JP2013057520A - Phase type diffraction grating, manufacturing method of phase type diffraction grating, and x-ray imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase type diffraction grating capable of further reducing surface roughness, a manufacturing method thereof, and an x-ray imaging device using the same.SOLUTION: A phase type diffraction grating comprises a plurality of first optical distance parts 12a which have a first thickness corresponding to a first optical distance and are arranged according to a predetermined rule, and second optical distance parts 12b which have a second thickness corresponding to a second optical distance to cause a predetermined phase difference for an X-ray transmitted through the plurality of first optical distance parts and are arranged corresponding to the plurality of first optical distance parts 12a, between an incidence plane and an emission plane. The second optical distance part 12b includes a plurality of optical elements. The optical element of the outermost exposed optical element part 12b2 which is exposed at the outermost among the plurality of optical elements has a thickness with an allowable surface roughness under specifications. The first optical distance part 12a includes one optical element having a refractive index which is higher than each of the refractive indices of the plurality of optical elements of the second optical distance part 12b.

Description

  The present invention relates to a phase type diffraction grating, and more particularly to a phase type diffraction grating capable of further reducing the roughness of the surface. And this invention relates to the manufacturing method of the phase type diffraction grating which manufactures this phase type diffraction grating, and the X-ray imaging device using this phase type diffraction grating.

  A diffraction grating is used as an optical system of various apparatuses as a spectroscopic element having a large number of parallel periodic structures, and in recent years, application to an X-ray imaging apparatus is also progressing. The diffraction gratings are classified into transmission diffraction gratings and reflection diffraction gratings when classified by the diffraction method. Furthermore, the transmission diffraction gratings periodically arrange light absorbing portions on a substrate that transmits light. There are an amplitude type diffraction grating (absorption type diffraction grating) and a phase type diffraction grating in which portions for changing the phase of light are periodically arranged on a substrate that transmits light. Here, absorption means that more than 50% of light is absorbed by the diffraction grating, and transmission means that more than 50% of light passes through the diffraction grating.

  The phase type diffraction grating includes, for example, a plurality of first optical distance portions having a first refractive index and a first thickness corresponding to the first optical distance and extending linearly in one direction, and the first optical distance portion. A plurality of second lines linearly extending in the one direction having a second refractive index and a second thickness corresponding to a second optical distance that causes a predetermined phase difference with respect to a wave that has passed through the optical distance portion. Two optical distance portions are provided between the entrance surface and the exit surface, and the plurality of first optical distance portions and the plurality of second optical distance portions are alternately arranged in parallel. When there are a plurality of media in the optical path, the optical distance in the optical path is the sum of the optical distances in the respective media. Such a phase type diffraction grating is disclosed in Patent Document 1, for example.

  The phase grating disclosed in Patent Document 1 is formed by opening a plurality of gaps that are rectangular structures in a silicon wafer by dry etching. The gap is provided. The phase grating disclosed in Patent Document 1 further matches the intensity (amplitude) of the X-ray that has passed through the protrusion and the X-ray that has passed through the gap, and extinguishes the 0th-order diffracted light. Filling materials are further disposed at the bottoms of the plurality of gaps (paragraph [0032], [0049] and FIG. 4). According to the paragraph [0050] of Patent Document 1, the phase grating having such a structure is obtained by sputtering the filler material onto the grating and then chemically-mechanically polishing the surface of the grating, that is, the end of the protrusion. Manufactured by doing.

  On the other hand, such a phase type diffraction grating is used for an X-ray interferometer, for example, a Talbot interferometer, as disclosed in Patent Document 1 or Patent Document 2, and this Talbot interferometer is used. It is used in an X-ray imaging apparatus using a so-called phase contrast method.

FIG. 16 is a diagram illustrating a schematic configuration of an X-ray imaging apparatus in the related art. FIG. 16A is an explanatory diagram showing a schematic configuration of the X-ray imaging apparatus described in Patent Document 2, and FIG. 16B is a top view thereof. In FIG. 16, an X-ray imaging apparatus 1000 described in Patent Document 2 includes an X-ray source 1001, a phase-type diffraction grating 1002 that diffracts X-rays emitted from the X-ray source 1001, and a phase-type diffraction grating 1002. An amplitude type diffraction grating 1003 that forms an image contrast by diffracting the diffracted X-rays, and an X-ray image detector 1004 that detects X-rays in which an image contrast is generated by the amplitude type diffraction grating 1003 are provided. The diffraction grating 1002 and the amplitude type diffraction grating 1003 are set to the conditions constituting the Talbot interferometer. This condition is expressed by the following equations 1 and 2. Formula 2 assumes that the diffraction grating 1002 disposed on the X-ray source 1001 side is a phase type diffraction grating.
l = λ / (a / (L + Z1 + Z2)) (Formula 1)
Z1 = (m + 1/2) × (d ² / λ) (Formula 2)
Here, l is a coherent distance, λ is an X-ray wavelength (usually a center wavelength), and a is an aperture diameter of the X-ray source 1001 in a direction substantially perpendicular to the diffraction member of the diffraction grating. Yes, L is the distance from the X-ray source 1001 to the phase type diffraction grating 1002, Z1 is the distance from the phase type diffraction grating 1002 to the amplitude type diffraction grating 1003, and Z2 is from the amplitude type diffraction grating 1003. The distance to the X-ray image detector 1004, m is an integer, and d is the period of the diffractive member (the period of the diffraction grating, the grating constant, the distance between the centers of adjacent diffractive members).

