JP3858682B2 - Extraction electrode system of ion implanter and ion implanter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an extraction electrode system and an ion implantation apparatus for extracting ions generated by an ion source.
[0002]
[Prior art]
In an ion implantation apparatus used for implanting hydrogen ions or the like into a silicon wafer, ion implantation is performed by irradiating a silicon wafer with an ion beam generated by an ion beam generation unit.
FIG. 1 is a configuration diagram schematically showing an example of an ion implantation apparatus. In the figure, an ion implantation apparatus 1 has an ion beam generator 2 that generates an ion beam (IB) irradiated to a silicon wafer W. An enlarged view of the ion beam generator 2 is shown in FIG. In general, the ion beam generator 2 includes an ion source 5 that ionizes a desired element (molecule), and extraction electrodes 8 and 9 that extract ions generated by the ion source 5.
[0003]
[Problems to be solved by the invention]
In the conventional ion implantation apparatus, when the ion beam is extracted by the extraction electrode, the ion beam is bent with respect to a desired direction, and the traveling direction of the ion beam may be shifted. For this reason, a part of the ion beam hits an electrode or the like provided around the beam line until the ion beam reaches the wafer, and as a result, there is a problem that the ion beam is not efficiently implanted into the wafer. It was.
[0004]
Specifically, as shown in FIG. 3, in the extraction electrode system 7, when the attachment plates 13 and 15 of the extraction electrodes 8 and 9 are formed of graphite or the like which is the same non-magnetic material as the electrode bodies 12 and 14. When the ion beam IB is extracted by the extraction electrodes 8 and 9, the ion beam IB is affected by the magnetic field of the source magnet 6. That is, when the magnetic field lines emitted from the source magnet 6 pass through the extraction electrodes 8 and 9, the magnetic field penetrates into the slits 12a and 14a that are the path of the ion beam IB, so that the ion beam IB is directed in a desired direction. It is drawn out in a bent state, and the traveling direction of the ion beam IB is shifted. Such defects are caused by hydrogen ions (H ⁺ , H ²⁺ Etc.) and helium ions (He ⁺ , He ²⁺ Etc.) are particularly noticeable.
[0005]
When the deviation of the traveling direction of the ion beam IB occurs in this way, a part of the ion beam IB may hit the plate 20 without passing through the slit of the plate 20 of the mass resolving unit 18. In this case, the ion beam IB reaching the wafer W is lost, and the ion beam IB cannot be efficiently driven into the wafer W.
[0006]
In order to solve this problem, when the mounting plates 13 and 15 of the extraction electrodes 8 and 9 are formed of a magnetic material, the magnetic lines of force emitted from the source magnet 6 are converted into the electrode body 12 of the extraction electrodes 8 and 9 as shown in FIG. , 14, it approaches the mounting plate 13, 15 side, which is a magnetic body, and passes through the slits 12 a, 14 a. That is, the magnetic field does not penetrate into the slits 12a and 14a that are the path of the ion beam IB.
[0007]
Thus, since the magnetic field of the source magnet 6 is shielded in the path of the ion beam IB, when the ion beam IB is extracted by the extraction electrodes 8 and 9, the ion beam IB is greatly affected by the magnetic field from the source magnet 6. As a result, the ion beam IB is extracted in a substantially desired direction. Therefore, most of the ion beam IB from the extraction electrode system 7 passes through the slit of the plate 20 without hitting the plate 20 of the mass resolving unit 18. Thereby, the loss of the ion beam IB is reduced, the irradiation amount of the ion beam IB to the wafer W is increased, and the ion beam IB is efficiently driven into the wafer W. As a result, ion implantation can be performed efficiently. In addition, the ion beam IB is less likely to hit the electrode material and the protective member, and accordingly, it is considered that the lifetime of the member is increased, the particle contamination is reduced, the lifetime of the vacuum pump is extended, and the like.
