JP4602944B2 - X-ray condenser lens - Google Patents

Description

  The present invention relates to an X-ray condensing device, and more particularly to an X-ray condensing lens that condenses light using a waveguide and a shielding zone in combination.

  In recent years, with the progress of nanotechnology development, structural evaluation of materials at the nanometer level is required. There are scanning microscopes, electron microscopes and the like as nanometer level evaluation methods, but all of them require high vacuum conditions and thinning of the sample, and it is difficult to measure the sample to be observed as it is. On the other hand, with the progress of X-ray focusing technology in recent years, micrometer level X-ray beams have been obtained, and X-ray diffraction and fluorescent X-rays using such X-ray beams have been obtained. Material evaluation such as analysis has finally become possible.

  X-ray beam condensing can be broadly divided into (A) a method using an X-ray optical element such as an X-ray mirror (see Non-Patent Document 1), and (B) asymmetric Bragg reflection of a crystal. (C) a method using an X-ray Fresnel zone plate (see non-patent document 3), and (D) a method using an X-ray waveguide (see non-patent document 4). . Table 1 shows the current status and problems of each condensing method.

  Of these, the method of using the optical element for X-rays such as the X-ray mirror of (A) and the method of using the asymmetric Bragg reflection of the crystal of (B) are almost at the technical limit at present. Condensation is difficult.

On the other hand, in the hard X-ray region where the X-ray energy is 5 keV or more, a condensed beam having a beam size of 100 nanometers or less is obtained by the method using the X-ray Fresnel zone plate of (C). When the Fresnel zone plate is irradiated with an X-ray beam, a part of the X-ray beam is absorbed by the zone plate and is not transmitted, but the other X-ray beams pass through the zone plate as they are. At this time, assuming that the wavelength of the X-ray beam is λ and the focal length of the X-ray Fresnel zone plate is f, (2nλf) ^1/2 and {2nλf) ^1/2 from the center of the X-ray beam to the direction orthogonal to the beam traveling direction (2n + 1) λf} ^1/2 (n = 0, 1, 2,...) Or between {(2n + 1) λf} ^1/2 and {(2n + 2) λf} ^1/2 When a shielding zone made of a material that does not transmit rays is provided, the transmitted X-rays interfere with each other, so that the X-ray beam can be collected.

  The light collecting principle is the same as that of visible light, and the details thereof are described in Non-Patent Document 5, for example, and it is known that the spatial resolution of the zone plate light collecting system is substantially equal to the outermost zone width. . Therefore, in the case of an X-ray Fresnel zone plate, the maximum spatial resolution is defined by the width of the narrowest shielded zone constituting the zone plate. In order to manufacture such a zone plate, lithography technology for semiconductor manufacturing including electron beam drawing is used. Although the semiconductor lithography technology itself can draw a line pattern of 10 nanometers, when producing a ring-shaped pattern necessary as an X-ray Fresnel zone plate, drawing of a width of about 40 nanometers is currently limited. The resolution of the X-ray Fresnel zone plate itself is about 50 nanometers. Furthermore, when producing an X-ray Fresnel zone plate, since it is necessary to precisely produce a large number of ring-shaped patterns, the X-ray Fresnel zone plate itself is very expensive.

On the other hand, in the case of the method (D) using the X-ray waveguide, the size of the X-ray beam is determined by the size of the core constituting the waveguide. Here, when the refractive index in the X-ray region of the cladding layer covering the core layer is N1, and the refractive index in the X-ray region of the core layer is N2, the relationship of (the real part of N1) <(the real part of N2) There is. When an X-ray beam is incident on the core layer of the X-ray waveguide, the X-ray beam travels through the core layer. At this time, when the thickness of the core layer is sufficiently small, only X-rays in a specific state are transmitted. At this time, the thickness D of the core layer, the wavelength λ of the X-ray beam, and the X-ray beam to the cladding layer are transmitted. It is known that there is the following relationship with the incident angle φ (see Non-Patent Document 6).
2Dsin (φ) = mλ (m = 0, 1, 2,...) (1)