  In the X-ray imaging apparatus 1000 having such a configuration, the subject 1010 is disposed between the X-ray source 1001 and the phase-type diffraction grating 1002, and X-rays are irradiated from the X-ray source 1001 toward the phase-type diffraction grating 1002. Is done. This irradiated X-ray produces a Talbot effect at the phase type diffraction grating 1002 to form a Talbot image. This Talbot image is acted on by the amplitude type diffraction grating 1003 to form an image contrast of moire fringes. This image contrast is detected by the X-ray image detector 1004. The moire fringes are modulated by the subject 1010, and the amount of modulation is proportional to the angle at which the X-ray is bent by the refraction effect of the subject 1010. For this reason, the subject 1010 and its internal structure can be detected by analyzing the moire fringes.

  Here, the Talbot effect means that when light enters the diffraction grating, the same image as the diffraction grating (self-image of the diffraction grating) is formed at a certain distance. It is called a distance L, and this self-image is called a Talbot image. When the diffraction grating is a phase type diffraction grating, the Talbot distance L is Z1 represented by the above formula 2 (L = Z1). In the Talbot image, an inverted image appears at an odd multiple of L (= (2m + 1) L, m is an integer), and a normal image appears at an even multiple of L (= 2 mL).

JP 2007-203064 A International Publication No. 2004/058070 Pamphlet

  By the way, if the surface of the X-ray incident on the phase-type diffraction grating or the X-ray emitted from the phase-type diffraction grating is rough, the X-ray is scattered by the rough surface. As a result, the performance of the phase type diffraction grating according to the design value cannot be achieved. In the said patent document 1, there is no mention of this point and it is not considered.

  For example, when the first and second optical distance portions are formed of metal and air, and a π / 2 type phase type diffraction grating applied to 28 keV (wavelength 0.04 nm) X-rays is designed. In addition, when gold having a relatively large phase change is used as the metal, the thickness of the gold is 2.7 μm. An electroforming method (wet electroplating method) is suitable as a method for forming a relatively thick gold as such a film (layer). However, when gold having such a thickness is formed by an electroforming method, The surface becomes rough.

  Therefore, in order to avoid this, in the case where a silicon substrate whose surface can be processed relatively smoothly is used instead of the metal, in the above example, gold, it is applied to the same conditions as described above, that is, to 28 keV X-rays. In the π / 2 type phase diffraction grating, the thickness of silicon is 18 μm. In a phase type diffraction grating having such a thickness grating, the X-rays radiated from the X-ray source 1001 spread radially because the X-ray source 1001 is generally a point light source. In the central region, X-rays are incident substantially parallel to the grating and function as a Talbot interferometer, but in each region on both sides of the phase-type diffraction grating 1002, X-rays are incident obliquely with respect to the grating. The function of the phase type diffraction grating cannot be properly exhibited, and the Talbot interferometer does not function properly.

  In other words, the method of manufacturing a phase-type diffraction grating using a relatively heavy element such as gold, which changes the phase relatively large, is a thin-type phase diffraction grating, so that the function of the phase-type diffraction grating deteriorates due to oblique incidence. Can be reduced. However, when gold having a thickness suitable for the phase type diffraction grating is formed, the surface may become rough.

  On the other hand, a method of manufacturing a phase-type diffraction grating using a silicon substrate or a quartz substrate capable of processing a relatively smooth surface can reduce the roughness of the surface, but results in a thick phase-type diffraction grating. For this reason, functional deterioration of the phase type diffraction grating due to oblique incidence occurs.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a phase type diffraction grating capable of further reducing the surface roughness. And this invention is providing the manufacturing method of the phase type diffraction grating which manufactures this phase type diffraction grating, and the X-ray imaging device using this phase type diffraction grating.

  As a result of various studies, the present inventor has found that the above object is achieved by the present invention described below. That is, the phase type diffraction grating according to an aspect of the present invention includes a plurality of first optical distance portions having a first thickness corresponding to the first optical distance and arranged according to a predetermined rule, The X-rays that have passed through one optical distance portion have a second thickness corresponding to a second optical distance that causes a predetermined phase difference, and are arranged according to the plurality of first optical distance portions. A second optical distance portion between the entrance surface and the exit surface, wherein the first optical distance portion is composed of one optical element, and the second optical distance portion includes a plurality of optical distance portions. An optical element, and one optical element of the first optical distance portion has a refractive index higher than each refractive index of the plurality of optical elements of the second optical distance portion, Optical requirement of outermost exposure that is exposed to the outside among a plurality of optical elements in two optical distance portions It is characterized by a thickness having a surface roughness allowed by the specification. Preferably, in the phase type diffraction grating, a sum of thicknesses of the plurality of optical elements is equal to the second thickness of the second optical distance portion, and the plurality of optical elements The sum of the product of the refractive index and the thickness required for each of the is equal to the second optical distance.

  In the phase type diffraction grating having such a configuration, the outermost exposed optical element of the plurality of optical elements in the second optical distance portion has the surface roughness permitted by the specifications. Formed with thickness. For this reason, the phase type diffraction grating having such a configuration can reduce the surface roughness.

  The optical element acts on the optical distance of the electromagnetic wave propagating through the medium, such as a substance, air, and vacuum. The optical distance is given by the product of its refractive index and its thickness (length) with respect to the wavelength of the incident electromagnetic wave.

  In another aspect, in the above-described phase type diffraction grating, one optical element of the first optical distance portion is a gas or a vacuum, and the outermost portion of the second optical distance portion is The exposed optical element is a material having a refractive index lower than the refractive index of the remaining optical elements excluding the outermost exposed optical element in the plurality of optical elements in the second optical distance portion.

