JPH09129151A - Negative ion source device - Google Patents

Abstract

(57) Abstract: Provided is a negative ion source device capable of stably obtaining a large amount of negative ions for a long time without deteriorating the function of a magnetic filter. A cylindrical discharge vessel having a gas introduction port, a microwave introduction port, and an ion emission port, and an ion extraction electrode 2 arranged adjacent to the ion emission port of the discharge vessel,
A voltage applying means 3 for setting the ion extracting electrode and the discharge vessel to predetermined potentials, a microwave introducing means 4 for introducing microwaves into the discharge vessel, and a discharge vessel on the outer peripheral side of the discharge vessel. The solenoid coil 5 is arranged concentrically and has a yoke whose inner peripheral side is open, and is provided on the ion emission port side of the discharge vessel to generate a magnetic field in a direction substantially perpendicular to the direction in which ions are extracted. In the negative ion source device including the magnetic pole pair 9, the magnetic member 7 is arranged on the inner wall surface of the discharge vessel and at the portion facing the yoke end on the ion extraction electrode side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative ion source device, and more particularly to a negative ion source device suitable for use in an ion implantation device or the like.

[0002]

2. Description of the Related Art As an effective measure for mitigating electrostatic charge of a sample at the time of ion implantation using this kind of ion source, for example, "4th Symposium on Advanced Application Technology of Particle Beam" (1993, Tokyo) "Proceedings of the
Fourth Symposium on Beam Engineering of Advanced M
There is a technique of implanting negative ions instead of positive ions, as described in "Aterial Syntheses" (published November 24, 1993), pages 75 to 78. Negative ion source device used in this technique The structure of is generally formed as follows.

That is, a discharge vessel having a gas introduction port and an ion emission port, an ion extraction electrode arranged adjacent to the ion emission port, and the ion extraction electrode and the discharge vessel are respectively brought to predetermined potentials. Voltage applying means to be set,
Permanent magnets arranged near the wall surface of the discharge vessel to form a plasma confining magnetic field, filaments arranged in the discharge vessel, and arc discharge generation for generating arc discharge between the filaments and the discharge vessel. Means and
And a pair of magnetic poles for generating a magnetic field in the discharge vessel in a direction substantially perpendicular to the direction in which the ions are extracted by the ion extracting electrode.

In such a structure, plasma is generated by arc discharge, and negative ions are generated in a low electron temperature region formed in a region surrounded by the magnetic field of the magnetic pole pair and the ion emission port. Negative ions are extracted through the extraction electrode. The magnetic field formed by the pair of magnetic poles and substantially perpendicular to the ion extraction direction is generally called a magnetic filter.

Regarding the mechanism of the negative ion generation, for example, “11th Ion Engineering Symposium“ Ion Source and Applied Technology Based on Ions ”” (1987,
"Proceedings of the Eleventh Sympos"
ium on Ion Sources and Ion-Assisted Technology ”, pages 267 to 276.

Further, in addition to the above configuration, as described in, for example, Japanese Patent Laid-Open No. 63-248037, a gas inlet, a microwave inlet, and an ion outlet are provided instead of the discharge vessel having the above configuration. While comprising a discharge container, in addition to the configuration of the conventional negative ion source device, microwave introducing means for introducing a microwave into the discharge container, a solenoid coil arranged around the discharge container, There has been proposed a configuration including a mesh member disposed in a region inside the discharge container surrounded by a microwave introduction port and a magnetic pole pair.

In the negative ion source device of this structure, instead of the arc discharge between the filament and the discharge vessel, a microwave discharge is generated in the magnetic field generated by the solenoid coil to generate plasma. In addition, the net-like member of the negative ion source device of the present configuration shields the region surrounded by the magnetic filter and the ion emission port from the microwaves incident from the microwave introduction port, and the electrons in the same region by the microwave are shielded. The dissociation of negative ions caused by heating is prevented.

[0008]

In the above-mentioned conventional negative ion source device for generating plasma by arc discharge between the filament and the discharge vessel, the filament is easily worn, and in particular, negative ions of chemically active elements are used. When the ions are obtained, the filament is broken in about several hours, so that there is a problem that the practically required life of the negative ion source device used for the ion implantation device or the like cannot be obtained.

