JPH0845459A - Ion source device - Google Patents

Abstract

PURPOSE:To adopt just one magnetic application means so as to downsize and lighten an ion source device by combining a microwave plasma cathode, a main plasma chamber, an ion electrode, and a magnetic application means in a specified condition. CONSTITUTION:An ion source device dispense with a permanent magnet and an electrode coil but has an electrode coil 36, and dispenses with an inner lid but is provided with an intermediate plate 37 made from a ferromagnetic body metal material and a cylindrical body 38 instead of an intermediate plate. Three apertures 39 equivalent to apertures are formed in the intermediate plate 37. A magnetic field application means is formed by a solenoid coil 36, an outer lid 3, a base lid 14, the intermediate plate 37, and the cylindrical body 38, this magnetic field application means forms a microwave plasma generation magnetic field by the solenoid coil 36 and the first magnetic circuit of the outer lid 3 and the base lid 14, the microwave plasma generation magnetic field is formed by the first magnetic circuit, and an axial magnetic field is formed in the adjacent to each electron emission hole 15 by the solenoid coil 36 parallel to the first magnetic circuit, and the second magnetic circuit of the outer lid 3, the intermediate plate 37, and the base lid 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a microwave plasma cathode (hereinafter referred to as an MP cathode) as an electron supply source.
Relates to an ion source device.

[0002]

2. Description of the Related Art Conventionally, this type of MP cathode type ion source device is constructed as shown in FIG. 3, in which 1 is a sub-housing made of a non-magnetic metal material and 2 is a sub-housing 1. 3 and 4 are outer and inner lids made of a ferromagnetic metal material on both sides of the sub-casing 1, 5 is a gas inlet of the sub-plasma chamber 2 formed in the outer lid 3, and 6 is a tip. The parts are three coaxial cables for microwave introduction, which are inserted into the sub-plasma chamber 2 through the outer lid 3, and 7 is an antenna at the tip of each coaxial cable 6.

Reference numeral 8 is an annular permanent magnet provided outside the sub-casing 1 and generates a magnetic field in the sub-plasma chamber 2 which is above the electron cyclotron resonance (ECR) condition. Reference numeral 9 denotes three openings formed in the inner lid 4 corresponding to the antenna 7. 1
Reference numeral 0 denotes a flange-shaped intermediate plate joined to the inner lid 4, which is made of a ferromagnetic metal material. Reference numeral 11 denotes three openings of the intermediate plate 10 overlapping the respective openings 9, reference numeral 12 denotes an extension portion of the peripheral edge of the intermediate plate 10, and reference numeral 13 denotes an electromagnetic coil for magnetic field generation provided at the peripheral edge of the intermediate plate 10. .

Reference numeral 14 is a base lid made of a ferromagnetic metal material provided with a gap between the intermediate plate 10 and the electromagnetic coil 13, and 15 is an electron emission hole formed in the base lid 15. Polymerize. Reference numeral 16 denotes an MP cathode formed by the sub-casing 1, the sub-plasma chamber 2, the outer lid 3, the inner lid 4, the gas inlet 5, the antenna 7, the permanent magnet 8, the intermediate plate 10, the electromagnetic coil 13, the base lid 14 and the like. is there.

Reference numeral 17 is a main housing made of a non-magnetic metal, 18 is a main plasma chamber formed by the main housing 17, 19, 20
Is an opening formed on both sides of the main housing 17, 21 is an insulator interposed between the one opening 19 and the base lid 14, and 22 is an ion beam extraction electrode attached to the other opening 20. The first electrode 23, the second electrode 24, and the third electrode 25 are arranged in this order from the opening 20. 26 is an insulator interposed between the opening 20 and each electrode 23, 24, 25,
Reference numeral 27 is a cylindrical permanent magnet or electromagnet provided outside the main casing 17 for generating a cusp magnetic field.

Reference numeral 28 denotes a cathode power source having a negative electrode connected to the outer lid 3, and a positive electrode connected to the base lid 14. Reference numeral 29 denotes a discharge power source whose negative electrode is connected to the positive electrode of the cathode power source 28, and the positive electrode is connected to the main housing 17. Reference numeral 30 is an accelerating power source whose positive electrode is connected to the main housing 17, and whose negative electrode is grounded. 31 is the negative electrode of the discharge power supply 29 and the first power supply 2
3 is a resistor provided between the second electrode and the second electrode 24.
Is a deceleration power supply connected to and the positive electrode is grounded. The third electrode 25 is grounded.