  The condition of formula (1) indicates that there is a limit to the incident angle φ of the X-ray incident on the X-ray waveguide, and X-rays having other incident angles cannot pass through the core layer. Is shown. The angle at which total reflection occurs is selected as the incident angle φ of the X-ray beam from the core layer to the cladding layer, and the length is such that all the X-ray beam passing through the cladding layer is absorbed and does not pass through the waveguide exit. When the X-ray waveguide is used, the X-ray beam can be condensed to the size substantially the same as the size of the core layer at the exit of the waveguide. Since such an X-ray waveguide can be manufactured by vapor deposition, it is easy to reduce the thickness of the core layer to 10 nanometers or less, and an X-ray beam having a size of several nanometers can be manufactured. It is possible in principle.

  However, in the case of the method using the X-ray waveguide, the X-ray beam can be condensed in the thickness direction of the core layer, but in the in-plane direction of the core layer perpendicular to the thickness direction and the traveling direction of the beam. The X-ray beam cannot be collected. In other words, the X-rays that can be extracted at the exit of the X-ray waveguide have the same size as the incident X-rays in the in-plane direction of the core layer, so that the X-ray waveguide can collect only in one dimension. It is difficult to obtain a pointed X-ray microbeam which is an illuminated linear X-ray microbeam and is focused in a two-dimensional direction.

Yamauchi et al., “Two-dimensional Submicron Focusing of Hard X-rays by Two Elliptical Mirrors Fabricated by Plasma Chemical Vaporization Machining and Elastic Emission Machining”, Jpn.J.Appl.Phys., Vol.42, 2003, p.7129-7134 Tsusaka et al., “Formation of Parallel X-Ray Microbeam and Its Application”, Japanese Journal of Applied Physics, Vol.39, 2000, p.635-637 E. Spiller, "Soft X-ray Optics", WA: SPIE Optical Engineering Press, 1994, p.81-97 Jun Kawai, “X-ray traveling wave”, Surface Science, Vol. 22, no. 6, p. 397-403, 2001 Hiroshi Kubota, "Wave Optics", Iwanami Shoten, p. 305, 1971 W. Jark et al., “High gain beam compression in new-generation thin-film x-ray waveguide”, Applied Physics Letters, Vol. 78, No. 9, 2001, p.1192-1194

  As described above, with the method using the X-ray Fresnel zone plate, it is difficult to obtain an X-ray beam with a size of 10 nanometers, and with the method using an X-ray waveguide, the size of several nanometers is used. Although it is possible to obtain an X-ray beam, the X-ray beam is condensed in only a one-dimensional direction, an X-ray beam condensed in a two-dimensional direction cannot be obtained, and the X-ray intensity is weak. There was a problem. As described above, with the progress of research on nanostructured materials, a technique for evaluating nanostructured materials with a spatial resolution of 10 nanometer level is required. However, the conventional X-ray beam focusing method has a level of 10 nanometer level. It is difficult to achieve a spatial resolution of

  The present invention has been made to solve the above-described problems, and an X-ray collection capable of realizing a high-intensity X-ray microbeam at a nanometer level, which has been difficult with the conventional X-ray beam focusing technology. An object is to provide an optical lens.

The present invention is an X-ray condensing lens that collects X-rays using an X-ray waveguide in which a clad layer is formed on both opposing surfaces of a core layer, and the X-rays are incident in parallel to the opposing surfaces. A shielding zone made of a material that does not transmit X-rays is disposed upstream of the core layer along a part of the core layer or in a direction opposite to the traveling direction of the X-ray beam , The wavelength is λ, the focal length is f 1, the traveling direction of the X-ray beam is the first direction, and the stacking direction of the core layer and the cladding layer is the second direction out of the directions orthogonal to the first direction, When the direction orthogonal to the first direction and the second direction is the third direction, the distance along the third direction from the center of the X-ray beam is (2nλf) ^1/2 (where n is 0, 1 , 2, the first region between the position of the ···) {(2n + 1) λf} 1/2 position, the Located on any of the second region except for the first region is positioned upstream by the focal length f from the X-ray beam outlet of the X-ray waveguide along said first direction and reverse direction The length along the first direction is set to such a dimension that there is no X-ray that passes through the shielding zone .
In one configuration example of the X-ray condenser lens of the present invention, the core layer is made of a material containing at least one of carbon, silicon, beryllium, and a polymer material, and the cladding layer and the shielding zone are made of tungsten. , Ruthenium, and tantalum.