[0008]
However, if the mounting plate 13 of the extraction electrode 8 is formed of a magnetic material having a large relative magnetic permeability, the magnetic field (lines of magnetic force) of the source magnet 6 when the extraction electrode 8 is brought close to the ion source 5 as shown in FIG. ) Approaches the mounting plate 13 side of the extraction electrode 8 from the inside of the ion source 5, and the magnetic field in the source magnet 6 is reduced. Thereby, since the magnetic energy from the source magnet 6 is reduced with respect to the plasma formed inside the ion source 5, the ionization of the source gas is not promoted inside the ion source 5, and further, the plasma state Becomes unstable, and a desired beam cannot be obtained.
[0009]
Here, when the acceleration voltage applied to the extraction electrode system 7 is large, a sufficient extraction electric field for extracting ions from the ion source 5 can be secured even if the interval between the ion source 5 and the extraction electrode 8 (hereinafter referred to as source gap) is widened. Therefore, ions can be efficiently extracted, and the irradiation amount of the ion beam IB to the wafer W can be made sufficient.
However, when the acceleration voltage applied to the extraction electrode system 7 is small, the extraction electrode 8 cannot be brought close to the ion source 5 in order to prevent the magnetic lines of force in the ion source 5 from being attracted to the extraction electrode 8. The extraction electric field for extracting ions from 5 cannot be sufficiently secured.
For this reason, ions cannot be efficiently extracted from the ion source 5, and the irradiation amount of the ion beam IB to the wafer W is reduced.
[0010]
That is, in order to stabilize the plasma in the ion source, when the ion acceleration voltage is lowered by increasing the distance between the ion source and the extraction electrode by a certain distance or more, (extraction electric field) = (acceleration voltage) / (ion source and extraction) The extraction electric field is lowered according to the relational expression of (electrode spacing), and the ion beam extracted from the ion source becomes small. That is, as the acceleration voltage is lowered, the ion beam becomes smaller, which causes a problem that the ion beam cannot be efficiently implanted into the substrate.
[0011]
In view of the above problems, an object of the present invention is to extract an ion beam efficiently even if the acceleration voltage is small and to extract an ion beam in a predetermined direction and An ion implanter is provided.
[0012]
[Means for Solving the Problems]
As a result of extensive studies, the inventors of the present invention have made a magnetic body as described above in order to prevent the ion beam from being bent due to the influence of the magnetic field of the source magnet disposed around the ion source. Although multiple extraction electrodes have been adopted, when the magnetic extraction electrode is brought close to the ion source, the magnetic field in the ion source is affected by the magnetic extraction electrode, and the magnetic force in the ion source is reduced, resulting in an unstable plasma state. The inventors have found that it becomes stable and have completed the present invention.
[0013]
That is, according to the present invention, provided in the ion beam generating chamber of the ion implantation apparatus, The source magnet's magnetic field was applied Ions generated by the ion source , In a direction perpendicular to the magnetic field An extraction electrode system comprising two or more extraction electrodes for extracting and generating an ion beam, the extraction electrode having an electrode body and a mounting plate, and mounting the extraction electrode at least at a position closest to the ion source An extraction electrode system of an ion implantation apparatus is provided in which the relative permeability of the plate is smaller than the relative permeability of the mounting plate of at least one other set of extraction electrodes.
[0014]
Thus, by making the relative permeability of the attachment plate of the extraction electrode closest to the ion source out of the extraction electrode system composed of a plurality of extraction electrodes smaller than other attachment plates, the elements in the ion source The extraction electrode can be brought closer to the ion source while suppressing the reduction of the magnetic force from the source magnet that promotes the ionization of the ion source. For this reason, the extraction electric field for extracting an ion beam from an ion source can be improved.
[0015]
In addition, since at least one of the other extraction electrode mounting plates is formed of a magnetic material having a large relative permeability, the magnetic lines of force approach the mounting plate portion side, which is a magnetic material. The penetration of the magnetic field into a slit is reduced. For this reason, when the ion beam is extracted by the extraction electrode, the ion beam is hardly affected by the magnetic field of the source magnet, and the ion beam is extracted in a desired direction.
[0016]
Therefore, if the extraction electrode system according to the present invention is used in an ion implantation apparatus, the ion beam can be efficiently extracted by bringing the extraction electrode system close to the ion source and at the same time, the deviation of the ion beam traveling direction is reduced. In addition, the ion beam can be efficiently injected into the substrate (wafer) while suppressing the loss of the ion beam.
