JP2006331691A - Ion irradiation device and ion irradiation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion irradiation device capable of reducing a spot diameter of an ion beam emitted to an object without causing the difficulties such as density deterioration of the ion beam and enlargement of a device size, and an ion irradiation method. <P>SOLUTION: The ion beam 8 is generated by accelerating ions supplied from an ion source. A divergence angle θ1 is reduced to a divergence angle θ0 by accelerating the traveling of the ion beam 8 with an accelerator. By this, a distance L1 is virtually made longer between an ion outlet from which the ion beam 8 is emitted, and a convergent lens 6, and the spot diameter of the ion beam when emitted to a sample is reduced in reverse proportional to L1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ion irradiation apparatus and an ion irradiation method for irradiating ions emitted from an ion source, and more particularly to an ion irradiation apparatus and an ion irradiation method capable of reducing an irradiation spot diameter.

Conventionally, when a sample is subjected to microfabrication, ions emitted from an ion source are turned into an ion beam and irradiated onto the sample. A characteristic change occurs in the portion irradiated with the ion beam in the sample, and uses such as melting in a special solvent are known. In this case, the sample can be processed into a target shape by irradiating each part of the sample with the ion beam in accordance with a target processed shape.
Here, when performing fine processing on the sample, it is desirable that the spot diameter of the ion beam irradiated on the sample is small. In other words, the smaller the spot diameter, the smaller the scale can be processed. Therefore, a technique for irradiating the sample while reducing the diameter of the ion beam using a converging lens is disclosed in, for example, Patent Document 1 and the like.

FIG. 1 is a schematic configuration diagram of an ion irradiation apparatus in a conventional example in which the technique disclosed in Patent Document 1 is used. Hereinafter, an ion irradiation apparatus in a conventional example will be described with reference to FIG.
As shown in FIG. 1, an ion irradiation apparatus B in the conventional example is roughly constituted by an ion source 1, an accelerator 2, an accelerator power source 3, a control device 4, an aperture 5, a focusing lens 6, and the like, and is installed at a predetermined installation location. An installed sample 7 (an example of a predetermined object) is irradiated with ions.
In the ion source 1, ions such as monovalent helium ions are generated. The ion source 1 is integral with a drawing aperture 1a provided with an ion outlet as an opening. The ion source 1 supplies the ions from the ion outlet to the acceleration tube of the accelerator 2. The accelerator tube in the accelerator 2 is applied with a voltage V0 such as 400 kV by the accelerator power supply 3. As a result, an electric field is generated toward the sample 7 (that is, along the path of the ions), and ions supplied from the ion source 1 are accelerated in the acceleration tube and irradiated onto the sample 7. . The voltage V0 from the accelerator power supply 3 is controlled by the control device 4.

Ions (ion beam 8) accelerated by the accelerator 2 pass through the aperture 5 having an opening on the axis of the ion beam 8. The ion beam 8 that has passed through the aperture 5 travels while increasing its diameter. A plurality of converging lenses 6 are installed in the traveling direction of the ion beam 8. The converging lens 6 is made of an electromagnet and constitutes a quadrupole electromagnet lens. Thereby, the converging lens 6 changes the traveling direction of each ion of the ion beam 8 to reduce the diameter of the ion beam 8. The ion beam 8 whose diameter has been reduced by the converging lens 6 is the sample placed near the focal point (the point at which the density of the ion beam 8 converged by the converging lens 6 is maximized). 7 is irradiated.
The energy of each ion in the ion beam 8 can be controlled by the voltage V0 applied by the accelerator power supply 3, and the depth of fine processing applied to the sample 7 is adjusted by controlling the energy. It is possible.
Japanese Patent Laid-Open No. 03-074037

