JP4249826B2 - Multipolar permanent magnet device for ECR - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multipole permanent magnet device, and more particularly to a multipole permanent magnet device suitable for an ECR (electron cyclotron resonance) ion source device.
[0002]
[Prior art]
This type of multipolar permanent magnet device is usually provided by assembling a permanent magnet to a cylindrical frame body at intervals in the circumferential direction, and further combining a yoke. In this type of multipolar permanent magnet device, the arrangement of permanent magnet blocks and yokes may not be the same in any cross section of the multipolar permanent magnet, but may be changed depending on the location. It is not always constant. In the conventional method, when the outer diameter changes, it is difficult to manufacture a small multipolar permanent magnet at the same time while maintaining the mechanical strength.
[0003]
[Problems to be solved by the invention]
Conventional multipolar permanent magnets have an outer frame that is cut out as a single piece, and permanent magnet blocks are placed inside such that they are supported by each other like an arch structure of a stone bridge, and fixed with an adhesive. It is a method to do. The problem with such a multipolar permanent magnet is that the mechanical strength decreases when the outer frame is divided. When the outer frame is configured by division, when the adhesive force deteriorates with the passage of time or usage conditions, the stronger the magnetic force of the permanent magnet, the easier it is to break and the fragments may scatter.
[0004]
If the conventional method cannot make a single piece, the mechanical strength is insufficient. Alternatively, in order to maintain the mechanical strength, there is a method of attaching something like a flange for a firm connection, but the size increases.
[0005]
Therefore, an object of the present invention is to provide a multipolar permanent magnet device that can be reduced in thickness in the radial direction while maintaining mechanical strength.
[0006]
[Means for Solving the Problems]
According to the present invention, Placed outside the plasma chamber A first multi-pole permanent magnet assembly comprising a plurality of rod-shaped permanent magnets is disposed on the outer peripheral surface of the cylindrical base frame so as to be arranged in the direction of the central axis of the base frame; Covering the outside of the plurality of rod-shaped permanent magnets in the first multipole permanent magnet assembly is a yoke body that is a cylindrical outer frame body of approximately the same length as this, End frames are provided at both ends of the base frame, and the end frames Both A second multipolar permanent magnet assembly made up of a plurality of rod-shaped permanent magnets is disposed on the outside, and the rod-shaped permanent magnets constituting the first multipolar permanent magnet assembly are orthogonal to the central axis of the base frame. The first multipole permanent magnet is formed in a cross section perpendicular to the central axis of the end frame by a rod-like permanent magnet that forms a main magnetic closed circuit in the cross section and constitutes the second multipole permanent magnet assembly. An end magnetic closed circuit of the same polarity as the assembly is formed. , A mirror magnet is disposed in the vicinity of each outer portion of the second multipole permanent magnet assembly, and the yoke body is interposed between the mirror magnets on both sides, thereby introducing a microwave introduction waveguide For connection to the plasma chamber, the base frame and the yoke body, at least one connection portion is provided in the triple structure, and the waveguide is connected to the first multipolar permanent magnet. The plasma chamber, the base frame, and the yoke body are each positioned between the rod-like permanent magnets in the assembly, and long holes parallel to the central axis direction thereof are formed, and the long hole portion of the plasma chamber is An RF window is provided in the connection portion so that microwaves are introduced from the radial direction of the plasma chamber, and the plurality of rod-like permanent magnets in the first multipole permanent magnet assembly has a number of magnetic poles N (N The rod-shaped permanent magnets belonging to each group have their magnetic pole directions in a plane perpendicular to the central axis of the base frame. And the adjacent pairs in the circumferential direction of the base frame are configured to have opposite magnetic poles, and the plurality of rod-like permanent magnets in the second multipole permanent magnet assembly are The magnetic poles in the plane perpendicular to the central axis of the base frame are made to have the same orientation so that the combination of the same magnetic poles as that of the N sets of magnet assemblies divided in one multipolar permanent magnet assembly is obtained. N sets of rod-shaped permanent magnets arranged so that adjacent magnetic poles spaced apart from each other in the circumferential direction of the end frame are opposite to each other, and the N poles between the N sets of rod-shaped permanent magnets, and the magnetic poles are in the end frame Only facing the circumferential direction Consisting of N sets of rod-shaped permanent magnets arranged the like poles adjacent with respect to the circumferential direction are opposite directions to each other An ECR multipolar permanent magnet device is provided.
