Ion source and ion gun

Abstract

This ion source 1 comprises: a resonance section 8 having an ion extraction port 9 for extracting ions I; an internal conductor 13 for forming a constriction section 16, which corresponds to an electric field concentration region P, between the internal conductor 13 and the ion extraction port 9 in the resonance section 8; an electromagnetic wave introduction section 14 for introducing an electromagnetic wave F that resonates in the resonance section 8; and a gas introduction section 15 for introducing a gas G, which is the source of the ions I, into the constriction section 16.

Description

Ion Sources and Ion Guns

[0001] The present disclosure relates to ion sources and ion guns.

[0002] A focused ion beam (FIB) device scans a very finely focused ion beam over the surface of a sample. This device is used for processing samples and observing the cross-sectional structure of samples based on secondary electrons generated by ion beam irradiation.

[0003] An example of an ion source that can be mounted in a focused ion beam device is a microwave ion source described in Patent Document 1. This conventional microwave ion source includes a discharge chamber in which plasma of a predetermined gas is generated by a magnetic field and microwaves, an antenna that forms part of the magnetic path of one magnetic pole of a magnetic field generating means and introduces microwaves into the discharge chamber, an extraction electrode that forms the magnetic path of the other magnetic pole of the magnetic field generating means and is arranged so that an extraction hole is located at the tip of the antenna, and an intermediate electrode that has an extraction port coaxial with the antenna and is arranged so that the cross-sectional area of ​​the discharge chamber between it and the antenna gradually decreases toward the extraction port.

[0004] Japanese Patent Application Publication No. 8-83586

[0005] In the ion source described above, electrons are vibrated by passing a high frequency wave through the antenna, and plasma is induced in the discharge chamber. However, in a configuration such as the microwave ion source described in Patent Document 1, plasma is generated over a wide area in the discharge chamber, so there is room for improvement in terms of increasing the brightness of the output ions.

[0006] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide an ion source that can output ions with high brightness, and an ion gun using the same.

[0007] The gist of the present disclosure is as follows.

[0008] [1] An ion source comprising: a resonator having an ion outlet for extracting ions; an internal conductor forming a narrowed portion in the resonator between the ion outlet and the resonator, the narrowed portion being an electric field concentration region; an electromagnetic wave introduction portion for introducing an electromagnetic wave that causes resonance in the resonator; and a gas introduction portion for introducing a gas that is a raw material for ions into the narrowed portion.

[0009] In this ion source, an electric field concentration region is formed by a narrowed portion of the internal conductor in the resonator, and the gas that serves as the source of ions is introduced into the narrowed portion, which serves as the electric field concentration region. This allows the area where the gas is ionized to be narrowed by the narrowed portion, making it possible to generate ions in a narrow area with high efficiency. Therefore, this ion source achieves high brightness for ions output from the ion outlet.

[0010] [2] The ion source according to [1], wherein the gas outlet of the gas inlet is arranged to face the narrowed portion. With this configuration, the raw material for ions can be supplied intensively to a narrow area where the gas is ionized. Therefore, the brightness of the ions output from the ion outlet can be further increased.

[0011] [3] The ion source according to [2], wherein the inner dimension of the gas outlet is 30 times or less the skin depth determined by the frequency of the electromagnetic wave and the angular frequency of the plasma generated in the resonator. With this configuration, it is possible to allow the electromagnetic wave to sufficiently penetrate into the gas, thereby effectively promoting the ionization of the gas.

[0012] [4] The ion source according to [2] or [3], wherein the gas outlet is provided with a nozzle having an inner dimension smaller than that of the ion outlet. In this case, the range in which the gas can exist in the constricted portion is physically limited, so that the raw material for ions can be supplied more intensively to a narrow area where the gas is ionized. Therefore, the brightness of the ions output from the ion outlet can be further increased.

[0013] [5] The ion source according to any one of [1] to [4], wherein the ion outlet has a shape that flares outward, and the internal conductor has a shape that is pointed toward the ion outlet. This configuration can further narrow the area where the gas is ionized. Therefore, the brightness of the ions output from the ion outlet can be further increased.