  In the phase type diffraction grating having such a configuration, the second optical distance portion is composed of a plurality of optical elements, and the outermost exposed optical element of the second optical distance portion is the second optical distance portion. In the plurality of optical elements, a material having a refractive index lower than the refractive index of the remaining optical elements excluding the outermost exposed optical element is formed. Therefore, in the phase type diffraction grating having such a configuration, the optical element of the first optical distance portion is formed by air or vacuum, and the optical element of the second optical distance portion is the remaining optical element. Compared with the case where it is formed, the thickness can be made thinner.

  According to another aspect, in the above-described phase type diffraction grating, the outermost exposed optical element of the second optical distance portion is any one of gold, platinum, and iridium, The remaining optical elements of the two optical distance portions are any of silicon, quartz and aluminium.

  According to this configuration, any one of gold, platinum, and iridium, which is a substance having a relatively small refractive index and a relatively small phase change per unit length, and any of silicon, quartz, and aluminum Provides a phase type diffraction grating having a second optical distance portion formed thereon. Therefore, in the phase type diffraction grating having such a configuration, the optical element of the first optical distance portion is formed of air or vacuum, and the optical element of the second optical distance portion is made of silicon, quartz, or aluminum. As compared with the case of forming any of the above, the thickness can be made thinner.

  In another aspect, in the above-described phase type diffraction grating, one optical element of the first optical distance portion is a gas or a vacuum, and the outermost portion of the second optical distance portion is The outermost exposed adjacent optical element adjacent to the exposed optical element is the refractive index of the remaining optical elements excluding the outermost exposed adjacent optical element in the plurality of optical elements of the second optical distance portion. It is characterized by being a substance having a lower refractive index.

  In the phase type diffraction grating having such a configuration, the second optical distance portion is composed of a plurality of optical elements, and the optical element adjacent to the outermost exposure of the second optical distance portion is the second optical distance. The plurality of optical elements are formed of a material having a refractive index lower than the refractive index of the remaining optical elements excluding the optical element adjacent to the outermost exposure. Therefore, in the phase type diffraction grating having such a configuration, the optical element of the first optical distance portion is formed by air or vacuum, and the optical element of the second optical distance portion is the remaining optical element. Compared with the case where it is formed, the thickness can be made thinner. The outermost exposed optical element of the second optical distance portion is formed of a material having a high refractive index relative to the optical element adjacent to the outermost exposed portion of the second optical distance portion. Therefore, the optical distance of the second optical distance portion can be finely adjusted to the design value by adjusting the thickness of the outermost exposed optical element of the second optical distance portion. That is, since the outermost exposed optical element of the second optical distance portion is formed of a material having a relatively high refractive index, it is effective as an adjustment margin for adjusting the optical distance of the second optical distance portion. Is. Alternatively, the outermost exposed optical element of the second optical distance portion can be used as a protective film for the optical element adjacent to the outermost exposed portion of the second optical distance portion.

  Further, in another aspect, in the above-described phase type diffraction grating, the optical element adjacent to the outermost exposure of the second optical distance portion is any of gold, platinum, and iridium, The remaining optical element of the second optical distance portion is any one of silicon, quartz, and aluminum.

  According to this configuration, any one of gold, platinum, and iridium, which is a substance having a relatively small refractive index and a relatively small phase change per unit length, and any of silicon, quartz, and aluminum A phase type diffraction grating is provided in which a second optical distance portion is formed. Therefore, in the phase type diffraction grating having such a configuration, the optical element of the first optical distance portion is formed of air or vacuum, and the optical element of the second optical distance portion is made of silicon, quartz, or aluminum. As compared with the case of forming any of the above, the thickness can be made thinner.

  In another aspect, in the above-described phase type diffraction grating, one optical element of the first optical distance portion is a resin material.

  In the phase type diffraction grating having such a configuration, since one optical element in the first optical distance portion is a resin material, one optical element in the first optical distance portion is gas or vacuum. Compared to the case, the mechanical strength can be improved.

  According to another aspect of the method of manufacturing a phase-type diffraction grating, a pattern member is formed by forming a plurality of pattern members arranged according to a predetermined rule on a substrate with a thickness having a surface roughness allowed by specifications. The pattern member forming step has a depth corresponding to the thickness of the plurality of pattern members formed by the pattern member forming step so as to cause a predetermined phase difference between the forming step and the pattern member forming step. An etching step of etching a portion of the substrate that is not formed.

  In the manufacturing method of the phase type diffraction grating having such a configuration, the exposed surface of the optical distance portion based on the pattern member is formed with a thickness having a surface roughness allowed by specifications. For this reason, the manufacturing method of the phase type diffraction grating of such a structure can manufacture the phase type diffraction grating which can reduce the surface roughness more.

  According to another aspect, in the method of manufacturing a phase type diffraction grating described above, the pattern member forming step includes forming a film of the material of the pattern member on the substrate with a thickness having a surface roughness allowed by specifications. And a patterning step of patterning the film formed in the film formation step so as to form a plurality of pattern members arranged in accordance with the predetermined rule.

  With such a configuration, there is provided a method for manufacturing a phase type diffraction grating in which a pattern member forming step is realized using a so-called etching method.

  In another aspect, in the above-described method for manufacturing a phase-type diffraction grating, the pattern member forming step includes patterning so that a substrate in a region corresponding to a plurality of pattern members arranged according to a predetermined rule faces the outside. Forming a patterned layer on the substrate, and forming a film of the material of the pattern member on the substrate after the patterning layer forming step with a thickness having a surface roughness allowed by specifications A film forming process and a removing process for removing the patterning layer are provided.