Further, in the above-mentioned conventional negative ion source device which generates plasma by microwave discharge in a magnetic field, the magnetic field generated by the solenoid coil leaks to the magnetic filter region and disturbs the magnetic field in the same region, so that the low electron temperature region is generated. However, there is a problem that the function of the magnetic filter for forming a negative electrode is deteriorated and the amount of negative ions produced is reduced.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a negative ion source device capable of stably obtaining a large amount of negative ions for a long time without deteriorating the function of a magnetic filter. There is.

[0011]

That is, the present invention provides a cylindrical discharge vessel having a gas inlet, a microwave inlet, and an ion outlet, and an ion disposed adjacent to the ion outlet of the discharge vessel. Extraction electrode, voltage applying means for setting the ion extraction electrode and the discharge vessel to predetermined potentials respectively, microwave introduction means for introducing microwaves into the discharge vessel, and discharge on the outer peripheral side of the discharge vessel A solenoid coil that is arranged concentrically with the container and that has a yoke that is open on the inner peripheral side, and a magnetic field that is provided on the ion emission port side of the discharge container and that is substantially perpendicular to the direction in which ions are extracted In a negative ion source device provided with a magnetic pole pair to be generated, on the inner wall surface of the discharge vessel,
In addition, the magnetic member is arranged in a portion facing the yoke end on the side of the ion extracting electrode to achieve the intended purpose.

Further, according to the present invention, an annular magnetic member formed concentrically with the discharge vessel is arranged in the discharge vessel on the upstream side of the magnetic pole pair in the ion extraction direction and near the ion emission port side. It was done. Further, a part of the discharge vessel on the upstream side of the magnetic pole pair in the ion extracting direction and in the vicinity of the ion emitting port side is formed of an annular magnetic member.

Further, according to the present invention, an annular magnetic member is provided concentrically with the discharge vessel in the discharge vessel and on the side of the ion emission port, and the annular magnetic member covers the annular hollow portion. A conductive net-like member is provided. Further, the mesh member is detachably attached to the side wall of the magnetic member. Furthermore, this mesh member is attached to the side wall surface of the ion extracting electrode of the magnetic member.

That is, in the thus-formed negative ion source device, the magnetic substance is arranged in the region inside the discharge vessel surrounded by the microwave introduction port and the magnetic pole pair, so that the magnetic field is generated by the yoke and the magnetic member. Since the circuit is formed,
The magnetic field generated by the solenoid coil is concentratedly distributed inside the yoke and inside the magnetic member. Therefore, the magnetic field inside the discharge vessel among the magnetic fields generated by the solenoid coil passes through the magnetic member and goes through the yoke. Will no longer leak into the area of the magnetic filter,
The magnetic field in the same region generated by the pair of magnetic poles is not disturbed, and therefore the function of the magnetic filter for forming the low electron temperature region is not deteriorated, and therefore a large amount of negative ions can be obtained. Further, microwave discharge can be generated in a stable magnetic field, and plasma can be stably generated for a long time.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 shows the negative ion source device in cross section. The negative ion source device mainly includes a discharge vessel 1, an ion extracting electrode 2, a DC constant voltage power source 3 as a voltage applying means, a microwave introducing means 4, a solenoid coil 5, and a yoke 6 arranged around the solenoid coil. It is composed of an annular magnetic member 7, a conductive mesh member 8 and a pair of permanent magnets 9 which are magnetic pole pairs.

The inside of the discharge vessel 1 is formed into a cylindrical shape,
It has a microwave introduction port 1A at one end, an ion emission port 1B at the other end, and a gas introduction port 1C at the side surface. In addition, as shown in FIG. 2, a cooling water passage 12 is provided on the side surface of the discharge vessel.
Is provided. The pair of permanent magnets 9 which are magnetic pole pairs,
An N pole and an S pole are attached so as to face each other on the outer wall of the side surface portion of the discharge vessel 1 near the ion emission port 1B (see FIG. 2) to form a magnetic filter.