[0017]
In this case, it is preferable that the extraction electrode mounting plate located closest to the ion source is made of a non-magnetic material. Moreover, it is preferable that the other extraction electrode mounting plate is made of a magnetic material.
As a result, the influence of the magnetic field of the source magnet on the ion beam can be further reduced, and the ion beam can be driven into the wafer more efficiently.
[0018]
As the nonmagnetic material, graphite, carbon, or tungsten is preferable. Moreover, as a magnetic body, the stainless steel which has magnetism, or what gave the corrosion-resistant coating to the surface of iron is preferable (Claim 5).
Thereby, it is possible to obtain an extraction electrode having high heat resistance or high corrosion resistance without affecting the magnetic force in the ion source.
[0019]
Further, when the electrode main body and the mounting plate can be integrally formed, the electrode main body and the mounting plate of the extraction electrode can be integrally formed (Claim 6).
That is, if the electrode body and the mounting plate of the extraction electrode are integrated, the number of parts of the extraction electrode can be reduced, and the extraction electrode can be reduced in size and weight.
[0020]
Further, the extraction electrode that is closest to the ion source can be arbitrarily set with a voltage (Claim 7), and it is preferable that the position can be set independently of other extraction electrodes. (Claim 8).
In this case, the extraction electric field can be optimized by adjusting the voltage and position of the extraction electrode that is closest to the ion source, and ions can be stably extracted from the ion source.
[0021]
The extraction electrode system preferably extracts hydrogen ions generated by the ion source (claim 9).
That is, if the extraction electrode system of the present invention is used for an ion source that generates hydrogen ions, which are light elements, the hydrogen ions are extracted and the hydrogen ion beam is efficiently injected into the wafer without shifting the traveling direction. be able to.
[0022]
Furthermore, according to the present invention, there is provided an ion implantation apparatus comprising at least the extraction electrode system (claim 10).
If such an ion implantation apparatus is used, the loss of the ion beam can be suppressed and the ion beam can be efficiently implanted into the substrate.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. However, the present invention is not limited to these embodiments.
The present invention is characterized by an extraction electrode system. Typically, at least an extraction electrode closest to the ion source surrounds an electrode body having a slit for passing an ion beam, and the electrode body. And an electrode body having a small relative permeability fixed in the chamber and an extraction electrode on the side far from the ion source having a slit for passing an ion beam; And an attachment plate having a large relative permeability that is configured to surround the electrode body and is fixed in the chamber.
[0024]
FIG. 6 shows a path of magnetic lines of force in one embodiment of the extraction electrode system according to the present invention.
In this embodiment, the mounting plate 13 for the extraction electrode 8 is made of graphite, which is the same nonmagnetic material as the electrode bodies 12 and 14, and the mounting plate 15 for the extraction electrode 9 is formed of stainless steel, which is a magnetic material. With such a configuration, in order to increase the extraction electric field and increase the ion extraction efficiency, even if the extraction electrode 8 is brought close to the ion source 5 as shown in FIG. Sufficient lines of magnetic force can be secured inside. Therefore, the source gas can be efficiently ionized inside the ion source 5 and the ions can be extracted from the ion source 5.
[0025]
At the same time, the magnetic lines of force from the source magnet 6 pass through the electrode body 14 of the extraction electrode 9 toward the mounting plate 15 that is a magnetic body and pass through the slit 14a. The magnetic field does not penetrate into the slit 14a, which is a passage, and the passage of the ion beam IB is avoided. Thus, since the magnetic field of the source magnet 6 is shielded in the path of the ion beam IB, when the ion beam IB is extracted by the extraction electrode 9, the ion beam IB greatly reduces the influence of the magnetic field from the source magnet 6. The ion beam IB is extracted in a substantially desired direction.
[0026]
Further, even when the acceleration voltage applied to the extraction electrode system 7 is low, the extraction electric field can be increased by narrowing the source gap, so that ions can be efficiently extracted from the ion source 5 and at the same time the magnetic field of the source magnet 6 at the extraction electrode 9. Since the magnetic field lines penetrating into the slit 14a, which is the path of the ion beam IB, can be reduced, the ion beam IB can be efficiently drawn out in a desired direction, and the wafer can be efficiently irradiated with ions.
