JPH0927280A - Filament fixing member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make both a filament current conductor and a mounting bolt usable repeatedly by enabling a filament to be attached and removed without damaging the mounting bolt and the threaded part of the filament current conductor even if a filament abutting part is deformed by the heating of the filament. SOLUTION: A filament abutting part 8, that is, the end of a mounting bolt 7, is formed into a cylindrical shape smaller than the minor diameter of the mounting bolt 7. By threading the mounting bolt 7 into a bolt mounting hole 6b formed in a filament current conductor 6, the filament abutting part 8 is pressed against and fixes a filament 2 in place that is inserted in a filament hole 6a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filament fixing member, and more particularly to a filament fixing member used in an arc discharge type ion source.

[0002]

2. Description of the Related Art In recent years, ion sources for converting elements into plasma and extracting ions in the plasma as ion beams have been used in various fields such as ion implantation, ion plating, crystal growth, or ion processing. .

In the above ion source, a current is passed through a cathode filament provided in a plasma generation chamber,
Ion species gas introduced into the plasma generation chamber by using arc discharge due to emission of thermoelectrons from the filament generated by heating the filament and applying a voltage between the filament and the plasma generation chamber There is a low-voltage arc discharge type ion source typified by a Freeman type ion source, which generates ions by making a plasma into a plasma. In the ion source, both ends of the filament are extended to the outside of the plasma generation chamber through an insulating support member provided in the chamber for connecting to a power source provided outside the plasma generation chamber. ing.

In these conventional low-voltage arc discharge type ion sources, a filament mounting portion which is a connection portion between the filament and an external power source such as a filament power source and an arc power source will be described with reference to FIG. Is the street.

That is, the filament attachment portion 55
Comprises a filament current conductor 56 and a mounting bolt 57 for pressing and fixing the filament 52,
The configuration is such that the current supplied from the power source connected to the filament current conductor 56 is transmitted to the filament 52.

A filament insertion hole 56a is formed in the filament current conductor 56. One end of the filament 52 is inserted into the filament insertion hole 56a. Further, the filament current conductor 56 is provided with a bolt attachment hole 56b in a direction perpendicular to the filament insertion hole 56a from the filament insertion hole 56a to the outer wall surface of the filament current conductor 56. A mounting bolt 57 is screwed into the bolt mounting hole 56b. The length of the mounting bolt 57 is set to be slightly longer than the length of the bolt mounting hole 56b, and the tip of the mounting bolt 57 presses and fixes the filament 52 inserted in the filament insertion hole 56a. The filament 52, the filament current conductor 56, and the mounting bolt 57 may be made of tungsten, molybdenum, or
It is formed of a refractory metal such as tantalum.

[0007]

However, in the filament mounting portion 55, which is the conventional filament fixing member, when the filament 52 becomes hot, the tip of the mounting bolt 57 that presses the filament 52 is heated or heated. It may be deformed due to expansion and become thicker than the root diameter of the threaded portion of the bolt mounting hole 56b formed in the filament current conductor 56. As a result, for example, when the mounting bolt 57 is removed to replace the filament 52, the threaded portion of the bolt mounting hole 56b may be damaged, and the filament current conductor 56 and the tip of the threaded portion are damaged. There is a problem in that it is necessary to frequently replace the attached mounting bolt 57. Particularly, in a low voltage arc discharge type ion source, since the filament 52 provided in the arc chamber is sputtered by charged particles in the plasma, the filament 5
It is necessary to replace the 2 relatively frequently and the solution to the above problem is eagerly awaited.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a filament fixing member that can repeatedly use the constituent members.

[0009]

In order to solve the above-mentioned problems, a filament fixing member according to a first aspect of the present invention has a filament insertion hole into which a part of a filament which is heated by an electric current is detachably inserted. Is formed, a screw hole communicating with the filament insertion hole is formed in a direction substantially perpendicular to the insertion direction of the filament, and a filament current conductor to which a power supply for supplying a current to the filament is connected,
A filament fixing member that includes a screw member that is screwed into the screw hole, and that fixes the filament in a state of being electrically connected to a power source by tightening the screw member, including the following member. .

