JP2001160368A - Ion source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To aim at improving performance of the ion source. SOLUTION: A pair of mirror magnets 10 in the ion source are respectively provided by containing a coil or a permanent magnet in a yoke 11. A side yoke 11-1 on the mirror magnets at the pullout electrode side was equipped with an opening to let the ion beam pass, and the shape of the opening was made into rotationally asymmetric shapes such as oval and ellipse. This smoothes the flow of the ion beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an ion source suitable for an ion source for an ion implantation apparatus.

[0002]

2. Description of the Related Art A schematic configuration of an ion source will be described with reference to FIG. This ion source 100 is provided between a plasma chamber 101 having a window for introducing microwaves, a pair of mirror magnets 102 disposed on the outer periphery of both ends of the plasma chamber 101, and between these mirror magnets 102. A plasma chamber for introducing microwaves into the plasma chamber;
A plasma is generated in the plasma chamber 1 and an ion beam is extracted by an extraction electrode provided at one end of the plasma chamber 101.

A gas for generating ions is introduced into the plasma chamber 101 from a supply port 104 provided at the other end on the center axis of the plasma chamber 101. Microwaves from a microwave power supply with an RF oscillator are also introduced into the plasma chamber 101 through the waveguide 103.

The plasma chamber 101 has a generally cylindrical shape, and a waveguide 103 is connected to a side surface of the plasma chamber 101 so that microwaves are introduced into the plasma chamber 101 from its radial direction. An RF window is inserted into a portion where the waveguide 103 and the plasma chamber 101 are connected. The RF window transmits microwaves from the atmosphere into the plasma chamber 101, but maintains the vacuum of the plasma chamber 101.

[0005] The pair of mirror magnets 102 are for creating a mirror magnetic field in the plasma chamber 101, and are usually realized by solenoid coils. The mirror magnet 102 may be constituted by a plurality of rod-shaped permanent magnets.

[0006] A casing for extracting an ion beam is provided at one end of the plasma chamber 101, and an extraction electrode and an anode electrode are provided in the casing.

[0007] Such an ion source 100 is applied to an ion implantation apparatus.
No. 343324.

[0008]

SUMMARY OF THE INVENTION The present invention seeks to improve the performance of various parts of the above-mentioned ion source by making various improvements.

[0009] The present invention particularly seeks to provide an ion source that can facilitate the incorporation of other components.

Another object of the present invention is to provide an ion source capable of reducing the required space around the apparatus.

[0011]

According to a first aspect of the present invention, there is provided:
A plasma chamber having an inner wall and an outer wall and having a window for introducing microwaves, a pair of mirror magnets provided by coils or permanent magnets disposed on outer walls at both ends of the plasma chamber, and the pair of mirror magnets A waveguide for introducing the microwave into the plasma chamber, the plasma being generated in the plasma chamber, and an ion beam being provided at one end of the plasma chamber. In the ion source configured to be extracted by the electrodes, the pair of mirror magnets are respectively
The coil or the permanent magnet is housed in a yoke,
An opening for passing the ion beam is provided on a yoke end surface of the mirror magnet on the extraction electrode side, and the opening has a rotationally asymmetric shape such as an ellipse or an ellipse.

The shape of the opening may be a shape corresponding to the slit shape of the extraction electrode.

According to a second aspect of the present invention, the cross-sectional shape of the outer wall surface is circular, the cross-sectional shape of the inner wall surface is a circular shape similar to the cross-sectional shape of the outer wall surface, and the cross-sectional shape of the inner wall surface is The plasma chamber is formed so as to be eccentric with respect to the cross-sectional shape of the outer wall surface.

The cross-sectional shape of the inner wall surface is circular,
The cross-sectional shape of the outer wall surface may be different from the cross-sectional shape of the inner wall surface, and the plasma chamber may be formed to have a concentric relationship.

The cross section of the outer wall surface is circular,
The cross-sectional shape of the inner wall surface may be different from the cross-sectional shape of the outer wall surface, and the plasma chamber may be formed to have a concentric relationship.