In the MP cathode 16, a magnetic circuit is formed by the permanent magnet 8 and the outer lid 3 and the inner lid 4 made of a ferromagnetic metal material, and a plasma generating magnetic field above the ECR condition is formed near the antenna 7. ing. Therefore,
By supplying gas to the sub plasma chamber 2 from the gas inlet port 5 and supplying microwaves to the sub plasma chamber 2 from the antenna 7, the supply gas is ionized by the microwave discharge,
The sub plasma 33 is formed.

Further, the intermediate plate 10 and the base cover 14 are made of a ferromagnetic metal material, and when the electromagnetic coil 13 is energized, holes 9, 11 are formed in the vicinity of the electron emission holes 15 as shown by arrow B in the figure. , An axial magnetic field passing through the electron emission hole 15 is formed. Further, a DC electric field between the intermediate plate 10 and the base lid 14 is applied by the cathode power source 28.

By applying the DC electric field and the magnetic field in the axial direction, the high-density plasma is confined in the opening between the intermediate plate 10 and the base cover 14. Due to the confinement of the high-density plasma, the direct plasma voltage is applied from the discharge power supply 29 provided between the main housing 17 and the base lid 14, and the main plasma chamber is passed from the sub-plasma chamber 2 through each electron emission hole 15. Electrons are efficiently supplied into the inside 18 to form the main plasma 34 due to the DC discharge.

Then, the ion extraction action of the ion extraction electrode 22 causes the ion beam 35 from the main plasma 34.
Is withdrawn.

Since this type of MP cathode type ion source device uses plasma generated by microwave discharge as an electron supply source and does not use a thermionic emission material such as a W filament,
There is an advantage that continuous operation can be performed for a long time even with a reactive gas such as oxygen. Moreover, by forming an axial magnetic field in the vicinity of each electron emission hole 15 of the MP cathode 16, high-density plasma is confined and transported in the area of this vicinity, and as a result, the electron emission capability is remarkably increased. improves.

[0012]

In the case of the conventional apparatus of FIG. 3, the first magnetic field applying means of the outer lid 3, the inner lid 4 and the permanent magnet 8 forms the plasma generating magnetic field in the sub plasma chamber 2. , Intermediate plate 10, base cover 14 and electromagnetic coil 1
An axial magnetic field is formed in the vicinity of each electron emission hole 15 by the third magnetic field applying means 3, and each magnetic field applying means is required to form both magnetic fields.

Therefore, it is necessary to provide the first and second magnetic field applying means, and there is a problem that the apparatus becomes very large and heavy. An object of the present invention is to reduce the size and weight of the device by using one magnetic field applying unit.

[0014]

To achieve the above object, in the ion source device of the present invention, an electron emission hole for confining the microwave plasma generating magnetic field and the high density plasma in the sub plasma chamber by the magnetic parallel circuit. One magnetic field applying means for forming an axial magnetic field in the vicinity of

[0015]

In the case of the ion source device of the present invention configured as described above, the magnetic field for microwave plasma generation in the sub-plasma chamber and the axis in the vicinity of the electron emission hole by one magnetic field applying means through the magnetic parallel circuit. A directional magnetic field is formed. for that reason,
Since only one magnetic field applying means is required, the size and weight of the device can be reduced.

[0016]

EXAMPLES Examples will be described with reference to FIGS. 1 and 2. (First Embodiment) First, one embodiment in which an electromagnetic coil is used as the magnetic field applying means will be described with reference to FIG.

In the figure, the same reference numerals as those in FIG. 3 indicate the same or corresponding parts, and the difference from the conventional device is that of FIG.
The permanent magnet 8 and the electromagnetic coil 13 are omitted to provide one electromagnetic coil 36, the inner lid 4 is omitted, and the intermediate plate 37 and the cylindrical body 38 made of a ferromagnetic metal material are provided instead of the intermediate plate 10. is there. The intermediate plate 37 is formed with three openings 39 corresponding to the openings 11 in FIG.

The electromagnetic coil 36, the outer lid 3, the base lid 14, the intermediate plate 37, and the cylindrical body 38 form one magnetic field applying means. The magnetic field applying means includes the electromagnetic coil 36 and the outer lid 3, 3. The first magnetic circuit of the base lid 14 forms a microwave plasma generating magnetic field, and the electromagnetic coil 36 and the outer lid 3, the intermediate plate 37, and the second magnetic circuit of the base lid 14 which are parallel to the first magnetic circuit. , An axial magnetic field is formed in the vicinity of each electron emission hole 15.

That is, a magnetic flux density of 2 to 3 KG or higher is required as the axial magnetic field in the vicinity of the electron emission hole 15, but a relatively weak magnetic field of 875 G or higher is required as the magnetic field for microwave plasma generation. Therefore, the magnetic field applying means forms the both magnetic fields by sharing the electromagnetic coil 36 by the magnetic parallel circuit of the first and second magnetic circuits.