The ion extraction electrode 2 provided on the ion extraction side of the discharge vessel 1 is composed of three electrodes 2A, 2B and 2C having a circular hole in the center thereof, and a flange 10A connected to the discharge vessel 1 respectively. It is fixedly held at 10B and 10C. These flanges 10A, 10B, 10C are
The discharge vessel 1 through the other flange 10D and the insulator 11.
It is connected to the.

In addition, a pair of permanent magnets 13 having N and S poles facing each other across a central circular hole are embedded in the electrode 2B in order to suppress extraction of electrons with negative ions. There is. A cooling water passage 14 is provided on the flange 10B to prevent thermal demagnetization of the permanent magnet 13.

The microwave introducing means 4 includes a microwave oscillator 4A, an isolator 4B, a directional coupler 4C, a choke flange 4D, a rectangular waveguide 4E, and a step converter 4F.
-It is composed of a microwave introduction window 4G. The oscillation frequency of the microwave oscillator 4A is 2.45 GHz. In the microwave introduction window 4G, two quartz plates are used, one for vacuum sealing and one for heat shielding. Resin is inserted into the gap between the solenoid coil 5 and the yoke 6 arranged around the solenoid coil 5 to form an integral mold structure.

The solenoid coil 5 and the yoke 6 are
The carriage 16 is supported on a rail 15 so that it can travel, and two sets are arranged side by side coaxially with the discharge vessel 1. The annular magnetic member 7 is installed in a region between the pair of permanent magnets 9 which are magnetic pole pairs and the microwave introduction port 1A. The material of the annular magnetic member 7 is electromagnetic soft iron plated with chromium.

The conductive mesh member 8 is attached to the annular plate 8A of SUS304 by SUS as shown in FIGS.
A wire 8B of 304 is stretched and is detachably fixed to the annular magnetic member 7 with a screw 8C. Also,
The annular magnetic member 7 is fixed so that the installation position can be adjusted by pressing the headless bolt 7A on the side surface against the inner wall surface of the discharge vessel 1.

The DC constant voltage power supply 3 sets the discharge container 1 and the ion extracting electrode 2 to predetermined potentials, and specifically, as shown in FIG. The DC constant voltage power supplies 3A, 3B and 3C are used to connect between the discharge vessel 1 and the electrode 2A, and between the electrode 2A and the electrode 2B, respectively.
A predetermined voltage is applied between the electrodes 2B and 2C.

The negative ion source device thus formed is
It acts as follows to generate negative ions. That is, the discharge gas is introduced into the discharge vessel 1 that has been evacuated by the vacuum evacuation means (not shown) through the gas introduction port 1C. The microwave power from the microwave oscillator 4A is supplied to the isolator 4B, the directional coupler 4C, the choke flange 4D,
Transmission via the rectangular waveguide 4E, step converter 4F
After being converted into a circular mode by, the magnetic field is introduced into the discharge vessel 1 through the microwave introduction window 4G in substantially parallel to the magnetic field generated by the solenoid coil 5.

In the discharge vessel 1, microwave discharge is generated in the magnetic field generated by the solenoid coil 5, and plasma is generated. By the pair of permanent magnets 9 attached to the outer wall of the side surface of the discharge vessel 1 so that the N pole and the S pole face each other, a magnetic field in the X direction (direction substantially perpendicular to the ion extraction direction) shown in FIGS. 1 and 2 is generated. A magnetic filter is generated to form a magnetic filter, a region of low electron temperature plasma is generated in the space between the magnetic filter and the ion emission port 1B, and negative ions are generated in the region. The generated negative ions are radiated in the Z direction shown in FIG. 1 by the electric field formed by the ion extracting electrode 2.

As described above, since plasma is generated by microwave discharge in a magnetic field without using a filament, negative ions can be stably obtained for a long time. Further, the yoke 6 is arranged around the solenoid coil 5, and the annular magnetic member 7 is arranged in the region between the pair of permanent magnets 9 which are magnetic pole pairs and the microwave introduction port 1A. Since a magnetic circuit is formed by 6 and the annular magnetic member 7, the magnetic field generated by the solenoid coil 5 is applied to the inside of the yoke 6 and the annular magnetic member 7.
Concentrated and distributed inside.