[0014] [6] The ion source according to any one of [1] to [5], wherein the resonator has an internal space. In this case, it is easy to arrange an internal conductor in the resonator.

[0015] [7] The ion source according to [6], wherein the resonator is configured by coupling an outer conductor having the ion outlet to a base conductor via an insulating member. In this case, the resonator can be easily configured. Since the outer conductor is electrically insulated from the base conductor, a voltage independent of the base conductor can be applied to the outer conductor. This allows ions to be suitably extracted from the ion outlet.

[0016] [8] The ion source according to [6] or [7], wherein the resonator has a choke structure. In this case, leakage of electromagnetic waves to the outside can be suppressed.

[0017] [9] The ion source according to any one of [1] to [5], wherein the resonator portion is made of a dielectric material. In this case, it is possible to reduce the resonator length of the resonator portion, thereby achieving miniaturization of the resonator portion.

[0018]

[10] The ion source according to [9], wherein the electromagnetic wave introducing section is configured by an antenna inserted in the dielectric body. In this case, the electromagnetic wave can be introduced with high efficiency into the resonator section configured by the dielectric body.

[0019]

[11] The ion source according to any one of [1] to

[10] , wherein an insulating enclosure member is disposed in the narrowed portion so as to surround the gas flow path. In this case, the range in which the gas can exist in the narrowed portion is physically limited, so that the raw material for ions can be supplied more intensively to a narrow area where the gas is ionized. Therefore, the brightness of the ions output from the ion outlet can be further increased.

[0020]

[12] An ion gun comprising: the ion source according to any one of [1] to

[11] ; an extraction electrode that extracts the ions from the ion source; and an optical system that guides the ions extracted by the extraction electrode toward a target object.

[0021] In this ion gun, by using the above-mentioned ion source, the area where the gas is ionized can be narrowed by the constriction portion, and ions can be generated in a narrow area with high efficiency. The high brightness of the ions output from the ion source enables processing of objects at high speed and with high precision.

[0022] According to the present disclosure, the brightness of output ions can be increased.

[0023] Fig. 1 is a perspective view showing the configuration of an ion source according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view of Fig. 1. Fig. 3 is an enlarged cross-sectional view of a main part of Fig. 1. Fig. 4 is a perspective view showing the configuration of an ion source according to a modified example. Fig. 5 is a perspective view showing the configuration of an ion source according to another modified example. Fig. 6 is a perspective view showing the configuration of an ion source according to yet another modified example. Fig. 7 is a schematic view showing the configuration of an ion gun according to an embodiment of the present disclosure.

[0024] Hereinafter, preferred embodiments of an ion source and an ion gun according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0025] FIG. 1 is a perspective view showing the configuration of an ion source according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view of FIG. 1. The ion source 1 shown in FIGS. 1 and 2 is a device mounted on, for example, a focused ion beam (FIB) device. The focused ion beam device scans an extremely finely focused ion beam over the surface of a sample. This device is used for processing samples and observing the cross-sectional structure of a sample based on secondary electrons generated by ion beam irradiation.

[0026] The ion source 1 of this embodiment is, for example, a Xe (xenon) ion source. In conventional focused ion beam devices, Ga (gallium) ion sources have been widely used from the viewpoint of microfabrication, but improving the processing speed and suppressing target contamination have been technical challenges. While Xe ion sources have emerged as devices that can overcome these challenges, increasing the brightness of output ions has been a technical challenge, and Xe ion sources have traditionally been considered difficult to use in microfabrication.

[0027] The ion source 1 of this embodiment forms an electric field concentration region P in the resonator 8 by utilizing the resonance of the electromagnetic wave F, and supplies the gas G to be ionized to the electric field concentration region P, thereby enabling high brightness of output ions and contributing to the realization of microfabrication in a focused ion beam apparatus using a Xe ion source. The detailed configuration of the ion source 1 will be described below.

[0028] 1 and 2, the ion source 1 includes a housing H made up of a base 2 that also serves as a base conductor K1 and a lid 3 that also serves as an outer conductor K2. The base 2 and the lid 3 are made of a metal material with excellent conductivity, such as copper. This reduces the electrical resistance of the surfaces of the base 2 and the lid 3, thereby reducing the loss of the electromagnetic waves F and enabling efficient use of the electromagnetic waves F.

