JPH0778582A - Ion source device - Google Patents

Abstract

PURPOSE:To provide an ion source device which can convey a high density plasma even with a small electron releasing aperture by furnishing a magnetic field forming means which generates a magnetic field in the axial direction for the electron releasing aperture. CONSTITUTION:An ion source device is formed from a plasma cathode 20 as electron source to generate electron by means of plasma production with high frequency discharging, a main plasma chamber 2 in which electrons are supplied from an electron releasing aperture 30 formed in a lid plate 27 for the cathode 20 and confines the main plasma 26 produced by DC discharging, and extaction device 4 which extracts ion beam from the main plasma 26. Between a lid plate 13 and insulation 15, a magnetic field forming means 31 is provided which is composed of a lid plate 29 made of ferromagnetic material and a ring-shaped magnetic field generating means 28 consisting of electromagnetic coil arranged in the peripheral part on the lid plate 27, and a magnetic field in the axial direction of approx, several hundreds thouthands of G's is produced on the axis of an electron aperture 30 by the magnetic circuit configured with the lid plates 27, 29 and magnetic field generating means 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source device using a microwave plasma cathode (hereinafter referred to as MP cathode) as an electron emission source.

[0002]

2. Description of the Related Art A conventional MP cathode type ion source device is
Since plasma generated by microwave discharge is used as an electron source and a thermoelectron emitting material such as W filament is not used, continuous operation can be performed for a long time even with a reactive gas such as oxygen.

Part 1 of this MP cathode type ion source device
FIG. 8 showing an example will be described. In the figure, 1 is a non-magnetic metal main housing, 2 is a main plasma chamber formed by the main housing 1, 3 is an opening formed on both sides of the main housing 1, and 4 is one opening 3 Is an ion beam extraction electrode attached to the first electrode 5, the second electrode 6, and the third electrode 7 having different potentials. 8 is an insulator interposed between the flange of the main housing 1 and each of the electrodes 5, 6, 7;
Is a permanent magnet or electromagnet for generating a cylindrical magnetic field provided outside the main housing 1, that is, a cusp magnetic field.

Reference numeral 10 is a sub-casing made of a non-magnetic metal material, and 1
1 is a sub-plasma chamber formed by the sub-housing 10, 12,
13 is a cover plate made of a ferromagnetic metal material on both sides of the sub-casing 10, 14 is an electron emission hole in the center of the cover plate 15, 15 is an insulator between the sub-casing 10 and the main casing 1, 16 is the sub-plasma chamber 11 It is an inlet for gas.

Reference numeral 17 is a coaxial cable for introducing microwaves,
18 is an antenna at the tip of the coaxial cable 17, 19 is an annular permanent magnet or electromagnet provided outside the sub-casing 10, forms a magnetic circuit with the lid plates 12 and 13, and an electron cyclotron near the antenna 18. Generate a magnetic field above the resonance (ECR) condition. Reference numeral 20 is a sub-casing 10, a sub-plasma chamber 11, lid plates 12 and 13, an electron emission hole 14, an inlet 1.
6, an MP cathode composed of a coaxial cable 17, an antenna 18, and a magnet 19.

Reference numeral 21 denotes a discharge power source, the anode of which is the main housing 1.
In addition, the cathode is connected to the first electrode 5 via the cover plate 11 and the resistor 22 having a high resistance value, and the main casing 1 is set to the anode potential and the cover plate 12 is set to the cathode potential. An accelerating power source 23 has an anode connected to the anode of the discharge power source 21, a cathode grounded, and an accelerating voltage applied to the first electrode 5. A deceleration power source 24 applies a negative voltage to the second electrode 6.

