CN111739774A

CN111739774A - Ion source

Info

Publication number: CN111739774A
Application number: CN201911375354.3A
Authority: CN
Inventors: 川村昌充; 山元彻朗
Original assignee: Nisshin Ion Machine Co ltd
Current assignee: Nisshin Ion Machine Co ltd; Nissin Ion Equipment Co Ltd
Priority date: 2019-03-25
Filing date: 2019-12-27
Publication date: 2020-10-02
Also published as: KR20200115016A; JP2020161241A

Abstract

The invention provides an ion source, which can restrain the loss of an electron emission part of a hot cathode caused by positive ions. The ion source (10) is configured to include: a plasma generation container (20); a hot cathode (30) which is disposed outside the plasma generation container (20) and emits electrons (e) into the plasma generation container; and an emitter power source (Ee) for applying a direct-current voltage positive to the plasma generation container (20) to the hot cathode (30), wherein the ion source (10) is provided with a cross electric field forming element (40) for forming a cross electric field (E1) that crosses in a cross direction (D) that crosses a direction from the electron emitter toward the inside of the plasma generation container, in at least a partial region (R1) of a region through which electrons (E) pass from the electron emitter (30a) of the hot cathode (30) into the inside of the plasma generation container.

Description

Ion source

Technical Field

The present invention relates to ion sources, and more particularly to ion sources for generating ion beams.

Background

As an ion source for generating an ion beam in an ion implantation apparatus or the like, for example, an ion source disclosed in patent document 1 is known.

As shown in fig. 10, an ion source 100 disclosed in patent document 1 includes: a filament 311; a cathode 302 which is heated by a filament 311 and emits thermal electrons; and an ionization chamber 102 into which a gaseous material is introduced, and an emitter power supply 430 for applying an emitter voltage Ve to make the cathode 302 negative is connected between the ionization chamber 102 and the cathode 302.

Thermal electrons emitted from the cathode 302 are accelerated by the emitter voltage Ve, introduced into the ionization chamber 102 through the opening 312 of the ionization chamber 102, and generate plasma by colliding with gas molecules as a raw material in the ionization chamber 102. The positive ions generated at this time are extracted as an ion beam to the outside of the ionization chamber 102 together with the electrons, but some of the positive ions flow into the cathode 302 side from the opening 312, are accelerated toward the cathode 302 side by the emitter voltage Ve, and collide with the cathode 302.

The ion source 100 includes the anode 304 disposed between the cathode 302 and the opening 312, and is configured to be capable of applying an operation mode called an ion pumping mode in which the positive voltage Va is applied to the anode 304 to generate the plasma 310 in the vicinity of the anode 304. In this ion pumping mode, when the plasma 310 is generated, some of the positive ions are also accelerated toward the cathode 302 by the voltage Va (and the emitter voltage Ve) and collide with the cathode 302.

Thus, in either case, the cathode 302 is sputtered by the collision of positive ions as the ion source 100 is used.

Patent document 1: japanese patent laid-open No. 2014-183041

Therefore, in the conventional ion source 100, the cathode 302 is sputtered by the positive ions to generate loss, and therefore, it is necessary to suppress the loss of the cathode 302 and use the ion source 100 for a long time.

Disclosure of Invention

The present invention has been made to solve the above problems, and an object thereof is to suppress loss of an electron emitting portion of a hot cathode due to positive ions.

In order to solve the above problem, an ion source according to claim 1 includes: a plasma generation container; a hot cathode disposed outside the plasma generation container and emitting electrons toward the inside of the plasma generation container; and an emitter power supply that applies a direct-current voltage positive with respect to the plasma generation container to the hot cathode, wherein the ion source includes a cross electric field forming element that forms an electric field in a cross direction that crosses a direction from the electron emitter toward the inside of the plasma generation container in at least a part of a region through which the electrons pass from the electron emitter of the hot cathode to the inside of the plasma generation container.

In the above configuration, the ion source of the present invention includes a cross electric field forming element that forms an electric field in a cross direction crossing a direction from the electron emitter toward the inside of the plasma generation container in at least a part of a region through which electrons pass from the electron emitter of the hot cathode to the inside of the plasma generation container, and therefore an electrostatic force acts on positive ions reaching the region from the electron emitter to the inside of the plasma generation container from the electric field formed by the cross electric field forming element in at least a part of the region.

That is, since the electrostatic force acts on the positive ions in the intersecting direction intersecting the direction from the electron emitter of the hot cathode toward the inside of the plasma generation container, the traveling direction of the positive ions toward the electron emitter of the hot cathode is deflected in the intersecting direction.