  With such a configuration, there is provided a method of manufacturing a phase type diffraction grating that realizes a pattern member forming process using a so-called lift-off method.

  In another aspect, in the above-described method for manufacturing a phase type diffraction grating, the etching in the etching step is wet etching or dry etching.

  Such a configuration provides a method of manufacturing a phase type diffraction grating that realizes an etching process using so-called wet etching or dry etching.

  In another aspect, the above-described method for manufacturing a phase type diffraction grating is used when a phase type diffraction grating used for an X-ray Talbot interferometer or an X-ray Talbot-low interferometer is manufactured.

  As described above, the above-described method for manufacturing a phase type diffraction grating can manufacture a phase type diffraction grating capable of reducing the roughness of the surface and reducing the thickness thereof. According to this configuration, a high-performance X-ray Talbot interferometer or X-ray Talbot-low interferometer can be realized.

  A phase type diffraction grating according to another embodiment of the present invention is manufactured by any one of the above-described phase type diffraction grating manufacturing methods.

  According to this configuration, it is possible to realize a phase type diffraction grating that can reduce the roughness of the surface and reduce the thickness.

  An X-ray imaging apparatus according to another aspect of the present invention includes an X-ray source that emits X-rays, and a Talbot interferometer or a Talbot-low interferometer that is irradiated with X-rays emitted from the X-ray source. And an X-ray imaging device that captures an X-ray image by the Talbot interferometer or the Talbot-Lau interferometer, and the Talbot interferometer or the Talbot-Lau interferometer is one of the above-described phase-type diffraction gratings It is characterized by including.

  The X-ray imaging apparatus having such a configuration can reduce the roughness of the surface and further reduce the thickness of the phase diffraction grating constituting the Talbot interferometer or the Talbot-low interferometer. Since the phase type diffraction grating that can be used is used, the diffraction is more reliably performed, and a clearer X-ray image can be obtained.

  The phase type diffraction case according to the present invention can further reduce the surface roughness. The method for producing a phase type diffraction grating according to the present invention can provide a phase type diffraction grating capable of further reducing the roughness of the surface. The present invention can provide an X-ray imaging apparatus using this phase type diffraction grating.

It is a perspective view which shows the structure of the phase type diffraction grating in embodiment. It is FIG. (1) for demonstrating the 1st manufacturing method of the phase type diffraction grating in embodiment. It is FIG. (2) for demonstrating the 1st manufacturing method of the phase type diffraction grating in embodiment. It is a figure (the 1) for demonstrating the 2nd manufacturing method of the phase type diffraction grating in embodiment. It is FIG. (2) for demonstrating the 2nd manufacturing method of the phase type diffraction grating in embodiment. The length (thickness) of the silicon and the length of the gold (thickness) in the case of a phase type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of silicon and gold. FIG. In the case of a phase type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of quartz and gold (including a 100 nm thick chromium film on the gold surface), It is a figure which shows the relationship between length (thickness) and the length (thickness) of the said gold | metal | money. The length (thickness) of the quartz in the case of a phase-type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of quartz and gold (without chrome in a film shape), and It is a figure which shows the relationship with the length (thickness) of gold | metal | money. The length (thickness) of the quartz and the length (thickness) of the platinum in the case of a phase type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of quartz and platinum. FIG. The length (thickness) of the silicon in the case of a phase type diffraction grating in which the first optical distance portion is formed of polymethyl methacrylate resin (PMMA) and the second optical distance portion is formed of silicon and gold, and It is a figure which shows the relationship with the length (thickness) of gold | metal | money. The state of the gold surface in the case of the phase type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of silicon 8.1 μm and gold 1.5 μm by the first manufacturing method. FIG. It is a figure which shows the mode of the surface of the said gold | metal | money when an optical distance part is formed with comparatively thick gold | metal | money by electroforming. It is a perspective view which shows the structure of the Talbot interferometer for X-rays in embodiment. It is a top view which shows the structure of the Talbot low interferometer for X-rays in embodiment. It is explanatory drawing which shows the structure of the X-ray imaging device in embodiment. It is a figure which shows schematic structure of the X-ray imaging device in a prior art.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. Further, in this specification, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix.

(Phase-type diffraction grating of the first embodiment)
FIG. 1 is a perspective view showing a configuration of a phase type diffraction grating in the embodiment. As shown in FIG. 1, the phase type diffraction grating DG of this embodiment includes a support part 11 and a diffraction grating 12 formed on the support part 11. The support portion 11 has a plate shape or a layer shape along the DxDy plane when a DxDyDz orthogonal coordinate system is set as shown in FIG. The diffraction grating 12 is a phase type diffraction grating, and includes a plurality of first optical distance portions 12a and a plurality of second optical distance portions 12b (12b1, 12b2) between the incident surface and the exit surface. ing. The plurality of first optical distance portions 12a have a first refractive index n1 and a first thickness H1 corresponding to the first optical distance h1 and are arranged according to a predetermined rule, and the plurality of second optical distance portions 12a. Reference numeral 12b denotes a second refractive index n2 and a second refractive index n2 corresponding to a second optical distance h2 that generates a predetermined phase difference C with respect to electromagnetic waves such as X-rays and light that have passed through the first optical distance portion 12a. It has thickness H2 and is arranged according to the plurality of first optical distance portions 12a.