The sub-casing 10 is held at the cathode potential of the cathode of the discharge power source 21, and the tip of the antenna 18 is provided close to the wall surface of the sub-plasma chamber 11 so that microwave discharge can be easily caused. There is. Next, gas is supplied from the inlet 16 and the coaxial cable 1 is supplied to the sub plasma chamber 11.
7. When microwave is introduced through the antenna 18,
Even if the sub-plasma chamber 11 is not formed in the microwave cavity condition, microwave discharge is easily generated by the high electric field between the tip of the antenna 18 and the wall surface of the sub-plasma chamber 11, and the inlet 16 The gas from is ionized to generate the sub-plasma 25.

Since the main plasma chamber 2 is biased to a higher potential than the sub-plasma chamber 11 by the discharge power source 21, the electrons ionized by the generation of the sub-plasma 25 pass through the electron emission hole 14 and the main plasma chamber 2 In the main plasma chamber 2, a DC discharge is continued by the supplied electrons, and the ionized gas such as the rare gas in the main plasma chamber 2 is ionized to generate the main plasma 26. Next, the main plasma 2 generated by the beam extraction action of the extraction electrode 3
Ions become an ion beam from 6 and are led out to a sputtering chamber or the like.

In the case of the above device, the output is proportional to the amount of electron emission from the MP cathode 20, and therefore the amount of electron emission must be increased in order to increase the current. On the other hand, M
Electrons from the P cathode 20 are emitted from the electron emission hole 1 of the cover plate 13.
It is supplied to the inside of the main plasma chamber 2 through 4 and the electron emission amount is limited by the size of the electron emission hole 14.
Further, the electrons are generated by the sub plasma 25 and the main plasma 26.
The electron emission amount is determined by the density of the sub-plasma 25, the potential difference between the plasmas 25 and 26, the area of the sheath portion, etc. Therefore, in order to increase the electron emission amount, measures such as increasing the hole diameter of the emission hole 14 and increasing the number of holes are taken.

[0010]

In the above apparatus, when the pore size is increased, the neutral gas in the MP cathode 20 flows out, causing a decrease in gas pressure, and the generation of the high density sub-plasma 25 can be stably maintained. In addition, there is a problem that a larger gas supply amount is required to keep the gas pressure constant.

On the other hand, when the number of holes is increased, as shown in FIG. 9, the cover plate 13 has the same potential as the sub-casing 10 and the magnetic circuit is closed in the sub-plasma chamber 11, so that the sub-plasma is closed. 25 is the main plasma 26 due to the lid plate 13.
On the other hand, since the electrons are accelerated to be supplied to the main plasma chamber 2 in the sheath portion between the plasmas 25 and 26 formed through the electron emission holes 14 because they are shielded to some extent, the number of holes is increased and the diameter of the holes is increased. If the gas conductance is narrowed down and the outflow of the neutral gas is suppressed, the direct current electric field from the main plasma 26 is less likely to be applied, and the formation area of the sheath portion which is the electron emission surface is substantially reduced. There is a problem that the release amount is reduced. In consideration of the above points, the present invention provides an ion source device capable of easily increasing the electron emission amount without increasing the supply gas amount, preventing the device from increasing in size, and reducing the formation area of the sheath portion. The purpose is to do.

[0012]

In order to solve the above-mentioned problems, the present invention is formed on a microwave plasma cathode as an electron emission source for generating electrons by plasma generation of microwave discharge, and a lid plate of the cathode. An ion source having a main plasma chamber for confining a main plasma generated by a direct current discharge by supplying electrons from an electron emission hole, and an extraction electrode provided at a position facing a cathode of the main plasma chamber to extract an ion beam from the main plasma The apparatus is provided with magnetic field forming means for forming a magnetic field in the electron emission hole in the axial direction. Further, the electron emission hole is provided with a DC electric field forming means for forming a DC electric field.

[0013]

In the ion source device of the present invention configured as described above, the magnetic field forming means for forming a magnetic field in the axial direction is provided in the electron emission hole, so that effective plasma confinement is performed in the vicinity of the electron emission hole. , Even if the electron emission holes are made small, high-density plasma is transported, the formation area of the sheath portion between both plasmas on the main plasma chamber side of the lid plate is not reduced, and a sufficient electric field for electron emission is applied. Without increasing the amount of supply gas, the device is prevented from being upsized and electrons are easily emitted. Further, since the direct-current electric field forming means for forming a direct-current electric field is provided in the electron emission hole, it has the same operation as described above.

