JP2007141545A - Deflecting electromagnet and ion beam irradiating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce electron loss due to E×B drift from a magnetic pole space for improving containment of an electron in the magnetic pole space so that the space charge of ion beam is neutralized efficiently by the confined electrons for reducing the divergence of the ion beam. <P>SOLUTION: This deflecting electromagnet 30a has first and second magnetic poles 32a and 32b mutually facing via an inter-pole space 34, through which an ion beam 4 passes. The deflecting electromagnet further has a pair of potential adjusting electrodes 52, which are placed to sandwich the path of the ion beam 4, in the same directions as the magnetic poles 32a and 32b in the inter-pole space 34, and a potential adjusting power source 54 which applies a positive voltage V<SB>1</SB>to the potential adjusting electrodes 52. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to, for example, a deflection electromagnet that bends an ion beam by a magnetic field and is used in an ion beam irradiation apparatus that performs ion implantation or the like by irradiating a target with an ion beam, and an ion beam irradiation apparatus including the same. . In the case of performing ion implantation, this ion beam irradiation apparatus is also called an ion implantation apparatus.

  An example of an ion beam irradiation apparatus is shown in FIG. This ion beam irradiation apparatus is configured to irradiate a target 16 with an ion beam 4 extracted from an ion source 2. The target 16 is, for example, a semiconductor substrate.

  More specifically, as described in Patent Document 1, this ion beam irradiation apparatus selects a specific ion species from the ion source 2 that extracts the ion beam 4 and the ion beam 4 that is extracted therefrom. A mass separation magnet 6 derived from the ion beam 4; an acceleration / deceleration tube 8 for accelerating or decelerating the ion beam 4 derived therefrom; and an energy separation magnet 10 for selectively extracting ions having a specific energy from the ion beam 4 derived therefrom. The ion beam 4 derived therefrom is scanned in the Y direction (for example, the horizontal direction) by a magnetic field, and the ion beam 4 derived therefrom is bent back and cooperates with the scanning magnet 12 to collimate the ion beam 4. A collimating magnet 14 that performs scanning, that is, creates a parallel ion beam 4 is provided.

  The ion beam 4 led out from the collimating magnet 14 is irradiated onto the target 16 held by the holder 18 in the processing chamber 20, whereby the target 16 is subjected to processing such as ion implantation. At that time, the target 16 is reciprocally driven in a Z direction (for example, a vertical direction) substantially orthogonal to the Y direction by a scanning mechanism (not shown) in this example. By cooperating with the reciprocating drive of the target 16 and the scanning of the ion beam 4, the entire surface of the target 16 can be subjected to processing such as ion implantation with high uniformity. All the paths of the ion beam 4 are kept in a vacuum atmosphere.

  In the ion beam irradiation apparatus as described above, it is necessary to increase the throughput of the apparatus and to reduce the ion implantation depth as the semiconductor device formed on the target 16 is miniaturized. It is desired to transport the ion beam 4 efficiently. However, as the ion beam 4 has a lower energy and a larger current, the divergence due to the space charge of the ion beam 4 increases, and it becomes difficult to efficiently transport the ion beam 4.

  There are many magnets such as the mass separation magnet 6, energy separation magnet 10, scanning magnet 12, and parallelizing magnet 14 in the transport path of the ion beam 4. Since these all deflect (bend) the ion beam 4, they can be collectively referred to as a deflection electromagnet. The distance passing through the space between the magnetic poles of the deflection electromagnet occupies most of the entire transport distance of the ion beam 4. For this reason, neutralizing the space charge of the ion beam in the space between the magnetic poles of the deflecting electromagnet to suppress the divergence increases the transport efficiency of the ion beam 4 in order to increase the transport efficiency of the ion beam 4 in particular. It is important to increase efficiency.

  For this purpose, for example, a method of supplying electrons from the outside of the magnetic pole to the space between the magnetic poles to neutralize the space charge of the ion beam passing through the space between the magnetic poles is conceivable. However, since the Larmor radius of the electrons becomes very small due to the strong magnetic field in the space between the magnetic poles, it is not easy to supply electrons from the outside to the space between the magnetic poles.

  As another method, there is a technique in which an electron source is installed on the surface of the magnetic pole and then electrons are supplied to the space between the magnetic poles to neutralize the space charge of the ion beam passing through the space between the magnetic poles (see, for example, Patent Document 2). ).

  In addition, the ion beam causes a part of its periphery to collide with a vacuum wall or the like to generate secondary electrons, or collide with a small amount of residual gas in the vacuum and ionize it to generate electrons. Originally, electrons exist in the ion beam and its vicinity. Therefore, as another method, there is a technique of neutralizing the space charge of the ion beam by improving confinement of electrons generated due to the ion beam by a cusp magnetic field formed in the ion beam line (for example, Patent Document 3). 4).

Japanese Patent Laying-Open No. 2001-143651 (paragraphs 0004-0005, FIG. 4) US Pat. No. 6,762,423 (FIG. 2) JP 2002-352765 A (paragraphs 0012-0019, FIG. 5) US Pat. No. 6,759,665 (FIG. 6)

  In the technique for installing the electron source, the structure is complicated and the space between the magnetic poles is usually very narrow, so it is very difficult to install the electron source. In addition, when the electron source is installed, the area through which the ion beam can pass is reduced, so that the ion beam easily collides with the electron source, thereby reducing the transport efficiency of the ion beam.

  Also, the electrons near the ion beam immediately flow out of the space between the magnetic poles due to the E × B (e-cross bee) drift caused by the electric field E created by the ion beam itself and the magnetic field B created by the deflecting electromagnet. As long as the E × B drift is not suppressed, even if an electron is supplied from the electron source to the space between the magnetic poles or the electron confinement in the ion beam line is improved by the cusp magnetic field, the space of the ion beam is lost. The effect of neutralizing the charge cannot be expected so much.

  This is described in detail below. First, the E × B drift will be described.

  When there is a magnetic field B, the electrons 38 perform a cyclotron motion so as to be wound around the magnetic field B as shown in FIG. Reference numeral 48 denotes the turning center.

  Further, when an electric field E is applied in a direction orthogonal to the magnetic field B, as shown in FIG. 3, a phenomenon occurs in which the orbit 40 at the center of rotation of the electrons 38 is shifted in the direction of the outer product of E × B. This is E × B drift. This E × B drift is due to the cyclotron motion being shifted due to the change in the kinetic energy of the electron 38 depending on the position of the electron 38 in the electric field E, thereby changing the Larmor radius.

  Further, as shown in FIG. 4, when the magnetic field B is directed in the vertical direction, the electrons 38 have a velocity component parallel to the magnetic field lines, and therefore move up and down along the magnetic field lines. Further, when an electric field E (see FIGS. 5 and 6) created by the ion beam 4 exists, it becomes a restoring force, and the electrons 38 reciprocate up and down along the lines of magnetic force. Therefore, when the magnetic field B and the electric field E exist, E × B drift occurs in the horizontal direction, and the electrons 38 move up and down along the lines of magnetic force. A complicated trajectory 40 that drifts in the direction of E × B is taken. Reference numeral 50 denotes a central trajectory of the trajectory 40.

  The ion beam 4 has a positive potential (beam potential). As shown in FIG. 5, when the ion beam 4 is considered as a cylinder having a uniform beam current density, the electric field E generated by the ion beam 4 is the ion beam 4. It occurs radially in the radial direction.

As shown in FIG. 6, the potential V _B of the ion beam 4 has a maximum value at the center of the ion beam 4, and the maximum value of the absolute value of the electric field E is generated near both ends a and b of the ion beam 4. This is because the gradient of the potential V _B , that is, | E | = | dV _B / dY | The direction of the electric field E is reversed up and down with respect to the Y axis.

  When the magnetic field B is applied to the electric field E, as shown in FIG. 7, the E × B drift becomes zero at the center of the ion beam 4 where the electric field E becomes zero, and the electric field E near both ends a and b of the ion beam 4. E × B drift is maximized because of the maximum. When the distance from the center of the ion beam 4 is far from both ends a and b, the electric field E becomes almost zero, so E × B becomes almost zero and E × B drift hardly occurs. The direction of E × B drift is reversed up and down with respect to the Y axis.

  FIG. 8 is a side view showing an outline of E × B drift of electrons in a conventional bending electromagnet. FIG. 9 is a sectional view taken along line DD in FIG.