Therefore, the positive ions can be deflected in a direction avoiding the electron emitter toward the trajectory of the hot cathode on the electron emitter side, and the positive ions can be prevented from colliding with the electron emitter of the hot cathode, so that sputtering of the electron emitter of the hot cathode can be suppressed.

The intersecting electric field forming element may be formed of at least one pair of intersecting electric field forming electrodes having a potential difference.

The pair of intersecting electric field forming electrodes may be constituted by a positive electrode having a relatively high potential and a negative electrode having a relatively low potential.

Further, a positive electrode power supply may be connected between the positive electrode and the plasma generation container, and the positive electrode power supply may apply a positive dc voltage to the positive electrode with respect to the plasma generation container.

In the above configuration, since a dc voltage positive with respect to the plasma generation container can be applied to the positive electrode, the plasma generation device can also operate in a so-called ion pumping mode in which plasma is generated in the vicinity of the positive electrode.

Further, a negative electrode power supply that applies a negative dc voltage to the negative electrode with respect to the plasma generation container may be further connected between the negative electrode and the plasma generation container.

In the above configuration, the negative electrode power supply is further connected to the negative electrode, whereby the potential difference between the positive electrode and the negative electrode is increased. Therefore, the electrostatic force applied to the positive ions from the electric field in the cross direction is increased, and the trajectories of the positive ions can be deflected more largely.

In addition, a penetrating portion that penetrates in the intersecting direction may be formed in the negative electrode.

In the above configuration, the positive ions after the orbit deflection can pass through the penetration portion, and therefore, the loss of the negative electrode due to the positive ions is suppressed.

Effects of the invention

According to the ion source of the present invention, the loss of the electron emitting portion of the hot cathode due to the positive ions can be suppressed.

Drawings

Fig. 1 is a schematic cross-sectional view showing a first embodiment of an ion source of the present invention.

Fig. 2 is an exploded perspective view showing the intersecting electric field forming electrodes, the hot cathode, and the holder in the first embodiment.

Fig. 3 is a schematic cross-sectional view showing an example of the arrangement of the negative electrode power supply in the first embodiment.

Fig. 4 is a schematic cross-sectional view showing another arrangement example of the negative electrode power supply in the first embodiment.

Fig. 5 is a perspective view showing a modification of the negative electrode in the first embodiment.

Fig. 6 is a schematic plan view showing an example of arrangement of the intersecting electric field forming electrodes in the first embodiment.

Fig. 7 is a schematic cross-sectional view showing a second embodiment of the ion source of the present invention.

Fig. 8 is a schematic cross-sectional view showing a modification of the intersecting electric field forming element in the second embodiment.

Fig. 9 is a schematic cross-sectional view showing a third embodiment of the ion source of the present invention.

Fig. 10 is a sectional view showing a conventional ion source.

Description of the reference symbols

10 ion source

20 plasma generating container

30 hot cathode

30a thermal electron emitting portion

40 crossed electric field forming element

41 crossed electric field forming electrode

42 positive side electrode

43 negative side electrode

44 penetration part

Region R1

D cross direction

E1 crossed electric field

Ee emitter power supply

Ep positive side electrode power supply

En negative side electrode power supply

e electrons

p positive ion

Detailed Description

The ion source of the present invention is used, for example, for extracting an ion beam in an ion implantation apparatus. First, the ion source 10 according to the first embodiment of the present invention will be described.

As shown in fig. 1, the ion source 10 includes: a plasma generation container 20 for generating plasma therein; and a disk-shaped hot cathode 30 disposed outside the plasma generation container 20 and made of tantalum, tungsten, or the like. Further, the side wall portion of the plasma generation container 20 is formed with: a gas inlet 21 for introducing phosphorus trifluoride (PF)₃) Boron trifluoride (BF)₃)、Arsenic hydride (AsH)₃) Waiting for raw material gas g; and an ion beam extraction port 22 through which the ion beam IB is extracted by an extraction electrode (not shown) disposed outside.

An opening 23 is formed in the upper portion of the plasma generation container 20, and the hot cathode 30 is disposed so that one surface side of the hot cathode 30 can be seen from the opening 23. Further, a reflective electrode 24 is disposed on a bottom 26 of the plasma generation container 20 so as to face the hot cathode 30, and a magnetic field B is formed in the plasma generation container 20 in a direction from the hot cathode 30 toward the reflective electrode 24 by a pair of magnets 25 disposed outside the plasma generation container 20.

