JP3454384B2 - Ion beam generator and method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam generator and method, and more particularly to an ion beam generator and method for continuously generating an ion beam having a high proportion of multiply-charged ions.

[0002]

2. Description of the Related Art An apparatus for vaporizing and ionizing a substance forming a cathode by vacuum arc discharge to form a metal plasma and extracting an ion beam from the metal plasma has been disclosed (for example, Japanese Patent Laid-Open No. 63-63). -27685
No. 8). As shown in FIG. 5, this ion beam generator is composed of a vacuum chamber 1, a cathode 2, an anode 3, an anode holding member 4, a trigger electrode 5, a coil 6, an ion extraction electrode 7, etc. A minute discharge is generated between the trigger electrodes 5 arranged concentrically, whereby an arc discharge is generated between the cathode 2 and the anode 3, and a part of the cathode 2 is vaporized by this arc discharge to form a plasma 8. Then, the magnetic field formed by the coil 6 causes the plasma 8 to pass through the opening of the anode 3,
Furthermore, the ion extraction electrode 7 is adapted to extract the ion beam 9 from the plasma 8 that has passed through the anode 3.

However, in such an ion beam generator, since the ion beam 9 is directly extracted from the metal plasma 8 formed by the vacuum arc discharge, the proportion of multiply charged ionized ions in the ion beam is very low. There is a problem that the power supply capacity of the ion extraction system for applying a predetermined energy to the beam must be increased. Further, this device has a problem that an ion beam can be generated only by a pulse wave of a short time of several milliseconds. Further, this device has a problem that the structure is complicated.

In order to solve such a problem, the inventors of the present invention have devised an ion beam device capable of increasing the proportion of multiply charged ionized ions by introducing a microwave into a vacuum chamber, Filed (Japanese Patent Laid-Open No. 5-
No. 101799). This ion beam device is shown in FIG.
As illustrated in, a cathode 10 and a vacuum chamber 1
1, a microwave introduction unit 12, an arc power supply 13, a magnet 14 for forming a multicusp magnetic field, an ion extraction electrode 15 and the like are provided, and the inside of the vacuum chamber 11 is evacuated to introduce microwaves from the microwave introduction unit 12. A microwave plasma is generated, and the arc power supply 13 is activated to generate a vacuum arc discharge between the cathode 10 and the microwave plasma by using the microwave plasma as a trigger to form a metal plasma 16 of a cathode material in the vacuum chamber 11. , The metal plasma 16 is temporarily enclosed by the magnet 14, the proportion of multiply charged ionized ions is increased by the microwave, and only the ions are extracted by the ion extraction electrode 15.
The ion beam 17 having a high proportion of multiply charged ionized ions is formed.

That is, the application of microwaves amplifies the energy of the electrons in the plasma, thereby promoting the formation of multiply-charged ions due to collisions between electrons and ions or electrons and neutral particles, and metal plasma This is an apparatus for increasing the ratio of multiply charged ionized ions in the inside, and can increase the ratio of multiply charged ionized ions and generate an ion beam continuously for a long time as compared with the apparatus of FIG.

[0006]

However, even with such an ion beam generator, when an attempt is made to maintain the arc discharge by stopping or reducing the introduction of gas to lower the degree of vacuum, the arc is directed to the tip of the cathode. There is a problem that it occurs in the root part or middle part of the cathode without concentrating and a deep dent is formed in this part in a short time, local damage of the cathode and breakage due to this easily occur, and it cannot withstand long-term use. It was Here, in order to generate multiply charged ionized ions, it is indispensable to stop the introduction of gas to lower the degree of vacuum. In addition, since the plasma is used as one of the electrodes, when the plasma fluctuates, the distance between the electrodes fluctuates, which makes control difficult, resulting in poor reproducibility.

The present invention was devised to solve these various problems. That is, it is an object of the present invention to continuously generate an ion beam having a high proportion of multiply-charged ions, to have a long electrode life, to operate stably, and to have a small and simple structure. A generator and method are provided.