That is, there is provided a filament abutting member interposed between the tip of the screw member and the filament and having an outer dimension smaller than the root diameter of the screw hole.

The outer dimensions of the filament contact member are set so that the outer dimensions of the filament after deformation due to heat generation of the filament are smaller than the root diameter of the screw hole.

It should be noted that how thinly the filament contact member is formed from the above-mentioned root diameter depends on the heat and pressure applied to the filament contact member when the filament generates heat, or the dimensions of the filament contact member. Will be decided.

In the above structure, when an electric current is applied to the filament by the power source, the filament generates heat. The heat generated by the filament causes the filament, the filament current conductor, and the filament abutment member to
It becomes extremely hot. As a result, the filament abutting member receives heat from the filament,
Due to the thermal expansion of the filament current conductor and the filament abutment member, the filament is deformed and slightly bulges outward due to the applied pressure.

However, the outer dimension of the filament contact member is set to be smaller than the root diameter of the screw member (that is, the inner diameter of the screw hole) in advance, in consideration of the increase in the outer dimension due to the above deformation, so that the deformed filament is deformed. The outer dimension of the contact member does not exceed the inner diameter of the screw hole.

Therefore, when the screw member is removed for filament replacement or the like, the filament current conductor having the screw hole, the screw member, and the filament contact member can be attached and detached without damage. As a result, it is possible to save the labor of removing the thickened screw member, which has conventionally occurred, and to greatly extend the life of the filament current conductor and the screw member in which the screw holes are formed.

In order to solve the above-mentioned problems, a filament fixing member according to a second aspect of the present invention is provided with a filament insertion hole into which a part of the filament which is heated by an electric current is detachably inserted. A filament fixing member having a filament current conductor connected to a power supply for supplying a current to the device is characterized by including the following members.

That is, the filament current conductor is
The end portion is formed in a columnar shape having a central axis in a direction substantially perpendicular to the filament insertion direction, and a contact member insertion hole communicating with the filament insertion hole is formed along the central axis. Is formed up to the end surface of.

Further, an engaging member screwed to cover the end of the filament current conductor, and a protruding member provided at a position corresponding to the abutting member inserting hole of the engaging member, the abutting member inserting hole. And a filament contacting member to be inserted into.

Further, the locking member presses the filament through the filament contact member to fix the filament in a state of being electrically connected to the power source.

In the above structure, when an electric current is applied to the filament and the filament, the filament current conductor, and the filament abutting member become high in temperature, the filament abutting member is strengthened by the thermal expansion of each of the above members, and the pressure and heat are increased. It deforms due to and bulges slightly to the outside. But,
Since the contact member insertion hole into which the filament contact member is inserted does not have a threaded portion, when removing the bulged filament contact member and locking member for replacement of the filament, the locking member Both can be easily removed without damaging the screwed portion.

Therefore, it is possible to save the trouble of conventionally removing the thickened screw member. Further, since the filament current conductor and the threaded portion of the locking member are not damaged when the locking member is attached and detached, the filament fixing member can be repeatedly used and a long-life filament fixing member can be realized.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

The ion source according to this embodiment is of an arc discharge type such as a Bernus type. As shown in FIG. 2, the ion source includes an arc chamber 1 for generating plasma, a cathode filament (hereinafter simply referred to as a filament) 2 provided in the arc chamber 1, and a filament 2. A filament power source (power source) 3 for supplying an electric current and an arc power source 4 for applying a voltage to the filament 2 and the arc chamber 1 are provided, and a gas box or an oven (not shown) is provided with a gas introduction pipe (not shown). Arc chamber 1
This is a configuration in which the ion species gas introduced into the inside is turned into plasma by arc discharge.