The diameter (spot diameter) of the ion beam 8 when the sample 7 is irradiated is determined as follows. That is, the distance from the aperture 5 to the converging lens 6 on the axis of the ion beam 8, in other words, the distance that the ion beam 8 travels while increasing its diameter is L1. Further, the distance from the focusing lens 6 to the sample 7 on the axis of the ion beam 8, in other words, the distance that the ion beam 8 travels while being converged by the focusing lens 6 is L2. Further, when the diameter of the opening provided in the aperture 5 is r1, the spot diameter r2 when the ion beam 8 is irradiated onto the sample 7 is substantially proportional to r1 and L2 and substantially inversely proportional to L1. , And have the relationship shown in the following formula (1).
r2∝r1 × L2 / L1 (1)
From formula (1), in order to reduce the spot diameter r2 of the ion beam 8, methods such as decreasing r1, decreasing L2, increasing L1 can be considered. However, if r2 is reduced, the number of ions passing through the aperture 5 is reduced, and the density of the ion beam 8 is reduced. Further, it is usually necessary to arrange a detector such as scattered ions scattered by the sample 7 between the focusing lens 6 and the sample 7, that is, it is difficult to reduce L2. Further, when L1 is increased, the entire apparatus becomes larger.
As described above, in the conventional example, it is difficult to reduce the spot diameter of the ion beam 8, and therefore there is a limit to the scale of fine processing.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a spot of an ion beam that is irradiated onto an object without difficulty such as a reduction in the density of the ion beam and an increase in the apparatus size. An object of the present invention is to provide an ion irradiation apparatus and an ion irradiation method capable of reducing the diameter.

In order to achieve the above object, the present invention is an ion irradiation apparatus for irradiating a predetermined object (sample) with ions, and a first electric field in the vicinity of an ion outlet (opening) in an ion source filled with ions. To extract ions from the ion source, generate a second electric field along a path of the extracted ions, accelerate the progress of the ions, and focus the accelerated ions on the sample. Irradiation is performed as an ion irradiation apparatus for irradiation.
The ion beam by the ions is generated by the ions being accelerated by the first electric field after passing through the ion outlet. The ion beam generated in this way and whose diameter is enlarged (that is, each ion diffusing from the axis of the ion beam) is accelerated by the second electric field, which will be described in detail later with reference to FIG. It is possible to obtain the same effect as increasing L1 (distance between the aperture 5 and the converging lens 6) described in the conventional example, and thereby the spot diameter when the sample is irradiated with the ion beam. Is reduced.

Here, as will be described in detail later, the energy of the ions and the spot diameter can be adjusted via the first electric field and the second electric field. Specifically, by adjusting the voltage ratio (predetermined setting ratio) when generating the first electric field and the second electric field while maintaining a constant value, only the energy is maintained while maintaining the spot diameter. Can be adjusted.
Furthermore, it is preferable that a first aperture for limiting a passage range of the ions is provided between the generation region of the first electric field and the generation region of the second electric field. The diameter expansion is started after passing through the first aperture. By installing the first aperture, the ion beam diameter expansion start point and the diameter at that point become clear, and the adjustment of the spot diameter becomes highly accurate and easy.
Further, in order to limit the passage range of the ions before being incident on the focusing lens, it is conceivable to install a second aperture in a region between the generation region of the second electric field and the focusing lens. The second aperture only blocks ions that are far away from the axis of the ion beam, and the diameter of the aperture does not change the degree of change in diameter (that is, the divergence angle) after the ion beam passes. It is necessary to provide a wide enough range (not to cause diffraction) and to minimize the decrease in the beam current due to the interruption of ions (to prevent the beam current from changing as much as possible).
Furthermore, the present invention may be understood as an ion irradiation method for irradiating an object with ions.

  According to the present invention, it is possible to reduce the spot diameter of the ion beam irradiated on the object without difficulty such as a decrease in the density of the ion beam and an increase in the size of the apparatus. It can be applied to an object.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
1 is a schematic configuration diagram of an ion irradiation apparatus in a conventional example, FIG. 2 is a schematic configuration diagram of an ion irradiation apparatus in an embodiment of the present invention, and FIG. 3 is irradiated by the ion irradiation apparatus in the embodiment of the present invention. FIG. 4 is a conceptual diagram illustrating the trajectory of ions, FIG. 4 is a table showing the correspondence between the voltage V0, the voltage V1, and the reduction rate of the ion beam, and FIG. 5 is a schematic configuration diagram of the ion irradiation apparatus according to the embodiment of the present invention. . In addition, the same code | symbol shall be attached | subjected about the structure similar to a prior art example.