[0008]
A space is provided between adjacent sets of the plurality of rod-shaped permanent magnets in the first multipolar permanent magnet assembly in the circumferential direction of the base frame, and the base frame corresponding to the space and A space is also formed in the yoke body.
[0009]
The first multi-pole permanent magnet assembly is composed of a plurality of magnet groups in each of the rod-shaped permanent magnets divided into N sets in the circumferential direction of the base frame according to the number N of magnetic poles, In each set, the magnetic poles are arranged in the same direction.
[0010]
The outer peripheral surfaces of the base frame and the end frame are respectively formed on polygonal flat surfaces to which a plurality of rod-shaped permanent magnets in the first and second multipolar permanent magnet assemblies are fixed, and the base frame and The inner peripheral surface of the end frame is cylindrical.
[0011]
The rod-shaped permanent magnets in the first and second multipolar permanent magnet assemblies have a substantially square cross-sectional shape, and the base frame and the end frame are flattened by adjoining the rod-shaped permanent magnets belonging to the same group. Stick to the surface.
[0014]
It is preferable that the end frame provided at both ends of the base frame is configured to be an extension of the base frame, and the base frame and the extension are integrally formed.
[0015]
The rod-shaped permanent magnets constituting the second multipolar permanent magnet assembly have a substantially square cross-sectional shape, and the outer peripheral surface of the end frame is a flat surface on which the rod-shaped permanent magnets are fixed. The second multipolar permanent magnet assembly is covered with a cylindrical frame having the same length as that of the second multipolar permanent magnet assembly.
[0016]
The frame body is preferably aligned with the central axis of the base frame by a flange member provided outside the base frame.
[0017]
The frame body may be divided into a plurality of short substantially cylindrical shapes.
[0018]
The outer diameter of the yoke body is preferably larger than the outer diameter of the frame body.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIG. 1 and FIG. 2, an embodiment will be described in the case where a multipolar permanent magnet device according to the present invention is applied to an ECR ion source device. This ion source device includes a pair of mirror electromagnets 11 and 12 arranged on the outside of a cylindrical plasma chamber 10 at an interval to create a mirror magnetic field, and a mirror electromagnet 11 outside the plasma chamber 10. 12 and a multipolar permanent magnet device 20 according to the present invention. Each of the mirror electromagnets 11 and 12 is realized by a solenoid coil. Each of the mirror electromagnets 11 and 12 may be composed of a plurality of rod-shaped permanent magnets.
[0021]
A connection portion 21 a having a waveguide portion is provided on the side surface of the plasma chamber 10, and the waveguide 13 is connected to introduce microwaves into the plasma chamber 10 from the radial direction. An RF window 22a is sandwiched between portions where the waveguide and the plasma chamber are connected. The RF window 22a transmits microwaves from the atmosphere into the plasma chamber 10, but maintains the vacuum in the plasma chamber 10. The position of the RF window 22a on the side surface of the plasma chamber 10 is less susceptible to plasma irradiation due to the magnetic field structure. Compared to the case where the RF window 22a is introduced from the plasma chamber axial direction as in an ECR ion source for a conventional ion implanter, There is an advantage that it is hard to get dirty. Since the RF window 22a becomes conductive when it becomes dirty, the microwave is cut off and the operation cannot be continued.
[0022]
In such an ECR ion source device, a high magnetic field is formed in the plasma chamber 10 by the mirror electromagnets 11 and 12 and the multipolar permanent magnet device 20, and an appropriate amount of ion generating gas is added to the magnetic field and 2.45. By introducing a microwave of (GHz), electrons are heated by ECR heating, plasma is generated, and an ion beam can be generated in the axial direction of the plasma chamber 10. When there is an 875 Gauss magnetic field for 2.45 (GHz) microwaves, electron ECR heating occurs.