The filament 2 provided in the arc chamber 1 is made of, for example, tungsten and is formed in a substantially U shape. Both ends of the filament 2 are
The arc chamber 1 is supported by filament field throughs 1 a, 1 a, which are insulating support members provided at a predetermined interval on one wall surface, and extends to the outside of the arc chamber 1. Further, a reflection electrode 1c supported by one wall surface of the arc chamber 1 via an insulating support member 1b is installed at a position facing the filament 2 in the arc chamber 1. The reflective electrode 1c repels the thermoelectrons emitted from the filament 2 to the filament 2 side, and is normally placed at the same potential as the filament 2 or a floating potential. A magnetic field B is formed in the direction from the filament 2 to the reflective electrode 1c by a solenoid coil (not shown) provided outside the arc chamber 1. Due to this magnetic field B, thermoelectrons emitted from the filament 2 drift between the filament 2 and the reflective electrode 1c. The thermoelectrons drifting along the magnetic field B are generated by the filament 2 at the filament potential.
Further, since it is driven back in front of the reflection electrode 1c and is confined between the two, the range distance (that is, the lifetime) becomes long.

A filament power supply 3 and an arc power supply 4 are provided outside the arc chamber 1.
As described above, both ends of the filament 2 extending outside the arc chamber 1 and the terminals of the filament power source 3 and the arc power source 4 are connected via the filament attachment portion (filament fixing member) 5.

Both terminals of the filament power source 3 are connected to both ends of the filament 2 through the filament mounting portions 5, respectively. This gives, for example, 2
A current of about 00 A can be passed through the filament 2 to heat the filament 2. Further, the positive electrode terminal of the arc power source 4 is connected to the arc chamber 1, and the negative electrode terminal of the arc power source 4 is connected to the filament 2 via the filament attachment portion 5, and a voltage required for arc discharge (for example, About 60 V) can be applied.

As shown in FIG. 1, the filament attachment portion 5 which is a connection portion with the filament power source 3 and the arc power source 4 has a filament current conductor 6 and a filament 2
And a mounting bolt (screw member) 7 for contacting the filament current conductor 6 with.

The filament current conductor 6 is made of a material having excellent heat resistance, such as molybdenum, and is connected to the filament power source 3 or the arc power source 4. The filament current conductor 6 is provided with a filament insertion hole 6a having an inner diameter slightly longer than the outer diameter of the filament 2. The insertion hole 6a
The end of the filament 2 is inserted in the. Further, from the surface of the filament current conductor 6 to the filament insertion hole 6
Up to a, a bolt mounting hole (screw hole) 6b is formed which penetrates in a direction substantially perpendicular to the axial direction of the insertion hole 6a.
A thread groove is formed in the bolt mounting hole 6b, and the mounting bolt 7 is screwed into the bolt mounting hole 6b.

A mounting bolt 7 is screwed into the bolt mounting hole 6b. The outer diameter of the filament contact portion (filament contact member) 8 that is the tip of the mounting bolt 7 is set to be smaller than the root diameter of the mounting bolt 7. The outer diameter of the filament contact portion 8 is determined by the heat and pressure applied to the filament contact portion 8 during the operation of the ion source,
The dimensions of the filament contact portion 8 are taken into consideration, and the outer diameter of the filament contact portion 8 deformed by the heat and pressure is set so as not to exceed the root diameter of the mounting bolt 7.

In this embodiment, an M4 bolt having a root diameter of 3.242 mm is used as the mounting bolt 7, and the outer diameter of the filament contact portion 8 is set to about 2.5 mm. The axial length of the filament contact portion 8 is set to about 1 mm.

The length of the above-mentioned mounting bolt 7 is determined from the surface of the filament current conductor 6 to the filament insertion hole 6
It is set to be slightly longer than the length up to a. Therefore, the filament abutting portion 8 is crimped to the filament 2 inserted into the filament insertion hole 6 by screwing the mounting bolt 7, and fixes the filament 2.

By the way, as the material for the filament current conductor 6, the mounting bolt 7 and the filament contact portion 8, it is desirable that the filament current conductor 6 has high conductivity and melting point, and is strong against pressure at high temperature and has low thermal expansion coefficient. Be done. As a material that sufficiently satisfies these conditions, for example, tantalum, tungsten, molybdenum, or the like can be used. Among them, tungsten is most preferable in terms of strength against pressure at high temperature. Further, among the above conditions, the filament current conductor 6 is emphasized in conductivity, and the filament abutting portion 8 is strongly required to have strength against pressure especially in a high temperature state. further,
In order to prevent the seizure of the screwed portion due to heat, it is preferable that the filament current conductor 6 and the mounting bolt 7 are made of different materials.