As shown in fig. 1, the hot cathode 30 is held by a cylindrical holder 31 made of a carbon material so that one surface side thereof is exposed to the plasma generation container 20 side, and a filament 32 is disposed inside the holder 31 so as to be close to the other surface side of the hot cathode 30. That is, the electron emitter 30a of the hot cathode 30 is disposed so as to be exposed into the plasma generation container 20, and as described later, electrons e can be emitted into the plasma generation container 20.

The electron emitter 30a of the hot cathode 30 refers to a region or a structural element of the hot cathode 30 that is heated by the filament 32 and can emit electrons e.

In the ion source 10, a structure is employed in which the entire hot cathode 30 is heated by a filament 32. Therefore, in the hot cathode 30 of the first embodiment, the electron emitter 30a of the hot cathode 30 is understood to mean the whole hot cathode 30.

As shown in fig. 1, a filament power supply Ef for applying a dc voltage Vf to the filament 32 to heat the filament 32 is electrically connected to the filament 32. A cathode power supply Ec to which a dc voltage Vc is applied is electrically connected between the filament 32 and the hot cathode 30 so that the hot cathode 30 side is positive.

The ion source 10 further includes an emitter power source Ee electrically connected between the hot cathode 30 and the plasma generation container 20, and applying a dc voltage Ve, which is negative with respect to the plasma generation container 20, to the hot cathode 30.

The ion source 10 is a so-called side heating type ion source, and heats the filament 32 by passing a direct current from a filament power supply Ef, thereby heating the hot cathode 30. More specifically, thermal electrons (not shown) emitted from the heated filament 32 are accelerated toward the hot cathode 30 by the potential difference Vc applied by the cathode power supply Ec, and collide with the hot cathode 30, thereby heating the hot cathode 30.

As shown in fig. 1, electrons e are emitted from the electron emitter 30a of the heated hot cathode 30, and the electrons e are introduced into the plasma generation container 20 because the electrons e are accelerated in a direction from the electron emitter 30a toward the inside of the plasma generation container 20 by a potential difference Ve formed between the hot cathode 30 and the plasma generation container 20 by the emitter power source Ee. The electrons e introduced into the plasma generation container 20 reciprocate in the direction of the magnetic field B while rotating around the direction of the magnetic field B in the plasma generation container 20, and collide with the molecules of the raw material gas g, thereby generating plasma.

As shown in fig. 1, the ion source 10 further includes a cross electric field forming element 40, and the cross electric field forming element 40 forms an electric field E1, which is an electric field formed in a cross direction D crossing a direction from the electron emitter 30a toward the inside of the plasma generation container 20, in at least a partial region R1 of a region through which the electrons E emitted from the electron emitter 30a of the hot cathode 30 pass from the electron emitter 30a to the inside of the plasma generation container 20.

Since the direction from the hot cathode 30 into the plasma generation container 20 can be said to be the direction of the magnetic field B shown in fig. 1, the intersecting direction D can also be referred to as the direction intersecting the magnetic field B.

As shown in fig. 1, in the present embodiment, the intersecting direction D represents a direction orthogonal to the magnetic field B, but the intersecting direction D is not necessarily limited to a direction orthogonal to the magnetic field B.

As shown in fig. 1, the positive ions p generated during plasma generation are extracted to the outside as the ion beam IB together with the electrons e, but some of the positive ions p are forced from the electric field formed by the voltage Ve of the emitter power supply Ee, for example, in the vicinity of the opening 23 in the plasma generation container 20, and reach the region R1 from the opening 23 of the plasma generation container 20. At this time, the positive ions p are accelerated toward the electron emitter 30a of the hot cathode 30 by the potential difference Ve between the plasma generation container 20 and the hot cathode 30, and at the same time, receive the electrostatic force f1 directed in the cross direction D from the cross electric field E1 formed by the cross electric field forming element 40.

Therefore, the trajectories of the positive ions p toward the electron emitter 30a of the hot cathode 30 are deflected in the cross direction D as indicated by the broken lines in fig. 1, and therefore, the collision between the positive ions p and the electron emitter 30a of the hot cathode 30 is avoided.

As described above, in the ion source 10 of the present embodiment, the trajectories of the positive ions p toward the hot cathode 30 are deflected in the direction avoiding the electron emitter 30a of the hot cathode 30, so that collision between the positive ions p and the electron emitter 30a of the hot cathode 30 can be avoided, and thus sputtering of the electron emitter 30a of the hot cathode 30 can be suppressed. That is, the loss of the electron emitter 30a of the hot cathode 30 due to the positive ions p can be suppressed.

