JP2013117444A - X-ray optical element and x-ray optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray optical element which can easily emit X rays of which phases are highly aligned, with higher propagation efficiency.SOLUTION: An X-ray optical element comprises: an X-ray waveguide; and a mechanism for selectively transmitting X rays emitted from the X-ray waveguide. The X-ray waveguide comprises: a core for wave-guiding the X rays; and a clad for confining the X rays in the core. The core has a periodic structure composed of a plurality of materials different in real part of a refractive index. A total reflection critical angle of the X rays in an interface between the clad and the core is larger than a Bragg angle caused by periodicity of the core. The mechanism for selectively transmitting the X rays selectively transmits the X rays emitted from the X-ray waveguide at a predetermined emission angle.

Description

  The present invention relates to an X-ray optical element.

  X-rays are widely used in the fields of medicine, nondestructive inspection, crystal structure analysis, and the like. Since the refractive index difference between different substances with respect to electromagnetic waves with a short wavelength of several tens of nm or less such as X-rays is very small, a large spatial optical system is used to control such electromagnetic waves. Recently, research has been conducted on X-ray waveguides that confine and propagate electromagnetic waves in thin films and multilayers with the aim of reducing the size and increasing the functionality of these optical systems, which are the mainstream. . Non-Patent Document 1 discloses an X-ray waveguide made of a multilayer film of nickel and carbon.

Physical Review B, Volume 62, p. 16939 (2000)

  The waveguide disclosed in Non-Patent Document 1 includes an X-ray waveguide clad made of nickel and an X-ray waveguide core made of carbon. In this waveguide, X-rays are confined by total reflection at the carbon / nickel interface, and the waveguide configured to guide is functioned as a laminated structure. For this reason, a combination of cores sandwiched between clads can guide X-rays having a larger light amount than a set of waveguides (hereinafter referred to as single-layer waveguides).

  On the other hand, in the waveguide having such a configuration, each of the laminated waveguide configurations (a set of a core and a clad sandwiching the core) functions as a separate single-layer waveguide. For this reason, the advantages of the single-layer waveguide are reduced, such that the phases of the X-rays emitted as a whole are uniform, and the light collection and divergence suppression effects are achieved.

  In contrast, the inventors have an X-ray waveguide that includes a clad and a core and confines X-rays in the core by total reflection at the core / cladding interface, and the core has a plurality of different refractive index real parts. Proposed X-ray waveguides with periodically arranged materials. In this waveguide, a mode in which X-rays guided through the core cause multiple interference and efficiently guide in accordance with this periodic structure (hereinafter referred to as a periodic resonant waveguide mode) is selected. Thus, it becomes possible to guide X-rays with a large phase of light quantity with high efficiency.

The present invention is an X-ray optical element having an X-ray waveguide and a mechanism for selectively transmitting X-rays emitted from the X-ray waveguide,
The X-ray waveguide has a core for guiding X-rays, and a clad for confining the X-rays in the core,
The core has a periodic structure composed of a plurality of substances having different real parts of refractive index,
The X-ray total reflection critical angle at the interface between the cladding and the core is larger than the Bragg angle due to the periodicity of the core,
The mechanism that selectively transmits X-rays relates to an X-ray optical element that selectively transmits X-rays emitted from the X-ray waveguide at a predetermined emission angle.

  According to the present invention, an X-ray optical element having a mechanism that selectively transmits X-rays whose positions are fixed with respect to the X-ray waveguide of the present invention can be easily and highly phase-shifted with higher propagation efficiency. An X-ray optical element capable of emitting uniform X-rays can be provided.

The conceptual diagram of the X-ray optical element of this invention is shown. The conceptual diagram of the X-ray waveguide of this invention is shown. It is explanatory drawing of a wave vector and an effective propagation angle. The X-ray waveguide of Example 1 is shown. The schematic diagram of the incident angle dependence of the X-ray transmission intensity is shown.

  The X-ray optical element of the present invention has an X-ray waveguide and a mechanism that selectively transmits X-rays emitted from the X-ray waveguide.

  The present inventors provide an X-ray waveguide that includes a clad and a core and confines X-rays in the core by total reflection at the interface between the core and the clad. We have found X-ray waveguides in which materials are periodically arranged. In this waveguide, a mode (hereinafter referred to as “periodic resonance waveguide mode”) is selected in which X-rays guided through the core cause multiple interference and efficiently guide in accordance with this periodic structure. For this reason, it becomes possible to guide X-rays having a large phase of a large amount of light with high efficiency.

  Conventionally, an element generally called a glass capillary has been used to converge X-rays. In this element, X-rays can be converged by advancing the inside of the capillary with total reflection of X-rays. Unlike the waveguide according to the present invention, this element cannot obtain a coherent X-ray because the tube diameter of the element is generally larger than that of the waveguide according to the present invention. This is different from the X-ray waveguide in the present invention.

  This waveguide confines and guides X-rays in the core by total reflection at the core / cladding interface. At this time, in addition to the periodic resonant waveguide mode, a mode in which X-rays are confined in the core by total reflection at the core / cladding interface regardless of the periodic structure (a mode generated also in a single-layer waveguide). Therefore, hereinafter, it will be referred to as “single-layer waveguide mode”). The single-layer waveguide mode often has a lower waveguide efficiency than the periodic resonance waveguide mode. However, although the efficiency is low, the X-ray guided by the latter mode is emitted simultaneously with the X-ray guided by the former mode. In this case, the phase of the X-ray is more disturbed than when only the periodic resonant waveguide mode is emitted. For example, this may cause a problem that an image becomes unclear when the X-ray is used for phase difference imaging.