According to a third aspect of the present invention, a cylindrical body is further provided inside the plasma chamber, the cylindrical body extending from a position corresponding to the two inner walls on the short axis side of the waveguide toward the end of the plasma chamber. It is characterized by having been formed.

As a modification of the third embodiment, a partition is formed inside the plasma chamber at at least one of two positions corresponding to the two inner walls on the short axis side of the waveguide so as to extend along the circumferential direction. A body may be provided.

Further, the plasma chamber may have a closed-end cylindrical shape having a closed end opposite to the extraction electrode.

In a fourth embodiment of the present invention, each of the pair of mirror magnets is a mirror electromagnet having a coil housed in the yoke, and the coil is formed by winding a winding into a single-layer ring shape. In addition, the inner lead wire and the outer lead wire are led out of the yoke, and the yoke has a groove or a through hole for leading the inner lead wire. It is characterized by being formed.

A fifth embodiment of the present invention is characterized in that the window for introducing microwaves has a horn shape such that the diameter increases toward the inside.

According to a sixth aspect of the present invention, in the case where each of the pair of mirror magnets includes a permanent magnet housed in the yoke, the permanent magnet of the mirror magnet on the side opposite to the extraction electrode is penetrated. A coaxial line is coupled to the waveguide.

As a modified example of the sixth embodiment, the waveguide is formed by bending the waveguide toward the mirror magnet opposite to the extraction electrode, and the bent waveguide portion is opposite to the extraction electrode. May be led out of the mirror magnet through a notch provided in the permanent magnet of the mirror magnet on the side.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram of the mirror magnet 10 on the downstream side, that is, the extraction electrode 110 (FIG. 2) side, as viewed from the extraction electrode 110 side, of a pair of mirror magnets in an ECR ion source (hereinafter, referred to as an ion source). . In the following description, the terms “upstream” and “downstream” are used with respect to the flow direction of ions. Here, the mirror magnet 10 is configured by housing a solenoid coil 12 in a yoke 11. The yoke 11 has two side yokes 11-1 and 11-2 and an outer yoke 11-3.
And a through hole for passing the plasma chamber 20 is formed in the side yoke 11-2 on the upstream side. on the other hand,
One end of the plasma chamber 20 is in contact with the inner surface of the downstream side yoke 11-1.
1 is provided with an opening 11-1a for passing an ion beam. Reference numeral 11-4 in FIG. 1 denotes a terminal for energizing the solenoid coil 12, and reference numeral 120 in FIG. 2 denotes an anode.

The present embodiment is characterized in that the shape of the opening 11-1a is a rotationally asymmetric shape. here,
An elliptical shape is adopted as the rotationally asymmetric shape. In particular, the opening inner diameter in the direction (vertical direction) corresponding to the longitudinal direction of the vertically elongated slit of the extraction electrode 110 is increased to be a longer diameter, and the opening inner diameter in the direction (horizontal direction) perpendicular to the longitudinal direction of the slit of the extraction electrode 110 is Reduce to a short diameter. Furthermore, the directions of the major axis and the minor axis are set to the specific directions of the magnetic field generated by the multipole. Of course, the major and minor diameters are larger than the cross-sectional shape of the ion beam (the hatched portion in FIG. 1). In addition, as other examples of the rotationally asymmetric shape, an oval shape, a rectangular shape, or the like can be considered. For example, the shape of the opening 11-1a may correspond to the cross-sectional shape of the extraction electrode 110.

More specifically, the cylindrical body forming the plasma chamber 20 is formed such that its inner wall has a cross-sectional shape of an opening 11-.
It may be manufactured to have the same shape as 1a.

The effects of this embodiment include the following.

Since the distribution of the mirror magnetic field in the portion near the central axis of the plasma chamber 20 does not change much and there is almost no component in the radial direction of the magnetic field, the distribution of the magnetic field is almost the same as that of a general circular opening. does not change. Leader electrodes having vertically elongated slits can be easily incorporated. Since there is no extra space between the ion beam and the aperture, the flow of the ion beam is smooth.