  More specifically, when the phase-type diffraction grating DG is one-dimensional as shown in FIG. 1, the diffraction grating 12 has the first thickness H1 (Dz direction perpendicular to the grating surface DxDy (the grating surface DxDy A plurality of first optical distance portions 12a having a length in the normal direction) and extending linearly in one direction Dx, and the second thickness H2 (the Dz direction perpendicular to the lattice plane DxDy (lattice plane DxDy)) And a plurality of second optical distance portions 12b extending linearly in the one direction Dx, and having a plurality of first optical distance portions 12a and H2 = H1). The plurality of second optical distance portions 12b are alternately arranged in parallel. For this reason, the plurality of first optical distance portions 12a are respectively arranged at predetermined intervals in a direction Dy orthogonal to the one direction Dx. In other words, the plurality of second optical distance portions 12b are disposed at predetermined intervals in a direction Dy orthogonal to the one direction Dx. The predetermined interval (pitch) P is constant in this embodiment. That is, the plurality of first optical distance portions 12a (the plurality of second optical distance portions 12b) are arranged at equal intervals P in the direction Dy orthogonal to the one direction Dx. The first optical distance portion 12a has a plate shape or a layer shape along the DxDz surface orthogonal to the DxDy surface, and the second optical distance portion 12b also has a plate shape or a layer shape along the DxDz surface.

  The first optical distance portion 12a is composed of one optical element. As described above, the optical element acts on the optical distance of the electromagnetic wave propagating through the medium, such as a substance, air, and vacuum. The optical distance h is given by the product of its refractive index n and its thickness (length) H with respect to the wavelength of incident electromagnetic waves such as X-rays and light (h = n × H). Therefore, the first optical distance h1 is n1 × H1 (h1 = n1 × H1). The one optical element of the first optical distance portion 12a has a predetermined wavelength of the electromagnetic wave used for the phase type diffraction grating DG (for example, the wavelength of X-ray), and the like. It has a refractive index higher than each refractive index in the plurality of optical elements, for example, a gas or a vacuum having a predetermined degree of vacuum. The gas includes not only a pure substance composed of one kind of simple substance or compound but also a mixture composed of a plurality of kinds such as air. For example, the one optical element of the first optical distance portion 12a may be a resin material. Thus, by forming the first optical distance portion 12a by filling it with a solid instead of a space, the phase type diffraction grating DG having such a configuration can be compared with the case where the first optical distance portion 12a is formed in a space. Thus, the mechanical strength can be improved.

  The second optical distance portion 12b is composed of a plurality of optical elements having different refractive indexes. Preferably, the sum of the thicknesses of the plurality of optical elements is the second optical distance portion. The sum of the product of the refractive index and the thickness required for each of the plurality of optical elements is equal to the second optical distance h2. Of the plurality of optical elements of the second optical distance portion 12b, the outermost exposed optical element is exposed to the electromagnetic wave propagating through the phase type diffraction grating DG, for example, against scattering. It is formed with a thickness having a surface roughness allowed by the specifications. The widths W of the first and second optical distance portions 12a and 12b are the lengths of the optical distance portions 12a and 12b in the direction (width direction) Dy orthogonal to the one direction (long direction) Dx. Yes, the thicknesses of the first and second optical distance portions 12a and 12b are in the normal direction (depth direction) Dz of the plane DxDy composed of the one direction Dx and the direction Dy perpendicular thereto. It is the length of each optical distance portion 12a, 12b. For example, the second optical distance portion 12b is composed of two first and second optical elements, and the refractive index and thickness of the first optical element portion 12b1 are n21 and H21, respectively. When the refractive index and thickness of the optical element portion 12b2 are n22 and H22, respectively, H21 + H22 = H2 (= H1), and n21 × H21 + n22 × H22 = h2. Here, in the phase grating disclosed in Patent Document 1, the filling material matches the intensity (amplitude) of the X-rays that have passed through the protrusion and the X-rays that have passed through the gap, and the zero-order diffracted light is emitted. Since it is provided at each bottom portion in the plurality of gaps in order to eliminate, not only the optical distance of the filling material but also the attenuation amount in the filling material is considered, and the phase grating disclosed in Patent Document 1 is considered. Then, the filling material cannot be determined (designed) only by the above relational expression like the phase type diffraction grating DG of the present embodiment, and is different from the phase type diffraction grating DG of the present embodiment.

  Further, in the present embodiment, the outermost exposed optical element of the second optical distance portion 12b excludes the outermost exposed optical element of the plurality of optical elements of the second optical distance portion 12b. A material having a refractive index lower than that of the remaining optical elements. For example, the outermost exposed optical element of the second optical distance portion 12b (in the above example, the optical element forming the second optical element portion 12b2 of the second optical distance portion 12b) is gold (Au). , Platinum (Pt), rhodium (Rh), ruthenium (Ru) and iridium (Ir), and the remaining optical elements of the second optical distance portion 12 (second optical in the above example). The optical element forming the first optical element portion 12b1 of the optical distance portion 12b) is any one of silicon, quartz, and aluminum. Such gold, platinum, rhodium, ruthenium and iridium have a relatively small refractive index and a unit length relative to the wavelength of a predetermined electromagnetic wave (for example, the wavelength of X-ray) used in the phase type diffraction grating DG. It is a material with a relatively small phase change. In contrast, silicon, quartz, and aluminum are substances that have a relatively high refractive index and a relatively large phase change per unit length, but are highly workable.