  Since the X-ray optical element of the present invention has a mechanism for selectively transmitting X-rays emitted from the X-ray waveguide, it selectively transmits X-rays guided by the periodic resonance waveguide mode. be able to. As a result, there is no mechanism for selectively transmitting X-rays, and the phase of X-rays is compared with the case where both X-rays guided by the periodic resonant waveguide mode and the single-layer waveguide mode are emitted. It can be more complete. Therefore, the optical element of the present invention amplifies the characteristics of this waveguide such that the image becomes clear in imaging.

  Hereinafter, the X-ray optical element and the X-ray optical system of the present invention will be described in detail with reference to the drawings.

  A conceptual diagram of an X-ray optical element according to the present invention is shown in FIG.

  In FIG. 1, a core 1000 has a periodic structure including a plurality of substances 1080 and 1090 having different real parts of refractive index, and clads 1010 and 1020 confine X-rays in the core. The X-ray waveguide 1030 is composed of the core and the clad. The monochromatic X-ray 1040 incident on the X-ray waveguide is guided by being confined in the core by total reflection at the core / cladding interface. As a result, the light is emitted from the end of the waveguide. The optical path of the X-ray emitted at this time has a specific angle with respect to the waveguide for each waveguide mode in the far field. The optical element of the present invention has a mechanism 1060 that selectively transmits X-rays 1050 guided in a periodic resonance waveguide mode, the position of which is fixed with respect to the X-ray waveguide. Thus, by removing X-rays 1070 other than the X-rays guided by the periodic resonance waveguide mode, it is possible to easily emit X-rays having a highly uniform phase.

  Here, for the X-ray waveguide according to the present embodiment, the following items are used: (1) X-ray, (2) X-ray waveguide, (3) Core, (4) Cladding, (5) X-ray A mechanism for selectively transmitting a line will be described separately for (6) effect and (7) X-ray optical system.

(1) About X-rays In the present invention, X-rays are electromagnetic waves in a wavelength band in which the real part of the refractive index of a substance is 1 or less. Specifically, the X-ray in the present invention refers to an electromagnetic wave having a wavelength of 1 nm or more and a wavelength of 100 nm or less including extreme ultraviolet light (Extreme Ultra Violet (EUV) light). The present invention is for controlling an electromagnetic wave corresponding to the X-ray. In the present specification, the term “electromagnetic wave” may be used synonymously with the above X-ray.

  In addition, since the frequency of such short-wave electromagnetic waves is very high and the outermost electrons of the substance cannot respond, X-rays differ from the frequency band of electromagnetic waves (visible light and infrared rays) having wavelengths longer than those of ultraviolet light. It is known that the real part of the refractive index of a substance is smaller than 1. The refractive index n of a substance with respect to such X-rays is generally obtained by using a deviation δ from the real part 1 and β ′ of the imaginary part related to absorption as represented by the following formula (1). It is expressed as

δ is proportional to the electron density [rho _e substance, the real part of the larger material as the refractive index of the electron density is reduced. The real part n ′ of the refractive index is 1−δ. Furthermore, ρ _e is proportional to the atomic density ρ _a and the atomic number Z. Thus, the refractive index of a substance with respect to X-rays is represented by a complex number. In this specification, the real part is referred to as the real part of the refractive index or the real part of the refractive index, and the imaginary part is referred to as the imaginary part of the refractive index or the imaginary part of the refractive index. For example, X-rays have a maximum real part of refractive index when propagating in a vacuum, and have a maximum real part of refractive index of air for almost all substances that are not gases under general circumstances. In this specification, the term “substance” includes air and vacuum. Therefore, a mesostructure that is a mesostructure or a mesoporous material has a portion having a different refractive index composed of air or vacuum even when it is composed of a single material, and therefore is composed of a plurality of substances. To do.

(2) X-ray waveguide An X-ray waveguide that exhibits a periodic resonant waveguide mode is confined in a core having a periodic structure by confining the X-ray in the core having a periodic structure by total reflection at the interface between the core and the cladding. Forming and propagating X-rays. This waveguide is characterized in that the total reflection critical angle at the interface between the core and the clad is larger than the Bragg angle resulting from the periodicity of the periodic structure of the core. FIG. 2 shows a conceptual diagram of this X-ray waveguide. This X-ray waveguide has a form in which a core 2001 is sandwiched between a clad 2002 and a clad 2003. The core 2001 has a basic structure including a layer 2005 having a real part having a high refractive index and a layer 2006 having a real part having a low refractive index. Here, the periodic structure of the waveguide core used in the X-ray optical element of the present invention may be any one of the one-dimensional to three-dimensional periodic structures. Description will be made using a one-dimensional periodic structure such as a multilayer film. 2007 represents the total reflection critical angle at the interface between the clad and the core, 2008 represents the Bragg angle, and 2009 represents the total reflection critical angle at the material interface in the basic structure.

In FIG. 2, the total reflection critical angle θ _{c-total at} the interface between the clad and the core, the total reflection critical angle θ _c-multi at the interface of each layer forming the basic structure in the multilayer film, and the periodicity of the multilayer film An example of the Bragg angle θ _B is shown. In the present specification, these angles are expressed by assuming that the direction parallel to the plane of the film is 0 °. The advancing direction of the arrow X-ray in the figure is shown.

The total reflection critical angle θ from the direction parallel to the film surface, where n _{clad is} the real part of the refractive index of the material on the clad side and n _core is the real part of the refractive index of the material on the core side at the interface between the clad and the core _c-total (°) is expressed by the following formula (2) where n _clad <n _core.