In the present embodiment, as shown in fig. 1 and 2, the intersecting electric field forming element 40 is disposed between the hot cathode 30 and the plasma generating container 20, and is constituted by a pair of intersecting electric field forming electrodes 41 having a potential difference.

As shown in fig. 1 and 2, the pair of intersecting electric field forming electrodes 41 includes a positive electrode 42 having a relatively high electric potential and a negative electrode 43 having a relatively low electric potential, which are arranged to face each other with the hot cathode 30 interposed therebetween.

The positive electrode 42 and the negative electrode 43 are each formed of a conductive plate material having a substantially semicircular arc-shaped cross section, which is formed of carbon or the like, and as shown in fig. 2, the positive electrode 42 and the negative electrode 43 are arranged so as to face each other with their end surfaces slightly separated from each other, and are arranged in a substantially cylindrical shape having a step in the longitudinal direction as a whole.

As shown in fig. 1 and 2, the positive electrode 42 and the negative electrode 43 are assembled to the ion source 10 so as to surround the hot cathode 30 with a predetermined distance from the outer peripheral surface 33 of the hot cathode 30. That is, the positive electrode 42 and the negative electrode 43 are formed in a shape that surrounds substantially the entire outer circumference of the hot cathode 30 and narrows the ion generation container 20 side, and the tips thereof are disposed in the opening 23.

The positive electrode 42 and the negative electrode 43 may have a potential difference so that the intersecting electric field E1 is formed in a direction from the positive electrode 42 toward the negative electrode 43, and a positive voltage is not necessarily applied to the positive electrode 42, and a negative voltage is not necessarily applied to the negative electrode 43.

As shown in fig. 1, a positive electrode power supply Ep that applies a dc voltage Vp positive with respect to the plasma generation container 20 to the positive electrode 42 is electrically connected between the positive electrode 42 and the plasma generation container 20. The negative electrode 43 is electrically connected between the hot cathode 30 and the plasma generation container 20 so as to have the same potential as the hot cathode 30.

Therefore, the ion source 10 has a potential difference Vp + Ve between the positive electrode 42 and the negative electrode 43 and the plasma generation container 20, and a cross electric field E1 is formed between the positive electrode 42 and the negative electrode 43.

In the ion source 10 of the present embodiment, at least a partial region R1 of the region through which the electrons e emitted from the electron emitter 30a of the hot cathode 30 reach the plasma generation container 20 from the electron emitter 30a of the hot cathode 30 may be referred to as a region defined by the electron emitter 30a of the hot cathode 30, the positive electrode 42, and the negative electrode 43.

In the ion source 10 of the present embodiment, since the positive dc voltage Vp is applied to the positive electrode 42, plasma can be generated in the vicinity of the positive electrode 42, and thus a so-called ion pumping mode operation can be performed.

In this case, some of the positive ions p generated when plasma is generated in the vicinity of the positive electrode 42 are accelerated toward the hot cathode 30 by the potential Ve between the hot cathode 30 and the plasma generation container 20, but the trajectories are deflected by the electrostatic force f1 received from the cross electric field E1 formed between the positive electrode 42 and the negative electrode 43, and collision between the hot cathode 30 and the electron emitter 30a is suppressed.

That is, the ion source 10 can apply the ion pumping mode, and can suppress sputtering of the hot cathode 30 by the positive ions p, thereby suppressing the loss of the electron emitter 30a of the hot cathode 30.

Further, a negative electrode power supply En that applies a negative dc voltage, i.e., a negative electrode power supply voltage Vn, to the negative electrode 43 may be electrically connected between the negative electrode 43 and the plasma generation container 20.

As an example of the connection of the negative electrode power supply En, for example, as shown in fig. 3, the negative electrode power supply En may be connected between the negative electrode 43 and the hot cathode 30.

In this case, since the negative electrode power supply En is a dc power supply to which the voltage Vn is applied and which is connected so that the negative electrode 43 side is negative, the potential difference between the positive electrode 42 and the negative electrode 43 can be increased in a state where the voltage of the hot cathode 30 with respect to the plasma generation container 20 is maintained at the predetermined voltage Ve, as compared with a case where the negative electrode power supply En is not provided.

If the voltage Ve is increased only to increase the potential difference between the positive electrode 42 and the negative electrode 43, the force for accelerating the electrons e emitted from the electron emitting portion 30a of the hot cathode 30 into the plasma generation container 20 is increased, and the force for accelerating the positive ions p into the hot cathode 30 is also increased. That is, the positive ions p collide with the electron emitting portions 30a of the hot cathode 30 with a larger energy, and sputter the hot cathode 30.