According to the present invention, by providing the shielding zone in the X-ray waveguide, the X-ray beam can be condensed using the X-ray waveguide in the thickness direction of the core layer. In the direction orthogonal to the traveling direction of the line beam, the X-ray beam can be condensed by using the same condensing action as the X-ray Fresnel zone plate. As a result, in the present invention, it is possible to easily obtain a high-intensity X-ray microbeam condensed to the nanometer order, such as quantum dots, nanodots, nanowires, nanoparticles, and fine gates of highly integrated semiconductor materials. It is possible to evaluate the structure of various nanomaterials and contribute to the development of semiconductor materials and semiconductor devices.
In the present invention, a normal X-ray mirror or the like is provided by arranging a shielding zone in a region upstream from the X-ray beam exit of the X-ray waveguide by the focal length f along the direction opposite to the traveling direction of the X-ray beam. Thus, it is possible to obtain an X-ray beam that can be further condensed and easily used for analysis and the like.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a plan view showing a configuration of an X-ray condenser lens according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line II of the X-ray condenser lens of FIG. It is. In FIG. 1A, it is assumed that an X-ray shielding layer and an X-ray beam under the upper ruthenium layer described later are seen through.
The X-ray condensing lens of the present embodiment incorporates a Fresnel zone plate in a part of the X-ray waveguide, and an X-ray waveguide portion 14 for condensing the X-ray beam in the vertical direction; It comprises an X-ray zone plate part 15 and an X-ray condenser part 16 for condensing the X-ray beam in the horizontal direction.

  In FIG. 1, 8 is a silicon substrate, 9 is a lower ruthenium layer which is a cladding layer formed on the silicon substrate 8, 10 is a carbon layer which is a core layer formed on the lower ruthenium layer 9, and 11 is carbon. An upper ruthenium layer which is a clad layer formed on the layer 10, 12 is an X-ray zone plate formed in a part of an X-ray waveguide composed of a lower ruthenium layer 9, a carbon layer 10 and an upper ruthenium layer 11. Is an X-ray shielding layer made of a tantalum material.

  Assuming that the refractive index in the X-ray region of the cladding layer is N1 and the refractive index in the X-ray region of the core layer is N2, between the refractive indexes N1 and N2, (the real part of N1) <(the real number of N2) Part). In the present embodiment, in order to prevent X-rays leaking from the cladding layer, the thickness of the lower ruthenium layer 9 and the upper ruthenium layer 11 is 100 nanometers, and the thickness of the carbon layer 10 through which X-rays pass is 10 nanometers. M.

The X-ray shielding layer 12 has a distance along the direction perpendicular to the traveling direction of the X-ray beam from the center of the X-ray beam as Z _2n, where λ is the wavelength of the X-ray and f is the focal length as the condenser lens. (N is 0, 1, 2,...) And the first region between the position of Z _{2n + 1} and the second region excluding the first region. In addition, it is disposed upstream from the X-ray waveguide exit 17 by a focal length f along the direction opposite to the traveling direction of the X-ray beam. In the example of FIGS. 1A and 1B, the center of the X-ray beam is the II line in FIG. 1A, and the traveling direction of the X-ray beam is in FIGS. 1A and 1B. The direction perpendicular to the traveling direction of the X-ray beam is the vertical direction in FIG.

Distances (coordinates) Z _2n and Z _{2n + 1} from the center of the X-ray beam of the X-ray shielding layer 12 are obtained by the following equations.
Z _2n = (2nλf) ^1/2 (2)
Z _{2n + 1} = {(2n + 1) λf} ^1/2 (3)

FIG. 2 shows a case where the X-ray shielding layer 12 is provided in a first region between Z _2n (n is 0, 1, 2,...) And Z _{2n + 1} . When the X-ray shielding layer 12 is provided in the second region except between Z _2n and Z _{2n + 1} , the X-ray shielding layer 12 may be disposed between the black background regions in FIG.
In the present embodiment, it is assumed that the wavelength λ of X-rays is 0.0711 nanometers and the focal length f is 10 millimeters. For this reason, the length of the X-ray condensing part 16 is 10 millimeters.