[0023]
An ion extraction casing 40-1 is provided at the end of the mirror electromagnet 12, and an extraction electrode 40-2 and an anode electrode 40-3 are provided in the casing 40-1.
[0024]
Another function of the magnetic field described above is to effectively confine the plasma, resulting in increased ionization efficiency and reduced contamination of the RF window 22a. Plasma that tends to spread in the direction of the mirror electromagnet 11 and the multipolar permanent magnet device 20 is lost, and is not drawn out as a beam. Specifically, the maximum value of the magnetic field generated by the mirror electromagnet 11 and the multipolar permanent magnet device 20 needs to be at least 875 gauss or more in the plasma chamber 10, and is ideal if it is 2 kilogauss or more. . 2 kilogauss is about twice as large as that of an ECR ion source device for a conventional ion implantation apparatus. When RF is introduced from the axial direction, the plasma chamber diameter becomes large due to the propagation of microwaves. Therefore, it was practically difficult to generate a strong magnetic field of 2 kilogauss. On the other hand, the magnetic field of the mirror electromagnet 12 is weaker than that of the mirror electromagnet 11 and the multipolar permanent magnet device 20, and a plasma escape path is created in that direction. Thereby, ions in the plasma are taken out of the plasma chamber 10 from the direction of the mirror electromagnet 12. The multipolar permanent magnet device 20 according to the present invention will be described with reference to FIGS. The multipole permanent magnet device 20 includes quadrupole permanent magnets 23a to 23d (first multipole permanent magnet assembly) and a cylindrical yoke 24 provided on the outside thereof. In particular, in this example, each of the quadrupole permanent magnets 23a to 23d is configured by combining two rod-shaped magnets having a trapezoidal cross-sectional shape with the wide bottom surface facing outward, and further the quadrupole permanent magnet. 23a to 23d are combined with the base frame 26 in a ring shape. The base frame 26 is made of a nonmagnetic material such as aluminum. The magnetic poles of the four-pole permanent magnets 23a to 23d are arranged such that the magnetic poles facing each other with respect to the central axis direction of the plasma chamber 10 are the same, and the adjacent magnetic poles are opposite to each other in the circumferential direction. .
[0025]
The multipolar permanent magnet device 20 is formed by combining a plurality of rod-shaped magnets extending in the direction of the central axis of the plasma chamber 10 from both ends of the base frame 26 in addition to the above-described four-pole permanent magnets 23a to 23d. It has a set of multipolar permanent magnets 25-1 to 25-2 (second multipolar permanent magnet assembly). Speaking of the multipolar permanent magnet 25-1, here, 16 magnetic poles 25-1a to 25-1h are configured by combining 16 rod-shaped magnets in pairs. Among the eight magnetic poles 25-1a to 25-1h, the magnetic poles 25-1a to 25-1d corresponding to the four-pole permanent magnets 23a to 23d have the same magnetic pole direction as that of the four-pole permanent magnets 23a to 23d. Arranged to be the same. In addition, the magnetic poles 25-1f to 25-1h arranged between the magnetic poles 25-1a to 25-1d are arranged so that the magnetic poles are in the circumferential direction and opposite to each other. Similarly, in the multipolar permanent magnet 25-2, eight magnetic poles are formed. Cylindrical frames 27-1 and 27-2 made of a nonmagnetic material are provided outside the multipolar permanent magnets 25-1 to 25-2, respectively.
[0026]
Two sets of multipolar permanent magnets 25-1 and 25-2 are interposed between the mirror electromagnets 11 and 12 and the plasma chamber 10, and if there is a yoke, the mirror electromagnets 11 and 12 cause the plasma chamber. Since the magnetic field generated in the motor 10 becomes small, the yoke 24 combined with the quadrupole permanent magnets 23a to 23d is not provided. In any case, as the permanent magnet used in the multipolar permanent magnet device 20, a magnet having a magnetization direction perpendicular to the magnetic pole surface and having the same residual magnetic flux density is used.
