 extracted from the opening 4 near the extraction electrode system 20. Therefore, the ratio of the ions in the plasma 18 and the ion beam 24 colliding with the structure such as the plasma generation container 2 and the extraction electrode system 20 is reduced, and the ion beam 24 can be efficiently extracted.

Moreover, with the above arrangement, the ground electrode 22
Since a serves also as a shaping means for shaping the magnetic force lines 17 of the magnetic coil 16, it is not necessary to provide a shaping means separately, and therefore, an effect that the structure is simple and compact can be obtained.

The number of electrodes forming the extraction electrode system 20 is not limited to two as in the above example, but 3
There may be more than one. In any case, for making only the most downstream side of the electrodes constituting the extraction electrode system of a magnetic material, the magnetic field lines, without being disturbed by the other electrode, parallel to the beam extraction direction until the most downstream side It is preferable from the viewpoint of withdrawal .

[0017]

As described above, according to the present invention, the electrode on the most downstream side of the plurality of electrodes forming the extraction electrode system is
Since only the magnetic material is made of magnetic material, the magnetic field lines from the magnetic coil are drawn into the most downstream electrode made of this magnetic material and pass through it without being disturbed by other electrodes. As a result, the distribution of the lines of magnetic force from the vicinity of the opening of the plasma generation container to the vicinity of the most downstream electrode of the extraction electrode system approaches parallel to the extraction direction of the ion beam.
As a result, it is possible to suppress the spread of the ions in the plasma in the plasma generation container near the opening and the spread of the ion beam near the extraction electrode system, and to efficiently extract the ion beam. Especially on the most downstream side
Since only the electrode of is made of magnetic material,
Beam is drawn to the most downstream side without being disturbed by other electrodes.
It can be pulled in parallel to the ejection direction, and as a result,
More effectively suppresses the spread of the beam.
Ion beam can be extracted.

Further, in the present invention, since the electrode made of the magnetic material also serves as the shaping means for shaping the magnetic force lines, it is not necessary to provide a shaping means separately, so that the structure is simple and compact.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an ECR type ion source according to an embodiment of the present invention.

FIG. 2 is a diagram showing an outline of magnetic field line distribution in the ECR type ion source of FIG.

FIG. 3 is a cross-sectional view showing an example of a conventional ECR type ion source.

FIG. 4 is a diagram showing an outline of magnetic field line distribution in the ECR type ion source of FIG.

[Explanation of symbols]

 2 Plasma generation container 4 Opening part 6 Waveguide 12 Gas introduction pipe 16 Magnetic coil 17 Magnetic field line 18 Plasma 20 Extraction electrode system 21 Suppression electrode 22a Ground electrode 24 Ion beam

Claims (1)

(57) [Claims] 1. A plasma producing container for producing a plasma, into which microwaves and gas are introduced, a magnetic coil for producing a magnetic field in the direction of extracting an ion beam in the plasma producing container, and the plasma producing container. be provided in the vicinity of the outside of the opening, the ECR ion source and a lead-out electrode system to draw an ion beam from the plasma in the plasma generating vessel by the action of an electric field composed of a plurality of electrodes, the extraction electrode system An ECR type ion source characterized in that only the most downstream electrode of a plurality of constituent electrodes is made of a magnetic material.