On the other hand, as shown in fig. 3, in a state where the voltage of the hot cathode 30 with respect to the plasma generation container 20 is kept at the predetermined voltage Ve, the negative electrode power supply En is electrically connected between the negative electrode 43 and the hot cathode 30 so that the negative electrode 43 side is a negative side, whereby the voltage Ve and the negative electrode power supply voltage Vn can be independently adjusted.

That is, the potential difference between the positive electrode 42 and the negative electrode 43 can be increased without changing the force acting on the positive ions p by the voltage Ve generated by the emitter power source Ee.

Therefore, the electrostatic force f1 that the electric field E1 and the positive ions p receive from the electric field E1 can be increased without changing the value of the voltage Ve, and therefore the trajectories of the positive ions p can be deflected more largely. That is, the collision of the positive ions p with the electron emitting portions 30a of the hot cathode 30 is more reliably suppressed.

As another example of the connection of the negative electrode power supply En, as shown in fig. 4, the negative electrode power supply En may be electrically connected between the negative electrode 43 and the plasma generation container 20 so that the negative electrode 43 side is a negative side. In this case as well, the potential difference between the positive electrode 42 and the negative electrode 43 can be increased while maintaining the voltage of the hot cathode 30 with respect to the plasma generation container 20 at the predetermined voltage Ve, as compared with the case where the negative electrode power supply En is not provided, and therefore the trajectory of the positive ions p can be deflected more largely.

The negative electrode power supply En may be connected to increase the potential difference between the positive electrode 42 and the negative electrode 43, and the trajectory of the positive ions p can be deflected more largely by adding the negative electrode power supply En, so that the collision of the positive ions with the electron emitter 30a of the hot cathode 30 can be suppressed more reliably.

Further, by the configuration in which the negative-side electrode power supply En is connected to the negative-side electrode 30 in a state in which the voltage of the hot cathode 42 with respect to the plasma generation container 20 is maintained at the predetermined voltage Ve, the potential difference between the positive-side electrode 43 and the negative-side electrode 43 can be increased to increase the electrostatic force f1 in the direction of the intersecting direction D without changing the force acting on the positive ions p in the direction of the hot cathode 30 due to the voltage Ve.

Therefore, the trajectories of the positive ions p toward the hot cathode 30 can be deflected more toward the intersecting direction D, that is, in a direction avoiding the electron emitting portions 30a of the hot cathode 30, and therefore, the loss of the electron emitting portions 30a of the hot cathode 30 due to the positive ions p can be further suppressed.

In the ion source 10 of the present embodiment, as shown in fig. 1 and 2, the negative electrode 43 is formed with a notch-shaped through portion 44 that penetrates in the intersecting direction D.

As shown in fig. 1, positive ions p whose trajectories toward the electron emitters 30a of the hot cathode 30 are deflected in the cross direction D by the electrostatic force f1 acting from the cross electric field E1 pass through the penetration portion 44. Therefore, since the collision of the positive ions p with the negative-side electrode 43 is suppressed, the loss of the negative-side electrode 43 caused by the positive ions p is suppressed.

As shown in fig. 1, a cover 45 made of a carbon material or the like is disposed outside the penetration portion 44 of the negative electrode 43, and the positive ions p that have passed through the penetration portion 44 collide with the cover 45. Although the cover 45 is lost by the collision of the positive ions p, the cover 45 can be used for a long time by making the thickness dimension sufficiently large. The cover 45 may be arranged or configured to be easily replaced compared with the hot cathode 30 or the intersecting electric field forming electrode 41.

The penetrating portion 44 formed in the negative electrode 43 is not limited to a slit shape, and may be a through-hole shape formed in a part of the negative electrode 43 as shown in fig. 5, and may penetrate in the crossing direction D on the trajectory of the positive ion q after deflection.

The intersecting electric field forming electrode 41 may be constituted by at least one pair of the positive side electrode 42 and the negative side electrode 43, and may be constituted by two positive side electrodes 42 and two negative side electrodes 43, that is, two pairs of the positive side electrode 42 and the negative side electrode 43, as shown in fig. 6(a), for example. As shown in fig. 6(b), the positive electrode 42 and the negative electrodes 43 may be formed.

The ion source 10 according to the first embodiment can suppress the loss of the electron emitter 30a of the hot cathode 30 due to the positive ions p. Therefore, the ion source 10 can be used for a long time as compared with the related art. That is, the lifetime of the ion source 10 can be extended. In addition, when the lifetime of the ion source 10 can be made as long as that of the conventional technique, the hot cathode 30 can be made thin.