[0027]
The multipolar permanent magnet 25-1 is not indispensable and may be deleted. In this case, the end portion (end portion frame) of the base frame 26 that is extended to form the multipolar permanent magnet 25-1 may be omitted. Further, the portions corresponding to the both end portions may be configured separately from the base frame 26. Further, the inner side of the base frame 26 has a cylindrical shape, but the outer surface has a flat surface for easy adhesion of the quadrupole permanent magnets 23a to 23d and the multipolar permanent magnets 25-1 and 25-2. I have to. For this reason, the outer side of the base frame 26 has a polygonal shape.
[0028]
Note that four long holes 24 a to 24 d are provided on the side surface of the yoke 24 at intervals in the circumferential direction. This is because the waveguide connection described in FIG. 2 can be connected at four arbitrary locations. The base frame 26 is provided with the long holes 26a only at the portions corresponding to the long holes 24a. However, the base frame 26 has the same length as the long holes 26a at the portions corresponding to the long holes 24b to 24d according to the connection portions of the waveguide. For this reason, not only locations corresponding to the elongated holes 24a in the base frame 26 but also locations corresponding to the elongated holes 24b to 24d are removed from the installation area of the quadrupole permanent magnets 23a to 23d as spaces. ing. And the location where the long hole is provided in the base frame 26 is the location corresponding to the polygonal corner, but when the long hole is provided, the corner is ground.
[0029]
Of course, long holes may be provided in advance in locations corresponding to the four long holes 24 a to 24 d of the yoke 24 in the base frame 26. In this case, the plasma chamber 10 is also provided with a long hole at a position corresponding to the long hole of the base frame 26, but a long hole to which the waveguide 13 is not connected in order to maintain the degree of vacuum in the plasma chamber 10. Needs to be closed with something like a lid.
[0030]
Returning to FIG. 1, a gas introduction pipe 29 for ion generation is connected to the left end of the plasma chamber 10. The right end of the plasma chamber 10 is opened to serve as an ion beam outlet, and a guide tube (not shown) for guiding the ion beam to the irradiation unit is connected to the opening of the plasma chamber 10.
[0031]
In such an ECR ion source device, a pair of mirror electromagnets 11 and 12 and a multipolar permanent magnet device 20 form a high magnetic field having a minimum B structure in the plasma chamber 10, and a gas for generating ions is generated in this magnetic field. In addition, by introducing a microwave of 2.45 (GHz), an ion beam can be generated in the axial direction of the plasma chamber 10.
[0032]
Such a multipolar permanent magnet device 20 is manufactured as follows. First, a cylindrical base frame 26 made of a non-magnetic material is prepared, and quadrupole permanent magnets 23a to 23d are bonded to the outside of the base frame 26, and multipolar permanent magnets 25-1 and 25-2 are attached to both ends thereof. 25-2 is glued. Next, the yoke 24 is combined with these outsides, and the frame bodies 27-1 and 27-2 are provided outside the multipolar permanent magnets 25-1 and 25-2 on both ends of the yoke 24.
[0033]
Here, positions close to both ends of the base frame 26, that is, boundary portions between the installation areas of the quadrupole permanent magnets 23 a to 23 d and the installation areas of the multipolar permanent magnets 25-1 and 25-2 are respectively in the radial direction. Extending flange portions 26-1 and 26-2 are formed. In particular, the protruding length of the flange portion 26-1 is slightly larger than that of the flange portion 26-2, and a notch 24-1 is provided in the circumferential direction on the inner periphery of the end of the yoke 24 corresponding to the flange portion 26-1. ing. Thereby, the front-end | tip of the flange part 26-1 has the function of positioning when the yoke 24 is assembled | attached. Further, steps 26-1a and 26-2a for positioning the frames 27-1 and 27-2 are provided on the outer surfaces of the flange portions 26-1 and 26-2. Steps 26-1b and 26-2b on processing of the quadrupole permanent magnets 23a to 23d are provided on the inner surface of 26-2.