[0014]

EXAMPLES Examples will be described with reference to FIGS. 1 to 7. In these figures, the same symbols as those in FIGS. 8 and 9 indicate the same or corresponding ones. First, in FIG. 1 showing the first embodiment, 27 is a cover plate made of a ferromagnetic material,
Reference numeral 28 denotes an annular magnetic field generating means composed of an electromagnetic coil or a permanent magnet, and is arranged on the peripheral edge of the cover plate 27.
Reference numeral 29 is a lid plate made of a ferromagnetic material, and the magnetic field generating means 2
The cover plate 27 is attached to the peripheral edge of the cover plate 27 so as to cover 8. Three
Reference numeral 0 is an electron emission hole formed so as to be narrowed down to a position communicating with the electron emission hole 14 of the lid plates 27 and 29.

Reference numeral 31 denotes lid plates 27 and 29, magnetic field generating means 2
8, a magnetic field forming means composed of electron emission holes 30, which is arranged between the cover plate 13 and the insulator 15, and has cover plates 27, 29,
An axial magnetic field of about several hundred to several kG is formed on the axes of the electron emission holes 14 and 30 by the magnetic circuit composed of the magnetic field generating means 28.

The sub-plasma 25 is effectively confined in the path of the electron emission holes 14 and 30 by the axial magnetic field of the magnetic field forming means 31 and the DC electric field of the discharge power source 21, and efficient electron emission is achieved. It will be possible.

Next, FIG. 2 showing the second embodiment is different from FIG. 1 in that a lid plate 32 in which the lid plate 13 and the lid plate 29 are made of the same member is arranged. Similarly, efficient electron emission becomes possible.

Next, in FIG. 3 showing the third embodiment, 3
3 is between the lid plate 13 and the lid plate 29, and between the lid plate 29 and the lid plate 27.
An insulator interposed between the electron emission holes 14 and 3;
0 is a DC power supply that forms a DC electric field, and the negative electrode is the cover plate 1
2, the positive electrode is connected to the cover plate 29, the cover plate 27, and the negative electrode of the discharge power source 21 via the resistor 35. 36 includes a DC power source 34 and a resistor 35, and has electron emission holes 14 and 3
It is a DC electric field forming means for forming a DC electric field at 0.

The DC power source 34 is used to control the sub-casing 10.
Has a negative potential with respect to the lid plate 27, and the electron emission holes 14,
In the vicinity of 30, a DC electric field is applied, and the resistance 35 causes the cover plate 29 to move to the sub-casing 10 and the cover plate 27 during operation.
By taking an intermediate potential between and, and effectively confining the magnetic field and the electric field, plasma with a higher density is emitted from the electron emission holes 14 and 30, and more efficient electron emission becomes possible.

Next, FIG. 4 showing the fourth embodiment is different from FIG. 3 in that the insulator 3 between the cover plate 13 and the cover plate 29 is different.
3 and the resistor 35 are omitted, and the sub-casing 10 and the cover plate 29 have the same potential.

Then, as shown in FIG. 5, the plasma is effectively confined in the vicinity of the electron emission holes 14 and 30 by the magnetic field generated by the magnetic circuit of the magnetic field forming means 31 and the electric field generated by the DC power source 34, so that a narrow electron is generated. High-density plasma is emitted from the inside of the emission hole 30, and a sheath portion between the plasmas 25 and 26 is formed on the side of the main plasma chamber 2 of the lid plate 27, which facilitates electron emission and reduces the electron emission hole 30 having a small hole diameter. However, a large current electron emission is possible.

Next, FIG. 6 showing the fifth embodiment is different from FIG. 4 in that a lid plate 37 in which the lid plate 13 and the lid plate 29 are made of the same member is arranged. Similarly, high-current electron emission is possible.