  The phase-type diffraction grating DG in which a portion that generates such a phase difference C is composed of a plurality of optical elements has a surface that allows a plurality of pattern members having a predetermined shape arranged on a substrate according to a predetermined rule according to specifications. A pattern member forming step of forming with a thickness having roughness, and a depth according to the thickness of the plurality of pattern members formed by the pattern member forming step so as to cause a predetermined phase difference; In the pattern member forming step, the substrate is manufactured by an etching step of etching a portion of the substrate on which the plurality of pattern members are not formed. More specifically, such a phase type diffraction grating DG is manufactured by a pattern member forming process using a so-called etching method or lift-off and an etching process using a wet etching method or a dry etching method.

  In the one-dimensional lattice, the predetermined shape of the pattern member is, for example, a stripe shape (a line shape having a predetermined width W, a band shape having a predetermined width W) in plan view having the thickness, and 2 In the dimensional lattice, for example, a column shape such as a cylinder or a prism is used. Hereinafter, a manufacturing method of the one-dimensional phase diffraction grating DG in which the pattern member has a stripe shape having the thickness will be described in detail. The same applies even if the pattern member has another shape such as a column shape having the thickness.

  Hereinafter, the first manufacturing method using the etching method will be described first, and then the second manufacturing method using the lift-off method will be described.

(First manufacturing method)
Drawing 2 is a figure (the 1) for explaining the 1st manufacturing method of a phase type diffraction grating in an embodiment. Drawing 3 is a figure (the 2) for explaining the 1st manufacturing method of the phase type diffraction grating in an embodiment.

  In the first manufacturing method, as the pattern member forming step, a film forming step of forming a film 33 of the material of the pattern member on the substrate 30 with a thickness having a surface roughness allowed by specifications is performed. A patterning process is performed in which the film 33 formed in the film forming process is patterned to form a plurality of pattern members 33 arranged according to the predetermined rule.

  More specifically, in order to manufacture the phase type diffraction grating DG of the present embodiment, first, the substrate 30 is prepared (FIG. 2A). Since this substrate 30 is processed in each step described later, it becomes the first optical element portion 12b1 of the support portion 11 and the second optical distance portion 12b, so that the first optical distance portion 12b has the first optical element portion 12b1. The material of the optical element of the optical element part 12b1 is selected. The substrate 30 is preferably made of a material whose surface can be processed smoothly for electromagnetic waves propagating through the phase type diffraction grating DG. For example, the substrate 30 is a silicon substrate 30a. Further, for example, the substrate 30 is a quartz substrate 30b. For example, the substrate 30 is an aluminum substrate 30c. In the case where the substrate 30 is a silicon substrate 30a and when wet plating such as electroforming is used when forming a film 33 described later, the silicon substrate 30a is n-type silicon whose majority carriers are electrons. Is preferred. Since this n-type silicon has abundant conductor electrons, when a negative potential is applied by connecting silicon to the cathode and the cathode is polarized, in the electroforming process described later, so-called ohmic contact is formed with the plating solution, and current flows. It tends to flow and cause a reduction reaction, and as a result, the metal is more likely to precipitate.

  Next, a film (layer) 33 of the material of the pattern member 33 is formed on the substrate 30 with a thickness having a surface roughness allowed by the specifications (deposition process, FIG. 2 ( B)). The film 33 is processed in each step described later to become the second optical element portion 12b2 of the second optical distance portion 12b. Therefore, the second optical element portion 12b2 in the second optical distance portion 12b. The material of the optical element is selected. For example, the material of the film 33 is gold. As a result, the gold pattern member 33a is obtained through the following steps. For example, the material of the film 33 is platinum. As a result, the platinum pattern member 33b is obtained through the following steps. For example, the material of the film 33 is iridium. As a result, an iridium pattern member 33c is obtained through the following steps.

  As the film forming method, for example, a dry plating method such as a vacuum deposition method, a sputtering method, and a chemical vapor deposition (CVD) method, or a wet plating method such as an electroforming method is used. The dry plating method can form a film with a surface roughness of angstrom level and can relatively easily achieve the surface roughness allowed by the specifications, but the film thickness is, for example, 3 μm, 5 μm, etc. When the thickness is several μm or more, the film formation time becomes remarkably long, or the film is easily peeled off due to stress during film formation. In this respect, the electroplating method of the wet plating method is advantageous, but the surface roughness increases as the film thickness increases, and X-rays are scattered when the film thickness becomes several μm or more. Therefore, in the dry plating method, the film thickness is preferably 2 μm or less, and in order to realize the surface roughness allowed by the specifications, at least in the wet plating method, the film thickness is preferably It is 1.5 μm or less.

  Next, in order to form the film 33 on the pattern member 33, in order to pattern the film 33 formed on the substrate 30, a photosensitive resin layer 40 is formed on the film 33 by, for example, spin coating (see FIG. 2 (C)). Here, the photosensitive resin layer 40 is a material that is used in lithography and whose physical properties such as solubility are changed by light (including not only visible light but also ultraviolet rays), an electron beam, and the like. However, the present invention is not limited to this. For example, a resist layer for electron beam exposure may be used instead of the photosensitive resin layer 40.

  Next, as a photolithography step, the photosensitive resin layer 40 is patterned by a lithography method (FIG. 2D), and the patterned photosensitive resin layer 40 is removed (FIG. 3A). More specifically, a lithography mask 41 is pressed against the photosensitive resin layer 40, and the photosensitive resin layer 40 is irradiated with ultraviolet rays 42 through the lithography mask 41, and the photosensitive resin layer 40 is subjected to pattern exposure and development. (FIG. 2D). And the photosensitive resin layer 40 of the part which was not exposed (or exposed part) is removed (FIG. 3 (A)).