[0034]
As described above, the base frame 26 is provided with a long hole 26a for installing the connecting portion 21a. The inner side of the base frame 26 has a cylindrical shape, but the outer surface is flattened so that the quadrupole permanent magnets 23a to 23d and the multipolar permanent magnets 25-1 and 25-2 are easily adhered. ing.
[0035]
The mirror electromagnets 11 and 12 are supported by a support member (not shown), and the multipolar permanent magnet device 20 is incorporated in a circular space at the center of the mirror electromagnets 11 and 12. Next, the cylindrical plasma chamber 10 that is sufficiently longer than this is incorporated inside the base frame 26.
[0036]
The conditions necessary for the above assembly are listed below.
[0037]
The base frame 26 is a one-piece unit by cutting.
[0038]
The outer peripheral surface of the base frame 26 has a polygonal cross-sectional shape and is flattened.
[0039]
When the arrangement of the quadrupole permanent magnets 23a to 23d and the multipolar permanent magnets 25-1 and 25-2 changes, the dimensions of the polygon may be changed.
[0040]
In order to position the yoke 25, the flanges 26-1 and 26-2 are formed on the outer periphery of the base frame 26. The method for producing the flanges 26-1 and 26-2 is as follows.
[0041]
In the first method, the flange is formed at the same time as the base frame 26 is cut out.
[0042]
In the second method, a ring-shaped object serving as a flange is fitted into the base frame 26 later.
[0043]
The third method is configured by attaching three or more spacers having steps 26-1a and 26-1b later.
[0044]
The yoke 24 is finished in a cylindrical shape.
[0045]
Although the inner surface of the yoke 24 is substantially cylindrical, the axial positioning of the yoke 24 with respect to the base frame 26 can be simplified by making a notch 24-1 in a part thereof.
[0046]
Each surface of the permanent magnet is flattened.
[0047]
The central axis of the yoke 24 is fitted with the flange of the base frame 26 so as to coincide with the axis of the base frame 26.
[0048]
The base frame 26 determines the axis of the yoke 24 through the flange, and the permanent magnet blocks 23 a to 23 d and 25-1 a to 25-1 h are not used for the alignment of the yoke 24.
[0049]
According to the multipolar permanent magnet device as described above, a high magnetic field having a minimum B structure is formed in the plasma chamber 10 by a combination with a pair of appropriate mirror electromagnets 11 and 12. As is well known, the magnetic field of the minimum B structure is a confined magnetic field structure in which ECR (Electron Cyclotron Resonance) resonance occurs in the plasma chamber 10 and the region where the ECR resonance occurs is closed in the plasma chamber 10. It is. In other words, the inner wall surface of the plasma chamber 10 and the ECR zone do not intersect, and the magnetic field of this minimum B structure is the ECR magnetic field B in space. _ECR (In the case of 2.45 MHz, it is 875 Gauss) Starting from one point weaker than B, before hitting the inner wall of the plasma chamber 10 in any direction _ECR Is a magnetic field that must be crossed. The ECR zone here is one in which ECR resonance points are continuously formed into a surface.
[0050]
In such a confinement magnetic field, as compared with the conventional microwave ion source device, the plasma electrons generated in the plasma chamber 10 are suppressed from being dissipated in the radial direction of the plasma chamber 10, thereby confining the electrons. By extending the time and promoting the heating of the electrons by the ECR heating action, particularly when the degree of vacuum in the plasma chamber 10 is high, it becomes easy to generate multivalent ions when colliding with gas atoms. Then, all ions including such multivalent ions are efficiently suppressed from leaking in the radial direction of the plasma chamber 10, and adhesion to the inner wall of the plasma chamber 10 and the RF window is suppressed. This means that it is possible to suppress the microwave transmission efficiency from being lowered due to the adhesion of ions to the RF window 22a.