[0008]

According to the present invention, a vacuum container divided into a first chamber and a second chamber by a partition plate, an anode having an opening hole penetrating the partition plate and being positively applied And a negatively applied cathode which is arranged on the axis of the opening in the first chamber so as to face the anode, and surrounds the cathode with a gap, and the gap is gradually increased toward the anode side. A conductive hood electrically floating from the anode and the cathode, and a microwave introducing device for introducing microwave into the vacuum container;
An ion beam generator comprising: a magnetic field generator for generating a magnetic field for at least temporarily confining the plasma generated in the chamber and the second chamber.

According to a preferred embodiment of the invention, the cathode has a frusto-conical portion concentric with the axis having a plane facing the anode and the hood has a hollow cylindrical shape concentric with the axis. Is. According to another embodiment, the cathode has a cylindrical shape having an end face facing the anode and is concentric with the axis, and the hood has a portion surrounding the cathode concentric with the axis gradually increasing to the anode side. It is a funnel shape.

A hollow cylindrical insulating support member for supporting the cathode inside, and a hollow cylindrical insulating member having one end connected to the support member and the other end extending along the axis toward the side opposite to the anode. An insulating tube is further provided, and the conductive hood is attached to the outside of the insulating tube with a space. It is preferable that the support member is made of boron nitride and the insulating tube is made of quartz glass. The anode has a hollow cylindrical shape and is made of crystal-grown carbon.

Further, the first chamber and the second chamber communicate with each other through the opening hole of the anode and are evacuated independently, and the second chamber is differentially evacuated so that the degree of vacuum of the second chamber is higher than that of the first chamber. To be done. The cathode is preferably made of a semiconductor or a conductive material.

[0012]

Further , according to the present invention, the first vacuum chamber
Vacuum arc discharge generated between anode and cathode in bar
To form a metal plasma of the cathode material, and
Metal plasma is temporarily contained and the first vacuum chamber
Microwave in the second vacuum chamber that communicates with the chamber.
To heat the metal plasma to increase the proportion of multiply-charged ions.
Increase and extract ions from metal plasma by electric field
Ion beam that generates an ion beam
In the generating method, the axial direction connecting the anode and the cathode is opened, the cathode is surrounded with a conductive hood at intervals, the hood is formed so as to gradually increase the interval to the anode side, and the hood is electrically floated. Te held floating potential, thereby and forming lines of electric force which is substantially perpendicular to the axis between the cathode and the hood ion beam
A method for generating a boom is provided.

[0014]

According to the above apparatus and method of the present invention, a vacuum arc discharge is generated between the anode and the cathode in the first vacuum chamber to form a metal plasma of the cathode material,
By temporarily confining the metal plasma by the magnetic field by the magnetic field generator, and heating the metal plasma by the microwave to increase the proportion of multiply-charged ions, by extracting the ions from the metal plasma by the electric field by the ion extraction electrode, An ion beam having a high proportion of multiply charged ionized ions can be generated.

The hood is electrically floated by surrounding the cathode with a space, formed so that the space gradually increases toward the anode, and having a conductive hood electrically floating from the anode and the cathode. It can be held at a potential and an electric field line can be formed between the cathode and the hood, which is almost orthogonal to the axis, and it is possible to essentially avoid that an arc flies to the root part of the cathode and damages this part, The cathode can be used continuously for a long time, the vacuum chamber can be downsized, and the distance between the cathode and the anode can be shortened.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of an ion beam generator according to the present invention. In this figure, the ion beam generator 20 of the present invention is a vacuum container 2 which is divided into a first chamber 22 and a second chamber 23 by a partition plate 21.
4, an anode 26 having an opening hole 25 penetrating the partition plate 21 and positively applied, and arranged on the axis Z of the opening hole 25 in the first chamber 22 so as to face the anode 26. The cathode 27 that is applied with a negative voltage, the conductive hood 28 that surrounds the cathode 27 at a distance, and the microwave device that introduces microwaves into the vacuum container 24, that is, the second chamber 23 (introduction part 29). And a magnetic field generator 30 for generating a magnetic field for at least temporarily confining the plasma generated in the first chamber 22 and the second chamber 23.