A second embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a cross-sectional shape of the plasma chamber 20. The plasma chamber 20 has an outer wall surface (that is, an outer peripheral surface) 20-1 and an inner wall surface (that is, an inner peripheral surface) 20-1.
0-2. In this embodiment, the cross-sectional shape of the outer wall surface 20-1 is circular, the cross-sectional shape of the inner wall surface 20-2 is a circular shape similar to the cross-sectional shape of the outer wall surface 20-1, and the inner wall surface 20-2 is the outer wall surface 20-1. The plasma chamber 20 is formed so as to be eccentric with respect to -1. This is because if the thickness of the plasma chamber 20 is reduced uniformly, it is expanded to the space where there is no plasma, and R
While the F window 31 and the passage 20a for water cooling become cramped,
This is based on the fact that a uniform thickness reduces the plasma.

The effects of the second embodiment are as follows.

Cooling water is easy to flow. That is, a passage 20 for passing cooling water through a thick portion of the plasma chamber 20.
It becomes easy to make a. It is easy to make an RF window for microwave introduction. That is, it becomes easy to form the RF window 31 in the thick portion of the plasma chamber 20.

FIGS. 5 to 7 each show a modification of the second embodiment. In these modifications, the cross-sectional shape of the outer wall surface 20-1 of the plasma chamber 20 is circular, and the cross-sectional shape of the inner wall surface 20-2 is different from the cross-sectional shape of the outer wall surface 20-1. Thus, the plasma chamber 20 is formed. For example, in the modification of FIG. 5, the cross-sectional shape of the inner wall surface 20-2 is elliptical, and in the modification of FIG. 6, the cross-sectional shape of the inner wall surface 20-2 is substantially oval. Further, in the modification of FIG. 7, the cross-sectional shape of the inner wall surface 20-2 is substantially rectangular. The inner wall surface 20-2 does not need to have the same cross-sectional shape over the entire length in the axial direction.

The effects of these modifications are as follows.

For the same reason as in the second embodiment, it is easy to flow cooling water. For the same reason as in the second embodiment, it is easy to create an RF window for introducing microwaves. By setting the cross-sectional shape of the inner wall surface 20-2 to a shape similar to the opening 11-1a of the yoke 11 described in the first embodiment, a useless space in the plasma chamber 20 is omitted, and the plasma chamber is used. Function can be enhanced.

FIGS. 8 to 10 show other modifications of the second embodiment. In these modifications, the cross-sectional shape of the inner wall surface 20-2 of the plasma chamber 20 is circular, the cross-sectional shape of the outer wall surface 20-1 is a rotationally asymmetric shape different from the cross-sectional shape of the inner wall surface 20-2, and concentric. The plasma chamber is formed so as to be related. For example, in the modification of FIG. 8, the cross-sectional shape of the outer wall surface 20-1 is substantially oval, and in the modification of FIG.
1 has an elliptical cross-sectional shape. Further, FIG.
In the modification, the cross-sectional shape of the outer wall surface 20-1 is substantially rectangular.

According to these modifications, the same effects as those of the modifications shown in FIGS. 5 to 7 can be obtained, and positioning in the rotation direction about the axis of the plasma chamber 20 can be easily performed.

The combination of the modification of the second embodiment and another modification, that is, the outer wall surface 20-1 and the inner wall surface 20
-2 may both have a rotationally asymmetric shape.

Referring to FIGS. 11 to 13, a third embodiment of the present invention will be described.
An embodiment will be described. In the third embodiment, the waveguide 3 is further provided on the inner diameter side of the plasma chamber 20.
A pair of cylindrical bodies 40 are formed extending from positions corresponding to the two inner walls on the short axis side of the opening 0 to the end portions of the plasma chamber 20, respectively.

In the third embodiment, a space having the same length as the inner width of the opening of the waveguide 30 in the long axis direction is formed in the plasma chamber 20. In this manner, the reflection of microwaves is reduced as much as possible, and the plasma (or E
The microwave can be guided to near (CR resonance point).