  The deflection electromagnet 30 has a first magnetic pole 32a and a second magnetic pole 32b that are opposed to each other with a space 34 between the magnetic poles through which the ion beam 4 passes, and the magnetic pole space 34 is formed by both the magnetic poles 32a and 32b. The ion beam 4 passing through the inter-pole space 34 is bent by the generated magnetic field B (in this example, bent in the front and back direction of the paper surface). An example of the magnetic force lines 36 that form the magnetic field B is shown. The ion beam 4 passes in the direction indicated by the arrow 42, for example, but may be in the opposite direction.

  The E × B drift of the electrons 38 in the inter-magnetic pole space 34 is as described above with reference to FIGS. 2 to 7, and the direction of the E × B drift is the right side of the ion beam 4 in FIG. 9. Is directed from the front side to the back side of the paper surface, and on the left side, conversely, from the back side of the paper surface to the front direction. As a result, the electrons 38 flow out of the inter-magnetic pole space 34 along the ion beam 4 and are lost. This is shown in FIG. The drift direction of the electrons 38 is reversed on the left and right of the ion beam 4, and the loss directions 44 and 46 are reversed. In any case, the electrons 38 flow out of the space 34 between the magnetic poles due to the E × B drift. Loss. In FIG. 10, the magnetic pole 32 a on the upper side is indicated by an imaginary line in order to facilitate the illustration of the drift state of the electrons 38.

  The electrons 38 are, for example, secondary electrons generated when a part of the periphery of the ion beam 4 collides with a wall surface or the like that forms the space 34 between the magnetic poles, and residual gas in the space 34 between the magnetic poles collides with the ion beam 4. It is an electron that is generated by ionization.

  Japanese Patent No. 3399117 discloses that a magnetic field in the direction along the axis of the ion beam is generated outside the deflection electromagnet (more specifically, the mass analysis electromagnet) to confine electrons (confinement in the ion beam radial direction). A magnetic field generating means for performing magnetically and first and second cylindrical electron confining electrodes which are disposed near both ends and electrostatically confine electrons (confinement in the ion beam axial direction). Although a technique for suppressing the space charge of the ion beam by the confined electrons has been described, this technique cannot be applied in a deflection electromagnet.

  This is because a strong magnetic field is applied in the deflection electromagnet almost perpendicularly to the traveling direction of the ion beam, so that a magnetic field in the direction along the axis of the ion beam cannot be generated as described above. As described above, it is important to neutralize the space charge of the ion beam in the deflecting electromagnet. Further, since the cylindrical electron confinement electrode can only act to push back electrons by a negative voltage, it is also impossible to suppress the outflow of electrons from the space portion to the space between the magnetic poles due to E × B drift.

  Therefore, the present invention reduces the loss of electrons due to E × B drift from the space between the magnetic poles, improves the confinement of electrons in the space between the magnetic poles, and efficiently neutralizes the space charge of the ion beam by the confined electrons. The main purpose is to suppress the divergence of the ion beam.

  One of the deflecting electromagnets according to the present invention has first and second magnetic poles facing each other with a space between magnetic poles through which an ion beam passes, and deflecting the ion beam passing through the space between the magnetic poles. A pair of potential adjusting electrodes disposed in the space between the magnetic poles so as to sandwich the path of the ion beam from the same direction as the first and second magnetic poles; And a direct-current potential adjusting power source for applying a voltage.

  In this deflecting electromagnet, the potential around the ion beam can be adjusted by a potential adjusting electrode to which a positive voltage is applied from a potential adjusting power source, whereby electrons generated by the electric field around the ion beam and the magnetic field created by the magnetic poles. As the E × B drift trajectory, a closed one in the space including the space between the magnetic poles can exist. As a result, electrons in a state where the trajectory is captured can exist in or near the ion beam. Thereby, electron loss due to E × B drift from the space between the magnetic poles can be reduced, and the confinement of electrons in the space between the magnetic poles can be improved.

  The electrons are generated by, for example, secondary electrons generated when a part of the periphery of the ion beam collides with a wall surface forming the space between the magnetic poles, or residual gas in the space between the magnetic poles is ionized by the collision of the ion beam. Is an electron. The same applies to other deflection electromagnets described below.

  The voltage applied to the potential adjustment electrode from the potential adjustment power source is higher than the higher one of the potential created by the ion beam at the ion beam entrance end of the potential adjustment electrode and the potential created by the ion beam at the ion beam exit end. It is preferable to use a voltage.

  Another deflection electromagnet according to the present invention has first and second magnetic poles facing each other with a space between magnetic poles through which an ion beam passes, and bends the ion beam passing through the space between the magnetic poles. A deflecting electromagnet, which is disposed at a position closer to the entrance than the center of the space between the magnetic poles in the ion beam passing direction so as to sandwich the ion beam path from the same direction as the first and second magnetic poles. A pair of correction electrodes, a second pair of correction electrodes arranged side by side with the first pair of correction electrodes so as to be located outside the first pair of correction electrodes in the ion beam passage direction, A third pair of correction electrodes disposed so as to sandwich the ion beam path from the same direction as the first and second magnetic poles at a position closer to the exit than the center in the ion beam passage direction in the space between the magnetic poles; The third A fourth pair of correction electrodes arranged side by side with the third pair of correction electrodes so as to be located outside of the correction electrode in the ion beam passage direction, and the potentials of the second pair of correction electrodes A first DC correction power source that is kept lower than the potential of one pair of correction electrodes, and a second DC power source that keeps the potential of the fourth pair of correction electrodes lower than the potential of the third pair of correction electrodes. And a correction power supply.

  In this deflection electromagnet, the electron E × B is generated by the electric field generated by the first pair of correction electrodes and the second pair of correction electrodes, the electric field generated by the ion beam, and the magnetic field generated by the magnetic poles. The drift is in a direction crossing the ion beam. The E × B drift of electrons due to the electric field generated by the third pair of correction electrodes and the fourth pair of correction electrodes and the electric field generated by the ion beam and the magnetic field generated by the magnetic poles are also The direction is opposite to that of the second pair of correction electrodes, and the direction intersects the ion beam.

  On the other hand, the direction of the E × B drift of electrons due to the electric field created by the ion beam and the magnetic field created by the magnetic pole is in the direction along the ion beam.

  Therefore, in the space between the magnetic poles, electrons cross in the direction intersecting with the ion beam, and in a direction in which two types of drifts opposite to each other near the entrance and exit are combined with drift in the direction along the ion beam. As a result, there is a closed electron orbit in or near the ion beam. That is, electrons whose orbits are captured can exist in or near the ion beam. Therefore, the loss of electrons due to the E × B drift from the space between the magnetic poles can be reduced, and the confinement of electrons in the space between the magnetic poles can be improved.

  The first correction power source and the second correction power source may be the same power source.

  The first and second pairs of correction electrodes are disposed in the vicinity of the entrance end in the ion beam passage direction in the inter-magnetic pole space, and the third and fourth pairs of correction electrodes are disposed in the ion beam in the inter-magnetic pole space. It may be arranged near the exit end in the passing direction.

  The first pair of correction electrodes is disposed in the vicinity of the entrance end in the ion beam passage direction of the space between the magnetic poles, and the second pair of correction electrodes is disposed from the entrance end in the ion beam passage direction of the space between the magnetic poles. Are arranged on the outer side, the third pair of correction electrodes are arranged in the vicinity of the exit end in the ion beam passage direction of the space between the magnetic poles, and the fourth pair of correction electrodes are disposed in the ion beam in the space between the magnetic poles. You may arrange | position outside the exit end in a passage direction.

  Surfaces of the first and second magnetic poles or in the vicinity thereof are disposed between the first pair of correction electrodes and the second pair of correction electrodes so as to cross the path of the ion beam. A first pair of permanent magnets for creating a magnetic field in a direction that intensifies the magnetic field produced by the first and second magnetic poles, and at or near the surfaces of the first and second magnetic poles, A first magnetic field is formed between the pair of correction electrodes and the fourth pair of correction electrodes so as to intersect with the path of the ion beam so as to strengthen the magnetic field generated by the first and second magnetic poles. Two pairs of permanent magnets may be further provided.

  An ion beam irradiation apparatus according to the present invention is an apparatus configured to irradiate a target with an ion beam extracted from an ion source, and includes one or more deflection electromagnets in a path of the ion beam from the ion source to the target. It is characterized by being.