First chamber 22 and second chamber 23
Are independently evacuated by a vacuum device (not shown) using the anode 26 having the opening 25 as a partition. With this configuration, when the arc plasma 32 is generated, differential evacuation can be performed so that the degree of vacuum in the second chamber 23 is higher (pressure is lower) than the first chamber 22 in which the cathode is evaporated and metal ions are generated. it can.

The microwave introducing section 29 is, as shown in the drawing,
It may be provided perpendicular to the axis Z, or as shown in FIG. 6, it may be provided on the side surface of the vacuum chamber. Similar to FIG. 6, the magnetic field generator 30 includes a plurality of permanent magnets 30a for forming a multicusp magnetic field, and air-core coils 30b, 30 for forming mirror magnetic fields provided on both sides of the permanent magnets 30a.
c), and these two magnetic fields form a plasma confining space in the first chamber 22. The magnetic field generator 30 is not limited to such a configuration, and may have various configurations as disclosed in, for example, JP-A-5-101799. The microwave introduced from the microwave introduction unit 29 and the magnetic field generated by the magnetic field generator 30 are set so as to satisfy the electron cyclotron resonance (ECR) condition. With this configuration, the ECR can be used to generate microwave plasma by microwaves and heat the metal plasma. In FIG. 1, reference numeral 41 is an arc power supply that applies the cathode 27 negatively, and 42a and 42b are ion beam extraction power supplies.

The device described above is used as follows.
That is, the inside of the vacuum chambers 22 and 23 is maintained in vacuum (for example, 10 ^-2 to 10 ^-4 Torr), and a vacuum arc discharge 31 is generated between the anode 26 and the cathode 27 to form a metal plasma of a cathode material. In this state, the vacuum degree in the vacuum chambers 22 and 23 is maintained at 10 ⁻⁵ to 10 ⁻⁶ Torr, the metal plasma is temporarily confined by the magnetic field generated by the magnetic field generator 30, and the metal plasma is heated by the microwave. The proportion of multiply-charged ions is increased, and the ion beam 38 is generated from the metal plasma by the electric field generated by the ion beam extraction electrode 37. This ion beam 38
Is introduced into another apparatus through the opening 24a provided in the vacuum container and used for the purpose of separating metal plasma, forming a metal film, implanting a dissimilar metal into the substrate, an X-ray source, a laser source, etc. You can

FIG. 2 is an enlarged view of the main part of FIG. In the figure, the anode 26 is a hollow cylindrical stainless tube having an inward flange surface 26a on the cathode side, a female screw provided on the inner surface, and is fixed to a partition plate 21 that is water-cooled. 21a is screwed and attached. The anode 26 is preferably made of crystal-grown carbon in terms of heat resistance. With this configuration, a sufficiently large opening hole 25 (for example, diameter 55 mm) is formed on the axis Z, and an ion beam 32 (for example, diameter 20 mm) having a relatively large diameter is formed while performing the above-described differential pumping. Second
It can be introduced into the chamber 23.

The hood 28 is electrically conductive (for example, made of stainless steel) and is electrically floated from the anode 26 and the cathode 27. That is, referring to FIG. 2, the apparatus of the present invention further includes a hollow cylindrical insulating support member 33 for supporting the cathode 27 inside, one end of which is connected to the support member 33, and the other end of which is along the axis Z. And an insulating tube 34 having a hollow cylindrical shape extending on the opposite side of the anode. Insulation tube 3
Although 4 is a double pipe in this figure, the present invention is not limited to this and may be, for example, a single pipe without the outer pipe in the figure. Further, the hood 28 is attached to the outside of the insulating pipe 34 with a mounting member 35 (for example, a screw) at a distance. With this configuration, the hood 28 is electrically insulated from the anode 26 and the cathode 27 and is held at the floating potential.

The supporting member 33 is preferably made of an insulating material containing no hydroxyl group (OH), for example, boron nitride (BN) so as not to react with the cathode material. Also,
The insulating tube 34 is preferably made of an insulating material having high heat resistance, such as quartz glass or ceramic. Further, as shown in the figure, the outer peripheral surface of the supporting member 33 is surrounded by the outer tube of the insulating tube 34 so that droplets of the cathode material generated by evaporation or arc discharge do not adhere to the outer peripheral surface of the supporting member 33. Good.