[0027]
Here, the ion implantation apparatus having the extraction electrode system according to the present invention will be described in detail with reference to FIGS.
In FIG. 2, the ion beam generator 2 has a source chamber (ion beam generating chamber) 3, and the inside of the source chamber 3 is depressurized to a predetermined degree of vacuum by a turbo molecular pump 4. An ion source 5 is accommodated in the source chamber 3. The ion source 5 discharges a doping gas sent from a gas supply source (not shown) to create a plasma state and ionizes a desired element (molecule). Around the ion source 5, a source magnet 6 for increasing the plasma density and promoting ionization is disposed.
[0028]
On the front side of the ion source 5, an extraction electrode system 7 for extracting ions generated by the ion source 5 is arranged. As shown in FIGS. 2 and 6, the extraction electrode system 7 has two sets of extraction electrodes 8 and 9 that face each other. Here, the extraction electrode 8 is a main electrode, and the extraction electrode 9 is a ground electrode.
[0029]
The main electrode 8 has an electrode body 12 having a slit 12a for allowing the ion beam IB to pass through, and a disk-shaped mounting plate 13 configured to surround the electrode body 12.
The electrode body 12 and the mounting plate 13 are made of a material having a small relative magnetic permeability, and a material having high purity and heat resistance, for example, a non-magnetic material such as graphite, carbon, or tungsten is preferably used. Only the mounting plate 13 may be made of a material having a small relative magnetic permeability.
[0030]
The ground electrode 9 also has an electrode body 14 having a slit 14 a for allowing the ion beam IB to pass through, and a disk-shaped mounting plate 15 configured to surround the electrode body 14.
The material of the electrode body 14 can be the same non-magnetic material such as graphite as the electrode body 12, while the mounting plate 15 is a magnetic material having a large relative permeability (for example, a relative permeability of 10). ² -10 ⁵ Degree). As the magnetic material, a material having high corrosivity is preferable. For example, it is desirable to use a magnetic stainless steel or an iron surface with a corrosion-resistant coating.
The extraction electrodes 8 and 9 may be movable or fixed, but it is preferable that the positions can be set independently.
[0031]
The slits 12a and 14a of the extraction electrodes 8 and 9 may have the same diameter or different diameters, and may be determined according to ion implantation conditions and the like. In addition, two or more slits having different diameters may be provided in each of the electrode bodies 12 and 14, and the extraction position of the ion beam IB may be switched.
[0032]
As described above, the extraction electrode on the side closest to the ion source is made of a material having a low relative magnetic permeability, and the mounting plate for the other extraction electrode is made of a magnetic material having a high relative magnetic permeability. When the ion beam is extracted by the extraction electrode system while reducing the influence on the magnetic field in the ion source even if it is close to the ion source, the extraction electric field can be raised and the ion beam can be extracted efficiently. Since it becomes difficult to be influenced by the magnetic field, the ion beam is drawn out in a desired direction. For this reason, it becomes difficult for the ion beam to hit the electrode material or the protective member, and accordingly, the life of the member is extended, the particle contamination is reduced, the life of the vacuum pump is extended, and the like.
In addition, it is desirable to increase the magnetic force of the source magnet as necessary when the magnetic field in the ion source is affected and the magnetic force is reduced by using a material having a high relative magnetic permeability.
[0033]
In the extraction electrode system 7 having such a structure, when a desired voltage is applied between the ion source 5 and the extraction electrode (main electrode) 8, ions are extracted and accelerated to form an ion beam IB. For example, when a voltage of +60 kV is applied to the ion source 5 and a voltage of −5 kV is applied to the main electrode 8 (the ground electrode 9 is 0 kV), an ion beam IB having an energy of 60 keV is extracted.
[0034]
As described above, the ion beam IB generated by the ion beam generator 2 is sent to the ion implanter 19 via the mass analyzer 17 and the mass resolving unit 18 as shown in FIG. In the part 19, ion implantation is performed on the silicon wafer W.
[0035]
Here, the mass analyzer 17 has an analysis magnet, and extracts only a desired ion species from the ion beam IB by adjusting the strength of the magnetic field. The mass resolving unit 18 includes a plurality of plates 20 having a slit for passing the ion beam IB and a shutter 21, and allows only a necessary ion beam among the ion beams IB from the mass analyzing unit 17 to pass therethrough.