  According to the first aspect of the invention, the following effects can be obtained.

  (1) Since the potential adjusting electrode and the potential adjusting power source therefor are provided, electrons in a state where the trajectory is captured can be present in or near the ion beam. Thereby, electron loss due to E × B drift from the space between the magnetic poles can be reduced, and the confinement of electrons in the space between the magnetic poles can be improved. As a result, it is possible to efficiently neutralize the space charge of the ion beam by the confined electrons, thereby suppressing the divergence of the ion beam, and thus improving the transport efficiency of the ion beam.

  (2) Since the electrons can be confined in the vicinity of the ion beam trajectory, the electrons generated from the vicinity of the ion beam can be efficiently confined when the ion beam collides with the residual gas. The effect of neutralizing the space charge becomes greater.

  (3) Since it is not necessary to form a complicated magnetic field such as a cusp magnetic field, the structure of the deflection electromagnet can be simplified. In addition, there is no fear of disturbing the ion beam trajectory with an extra magnetic field.

  (4) Since the electrons generated due to the ion beam are confined to neutralize the space charge of the ion beam, it is not necessary to install an electron source for supplying electrons to the magnetic pole surface or the space between the magnetic poles from the outside. In addition, when the ion beam current is large, more electrons are generated due to the ion beam, and space charge neutralization is adjusted naturally, so that no extensive control is required.

  (5) Even when the ion beam is scanned, the electrons are light and are moved by being dragged by the electric field of the ion beam, and the electron drift speed is fast, so the deflecting electromagnet scans the ion beam like a scanning magnet. Even in this case, the above-described effect can be achieved.

  According to the second aspect of the present invention, it is possible to more surely close the electron orbit of the E × B drift in the space including the space between the magnetic poles. Can be increased. As a result, the space charge of the ion beam can be neutralized more efficiently, the divergence of the ion beam can be further suppressed, and the transport efficiency of the ion beam can be further improved.

  According to the third aspect of the present invention, since the correction electrode and the correction power supply for the correction electrode are provided, electrons in a state where the trajectory is captured can exist in or near the ion beam. Thereby, electron loss due to E × B drift from the space between the magnetic poles can be reduced, and the confinement of electrons in the space between the magnetic poles can be improved. As a result, it is possible to efficiently neutralize the space charge of the ion beam by the confined electrons, thereby suppressing the divergence of the ion beam, and thus improving the transport efficiency of the ion beam.

  Furthermore, there exists an effect similar to the effect of said (2)-(5) of invention of Claim 1.

  According to invention of Claim 4, there exists the further effect that simplification of a power supply structure can be aimed at.

  According to the fifth aspect of the present invention, the distance between the first and second pairs of correction electrodes and the third and fourth pairs of correction electrodes is long, and the direction in the direction along the ion beam passage direction is taken. Since the reciprocal confinement length of electrons can be made long, a wide area for neutralizing the space charge of the ion beam can be taken. As a result, the space charge of the ion beam can be neutralized more efficiently, the divergence of the ion beam can be further suppressed, and the transport efficiency of the ion beam can be further improved.

  According to the sixth aspect of the present invention, by utilizing the curvature of the magnetic field lines in the vicinity of the end of the magnetic pole, the decrease in the E × B drift of the electrons in the vicinity of the correction electrode is suppressed, thereby reducing the weakly confined region of the electrons. Therefore, the electron confinement performance can be further enhanced. In addition, the distance between the first and second pairs of correction electrodes and the third and fourth pairs of correction electrodes is increased to increase the reciprocal confinement length of electrons in the direction along the ion beam passage direction. Therefore, a wide area for neutralizing the space charge of the ion beam can be taken. As a result, the space charge of the ion beam can be neutralized more efficiently, the divergence of the ion beam can be further suppressed, and the transport efficiency of the ion beam can be further improved.

  According to the seventh aspect of the present invention, the decrease in the E × B drift of the electrons in the vicinity of the correction electrode is suppressed by utilizing the curvature of the magnetic field lines created by the first and second pairs of permanent magnets. The weak confinement region can be reduced. Further, the electron confinement region can be expanded by the gradient B drift caused by the magnetic field gradient generated by the permanent magnet. Therefore, the electron confinement performance can be further enhanced. As a result, the space charge of the ion beam can be neutralized more efficiently, the divergence of the ion beam can be further suppressed, and the transport efficiency of the ion beam can be further improved.

  According to the eighth aspect of the present invention, since one or more deflection electromagnets as described above are provided and each of the deflection electromagnets exhibits the effect, the transport efficiency of the ion beam extracted from the ion source to the target is improved. Can be made.

  FIG. 11 is a schematic longitudinal sectional view showing a first embodiment of the bending electromagnet according to the present invention. Portions that are the same as or equivalent to those in the conventional example shown in FIGS. 8 to 10 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

  The deflection electromagnet 30a has a pair of potentials arranged so as to sandwich the path of the ion beam 4 from the same direction as both the magnetic poles 32a and 32b in the inter-magnetic pole space 34 between the first magnetic pole 32a and the second magnetic pole 32b. An adjustment electrode 52 is provided. More specifically, a pair of plate-like potential adjustment electrodes 52 are disposed in the vicinity of the surfaces 33a and 33b of the magnetic poles 32a and 32b, respectively, so as to be electrically insulated from the magnetic poles 32a and 32b.

  When coordinate axes X, Y, and Z orthogonal to each other in the inter-magnetic pole space 34 are taken as shown in FIG. 11 and the like, that is, the coordinate of the center of the inter-magnetic pole space is the origin, and the direction toward the passing direction 42 of the ion beam 4 is X Assuming that the axis, the direction perpendicular to the Y axis is the Y axis, and the direction perpendicular to the longitudinal direction (that is, the vertical direction between the magnetic poles 32a and 32b) is the Z axis, the pair of potential adjusting electrodes 52 It is arranged with a space between them.

  The lengths of the potential adjustment electrodes 52 in the X direction and the Y direction are preferably long enough to cover the inter-magnetic pole space 34 as much as possible. This is because the potential around the ion beam can be adjusted in a wider region of the space 34 between the magnetic poles. In this embodiment, the length is such that it covers almost the entire area of the inter-magnetic pole space 34.

The bending electromagnets 30a further includes a DC voltage regulated power supply 54 for applying respective positive the voltages V ₁ to the pair of potential adjusting electrode 52. The positive terminal of the potential adjusting power source 54 is connected to the pair of potential adjusting electrodes 52, and the negative terminal is grounded. The magnetic poles 32a and 32b are also electrically grounded.

If the voltage V ₁ applied to each potential adjusting electrode 52 from the potential adjusting power source 54 is 0 V (in this case, the potential adjusting electrode 52 has the same potential as the magnetic poles 32a and 32b, the potential distribution around the ion beam) Is the same as in the case of the conventional deflection electromagnet 30 shown in FIG. 9 and the like), the potential distribution around the ion beam in the inter-magnetic pole space 34 and the electrons 38 (if not shown, for example, FIG. 8 to FIG. 10, FIG. The outline of E × B drift of 22 to 27. The same applies hereinafter) is shown in FIGS. The magnetic field B is a magnetic field generated by the magnetic poles 32 a and 32 b, and the electric field E is an electric field generated by the ion beam 4. Reference numeral 56 denotes an equipotential line. As described above, the electrons 38 are, for example, secondary electrons generated when a part of the periphery of the ion beam 4 collides with a wall surface or the like forming the space 34 between the magnetic poles, or residual gas in the space 34 between the magnetic poles. Electrons generated by ionization due to the collision of the beam 4. The same applies to the electrons 38 described below.

  In FIG. 13 and FIG. 15, the upper magnetic pole 32a is not shown and the upper potential adjustment electrode 52 is indicated by an imaginary line in order to make the equipotential line 56 and the like easier to show. Further, in FIG. 11 and subsequent figures, the ion beam 4 is shown in a cylindrical shape for convenience, but is not limited thereto. The ion beam 4 is originally bent by the magnetic field generated by the magnetic poles 32a and 32b, but for the sake of simplicity of illustration, the bending due to the magnetic field is ignored and shown as a straight line.