Further, in FIG. 2, the cathode 27 has a frustoconical portion 27b concentric with the axis Z having a plane 27a facing the anode 26, while the hood 28 is a hollow cylinder concentric with the axis Z. It is shaped into a shape. With this configuration, the distance between the cathode and the hood can be gradually increased toward the anode. For the cathode 27, a semiconductor such as silicon, a conductive substance such as copper, titanium, tantalum, iron, or the like, or a mixture of these powders in a certain ratio and solidified is used.

With the above structure, as shown in FIG. 3 (A), the axis line Z is formed between the cathode 27 and the hood 28.
A line of electric force 36 substantially orthogonal to the electrode 26 can be formed, a vacuum arc discharge 31 can be generated between the flat surface 27a of the cathode and the anode 26, and the electrode (cathode) can be formed.
It has a long life and can be operated stably. Further, since the distance between the anode and the cathode can be shortened as compared with the conventional example shown in FIG. 6, the device can be made compact and have a simple structure.

On the other hand, FIG. 3B shows the case where the hood 28 is not provided. In this case, vacuum arc discharge 31 is generated near the base of the cathode, and the vicinity of the base is damaged in a short time. The problem of denting or breaking occurs. Furthermore, since high heat is generated near the root of the cathode due to arc discharge, there is a problem that the insulating tube 34 is easily damaged.
Therefore, the hood 28 is an important component for downsizing the device of the present invention, ensuring stable operation, and extending the life of the cathode 27. Further, if the hood 28 is electrically connected to the anode without being electrically floated, an arc may fly between the hood and the cathode. Conversely, if the hood 28 is connected to the cathode, the arc may fly to the hood and damage the hood. It is also important to float electrically because there is a risk.

FIG. 4 shows a second embodiment of the present invention.
It is a partially expanded view similar to FIG. In this figure, the cathode 39 has a cylindrical shape having an end face 39 a facing the anode 26 and concentric with the axis Z, and the hood 40 is a cathode 39.
Is a funnel shape concentric with the axis Z that gradually increases toward the anode side. Other parts are the same as those in the first embodiment shown in FIGS. With such a configuration, as in FIG. 2, the gap between the cathode and the hood can be formed so as to gradually increase toward the anode side, and the cathode 39 and the hood 40 can be formed.
Forming an electric force line 36 substantially orthogonal to the axis Z between
A vacuum arc discharge 31 can be generated between the end surface 39a of the cathode and the anode 26, and the life of the electrode (cathode) can be extended and the electrode can be stably operated. Further, the cathode 39 having this configuration is easy to process and can be manufactured at a low cost, the plasma diameter can be made constant, and the stable ion beam 32 can be generated for a longer time.

As described above, according to the apparatus and method of the present invention, the vacuum arc discharge 31 is generated between the anode and the cathode in the first vacuum chamber 22 to form the metal plasma of the cathode material, and the magnetic field is generated. By temporarily confining the metal plasma with a magnetic field generated by the device 30 and heating the metal plasma with microwaves to increase the proportion of multiply-charged ions, the ions are extracted from the metal plasma by the electric field generated by the ion extraction electrode. An ion beam 37 having a high proportion of valence ionized ions can be generated through the aperture 24a.

Further, by surrounding the cathodes 27, 39 with a space therebetween, and by forming the conductive hoods 28, 40 which are formed so that the space gradually increases toward the anode side and which are electrically floated from the anode and the cathode, It is possible to hold the hood electrically at a floating potential and form a line of electric force 36 between the cathode and the hood, which is substantially orthogonal to the axis line, and it is essential that an arc fly to the root part of the cathode and damage this part. The cathode can be used continuously for a long time, the vacuum chamber can be made small, and the distance between the cathode and the anode can be shortened.