(1) About schematic structure of the ion irradiation apparatus which concerns on embodiment of this invention.
Hereinafter, an ion irradiation apparatus according to an embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, an ion irradiation apparatus A1 according to an embodiment of the present invention includes an ion source 1, an extraction electrode 9, an extraction power supply 11, an accelerator 2, an accelerator power supply 3, a control apparatus 4, a converging lens 6, and the like. Is an apparatus that irradiates ions to a sample 7 (an example of a predetermined object) installed at an installation location near the focal point of the convergent lens 6.
The ion source 1 is filled with ions such as monovalent helium ions. The ion source 1 is integral with a drawing aperture 1a provided with an ion outlet as an opening. The ion source 1 supplies the ions from the ion outlet to a space 10 formed between the extraction aperture 1 a and the extraction electrode 9. A voltage V1 is applied to the space 10 by the power supply 11 for extraction, thereby forming a first electric field. The extraction aperture 1a, the extraction electrode 9, and the extraction power supply 11 are an example of a first electric field generating means. The extraction electrode 9 is provided with an aperture opening, and the ion passing range is limited by the size of the aperture opening. The extraction electrode 9 is an example of a first aperture. By providing the first aperture, the generation point of the ion beam and the diameter of the ion beam at the point become clear, and adjustment of the spot diameter when the sample 7 is irradiated becomes easy (first Even if the aperture is not reduced by the aperture, it is considered that an ion beam diffusing with the vicinity of the ion exit as a generation point can be obtained, but the generation point and the diameter at the point become unclear).

In the space 10, the ions are extracted from the ion source 1 and accelerated by the first electric field (the electric field generated by the first electric field generating means), and the ions passing through the extraction electrode 9 are accelerated and extracted as an ion beam. (An example of an ion extraction process). The ion beam passes through the aperture opening provided in the extraction electrode 9 and is incident on an acceleration tube of the accelerator 2 while expanding its diameter (the accelerator 2 has a second electric field as described later). It is an example of the generation means, and it can be understood that the extraction electrode 9 is provided between the first electric field generation means and the second electric field generation means). A voltage V0 is applied to the accelerator 2 by the accelerator power supply 3, whereby the accelerator tube has a second direction in the direction along the axis of the ion beam 8 (direction along the path of the ions). An electric field is generated. Each of the ions of the ion beam 8 is accelerated in the direction along the axis of the ion beam 8 by the second electric field (an example of an ion acceleration step). The accelerator 2 and the accelerator power supply 3 are an example of second electric field generating means.
The voltage V0 from the accelerator power supply 3 and the voltage V1 from the lead-out power supply 11 are controlled by the control device 4.
A plurality of converging lenses 6 are installed in the traveling direction of the ion beam 8 (direction along the axis). The converging lens 6 is made of an electromagnet and constitutes a quadrupole electromagnet lens. That is, each of the converging lenses 6 generates a magnetic field in the passage region of the ion beam 8 and changes the traveling direction of each ion of the ion beam 8 to reduce the diameter of the ion beam 8 (that is, Converge). The ion beam 8 whose diameter has been reduced by the focusing lens 6 (an example of ion focusing means) is applied to the sample 7 placed in the vicinity of the focal point (an example of an ion focusing irradiation process).

(2) About ion trajectory and ion beam spot diameter.
With this configuration, the ion irradiation apparatus can reduce the diameter of the ion beam 8 at the focal point of the focusing lens 6 (the diameter when the sample 7 is irradiated, that is, the spot diameter). It is. FIG. 3 is a diagram showing the trajectory of ions irradiated by the ion irradiation apparatus. The reason why a small spot diameter can be obtained will be described below with reference to FIG.
The ion beam 8 composed of each of the ions accelerated by the first electric field travels at a velocity v1 in the traveling direction along the axis of the ion beam while its divergence angle is θ1 and the diameter is expanded. Further, after entering the accelerator tube of the accelerator 2, each of the ions is accelerated by the second electric field in the traveling direction along the axis of the ion beam 8 to v0. Further, since there is no change in the velocity component of each of the ions in the direction orthogonal to the traveling direction (hereinafter referred to as the orthogonal direction), the divergence angle of the ion beam 8 becomes θ0 (<θ1) after passing through the accelerator tube. Pressed.
Therefore, as shown in FIG. 3, the ion beam 8 is not actually irradiated from the actual aperture opening, but is a virtual opening positioned upstream in the traveling direction from the actual aperture opening. It seems to be more irradiated.
As described above, the traveling distance L1 (see FIG. 1) when the ion beam 8 after passing through the aperture 5 (in the configuration of the present invention, the extraction electrode 9) travels while increasing its diameter increases. The spot diameter of the ion beam 8 is reduced (specifically, it is inversely proportional to L1). Therefore, in this case, the distance L1 ″ along the axial direction between the virtual aperture and the convergent lens 6 can be identified with the travel distance L1, and the actual aperture aperture and the convergent lens 6 can be identified. It is possible to obtain a small spot diameter of the ion beam 8 without increasing the distance L ′.