Next, FIG. 7 showing the sixth embodiment is different from FIG. 6 in that the DC power supply 34 is omitted and the discharge power supply 2 is omitted.
The positive electrode of No. 1 is connected to the cover plate 27 via the resistor 37, and the potential of the cover plate 27 is set by the resistor 38.
Since the intermediate potential between the main casing 1 and the main casing 1 is maintained, the same effects as those in FIGS. 3, 4, and 6 can be obtained without adding a new power source, and the device configuration can be simplified.

Next, the experimental results will be described. In the configuration shown in FIGS. 4 and 6, the hole diameter of the electron emission hole 30 is φ.
The maximum electron emission amount Iee was measured by applying an axial magnetic field of about 3 kG at the center of the electron emission hole 30 and supplying oxygen gas at 1/2 or less of the normal amount, and supplying the oxygen gas at 2 mm or less.

On the other hand, without using the magnetic field forming means 32 and the DC electric field forming means 36, the hole diameter of the electron emission hole 14 is φ4 mm,
φ2 mm, oxygen gas supplied, maximum electron emission amount Ie
e was measured.

As a result, in the former case, the hole diameter φ2 mm, the oxygen gas flow rate Q = 1.2 cc / min, and the Iee = 1.15.
A, and no decrease in the amount of electron emission due to the decrease in the opening area of the electron emission hole was observed. However, in the latter case, when the hole diameter is 4 mm, Q = 2.5 cc / min and Iee =
Q = 1.2 cc / mi when 1.18 A and hole diameter φ2 mm
Iee = 0.42A for n, and the electron emission amount also decreases as the opening area of the electron emission hole decreases. In this way, the hole diameter of the electron emission hole 30 is reduced and the gas flow rate is reduced to 1 /
Even if it is 2 or less, the electron emission amount hardly changes, and the gas efficiency can be greatly improved.

[0027]

Since the present invention is constructed as described above, it has the following effects. Since the ion source device of the present invention is provided with the magnetic field forming means 31 for forming a magnetic field in the electron emission hole 30 in the axial direction, effective plasma confinement is performed in the vicinity of the electron emission hole 30 to reduce the electron emission hole 30. Even if high density plasma can be transported, both plasmas 2 on the main plasma chamber side of the lid plate 27 can be transported.
It is possible to sufficiently apply an electric field for electron emission without reducing the formation area of the sheath portion between 5 and 26.
It is possible to prevent the device from increasing in size and facilitate electron emission without increasing the amount of supply gas. Further, since the DC electric field forming means 36 for forming a DC electric field is provided in the electron emission hole 30, the same effect as described above is obtained.

[Brief description of drawings]

FIG. 1 is a cut front view of a first embodiment of the present invention.

FIG. 2 is a cut front view of a second embodiment of the present invention.

FIG. 3 is a cut front view of a third embodiment of the present invention.

FIG. 4 is a cut front view of a fourth embodiment of the present invention.

FIG. 5 is a partial operation state diagram of FIG. 4;

FIG. 6 is a cut front view of a fifth embodiment of the present invention.

FIG. 7 is a cut front view of a sixth embodiment of the present invention.

FIG. 8 is a cut front view of a conventional example.

FIG. 9 is a partial operation state diagram of FIG. 8;

[Explanation of symbols]

 2 Main Plasma Chamber 4 Extraction Electrode 14 Electron Emission Hole 20 Microwave Plasma Cathode 26 Main Plasma 27 Cover Plate 30 Electron Emission Hole 31 Magnetic Field Forming Means 36 Electric Field Forming Means

[Procedure amendment]

[Submission date] September 19, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Ion source device

[Claims]

Detailed Description of the Invention

[0001]

The present invention relates to relates to an ion source device using the Purazumaka <br/> saw de generating electrons by high-frequency discharge such as a microwave discharge in the electron emission source.