Further, the present invention removes the partition plate 21 including the anode 26, introduces the microwave from the microwave introduction part 29 to generate plasma, and includes the plasma and the hood 28 constructed according to the present invention. It is also possible to generate a vacuum arc discharge with the cathode 27. The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0030]

As described above, the ion beam generating apparatus and method of the present invention can continuously generate an ion beam having a high proportion of multiply charged ionized ions, have a long electrode life and are stable. It has excellent effects such as being operable, being small and having a simple structure.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an ion beam generator according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a diagram schematically showing an effect of a hood.

FIG. 4 is a partially enlarged view showing a second embodiment of the present invention.

FIG. 5 is a partial configuration diagram of a conventional ion beam generator.

FIG. 6 is an overall configuration diagram of another ion beam generator by the present inventors.

[Explanation of symbols]

1, 11 Vacuum chamber 2, 10, 27 cathode 3, 26 Anode 4 Anode holding member 5 Trigger electrode 6, 14 coil (magnet) 7,15 Ion extraction electrode 8 plasma 9,17 Ion beam 12 Microwave introduction section 13 Arc power supply 16 metal plasma 20 Ion beam generator 21 Partition board 22 First chamber 23 Second chamber 24 vacuum vessels 25 open holes 28 Hood 29 Microwave introduction section 30 Magnetic field generator 31 vacuum arc discharge 32 arc plasma 33 Support member 34 Insulation pipe 35 Mounting bracket 36 lines of electric force 37 Ion beam extraction electrode system 38 ion beam 39 cathode 40 hood

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01J 37/08 H01J 27/08 H01J 27/18

Claims (9)

(57) [Claims] 1. A vacuum container divided into a first chamber and a second chamber by a partition plate, an anode having an opening hole penetrating the partition plate and being positively applied, and the opening hole in the first chamber. A cathode, which is arranged to face the anode on the axis of the negative electrode and is negatively applied, surrounds the cathode with a space, and the space is formed so that the space gradually increases toward the anode side and electrically floats from the anode and the cathode. A conductive hood, a microwave introduction device for introducing microwaves into the vacuum container, and a magnetic field generation device for generating a magnetic field that at least temporarily confines the plasma generated in the first chamber and the second chamber. An ion beam generator characterized in that 2. The cathode has a frustoconical portion concentric with an axis having a plane facing the anode, and the hood is a hollow cylindrical shape concentric with the axis. The ion beam generator according to claim 1. 3. The cathode has a cylindrical shape having an end face facing the anode and concentric with the axis, and the hood has a funnel shape in which a portion surrounding the cathode is concentric with the axis gradually increasing to the anode side. The ion beam generator according to claim 1, wherein. 4. A hollow-cylindrical insulating support member for supporting the cathode inside, and a hollow-cylindrical support member having one end connected to the support member and the other end extending axially opposite to the anode. The ion beam generator according to claim 1, further comprising: an insulating tube, wherein the conductive hood is attached to the outer side of the insulating tube with a space therebetween. 5. The ion beam generator according to claim 4, wherein the support member is made of boron nitride, and the insulating tube is made of quartz glass. 6. The anode has a hollow cylindrical shape and is made of crystal growth carbon.
Ion beam generator according to. 7. The first chamber and the second chamber communicate with each other through an opening hole of an anode, and are evacuated independently of each other, and the second chamber is differentially evacuated so that the degree of vacuum of the second chamber is higher than that of the first chamber. The ion beam generator according to claim 1, wherein 8. The ion beam generator according to claim 1, wherein the cathode is made of a semiconductor or a conductive material. 9. An anode and a cathode in the first vacuum chamber.
A vacuum arc discharge is generated between the swords to
Forming a metal plasma and temporarily activating it with a magnetic field
Second containment, which communicates with the first vacuum chamber
Metal plasma by microwave in the vacuum chamber of
Heating to increase the proportion of multiply charged ionized ions,
Ions are extracted from the metal plasma, which
In the method of generating an ion beam for generating a dome, an axial direction connecting the anode and the cathode is opened to surround the cathode with a conductive hood at intervals, and the hood is formed so that the interval gradually increases toward the anode side, and An ion beam generating method, characterized in that the hood is electrically floated and held at a floating potential, thereby forming a line of electric force between the cathode and the hood substantially orthogonal to the axis.