JP5527617B2 - Ion source - Google Patents

Description

  The present invention relates to an ion source including magnetic field generation means for capturing electrons flowing into the ion source from the downstream side of the ion source.

  In an ion source of an ion beam irradiation apparatus such as an ion implantation apparatus, an ion doping apparatus, or an ion beam alignment apparatus, an electrode group including a plurality of electrodes called an extraction electrode system is used to extract an ion beam. .

  FIG. 2 of Patent Document 1 discloses an example of such an extraction electrode system. Here, four electrodes of a plasma electrode, an extraction electrode, a suppression electrode, and a ground electrode are used as electrodes constituting the extraction electrode system.

  The plasma electrode is an electrode that determines the energy of the ion beam to be extracted. The extraction electrode is an electrode for generating a potential difference with the plasma electrode and extracting the ion beam from the plasma by an electric field thereby. The suppression electrode is an electrode that suppresses electrons from flowing into the ion source from the downstream side of the ion source, and is set so that the potential of the electrode becomes a negative potential with respect to the ground potential. It has the function of repelling the electrons it has to the downstream side of the ion source. The ground electrode is an electrode that is electrically grounded to fix the potential.

  The number of electrodes used in such an extraction electrode system is not limited to four. For example, FIGS. 1 and 2 of Patent Document 2 disclose an extraction electrode system composed of three electrodes including a plasma electrode, a suppression electrode, and a ground electrode. Using such an extraction electrode system, An ion beam may be extracted from the ion source.

JP 2007-115511 (FIG. 2, paragraphs 0037 to 0039) JP-A-5-82075 (FIGS. 1 and 2, paragraph 0011)

  A plurality of power supplies are used to set the potential of each electrode used in the extraction electrode system. Since such a power supply is expensive, there is a demand for not using it as much as possible.

  In order to reduce the number of power sources, it is conceivable to reduce the number of electrodes, but if the electrodes are simply removed, the function of the ion source will be hindered.

  Therefore, an object of the present invention is to provide a novel ion source having a function equivalent to that of a conventional ion source although the number of electrodes is smaller than that of a conventional ion source.

The ion source of the present invention is a positive ion source that does not include a suppression electrode that suppresses the inflow of electrons from the downstream side and is negative with respect to the ground potential, and is disposed along the extraction direction of the ion beam. And a magnetic field generating means having at least a pair of magnetic poles arranged downstream of the electrodes and generating a magnetic field across the ion beam drawn from the ion source. It is said.

  If the ion source includes such a magnetic field generating means, the number of electrodes can be reduced as compared with the conventional ion source, and the function equivalent to that of the conventional ion source can be provided.

  Further, in order to correct the traveling direction of the ion beam deflected by the magnetic field generating means, the magnetic field generating means is a pair of pairs arranged with the ion beam being sandwiched at different positions along the extraction direction of the ion beam. It is desirable that a first magnetic pole pair and a second magnetic pole pair having magnetic poles are provided, and the directions of magnetic fields generated between the magnetic pole pairs are opposite to each other.

  By adopting such a configuration, the traveling direction of the ion beam can be corrected.

  Further, it is desirable that the first magnetic pole pair and the second magnetic pole pair are made of a magnetic material, and the magnetic materials constituting each magnetic pole pair are connected via a permanent magnet.

  By adopting such a configuration, the magnetic field generating means can be made simple.

  In addition, the magnetic field generated between the first magnetic pole pair and the second magnetic pole pair is configured so that a Lorentz force having an opposite direction and a substantially equal magnitude acts on the ion beam. You can keep it.

  When such a configuration is adopted, the traveling direction of the ion beam can be kept substantially the same before and after the ion beam passes through the magnetic field generating means. Therefore, the optical system of the entire ion beam irradiation apparatus can be easily designed.

  In addition, the magnetic pole may be formed with an electrode support groove extending in a direction substantially perpendicular to the extraction direction of the ion beam.

  If such a configuration is adopted, the electrode can be supported by the magnetic field generating means, so that it is not necessary to provide a special support member for the electrode.

  The electrode arranged on the most downstream side may be arranged on the surface of the magnetic pole facing the electrode.