The mass analyzing unit 17 and the mass resolving unit 18 are surrounded by a housing or a tube, and the inside thereof is depressurized to a predetermined degree of vacuum by a turbo molecular pump 22.
[0036]
The ion implantation part 19 has a target chamber 23, and the inside of the target chamber 23 is depressurized to a predetermined degree of vacuum by a cryopump 24. A wafer support 25 for supporting the wafer W to be ion-implanted is disposed in the target chamber 23.
The wafer support base 25 has a main body portion 26 that is rotatably and swingably provided. A plurality of arms 27 are provided radially on the main body portion 26, and a wafer W is provided at the tip of each arm 27. A wafer holder 28 is provided for holding the wafer. Further, a plasma shower 29 is installed in the target chamber 23, and the plasma shower 29 prevents the wafer W from being charged up when the ion beam IB is incident on the wafer W.
[0037]
A Faraday box 30 is connected to the target chamber 23, and a beam stop 31 for receiving the ion beam IB is disposed in the Faraday box 30. The beam stop 31 has an ion detector (not shown) that measures the irradiation amount of the ion beam IB as a beam current value.
[0038]
When ion implantation is performed by the ion implantation apparatus 1 configured as described above, a desired voltage is applied between the ion source 5 and the extraction electrodes 8 and 9 with the shutter 21 of the mass resolving unit 18 closed. An ion beam IB is generated. Then, the wafer W is mounted on each wafer holder 28 of the wafer support 25 by a wafer transfer robot (not shown). Thereafter, the shutter 21 of the mass resolving unit 18 is opened to pass the ion beam IB, and a motor (not shown) is driven to rotate and swing the wafer support 25. Thereby, ion implantation is performed by irradiating each wafer W with the ion beam IB.
[0039]
In addition, although it does not specifically limit regarding the ion produced | generated from an ion source, If the extraction electrode system of this invention is applied with respect to the ion source which produces | generates the hydrogen ion which is a light element, especially a hydrogen ion will be efficiently injected into a board | substrate. Can do. When performing hydrogen ion implantation using a conventional extraction electrode system, the traveling direction of the hydrogen ion beam was easily shifted. However, in the extraction electrode system of the present invention, when the ion beam is extracted, it is almost affected by the magnetic field of the source magnet. The hydrogen ion beam is extracted in a desired direction.
[0040]
In the above embodiment, the electrode body 14 of the ground electrode 9 is formed of a non-magnetic material such as graphite. However, it may be formed of a magnetic material having a high relative permeability. If the electrode body 14 and the like are made of a magnetic material in this way, the influence of the magnetic field of the source magnet 6 on the ion beam can be further reduced.
In addition, when the electrode body and the mounting plate are made of the same material, the same material can be integrally formed to reduce the size and weight of the extraction electrode.
[0041]
In addition, when using a material that may cause metal contamination, such as stainless steel, as the magnetic material, the surface of each part of the extraction electrode system can be coated in accordance with the material of the target wafer W. . For example, when the wafer W is silicon, the surface of the extraction electrode system can be coated with silicon, SiC, or the like. Thereby, metal contamination to the wafer W can be prevented.
[0042]
Furthermore, the shape of each extraction electrode may be freely changed according to the purpose, the arrangement location, and the like. This makes it possible to reduce the weight of the extraction electrode for easy handling, or to install the extraction electrode in a place where it is difficult to attach or a place where the attachment strength is weak, such as an ion source.
In addition, by reducing the size of the mounting plate made of a magnetic material having a high relative permeability, the effect on the magnetic field in the ion source is reduced in the same manner as when a material with a low relative permeability is used. Can be pulled out.
[0043]
In the above embodiment, the extraction electrode system including two sets of extraction electrodes has been described. However, the present invention can also be applied to three or more sets of extraction electrode systems. Also in this case, the extraction electrode mounting plate closest to the ion source is made of a material having a small relative permeability, and among the other extraction electrodes, at least one set of the extraction electrode mounting plate is a magnetic body having a large relative permeability. What should I do? As an example, in addition to the main electrode and the ground electrode as described above, another extraction electrode (intermediate electrode) is installed between the extraction electrode (main electrode) and the ion source, that is, three sets of extraction electrodes are provided. The extraction electrode system will be described with reference to FIGS.