It is represented by

When the period of the one-dimensional periodic structure of the core is d and the real part of the average refractive index of the periodic structure that is the core is n _avg , it is approximately as shown in the following formula (3) regardless of the presence or absence of multiple diffraction in the core. Bragg angle θ _B (°) is defined.

λ is the wavelength of X-rays.

  It is assumed that the physical property parameter of the substance constituting the X-ray waveguide, the structural parameter of the waveguide, and the wavelength of the X-ray are designed to satisfy the following formula (4).

As a result, the waveguide mode having an effective propagation angle near the Bragg angle due to the periodicity of the core which is a periodic structure can be always confined in the core by the clad and contribute to the propagation of X-rays. Here, in this specification, the effective propagation angle θ ′ (°) is expressed by the following equation (5) using the wave number vector (propagation constant) k _z in the propagation direction of the waveguide mode and the wave number vector k ₀ in vacuum. It shall be represented by Since k _z is constant at the interface of each layer due to the continuous condition, as shown in FIG. 3, the effective propagation angle θ ′ (°) is the propagation constant k _z of the fundamental wave of the waveguide mode and the wave number vector k _{0 in} vacuum. The angle at which the fundamental wave of the guided mode travels in a vacuum. Since this can be considered to roughly represent the propagation angle of the fundamental wave of the waveguide mode in the core, it will be used for the future explanation.

Here, the periodic structure that forms the core is assumed to be a multilayered film in which films of a plurality of substances having different real parts of the refractive index are periodically stacked. At this time, the total reflection critical angle due to the difference in the real part of the refractive index exists at the adjacent film interface. This is defined as θ _c-multi (°).

  When the critical angle for total reflection in the multilayer film is smaller than the Bragg angle due to the periodicity of the multilayer film as shown in the above formula (6), it is incident on the interface in the multilayer film at an angle greater than or equal to the Bragg angle. The X-rays that are generated do not cause total reflection, but cause partial reflection or refraction. Since the multilayer film is composed of a plurality of periodically laminated films having different real refractive indexes, there are a plurality of interfaces in the stacking direction, and X-rays inside the multilayer film are repeatedly reflected and refracted at these interfaces. It becomes. Such repeated reflection and refraction of X-rays within the multilayer film causes multiple interference. As a result, an X-ray having a condition capable of resonating with the periodic structure of the multilayer film, that is, a propagation mode that can exist inside the multilayer film is formed. As a result, a waveguide mode is formed in the core of the X-ray waveguide structure. It will be. This is referred to as a periodic resonance waveguide mode.

  Each of such periodic resonant waveguide modes has an effective propagation angle, and the effective propagation angle of the periodic resonant waveguide mode having the smallest effective propagation angle appears near the Bragg angle of the multilayer film. Since the periodic resonant waveguide mode is a mode that resonates with the periodicity of the periodic structure, it is referred to as a periodic resonant waveguide mode in this specification. This corresponds to a propagation mode that satisfies the lowest order band when the multi-layer film is considered as a one-dimensional photonic crystal with an infinite number of cycles. This propagation mode is confined by total reflection at the interface between the cladding and the core. Become.

  In an actual one-dimensional periodic structure, since the number of periods is finite, the photonic band structure deviates from the photonic band structure of the one-dimensional periodic structure with an infinite period. However, the waveguide mode increases as the number of periods increases. The characteristic approaches that on a photonic band with an infinite period. The Bragg reflection is caused by the effect of the photonic band gap due to periodicity, and the Bragg angle, which is the angle that gives the Bragg reflection, is slightly larger than the effective propagation angle of the periodic resonant waveguide mode.

  In the photonic band structure corresponding to the periodic structure, a waveguide mode that resonates with the periodic structure exists at the end of the photonic band gap. When the effective propagation angle of the waveguide mode is considered with the X-ray energy constant, the waveguide mode having a relatively small effective propagation angle among these waveguide modes is the lowest-order periodic resonant waveguide mode. . In the spatial distribution profile of the electric field intensity in the periodic resonant waveguide mode, the number of antinodes of the electric field intensity basically matches the number of periods of the multilayer film. The position of the antinode of the higher-order periodic resonant waveguide mode having an effective propagation angle corresponding to the higher-order Bragg angle is basically a natural number multiple of 2 or more of the number of periods.

  In a multilayer film having a finite number of periods, there may be a waveguide mode that propagates at an angle other than the effective propagation angle of the periodic resonance waveguide mode as described above. These are waveguide modes that exist when the entire multilayer film, which is not a periodic resonant waveguide mode, is considered as a uniform medium with the real part of the refractive index averaged. The influence of periodicity is small. On the other hand, in the periodic resonant waveguide mode realized by this X-ray waveguide configuration, as the number of periods of the periodic structure increases, the electric field concentrates at the center of the core, which is a multilayer film, and the seepage into the cladding decreases. Thus, the X-ray propagation loss is reduced. In addition, the envelope curve of the electric field intensity distribution has a shape biased toward the center of the core, and the loss due to the seepage into the clad is further reduced. Furthermore, the phase of the periodic resonant waveguide mode used in this X-ray waveguide is uniform in the direction with high periodicity, that is, in the direction perpendicular to the interface between the cladding and the core and perpendicular to the waveguide direction. Have coherence. Here, the fact that the waveguide modes are in phase not only corresponds to the fact that the phase difference of the electromagnetic field in the plane perpendicular to the waveguide direction is zero, but also corresponds to the spatial refractive index distribution of the periodic structure. This also means that the phase difference of the electromagnetic field periodically changes between −π and + π. In this periodic resonant waveguide mode, the phase of the electric field changes between −π and + π in the direction perpendicular to the waveguide direction at the same period as the period of the periodic structure.