Then, the first magnetic circuit forms a magnetic field above the ECR condition in the vicinity of each antenna 7 of the sub-plasma chamber 2, introduces the gas into the sub-plasma chamber 2 from the gas inlet 5, and then the respective coaxial cables 6 When microwaves are supplied to the sub plasma chamber 2 from each antenna 7 through the antennas 7,
The sub plasma 33 of FIG. 3 is generated in the sub plasma chamber 2.

Further, an axial magnetic field of 2 KG or more is formed in the vicinity of each electron emission hole 15 by the second magnetic circuit. Then, due to the axial magnetic field and the application of the DC electric field from the cathode power source 29 shown in FIG. 3, high-density plasma similar to the conventional device is confined in the vicinity of each electron emission hole 15.

Further, when a DC voltage is applied from the discharge power source 29 shown in FIG. 3, electrons are supplied from the sub-plasma chamber 2 through the electron emission holes 15 into the main plasma chamber 18 shown in FIG. It is formed. An ion beam is extracted from the main plasma 19 by the ion extracting action of the ion extracting electrode 22 shown in FIG.

(Other Embodiment) Next, another embodiment in which a permanent magnet is used as the magnetic field applying means will be described with reference to FIG. In the figure, the same reference numerals as those in FIG. 1 indicate the same or corresponding ones, except that an annular permanent magnet 40 is provided on the surface of the base lid 14 on the side of the sub plasma chamber 2 instead of the electromagnetic coil 36 of FIG. , The intermediate plate 37 and the cylindrical body 38 of FIG.
Instead of the above, an intermediate plate 42 attached to the outer lid 3 via a tubular body 41 is provided.

The cylindrical body 41 and the intermediate plate 42 are made of a ferromagnetic metal material. Further, the intermediate plate 42 is formed with three openings 43 corresponding to the openings 39 in FIG.

Further, a magnetic field adjusting gap is formed between the intermediate plate 42 and the permanent magnet 40. The permanent magnet 40, the outer lid 3, the base lid 14, the cylindrical body 41, and the intermediate plate 42 form one magnetic field applying unit.

This magnetic field applying means forms a microwave plasma generating magnetic field by the permanent magnet 40, the outer lid 3, the base lid 14, and the first magnetic circuit of the cylindrical body 41, and the permanent magnet 40, the base lid 14, and the intermediate plate. An axial magnetic field is formed in the vicinity of each electron emission hole 15 by the second magnetic circuit 42. Therefore,
In the case of this embodiment, the permanent magnet 40 is used to obtain the same effect as that of the first embodiment.

By the way, the permanent magnet 40 may be formed of one annular magnet, or may be formed of a plurality of divided magnet pieces. Further, in the above both embodiments, the case where the three electron emission holes 15 corresponding to the antenna 7 are described, but the number of the antennas 7, the electron emission holes 15 and the like are not limited to the embodiments, and the antenna 7 is not limited. , One electron emission hole 15 may be provided.

[0028]

Since the present invention is configured as described above, it has the following effects. Since the magnetic field for microwave plasma generation in the sub-plasma chamber 2 and the axial magnetic field in the vicinity of the electron emission hole 15 are formed by one magnetic field applying means through the magnetic parallel circuit, only one magnetic field applying means is provided in the apparatus. In addition, the size and weight of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a partial cutaway front view of an embodiment of the present invention.

FIG. 2 is a partial cutaway front view of another embodiment of the present invention.

FIG. 3 is a cut front view of a conventional example.

[Explanation of symbols]

 2 Sub-plasma chamber 15 Electron emission hole 16 MP cathode 18 Main plasma chamber 22 Ion extraction electrode 36 Electromagnetic coil 40 Permanent magnet

Claims (1)

[Claims] 1. A microwave plasma cathode (hereinafter referred to as an MP cathode) for confining high-density plasma near an electron emission hole by using plasma generated in a sub-plasma chamber by microwave discharge as an electron supply source, and from the electron emission hole Ions provided with a main plasma chamber that is supplied with electrons and that generates a main plasma by direct current discharge, and an ion extraction electrode that is provided at a position facing the MP cathode in the main plasma chamber and that extracts an ion beam from the main plasma The source apparatus comprises one magnetic field applying means for forming a magnetic field for microwave plasma generation in the sub-plasma chamber and an axial magnetic field in the vicinity of the electron emission hole for confining the high-density plasma by a magnetic parallel circuit. An ion source device characterized by.