(3) Control of voltage V1 and voltage V0.
As described above, the spot diameter of the ion beam 8 is proportional to L2 / L1 ″. Hereinafter, L2 / L1 ″ is referred to as a reduction ratio M. Here, the divergence angles θ1 and θ0 are usually small, and the reduction ratio M (= L2 / L1 ″) can be approximated by √ (θ0 / θ1). Since it is accelerated only in the axial direction of the ion beam 8 and there is no speed change in the orthogonal direction, θ0 / θ1 matches the ratio v1 / v0 of the speed v0 after acceleration by the accelerator 2 and the speed v1 before acceleration. In addition, the speed ratio v1 / v0 is obtained by dividing the voltage applied to the space 10 (voltage by the power supply 11 for extraction) V0 and the voltage applied to the accelerator 2 (voltage by the power supply 3 for accelerator) V1. √ {V0 / (V0 + V1)} In addition, since the extraction power supply 11 and the accelerator power supply 3 are normally controlled to satisfy V0 << V1, √ {V0 / (V0 + V1) } ≒ √ (V0 It is possible to approximate as V1).
From the above, the spot diameter reduction rate M is determined by the ratio of the voltage V1 from the extraction power supply 11 and the voltage V0 from the accelerator power supply 3.

As described above, the depth of fine processing applied to the sample 7 can be adjusted by the energy applied to each of the ions. That is, as the ion with higher energy is irradiated, the characteristic change of the irradiated portion in the sample 7 occurs deeper.
The energy applied to each of the ions is proportional to the total value of the voltage V0 from the accelerator power supply 3 and the voltage V1 from the extraction power supply 11, and the control device 4 controls these voltages. To adjust the energy of each of the ions.
However, as described above, the reduction ratio M is determined by the ratio between the V0 and the V1, and if the V0 and V1 are controlled without considering this, the reduction simultaneously with the energy of the ions. The rate M changes, and the spot diameter of the ion beam 8 changes.
Therefore, when the control device 4 (an example of voltage control means) is determined in advance by, for example, inputting the spot diameter of the ion beam 8 (target irradiation spot diameter of the object) to the user's operation input, The ratio between V0 and V1 is calculated from the input spot diameter, and the value is used for the following voltage control as a set voltage ratio. That is, according to the target energy applied to each of the ions irradiated to the sample 7 (object), the V0 (voltage for generating an electric field in the second electric field generating means) and the V1 (first electric field generating). These values are adjusted while maintaining the ratio of the electric field generating voltage) in the means at the set voltage ratio. Thereby, it is possible to adjust only the ion energy without changing the size of the spot diameter.
On the contrary, when only the spot diameter is adjusted without changing the ion energy, only the ratio may be changed while maintaining the sum of V0 and V1 at a predetermined total value.

FIG. 4 shows a table in which the reduction ratio M is associated with V0 and V1. A quadrupole electromagnet lens formed by a plurality of the converging lenses 6 has an asymmetric focusing force in a plane perpendicular to the axis of the ion beam 8. The first axis orthogonal to the axis of the ion beam 8 is the x axis, and the second axis orthogonal to the axis of the ion beam 8 (the axis of the ion beam 8 and the axis orthogonal to the x axis) is the y axis. That's it. FIG. 4 shows both the reduction rate Mx in the x-axis direction and the reduction rate My in the y-axis direction.
(A) is a simulation result of the reduction ratios Mx and My when V1 = 5 kV and V0 = 1000 kV. (B) is a simulation result of the reduction ratios Mx and My when V1 = 10 kV and V0 = 1000 kV. (C) is a simulation result of the reduction ratios Mx and My when V1 = 2.5 kV and V0 = 500 kV. (D) is a simulation result of convergence rates Mx and My when V1 = 10 kV and V0 = 1000 kV in the configuration of the conventional example (passing through the aperture 5 after acceleration by the accelerator 2, that is, no change in the divergence angle by the accelerator 2) It is.
By comparing (d) with (a), (b), (c), it is understood that the reduction ratios Mx, My are greatly reduced by the configuration of the present invention, and a smaller spot diameter can be obtained. The From the comparison between (a) and (b), it is understood that the reduction ratios Mx and My change when the ratio between V0 and V1 is not maintained. On the other hand, it is understood from the comparison between (a) and (b) that the reduction ratios Mx and My do not change even if each is changed while maintaining the ratio between V0 and V1.