(3) About the core In the present invention, the core has a periodic structure composed of a plurality of substances having different real parts of the refractive index. In the present invention, the plurality of substances having different real parts of refractive index are often two or more kinds of substances having different electron densities. The periodic structure may be a one-dimensional to three-dimensional periodic structure, but has a periodicity in a plane perpendicular to the X-ray waveguide direction. Such a periodic structure can also be produced by a conventional semiconductor process such as photolithography, electron beam lithography, etching process, lamination or bonding. For example, when the periodic structure is one-dimensional, this periodic structure can be configured as a periodic multilayer film. In this case, as a method of forming the multilayer film, there are alternating vapor deposition and sputtering.

Such a substance having a different real part of the refractive index forming the core may be a gas or a vacuum in addition to an inorganic or organic solid material. A combination of these substances is also preferably used. Examples of inorganic materials include boron, boron compounds, beryllium, carbon, nitrides, oxides, and phosphorus. Specific examples include Be, B, C, B ₄ C, BN, SiC, Si ₃ N ₄ , SiN, Al ₂ O ₃ , MgO, TiO ₂ , SiO ₂ , and P. By using an inorganic material as the material for forming the core, established processes such as conventional sputtering, vapor deposition, and crystal growth can be used, and a structure resistant to heat and external force can be obtained. Examples of organic substances include polymers and low molecular compounds. Propagation loss due to absorption of X-rays can be reduced by being an organic substance. A gas or vacuum is preferable because this loss can be further reduced.

  Further, as a material for forming the periodic structure, a material manufactured by a self-organized formation mechanism different from a normal semiconductor process may be used. An example of this is a periodic mesostructured film formed by self-assembly of a surfactant. The mesostructured film is preferably used for the periodic structure in the present invention. This is described below.

(3-1) About mesostructured membranes Porous materials are classified according to their pore diameters by IUPAC (International Union of Pure and Applied Chemistry), and porous materials with pore diameters of 2-50 nm are classified as mesoporous. The In recent years, research on this mesoporous material has been actively conducted, and it has become possible to obtain a structure in which mesopores with uniform diameters are regularly arranged by using a surfactant aggregate as a template.

In the present specification, the mesostructured film means the following.
(A) Mesoporous film (B) A mesoporous film in which pores are mainly filled with an organic compound (C) Mesostructured film having a lamellar structure A detailed description will be given below.

(A) About mesoporous membrane The porous material has a pore diameter of 2 to 50 nm and the material of the wall is not particularly limited. Examples thereof include manufacturability, refractive index as well as molecules or vacancies serving as templates. From the viewpoint of forming a periodic structure composed of substances whose real parts are different, oxides are mentioned. Examples of the oxide include silicon oxide, tin oxide, zirconia, titanium oxide, niobium oxide, tantalum oxide, aluminum oxide, tungsten oxide, hafnium oxide, and zinc oxide. These substances have, for example, a real part of refractive index of 0.999997 or less for X-rays of 10 keV, for example, organic substances (having a real part of refractive index of about 0.999998) described later, air (same as above) , Having a real part of refractive index of approximately 1) and a periodic structure, it is possible to form a periodic structure made of materials having different real parts of refractive index. The above oxide may contain an organic component in its skeleton. The surface of the wall portion may be modified as necessary. For example, hydrophobic molecules may be modified to suppress water adsorption.

  The method for preparing the mesoporous film is not particularly limited, but for example, it can be prepared by the following method. An inorganic oxide precursor is added to a solution of an amphiphile in which the aggregate functions as a template, a film is formed, and an inorganic oxide formation reaction proceeds. Thereafter, the template molecule is removed to obtain a porous material.

  The amphiphile is not particularly limited, but a surfactant is suitable. Examples of the surfactant molecule include ionic and nonionic surfactants. Examples of the ionic surfactant include a halide salt of trimethylalkylammonium ion. Examples of the chain length of the alkyl chain include 10 to 22 carbon atoms. As an example of a nonionic surfactant, what contains polyethyleneglycol as a hydrophilic group can be mentioned. Specific examples of the surfactant containing polyethylene glycol as a hydrophilic group include polyethylene glycol alkyl ether and polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymers. Examples of the chain length of this alkyl chain of the polyethylene glycol alkyl ether include 10 to 22 carbon atoms, and examples of the polyethylene glycol repeating number include 2 to 50. It is possible to change the structural period by changing the hydrophobic group and the hydrophilic group. In general, it is possible to enlarge the pore diameter by increasing the hydrophobic group and hydrophilic group. In addition to the surfactant, an additive for adjusting the structural period may be added. Examples of the additive for adjusting the structure period include hydrophobic substances. Examples of the hydrophobic substance include alkanes and aromatic compounds not containing a hydrophilic group, and specific examples thereof include octane.

  Examples of inorganic oxide precursors include silicon and metal element alkoxides and chlorides. More specific examples include alkoxides and chlorides of Si, Zr, Ti, Nb, Al, Zn, and Sn. Examples of the alkoxide include methoxide, ethoxide, propoxide, or one in which a part thereof is substituted with an alkyl group.

  Examples of the film forming method include a dip coating method, a spin coating method, and a hydrothermal synthesis method.

  Examples of the template molecule removal method include baking, extraction, ultraviolet irradiation, and ozone treatment.