Next, an ion source 50 according to a second embodiment of the present invention will be described.

The ion source 50 of the second embodiment includes the plasma generation container 20 having the same configuration as the ion source 10 of the first embodiment, and therefore only the main part of the ion source 50 is shown in fig. 7 and 8 showing the ion source 50 and its modification.

The components having the same structure as the ion source 10 of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and descriptions thereof are omitted.

As shown in fig. 7, the main difference between the structure of the ion source 50 of the second embodiment and the structure of the ion source 10 of the first embodiment is the structure of the intersecting electric field forming element 51.

As shown in fig. 7, the ion source 50 includes a hot cathode 52 formed of tantalum, tungsten, or the like and having an L-shaped cross section. The hot cathode 52 includes an electron emitter 52a formed in a thin plate shape and arranged to face the filament 32, and a cathode wall 52b formed in a plate shape and extending from one end of the electron emitter 52a toward the opening 23 of the plasma generation container 20, and the electron emitter 52a and the cathode wall 52b are integrally formed.

The electron emitting portion 52a of the hot cathode 52 is disposed so as to be close to and face the filament 32, and is heated by the filament 32 to emit electrons e. On the other hand, since the cathode wall 52b is disposed away from the filament 32, it is not heated to a level where electrons e can be emitted. That is, the cathode wall 52b is a part of the hot cathode 52, but does not contribute to the emission of the electrons e.

As shown in fig. 7, the ion source 50 has a thin plate-like deflection electrode 53, and the intersecting electric field forming element 51 in the second embodiment is composed of a cathode wall 52b of the hot cathode 52 and the deflection electrode 53.

The cathode wall 52b of the hot cathode 52 and the deflection electrode 53 are disposed so as to face each other with the electron emitter 52a of the hot cathode 52 interposed therebetween, between the electron emitter 52a of the hot cathode 52 and the plasma generation container 20.

A deflection electrode power supply Eq is electrically connected between the deflection electrode 53 and the plasma generation container 20, and the deflection electrode power supply Eq applies a dc voltage Vq positive to the plasma generation container 20 to the deflection electrode 53. Since the emitter power source Ee is connected between the hot cathode 52 and the plasma generation container 20 in the same manner as the ion source 10 in the first embodiment, a positive voltage Ve is applied to the cathode wall 52b of the hot cathode 52 with respect to the plasma generation container 20.

Therefore, the ion source 50 has a potential difference Vq + Ve between the deflection electrode 53 and the cathode wall 52b with respect to the plasma generation container 20, and thus a cross electric field E2 is formed between the deflection electrode 53 and the cathode wall 52 b.

At this time, since the deflection electrode 53 has a higher potential than the cathode wall 52b, the direction of the cross electric field E2 is a direction from the deflection electrode 53 toward the cathode wall 52 b.

That is, as shown in fig. 7, the ion source 50 forms an electric field formed in a crossing direction D crossing a direction from the electron emitter 52a toward the inside of the plasma generation container 20, that is, a crossing electric field E2, in at least a partial region R2 of a region through which electrons E emitted from the electron emitter 52a of the hot cathode 52 pass from the electron emitter 52a to the plasma generation container 20, by the crossing electric field forming element 51 including the deflecting electrode 53 and the cathode wall 52b of the hot cathode 52.

Further, as in the first embodiment, since the direction from the electron emitter 52a toward the inside of the plasma generation container 20 can be said to be the direction of the magnetic field B, the direction of the intersecting electric field E2 can be said to be the direction intersecting the magnetic field B, and the direction of the intersecting electric field E2 is not limited to the direction orthogonal to the magnetic field B.

The region R2 of at least a part of the region through which the electrons e emitted from the electron emitter 52a of the hot cathode 52 reach the plasma generation container 20 from the electron emitter 52a can be defined by the electron emitter 52a of the hot cathode 52, the cathode wall 52b, and the deflection electrode 53.

As in the case of the ion source 10 of the first embodiment, the ion source 50 of the second embodiment accelerates a part of the positive ions p that reach the region R2 from the opening 23 of the plasma generation container 20 toward the electron emitter 52a of the hot cathode 52 by the potential difference Ve between the plasma generation container 20 and the hot cathode 52, and at the same time, the electrostatic force f2 in the intersecting direction D acts on the positive ions p from the intersecting electric field E2 formed by the intersecting electric field forming element 51.