[0029] The base portion 2 is, for example, cylindrical in shape and has a base end surface 2a, a tip surface 2b, and a peripheral surface 2c. The lid portion 3 has a tubular portion 4 that is closed at the tip end and open at the base end, and a flange portion 5 provided at the base end of the tubular portion. A fixing portion M to the base portion 2 is provided on the periphery of the flange portion 5 at a predetermined phase angle. At the fixing portion M, the flange portion 5 and the base portion 2 are joined via an insulating spacer (insulating member) 6 by a fixing member (not shown) such as a bolt. The insulating spacer 6 and a gap E described below electrically insulate the flange portion 5 and the base portion 2, allowing different potentials to be applied to the lid portion 3 and the base portion 2, making it easier to extract ions I.

[0030] In the base portion 2, a notch 7 corresponding to the fixing portion M is provided toward the base end surface 2a at the corner formed by the tip surface 2b and the peripheral surface 2c. The length of the insulating spacer 6 is slightly greater than the depth of the notch 7. As a result, a gap E is formed between the tip surface 2b of the base portion 2 and the flange portion 5, the gap E being determined by the difference between the depth of the notch 7 and the length of the insulating spacer 6 (see FIG. 2).

[0031] By coupling the base portion 2 and the lid portion 3, a resonator 8 that resonates electromagnetic waves F is formed in the housing H. In this embodiment, the resonator 8 has an internal space S1, as shown in Fig. 2. Here, the internal space S1 is a cylindrical space defined by the tubular portion 4 and the tip surface 2b of the base portion 2. On the base portion 2 side, the internal space S1 communicates with the gap E between the tip surface 2b of the base portion 2 and the flange portion 5 described above.

[0032] An ion outlet 9 for extracting ions I is provided in the center of the tip wall 4a of the cylindrical portion 4. At the ion outlet 9, the cylindrical portion 4 is recessed toward the internal space S1 of the resonator 8. The ion outlet 9 has, for example, a circular cross section and is shaped to widen outward.

[0033] In this embodiment, the resonator unit 8 has a choke structure 11 for suppressing leakage of electromagnetic waves F to the outside of the housing H. In the example of FIGS. 1 and 2 , in order to arrange the choke structure 11, an annular notch 12 is provided on the tip surface 2 b of the base unit 2 at a position that is outside the cylindrical unit 4 in a front view. The choke structure 11 is composed of this notch 12 and the above-mentioned gap E. In the example of FIGS. 1 and 2 , the depth of the notch 12 is greater than the depth of the notch 12 of the fixing unit M. The arrangement and depth of the notch 12 can be designed according to the wavelength of the electromagnetic waves F.

[0034] The internal space of the notch 12 communicates with the gap E between the tip surface 2b of the base 2 and the flange 5. With this configuration of the choke structure 11, the electromagnetic waves F traveling from the internal space S1 of the resonator 8 through the gap E toward the notch 12 and the electromagnetic waves F reflected by the notch 12 and returning to the gap E cancel each other out, thereby suppressing leakage of the electromagnetic waves F to the outside of the housing H. By electrically insulating the flange 5 and the base 2 through the gap E, different potentials can be applied to the lid 3 and the base 2. However, although there is a possibility that the electromagnetic waves F will leak from the gap E, the choke structure 11 can suppress leakage of the electromagnetic waves F to the outside of the housing H.

[0035] 2, the ion source 1 includes an internal conductor 13, an electromagnetic wave introduction section 14, and a gas introduction section 15 for generating ions I in the resonator 8. The internal conductor 13 is made of a metal material with excellent conductivity, such as copper, similar to the housing H. The internal conductor 13 is fixed to the center of the tip surface 2b of the base 2, and is located in the internal space S1 of the resonator 8 so as to directly face the ion outlet 9 when the lid 3 is joined to the base 2.