As described above (see FIG. 6 and its description), the ion beam 4 has a positive potential. However, when the voltage V _{1 is set} to 0 V, the wall surface around the ion beam 4 (that is, the magnetic poles 32a, 32b and The potential of the potential adjusting electrode 52) becomes 0 V, and the potential distribution around the ion beam 4 becomes unsuitable for confining the electrons 38 under the influence. That is, as schematically shown in FIG. 12, the potential near the ion beam 4 is low in the center due to the influence of the potential of the surrounding wall surface, and near the entrance and exit of the inter-magnetic pole space 34. In order to get away from the wall surface, the potential returns and becomes high. In other words, it has a saddle shape. For example, when the potential of the ion beam 4 at the entrance of the space 34 between the magnetic poles is 100 V, the potential in the vicinity of the ion beam 4 is high (indicated by “high” in the figure. The same applies to other figures). Nearly 100V, in the middle place (indicated by “middle” in the figure. The same applies to other figures), about 50V, and in the low place (indicated by “low” in the figure. The same applies to other figures), 10V. It becomes the following.

  In this case, the direction of the E × B drift of the electrons 38 is + Y direction (that is, from the front to the back of the paper) on the ion beam entrance side of the inter-magnetic pole space 34, and on the ion beam exit side, as shown in FIG. -Y direction (ie, from the back of the paper to the front). Further, in FIG. 12 (and FIG. 14 and the like), the magnitude of E × B drift | E × B | is indicated by the area of a parallelogram with diagonal lines.

FIG. 12 is a longitudinal sectional view of the ion beam 4 viewed from the side, but the potential distribution around the ion beam 4 is the same as that of FIG. It is distributed and has a bowl shape. As described above, since the voltage V ₁ applied to the potential adjusting electrode 52 is 0V, the potential of the wall surface around the ion beam 4 is 0V. The main difference between FIG. 12 and FIG. This is because only the direction of the magnetic field B is present.

  When the distribution of the equipotential lines 56 around the ion beam, that is, the distribution of the potential has a saddle shape, as shown in FIG. It flows out of the space 34 between the magnetic poles in the direction along the ion beam 4 and is lost.

On the other hand, an outline of the potential distribution around the ion beam and the E × B drift of the electrons 38 in the inter-magnetic pole space 34 when the positive voltage V ₁ is applied from the potential adjusting power source 54 to each potential adjusting electrode 52 is shown in FIGS. As shown in FIG. This corresponds to FIGS. 12 and 13, respectively.

FIGS. 14 and 15 are examples in which the potential of the ion beam 4 at the entrance of the inter-magnetic pole space 34 is 100V and the voltage V ₁ is 100V. In this case, the potential around the ion beam in the space 34 between the magnetic poles is affected by the potential of the potential adjustment electrode 52 and has the highest convex distribution near the center of the ion beam 4. For example, it becomes about 150 V at a high place, and the potential gradually decreases from there toward the surroundings. In the vicinity of the potential adjustment electrode 52, the voltage is about 100V.

When the distribution of equipotential lines 56 around the ion beam, that is, the distribution of potential is convex as described above, the E × B drift of the electrons 38 circulates in the XY plane as shown in FIG. The drift trajectory 58 of the electrons 38 is included in the direction including the closed space in the space including the inter-pole space 34. That is, in this bending electromagnets 30a, by applying a positive voltages V ₁ to the potential adjustment electrodes 52, it is possible to adjust the potential of the surrounding ion beam, thereby creating an electric field E and the magnetic poles near the ion beam As a trajectory of the electron E × B drift caused by the magnetic field B, a trajectory closed in the space including the inter-pole space 34 can exist.

  As a result, the electrons 38 in a state where the trajectory is captured can exist in the ion beam 4 or in the vicinity thereof. Thereby, the loss of the electrons 38 due to the E × B drift from the inter-pole space 34 can be reduced, and the confinement of the electrons 38 in the inter-pole space 34 can be improved.

  Furthermore, the space charge of the ion beam 4 can be efficiently neutralized by the confined electrons 38, and the divergence of the ion beam 4 can be suppressed, and as a result, the transport efficiency of the ion beam 4 can be improved.

  In addition, since the electrons 38 can be confined within the vicinity of the ion beam trajectory, the electrons generated from the vicinity of the ion beam can be efficiently confined by the collision of the ion beam 4 with the residual gas. The effect of neutralizing the space charge of 4 is further increased.

  In addition, since it is not necessary to form a complicated magnetic field such as a cusp magnetic field, the structure of the bending electromagnet 30a can be simplified. In addition, there is no fear of disturbing the trajectory of the ion beam 4 with an extra magnetic field.

  Further, electrons generated due to the ion beam 4, that is, secondary electrons generated when a part of the periphery of the ion beam 4 collides with a wall surface or the like forming the space 34 between the magnetic poles, and residuals in the space 34 between the magnetic poles. In order to confine the electrons generated when the gas is ionized by the collision of the ion beam 4 and neutralize the space charge of the ion beam 4, it is necessary to install an electron source that supplies electrons from the surface of the magnetic pole or from the outside to the space 34 between the magnetic poles. Absent. In addition, if the ion beam current is large, more electrons are generated due to the ion beam 4, and space charge neutralization is adjusted naturally, so that no extensive control is required.

  Further, even when the ion beam 4 is scanned, the electrons are light and are dragged and moved by the electric field of the ion beam 4, and the drift speed of the electrons is fast, so that the deflecting electromagnet 30a moves the ion beam 4 like a scanning magnet. Even when scanning, the above-described effects can be obtained.

The voltage V ₁ applied to the potential adjusting electrode 52 from the potential adjusting power source 54 is the potential generated by the ion beam 4 at the ion beam inlet end 52a of the potential adjusting electrode 52 and the potential generated by the ion beam 4 at the ion beam outlet end 52b. It is preferable to set the voltage higher than the higher one.

  By doing so, the potential near the center of the ion beam 4 can be made higher than the potentials at the entrance end 52a and the exit end 52b, and the potential distribution around the ion beam can be more reliably made convex. Within the trajectory of the E × B drift, a closed space in the space including the inter-pole space 34 can be present more reliably, and the confinement performance of the electrons 38 can be further enhanced. As a result, the space charge of the ion beam 4 can be neutralized more efficiently, the divergence of the ion beam 4 can be further suppressed, and the transport efficiency of the ion beam 4 can be further improved.

  FIG. 16 is a schematic longitudinal sectional view showing the outlet half of the second embodiment of the bending electromagnet according to the present invention. FIG. 17 is a plan view showing an outline of the direction of E × B drift of electrons in the bending electromagnet shown in FIG. In FIG. 16, the inlet-side half is not shown, but has a symmetrical structure with respect to the symmetry center line 78 (see FIG. 17). The same applies to FIGS. 18 and 19. In FIG. 17, the magnetic pole 32 a on the upper side is indicated by an imaginary line in order to facilitate the illustration of the electron drift direction and the like. Further, the potential adjusting electrode 52 is omitted because it is not necessary for the description.

  The deflecting electromagnet 30b sandwiches the path of the ion beam 4 from the same direction as the first and second magnetic poles 32a and 32b at a position closer to the entrance than the center of the space 34 between the magnetic poles in the ion beam passing direction. The arranged first pair of correction electrodes 61 (see FIG. 17) and the first pair of correction electrodes 61 so as to be positioned outside the first pair of correction electrodes 61 in the ion beam passing direction. The second pair of correction electrodes 62 (see FIG. 17) and the first and second magnetic poles 32a and 32b, which are closer to the exit than the center of the inter-magnetic pole space 34 in the ion beam passage direction, are the same. A third pair of correction electrodes 63 arranged so as to sandwich the path of the ion beam 4 from the direction, and to be positioned outside the third pair of correction electrodes 63 in the ion beam passage direction. Tile correcting electrode 63 of the third pair and a correction electrode 64 of the fourth pair is located.

  Each of the first to fourth pairs of correction electrodes 61 to 64 has a plate shape and is arranged so as to sandwich the ion beam 4 with a space therebetween in the Z direction described above. Yes. More specifically, each pair of correction electrodes 61 to 64 is disposed in the vicinity of the surfaces 33a and 33b of the magnetic poles 32a and 32b and electrically insulated from the magnetic poles 32a and 32b.

  The length in the Y direction of each pair of correction electrodes 61 to 64 is preferably set to a length that covers the inter-magnetic pole space 34 as long as possible. This is because electrons can be confined in a wider area. In this embodiment, the length between the magnetic pole spaces 34 is approximately the same as the length in the Y direction. The length of each pair of correction electrodes 61 to 64 in the X direction only needs to be long enough to create a concentric semicircular electric field (see electric field lines 70) described later.