[0051]
Thus, when the ion confinement efficiency is improved, the amount of gas introduced into the plasma chamber 10 can be reduced, and the degree of contamination in the plasma chamber 10 can be reduced. Even if the introduced gas is a corrosive gas, it is possible to suppress the ions from adhering to the inner wall of the plasma chamber 10 and corroding the inner wall. This means that the lifetime of the ion source device is prolonged.
[0052]
In addition, by setting the multipolar permanent magnets in the region where the microwave is introduced to the quadrupole permanent magnets 23a to 23d, the interaction with the magnetic field by the pair of mirror electromagnets 11 and 12 causes the central axis of the plasma chamber 10 to move. An ion beam having an elongated cross-sectional shape intersecting at right angles can be generated. It is known that the cross-sectional shape of this ion beam changes according to the number of poles of the multipolar permanent magnet in the region where the microwave is introduced. Incidentally, in the case of 6 poles, the cross-sectional shape is substantially triangular, and in the case of 8 poles, it is substantially square. In addition, it is preferable that the magnetic field strength comprised in the plasma chamber 10 is a magnetic field of 2 kilogauss or more.
[0053]
Next, the operation of the pair of mirror electromagnets 11 and 12 and the yoke 24 will be described with reference to FIG. It is known that when the frequency of the microwave introduced into the plasma chamber 10 is 2.45 (MHz), ECR resonance occurs at a magnetic field strength of 875 (Gauss). The absolute value | B | of the magnetic field generated by the mirror electromagnets 11 and 12 is as shown in FIG. 5B when the central axis r = 0 of the plasma chamber 10. In order to cause ECR resonance, it is necessary to form a convex valley between the mirror electromagnets 11 and 12 such that the curves intersect at 875 (Gauss) as shown in FIG. 5B. .
[0054]
Here, if the distance between them is too small compared to the inner diameters of the mirror electromagnets 11 and 12, the absolute value | B | of the magnetic field cannot form a convex valley below that intersects at 875 (Gauss). The ECR resonance point disappears. For this purpose, a cylindrical iron yoke 24 is interposed between the mirror electromagnets 11 and 12 to absorb the magnetic lines near r = 0 and lower the valley downward.
[0055]
Since the multipolar permanent magnet combined with the mirror electromagnets 11 and 12 cannot create a magnetic field in the plasma chamber 10 unless it is inside the yoke 24, the pole-shaped magnets are used to form the quadrupole permanent magnets 23a to 23d. The thin space between the yoke 24 and the plasma chamber 10 can be used for accommodation.
[0056]
Next, the principle of ion confinement action by a magnetic field of a quadrupole permanent magnet will be described with reference to FIG. In FIG. 6, the magnetic field lines between the quadrupole permanent magnets are symbolically shown one by one. Also, the broken line indicates the isomagnetic field strength range of the absolute value | B | of the magnetic field. The closer to the center, the closer the magnetic field strength is to an isotropic shape, but the more the magnetic field becomes isotropic, the closer it is to the magnetic pole. It ’s not right. The charged particles existing in such a magnetic field try to move to the magnetic pole side while moving in a spiral around the magnetic field lines. In other words, the charged particles tend to move toward the direction where the center of rotation becomes stronger. Such charged particles are also subject to a rebound action that moves in the opposite direction as the magnetic field strength increases as it approaches the magnetic pole. The degree of the rebound is determined by the initial motion direction, and the rebound is more easily as the strength ratio of the magnetic field (the ratio between the minimum value of the valley of the curve and the peak value in terms of FIG. 5B) increases. By such a principle, an ion confinement action in which the residence time of ions becomes long occurs. On the other hand, the RF window 22a is in a position that is parallel to the magnetic field lines, and ions are difficult to move in a direction perpendicular to the magnetic field lines, which is also one of the causes that the attachment of ions to the RF window 22a is difficult to occur.
[0057]
By the way, the reason why the frequency of the microwave is set to 2.45 (GHz) is that this frequency generator is used in household electric appliances such as a microwave oven and is provided at the lowest price. If it is not necessary to consider this, another frequency may be used.