[0036] As described above, in the lid portion 3 which is the outer conductor K2, the cylindrical portion 4 is recessed toward the internal space S1 of the resonator unit 8 at the ion outlet 9. Meanwhile, the tip portion 13a of the inner conductor 13 directly facing the ion outlet 9 has a sharpened shape toward the ion outlet 9. Due to this configuration of the inner conductor 13, a narrowed portion 16 which becomes an electric field concentration region P is formed between the ion outlet 9 and the tip portion 13a of the inner conductor 13 in the resonator unit 8.

[0037] The electromagnetic wave introduction section 14 is a section that introduces the electromagnetic wave F that resonates in the resonator 8. Here, the electromagnetic wave introduction section 14 is a waveguide formed within the base section 2. The electromagnetic wave introduction section 14 is provided in a circular cross section extending from the center of the base end surface 2a of the base section 2 toward the distal end surface 2b. The electromagnetic wave introduction section 14 expands in diameter toward the distal end surface 2b so as to form a flared shape. The open end 14a of the electromagnetic wave introduction section 14 at the distal end surface 2b is circular and has approximately the same diameter as the tubular section 4 in a front view, surrounding the internal conductor 13. Note that instead of the electromagnetic wave introduction section 14, an antenna whose tip protrudes into the internal space S1 of the resonator 8 may be provided, such as an antenna 36 (see FIG. 4 ), which will be described later.

[0038] An annular coupling plate 17 is fitted into the open end 14a. The coupling plate 17 is made of a metal material with excellent conductivity, such as copper, similar to the housing H. The coupling plate 17 is provided with a plurality of arc-shaped through holes 17a when viewed from the front. In the example shown in FIGS. 1 and 2, four through holes 17a are arranged annularly and spaced apart from one another in the circumferential direction of the coupling plate 17 so as to surround the internal conductor 13.

[0039] The gas inlet 15 is a portion that introduces gas G, which is a raw material for ions I, toward the narrowed portion 16. The gas inlet 15 is, for example, a pipe with a circular cross section. The gas inlet 15 extends linearly toward the tip end surface 2b from a position on the base end surface 2a of the base portion 2 that does not overlap with the electromagnetic wave inlet 14 and the notched portion 12 that constitutes the choke structure 11. The gas inlet 15 bends in the in-plane direction of the tip end surface 2b near the tip end surface 2b, and extends linearly within the coupling plate 17 toward the center of the tip end surface 2b at a position that avoids the through hole 17a.

[0040] The gas inlet 15 is bent toward the internal conductor 13 at the center of the tip surface 2b and extends linearly toward the tip 13a through the center of the internal conductor 13. The gas inlet 15 is reduced in diameter near the tip 13a of the internal conductor 13 and communicates with the internal space S1 of the resonator 8 directly opposite the ion outlet 9 through a gas outlet 15a (see FIG. 3 ) provided at the top of the tip 13a. The opening diameter of the gas outlet 15a at the top of the tip 13a is smaller than the minimum diameter of the ion outlet 9 directly opposite the internal conductor 13, for example.

[0041] In the ion source 1 having the above configuration, an electromagnetic wave F such as a microwave is introduced from the electromagnetic wave introducing section 14. The electromagnetic wave F passes through the base section 2 by the electromagnetic wave introducing section 14 and is introduced into the resonator section 8 through the passage hole 17a of the coupling plate 17. The electromagnetic wave F introduced into the resonator section 8 resonates in the internal space S1, and an electric field concentration region P is formed in the narrowed section 16 between the internal conductor 13 and the ion outlet 9, as shown in FIG.

[0042] Gas G is introduced from the gas inlet 15 into the electric field concentration region P formed in the narrowed portion 16. The gas G passes through the base portion 2 by the gas inlet 15 and is introduced into the resonator 8 from the gas outlet 15a at the top of the tip 13a of the internal conductor 13. The gas G introduced into the resonator 8 reaches the electric field concentration region P immediately after being ejected from the gas outlet 15a, and is ionized in the electric field concentration region P. When a predetermined voltage is applied to the external conductor K2, ions I are extracted from the neutral plasma ionized from the gas G and output to the outside from the ion outlet 9.