  Next, using the patterned photosensitive resin layer 40 as a mask, the portion of the film 33 where the photosensitive resin layer 40 has been removed is removed by etching, and the film 33 is patterned to form the pattern member 33 (FIG. 3A). )). More specifically, for example, when the film 33 is gold, it is immersed in a so-called aqua regia and patterned by wet etching. For example, when the film 33 is platinum, it is patterned by ICP (Inductively Coupled Plasma) dry etching using hydrogen iodide gas.

  Next, a portion of the substrate 30 where the pattern member 33 is not formed is etched in the normal direction Dz at a depth corresponding to the thickness of the pattern member 33 so as to generate a predetermined phase difference (etching). Process, FIG. 3 (C)). The pattern member 33 formed by remaining by etching the film 33 shown in FIG. 3A and the pattern member 33 formed along the DxDz plane by remaining by etching the substrate 30 shown in FIG. The plate-like portion 30b (the wall portion 32 of the substrate 30) of the subsequent substrate 30 becomes the second optical distance portion 12b. More specifically, the pattern member 33 becomes the second optical element portion 12b2 of the second optical distance portion 12b, and the wall portion 32 of the substrate 30 becomes the first optical element portion of the second optical distance portion 12b. 12b1. Then, a space (first space) 34 (a space 34 sandwiched between adjacent pattern members 33) formed by etching the film 33 shown in FIG. 3A and the substrate 30 shown in FIG. 3C. A space (second space) 35 (a space 35 sandwiched between the wall portions 32 of the substrates 30 adjacent to each other) following the first space formed by etching becomes the first optical distance portion 12a (36).

  Note that the plate-like portion 30a (the base portion 31 of the substrate 30) of the substrate 30 remaining along the DxDy plane by the etching of the substrate 30 shown in FIG.

  Through the above manufacturing steps, the phase type diffraction grating DG having the configuration shown in FIG. 1 is manufactured.

(Second manufacturing method)
FIG. 4 is a view (No. 1) for describing a second manufacturing method of the phase diffraction grating in the embodiment. Drawing 5 is a figure (the 2) for explaining the 2nd manufacturing method of the phase type diffraction grating in an embodiment.

  In the second manufacturing method, as the pattern member forming step, a patterning layer 40 patterned so that the substrate 30 in a region corresponding to a plurality of pattern members arranged according to a predetermined rule faces the outside is formed on the substrate 30. A patterning layer forming step is performed, and a film forming step of forming a film 33 of the material of the pattern member with a thickness having a surface roughness allowed by the specifications is performed on the substrate 30 after the patterning layer forming step. Then, a removal step of removing the patterning layer is performed.

  More specifically, in order to manufacture the phase type diffraction grating DG of the present embodiment, first, the substrate 30 is prepared as in the first manufacturing method (FIG. 4A).

  Next, a patterning layer 40 patterned so that the substrate 30 in a region corresponding to the plurality of pattern members 33 arranged in accordance with a predetermined rule faces the outside is formed on the substrate 30 (patterning layer forming step, FIG. 4). (A) to FIG. 4 (D)). That is, the patterning layer 40 patterned to be a lift-off mask for forming the plurality of pattern members 33 arranged according to a predetermined rule is formed on the substrate 30.

  More specifically, in order to form the patterning layer 40 on the substrate 30, first, the photosensitive resin layer 40 is formed on the substrate 30 by, for example, spin coating (FIG. 4B), and then, photo As a lithography process, the photosensitive resin layer 40 is patterned by a lithography method (FIG. 4C), and the patterned photosensitive resin layer 40 is removed (FIG. 4D). More specifically, a lithography mask 41 is pressed against the photosensitive resin layer 40, and the photosensitive resin layer 40 is irradiated with ultraviolet rays 42 through the lithography mask 41, and the photosensitive resin layer 40 is subjected to pattern exposure and development. (FIG. 4C). And the photosensitive resin layer 40 of the part which was not exposed (or exposed part) is removed (FIG.4 (D)).

  Next, on the substrate 30 after the patterning layer forming step, a film 33 of the material of the pattern member is formed by a predetermined film forming method with a thickness having a surface roughness allowed by the specifications (film forming step, FIG. 5 (A)). The film 33 is processed in each step described later to become the second optical element portion 12b2 of the second optical distance portion 12b. Therefore, the second optical element portion 12b2 in the second optical distance portion 12b. The material of the optical element is selected. As this film formation method, a film formation method in which the patterning layer 40 is not lost during film formation is used. For example, a vacuum deposition method is used as this film forming method. For example, an electroforming method is used. FIG. 5A shows a film 33 when a vacuum evaporation method is used as a film formation method.

  As described above, since the vacuum deposition method is one of dry plating methods, it is possible to form a film with a surface roughness of angstrom level, and it is relatively easy to achieve the surface roughness allowed by the specifications. Although it can be achieved, when the film thickness is several μm or more such as 3 μm or 5 μm, the film tends to be peeled off by stress during film formation. In this respect, the electroplating method of the wet plating method is advantageous, but the surface roughness increases as the film thickness increases, and X-rays are scattered when the film thickness becomes several μm or more. Therefore, in the vacuum deposition method, the film thickness is preferably 2 μm or less, and in order to achieve the surface roughness allowed by the specifications, at least in the wet plating method, the film thickness is preferably It is 1.5 μm or less.

  Next, the patterning layer 40 is removed (removal process, FIG. 5B). As a result, a plurality of pattern members 33 arranged according to a predetermined rule are formed on the substrate 30.