Therefore, the trajectories of the positive ions p toward the electron emitter 52a of the hot cathode 52 are deflected in the cross direction D as shown by the broken lines in fig. 7, and the collision between the positive ions p and the electron emitter 52a of the hot cathode 52 is avoided.

As described above, in the ion source 50 of the present embodiment, the trajectories of the positive ions p toward the electron emitter 52a of the hot cathode 52 can be deflected in the direction avoiding the electron emitter 52a, that is, in the direction toward the cathode wall 52 b.

That is, since collision of the positive ions p with the electron emission portions 52a of the hot cathode 52 can be avoided, sputtering of the electron emission portions 52a of the hot cathode 52 is suppressed. That is, the loss of the electron emitter 52a of the hot cathode 52 due to the positive ions p is suppressed, and the ion source 50 can be used for a long time.

In addition, in the ion source 50 of the second embodiment, the positive ions p after orbital deflection collide with the cathode wall 52b of the hot cathode 52, and the cathode wall 52b is sputtered by the positive ions p.

Since the electron emitter 52a of the hot cathode 52 needs to be heated sufficiently to emit the electrons e, it is difficult to increase the thickness dimension T1 of the electron emitter 52 a.

However, since the cathode wall 52b does not contribute to the emission of the electrons e, it is sufficient to ensure that the thickness dimension T2 of the cathode wall 52b is sufficiently large to withstand the loss due to the sputtering of the positive ions p.

That is, by securing the thickness T2 of the cathode wall 52b to be larger than the thickness T1 of the electron emitter 52a of the hot cathode 52, the ion source 50 can be used for a longer time.

Further, by changing the deflection electrode voltage Vq, the cross electric field E2 and the electrostatic force f2 acting on the positive ions q can be adjusted, and thereby the degree to which the trajectories of the positive ions p are deflected can also be adjusted.

The electron emitter 52a and the cathode wall 52b of the hot cathode 52 are integrally formed, but may be separate members as long as the emitter power source E can apply the emitter voltage Ve to the cathode wall 52 b.

Next, a modification of the ion source 50 according to the second embodiment will be described.

The intersecting electric field forming element 51 of the ion source 50 according to the second embodiment is composed of the cathode wall 52b of the hot cathode 52 and the deflection electrode 53 to which the deflection electrode power source Eq is connected, but the deflection electrode 53 is not necessarily used.

As shown in fig. 8, the intersecting electric field forming element 55 in the modification of the ion source 50 is composed of the cathode wall 52b of the hot cathode 52 and the opening forming portion 54 having the same potential as the plasma generation container 20. The opening forming portion 54 may be a member integral with the opening 23, that is, a portion itself where the opening 23 is formed, or may be another member attached to the opening 23 so as to have the same potential as the plasma generation container 20.

The opening forming portion 54 of the intersecting electric field forming element 55 is at the same potential as the plasma formation container 20, and an emitter voltage Ve which is negative with respect to the plasma formation container 20 is applied to the cathode wall portion 52b of the hot cathode 52.

Therefore, the opening-forming portion 54 and the cathode wall portion 52b have a potential difference Ve, and the electric field E3 is formed in the direction of the intersecting direction D, and the electrostatic force f3 is applied to the positive ion p, whereby the positive ion p can be deflected toward the orbit of the electron emitter 52a of the hot cathode 52 in the intersecting direction D.

That is, the loss of the electron emitting portion 52a of the hot cathode 52 due to the positive ions p can be suppressed.

Next, an ion source 60 according to a third embodiment of the present invention will be described.

As shown in fig. 9(a), an ion source 60 according to a third embodiment of the present invention is the same as the ion source 10 according to the first embodiment except for the structure of the hot cathode 30 and the arrangement position of the filament 32 in the ion source 10 according to the first embodiment. Therefore, fig. 9(a) shows only the main part of the modification, and the same components as those of the ion source 10 are denoted by the same reference numerals as those of the first embodiment, and the description thereof is omitted.

As shown in fig. 9(a), the ion source 60 includes a hot cathode 61 including an electron emitter 61a and a barrier 61 b.

The electron emitter 61a is a portion that emits electrons e by being heated by the filament 32. The barrier portion 61b and the flat plate-like electron emitting portion 61a are formed continuously in the direction intersecting the direction D. The stopper 61b is formed so that the thickness thereof gradually increases toward the intersecting direction D. The filament 32 is disposed at a position facing the electron emitter 61 a.