[0043] As described above, in the ion source 1, the electric field concentration region P is formed by the constriction portion 16 of the internal conductor 13 in the resonator 8, and the gas G, which is the raw material for ions I, is introduced toward the constriction portion 16, which forms the electric field concentration region P. This allows the area where the gas G is ionized to be narrowed by the constriction portion 16, making it possible to generate ions I in a narrow area with high efficiency. Therefore, in the ion source 1, the brightness of the ions I output from the ion outlet 9 is increased. Furthermore, since the ion source 1 employs a structure in which the electromagnetic wave F is resonated using the resonator 8, the power consumption required to form the electric field and the consumption of the gas G are also reduced.

[0044] In this embodiment, the gas outlet 15a of the gas inlet 15 is disposed so as to face the narrowed portion 16. With this configuration, the raw material for the ions I can be supplied intensively to a narrow area where the gas G is ionized. Therefore, the brightness of the ions I output from the ion outlet 9 can be further increased.

[0045] In this embodiment, the ion outlet 9 has a shape that widens outward, and the internal conductor 13 has a pointed shape that approaches the ion outlet 9. This configuration makes it possible to further narrow the area where the gas G is ionized. Therefore, the brightness of the ions I output from the ion outlet 9 can be further increased.

[0046] In this embodiment, the resonator unit 8 has an internal space S1. In this case, the internal conductor 13 can be easily arranged in the resonator unit 8. In addition, in this embodiment, the resonator unit 8 is configured by connecting the external conductor K2 having the ion outlet 9 to the base conductor K1 via the insulating spacer 6. This allows the resonator unit 8 to be configured easily. Since the external conductor K2 is electrically insulated from the base conductor K1, a voltage independent of the base conductor K1 can be applied to the external conductor K2. This allows ions I to be suitably extracted from the ion outlet 9.

[0047] In this embodiment, the resonator unit 8 has a choke structure 11. The arrangement of the choke structure 11 causes the electromagnetic waves F traveling from the internal space S1 of the resonator unit 8 through the gap E toward the notch 12 and the electromagnetic waves F reflected by the notch 12 and returning to the gap E to cancel each other out, thereby suppressing leakage of the electromagnetic waves F to the outside of the housing H.

[0048] It should be noted that the ion source 1 of this embodiment does not necessarily need to include the choke structure 11. In this case, the gap E between the base portion 2 and the lid portion 3 may not be formed, and the flange portion 5 of the lid portion 3 may be joined to the tip surface 2 b of the base portion 2 without any gap, without the insulating spacer 6 interposed therebetween.

[0049] 4 is a perspective view showing the configuration of an ion source according to a modified example. As shown in the drawing, an ion source 21 according to the modified example differs from the above embodiment in that the resonator 18 is formed of a dielectric 22, in that the resonator 8 has an internal space S1.

[0050] Specifically, the ion source 21 includes a cylindrical dielectric body 22 made of a solid dielectric material, such as ceramic, and an extraction electrode 23. The dielectric body 22 has a base end surface 22a, a tip end surface 22b, and a peripheral surface 22c. An internal space S2 having, for example, a circular cross section is provided in the center of the dielectric body 22. The internal space S2 is defined so as to penetrate the dielectric body 22 from the base end surface 22a to the tip end surface 22b. The internal space S2 has a constant diameter on the base end surface 22a side. The internal space S2 has a tapered shape near the tip end surface 22b, forming a narrowed portion 26 that serves as an electric field concentration region P. The internal space S2 has a flared shape toward the tip end surface 22b from the narrowed portion 26. This flared portion functions as an ion extraction port 29.

[0051] The base end surface 22a, the tip end surface 22b, the peripheral surface 22c, and the inner wall surface 22d defining the internal space S2 of the dielectric 22 are covered with a conductor K, except for the narrowed portion 26. The conductor K is made of a metal material with excellent conductivity, such as copper, similar to the base portion 2 and the lid portion 3 of the above embodiment. The conductor K covering the inner wall surface 22d defining the internal space S2 corresponds to the internal conductor in the present disclosure. An insulating layer made of an insulating material may be further provided on the surface of the conductor K so as to cover the conductor K. The arrangement of such an insulating layer can suppress electric shock caused by power supplied to the conductor K.