(B) About mesoporous film in which pores are mainly filled with an organic compound As the material of the wall, the same materials as those described in the section (A) can be used. The substance filling the pores is not particularly limited as long as it is mainly composed of an organic compound. The meaning of “main” means 50% or more by volume ratio. Examples of the organic compound include a surfactant and a material in which a site having a function of forming a molecular assembly is bonded to a material forming a wall or a precursor of a material forming a wall. Examples of this surfactant include the surfactants described in the section (A). Examples of a material in which a part having a function of forming a molecular assembly forms a wall or a material bonded to a precursor of a material that forms a wall include an alkoxysilane having an alkyl group and an alkyl group. The oligosiloxane compound which has can be mentioned. Examples of the chain length of the alkyl chain include 10 to 22 carbon atoms.

  The inside of the hole may contain water, an organic solvent, a salt, or the like as necessary or as a result of a material to be used or a process. Examples of the organic solvent include alcohol, ether and hydrocarbon.

  The method for preparing the mesoporous membrane whose pores are mainly filled with an organic compound is not particularly limited. For example, the steps prior to the removal of the template in the method for preparing the mesoporous membrane described in the section (A) are performed. Can be mentioned.

(C) Mesostructured film having a lamellar structure The mesostructured film of the present invention includes a mesostructured film having a lamellar structure in addition to (A) and (B). This lamellar structure refers to a lamellar structure composed of the material for the wall portion described in (B) and the substance that fills the holes described in (B). These two kinds of materials (substances) may be bonded by chemical bonds as necessary in order to obtain desired properties. An example of this bonded compound is trialkoxyalkylsilane.

(4) Cladding The X-ray waveguide of the present invention guides the X-ray by confining the X-ray in the core by total reflection at the cladding. In the X-ray region, a substance having a higher electron density has a smaller real part of the refractive index. Therefore, a specific example of a material used for the clad is a metal having a high density. More specifically, a simple substance of Os, Ir, Pt, Au, W, Ta, Hg, Ru, Rh, Pd, Pb, and Mo, or a material containing these elements can be used. A clad using such a material can be formed by sputtering, vapor deposition, or the like. Although the thickness of this clad varies depending on the material, it is required to be thick enough to sufficiently confine X-rays in the core and thin from the viewpoint of cost and manufacturing. Examples of the thickness include a value of about 1 nm to 300 nm, preferably about 1 nm to 50 nm. The clad is preferably formed with a film thickness distribution in the X-ray waveguide. For example, for the purpose of positively incident from the cladding surface, a thin film is formed in the incident region to improve introduction efficiency, while in other regions, a thick film is formed to enhance the X-ray confinement effect. Is preferably performed.

(5) Mechanism for selectively transmitting X-rays The X-ray optical element of the present invention transmits X-rays emitted from an X-ray waveguide that guides X-rays in a periodic resonant waveguide mode. In order to selectively transmit the processed component, a mechanism for limiting the emission angle is provided.

(5-1) Style and positional relationship Any mechanism may be used as long as the mechanism for limiting the emission angle is a mechanism for limiting the emission angle in order to selectively transmit desired X-rays. Even if it exists, it can be used. For example, a slit, pinhole, collimator-like mechanism can be raised. On the other hand, the mechanism for limiting the emission angle is also a mechanism for blocking X-rays that are not emitted in a desired angular direction. Therefore, as a constituent material, a material used for blocking X-rays can be used. An example of this material is metal.

The mechanism for selectively transmitting X-rays according to the present invention shields, in the far field, X-rays guided by a mode other than the periodic resonance waveguide mode among X-rays emitted from the X-ray waveguide. To do. For this reason, this mechanism is installed in the Fraunhofer region with respect to the exit end of the waveguide. This region is a region away from D ² / λ from the output end, where D is the thickness of the core of the waveguide and λ is the wavelength of the X-ray. On the other hand, if this mechanism is too far from the exit end, it is not preferable because the cross-sectional area of the X-ray beam is enlarged (the resulting spot density is reduced) and the intensity is attenuated. Further, from the viewpoint of preventing the device from becoming large, it is preferable that this distance is small. For this reason, the upper limit of the distance from the emitting end to this mechanism is 30 cm or less, preferably 1 cm or less. That is, when the thickness of the core in the direction perpendicular to the core-cladding interface is D, the distance between the exit end of the X-ray waveguide and the mechanism that selectively transmits X-rays is D ² / λ or more and 1 cm or less. Preferably there is.

(5-2) Angle X-rays guided in the X-ray waveguide by the periodic resonance waveguide mode are emitted at a specific angle with respect to the waveguide. This angle is determined mainly by the period of the periodic structure constituting the waveguide, the refractive index of the substance constituting the periodic structure, and the number of periods. Roughly speaking, it can be described as being near the Bragg angle of the periodic structure constituting the waveguide and smaller than that.

  This waveguide has a structure in which X-rays are confined and guided in the core by total reflection at the core / cladding interface. Therefore, in addition to the periodic resonant waveguide mode, there may exist a mode that guides by confining X-rays in the core by total reflection at the core / cladding interface regardless of the periodic structure. This waveguide mode is a mode (single layer waveguide mode) similar to the waveguide mode of the single layer waveguide. The single-layer waveguide mode often has a lower waveguide efficiency than the periodic resonance waveguide mode. However, although the efficiency is low, it is possible that the X-ray guided by this mode is emitted simultaneously with the X-ray guided by the periodic resonance waveguide mode. The waveguide efficiency of X-rays transmitted through the single-layer waveguide mode is greatly reduced as the mode order increases from a low-order mode to a high-order. Therefore, in order to obtain an X-ray with the same phase, which is a feature of the X-ray waveguide that guides the X-rays by this periodic resonance waveguide mode, among the X-rays transmitted by the single-layer waveguide mode, It is more important to shield the transmitted X-rays by different modes. (On the contrary, if the X-ray is transmitted by a higher-order mode, the influence is relatively small even if it is emitted simultaneously with the X-ray propagated by the periodic resonant waveguide mode.) The emission angle of the X-rays emitted by increases with the order. A mode in which the order coincides with ((the number of periods of the periodic structure) −1) is a periodic resonance waveguide mode. For this reason, in order to obtain X-rays having the same phase, it is effective to shield X-rays having an emission angle smaller than that of the periodic resonance mode.