  Even if such a configuration is used, the electrode can be supported by the magnetic field generating means in the same way as the configuration described above, so that it is not necessary to provide a special electrode support member.

  Since magnetic field generating means for suppressing the inflow of electrons from the downstream side of the ion source is used instead of the suppression electrode used in the conventional extraction electrode system, the number of electrodes can be reduced as compared with the conventional ion source. In addition to being able to, it can have the same function as a conventional ion source.

It is a top view which shows an example of the ion source used by this invention. It is a top view showing a mode that the ion source of FIG. 1 was seen from the X direction. The state when electrons flow into the magnetic field generating means is shown. It is another example of the magnetic field generation means which has a 1st, 2nd magnetic pole pair. It is an example of the magnetic field generation means which has a pair of magnetic pole. It is another example of the magnetic field generation means which has a pair of magnetic pole. It is an example of the electrode support structure formed in the magnetic field generation means. It is another example of the electrode support structure formed in the magnetic field generation means.

  In the present invention, the Z direction is the extraction direction of the ion beam extracted from the ion source, and the two directions orthogonal to the Z direction are the X direction and the Y direction. In the present invention, the downstream side means an ion beam extraction direction side (Z direction side).

  FIG. 1 shows an example of an ion source used in the present invention. This ion source 1 is a kind of so-called bucket type ion source.

  The ion source 1 includes a rectangular plasma generation container 4 from which a substantially ribbon-shaped ion beam 3 is drawn. In the following embodiments, the shape of the ion beam 3 extracted from the ion source 1 will be described as having a long side in the X direction and a short side in the Y direction. However, in the ion source 1 to which the present invention is applied, The shape of the ion beam 3 used is not limited to this.

  A gas source 2 is attached to the plasma generation container 4 via a valve (not shown), and a gas that is a raw material of the ion beam 3 is supplied from the gas source 2. Note that a gas flow rate controller (mass flow controller) (not shown) is connected to the gas source 2, thereby adjusting the amount of gas supplied from the gas source 2 to the inside of the plasma generation container 4.

A plurality of U-shaped filaments 8 are attached to one side surface of the plasma generation container 4 along the X direction. Then, using the power V _F which is connected between the terminals of the filament 8, and it is configured to allow adjustment of the amount of current flowing through the respective filaments 8. With such a configuration, the current density distribution of the ion beam 3 extracted from the ion source 1 can be adjusted.

  By passing an electric current through the filament 8 and heating the filament 8, electrons are emitted therefrom. The electrons collide with the gas supplied into the plasma generation container 4 to cause ionization of the gas, and plasma 9 is generated in the plasma generation container 4.

  In the ion source 1, a plurality of permanent magnets 12 are attached along the outer wall of the plasma generation container 4. By this permanent magnet 12, a cusp magnetic field is formed in the inner region of the plasma generation container 4, and the electrons emitted from the filament 8 are confined in the predetermined region.

The ion source 1 has three electrodes as an extraction electrode system, and is arranged in the order of the plasma electrode 5, extraction electrode 6, and ground electrode 7 along the Z direction from the plasma generation container 4. Each of these electrodes is provided with a plurality of holes, and the ion beam 3 is extracted through these holes. Since the functions of these electrodes are the same as those described in the prior art, description thereof is omitted. The potentials of the electrodes and the plasma generation container 4 are set to different values by a plurality of power sources (V _{1 to} V ₄ ), and the members are attached via the insulator 10. In addition, the plasma electrode 5 mentioned above may be called an acceleration electrode.

  In the conventional ion source, as one of the electrode groups described above, an electrode set to a negative potential of about 500 V with respect to the potential of the ground electrode is provided on the downstream side of the ion source (the ion source in the present invention). Although a suppression electrode that suppresses electrons flowing into the ion source from the Z-direction side is provided, this suppression electrode is not provided in the present invention. Instead, magnetic field generating means 11 described later is provided.

  The suppression electrode is an electrode that does not affect the energy and spread of the ion beam 3 extracted from the ion source 1. In addition, there is a high possibility that a large current flows in the suppression power source used for setting the potential of the suppression electrode when abnormal discharge occurs between the electrodes of the extraction electrode system. Therefore, the capacity of the suppression power source must be made sufficiently large. In that case, the price of the power supply becomes expensive. Focusing on this point, the present invention eliminates the suppression electrode from the extraction electrode system of the ion source.