In order to efficiently collect the X-rays in the X-ray zone plate unit 15, it is necessary that there is no X-rays that pass through the X-ray shielding layer 12, but in this embodiment, the X-ray zone plate unit 15 The length (the dimension in the left-right direction in FIG. 1A) is 75 microns. At this time, the ratio of X-rays transmitted through the X-ray shielding layer 12 is estimated to be about 2.54 × 10 ⁻⁴ % from the absorption coefficient of tantalum. Absent.

  Next, a method for manufacturing the X-ray condenser lens of the present embodiment will be described. First, the lower ruthenium layer 9 is formed on the silicon substrate 8 by vapor deposition, for example. Tantalum is deposited on the lower ruthenium layer 9 and then processed by a method such as electron beam lithography to form the X-ray shielding layer 12. Subsequently, a carbon layer 10 is formed on the lower ruthenium layer 9 by, for example, sputtering. At this time, the thickness of the carbon layer 10 is set to be equal to or less than the thickness of the X-ray shielding layer 12. Finally, the upper ruthenium layer 11 is formed on the carbon layer 10 and the X-ray shielding layer 12, for example, by vapor deposition, thereby completing the production of the X-ray condenser lens.

  When the X-ray beam 13 is incident on the X-ray condensing lens thus manufactured from the left side of FIGS. 1A and 1B, it proceeds in a waveguide mode depending on the length of the X-ray waveguide portion 14. Although there is a possibility that the presence of X-rays other than X-rays cannot be ignored, in this embodiment, the length of the X-ray waveguide portion 14 is 10 millimeters. Since this value is sufficiently larger than the wavelength of the X-ray, only the X-ray beam that passes through the X-ray waveguide section 14 satisfies the formula (1), and the direction perpendicular to the silicon substrate 8 ( The size of the X-ray beam in the vertical direction in FIG. 1B is about 10 nanometers.

  The X-rays that have passed through the X-ray waveguide unit 14 then enter the X-ray zone plate unit 15. At this time, a part of the X-rays passing through the waveguide is absorbed by the X-ray shielding layer 12, and other X-rays reach the X-ray condensing unit 16. Since the X-ray beam cannot spread in the direction perpendicular to the silicon substrate 8, the vertical size of the X-ray beam is about 10 nanometers as in the case of the X-ray waveguide portion 14.

  On the other hand, since there is nothing that constrains the mode of the X-ray beam in the horizontal plane of the waveguide, the X-rays pass through the X-ray condensing unit 16 from the opening of the X-ray zone plate unit 15 as a one-dimensional spherical wave. proceed. As a result, the X-rays traveling in the waveguide are condensed in the horizontal direction (vertical direction in FIG. 1A) due to the interference effect, and are condensed at the X-ray waveguide outlet 17 of the X-ray condensing unit 16. Is done. The horizontal size of the X-ray beam at this time is determined by the minimum width of the X-ray shielding layer 12 (the vertical dimension in FIG. 1A). In the present embodiment, the minimum value of the width of the X-ray shielding layer 12 is about 8 nanometers, so the horizontal beam size is about 10 nanometers. In addition, the beam size in the vertical direction reflects the thickness of the carbon layer 10 that is the core layer, and an X-ray beam of about 10 nanometers can be obtained.

As illustrated above, the X-ray condensing lens of the present embodiment can perform two-dimensional condensing of the X-ray beam while effectively utilizing the energy of the incident X-ray beam. Since an intense X-ray microbeam can be realized, a higher-level structural evaluation of a nanometer level material becomes possible.
When the X-ray condenser lens of the present embodiment is used for material evaluation, the light emitted from the X-ray condenser lens is directly irradiated to the material to be evaluated, or the light emitted from the X-ray condenser lens is further applied. The material may be evaluated by collecting the light with a mirror or the like and irradiating the material to be evaluated, detecting X-rays diffracted by the material or fluorescent X-rays generated from the material.