  Of course, the X-ray angle region transmitted by the X-ray optical element of the present invention corresponds only to the X-rays transmitted by the periodic resonance waveguide mode if allowed from the technical and cost viewpoints. An angular region is most effective. On the other hand, severe restrictions on the emission angle reduce the intensity of X-rays emitted from the optical element. Therefore, an angle range suitable for the purpose of use is selected. Considering these, the preferable angle condition of the X-ray selectively transmitted by the X-ray optical element can be described as follows.

  When the number of periods of the structure that resonates with the periodic resonant waveguide mode is n, 130 (n−) is greater than the emission angle of the single-layer waveguide mode having an integer order closest to 70 (n−1) / 100. 1) Being equal to or smaller than the emission angle of the single-layer waveguide mode having an integer order closest to / 100. More preferably, the single-layer waveguide having an integer order closest to 110 (n-1) / 100 is equal to or greater than the emission angle of the single-layer waveguide mode having an integer order closest to 90 (n-1) / 100. It must be below the wave mode exit angle.

  As a method for separating and confirming the single-layer waveguide mode around the periodic resonant waveguide mode, the following method can be cited. The incident angle dependence of the transmission intensity of the guided X-ray when an X-ray beam having a small divergence angle is incident on the waveguide is measured. FIG. 5 shows a schematic diagram (peripheral angle of the periodic resonant waveguide mode) of the incident angle dependence of the transmission intensity of X-rays emitted from the X-ray waveguide. In the figure, a peak with a reference sign is an X-ray guided by a single-layer waveguide mode, and among them, a peak indicated by a sign of n-1 is an X-ray guided by a periodic resonant waveguide mode. It is. The emission angle of the X-ray guided by the single-layer waveguide mode around the periodic resonant waveguide mode is an X-ray that is strongly guided when the X-ray is incident at an incident angle at which each mode gives a peak. Can be determined by observing the emission angle.

  Moreover, the preferable angle condition of the X-ray selectively transmitted by the X-ray optical element is set as follows when the Bragg angle of the periodic structure constituting the waveguide is used.

When the number of periods of the structure that resonates in the periodic resonance waveguide mode is n and the Bragg angle is θ _B , it is 0.7 × θ _B × (n−1) / n or more and 1.3 × θ _B × ( It is preferable that it is n-1) / n or less. Further, it is more preferably 0.9 × θ _B × (n−1) / n or more and 1.1 × θ _B × (n−1) / n or less.

(5-3) About fixed position In the X-ray optical element of the present invention, the mechanism for selectively transmitting the X-ray through the angle is a mechanism whose position is fixed with respect to the X-ray waveguide. . The reason is described below. In the waveguide used for the X-ray optical element of the present invention, the exit angle region of the X-ray guided by the periodic resonance waveguide mode is very narrow. For this reason, when considering the removal of X-rays guided by modes other than this mode, the following method can be considered. 1. It is removed using a large optical system with a longer distance between the waveguide and its removal mechanism. 2. A small optical system is precisely controlled and removed. In the former case, it is against the policy of downsizing the optical system, which is the original motivation for introducing the X-ray waveguide. Further, when the distance is increased, the density of X-rays is inversely proportional to the square of the distance. Further, in the case of long-wavelength X-rays, the strength is reduced by substances such as air. In the case of 2, the precise angle setting requires a long time and a large tool. In either case of the former or the latter, it is necessary to adjust each time the waveguide is moved and installed.

  On the other hand, the position of the X-ray optical element of the present invention is fixed with respect to the waveguide, which is set in advance with respect to the wavelength peculiar to the periodic resonance waveguide mode guided through the waveguide. By using the mechanism, X-rays with high intensity and high phase alignment can be given while maintaining the miniaturization of the optical system and the ease of installation. For this reason, monochromatic X-rays are used as the X-rays used in the X-ray optical element of the present invention.

  In the periodic resonant waveguide mode used in the X-ray optical element of the present invention, the emission angle changes depending on the wavelength of the guided X-ray, as does the Bragg angle. In order to cope with this, the X-ray optical element of the present invention may include a mechanism that moves a mechanism that selectively transmits X-rays whose positions are fixed as needed.

(6) Effect The X-ray optical element of the present invention has an X-ray waveguide that guides X-rays in the periodic resonance waveguide mode and a mechanism that selectively transmits X-rays guided in the waveguide mode. And the mechanism is fixed in position relative to the waveguide, so that X-rays other than the X-rays guided by the periodic resonant waveguide mode can be removed, and the X-rays can be easily and highly aligned in phase. Can be emitted.

(7) X-ray optical system The X-ray optical system of the present invention has an X-ray source, an X-ray waveguide, and a mechanism that selectively transmits X-rays emitted from the X-ray waveguide. The X-ray source emits monochromatic X-rays having a wavelength λ. As the X-ray waveguide, the above X-ray waveguide can be used. The mechanism that selectively transmits X-rays is a mechanism that selectively transmits the X-ray emission angle. The distance between the emission end of the X-ray waveguide and the mechanism that selectively transmits the X-ray is preferably D ² / λ or more and 1 cm or less.

  The present invention will be described in more detail with reference to the following examples. However, the method of the present invention is not limited to these examples.