  The magnetic field generation means 11 of this embodiment has a first magnetic pole pair 20 and a second magnetic pole pair 21 along the Z direction, and the ion beam 3 passes between the magnetic pole pairs 20 and 21. ing. FIG. 1 shows a state of one side of the magnetic pole pairs 20 and 21 arranged with the ion beam 3 interposed therebetween.

  Each of the magnetic pole pairs 20 and 21 is constituted by an individual magnetic body 14, and the magnetic bodies 14 constituting different magnetic pole pairs are connected via a permanent magnet 13. The same configuration as that shown in FIG. 1 is also provided on the opposite side in the Y direction across the ion beam 3. However, the direction of the polarity of the permanent magnet 13 provided between the magnetic bodies 14 constituting different magnetic pole pairs is opposite to that shown in FIG.

  In the magnetic field generating unit 11 having the above-described configuration, the Lorentz force F1 acts on the ion beam 3 in the X direction approximately in the first magnetic pole pair 20. On the other hand, in the second magnetic pole pair 21, the Lorentz force of F2 acts on the ion beam 3 in a direction approximately opposite to the X direction. With such a configuration, the ion beam 3 deflected by the first magnetic pole pair 20 can be bent back in the opposite direction by the second magnetic pole pair 21, so that the traveling direction of the ion beam 3 is corrected. I can do it.

  The traveling direction of the ion beam 3 depends on the degree of miniaturization of a device manufactured by the ion beam irradiation apparatus, the performance and configuration of an optical element (analysis electromagnet, acceleration tube, etc.) disposed downstream of the ion source 1, or the ion source. Considering factors such as the distance from 1 to the target (wafer, glass substrate, etc.) irradiated with the ion beam 3, it does not necessarily have to be parallel to the Z direction.

  Since an allowable range is provided according to the configuration of the ion beam irradiation apparatus and the device to be manufactured, the traveling direction of the ion beam 3 after passing through the magnetic field generating means 11 is corrected so as to fall within such an allowable range. It is enough if it is done. Therefore, the Lorentz forces F1 and F2 acting on the ion beam 3 described above do not have to be the same magnitude.

  However, considering the optical design of the entire ion beam irradiation apparatus, in order to easily do this, it is desirable to keep the traveling direction substantially the same before and after the ion beam 3 passes through the magnetic field generating means 11. . Therefore, from such a viewpoint, it is desirable that the Lorentz forces F1 and F2 acting on the ion beam 3 be substantially the same.

  When the Lorentz force F1 and the Lorentz force F2 are opposite in direction and have substantially the same magnitude, the position A1 of the central trajectory of the ion beam 3 before entering the magnetic field generation means 11 and the magnetic field generation means 11 after exiting. The position A2 of the center trajectory 3 of the ion beam is separated by a distance D in the X direction. However, the deviation of the central orbit is not a problem.

  In order to suppress the inflow of electrons to the ion source 1 side using the magnetic field generating means 11, it is sufficient to form a magnetic field having a small magnetic flux density such as several mT. Although depending on the energy value of the ion beam 3 extracted from the ion source 1 and the type of ions, the amount by which the ion beam 3 is deflected by the magnetic field generation means 11 is not so large. Therefore, the value of the distance D is not so large.

  The distance D is not so large, but if the value still needs to be small, the distance between the first magnetic pole pair 20 and the second magnetic pole pair 21 in the Z direction is reduced. Just keep it. In this case, since the ion beam 3 is first deflected and then immediately deflected in the reverse direction, the distance D can be reduced. However, if the distance between the first magnetic pole pair 20 and the second magnetic pole pair 21 is too narrow, the magnetic field generated by the permanent magnet 13 may affect the ion beam 3. For this reason, the distance between the first magnetic pole pair 20 and the second magnetic pole pair 21 needs to be set to an appropriate value in consideration of the influence of the magnetic field generated by the permanent magnet 13 on the ion beam 3. There is.