[0052] Here, the electromagnetic wave introduction section 34 is configured by an antenna 36 inserted into the dielectric 22. The antenna 36 is inserted into the dielectric 22 from the base end surface 22a side at a position different from the internal space S2. The antenna 36 extends linearly and substantially parallel to the gas introduction section 35. The antenna 36 extends toward the distal end surface 22b in the direction of the central axis of the dielectric 22, for example, to reach the vicinity of the position of the narrowed portion 26. Note that, from the viewpoint of reliably introducing the electromagnetic wave F into the dielectric 22, it is preferable that the antenna 36 be in non-contact with the conductor K. In the example of FIG. 4 , the antenna 36 is in the form of a coaxial cable with an insulator and an outer sheath, except for the portion inserted into the dielectric 22. This ensures the transmission of the electromagnetic wave F from the outside and the reliable introduction of the electromagnetic wave F into the dielectric 22.

[0053] The gas inlet 35 is introduced into the internal space S2 from the base end surface 22a side, and extends linearly with a constant diameter along the central axis of the dielectric 22. A gas outlet 35a at the tip of the gas inlet 35 faces the narrowed portion 26. The opening diameter of the gas outlet 35a is smaller than the diameter of the narrowed portion 26 and the minimum diameter of the ion outlet 29.

[0054] The extraction electrode 23 is made of a metal material with excellent conductivity, such as copper. A through hole 23a with a circular cross section is provided in the center of the extraction electrode 23 to allow the generated ions I to pass through. There are no particular restrictions on the diameter of the through hole 23a, but it is, for example, equal to or smaller than the diameter of the narrowed portion 26. The extraction electrode 23 is disposed at a distance from the tip surface 22b of the dielectric 22 so that the through hole 23a directly faces the ion outlet 29.

[0055] In the ion source 21 having such a configuration, electromagnetic waves F such as microwaves are introduced from the antenna 36, ​​which is the electromagnetic wave introduction section 34. The electromagnetic waves F introduced by the antenna 36 resonate in the dielectric 22, which is the resonator 18, and an electric field concentration region P is formed in the narrowed section 26. Gas G is introduced from the gas introduction section 35 into the electric field concentration region P formed in the narrowed section 26. The gas G is introduced into the resonator 18 from the gas outlet 35a of the gas introduction section 35. The gas G introduced into the resonator 18 reaches the electric field concentration region P immediately after being ejected from the gas outlet 35a, and is ionized in the electric field concentration region P. When a predetermined voltage is applied to the extraction electrode 23, ions I are extracted from the neutral plasma ionized from the gas G and output to the outside from the ion extraction port 29.

[0056] In this ion source 21, the same effects as those of the above embodiment are achieved, and since the area where the gas G is ionized can be narrowed by the constriction portion 26, it is possible to generate the ions I in a narrow area with high efficiency. Therefore, the brightness of the ions I output from the ion outlet 29 is increased. Furthermore, since a structure is adopted in which the electromagnetic wave F is resonated using the resonator 18, the power required to form the electric field and the consumption of the gas G are also reduced.

[0057] In this embodiment, the resonator unit 18 is made of the dielectric 22. With this configuration, it is possible to reduce the resonator length of the resonator unit 18 (particularly the length in the central axis direction of the dielectric 22), thereby reducing the size of the resonator unit 18. Furthermore, in this embodiment, the electromagnetic wave introducing unit 34 is made of an antenna 36 inserted in the dielectric 22. This allows the electromagnetic wave F to be introduced into the resonator unit 18 made of the dielectric 22 with high efficiency.

[0058] The present disclosure may include further findings and aspects.

[0059] For example, the inner dimension (here, inner diameter) of the gas discharge port 15 a, 35 a of the ion source 1, 21 described above may be 30 times or less the skin depth determined by the frequency of the electromagnetic wave F and the angular frequency of the plasma generated in the resonance unit 8, 18. The inner dimension (inner diameter) of the gas discharge port 15 a, 35 a of the ion source 1, 21 may be 20 times or less, or may be 10 times or less, the skin depth determined by the frequency of the electromagnetic wave F and the angular frequency of the plasma generated in the resonance unit 8, 18. With such a configuration, it is possible to allow the electromagnetic wave F to sufficiently penetrate into the gas G, and the ionization of the gas G can be effectively promoted.