Example 1
(1-1) Preparation of Waveguide FIG. 4 is a diagram showing an X-ray waveguide used for the X-ray optical element of the present invention. A lower clad 4000 made of W having a thickness of 20 nanometers, a multi-layer film 4020 having a one-dimensional periodic structure, and an upper clad 4010 made of W having a thickness of 20 nm were formed on a Si substrate 4030 by sputtering. In addition, a part of the upper clad has a thickness of 2 nm for X-ray waveguide mode separation measurement. In this multilayer film having a periodic structure, a film having a thickness of 3 nm made of boron carbide (B ₄ C) and a film having a thickness of 12 nm made of aluminum oxide (Al ₂ O ₃ ) are alternately laminated. It consists of a periodic structure. The number of periods is 100, and the period is 15 nanometers.

  An 8 keV parallel X-ray beam is made incident on the region where the thickness of the upper clad of the waveguide is 2 nm by prism coupling (oblique incidence on the upper portion of the waveguide), and the incident angle of the waveguide X-ray intensity. Measure dependencies. Thereby, the emission angle of the X-ray guided by the single-layer waveguide mode and the periodic resonance waveguide mode is confirmed. The Bragg angle of the periodic structure constituting this waveguide is confirmed to be 0.369 degrees by X-ray diffraction measurement.

(1-2) Formation of X-ray optical element A slit having a predetermined width is prepared on a silicon substrate using a semiconductor process. The slit is held at a predetermined angle at a distance of 1 cm from the emission end of the waveguide while monitoring the waveguide X-ray, and the position is fixed to the waveguide and bonded, as shown in FIG. An X-ray optical element is formed. The selective transmission angle at this time (the range of transmissive θ in FIG. 1) is (a) 0.256 degrees (corresponding to the emission angle of the 69th mode) or more and 0.475 degrees (129th order) or less. (B) 0.329 degrees (89th order) or more and 0.402 degrees (109th order) or less, (c) 0.364 degrees or more and 0.367 degrees or less (selecting only the periodic resonant waveguide mode).

(1-3) Measurement of effect 10 keV X-rays were incident on the formed X-ray optical element by front coupling, and waveguide X-rays were measured. Table 1 shows the relative intensity of all X-rays guided through the waveguide, and the ratio of the periodic resonant waveguide mode included in the all waveguide X-rays (converted from the emission angle, the same applies hereinafter).

  The X-ray optical element of the present invention has a mechanism that selectively transmits X-rays guided in the periodic resonant waveguide mode, and the position of the mechanism is fixed with respect to the waveguide. Features. This measurement result shows that by using the X-ray optical element of the present invention having this feature, it is possible to obtain X-rays having a uniform phase with a size of about several centimeters.

  Moreover, it is shown that the preferable conditions of the selected emission angle of the X-ray at that time are the angle conditions described in the section (5-2) for carrying out the invention.

Example 2
(2-1) Formation of X-ray optical element A pinhole is formed in a stainless steel plate. The pinhole is held at a predetermined angle at a distance of 1 cm from the emission end of the X-ray waveguide described in Example 1 while monitoring the waveguide X-ray, and is positioned relative to the waveguide and the waveguide. Is fixed to form the X-ray optical element shown in FIG. At this time, the selective transmission angle (the range of θ that can be transmitted in FIG. 1) is 0.329 degrees (corresponding to the emission angle of the 89th mode) or more and 0.402 degrees (109th order) or less.

(2-2) Measurement of effect A 10 keV X-ray was incident on the formed X-ray optical element by front coupling, and a waveguide X-ray was measured. Table 2 shows the relative intensity of all the X-rays guided through the waveguide and the ratio of the periodic resonant waveguide mode included in the all guided X-rays.

  The X-ray optical element of the present invention has a mechanism that selectively transmits X-rays guided in the periodic resonant waveguide mode, and the position of the mechanism is fixed with respect to the waveguide. Features. This measurement result shows that by using the X-ray optical element of the present invention having this feature, it is possible to obtain X-rays having a uniform phase with a size of about several centimeters.

Example 3
In this example, an X-ray optical element using a waveguide using a mesostructured film as a core will be described.

(3-1) Preparation of Waveguide Preparation of an X-ray waveguide having the configuration of FIG. 4 will be described. The X-ray waveguide of this embodiment is formed on a Si substrate 4030 so that clads 4000 and 4010 made of W (tungsten) sandwich the core 4020 therebetween. The core 4020 is a silicon oxide mesostructured film. In this mesostructured film, holes made of an organic substance are two-dimensionally arranged to form a periodic structure in the film thickness direction.

(3-1-1) Formation of cladding (4000)
A clad 4000 made of W (tungsten) is formed on a Si substrate to a thickness of about 20 nanometers by sputtering.

(3-1-2) Method for producing silicon oxide mesostructured film (3-1-2-1) Preparation of precursor solution for mesostructured film Silicon oxide mesostructured film having a 2D hexagonal structure is formed by dip coating. It is prepared with. The precursor solution of the mesostructure is prepared by adding an ethanol solution of a block polymer to a solution obtained by adding ethanol, 0.01M hydrochloric acid, and tetraethoxysilane and mixing for 20 minutes, and stirring for 3 hours. As a block polymer, ethylene oxide (20) propylene oxide (70) ethylene oxide (20) (hereinafter referred to as EO (20) PO (70) EO (20) (in parentheses are the number of repetitions of each block)) Can be used. It is also possible to use methanol, propanol, 1,4-dioxane, tetrahydrofuran, or acetonitrile instead of ethanol. The mixing ratio (molar ratio) is tetraethoxysilane: 1.0, hydrochloric acid: 0.0011, ethanol: 5.2, block polymer: 0.0096, and ethanol: 3.5. The solution is appropriately diluted and used for the purpose of adjusting the film thickness.