  The deflection electromagnet 30b further includes a first DC correction power source (not shown, corresponding to the second pair) that keeps the potential of the second pair of correction electrodes 62 lower than the potential of the first pair of correction electrodes 61. And a second DC correction power supply 66 that keeps the potential of the fourth pair of correction electrodes 64 lower than the potential of the third pair of correction electrodes 63.

In this example, the second correction power supply 66 includes a DC power supply 67 having a positive end connected to the third pair of correction electrodes 63 and a DC power supply having a negative end connected to the fourth pair of correction electrodes 64, respectively. And a power source 68. The negative electrode end of the DC power supply 67 and the positive electrode end of the DC power supply 68 are grounded. If the voltages output from the DC power supplies 67 and 68 are V ₂ and V ₃ , respectively, the potentials of the correction electrodes 63 and 64 are V ₂ and V ₃ , respectively. Although not shown, the first correction power source on the inlet side has the same configuration as this, for example.

If the first correction power source and the second correction power source are different from each other, the degree of freedom in correcting the electric field increases. Further, the same power source may be used, and in this way, the power source configuration can be simplified. If you same applies the (V ₂ in this example) the same voltage to the correction electrode 61 and 63, it applies the same voltage to the correction electrode 62 and 64 (V ₃ in this example).

Although the deflection electromagnet 30b includes the potential adjustment electrode 52 described above, the potential adjustment electrode 52 is not necessarily used in combination with the correction electrodes 61 to 64. The potential adjustment electrode 52 may not be provided. When the potential adjusting electrode 52 is provided and the positive voltage V ₁ as described above is applied thereto, both of the effects described above by the potential adjusting electrode 52 and the effects described below by the correction electrodes 61 to 64 can be achieved. .

In this deflection electromagnet 30b, the potential of the correction electrode 64 is lower than that of the correction electrode 63 (in other words, the potential of the correction electrode 63 is higher than that of the correction electrode 64). The electric force lines 70 having a concentric semicircular cross section toward 64 are formed. The electric field E _{1 formed by the} correction electrode 63 and the correction electrode 64 and the electric field generated by the ion beam 4 (here, referred to as E ₂ ), and the magnetic field B generated by the magnetic poles 32a and 32b. The E × B drift due to is in the direction intersecting the ion beam 4 as shown in FIG. More specifically, the direction is the + Y direction. The direction of this E × B drift is indicated by an arrow 82 in FIG. Also, the magnitude of this E × B drift | E × B | is indicated by the area of a parallelogram with hatching in FIG. Note that the electric field E ₁ and the electric field E ₂ are illustrated in more detail in FIG.

  Due to the electric field E formed by the electric field generated by the first pair of correction electrodes 61 and the second pair of correction electrodes 62 and the electric field generated by the ion beam 4 near the entrance, and the magnetic field B generated by the magnetic poles 32a and 32b. Since the direction of the electric field generated by the correction electrodes 61 and 62 is reversed and the direction of the combined electric field E is also reversed, the E × B drift is opposite to the third and fourth pairs of correction electrodes 63 and 64 side. The direction is the direction intersecting the ion beam 4. More specifically, it is in the −Y direction. The direction of this E × B drift is indicated by an arrow 81 in FIG.

  On the other hand, the direction of the E × B drift caused by the electric field generated by the ion beam 4 and the magnetic field generated by the magnetic poles 32a and 32b is the direction along the ion beam 4 as described above with reference to FIG. More specifically, on the left side in the ion beam 4 passing direction 42, the direction is −X as indicated by an arrow 83 in FIG. 17 and on the right side is the + X direction as indicated by an arrow 84.

  Therefore, in the inter-magnetic pole space 34, the electrons 38 are of two types in the Y direction intersecting the ion beam 4 and in opposite directions near the entrance and exit (directions indicated by arrows 81 and 82 in FIG. 17). The E × B drift and the E × B drift in the X direction along the ion beam 4 (directions indicated by arrows 83 and 84 in FIG. 17) will drift in the synthesized direction, thereby causing the arrows 81 to 84. Since the drifts in the directions indicated by are connected to each other, a closed electron orbit exists in or near the ion beam 4. An example of such a closed drift trajectory 86 of electrons is shown in FIG. Thereby, the electrons 38 in which the trajectory is captured can be present in or near the ion beam 4. Therefore, the loss of the electrons 38 due to the E × B drift from the interpole space 34 can be reduced, and the confinement of the electrons 38 in the interpole space 34 can be improved. As a result, the space charge of the ion beam 4 can be efficiently neutralized by the confined electrons 38, and the divergence of the ion beam 4 can be suppressed. As a result, the transport efficiency of the ion beam 4 can be improved.

  The first and second pairs of correction electrodes 61 and 62 are arranged near the entrance end in the ion beam passing direction of the inter-magnetic pole space 34, and the third and fourth pairs of correction electrodes 63 and 64 are arranged between the magnetic poles. It is preferable to arrange in the vicinity of the exit end of the space 34 in the ion beam passage direction (see correction electrodes 63 and 64 in FIG. 19). In such a case, the distance between the first and second pairs of correction electrodes 61 and 62 and the third and fourth pairs of correction electrodes 63 and 64 is increased, and the direction in the direction along the ion beam passage direction is taken. Since the round-trip confinement length of the electrons 38 can be increased, a wide area for neutralizing the space charge of the ion beam 4 can be provided. As a result, the space charge of the ion beam 4 can be neutralized more efficiently, the divergence of the ion beam 4 can be further suppressed, and the transport efficiency of the ion beam 4 can be further improved.

By the way, in the deflection electromagnet 30b, as shown in FIG. 16, in the vicinity of the upper and lower correction electrodes 63 and 64, the electric field E ₂ formed by the correction electrodes 63 and 64 is almost perpendicular to the correction electrodes 63 and 64. The electric field E obtained by combining the electric field E ₂ and the electric field E ₁ generated by the ion beam 4 becomes almost parallel to the magnetic field B, and the magnitude of E × B drift | E × B | Become. That is, weak confinement regions 71 and 72 are generated as shown by hatching in FIG.

  FIG. 18 shows an embodiment (third embodiment) that can improve the problem of the weakly confined region. The difference from the embodiment shown in FIG. 16 will be mainly described. In this deflection electromagnet 30c, the third pair of correction electrodes 63 is arranged in the vicinity of the exit end in the ion beam passage direction of the inter-magnetic pole space. The fourth pair of correction electrodes 64 is disposed outside the exit end in the ion beam passage direction of the inter-magnetic pole space 34. The same applies to the inlet side although not shown. That is, the first pair of correction electrodes 61 is arranged near the entrance end in the ion beam passage direction of the inter-magnetic pole space 34, and the second pair of correction electrodes 62 is arranged in the ion beam passage direction of the inter-magnetic pole space 34. It arrange | positions outside the entrance end in.

  In this way, a leakage magnetic field exists near the ends of the magnetic poles 32a and 32b, and the magnetic force lines 36 created by the magnetic poles 32a and 32b are curved outward from the inter-magnetic pole space 34. In FIG. 16, it is possible to prevent the synthetic electric field E and the magnetic field B from being parallel to each other, thereby preventing the weak confinement region 72 shown in FIG. Further, the weak confinement region 71 generated in the vicinity of the correction electrode 63 can be reduced. The same applies to the vicinity of the correction electrodes 61 and 62 on the entrance side.

  As described above, according to the deflection electromagnet 30c shown in FIG. 18, the E × B drift of the electrons 38 in the vicinity of the correction electrodes 61 to 64 is reduced by utilizing the curvature of the magnetic force lines 36 in the vicinity of the ends of the magnetic poles 32a and 32b. Since the weak confinement region of the electrons 38 can be reduced, the confinement performance of the electrons 38 can be further improved. In addition, the distance between the first and second pairs of correction electrodes 61 and 62 and the third and fourth pairs of correction electrodes 63 and 64 is increased so that the electrons 38 in the direction along the ion beam passage direction can be reduced. Since the reciprocating confinement length can be made long, a wide area for neutralizing the space charge of the ion beam 4 can be taken. As a result, the space charge of the ion beam 4 can be neutralized more efficiently, the divergence of the ion beam 4 can be further suppressed, and the transport efficiency of the ion beam 4 can be further improved.