[0002]

2. Description of the Related Art A conventional plasma cathode type ion source device of this kind uses a plasma generated by a high frequency discharge such as a microwave discharge as an electron source and does not use a thermionic emission material such as a W filament, and therefore a reactive gas such as oxygen. Also, continuous operation for a long time is possible.

An example of this plasma cathode type ion source device will be described with reference to FIG. The figure shows a micro
Microwave plasma generator that generates electrons by microwave discharge
Mode (hereinafter referred to as MP cathode) is used.
In the figure , 1 is a non-magnetic metallic main casing, 2 is a main plasma chamber formed by the main casing 1, 3 is an opening formed on both sides of the main casing 1, and 4 is one opening 3 The attached ion beam extraction electrode, which has a different potential
It is composed of an electrode 5, a second electrode 6, and a third electrode 7.
8 flange and is an insulator interposed between the electrodes 5, 6 and 7 of the main casing 1, 9 is a permanent magnet or an electromagnet for mosquito spray field generator provided outside of the main casing 1.

Reference numeral 10 is a sub-casing made of a non-magnetic metal material, and 1
1 is a sub-plasma chamber formed by the sub-housing 10, 12,
13 is a cover plate made of a ferromagnetic metal material on both sides of the sub-casing 10, 14 is an electron emission hole in the center of the cover plate 15, 15 is an insulator between the sub-casing 10 and the main casing 1, 16 is the sub-plasma chamber 11 It is an inlet for gas.

Reference numeral 17 is a coaxial cable for introducing microwaves,
18 is an antenna at the tip of the coaxial cable 17, 19 is an annular permanent magnet or electromagnet provided outside the sub-casing 10, forms a magnetic circuit with the lid plates 12 and 13, and an electron cyclotron near the antenna 18. Generate a magnetic field above the resonance (ECR) condition. Reference numeral 20 is a sub-casing 10, a sub-plasma chamber 11, lid plates 12 and 13, an electron emission hole 14, an inlet 1.
6, an MP cathode composed of a coaxial cable 17, an antenna 18, and a magnet 19.

Reference numeral 21 denotes a discharge power source, the anode of which is the main housing 1.
In addition, the cathode is connected to the first electrode 5 via the cover plate 11 and the resistor 22 having a high resistance value, and the main casing 1 is set to the anode potential and the cover plate 12 is set to the cathode potential. An accelerating power source 23 has an anode connected to the anode of the discharge power source 21, a cathode grounded, and an accelerating voltage applied to the first electrode 5. A deceleration power source 24 applies a negative voltage to the second electrode 6.

The sub-casing 10 is held at the cathode potential of the cathode of the discharge power source 21, and the tip of the antenna 18 is provided close to the wall surface of the sub-plasma chamber 11 so that microwave discharge can be easily caused. There is. Next, gas is supplied from the inlet 16 and the coaxial cable 1 is supplied to the sub plasma chamber 11.
7. When microwave is introduced through the antenna 18,
Even if the sub-plasma chamber 11 is not formed in the microwave cavity condition, microwave discharge is easily generated by the high electric field between the tip of the antenna 18 and the wall surface of the sub-plasma chamber 11, and the inlet 16 The gas from is ionized to generate the sub-plasma 25.

Since the main plasma chamber 2 is biased to a higher potential than the sub-plasma chamber 11 by the discharge power source 21, the electrons ionized by the generation of the sub-plasma 25 pass through the electron emission hole 14 and the main plasma chamber 2 In the main plasma chamber 2, a DC discharge is continued by the supplied electrons, and the ionized gas such as the rare gas in the main plasma chamber 2 is ionized to generate the main plasma 26. Next, the main plasma 2 generated by the beam extraction action of the extraction electrode 3
Ions become an ion beam from 6 and are led out to a sputtering chamber or the like.