In the above structure, the filament power source 3 shown in FIG.
When a current of about A is passed, the filament 2 heats up.
Furthermore, when the arc power supply 4 is turned on and a voltage (for example, about 60 V) necessary for arc discharge is applied between the arc chamber 1 and the filament 2, the filament 2 that has generated heat
Thermions are emitted from them to generate arc discharge. When the emitted thermoelectrons collide with the particles of the ion species gas introduced into the arc chamber 1, the gas particles are ionized,
Ions are generated by turning into plasma.

During the operation of the ion source, a current is applied to the filament 2, so that the filament 2 heats up and reaches a high temperature. Further, as shown in FIG. 1, the filament current conductor 6 and the filament contact portion 8 that are in contact with the filament 2 also become hot. In addition, the filament 2, the filament current conductor 6, and the filament contact portion 8 are
Expands due to heat. Therefore, the filament contact portion 8 of the mounting bolt 7 is heated to a high temperature and is subjected to stronger pressure. Since a gap is formed between the outer peripheral wall surface of the filament contact portion 8 and the inner wall of the bolt mounting hole 6b, the radial pressure applied to the filament contact portion 8 is smaller than in other directions. . As a result, the filament contact portion 8 formed of a high melting point material such as tantalum is slightly deformed radially outward.

On the other hand, since the filament 2 is thinned by being sputtered in the arc chamber 1 shown in FIG. 2 during the operation of the ion source, the filament 2 needs to be replaced relatively frequently. When the filament 2 is replaced, the mounting bolt 7 is attached to the bolt mounting hole 6
It is removed from b.

As described above, the filament contact portion 8 of the mounting bolt 7 is deformed by the applied pressure and heat and slightly bulges outward in the radial direction. However, since the outer diameter of the filament contact portion 8 is set in advance to be smaller than the root diameter of the mounting bolt 7 in consideration of the amount of deformation due to heat, even when the filament contact portion 8 swells slightly. The root diameter of the mounting bolt 7 (that is, the inner diameter of the bolt mounting hole 6b) is not exceeded. As a result, the mounting bolt 7 and the filament contact portion 8 can be removed without damaging the bolt mounting hole 6b.

By the way, when the mounting bolt 7 or the filament contact portion 8 swells and its outer diameter exceeds the inner diameter of the bolt mounting hole 6b, the filament contact portion 8
Also, the mounting bolt 7 may damage the threaded portion of the bolt mounting hole 6b during mounting. Furthermore, when removing the bulging mounting bolt 7 and the filament abutting portion 8 mounted on the filament current conductor 6, the threaded portion of the bolt mounting hole 6b formed on the filament current conductor 6 is damaged, The filament current conductor 6 may be unusable.

However, in the filament mounting portion 5 according to the present embodiment, even when the filament contact portion 8 is slightly expanded, the outer diameter thereof does not exceed the inner diameter of the bolt mounting hole 6b, and the filament current conductor is 6 and the mounting bolt 7 are not damaged. As a result, both members 6 and 7 can be used repeatedly.

The filament contact portion 8 may be made of a material different from that of the mounting bolt 7. In this case, the material according to the pressure and heat applied to each part can be individually selected. Furthermore, when it is difficult to join the filament contact portion 8 and the mounting bolt 7, they may be formed as separate members.
Accordingly, for example, the mounting bolt 7 can be formed of tantalum, and particularly, only the filament contact portion 8 that is required to have strength against pressure in a high temperature state can be formed of tungsten.

In any case, the mounting bolt 7 can press and fix the filament 2 via the filament contact portion 8. Moreover, since the outer diameter of the filament contact portion 8 is set to be smaller than the root diameter of the bolt mounting hole 6b formed in the filament current conductor 6, the same effect as when integrally molded can be obtained.

[Embodiment 2] Another embodiment of the present invention will be described below with reference to FIGS. 2 and 3. It should be noted that the same function as in the first embodiment,
The members having the same configurations are given the same reference numerals as those in the first embodiment, and the description thereof will be omitted.