  FIG. 19 shows another embodiment (fourth embodiment) that can solve the problem of the weakly confined region. Explaining mainly the differences from the embodiment shown in FIG. 16, the deflection electromagnet 30d is the surfaces 33a and 33b of the magnetic poles 32a and 32b, and the third pair of correction electrodes 63 and the fourth A pair (second pair) of permanent magnets 75 are arranged between the pair of correction electrodes 64 so as to cross the path of the ion beam 4 and create a magnetic field in a direction in which the magnetic field generated by the magnetic poles 32a and 32b is strengthened. It has. The polarities of the surfaces of the upper and lower permanent magnets 75 facing the ion beam 4 are the same as the polarities of the surfaces 33a and 33b of the magnetic poles 32a and 32b, respectively. Each permanent magnet 75 has a rod shape extending in a direction intersecting with the passing direction of the ion beam 4.

  The inlet side is also provided with a permanent magnet similar to the permanent magnet 75, although not shown. That is, the surfaces 33a and 33b of the magnetic poles 32a and 32b are disposed between the first pair of correction electrodes 61 and the second pair of correction electrodes 62 so as to intersect the path of the ion beam 4 respectively. And a pair of (first pair) permanent magnets for generating a magnetic field in a direction in which the magnetic field generated by the magnetic poles 32a and 32b is strengthened.

  In this deflection electromagnet 30d, the magnetic field created by the permanent magnet 75 is superimposed on the magnetic field created by the magnetic poles 32a and 32b, thereby forming a composite magnetic field B. Since the magnetic field generated by the permanent magnet 75 is curved, the resultant magnetic field B is also curved in the inner and outer directions (in other words, the + X direction and the −X direction) of the inter-magnetic pole space 34. Some of the magnetic force lines 76 representing the magnetic field B are shown in FIG. Since the magnetic field B is thus curved, the magnetic field B and the synthetic electric field E are prevented from being parallel to each other in the vicinity of the correction electrodes 63 and 64, and the weak confinement region 71 and 72 can be prevented or reduced. The same applies to the vicinity of the correction electrodes 61 and 62 on the entrance side.

  In addition, since the synthesized magnetic field B is stronger near the permanent magnet 75 than near the Y axis, the magnetic field B has a non-uniform magnitude, and the Larmor radius of the electrons 38 varies depending on the location. A phenomenon occurs in which electrons 38 drift and drift. This is called a gradient (drift) B drift. This naturally becomes stronger near the permanent magnet 75.

  In FIG. 20, the component perpendicular to the magnetic field line 76 of the gradient ∇B of the magnetic field B is indicated by ∇B⊥. In FIG. 20, only the lines of magnetic force 76 that are curved in the inner direction of the inter-magnetic pole space 34 (in other words, the −X direction) are illustrated, but the outer direction of the inter-magnetic pole space 34 (in other words, in other words, Some are curved in the + X direction. The magnetic field density gradient ∇B is divided into a component ∇B⊥ that is perpendicular to the magnetic field line 76 and a component ∇B‖ that is parallel to the magnetic field line 76. However, since ∇B‖ × B = 0, only the vertical component ∇B⊥ needs to be considered. . Therefore, ∇B⊥ × B drift caused thereby will be referred to as gradient B drift below. Since the magnetic lines of force 76 are curved inward and outward in the inter-magnetic pole space 34, the gradient B drift is in the + Y direction as shown in FIG. On the other hand, the half on the side curved in the outward direction is the -Y direction. This drift is naturally not affected by the electric field.

As shown in FIG. 21, the magnitude and direction of the gradient B drift (∇B⊥ × B drift) shown in FIG. 20 has a minimum value on the Y axis and is maximum near the upper and lower permanent magnets 75. In the Y-axis direction, that is, in the longitudinal direction of the rod-like permanent magnet 75, there is no change in the curved shape of the magnetic lines of force 76, so that the Y coordinate position (for example, + Y ₁ , 0, − There is no change in the drift due to Y ₁ ).

  In the vicinity of the permanent magnet on the entrance side of the space 34 between the magnetic poles, a gradient B drift occurs as described above, but the direction of the drift is opposite to that on the exit side because the direction of curvature of the magnetic field lines is opposite. That is, the gradient B drift is in the -Y direction in the half of the side where the magnetic lines of force are curved in the inner direction of the inter-magnetic pole space 34, and is in the + Y direction in the half of the side curved in the outer direction.

  When attention is paid to the drift directions in the vicinity of the correction electrode 61 and the correction electrode 63 of the gradient B drift due to the magnetic fields of the inlet-side permanent magnet and the outlet-side permanent magnet, this is indicated by the directions of arrows 81 and 82 shown in FIG. become. Therefore, this gradient B drift can reinforce the drift of electrons in the Y direction in the vicinity of the correction electrodes 61 and 63, thereby expanding the electron confinement region. That is, drifts in the directions indicated by arrows 81 to 84 in FIG. 17 are connected to each other in a wider region in the Z direction, so that there is a closed electron orbit in a wider region in the Z direction. Become.

  As described above, according to the deflection electromagnet 30d shown in FIG. 19, by providing the first pair of permanent magnets and the second pair of permanent magnets, a weakly confined region of electrons is formed in the vicinity of the correction electrodes 61 to 64. This can be prevented or reduced, and the drift in the Y direction can be enhanced by the gradient B drift, so that the electron confinement region can be expanded. Therefore, the confinement performance of the electrons 38 can be further improved. As a result, the space charge of the ion beam 4 can be neutralized more efficiently, the divergence of the ion beam 4 can be further suppressed, and the transport efficiency of the ion beam 4 can be further improved.

  The first and second pairs of permanent magnets may be disposed in the vicinity of the surfaces 33a and 33b instead of being disposed on the surfaces 33a and 33b of the magnetic poles 32a and 32b. Even in this case, the same effects as described above can be obtained.

  By the way, when the deflection electromagnet 30c of the third embodiment shown in FIG. 18 is examined in more detail, the magnetic field lines 36 due to the magnetic poles protrude outward at the ends of the magnetic poles 32a and 32b, and the magnetic field B there is weakened. A gradient B is generated in the direction in which the magnetic field B is strong (that is, inward of the space 34 between the magnetic poles), and a gradient B drift is generated in the direction of ∇B × B. In FIG. 18, | ∇B × B | indicates the size. Reference numeral 88 denotes a contour line of the magnitude | B | of the magnetic field B created by the magnetic poles 32a and 32b. Since the gradient B drift works in a direction to cancel the confinement action of the electrons 38 due to the E × B drift described above, the confinement performance of the electrons 38 is slightly deteriorated. Incidentally, when the correction electrodes 61 to 64 are inside the end of the inter-magnetic pole space 34 (that is, the end of the magnetic poles 32a and 32b) like the deflection electromagnet 30b shown in FIG. 16, for example, the magnetic pole 32a , 32b has no or small curvature of the magnetic field lines 36, that is, the magnetic field generated by the magnetic poles 32a, 32b is uniform or almost uniform, so that the gradient B is not generated or very small. The magnetic field created by the magnetic poles 32a and 32b is more uniform toward the inner side of the inter-pole space 34.

  In order to solve the above-described problem of the deflection electromagnet 30c of the third embodiment, for example, as in the deflection electromagnet 30e of the fifth embodiment shown in FIG. The pair of permanent magnets 75 as described above may be provided between the pair of correction electrodes 60 and at or near the ends of the magnetic poles 32a and 32b. Although illustration is omitted, the entrance side is similarly between the first pair of correction electrodes 61 and the second pair of correction electrodes 62 and at or near the ends of the magnetic poles 32a and 32b. A pair of permanent magnets similar to the permanent magnet 75 may be provided. By doing so, the magnetic field generated by the permanent magnet 75 (an example of the lines of magnetic force thereof is indicated by reference numeral 76) corrects (suppresses) the bending of the magnetic field generated by the magnetic poles 32a and 32b, and the gradient B and thus the gradient B drift are corrected. Can be reduced. As a result, the confinement performance of the electrons 38 is improved.

  The comparison of the confinement performance of the electrons 38 in the conventional example and the deflection electromagnets of the first to fifth embodiments will be described below with reference to the simulation result of the electron trajectory and the electron confinement region.

  Examples of simulation results of electron trajectories in the conventional deflection electromagnet 30 and the deflection electromagnets 30a to 30e of the first to fifth embodiments are shown in FIGS. 23 to 29, only the surfaces 33a and 33b of the magnetic poles 32a and 32b are illustrated. FIG. 24 shows a potential adjustment electrode 52 provided on the surface of the magnetic pole instead of the magnetic pole.