  Further, in anticipation of the distance D, the ion source 1 may be preliminarily shifted to the opposite side in the X direction. With such an arrangement, it is possible to eliminate the influence of the deviation of the center orbit of the ion beam 3 in the beam optical system arranged on the downstream side of the ion source 1.

FIG. 2 illustrates a state when the ion source 1 of FIG. 1 is viewed from the X direction. In FIG. 2, descriptions of power sources (V _F , V _{1 to} V ₄ ) connected to the plasma electrode 5, the filament 8, and the like and grounding (ground) are omitted.

  Each magnetic body 14 constituting the first magnetic pole pair 20 and the second magnetic pole pair 21 protrudes toward the ion beam 3 along the Y direction. By configuring the magnetic body 14 in this way, it is possible to easily generate a magnetic field across the ion beam 3 drawn in the Z direction.

  In addition, the direction of the magnetic field generated in the first magnetic pole pair 20 and the direction of the magnetic field generated in the second magnetic pole pair 21 are opposite to each other, and the Lorentz force F1 and the Lorentz force in the reverse direction due to such a magnetic field are reversed. F2 is generated.

  The magnetic field generating means 11 may be attached by bolts or the like to the inner wall of a support frame of a ground electrode (not shown) extending from the lower surface of the ground electrode 7 in the Z direction. 1 may be attached to the flange.

  In FIG. 3, the state in which electrons flow into the magnetic field generation means 11 from the downstream side of the ion source 1 is depicted. When the electrons enter the magnetic field region formed in the second magnetic pole pair 21, the electrons travel along the magnetic field lines while spiraling. As described above, electrons are captured by the magnetic field generation means 11, so that it is possible to prevent the electrons from entering the upstream side (opposite side in the Z direction) of the magnetic field generation means 11.

  4A to 4E show modified examples of the magnetic field generating means 11 described so far. These configurations will be described below. In each figure, the directions of the X, Y, and Z axes are common, and the arrows drawn on the magnetic pole pairs 20 and 21 indicate the direction of the magnetic field.

  In FIG. 4A, each magnetic pole pair 20 and 21 is composed of a permanent magnet 13. Although the number of permanent magnets 13 is increased by two as compared with the configuration described in FIGS. 1 to 3, the configuration shown in FIG. 4A may be adopted as the magnetic field generating means 11 of the present invention.

  Also in FIG. 4B, each magnetic pole pair 20, 21 is constituted by a permanent magnet 13 as in FIG. 4A. Since the permanent magnet 13 does not need to be provided at the end of the magnetic body 14, it goes without saying that the configuration shown in FIG. Further, in both FIGS. 4A and 4B, the magnetic material 14 may be a non-magnetic material. Furthermore, it may be configured such that each magnetic pole pair is individually supported in the Z direction regardless of whether it is a magnetic body or a non-magnetic body.

  FIG. 4C illustrates a configuration similar to the magnetic field generation unit 11 illustrated in FIGS. As shown in FIG. 4C, the magnetic pole pairs 20 and 21 may be configured to protrude toward the ion beam 3 from the middle of the magnetic body 14 extending along the Z direction.

  In FIG. 4D, the first magnetic pole pair 20 is constituted by a permanent magnet 13, and the second magnetic pole pair 21 is constituted by a magnetic body 14. Since the magnetic body 14 constituting the second magnetic pole pair 21 is connected to the permanent magnet 13 constituting the first magnetic pole pair 20, the number of permanent magnets 13 is the same as in the example of FIG. Can be reduced. 4 (d), the first magnetic pole pair 20 may be composed of the magnetic body 14, and the second magnetic pole pair 21 may be composed of the permanent magnet 13.

  Furthermore, as disclosed in FIG. 4 (e), instead of the permanent magnet 13, a coil 15 is wound around each magnetic body 14 arranged in the Y direction, and a magnetic field is generated by passing an electric current therethrough. It may be generated. When the coil 15 is wound around each magnetic body 14 in the same direction, the direction of the current flowing through each coil is reversed. On the contrary, when the coil 15 is wound around each magnetic body 14 in the opposite direction, the direction of the current flowing through each coil is kept the same. In the example of FIG. 4E, the direction of the coil 15 wound around the left magnetic body 14 is right-handed, whereas the direction of the coil 15 wound around the right magnetic body 14 is left-handed. It has become. For this reason, a current is supplied to each coil 15 in the same direction (from the top to the bottom in the direction of the Z direction). By using such a configuration, it is possible to generate a magnetic field in the opposite direction so as to cross the ion beam 3 as in the other examples.