[0044]
In these embodiments, the extraction electrode 32 is installed so as to be closest to the ion source 5. In this extraction electrode 32, in order not to affect the magnetic field lines in the ion source 5, the electrode body and the mounting plate are integrally formed of graphite which is a non-magnetic material. For this reason, the extraction electrode 32 can be brought close to the ion source 5 to increase the extraction electric field for extracting ions.
[0045]
The extraction electrode 32 may be movable or fixed, and may be installed in the chamber, the ion source 5 or the like, but the position can be set independently of other extraction electrodes. preferable.
If the voltage of the extraction electrode 32 can be set arbitrarily, the extraction electric field can be brought into an optimum state by adjusting the voltage. Therefore, it is not necessary to bring the magnetic extraction electrode close to the ion source 5 in order to increase the extraction electric field.
[0046]
In this case, with respect to the mounting plates 13 and 15 of the extraction electrodes 8 and 9, as shown in FIG. 10, the magnetic lines of force emitted from the source magnet 6 can be effectively obtained by using two magnetic stainless steels having a large relative permeability. The magnetic lines of force penetrating into the slits 12a and 14a, which are passages of the ion beam IB, can be reduced. Further, only one of them can be made of magnetic stainless steel as shown in FIG.
[0047]
If the extraction electrode 32 can be set to any voltage or position independently as described above, an extraction electric field that can extract ions most efficiently is set regardless of the magnitude of the acceleration voltage. At the same time, it is not necessary to bring a magnetic extraction electrode having a high relative permeability close to the ion source 5, and ions can be stably extracted from the ion source 5. Further, the magnetic field of the source magnet 6 is shielded by the extraction electrodes 8 and 9, and the magnetic lines of force penetrating the slit 14a that is the path of the ion beam IB can be reduced. Can be efficiently irradiated with ions.
[0048]
In the present embodiment, the extraction electrode closest to the ion source is described as being made of nonmagnetic graphite as a material having a small relative magnetic permeability. However, if the relative permeability of the extraction electrode closest to the ion source is smaller than the relative permeability of other extraction electrodes and the influence on the magnetic field in the ion source is small, the extraction electrode closest to the ion source may be a magnetic body. .
[0049]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to these.
(Examples and Comparative Examples)
[Source gap dependency test]
Using the ion implantation apparatus as shown in FIG. 1, when the extraction electrode system 7 is made of stainless steel having magnetism with a large relative permeability as the material of the mounting plates 13 and 15 of the extraction electrodes 8 and 9 (comparative example), Source gap and beam in the case where the mounting plate 13 of the extraction electrode 8 is made of graphite having a lower relative permeability than magnetic stainless steel and the mounting plate 15 of the extraction electrode 9 is made of stainless steel having a high relative permeability and magnetic properties (Example). The relationship between the current values (FIG. 8) and the relationship between the source gap and the magnetic force in the ion source (FIG. 7) were examined.
[0050]
7 is a graph when the material of the mounting plates 13 and 15 of the extraction electrodes 8 and 9 is made of magnetic stainless steel (comparative example), and the circle of FIG. 7 indicates that the mounting plate 13 of the extraction electrode 8 is graphite. The graph when the attachment plate 15 of the extraction electrode 9 is made of magnetic stainless steel (Example) is shown. These magnetic forces were measured by installing a Gauss meter probe (not shown) at the position of the ion source with the ion source removed.
[0051]
As the distance between the source gaps was narrow and the ion source and the extraction electrodes 8 and 9 were closer, the magnetic force of the ion source tended to decrease. In particular, when only the mounting plate 13 is made of graphite having a small relative permeability as compared with the case where stainless steel having a high relative permeability is used for the mounting plates 13 and 15, the overall magnetic force in the ion source is reduced. There was a tendency for the decrease to be suppressed.