  In the present embodiment, the X-ray shielding layer 12 is provided in a region upstream from the X-ray waveguide exit 17 by the focal length f along the direction opposite to the traveling direction of the X-ray beam. Thus, it is possible to obtain an X-ray beam that can be further condensed by using the above-mentioned method and can be easily used for analysis. When the focal point of the X-ray is at a position shifted forward (in the waveguide) from the X-ray waveguide exit 17, the X-ray beam has already spread in the vertical direction in FIG. In addition, when the focal point of the X-ray is located behind the X-ray waveguide outlet 17 (outside the waveguide), the X-ray beam is moved in the vertical direction in FIG. Since it starts to spread, the minimum spot size cannot be obtained. On the other hand, if the focal point of the X-ray coincides with the X-ray waveguide outlet 17, the X-ray beam is then expanded isotropically, so that an easy-to-use X-ray beam can be obtained.

  In addition, this invention is not limited to the above embodiment. For example, in the present embodiment, the X-ray shielding layer 12 is provided in the core layer of the X-ray waveguide, but may be provided on the front surface of the core layer. In this case, the X-ray shielding layer 12 may be provided upstream from the X-ray waveguide outlet 17 by the focal length f.

  In this embodiment mode, carbon is used as the material for the core layer. However, the material for the core layer may be any material including at least one of carbon, silicon, beryllium, and a polymer material. Further, as the material of the core layer, a material containing at least one of boron, beryllium, aluminum, fluorine, calcium, magnesium, and titanium may be used, and polyimide, polymethyl methacrylate, fluorine resin, or chlorine resin is used. Also good.

  In the present embodiment, ruthenium is used as the material of the cladding layer, but any material containing at least one of tungsten, ruthenium, and tantalum may be used. Further, as a material for the cladding layer, a material containing at least one of nickel, cobalt, chromium, vanadium, titanium, germanium, molybdenum, zirconium, indium, rhenium, silver, gold, platinum, and tantalum may be used. The material of the X-ray shielding layer 12 may be the same as that of the clad layer, or a material different from the clad layer may be used from those listed as the clad layer material.

  The present invention can be applied to an X-ray condensing device.

It is the top view and sectional drawing which show the structure of the X-ray condensing lens which concerns on embodiment of this invention. It is a top view for demonstrating the position of the X-ray shielding layer in embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 8 ... Silicon substrate, 9 ... Lower ruthenium layer, 10 ... Carbon layer, 11 ... Upper ruthenium layer, 12 ... X-ray shielding layer, 13 ... X-ray beam, 14 ... X-ray waveguide part, 15 ... X-ray zone plate part 16 ... X-ray condensing part, 17 ... X-ray waveguide exit.

Claims (2)

An X-ray condensing lens that condenses X-rays using an X-ray waveguide having clad layers formed on both opposing surfaces of a core layer,
A shielding zone made of a material that does not transmit X-rays to the upstream side of the core layer along a part of the core layer where X-rays enter parallel to the opposing surfaces or in the direction opposite to the traveling direction of the X-ray beam. Have
The shielding zone has an X-ray wavelength of λ, a focal length of f 1, a traveling direction of the X-ray beam in a first direction, and a stack of the core layer and the cladding layer in a direction orthogonal to the first direction. When the direction is the second direction, and the first direction and the direction perpendicular to the second direction are the third direction, the distance along the third direction from the center of the X-ray beam is (2nλf) ^{1. / 2} (where n is 0, 1, 2,...) And the position of {(2n + 1) λf} ^1/2 , the second area excluding this first area Disposed at any one of them, and is disposed upstream from the X-ray beam exit of the X-ray waveguide by the focal length f along the direction opposite to the first direction, in the first direction. X-rays length along, characterized in that the X-rays transmitted through the shielding zone is set to a dimension so as not to exist Light lens. The X-ray condenser lens according to claim 1,
The core layer is made of a material including at least one of carbon, silicon, beryllium, and a polymer material,
The X-ray condenser lens according to claim 1, wherein the cladding layer and the shielding zone are made of a material containing at least one of tungsten, ruthenium, and tantalum .

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