Here, the cylindrical body 40 is formed by forming the downstream cylindrical body 40 of the pair of cylindrical bodies 40 integrally with the plasma chamber 20 and separately forming the upstream cylindrical body 40. This is inserted and fixed from the opening on the upstream side of the plasma chamber 20.

The end face of the plasma chamber 20 on the side opposite to the extraction electrode 110 may be closed (that is, the end face may be closed).
Cylindrical shape with bottom). The plasma chamber 20 is longer than the opening of the waveguide 30 both upstream and downstream.

According to the third embodiment, the plasma generated in the plasma chamber 20 can be prevented from approaching the inner periphery of the RF window 31, and the inner surface of the RF window 31 is less likely to be contaminated.

A modification of the third embodiment will be described with reference to FIGS. In this modification, partitioning bodies 41 are provided on the inner wall side of the plasma chamber 20 at positions corresponding to the two inner walls on the short axis side of the opening of the waveguide 30 so as to extend in the circumferential direction.

The partition member 41 is disposed at a position in the plasma chamber 20 that partitions a portion corresponding to the inner width of the long axis of the opening of the waveguide 30. As shown in FIG. 14, it may be provided at two locations on the upstream side and the downstream side, or may be provided at only one location if one of them matches the inner width of the waveguide 30. The partition body 41 is desirably integrated with the plasma chamber 20 for cooling purposes, but may be separate.

The partition member 41 has a plate shape (for example, a thickness of 1 mm).
Plate or a cylindrical shape having a certain thickness (for example, about the diameter of the partition 41). The partition body 41 has an opening, and the sectional shape thereof may be a substantially donut shape or a substantially C shape with a part cut off in the circumferential direction. The size of the opening is arbitrary, but the ECR in the plasma chamber 20 is
Make it larger than the maximum diameter of the zone by one turn (at least about 5 mm). It is not necessary that the upstream and downstream partitions 41 have the same shape and arrangement.

In this modification, the partition 41 is placed inside the plasma chamber 20 so that
It can be considered that the waveguide 30 is extended to the inside of the plasma chamber 20. The width W1 of the central portion of the partitioned space is the same as the width W2 on the inner wall side of the waveguide 30.

According to this modification, the same effects as in the third embodiment can be obtained.

Referring to FIGS. 16 and 17, the fourth embodiment of the present invention will be described.
An embodiment will be described. In the fourth embodiment, each of the pair of mirror magnets is a mirror electromagnet formed by housing the coil 50 in a yoke. In particular, coil 5
Numeral 0 is different from the solenoid coil in that the winding is wound in a single-layer ring shape and the inner lead wire 51 and the outer lead wire 52 are led out of the yoke. . A groove 53-1 for leading out the lead wire 51 on the inner peripheral side is formed on the inner wall of one of the two side yokes (indicated by 53 here) of the yoke. In addition, instead of the groove 53-1,
A through hole may be provided in the side yoke 53 for passing the lead wire 51 on the inner peripheral side.

As described above, in the fourth embodiment, in order to reduce the thickness of the coil 50 on the downstream side of the pair of mirror electromagnets, only a single layer of pancake shape is used. The side yoke made of iron surrounding the coil 50 is provided with a groove or a through hole in a part thereof to guide the lead wire 51 drawn from the inner peripheral side of the coil 50 to the outside. As a result, the thickness of the coil 50 can be reduced. Even if grooves and through holes are provided in the side yoke 53, almost the same magnetic field can be generated as when there is no groove or through holes.

Referring to FIGS. 18 and 19, a fifth embodiment of the present invention will be described.
The embodiment will be described. In the fifth embodiment,
RF for microwave introduction in plasma chamber 20
The window 31 is characterized in that it has a horn shape whose diameter increases toward the inside. The RF window 31
Alternatively, the tip of the waveguide 30 may be provided by soldering.