[0052]
8 is a graph when the material of the mounting plates 13 and 15 of the extraction electrodes 8 and 9 is made of magnetic stainless steel (comparative example), and ○ is that the mounting plate 13 of the extraction electrode 8 is graphite, and the extraction electrode 9 shows a graph when the mounting plate 15 is made of magnetic stainless steel (Example). These beam current values are obtained by measuring with an ion detector (not shown) provided in the beam stop 31. At this time, the acceleration voltage was 80 kV, the arc voltage of the ion source 5 was 90 V, and the arc current was 8366 mA.
[0053]
In the case where both the mounting plates 13 and 15 are stainless steel having magnetism with a large relative permeability, if the source gap is 30 mm or less, the plasma of the ion source 5 becomes unstable and the ion beam IB is not obtained. This is because, as shown in FIG. 7, the magnetic force in the ion source is lowered due to the influence of a magnetic material having a large relative permeability. On the other hand, when the mounting plate 13 close to the ion source 5 is made of graphite and the far mounting plate 15 is made of stainless steel having magnetism with a large relative permeability, the source gap is stable from 15 mm to 45 mm at which the apparatus can operate. Thus, an ion beam is obtained.
[0054]
[Acceleration voltage dependence test]
Next, the relationship between the acceleration voltage and the beam current value when the two extraction electrode systems were used was examined. FIG. 9 is a diagram showing the results. These beam current values were obtained by measuring in the same manner as described above using an ion detector. At this time, the arc voltage of the ion source 5 was 90 V, and the arc current was 8366 mA.
[0055]
When the mounting plates 13 and 15 are both magnetic stainless steel (comparative example) and the source gap is 32 mm, the beam current value is about 25 mA when the acceleration voltage is 80 kV, and the beam current value when the acceleration voltage is 40 kV. Although the current was about 16 mA, when the source gap was 30 mm or less, the magnetic force in the ion source decreased to 200 Gauss or less, and the beam current could not be obtained stably.
[0056]
On the other hand, when the mounting plate 13 is made of graphite and the mounting plate 15 of the extraction electrode 9 is made of magnetic stainless steel (Example), the magnetic force in the ion source can be 200 Gauss or more even if the source gap is brought close to the ion source. Therefore, a beam current value can be stably obtained even when the source gap is 30 mm or less. Therefore, by setting the source gap to 22 mm, a beam current value of about 27 mA is obtained when the acceleration voltage is 80 kV, and about 18 mA is obtained when the acceleration voltage is 40 kV, and the mounting plates 13 and 15 are made of stainless steel having magnetism. The beam current value could be improved by about 10% compared with the above.
[0057]
As can be seen from the above results, the extraction electrode mounting plate closest to the ion source is made of a material having a low relative permeability (such as graphite), and the other extraction electrode mounting plate is a magnetic material having a high relative permeability. By using an extraction electrode system made of (such as stainless steel having magnetism), a stable ion beam IB can be obtained even if the source gap is reduced, and a relatively high beam current value can be obtained even when the acceleration voltage is reduced. As a result, ion implantation can be performed efficiently.
[0058]
In addition, this invention is not limited to the said embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0059]
For example, the present invention is not limited to hydrogen ion implantation, but can be applied to ion implantation of B, P, As, and the like.
In the above-described embodiment, the scanning of the ion beam IB is performed by the rotation / oscillation operation of the wafer support. However, the present invention is not limited to this, and an ion implantation apparatus of a type that moves the ion beam itself. The present invention can also be applied.
[0060]
【The invention's effect】
According to the present invention, among the extraction electrode system composed of two or more extraction electrodes, the extraction electrode mounting plate that is at least closest to the ion source is made of a material having a low relative permeability, and the remaining Of the extraction electrodes, at least one set of extraction electrode mounting plates is made of a material having a relative permeability larger than that of the former, thereby minimizing the influence on the magnetic field in the ion source and at the same time narrowing the source gap, The ion extraction electric field can be increased, and the ion beam can be extracted in a desired direction with almost no influence of the magnetic field of the source magnet. Therefore, even if the acceleration voltage is lowered, the ion extraction electric field can be increased by narrowing the gap of the source gap, and the loss of the ion beam by the source magnet can be suppressed. improves.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram (top view) showing an example of an ion implantation apparatus.
FIG. 2 is an enlarged view of the ion beam generator shown in FIG.