In the case of the above device, the output is proportional to the amount of electron emission from the MP cathode 20, and therefore the amount of electron emission must be increased in order to increase the current. On the other hand, M
Electrons from the P cathode 20 are emitted from the electron emission hole 1 of the cover plate 13.
It is supplied to the inside of the main plasma chamber 2 through 4 and the electron emission amount is limited by the size of the electron emission hole 14.
Further, the electrons are generated by the sub plasma 25 and the main plasma 26.
The electron emission amount is determined by the density of the sub-plasma 25, the potential difference between the plasmas 25 and 26, the area of the sheath portion, etc. Therefore, in order to increase the electron emission amount, measures such as increasing the hole diameter of the emission hole 14 and increasing the number of holes are taken.

[0010]

In the above apparatus, when the pore size is increased, the neutral gas in the MP cathode 20 flows out, causing a decrease in gas pressure, and the generation of the high density sub-plasma 25 can be stably maintained. In addition, there is a problem that a larger gas supply amount is required to keep the gas pressure constant.

On the other hand, when the number of holes is increased, as shown in FIG. 9, the cover plate 13 has the same potential as the sub-casing 10 and the magnetic circuit is closed in the sub-plasma chamber 11, so that the sub-plasma is closed. 25 is the main plasma 26 due to the lid plate 13.
To have been somewhat shielded, it accelerated electrons in the sheath portion of both plasma between 25 and 26 formed through the electron emission holes 14, to be supplied to the main plasma chamber 2, increasing the number of holes, on the other hand Electron emission by narrowing down the hole diameter
If the gas conductance per outlet is reduced, the direct current electric field from the main plasma 26 is less likely to be applied even if the outflow of neutral gas is suppressed, and the formation area of the sheath portion, which is the electron emission surface, is substantially reduced. Therefore, there is a problem that the amount of electron emission is reduced. In consideration of the above points, the present invention prevents an increase in the size of the device without increasing the supply gas amount, and does not reduce the formation area of the sheath portion.
An object is to provide an ion source device that easily increases the amount of electron emission.

[0012]

In order to solve the above problems SUMMARY OF THE INVENTION The present invention provides a flop plasma cathode as an electron emission source for generating electrons by plasma generating high-frequency discharge, formed on the cathode of the cover plate electron In an ion source device equipped with a main plasma chamber for confining a main plasma generated by direct current discharge by supplying electrons from an emission hole and an extraction electrode for extracting an ion beam from the main plasma, an axial magnetic field is formed in the electron emission hole. It is provided with a magnetic field forming means. Further, the electron emission hole is provided with a DC electric field forming means for forming a DC electric field.

[0013]

In the ion source device of the present invention configured as described above, the magnetic field forming means for forming a magnetic field in the axial direction is provided in the electron emission hole, so that effective plasma confinement is performed in the vicinity of the electron emission hole. , Even if the electron emission holes are made small, high-density plasma is transported, the formation area of the sheath portion between both plasmas on the main plasma chamber side of the lid plate is not reduced, and a sufficient electric field for electron emission is applied. Without increasing the amount of supply gas, the device is prevented from being upsized and electrons are easily emitted. Further, since the direct-current electric field forming means for forming a direct-current electric field is provided in the electron emission hole, it has the same operation as described above.

[0014]

EXAMPLES Examples will be described with reference to FIGS. 1 to 7. In these figures, the same symbols as those in FIGS. 8 and 9 indicate the same or corresponding ones. First, in FIG. 1 showing the first embodiment, 27 is a cover plate made of a ferromagnetic material,
28 is a magnetic field generating means of the electromagnetic coil or Ranaru ring,
It is arranged on the peripheral edge of the cover plate 27. Reference numeral 29 is a lid plate made of a ferromagnetic material, and is attached to the peripheral portion of the lid plate 27 so as to cover the magnetic field generating means 28. Not shown
However, the magnetic field generating means may be a permanent magnet. Thirty
Is an electron emission hole formed in the cover plate 27 , and 39 is a cover plate 29.
Narrow down to a position that communicates with the electron emission hole 30
It is the formed orifice.