[0060] The skin depth δ can be calculated using the following formula (1): In formula (1), c is the speed of light, ω is the ｐ is the angular frequency of the plasma, ω is the frequency of the electromagnetic wave, ε ０ is the dielectric constant of vacuum, n is the plasma density, e is the elementary charge, and m is the ion mass.

[0061] As an example, if the plasma size is φ50 μm, the current is 3 mA, the electron temperature is 2 eV, and the ion mass (xenon) is 131, the plasma density n is approximately 3.22 × 10 １７ ( / cm ３ ), plasma angular frequency ω ｐ is approximately 3.19 x 10 １３ Hz, and the skin depth δ calculated from equation (1) is about 9.4 μm. If the inner dimension (inner diameter) of the gas release ports 15 a and 35 a is about 10 times the skin depth δ, the inner diameter of the gas release ports 15 a and 35 a is about 100 μm.

[0062] In the ion source 1, an insulating enclosure 41 may be arranged in the narrowed portion 16 so as to surround the flow path of the gas G. Furthermore, a nozzle 42 having an inner dimension (inner diameter) smaller than that of the ion outlet 9 may be arranged in the gas outlet 15a. In the example of Fig. 5, the enclosure 41 is formed of an insulating material such as ceramic, and has a cylindrical shape with a length corresponding to the narrowed portion 16. The inner diameter of the enclosure 41 is approximately the same as that of the gas outlet 15a, and the gas outlet 15a and the ion outlet 9 are airtightly connected by the enclosure 41.

[0063] 5, the nozzle 42 is formed into a cylindrical shape from a high-melting-point metal such as tungsten, and is inserted into the gas outlet 15 a without protruding from the gas outlet 15 a. The inner diameter of the base end of the nozzle 42 is smaller than that of the ion outlet 9, for example, and the inner diameter of the tip end of the nozzle 42 is even smaller than the inner diameter of the base end.

[0064] By using such an enclosure member 41 and nozzle 42, the range in which the gas G can exist in the narrowed portion 16 is physically limited, so that the raw material for the ions I can be supplied more intensively to the narrow area where the gas G is ionized. Therefore, the brightness of the ions I output from the ion outlet 9 can be further increased. Note that it is not necessary to use both the enclosure member 41 and the nozzle 42, and an embodiment in which only one of them is provided may also be used.

[0065] 5 illustrates a cylindrical enclosure 41 having a length corresponding to the narrowed portion 16. However, as shown in FIG. 6, the internal space S1 of the resonator 8 may be filled with the enclosure 41. In the example of FIG. 6, in addition to the internal space S, the enclosure 41 also fills the gap E between the front end surface 2b of the base 2 and the flange 5, and the notch 12 in the front end surface 2b of the base 2. With this configuration, as in the case of FIG. 5, the brightness of the ions I output from the ion outlet 9 can be further increased. Furthermore, by filling the internal space S1 of the resonator 8 with the insulating enclosure 41, the base 2 and the resonator 8 can be made smaller. This allows the ion source 1 to be made smaller overall, making it easier to install in an ion gun or the like.

[0066] 7 is a schematic diagram showing the configuration of an ion gun according to an embodiment of the present disclosure. The ion gun 51 shown in FIG. 7 is configured as an apparatus for micromachining the surface of a target Q using ions I output from, for example, the ion source 1 or 21. The ion gun 51 includes the above-described ion source 1 or 21, an extraction electrode 52, an aperture 53, an optical system 54, an acceleration power supply 57, and an extraction power supply 58. The ion source 1 or 21 and the target Q are electrically connected to the acceleration power supply 57. The acceleration power supply 57 supplies an acceleration voltage to the ion source 1 or 21 for irradiating the target Q with ions I at high speed.