The ion source according to this embodiment is of a low voltage arc discharge type, and as shown in FIG. 2, the filament 2 connected to the filament power source 3 and the arc power source 4 via the filament attachment parts 5 and 5. Emits thermoelectrons, and the arc discharge generated thereby causes the ion species gas introduced into the arc chamber 1 to turn into plasma.

As shown in FIG. 3, the filament mounting portion 5 includes a filament current conductor 16 and a filament 2
And a locking member 19 for bringing the filament current conductor 16 into contact therewith.

The end of the filament current conductor 16 is
It is formed in a cylindrical shape, and a thread groove is formed on the outer peripheral wall surface thereof. The filament current conductor 16 is formed with an insertion hole 16a having an inner diameter slightly larger than the outer diameter of the filament 2 in a direction perpendicular to the axial center of the end portion. A filament contact portion insertion hole (contact member insertion hole) 16c, which is a round hole, is formed along the axis of the end of the filament current conductor 16 from the insertion hole 16a to the end surface of the end. There is.

The locking member 19 is formed in a cylindrical shape with one end closed, and its inner diameter is set to be substantially the same as the outer diameter of the end of the filament current conductor 16. Also,
The locking member 19 has a thread groove formed on its inner wall,
The filament current conductor 16 is screwed so as to cover the end portion thereof. Further, a cylindrical filament contact portion (filament contact member) 18 having a diameter smaller than the inner diameter of the filament contact portion insertion hole 16c projects from the center of the inner surface of the closed end of the locking member 19 along the axis. It is set up.

The axial length of the filament contact portion 18 is set to be slightly longer than the length from the end surface of the filament current conductor 16 to the filament insertion hole 16a. Therefore, when the locking member 19 is screwed into the filament current conductor 16, the filament contact portion 18 presses and fixes the filament 2 inserted in the insertion hole 16a.

In the above structure, when the filament power supply 3 and the arc power supply 4 shown in FIG. 2 are turned on, the filament 2 generates heat, and the filament current conductor 16 and the filament contact portion of the locking member 19 which are in contact with the filament 2 are heated. 18 becomes hot and expands due to heat.
As a result, the filament contact portion 18 shown in FIG. 3 is heated to a high temperature, receives a stronger pressure, and slightly expands radially outward.

However, the outer diameter of the filament contact portion 18 is set to be shorter than the inner diameter of the filament contact portion insertion hole 16c. Even if the diameter of the filament contact portion 18 is large, it does not cause any trouble. Further, since the outer peripheral portion of the end portion of the filament current conductor 16 is screwed into the locking member 19, even if the outer diameter of the filament contact portion 18 is increased, the screwed portion is not damaged, Filament current conductor 16, filament contact portion 1
8 and the locking member 19 can be used repeatedly.

As the material of the filament current conductor 16 and the filament contact portion 18, it is desired that the filament current conductor 16 and the filament contact portion 18 have high conductivity and melting point, and are strong against pressure at high temperature and have low thermal expansion coefficient. As a material that sufficiently satisfies these conditions, for example, tantalum, tungsten, molybdenum, or the like can be used. Among them, tungsten is most preferable in terms of strength against pressure at high temperature.

In the present embodiment, the filament contact portion 18 and the locking member 19 are integrally formed, but the invention is not limited to this, and the filament contact portion 18 may be locked partially or entirely. It may be formed of a material different from that of the member 19. Further, from the viewpoint of operability at the time of attachment and detachment, it is desirable that the filament contact portion 18 be fixed to the locking member 19, but the locking member 19 and the filament contact portion 18 are fixed.
The and may be removable. Also in this case, when the locking member 19 is screwed to the filament current conductor 16, the inner wall surface of the locking member 19 is the filament contact portion 1.
Since it is in contact with the filament contact portion 8, the filament contact portion 18 can press and fix the filament 2 inserted in the filament insertion hole 16a.

In each of the above-mentioned embodiments, the Bernus type ion source is described as an example, but the present invention is not limited to this, and the filament fixing member according to the present invention can be used in other low ion sources such as a Freeman type ion source. It can be applied to the attachment part of the filament of the voltage arc discharge type ion source.