FIGS. 3A and 3B are diagrams showing a path of magnetic lines of force emitted from a source magnet when the extraction electrode mounting plate is made of a non-magnetic material, FIG. 3A is a top view, and FIG. 3B is a front view of a mounting plate portion; .
FIGS. 4A and 4B are diagrams showing paths of magnetic lines of force emitted from a source magnet when the extraction electrode mounting plate is made of a magnetic material, FIG. 4A is a top view, and FIG. 4B is a front view of the mounting plate portion;
5 is a diagram showing a path of magnetic lines of force emitted from a source magnet when the extraction electrode of FIG. 4 is brought close to an ion source.
FIG. 6 is a diagram showing a path of lines of magnetic force emitted from a source magnet when an extraction electrode system according to the present invention configured from two sets of extraction electrodes is used.
FIG. 7 is a graph showing the relationship between the source gap and the magnetic force in the ion source.
FIG. 8 is a diagram showing a relationship between a source gap and a beam current value when the extraction electrode systems of Examples and Comparative Examples are used.
FIG. 9 is a diagram showing the relationship between the acceleration voltage and the beam current value when the extraction electrode systems of Examples and Comparative Examples are used.
FIG. 10 is a diagram showing a path of lines of magnetic force emitted from a source magnet when the extraction electrode system according to the present invention configured from three sets of extraction electrodes is used.
FIG. 11 is a diagram showing a path of lines of magnetic force emitted from a source magnet when another extraction electrode system according to the present invention configured from three sets of extraction electrodes is used.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Ion implantation apparatus, 2 ... Ion beam generation part, 3 ... Source chamber (chamber for ion beam generation), 5 ... Ion source, 6 ... Source magnet, 7 ... Extraction electrode system, 8 ... Extraction electrode (main electrode), DESCRIPTION OF SYMBOLS 9 ... Extraction electrode (ground electrode) 12 ... Electrode body, 12a ... Slit, 13 ... Mounting plate, 14 ... Electrode body, 14a ... Slit, 15 ... Mounting plate, 19 ... Ion implantation part, 32 ... Extraction electrode (intermediate electrode) IB, ion beam, W ... wafer.

Claims (10)

Two or more sets of ions that are provided in an ion beam generating chamber of an ion implanter and that generate ions generated by an ion source to which a magnetic field of a source magnet is applied are extracted in a direction perpendicular to the magnetic field . An extraction electrode system including an extraction electrode, wherein the extraction electrode has an electrode body and a mounting plate, and the relative permeability of the mounting plate of the extraction electrode that is at least closest to the ion source is at least one other An extraction electrode system for an ion implantation apparatus, wherein the extraction electrode system is smaller than the relative permeability of a set of extraction electrode mounting plates.   2. The extraction electrode system for an ion implantation apparatus according to claim 1, wherein the extraction electrode mounting plate closest to the ion source is made of a non-magnetic material.   The extraction electrode system of the ion implantation apparatus according to claim 1 or 2, wherein the extraction electrode mounting plate other than the extraction electrode located closest to the ion source is made of a magnetic material.   The extraction electrode system of the ion implantation apparatus according to any one of claims 1 to 3, wherein the nonmagnetic material is graphite, carbon, or tungsten.   The ion implantation apparatus according to any one of claims 1 to 4, wherein the magnetic body is a stainless steel having magnetism or a surface of iron having a corrosion-resistant coating. Extraction electrode system.   The extraction electrode system of the ion implantation apparatus according to any one of claims 1 to 5, wherein an electrode body and a mounting plate of the extraction electrode are integrally formed.   The extraction electrode system of the ion implantation apparatus according to any one of claims 1 to 6, wherein the extraction electrode located closest to the ion source can arbitrarily set a voltage.   The ion implantation according to any one of claims 1 to 7, wherein the extraction electrode that is closest to the ion source is capable of setting a position independently of other extraction electrodes. The extraction electrode system of the device.   The extraction electrode system of an ion implantation apparatus according to any one of claims 1 to 8, wherein the extraction electrode system extracts hydrogen ions generated by an ion source.   An ion implantation apparatus comprising at least the extraction electrode system according to any one of claims 1 to 9.

Images