Reference numeral 31 denotes lid plates 27 and 29, magnetic field generating means 2
8, a magnetic field forming means composed of electron emission holes 30, which is arranged between the cover plate 13 and the insulator 15, and has cover plates 27, 29,
The magnetic circuit comprising a magnetic field generating means 28, an electronic
An axial magnetic field of about several hundred to several kG is formed on the axis of the emission hole 30 .

The sub-plasma 25 is effectively confined in the path of the electron emission hole 30 by the magnetic field in the axial direction by the magnetic field forming means 31 and the DC electric field by the discharge power source 21 to enable efficient electron emission. Become.

Next, FIG. 2 showing the second embodiment is different from FIG. 1 in that a lid plate 32 in which the lid plate 13 and the lid plate 29 are made of the same member is arranged. Similarly, efficient electron emission becomes possible.

Next, in FIG. 3 showing the third embodiment, 3
3 is between the lid plate 13 and the lid plate 29, and between the lid plate 29 and the lid plate 27.
And an insulator interposed between the sub plasma chamber 11 and
A direct current power source that forms a direct current electric field in the electron emission hole 30 ,
The negative electrode is connected to the cover plate 12, and the positive electrode is connected to the cover plate 29, the cover plate 27, and the negative electrode of the discharge power supply 21 via the resistor 35. 36 comprises a DC power source 34, resistor 35, electronic release
It is a DC electric field forming means for forming a DC electric field in the exit hole 30 .

The DC power source 34 is used to control the sub-casing 10.
Has a negative potential with respect to the lid plate 27, a DC electric field is applied in the vicinity of the electron emission hole 30 , and the resistance 35
As a result, the cover plate 29 takes an intermediate potential between the sub-casing 10 and the cover plate 27 during operation, and the effective confinement of the magnetic field and the electric field causes the high-density plasma to be emitted from the electron emission holes 30 to further improve the efficiency. Good electron emission is possible.

Next, FIG. 4 showing the fourth embodiment is different from FIG. 3 in that the insulator 3 between the cover plate 13 and the cover plate 29 is different.
3 and the resistor 35 are omitted, and the sub-casing 10 and the cover plate 29 have the same potential.

Then, as shown in FIG. 5, the plasma is effectively confined in the vicinity of the electron emission hole 30 by the magnetic field generated by the magnetic circuit of the magnetic field forming means 31 and the electric field generated by the DC power source 34, so that a narrow electron emission hole is formed. High-density plasma is emitted from inside 30, and a sheath portion between the plasmas 25 and 26 is formed on the main plasma chamber 2 side of the lid plate 27.
Electrons can be easily emitted, and a large amount of electrons can be emitted even in the electron emission hole 30 having a small hole diameter.

Next, FIG. 6 showing the fifth embodiment is different from FIG. 4 in that a lid plate 37 in which the lid plate 13 and the lid plate 29 are made of the same member is arranged. Similarly, high-current electron emission is possible.

Next, FIG. 7 showing the sixth embodiment is different from FIG. 6 in that the DC power supply 34 is omitted and the discharge power supply 2 is omitted.
The positive electrode of No. 1 is connected to the cover plate 27 via the resistor 38, and the potential of the cover plate 27 is set by the resistor 38 to the sub-casing 10.
Since the intermediate potential between the main casing 1 and the main casing 1 is maintained, the same effects as those in FIGS. 3, 4, and 6 can be obtained without adding a new power source, and the device configuration can be simplified. In addition, each embodiment is
For MP cathode using microwave discharge by Tena
However, the plasma using general high frequency discharge etc.
The same effect can be obtained with a cathode.

Next, the experimental results will be described. In the configuration shown in FIGS. 4 and 6, the hole diameter of the electron emission hole 30 is φ.
The maximum electron emission amount Iee was measured by applying an axial magnetic field of about 3 kG at the center of the electron emission hole 30 and supplying oxygen gas at 1/2 or less of the normal amount, and supplying the oxygen gas at 2 mm or less.