[0052]

As described above, the filament fixing member according to the first aspect of the present invention is interposed between the tip of the screw member and the filament, and has a filament abutment having an outer dimension smaller than the root diameter of the screw hole. The filament contact member is provided with a member, and the outer dimension of the filament contact member is set such that the outer dimension after deformation due to heat generation of the filament is smaller than the root diameter of the screw hole.

Therefore, even if the filament abutting member that abuts against the filament swells slightly due to heat and pressure, the outer dimensions of the filament abutting member do not exceed the inner diameter of the screw hole. Therefore,
When removing the screw member to replace the filament,
The screw member and the filament contact member can be attached and detached without damaging the screw member and the screw hole.

As a result, it is possible to save the labor of forcibly removing the thickened screw member at the time of attaching and detaching the screw member, which is conventionally generated, and to significantly extend the life of the screw member and the filament current conductor.

As described above, in the filament fixing member according to the second aspect of the present invention, the end portion of the filament current conductor is formed in a cylindrical shape having a central axis in a direction substantially perpendicular to the filament insertion direction. At the same time, a contact member insertion hole communicating with the filament insertion hole is formed up to the end surface of the end portion along the central axis, and the engagement member is screwed to cover the end portion of the filament current conductor, and A filament contact member protruding from a position corresponding to the contact member insertion hole of the locking member and inserted into the contact member insertion hole;
The locking member presses the filament through the filament contact member and fixes the filament in a state of being electrically connected to the power supply.

Therefore, even if the tip of the filament abutting member that abuts against the filament swells outward slightly due to heat and pressure, the locking member and the filament abutting member can be attached and detached without damaging the threaded portion. it can.

As a result, there is an effect that it is possible to realize a filament fixing member which can be repeatedly used and has a long life, while eliminating the trouble of forcibly removing the thickened screw member at the time of attaching and detaching the screw member which has been conventionally generated.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a vertical cross-sectional view showing a mounting portion of a filament in a low-voltage arc discharge type ion source.

FIG. 2 is an explanatory diagram showing a configuration of a main part of the ion source.

FIG. 3 illustrates another embodiment of the present invention,
It is a longitudinal cross-sectional view which shows the attachment part of the filament in a low voltage arc discharge type ion source.

FIG. 4 is a vertical cross-sectional view showing a conventional example, showing a filament attachment portion in a low-voltage arc discharge type ion source.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Arc chamber 2 Cathode filament (filament) 3 Filament power supply (power supply) 4 Arc power supply 5 Filament mounting part (filament fixing member) 6 Filament current conductor 6a Filament insertion hole 6b Bolt mounting hole (screw hole) 7 Mounting bolt (screw member) 8 filament contact part (filament contact member) 16 filament current conductor 16a filament insertion hole 16c filament contact part insertion hole (contact part insertion hole) 18 filament contact part (filament contact member) 19 locking member

Claims (2)

[Claims] 1. A filament insertion hole is formed in which a part of a filament that is heated by an electric current is removably inserted, and a screw hole communicating with the filament insertion hole is substantially perpendicular to the filament insertion direction. A filament current conductor connected to a power source for supplying a current to the filament and a screw member screwed into the screw hole, and the filament is electrically connected to the power source by tightening the screw member. In the filament fixing member to be fixed with, a filament abutting member that is interposed between the tip of the screw member and the filament and has an outer dimension smaller than the root diameter of the screw hole is provided. , The external dimensions after deformation due to the heat generated by the filament are set to be smaller than the root diameter of the screw hole. Filament fixing member, characterized in that. 2. A filament fixing device having a filament current conductor connected to a power source for supplying a current to the filament, wherein a filament insertion hole is formed into which a part of the filament, which is heated by an electric current and generates heat, is detachably inserted. In the member, the filament current conductor has an end portion formed in a cylindrical shape having a central axis in a direction substantially perpendicular to the insertion direction of the filament, and a contact member insertion hole communicating with the filament insertion hole is formed. A locking member formed along the central axis up to the end surface of the end and screwed to cover the end of the filament current conductor, and a position corresponding to the contact member insertion hole of the locking member. And a filament contact member that is inserted into the contact member insertion hole, and the locking member pushes the filament through the filament contact member. A filament fixing member characterized by pressing and fixing the filament in a state of being electrically connected to a power source.