In addition to the configuration disclosed in the above-described embodiment, as shown in FIG. 5, the accelerator 2 (an example of the second electric field generating unit) in the irradiation path of the ion beam 8 to the focusing lens 6 (an example of the ion focusing unit). A configuration (an ion irradiation apparatus A2 according to an embodiment of the present invention) further including an aperture 12 that restricts the passage range of each ion of the ion beam 8 on the path toward () is conceivable.
It is assumed that ions that are greatly diverged from the axis of the ion beam 8 are difficult to be converged by the focusing lens 6. Therefore, the aperture 12 is used for the purpose of blocking ions largely separated from the axis of the ion beam 8. The diameter of the aperture of the aperture 12 is set to be considerably larger than the diameter of the aperture opening of the extraction electrode 9, so that the ion beam 8 changes in the divergence angle when passing through the aperture 12. (Diffraction) does not occur.

In the above-described embodiment, an example in which monovalent helium is used as the ion has been disclosed. However, the present invention is not limited to this, and an ion using another chemical species such as hydrogen ion (H ⁺ ) may be used. . Alternatively, the sample may be irradiated with charged particles such as protons and electrons.
Furthermore, although the above description has dealt with the microfabrication of the sample as an application target field of the present invention, it is not limited to this. For example, the present invention can be applied to the purpose of detecting scattered ions scattered by the sample and analyzing the sample based on the detection result.

The schematic block diagram of the ion irradiation apparatus in a prior art example. The schematic block diagram of the ion irradiation apparatus in embodiment of this invention. The conceptual diagram explaining the track | orbit of the ion irradiated with the ion irradiation apparatus in embodiment of this invention. The table | surface showing the correspondence of the voltage V0, the voltage V1, and the reduction rate of an ion beam. The schematic block diagram of the ion irradiation apparatus which concerns on the Example of this invention.

Explanation of symbols

A1 ... Ion irradiation apparatus A2 according to an embodiment of the present invention ... Ion irradiation apparatus B according to an example of the present invention ... Ion irradiation apparatus 1 in conventional example ... Ion source 1a ... Drawer aperture 2 ... Accelerator 3 ... Accelerator power supply 4 ... Control device 5 ... Aperture 6 ... Converging lens 7 ... Sample (object)
8 ... Ion beam 9 ... Extraction electrode 10 ... Space 11 ... Extraction power supply 12 ... Aperture

Claims (6)

An ion irradiation apparatus for irradiating ions on a predetermined object,
First electric field generating means for generating an electric field in the vicinity of an ion outlet in an ion source for generating ions and extracting ions from the ion source;
Second electric field generating means for generating an electric field along the path of ions extracted from the ion source by the first electric field generating means and accelerating the progress of the ions;
Ion focusing means for converging ions accelerated by the second electric field generating means and irradiating the object;
An ion irradiation apparatus comprising:   Voltage control for adjusting each of the electric field generating voltages in the first electric field generating means and the second electric field generating means while maintaining a predetermined set voltage ratio according to the target energy of ions irradiated on the object. The ion irradiation apparatus according to claim 1, further comprising means.   The ion irradiation apparatus according to claim 1, wherein the set voltage ratio is determined by a target irradiation spot diameter of ions in the object.   The ion irradiation apparatus according to any one of claims 1 to 3, wherein a first aperture is provided between the first electric field generating unit and the second electric field generating unit to limit an ion passage range.   The ion irradiation apparatus according to any one of claims 1 to 4, further comprising a second aperture that limits a passage range of ions from the second electric field generating unit toward the ion converging unit. A method of irradiating ions to a predetermined object,
An ion extraction step of generating a first electric field in the vicinity of an ion outlet in the ion source for generating ions, and extracting the ions from the ion source by the first electric field;
An ion acceleration step of generating a second electric field along a path of ions extracted from the ion source by the ion extraction step, and accelerating the progression of the ions by the second electric field;
An ion focused irradiation step of focusing the ions accelerated by the ion acceleration step and irradiating the target object;
An ion irradiation method comprising:

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