Therefore, as shown by the lines of magnetic force in FIG. 5, of the magnetic field generated by the solenoid coil 5, the discharge vessel 1
The magnetic field inside the magnet passes through the annular magnetic member 7 and the yoke 6
The magnetic field of the magnetic filter is not disturbed, and therefore the function of the magnetic filter for forming the low electron temperature region is not deteriorated. Therefore, a large amount of negative ions can be obtained.

As described above, in this negative ion source device, the conductive mesh member 8 is arranged in the region between the pair of permanent magnets 9 which are magnetic pole pairs and the microwave introduction port 1A. Therefore, the microwaves incident from the microwave introduction port 1A are shielded by the conductive mesh member 8 and are not propagated to the back of the conductive mesh member 8, so that the area surrounded by the magnetic filter and the ion emission port 1B is Electrons are not heated by microwaves to dissociate negative ions. Therefore, a large amount of negative ions can be obtained.

A cooling water passage 12 is provided on the side surface of the discharge vessel 1.
Is provided, the ion discharge port 1B of the discharge vessel 1 is provided.
The permanent magnet 9 attached to the outer wall of the adjacent side surface portion is cooled by the cooling water flowing through the cooling water passage, and the heat demagnetization of the permanent magnet 9 due to overheating of the discharge vessel 1 is prevented.

Further, the solenoid coil 5 and the yoke 6 are supported by the carriage 16 movably arranged on the rails 15, and the headless bolt 7A is pressed against the inner wall surface of the discharge vessel 1 to form the annular magnetic member 7. Since the position is fixed, the installation positions of the solenoid coil 5, the yoke 6, and the annular magnetic member 7 can be adjusted so that an optimal magnetic circuit without leakage of the magnetic field of the solenoid coil 5 to the magnetic filter region is formed. Therefore, the function of the magnetic filter is not deteriorated, and thus a large amount of negative ions are obtained.

Further, when the material of the headless bolt 7A for fixing the position of the annular magnetic member 7 is changed to an insulator such as ceramics, the annular magnetic member 7 and the discharge vessel 1 are electrically insulated, and therefore the mesh shape is formed. The member 8 and the discharge vessel 1 are electrically insulated. So, for example, Applied Physics Letter
s No. 65, No. 7, pages 816 to 818, the potential of the mesh member 8 with respect to the discharge vessel 1 is set to a predetermined value by using a voltage applying means, so that the magnetic filter and the ion discharge can be reduced. It is possible to lower the electron temperature in the low electron temperature region generated with the outlet 1B and increase the electron density in the same region, thus increasing the production amount of negative ions.

In the above description, the case where the magnetic member formed in a ring shape is arranged inside the discharge vessel has been described, but the magnetic member does not always have to be formed in a ring shape, and for example, the magnetic pieces are arranged in parallel. You may choose to install it. Further, it goes without saying that a part of the discharge container may be formed of a magnetic member instead of being arranged inside the discharge container.

[0032]

According to the present invention described above, since the magnetic member is arranged on the inner wall surface of the discharge vessel and the portion facing the yoke end on the ion extracting electrode side, the solenoid coil is used. The generated magnetic field is concentrated and distributed inside the yoke and inside the magnetic member.
Of the magnetic field generated by the solenoid coil, the magnetic field inside the discharge vessel is focused on the yoke via the magnetic member and does not leak to the magnetic filter area, and the magnetic field in the same area generated by the magnetic pole pair is not disturbed. Therefore, it is possible to obtain a negative ion source device capable of stably obtaining a large amount of negative ions for a long time without deteriorating the function of the magnetic filter.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a negative ion source device showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a front view showing an annular magnetic member and a conductive mesh member used in the negative ion source device of the present invention.