In other words, the filament 32 is arranged offset from the position in the first embodiment in the direction opposite to the intersecting direction D, and the portion of the hot cathode 61 that is arranged so as to face the filament 32 and can emit electrons e by being heated by the filament 32 is the electron emitting portion 61 a. On the other hand, a portion which is separated from the filament 32 and is less likely to be heated by the filament 32 and thus does not contribute to the emission of the electrons e is the barrier portion 61 b.

As shown in fig. 9(a), as in the first embodiment, electrons e emitted from the electron emitting portion 61a of the hot cathode 61 are accelerated by the emitter voltage Ve and introduced into the plasma generation container 20, while some of the positive ions p are accelerated toward the hot cathode 61.

At this time, as in the first embodiment, the electrostatic force f1 from the intersecting electric field E1 acts, and the orbit of the positive ion p is deflected toward the intersecting direction D. Here, in the ion source 10 of the first embodiment, the trajectories of the positive ions p are deflected so as to pass through the through portion 44, but a part of the positive ions p whose trajectories are not sufficiently deflected collide with the hot cathode 61.

However, in the ion source 60, a barrier 61b that does not contribute to the emission of electrons e is formed on the cross direction D side of the hot cathode 61, and the positive ions p collide with the barrier 61b to sputter the barrier 61 b. That is, in the ion source 60, the positive ions p are also suppressed from colliding with the electron emitting portions 61a of the hot cathode 61, and thus the loss of the electron emitting portions 61a of the hot cathode 61 due to the positive ions p can be suppressed.

Further, the stopper portion 61b is formed so as to gradually increase in thickness in the crossing direction D, and is therefore less likely to be worn. That is, the ion source 60 can be used for a long time by sufficiently securing the thickness dimension of the stopper 61 b.

Further, most probably due to the loss of the hot cathode 61, when the loss of the hot cathode 61 progresses to generate holes penetrating the hot cathode 61, the positive ions p are accelerated toward the filament 32 by the cathode voltage Vc, and the filament 32 is sputtered. However, in the ion source 60 of the third embodiment, even when the aperture penetrating the hot cathode 61 is formed in the stopper 61b, the stopper 61b is located at a position shifted from the filament 32 toward the intersecting direction D, and therefore, the positive ions p entering the filament 32 through the aperture can be prevented from traveling toward the filament 32.

Therefore, in the third embodiment, the barrier 61b of the hot cathode 61 is formed to have a larger thickness than the electron emitter 61a, but the ion source 60 can be continuously used even when a hole penetrating the barrier 61b is formed.

Therefore, the thickness dimension of the barrier portion 61b may be configured to be the same as the thickness dimension of the electron emitter 61 a.

The same applies to the arrangement of the hot cathode 52 and filament 32 of the ion source 50 in the second embodiment.

That is, as shown in fig. 9(b), the hot cathode 52 of the ion source 50 according to the second embodiment may be configured to include an electron emitting portion 71a, a cathode wall portion 71b, and a shield wall portion 71c formed at a connecting portion connecting the electron emitting portion 70a and the cathode wall portion 71b, and the ion source 70 may be configured by disposing the filament 32 at a position facing the electron emitting portion 70 a. In this case, the protective wall 71c is also provided to prevent the formation of a through hole by the positive ion sputtering, and therefore the protective wall 71c is not necessarily required.

It is needless to say that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

Claims

1. An ion source is provided with: a plasma generation container; a hot cathode disposed outside the plasma generation container and emitting electrons toward the inside of the plasma generation container; and an emitter power supply for applying a direct current voltage positive with respect to the plasma generation container to the hot cathode,

the ion source includes a cross electric field forming element that forms an electric field in a cross direction that crosses a direction from the electron emitter toward the inside of the plasma generation container in at least a part of a region through which the electrons pass from the electron emitter of the hot cathode into the inside of the plasma generation container.

2. The ion source of claim 1,

the intersecting electric field forming element is composed of at least one pair of intersecting electric field forming electrodes having a potential difference.

3. The ion source of claim 2,

the pair of crossed electric field forming electrodes is composed of a positive side electrode having a relatively high electric potential and a negative side electrode having a relatively low electric potential.

4. The ion source of claim 3,

a positive electrode power supply is connected between the positive electrode and the plasma generation container, and applies a positive dc voltage to the positive electrode with respect to the plasma generation container.

5. The ion source of claim 3 or 4,

a negative electrode power supply that applies a dc voltage negative with respect to the plasma generation container to the negative electrode is further connected between the negative electrode and the plasma generation container.

6. The ion source of claim 3 or 4,

the negative electrode is formed with a penetrating portion penetrating in the intersecting direction.

7. The ion source of claim 5,