  When the coil 15 is used, the strength of the magnetic field can be controlled. Therefore, it is possible to measure the traveling direction of the ion beam 3 on the downstream side of the ion source 1 and finely adjust the traveling direction of the ion beam 3 by the magnetic field generating unit 11 according to this measurement. Further, in FIG. 4 (e), the magnetic bodies 14 constituting the magnetic pole pairs 20 and 21 are integrated, but these are separated separately and the coil 15 is wound around each. Also good. Then, the strength of the magnetic field formed by each magnetic pole pair can be finely adjusted by each magnetic pole pair.

  4 (a) to 4 (e) show only the state in the YZ plane, the magnetic field generating means 11 described here also has a ribbon-like ion beam having a long side in the X direction. 3, it has a length in the X direction as in the magnetic field generating means 11 shown in FIG. 1.

  5A to 5C illustrate an example of the magnetic field generating unit 11 having a pair of magnetic poles 22. Similar to FIG. 4, the directions of the X, Y, and Z axes are common in each of the drawings, and an arrow drawn on the magnetic pole pair indicates the direction of the magnetic field. When the energy of the ion beam 3 is relatively high (for example, 300 keV or more), the ion beam 3 is hardly deflected by the magnetic field generated by the magnetic field generation unit 11. Even when the energy of the ion beam 3 is low, as described above, if the traveling direction of the ion beam 3 that has passed through the magnetic field generating means 11 is within an allowable range, a magnetic field for bending back the ion beam 3 is generated. There is no need to generate it. Therefore, as shown in FIGS. 5A to 5C, a magnetic field that traverses the ion beam 3 may be generated only in one direction.

  FIG. 5A discloses a magnetic field generating means 11 composed of a pair of permanent magnets 13 and a magnetic body 14 that supports the permanent magnets 13. In this example, the permanent magnets 13 constituting the pair of magnetic poles 22 are arranged at the central portion in the Z direction of the magnetic body 14, but these may be provided at the end portions. Moreover, although the magnetic body 14 is used as a support member for the permanent magnet 13, it may be a non-magnetic body.

  FIG. 5B discloses magnetic field generation means 11 in which a magnetic body 14 supporting a pair of permanent magnets 13 protrudes in the Y direction and forms a pair of magnetic poles 22. Such a configuration may be adopted.

  FIG. 5C discloses magnetic field generation means 11 in which a coil 15 is wound around a set of magnetic bodies 14. What is necessary is just to comprise similarly to the example of FIG.4 (e) about the direction which winds the coil 15, and direction of the electric current I sent through it.

  5A to 5C, when the ribbon-like ion beam 3 having a long side in the X direction is handled, it is long in the X direction in the same way as the magnetic field generating means 11 shown in FIG. Have

  FIG. 6 shows another example of the magnetic field generating means 11 having a pair of magnetic poles 22. In this example, portions protruding in the Y direction of the magnetic body 14 constitute a pair of magnetic poles 22. In this case, when the ion beam 3 passes through a position close to the permanent magnet 13, the shape of the ion beam 3 may be deformed due to the influence of a strong magnetic field from the permanent magnet 13. Therefore, it is desired that the pair of magnetic poles 22 through which the ion beam 3 passes is sufficiently separated from the permanent magnet 13.

  FIG. 7 shows an example of an electrode support structure formed in the magnetic field generating means. An electrode support groove 16 extending in a direction substantially orthogonal to the extraction direction of the ion beam 3 is formed in the first magnetic pole pair 20 disposed on the extraction electrode system side that constitutes the magnetic field generation means 11.

  In this example, the ground electrode 7 located closest to the first electrode pair 20 is accommodated in the electrode support groove 16 by sliding. In this case, the magnetic body 14 that supports the ground electrode 7 may be grounded without electrically grounding the ground electrode 7 itself. In this example, the magnetic field generating means 11 has a configuration having the first magnetic pole pair 20 and the second magnetic pole pair 21, but the magnetic field generating means 11 having the configuration having the pair of magnetic poles 22 as described above is used. The electrode support groove 16 described here may be provided.