Referring to FIG. 20, a sixth embodiment of the present invention will be described. The sixth embodiment is applied to a case where each of a pair of mirror magnets 10 includes a bar-shaped permanent magnet housed in a yoke 11. Particularly, the present invention is characterized in that the coaxial line 61 is coupled to the waveguide 30 by penetrating the yoke 11 of the mirror magnet 10 on the side opposite to the extraction electrode and the permanent magnet therein.

When microwaves are introduced into the plasma chamber 20, there are many restrictions on securing a radial space in the ion source of the implanter. In such a case, an ion source employing a mirror magnet made of a permanent magnet does not require a large space in the radial direction of the apparatus by using the coaxial line 61 as shown in FIG. Even if a permanent magnet is provided with a through-hole, the magnetic field maintains almost rotational symmetry, and the influence is small. In particular, when the RF power is about 300 W or less, the mirror magnet 10 is converted into a coaxial line 61 as shown in FIG.
It can be easily penetrated while keeping the cross section of the large.

A modification of the sixth embodiment will be described with reference to FIG. In this modification, the waveguide 30 is formed by bending the waveguide 30 on the side of the mirror magnet 10 opposite to the extraction electrode, and the bent waveguide portion is combined with the yoke 11 and the permanent magnet of the mirror magnet 10 on the side opposite to the extraction electrode. It is led out of the mirror magnet 10 through a notch 70 provided in the magnet. Such a waveguide may be integrated or may be configured to be split.

Although the present invention has been described with reference to various embodiments, furthermore, for example, when the strength of the mirror magnetic field is fixed, it is difficult to ignite the arc. .

[0054]

As described above, the present invention has been described by exemplifying a plurality of embodiments. However, the ion source according to the present invention can easily incorporate other constituent members, for example, an extraction electrode and a cooling system.
Also, the required space around the device is small.

[Brief description of the drawings]

FIG. 1 is a diagram of a mirror magnet to which a first embodiment of the present invention is applied, viewed from a lead electrode side.

FIG. 2 is a longitudinal sectional view of the mirror magnet of FIG.

FIG. 3 is a cross-sectional view of the mirror magnet of FIG. 1;

FIG. 4 is a diagram showing a cross-sectional shape of a plasma chamber to which a second embodiment of the present invention is applied.

FIG. 5 is a diagram showing a modification of the second embodiment in FIG. 4;

FIG. 6 is a diagram showing a modification of the second embodiment in FIG. 4;

FIG. 7 is a diagram showing a modification of the second embodiment in FIG. 4;

FIG. 8 is a diagram showing another modification of the second embodiment in FIG. 4;

FIG. 9 is a diagram showing another modification of the second embodiment in FIG. 4;

FIG. 10 is a diagram showing another modification of the second embodiment in FIG. 4;

FIG. 11 is a sectional view of a plasma chamber to which a third embodiment of the present invention is applied.

FIG. 12 is a view of the plasma chamber of FIG. 11 as viewed from a lead electrode side.

FIG. 13 is a sectional view taken along line AA ′ in FIG. 11;

FIG. 14 is a diagram showing a modification of the third embodiment in FIG. 11;

FIG. 15 is a sectional view taken along line BB ′ of FIG. 14;

FIG. 16 is a diagram showing a coil in a mirror magnet to which the fourth embodiment of the present invention is applied.

17 is a diagram showing an inner wall side of a side yoke in a yoke for accommodating the coil of FIG. 16;

FIG. 18 is a cross-sectional view showing a part of a plasma chamber to which a fifth embodiment of the present invention is applied.

19 is a diagram showing a cross-sectional shape of the plasma chamber shown in FIG.

FIG. 20 illustrates an EC to which the sixth embodiment of the present invention is applied.
FIG. 7A is a diagram for explaining an R ion source, in which FIG.
Figure (b) is a side view.

FIGS. 21A and 21B are views for explaining an ECR ion source according to a modified example of the embodiment shown in FIG. 20, wherein FIG. 21A is a front view and FIG. 21B is a side view.