On the other hand, without using the magnetic field forming means 32 and the DC electric field forming means 36, the hole diameter of the electron emission hole 14 is φ4 mm,
φ2 mm, oxygen gas supplied, maximum electron emission amount Ie
e was measured.

As a result, in the former case, the hole diameter φ2 mm, the oxygen gas flow rate Q = 1.2 cc / min, and the Iee = 1.15.
A, and no decrease in the amount of electron emission due to the decrease in the opening area of the electron emission hole was observed. However, in the latter case, when the hole diameter is 4 mm, Q = 2.5 cc / min and Iee =
Q = 1.2 cc / mi when 1.18 A and hole diameter φ2 mm
Iee = 0.42A for n, and the electron emission amount also decreases as the opening area of the electron emission hole decreases. In this way, the hole diameter of the electron emission hole 30 is reduced and the gas flow rate is reduced to 1 /
Even if it is 2 or less, the electron emission amount hardly changes, and the gas efficiency can be greatly improved.

[0027]

Since the present invention is constructed as described above, it has the following effects. Since the ion source device of the present invention is provided with the magnetic field forming means 31 for forming a magnetic field in the electron emission hole 30 in the axial direction, effective plasma confinement is performed in the vicinity of the electron emission hole 30 to reduce the electron emission hole 30. Even if high density plasma can be transported, both plasmas 2 on the main plasma chamber side of the lid plate 27 can be transported.
It is possible to sufficiently apply an electric field for electron emission without reducing the formation area of the sheath portion between 5 and 26.
It is possible to prevent the device from increasing in size and facilitate electron emission without increasing the amount of supply gas. Further, since the DC electric field forming means 36 for forming a DC electric field is provided in the electron emission hole 30, the same effect as described above is obtained.

[Brief description of drawings]

FIG. 1 is a cut front view of a first embodiment of the present invention.

FIG. 2 is a cut front view of a second embodiment of the present invention.

FIG. 3 is a cut front view of a third embodiment of the present invention.

FIG. 4 is a cut front view of a fourth embodiment of the present invention.

FIG. 5 is a partial operation state diagram of FIG. 4;

FIG. 6 is a cut front view of a fifth embodiment of the present invention.

FIG. 7 is a cut front view of a sixth embodiment of the present invention.

FIG. 8 is a cut front view of a conventional example.

FIG. 9 is a partial operation state diagram of FIG. 8;

[Description of Reference Signs ] 2 Main Plasma Chamber 4 Extraction Electrode 20 Microwave Plasma Cathode 26 Main Plasma 27 Cover Plate 30 Electron Emission Hole 31 Magnetic Field Forming Means 36 Electric Field Forming Means

[Procedure 3]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

[Figure 9]

[Figure 8]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuo Matsubara 47 Umezu Takaune-cho, Ukyo-ku, Kyoto Nissin Electric Co., Ltd.

Claims (2)

[Claims] 1. A microwave plasma cathode as an electron emission source that generates electrons by plasma generation of microwave discharge, and the electrons are supplied from an electron emission hole formed in a cover plate of the cathode and generated by direct current discharge. In an ion source device comprising a main plasma chamber for confining a main plasma, and an extraction electrode provided at a position facing the cathode of the main plasma chamber and extracting an ion beam from the main plasma, an axial direction is provided in the electron emission hole. An ion source device comprising magnetic field forming means for forming a magnetic field. 2. A microwave plasma cathode as an electron emission source that generates electrons by plasma generation of microwave discharge, and the electrons are supplied from an electron emission hole formed in a lid plate of the cathode to generate by DC discharge. In a main plasma chamber for confining the main plasma, and an extraction electrode provided at a position facing the cathode of the main plasma chamber for extracting an ion beam from the main plasma, a DC electric field is applied to the electron emission hole. An ion source device provided with a DC electric field forming means for forming.