  In this simulation, the magnetic poles 32a and 32b have a total length of 0.3 m in the X direction, a total length of 0.16 m in the Y direction, and an interval between the magnetic poles 32 a and 32 b of 0.065 m. 28 and 29, a permanent magnet 75 having a residual magnetic flux density of 1 T (Tesla), a width (dimension in the X direction) of 5 mm, and a thickness (dimension in the Z direction) of 3 mm is used as the magnetic pole 32a. It is attached to the surfaces 33a and 33b of 32b. The magnitude of the magnetic field created by the magnetic poles 32a and 32b in the center in the X and Y directions of the inter-magnetic pole space 34 is about 10 mT. The ion beam 4 has a cylindrical uniform current, the radius is 0.02 m, the current is 1 mA, the energy is 5 keV, and the ion species is monovalent boron. The equipotential lines 56 of the ion beam 4 are also shown in the drawings. The electrons 38 were emitted from the position indicated by the arrow P in the drawing, that is, from the vicinity of the origin at the center of the inter-magnetic pole space 34. The energy of the electrons 38 was 10 eV.

As shown in FIG. 23, in the conventional bending electromagnet 30, the trajectory of the electrons 38 is greatly deviated from the ion beam 4 in the vicinity of the end portion in the X direction of the inter-pole space 34, and the electrons 38 cannot be confined. The same applies to the case where the potential adjusting electrode 52 is provided and the voltage V ₁ applied thereto is 0V.

In the deflection electromagnet 30a of the first embodiment shown in FIG. 24, the positive voltage V ₁ applied to the potential adjustment electrode 52 is set to 180V. The trajectory of the electrons 38 is closed and the electrons 38 can be confined.

In the second deflection electromagnet 30b shown in FIG. 25, the voltages V ₁ , V ₂ , and V ₃ applied to the potential adjustment electrode 52 and the correction electrodes 63 and 64 are set to 15V, 15V, and −15V, respectively. The voltages V ₂ and V ₃ applied to the inlet-side correction electrodes 61 and 62 (not shown in the figure) were also set to 15V and −15V, respectively. The trajectory of the electrons 38 is closed and the electrons 38 can be confined. In the first embodiment shown in FIG. 24, a high voltage of 180 V is required to confine electrons, but in the second embodiment, the voltage can be lowered to 15 V.

In bending magnet 30c of the third embodiment shown in FIG. 26, the potential adjusting electrode 52, and the voltage V _1, V _2, V ₃ applied to the correction electrodes 63, 64 30 V respectively, 30 V, the -30 V. The voltages V ₂ and V ₃ applied to the inlet-side correction electrodes 61 and 62 (not shown in the figure) were also set to 30 V and −30 V, respectively. The trajectory of the electrons 38 is closed and the electrons 38 can be confined. In this embodiment, the voltage is a little higher, 30V.

In bending magnet 30c of the third embodiment, the potential adjusting electrode 52, voltage V ₁ applied to the correction electrode 63, 64, V _2, V _3, respectively 8V, 8V, in the -8 V, not confined electrons 38 This case is shown in FIG. At this time, the voltages applied to the correction electrodes 61 and 62 (not shown in the figure) on the inlet side were also 8V and -8V, respectively.

When the permanent magnet 75 is added like the deflection electromagnet 30d of the fourth embodiment shown in FIG. 28 (not shown in the figure, a permanent magnet corresponding to the permanent magnet 75 is also added on the entrance side), the above Even if the voltages V ₁ , V ₂ , and V ₃ are lowered to 5 V, 5 V, and −5 V, respectively, the trajectory of the electrons 38 is closed and the electrons 38 can be confined. That is, the voltage can be lowered as compared with the second embodiment shown in FIG.

In the case shown in FIG. 27, the electrons 38 could not be confined. However, if a permanent magnet 75 is added like the deflection electromagnet 30e of the fifth embodiment shown in FIG. 29 (not shown in the figure, it is not on the entrance side). In addition, a permanent magnet corresponding to the permanent magnet 75 is added), and even if the voltages V ₁ , V ₂ , and V ₃ are set to 8V, 8V, and −8V, respectively, as shown in FIG. The orbit is closed and the electrons 38 can be confined.

In the deflecting electromagnet having the structure shown in FIGS. 23 to 29, in order to investigate the confinement range of the electrons 38, the electrons 38 are emitted from the vicinity of the origin at the center of the space 34 between the magnetic poles, Outlines of the confinement region A _C (the hatched region) and the non-confinement region A _N (the region not hatched) are shown in FIGS.

As shown in FIG. 30, in a conventional bending electromagnet 30, confinement region is absent, the ion beam 4 and the entire area of its peripheral surface is unconfined regions A _N.

Figure 31, in the bending magnet 30a of the first embodiment, a case where the voltages V ₁ to 180 V, an ion beam 4 and in the region A _C confinement whole of its periphery.

In bending magnet 30a of the first embodiment, when the voltages V ₁ to 30 V, as shown in FIG. 32, the confinement region A _C is very narrow.

FIG. 33 shows a case where the voltages V ₁ , V ₂ , and V ₃ are set to 30 V, 30 V, and −30 V, respectively, in the deflection electromagnet 30 b of the second embodiment, and the entire region in and around the ion beam 4 is a confinement region. a a _C. Since a voltage lower than that in the case of FIG. 31 is sufficient, the effect is considerably large.

FIG. 35 shows the case where the voltages V ₁ , V ₂ , and V ₃ are set to 30 V, 30 V, and −30 V, respectively, in the deflection electromagnet 30 c of the third embodiment, and the entire region in and around the ion beam 4 is a confinement region. a a _C. Since a voltage lower than that in the case of FIG. 31 is sufficient, the effect is considerably large.

To investigate the difference in effect between the bending magnet 30c of the second embodiment bending magnet 30b of the third embodiment, 15V voltage V _1, V _2, V ₃ respectively, 15V, a voltage in the -15V The confinement area was investigated by lowering. The results are shown in FIGS. 34 and 36, respectively. Since the confinement area A _{C in} FIG. 34 is slightly wider than that in FIG. 36, the confinement performance is slightly better.

FIG. 37 shows a case where the voltages V ₁ , V ₂ , and V ₃ are set to 15V, 15V, and −15V, respectively, in the deflection electromagnet 30d of the fourth embodiment. Results when provided with no permanent magnets (second embodiment) is 34, the same compared to the confinement region A _C is wider at the same voltage.

FIG. 39 shows a case where the voltages V ₁ , V ₂ , and V ₃ are set to 15V, 15V, and −15V, respectively, in the bending electromagnet 30e of the fifth embodiment. It results when provided with no permanent magnets (Third Embodiment) of FIG. 36, the same compared to the confinement region A _C is wider at the same voltage.

In the deflection electromagnet 30d of the fourth embodiment and the deflection electromagnet 30e of the fifth embodiment, the cases where the voltages V ₁ , V ₂ , and V ₃ are lowered to 8V, 8V, and −8V, respectively, are shown in FIGS. 38 and 40, respectively. Show. Towards 38 confinement performance slightly better because the wide little confinement region A _C than Figure 40.

  As described above, the deflection electromagnets 30d and 30e of the fourth and fifth embodiments have high confinement performance of the electrons 38 at a low voltage. If both are strictly observed, the deflecting electromagnet 30d of the fourth embodiment has somewhat higher confinement performance of the electrons 38. Further, the deflection electromagnet 30d of the fourth embodiment is easy to arrange because the correction electrodes 61 and 64 do not have to be arranged outside the magnetic poles 32a and 32b, unlike the deflection electromagnet 30e of the fifth embodiment. . Therefore, it can be said that the deflection electromagnet 30d of the fourth embodiment has the highest practicality.

  The deflection electromagnets 30a to 30e of the above embodiments can be used in an ion beam irradiation apparatus. That is, in the ion beam irradiation apparatus configured to irradiate the target with the ion beam 4 extracted from the ion source, the deflecting electromagnet 30a of the first to fifth embodiments is provided along the path of the ion beam 4 from the ion source to the target. One or more of ~ 30e may be provided. For example, any one of the deflection electromagnets 30a to 30e is used for one or more of the mass separation magnet 6, the energy separation magnet 10, the scanning magnet 12, and the parallelizing magnet 14 of the ion beam irradiation apparatus shown in FIG. Also good.