[0067] The extraction electrode 52 is electrically connected to the extraction power supply 58. The extraction electrode 52 receives a voltage from the extraction power supply 58 and extracts ions I output from the ion source 1, 21 to the outside. In the ion source 1, the extraction electrode 52 may be configured by the cylindrical portion 4 and the flange portion 5 that define the resonance portion 8 (see FIG. 2). Alternatively, the extraction electrode 52 may be disposed as a separate member in front of the ion outlet 29, as in the ion source 21 (see FIG. 4; the extraction electrode 23 in FIG. 4 corresponds to the extraction electrode 52). When the extraction electrode 52 is disposed as a separate member, the choke structure 11 in the ion source 1 is not necessary, and the base portion 2 can be configured to have the same diameter as the resonance portion 8.

[0068] The aperture 53 is a part that cuts the ions I output from the ion sources 1 and 21 to only ions of a required vector. In the example of Fig. 7, the aperture 53 is disposed between the extraction electrode 52 and the optical system 54, but one or more apertures may also be disposed in the optical system 54.

[0069] The optical system 54 is a part that guides the ions I extracted by the extraction electrode 52 toward the target Q. In the example of FIG. 7 , the optical system 54 is configured to include a pair of electrostatic lenses 55A and 55B and a polarizer 56. The electrostatic lenses 55A and 55B are arranged to sandwich the polarizer 56. The electrostatic lens 55A converts the ions I incident on the polarizer 56 into parallel rays, and the electrostatic lens 55B focuses the ions I from the polarizer 56 onto the surface of the target Q. The polarizer 56 adjusts the irradiation axis of the ions I toward the target Q.

[0070] In the ion gun 51 having the above configuration, by using the above-described ion sources 1 and 21, the area where the gas G is ionized can be narrowed by the constriction portions 16 and 26, and ions I can be generated in a narrow area with high efficiency. The high brightness of the ions I output from the ion sources 1 and 21 allows processing of the target object Q at high speed and with high precision.

[0071] 1, 21...ion source, 6...insulating spacer (insulating member), 8, 18...resonator, 9, 29...ion outlet, 11...choke structure, 13...internal conductor, 14, 34...electromagnetic wave introduction section, 15, 35...gas introduction section, 15a, 35a...gas outlet, 16, 26...narrowed section, 22...dielectric, 36...antenna, F...electromagnetic wave, G...gas, I...ion, P...electric field concentration region, S1...internal space, K1...base conductor, K2...external conductor, 41...enclosure member, 42...nozzle, 51...ion gun, 52...extraction electrode, 54...optical system.

Claims

1. An ion source comprising: a resonator having an ion outlet for extracting ions; an internal conductor that forms a constriction portion between the ion outlet and the resonator, which serves as an electric field concentration region; an electromagnetic wave introduction portion that introduces an electromagnetic wave that resonates in the resonator; and a gas introduction portion that introduces a gas that is a raw material for ions into the constriction portion.

2. The ion source according to claim 1, wherein the gas outlet of said gas inlet is disposed so as to face said narrowed portion.

3. An ion source according to claim 2, wherein the inner dimension of said gas ejection port is 30 times or less the skin depth determined by the frequency of said electromagnetic wave and the angular frequency of the plasma generated in said resonator.

4. The ion source according to claim 2 or 3, wherein a nozzle having an inner dimension smaller than that of the ion outlet is disposed at the gas outlet.

5. The ion source according to any one of claims 1 to 4, wherein the ion outlet has a shape that flares outward, and the internal conductor has a shape that is pointed toward the ion outlet.

6. The ion source according to any one of claims 1 to 5, wherein the resonator has an internal space.

7. The ion source according to claim 6, wherein said resonator portion is constructed by coupling an external conductor having said ion outlet to a base conductor via an insulating member.

8. The ion source according to claim 6 or 7, wherein the resonator portion has a choke structure.

9. The ion source according to any one of claims 1 to 5, wherein the resonator portion is made of a dielectric material.

10. The ion source according to claim 9, wherein the electromagnetic wave introduction section is constituted by an antenna inserted within the dielectric body.

11. The ion source according to any one of claims 1 to 10, wherein an insulating surrounding member is disposed in the narrowed portion so as to surround the gas flow path.

12. An ion gun comprising: an ion source according to any one of claims 1 to 11; an extraction electrode for extracting the ions from the ion source; and an optical system for directing the ions extracted by the extraction electrode towards a target object.

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