FIG. 4 is a sectional view taken along the line BB of FIG. 3;

FIG. 5 is a diagram showing a magnetic field inside the discharge container of the negative ion source device of the present invention and in the vicinity thereof.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Discharge container, 1A ... Microwave introduction port, 1B ... Ion emission port, 1C ... Gas introduction port, 2 ... Ion extraction electrode, 3 ...
DC constant voltage power source, 4 ... Microwave introducing means, 4A ... Microwave oscillator, 5 ... Solenoid coil, 6 ... Yoke, 7
... annular magnetic member, 8 ... conductive mesh member, 9 ... permanent magnet, 10 ... flange, 11 ... insulator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanobu Tanaka 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Power & Electric Development Division

Claims (8)

[Claims] 1. A cylindrical discharge vessel having a gas introduction port, a microwave introduction port, and an ion emission port, an ion extraction electrode disposed adjacent to the ion emission port of the discharge vessel, and an ion extraction electrode, and Voltage applying means for respectively setting the discharge vessel to a predetermined potential, microwave introducing means for introducing microwaves into the discharge vessel, and arranged concentrically with the discharge vessel on the outer peripheral side of the discharge vessel. A negative pole provided with a solenoid coil having a yoke whose inner peripheral side is open, and a magnetic pole pair which is provided on the ion emission port side of the discharge vessel and generates a magnetic field in a direction substantially perpendicular to the direction in which ions are extracted. In the ion source device, a magnetic member is arranged on the inner wall surface of the discharge container and at a portion facing the yoke end on the ion extraction electrode side. On supply. 2. A cylindrical discharge vessel having a gas introduction port, a microwave introduction port and an ion emission port, an ion extraction electrode arranged adjacent to the ion emission port of the discharge vessel, and an ion extraction electrode, and Voltage applying means for respectively setting the discharge vessel to a predetermined potential, microwave introducing means for introducing microwaves into the discharge vessel, and arranged concentrically with the discharge vessel on the outer peripheral side of the discharge vessel. A negative pole provided with a solenoid coil having a yoke whose inner peripheral side is open, and a magnetic pole pair which is provided on the ion emission port side of the discharge vessel and generates a magnetic field in a direction substantially perpendicular to the direction in which ions are extracted. In the ion source device, an annular magnetic member formed concentrically with the discharge vessel in the discharge vessel near the ion emission port side, upstream of the pair of magnetic poles in the ion extraction direction. Negative ion source apparatus characterized by the arranged. 3. A cylindrical non-magnetic discharge vessel having a gas introduction port, a microwave introduction port and an ion emission port, and an ion extraction unit arranged adjacent to the ion emission port of the discharge vessel. An electrode, a voltage applying unit that sets the ion extracting electrode and the discharge container to predetermined potentials, a microwave introducing unit that introduces a microwave into the discharge container, and a discharge container on the outer peripheral side of the discharge container. And a solenoid coil that is concentrically arranged with a yoke that is open on the inner peripheral side, and that is provided on the ion emission port side of the discharge vessel and that generates a magnetic field in a direction substantially perpendicular to the direction in which ions are extracted. In the negative ion source device having a pair of magnetic poles, a part of the discharge vessel on the upstream side of the magnetic pole pair in the ion extracting direction and near the ion emission port is formed of an annular magnetic member. Negative ion source apparatus characterized by the the like. 4. A cylindrical discharge vessel having a gas introduction port, a microwave introduction port and an ion emission port, an ion extraction electrode arranged adjacent to the ion emission port of this discharge vessel, and this ion extraction electrode, and Voltage applying means for respectively setting the discharge vessel to a predetermined potential, microwave introducing means for introducing microwaves into the discharge vessel, and arranged concentrically with the discharge vessel on the outer peripheral side of the discharge vessel. A negative pole provided with a solenoid coil having a yoke whose inner peripheral side is open, and a magnetic pole pair which is provided on the ion emission port side of the discharge vessel and generates a magnetic field in a direction substantially perpendicular to a direction in which ions are extracted. In the ion source device, an annular magnetic member is provided concentrically with the discharge vessel in the discharge vessel and on the side of the ion emission port, and the annular magnetic member has an annular shape. Check unit negative ion source apparatus characterized in that a conductive mesh member so as to cover. 5. The negative ion source device according to claim 4, wherein the mesh member is detachably attached to a side wall of the magnetic member. 6. The negative ion source device according to claim 4, wherein the mesh member is mounted on a side wall surface of the ion extracting electrode of the magnetic member. 7. The negative ion source device according to claim 1, wherein a cooling water channel is provided on a side surface portion of the discharge vessel on the magnetic pole pair side. 8. The negative ion source device according to claim 1, wherein the installation positions of the yoke and the magnetic member are adjustable.