  By doing so, each deflecting electromagnet can achieve the above-mentioned effect and efficiently neutralize the space charge of the ion beam 4 to suppress the divergence of the ion beam 4, so that ions extracted from the ion source 2 can be suppressed. The transport efficiency of the beam 4 to the target 16 can be improved.

It is a schematic plan view which shows an example of an ion beam irradiation apparatus. It is a figure which shows the outline | summary of the cyclotron motion of an electron. It is a figure which shows the outline | summary of the E * B drift of an electron. It is a figure which shows the outline | summary of the ExB drift of the electron between magnetic poles. It is a figure which shows the outline | summary of the electric field which an ion beam produces. It is a figure which shows the outline | summary of the electric potential and electric field distribution of the ion beam of FIG. It is a figure which shows the outline | summary of the E * B drift of the electron in the case of FIG. 5 and FIG. It is a side view which shows the outline | summary of the E * B drift of the electron in the conventional bending electromagnet. It is sectional drawing which follows the line DD of FIG. It is a top view which shows the outline | summary of the loss by the E * B drift of the electron in the conventional bending electromagnet. 1 is a schematic longitudinal sectional view showing a first embodiment of a bending electromagnet according to the present invention. FIG. 12 is a longitudinal sectional view showing an outline of potential distribution and electron E × B drift when the voltage applied to the potential adjusting electrode is 0 V in the deflection electromagnet shown in FIG. 11. It is a top view which shows the outline | summary of the electric potential distribution near the ion beam of FIG. 12, and an electron drift orbit. FIG. 12 is a longitudinal sectional view showing an outline of potential distribution and electron E × B drift when the voltage applied to the potential adjusting electrode is 100 V in the deflection electromagnet shown in FIG. 11. It is a top view which shows the outline | summary of the electric potential distribution of the ion beam vicinity of FIG. 14, and an electron drift orbit. It is a schematic longitudinal cross-sectional view which shows the exit side half of 2nd Embodiment of the bending electromagnet which concerns on this invention. It is a top view which shows the outline | summary of the direction of the E * B drift of the electron in the bending electromagnet shown in FIG. It is a schematic longitudinal cross-sectional view which shows 3rd Embodiment which shifted the correction electrode of the deflection electromagnet shown in FIG. 16 to the exit side. It is a schematic longitudinal cross-sectional view which shows the exit side half of 4th Embodiment of the bending electromagnet which concerns on this invention. It is a figure which shows the outline | summary of the gradient B drift of an electron by having provided the permanent magnet shown in FIG. 19, and the line of magnetic force has shown only the one side of the X direction. It is a figure which shows the outline | summary of distribution in the different Y coordinate position of the gradient B drift shown in FIG. It is a schematic longitudinal cross-sectional view which shows the exit side half of 5th Embodiment of the bending electromagnet which concerns on this invention. It is a figure which shows an example of the simulation result of the electron orbit in the conventional bending electromagnet. It is a figure which shows an example of the simulation result of the electron orbit in the deflection electromagnet of 1st Embodiment. It is a figure which shows an example of the simulation result of the electron orbit in the deflection electromagnet of 2nd Embodiment. It is a figure which shows an example of the simulation result of the electron orbit in the bending electromagnet of 3rd Embodiment. It is a figure which shows the other example of the simulation result of the electron orbit in the bending electromagnet of 3rd Embodiment. It is a figure which shows an example of the simulation result of the electron orbit in the deflection electromagnet of 4th Embodiment. It is a figure which shows an example of the simulation result of the electron orbit in the bending electromagnet of 5th Embodiment. It is a figure which shows the outline | summary of the electron confinement area | region and the non-confinement area | region in the conventional bending electromagnet. It is a figure which shows an example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 1st Embodiment. It is a figure which shows the other example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 1st Embodiment. It is a figure which shows an example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 2nd Embodiment. It is a figure which shows the other example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 2nd Embodiment. It is a figure which shows an example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 3rd Embodiment. It is a figure which shows the other example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 3rd Embodiment. It is a figure which shows an example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 4th Embodiment. It is a figure which shows the other example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 4th Embodiment. It is a figure which shows an example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 5th Embodiment. It is a figure which shows the other example of the outline | summary of the electron confinement area | region and the non-confinement area | region in the bending electromagnet of 5th Embodiment.

Explanation of symbols

2 Ion source 4 Ion beam 16 Target 30a-30e Bending electromagnet 32a 1st magnetic pole 32b 2nd magnetic pole 34 Space between magnetic poles 38 Electron 52 Potential adjustment electrode 54 Potential adjustment power supply 61-64 Correction electrode 66 Correction power supply 75 Permanent magnet

Claims (8)

A deflection electromagnet having first and second magnetic poles facing each other with a space between magnetic poles through which an ion beam passes, and bending the ion beam passing through the space between the magnetic poles;
A pair of potential adjusting electrodes disposed in the space between the magnetic poles so as to sandwich the path of the ion beam from the same direction as the first and second magnetic poles;
A deflection electromagnet comprising a DC potential adjusting power source for applying a positive voltage to the pair of potential adjusting electrodes.   The voltage applied from the potential adjustment power source to the potential adjustment electrode is higher than the higher one of the potential created by the ion beam at the ion beam entrance end of the potential adjustment electrode and the potential created by the ion beam at the ion beam exit end. The deflection electromagnet according to claim 1, which is a voltage. A deflection electromagnet having first and second magnetic poles facing each other with a space between magnetic poles through which an ion beam passes, and bending the ion beam passing through the space between the magnetic poles;
A first pair of correction electrodes disposed so as to sandwich the path of the ion beam from the same direction as the first and second magnetic poles, closer to the entrance than the center of the space between the magnetic poles in the ion beam passing direction; ,
A second pair of correction electrodes arranged side by side with the first pair of correction electrodes so as to be located outside of the first pair of correction electrodes in the ion beam passage direction;
A third pair of correction electrodes arranged so as to sandwich the path of the ion beam from the same direction as the first and second magnetic poles, closer to the exit than the center in the ion beam passage direction of the space between the magnetic poles; ,
A fourth pair of correction electrodes arranged side by side with the third pair of correction electrodes so as to be located outside the third pair of correction electrodes in the ion beam passage direction;
A first DC correction power source that keeps the potential of the second pair of correction electrodes lower than the potential of the first pair of correction electrodes;
A deflection electromagnet comprising: a second DC correction power source that maintains a potential of the fourth pair of correction electrodes lower than a potential of the third pair of correction electrodes.   The deflection electromagnet according to claim 3, wherein the first correction power source and the second correction power source are the same power source. The first and second pairs of correction electrodes are disposed in the vicinity of the entrance end in the ion beam passage direction of the space between the magnetic poles;
The deflection electromagnet according to claim 3 or 4, wherein the third and fourth pairs of correction electrodes are arranged in the vicinity of the exit end in the ion beam passage direction of the space between the magnetic poles. The first pair of correction electrodes is disposed near the entrance end in the ion beam passage direction of the space between the magnetic poles;
The second pair of correction electrodes is disposed outside the entrance end in the ion beam passage direction of the inter-magnetic pole space;
The third pair of correction electrodes is disposed near the exit end in the ion beam passing direction of the space between the magnetic poles;
5. The deflection electromagnet according to claim 3, wherein the fourth pair of correction electrodes is disposed outside an exit end in an ion beam passing direction of the space between the magnetic poles. Surfaces of the first and second magnetic poles or in the vicinity thereof are disposed between the first pair of correction electrodes and the second pair of correction electrodes so as to cross the path of the ion beam. A first pair of permanent magnets for creating a magnetic field in a direction that intensifies the magnetic field produced by the first and second magnetic poles;
Surfaces of the first and second magnetic poles or in the vicinity thereof are disposed between the third pair of correction electrodes and the fourth pair of correction electrodes so as to cross the ion beam path. The deflecting electromagnet according to claim 3, 4, 5, or 6, further comprising a second pair of permanent magnets for generating a magnetic field in a direction for strengthening the magnetic field generated by the first and second magnetic poles. An ion beam irradiation apparatus configured to irradiate a target with an ion beam extracted from an ion source,
An ion beam irradiation apparatus comprising at least one deflection electromagnet according to claim 1 in a path of an ion beam from the ion source to the target.

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