  FIG. 8 shows another example of the electrode support structure formed in the magnetic field generating means. In FIG. 8A, the upper surface of the first magnetic pole pair 20 arranged on the extraction electrode system side constituting the magnetic field generating means 11 is used as an electrode support surface 17, and the ground electrode 7 is fixed thereto with a bolt 18 or the like. . This is illustrated in FIG.

  As in the example of FIG. 7, the example of FIG. 8 may be applied to the magnetic field generating means 11 having the pair of magnetic poles 22 described in FIGS. 5 and 6.

  By providing such an electrode support surface 17 in a part of the magnetic field generating means 11, it is not necessary to prepare a separate electrode support member.

<Other variations>
In the present invention, a bucket type ion source has been described as an example. However, the present invention is not limited to this type of ion source. For example, an ion source having a Freeman type, a Bernas type, or an indirectly heated cathode may be used.

  The ion beam 3 extracted from the ion source has been described by taking the ribbon-shaped ion beam 3 having a long side in the X direction and a short side in the Y direction as an example, but the shape of the extracted ion beam 3 is as follows. It is not limited to this. For example, the shape of the extracted ion beam may be a spot shape.

  Further, the number of filaments 8 may be one instead of a plurality. The number of electrode groups constituting the extraction electrode system may be any as long as it does not have a suppression electrode.

  On the other hand, in the embodiment described in the present invention, the center of the ion beam 3 is positioned at the center between each pair of magnetic poles, but the center position of the ion beam 3 may be shifted to one magnetic pole side. . However, when the center position is located in the center between the magnetic poles, the ion beam 3 is deflected with symmetry when passing through the magnetic field, so that it is easy to handle in the optical system following the ion source. It can be said.

  The electrode used as the extraction electrode system is not limited to the porous electrode, and may be an electrode having a slit.

  Further, in the present embodiment, the direction of the magnetic field generated by the magnetic field generation unit 11 and the traveling direction of the ion beam 3 are illustrated as being substantially orthogonal to each other, but such a relationship is not necessarily required. For example, the direction of the magnetic field generated by the magnetic field generating means 11 and the traveling direction of the ion beam 3 may be obliquely intersected, and the magnetic field generated by the magnetic field generating means 11 is formed so as to cross the ion beam 3. As long as they are, they may have any relationship.

  In addition to the above, it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

1. 2. ion source Ion beam4. 4. Plasma generation container 5. Plasma electrode Extraction electrode 7. Ground electrode 8. Filament 9. Plasma 10 Insulator 11. Magnetic field generating means 13. Permanent magnet 14. Magnetic body 16. Electrode support groove 17. Electrode support surface 20. First magnetic pole pair 21. Second pole pair

Claims (6)

A positive ion source that does not include a suppression electrode that suppresses the inflow of electrons from the downstream side and has a negative potential with respect to the ground potential
A plurality of electrodes arranged along the ion beam extraction direction;
An ion source comprising: at least a pair of magnetic poles disposed at a downstream side of the electrode and generating a magnetic field across the ion beam drawn from the ion source.   The magnetic field generation means includes a first magnetic pole pair and a second magnetic pole pair having a pair of magnetic poles arranged at different positions along the extraction direction of the ion beam and sandwiching the ion beam. The ion source according to claim 1, wherein directions of magnetic fields generated between the magnetic pole pairs are opposite to each other.   The first magnetic pole pair and the second magnetic pole pair are made of a magnetic material, and the magnetic materials constituting each magnetic pole pair are connected via a permanent magnet. Ion source.   The Lorentz force acting in the opposite direction and substantially equal in magnitude to the ion beam is exerted by the magnetic field generated between the first magnetic pole pair and the second magnetic pole pair. The ion source according to 2 or 3.   5. The ion source according to claim 1, wherein an electrode support groove extending in a direction substantially perpendicular to the ion beam extraction direction is formed in the magnetic pole. 5. The ion source according to claim 1, wherein the electrode arranged on the most downstream side is arranged on a surface of the magnetic pole facing the electrode.