[0058]
The present invention has been described with respect to the case of a four-pole permanent magnet, but it goes without saying that the number of magnetic poles is not limited to four. Further, the case where the present invention is applied to an ECR ion source device has been described. However, the multipolar permanent magnet device for ECR according to the present invention is not limited to the above-described embodiment, and requires a high magnetic field, particularly using ECR resonance. Needless to say, the present invention can be applied to all permanent magnet devices.
[0059]
【The invention's effect】
According to the multipolar permanent magnet device according to the present invention described above, the following effects can be obtained.
[0060]
Even if the permanent magnet block does not have an arch structure like a stone bridge, it does not come off inside.
[0061]
Since the permanent magnet blocks are not necessarily brought into close contact with each other, fine precision is not required for the angle of the surface.
[0062]
Since the outer periphery of the base frame is flat and the inner surface of the yoke is curved, the permanent magnet blocks that are not easily displaced in the circumferential direction are not necessarily brought into close contact with each other, so that the permanent magnet blocks can be arranged apart in the circumferential direction.
[0063]
If long holes are formed in the base frame and the yoke at the gaps between the permanent magnet blocks, microwave introduction openings can be provided in the radial direction.
[0064]
RF can be introduced from the radial direction of the plasma chamber through the opening, and even if the permanent magnet block is peeled off, it is difficult to shift laterally.
[0065]
Even if the yoke becomes a cover and the permanent magnet is peeled off, it does not jump out.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing the structure of an ECR ion source device to which the present invention is applied.
FIG. 2 is a cross-sectional view taken along line AA ′ of FIG.
FIG. 3 is a view showing a preferred embodiment of the multipolar permanent magnet device according to the present invention, in which FIG. (A) is a partially sectional side view, and (b) is taken along line BB ′ in FIG. Sectional drawing and figure (c) are sectional drawings by line CC 'of figure (a).
4 is a side view and a cross-sectional view of the yoke, the base frame and the frame shown in FIG. 3. FIG.
FIGS. 5A and 5B are diagrams for explaining the operation of the mirror electromagnet and the yoke shown in FIG. 1, in which FIG. 5A is a longitudinal sectional view, and FIG. 5B is a magnetic field with respect to a distance Z in FIG. FIG. 6 is a characteristic diagram showing an absolute value intensity | B |.
6 is a diagram for explaining the operation of the quadrupole permanent magnet shown in FIG. 2; FIG.
[Explanation of symbols]
10 Plasma chamber
11, 12 Mirror electromagnet
13 Waveguide
20 Multi-pole permanent magnet device
21a connection
22a RF window
23a-23d 4-pole permanent magnet
24 York
25-1, 25-2 Multipole permanent magnet
26 Base frame
27-1, 27-2 Frame
29 Gas introduction pipe

Claims (9)

A first multi-pole permanent magnet assembly comprising a plurality of rod-shaped permanent magnets is disposed on the outer peripheral surface of a cylindrical base frame disposed outside the plasma chamber so as to be disposed in the direction of the central axis of the base frame;
Covering the outside of the plurality of rod-shaped permanent magnets in the first multipole permanent magnet assembly is a yoke body that is a cylindrical outer frame body of approximately the same length as this,
End frames are provided at both ends of the base frame,
A second multipole permanent magnet assembly made up of a plurality of rod-shaped permanent magnets is disposed on both outer sides of the end frame,
A main magnetic closed circuit is formed in a cross section perpendicular to the central axis of the base frame by the rod-like permanent magnets constituting the first multipole permanent magnet assembly,
An end magnetic closed circuit having the same polarity as that of the first multipole permanent magnet assembly in a cross section orthogonal to the central axis of the end frame by the rod-like permanent magnets constituting the second multipole permanent magnet assembly Form the
A mirror magnet is disposed in proximity to each outer portion of the second multipole permanent magnet assembly, and the yoke body is interposed between the mirror magnets on both sides,