FIG. 22 is a diagram showing a schematic configuration of a conventional ion source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mirror magnet 11 Yoke 11-1, 11-2 Side yoke 11-1a Opening 11-3 Outer peripheral yoke 11-4 Current-carrying terminal 12 Solenoid coil 20 Plasma chamber 20a Cooling water passage 20-1 Outer wall surface 20-2 Inside Wall surface 30 Waveguide 31 RF window 40 Cylindrical body 41 Partition body 61 Coaxial line 70 Notch 110 Leader electrode 120 Anode electrode

Claims (12)

[Claims] 1. A plasma chamber having an inner wall surface and an outer wall surface and having a window for introducing microwaves, a pair of mirror magnets provided by coils or permanent magnets disposed on outer walls at both ends of the plasma chamber, A waveguide provided between the pair of mirror magnets for introducing the microwave into the plasma chamber, generating plasma in the plasma chamber, and applying an ion beam to one end of the plasma chamber. In the ion source that is extracted by an extraction electrode provided on the side, the pair of mirror magnets are each formed by accommodating the coil or the permanent magnet in a yoke, and the ion magnet is provided on a yoke end surface of the mirror magnet on the extraction electrode side. An opening for passing the beam is provided, and the shape of the opening is a rotationally asymmetric shape such as an ellipse and an ellipse. Ion source, characterized in that. 2. The ion source according to claim 1, wherein said opening has a shape corresponding to a slit shape of said extraction electrode. 3. The ion source according to claim 1, wherein the outer wall has a circular cross section, the inner wall has a circular cross section similar to the outer wall, and the inner wall has a cross section. An ion source, wherein the plasma chamber is formed such that the shape thereof is eccentric with respect to the cross-sectional shape of the outer wall surface. 4. The ion source according to claim 1, wherein the cross-sectional shape of the inner wall surface is circular, and the cross-sectional shape of the outer wall surface is different from the cross-sectional shape of the inner wall surface, and has a concentric relationship. An ion source, wherein the plasma chamber is formed. 5. The ion source according to claim 1, wherein a cross-sectional shape of the outer wall surface is circular, and a cross-sectional shape of the inner wall surface is different from the cross-sectional shape of the outer wall surface, and has a concentric relationship. An ion source, wherein the plasma chamber is formed. 6. The ion source according to claim 1, further comprising: an inner wall side of the plasma chamber; and an end side of the plasma chamber from a position corresponding to two inner walls on a short axis side of the waveguide. An ion source characterized by forming an elongated cylinder. 7. The ion source according to claim 1, wherein the inner wall side of the plasma chamber is further provided with at least one of two positions corresponding to the two inner walls on the short axis side of the waveguide in a circumferential direction. An ion source characterized in that a partition body is provided along the same. 8. The ion source according to claim 1, wherein the plasma chamber has a bottomed cylindrical shape having an end opposite to the extraction electrode closed. 9. The ion source according to claim 1, wherein each of the pair of mirror magnets is a mirror electromagnet in which a coil is housed in the yoke, and the coil has a single-layer ring shape. The inner lead and the outer lead are led out of the yoke, and the yoke has grooves or through holes for leading the inner lead. An ion source, characterized in that is formed. 10. The ion source according to claim 1, wherein the window for introducing microwaves has a horn shape such that its diameter increases inward. 11. The ion source according to claim 1, wherein each of the pair of mirror magnets includes a permanent magnet housed in the yoke, and the permanent magnet of the mirror magnet on the opposite side of the extraction electrode is penetrated. An ion source wherein a coaxial line is coupled to the waveguide. 12. The ion source according to claim 1, wherein each of the pair of mirror magnets includes a permanent magnet housed in the yoke, and the waveguide is provided on the mirror magnet side opposite to the extraction electrode. An ion source characterized in that a bent waveguide portion is formed, and a bent waveguide portion is led out of the mirror magnet through a cutout provided in a permanent magnet of the mirror magnet on the side opposite to the extraction electrode.