(3-1-2-2) Formation of Mesostructured Film A dip coating is performed on the cleaned substrate using a dip coating apparatus at a lifting speed of 0.5 mms ⁻¹ . After film formation, the film is held in a constant temperature and humidity chamber at 25 ° C. and a relative humidity of 40% for 2 weeks and at 80 ° C. for 24 hours.

(3-1-2-3) Evaluation The prepared mesostructured film is subjected to X-ray diffraction analysis using the Bragg-Brentano configuration. As a result, it is confirmed that this mesostructured film has high ordering in the normal direction of the substrate surface, and the interval between the surfaces, that is, the period in the confinement direction is 10.2 nm. Its film thickness is 480 nanometers.

(3-1-3) Formation of Cladding (4010) W cladding 4010 is formed on the buffer layer. This clad is formed with a thickness of about 20 nanometers by sputtering. In addition, a part of the upper clad has a thickness of 2 nm for X-ray waveguide mode separation measurement.

  An 8 keV parallel X-ray beam is made incident on the region where the thickness of the upper clad of the waveguide is 2 nm by prism coupling (oblique incidence on the upper portion of the waveguide), and the incident angle of the waveguide X-ray intensity. Measure dependencies. Thereby, the emission angle of the X-ray guided by the single-layer waveguide mode and the periodic resonance waveguide mode is confirmed. The Bragg angle of the periodic structure constituting this waveguide is confirmed to be 0.485 degrees by X-ray diffraction measurement.

(3-2) Formation of X-ray optical element A semiconductor process is used to prepare a slit having a predetermined width on a silicon substrate. The slit is held at a predetermined angle at a distance of 1 cm from the exit end of the waveguide while monitoring the waveguide X-ray, and the position is fixed with respect to the waveguide using a fixture, and the X-ray shown in FIG. An optical element is formed. The selective transmission angle at this time (the range of θ that can be transmitted in FIG. 1) is (a) 0.332 degrees (corresponding to the emission angle of the 32nd mode) or more and 0.617 degrees (60th order), (B) 0.427 degrees (41st order) or more and 0.522 degrees (51st order) or less, (c) 0.469 degrees or more and 0.485 degrees or less (selecting only the periodic resonant waveguide mode).

(3-3) Measurement of effect 10 keV X-rays were incident on the formed X-ray optical element by front coupling, and waveguide X-rays were measured. Table 3 shows the relative intensities of all the X-rays guided through the waveguide and the ratio of the periodic resonance waveguide modes included in the all the guided X-rays.

  The X-ray optical element of the present invention has a mechanism that selectively transmits X-rays guided in a periodic resonance waveguide mode through an X-ray waveguide having a mesostructure film as a core, and the mechanism is The position is fixed with respect to the waveguide. This measurement result shows that by using the X-ray optical element of the present invention having this feature, it is possible to obtain X-rays having a uniform phase with a size of about several centimeters.

  Moreover, it is shown that the preferable conditions of the selected emission angle of the X-ray at that time are the angle conditions described in the section (5-2) for carrying out the invention.

  The X-ray waveguide of the present invention can be used for components used in an X-ray optical system in imaging, exposure, analysis and the like using X-rays.

1000 core 1010, 1020 clad 1030 X-ray waveguide 1060 mechanism for selectively transmitting X-ray 1080, 1090 material 2001 core 2002, 2003 clad 2004 basic structure 2005, 2006 material 4000, 4010 clad 4020 core

Claims (8)

An X-ray optical element having an X-ray waveguide and a mechanism for selectively transmitting X-rays emitted from the X-ray waveguide,
The X-ray waveguide has a core for guiding X-rays, and a clad for confining the X-rays in the core,
The core has a periodic structure composed of a plurality of substances having different real parts of refractive index,
The X-ray total reflection critical angle at the interface between the cladding and the core is larger than the Bragg angle due to the periodicity of the core,
The X-ray optical element, wherein the mechanism for selectively transmitting the X-ray selectively transmits the X-ray emitted from the X-ray waveguide at a predetermined emission angle.   2. The X-ray waveguide according to claim 1, wherein a Bragg angle resulting from the periodicity of the core is larger than a total reflection critical angle between a plurality of substances forming the periodic structure.   The X-ray waveguide according to claim 1, wherein the core is a periodic multilayer film.   The X-ray waveguide according to claim 1, wherein the core is a periodic mesostructure.   The X-ray waveguide according to claim 1, wherein the core is a mesoporous film having periodicity.   The X-ray optical element according to claim 1, wherein the mechanism for selectively transmitting X-rays is fixed in position with respect to the X-ray waveguide. In an X-ray optical system having an X-ray source, an X-ray waveguide, and a mechanism for selectively transmitting X-rays emitted from the X-ray waveguide,
The X-ray source emits monochromatic X-rays with a wavelength λ,
The X-ray waveguide has a core for guiding X-rays, and a clad for confining the X-rays in the core,
The core has a periodic structure composed of a plurality of substances having different real parts of refractive index,
The X-ray total reflection critical angle at the interface between the cladding and the core is larger than the Bragg angle due to the periodicity of the core,
The X-ray optical system characterized in that the mechanism that selectively transmits X-rays is a mechanism that selectively transmits an X-ray emission angle. When the thickness of the core in the direction perpendicular to the core-cladding interface is D, the distance between the emission end of the X-ray waveguide and the mechanism that selectively transmits the X-ray is D ² / λ or more and 1 cm. The X-ray optical system according to claim 7, wherein:

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