For connection with a waveguide for introducing microwaves, at least one connection portion is provided in the triple structure of the plasma chamber, the base frame, and the yoke body to connect the waveguide, Positioned between the rod-like permanent magnets in the first multipolar permanent magnet assembly, the plasma chamber, the base frame and the yoke body are each formed with a long hole parallel to the central axis direction thereof, and An RF window is disposed in the connection portion of the elongated hole portion of the plasma chamber so that microwaves are introduced from the radial direction of the plasma chamber,
The plurality of rod-like permanent magnets in the first multipolar permanent magnet assembly are divided into N magnet assemblies in the circumferential direction of the base frame according to the number of magnetic poles N (N is an even number), The rod-shaped permanent magnets belonging to the pair of magnets have the same orientation of the magnetic poles in the plane perpendicular to the central axis of the base frame, and the pairs adjacent to each other in the circumferential direction of the base frame are opposite to each other. To configure
The plurality of rod-shaped permanent magnets in the second multipolar permanent magnet assembly are:
The direction of the magnetic poles in the plane perpendicular to the central axis of the base frame is made the same so that the combination of the same magnetic poles as the N sets of magnet assemblies divided in the first multipole permanent magnet assembly is obtained. In addition, N sets of rod-shaped permanent magnets arranged so that adjacent magnetic poles at intervals with respect to the circumferential direction of the end frame are opposite to each other;
These N sets of rod-shaped permanent magnets are arranged between the N sets of rod-shaped permanent magnets so that the magnetic poles face the circumferential direction of the end frame and the adjacent magnetic poles are opposite to each other in the circumferential direction. A multipolar permanent magnet device for ECR that is characterized. The multipolar permanent magnet device for ECR according to claim 1 ,
A space is provided between adjacent sets of the plurality of rod-shaped permanent magnets in the first multipolar permanent magnet assembly in the circumferential direction of the base frame, and
A multipolar permanent magnet device for ECR, characterized in that a space portion is also formed in the base frame and the yoke body corresponding to the space portion. The multipolar permanent magnet device for ECR according to claim 2 ,
The first multi-pole permanent magnet assembly is composed of a plurality of magnet groups in each of the rod-shaped permanent magnets divided into N sets in the circumferential direction of the base frame according to the number N of magnetic poles, A multi-pole permanent magnet device for ECR characterized in that the magnetic poles are aligned in the same direction in each set. The multipolar permanent magnet device for ECR according to claim 1,
The outer peripheral surfaces of the base frame and the end frame are respectively formed on polygonal flat surfaces to which a plurality of rod-shaped permanent magnets in the first and second multipolar permanent magnet assemblies are fixed, and the base frame and The multipolar permanent magnet device for ECR, wherein an inner peripheral surface of the end frame is cylindrical. In the multipolar permanent magnet device for ECR according to claim 4 ,
The rod-shaped permanent magnets in the first and second multipolar permanent magnet assemblies have a substantially rectangular cross-sectional shape, and the base frame and the end frame are flattened by adjoining the rod-shaped permanent magnets belonging to the same group. A multipolar permanent magnet device for ECR, which is fixed to a surface. The multipolar permanent magnet device for ECR according to claim 1 ,
The end frame provided at both ends of the base frame is configured to be an extension of the base frame, and the base frame and the extension are integrally molded. . The multipolar permanent magnet device for ECR according to claim 1 ,
The rod-shaped permanent magnets constituting the second multipolar permanent magnet assembly have a substantially rectangular cross-sectional shape, and the outer peripheral surface of the end frame has a flat surface on which the rod-shaped permanent magnets are fixed. A multi-pole permanent magnet device for ECR, wherein the second multi-pole permanent magnet assembly is covered with a cylindrical frame having substantially the same length as that of the second multi-pole permanent magnet assembly. The multipolar permanent magnet device for ECR according to claim 7 ,
The multi-pole permanent magnet device for ECR, wherein the frame body is aligned with a central axis of the base frame by a flange member provided outside the base frame. The multipolar permanent magnet device for ECR according to claim 7 ,
The multipolar permanent magnet device for ECR, wherein an outer diameter of the yoke body is larger than an outer diameter of the frame body.

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