  Next, similarly to the etching process of the first manufacturing method shown in FIG. 3C, the pattern member 33 is formed at a depth corresponding to the thickness of the pattern member 33 so as to generate a predetermined phase difference. A portion of the substrate 30 that is not etched is etched in the normal direction Dz (etching step, FIG. 5C). The pattern member 33 formed by removing the patterning layer 40 shown in FIG. 5B and the pattern member 33 formed along the DxDz plane left by etching the substrate 30 shown in FIG. 5C. Subsequent plate-like portion 32 of substrate 30 (wall portion 32 of substrate 30) becomes second optical distance portion 12b. More specifically, the pattern member 33 becomes the second optical element portion 12b2 of the second optical distance portion 12b, and the wall portion 32 of the substrate 30 becomes the first optical element portion of the second optical distance portion 12b. 12b1. Then, in the space (first space) 34 formed by removing the patterning layer 40 shown in FIG. 5B and the first space formed by etching the substrate 30 shown in FIG. 5D. The following space (second space) 35 becomes the first optical distance portion 12a (36).

  Note that the plate-like portion 30a (the base portion 31 of the substrate 30) of the substrate 30 remaining along the DxDy plane by etching of the substrate 30 shown in FIG.

  Through the above manufacturing steps, the phase type diffraction grating DG having the configuration shown in FIG. 1 is manufactured.

  In the etching process in the first and second manufacturing methods, the depth for etching the substrate 30 in the Dz direction is designed as follows.

Taking the case where the second optical distance portion 12b is formed of two first and second optical elements as an example, the refractive indexes of the first and second optical element portions 12b1 and 12b2 are expressed as n _b1. and the _{n b2,} the lengths of the first and second optical element portion 12b1,12b2 the (respective thickness) and _{H b1} and _{H b2,} respectively, the wavelength of X-rays and lambda, the phase difference n (retardation In the case of π, N = 1, and in the case of phase difference π / 2, N = 2), there is a relationship of the following formula 1.
H _b1 = {− (1−n _b2 ) × H _b2 + (λ / (2 × N))} / (1−n _b1 ) (1)
These equations 1 show how the length (thickness) of the first optical element portion 12b1 is determined after the length (thickness) of the second optical element portion 12b2 is determined. A similar expression can be derived when the second optical distance portion 12b is formed of a plurality of three or more optical elements.

  FIG. 6 to FIG. 10 show calculation examples of Equation 1 in the case of a π / 2 phase type diffraction grating for 28 keV (wavelength 0.04 nm) X-rays. FIG. 6 shows the length (thickness) of the silicon and the length of the gold in the case of a phase type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of silicon and gold. It is a figure which shows the relationship with thickness (thickness). FIG. 7 shows a case of a phase type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of quartz and gold (including gold having a film thickness of 100 nm on the gold surface). It is a figure which shows the relationship between the length (thickness) of the said quartz, and the length (thickness) of the said gold | metal | money. FIG. 8 shows the length (thickness) of the quartz in the case of a phase type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of quartz and gold (film is not chromium). It is a figure which shows the relationship between length) and the length (thickness) of the said gold | metal | money. FIG. 9 shows the length (thickness) of the quartz and the length of the platinum in the case of a phase type diffraction grating in which the first optical distance portion is formed of air and the second optical distance portion is formed of quartz and platinum. It is a figure which shows the relationship with thickness (thickness). FIG. 10 shows the length (thickness) of the silicon in the case of a phase type diffraction grating in which the first optical distance portion is formed of polymethyl methacrylate resin (PMMA) and the second optical distance portion is formed of silicon and gold. It is a figure which shows the relationship between length) and the length (thickness) of the said gold | metal | money. 6 to 10, the horizontal axis represents the thickness of the second optical element portion 12b2 expressed in μm, and the vertical axis represents the thickness of the first optical element portion 12b1 expressed in μm. . FIG. 7 shows a case of the second optical element portion 12b2 in which chromium is laminated on gold. That is, the second optical distance portion 12b is formed by three optical elements of quartz, gold, and chromium.

Here, for an X-ray of 28 keV (wavelength 0.04 nm), the refractive index n _Si of _silicon is 0.99993844-i1.2289485e-9, and the refractive index n _{SiO2 of} quartz is 0.9999999418-i7. 143670e-10, gold refractive index n _Au is 0.999995960-i2.123481e-7, platinum refractive index n _Pt is 0.999995477-i2.3151473e-7, and chromium refractive index _{n Cr} is 0.999998229-i1.8515591e-8. Further, the refractive index n _PMMA of _PMMA is 0.99999996-i1.1778217e-10. Here, i is an imaginary unit, and i ² = −1.

  As a specific example of the first manufacturing method, in the case of manufacturing a π / 2 phase type diffraction grating DG for 28 keV (wavelength 0.04 nm) X-ray, first, a silicon substrate 30a is prepared. Gold (Au) was deposited to a thickness of 1.5 μm on the substrate 30a by sputtering. Subsequently, a photosensitive resin layer 40 is applied on the main surface of the formed gold film 33 by, for example, spin coating, and then, as a photolithography process, the photosensitive resin layer 40 is patterned by a lithography method, The patterned photosensitive resin layer 40 was removed. Subsequently, the silicon substrate 30a is immersed in aqua regia, and the gold film 33 in the removed portion of the photosensitive resin layer 40 is removed by wet etching using the patterned photosensitive resin layer 40 as a mask. The film 33 was patterned to form a gold pattern member 33a. Subsequently, using the patterned gold pattern member 33a as a mask, a depth of 8.1 μm corresponding to a thickness of 1.5 μm of the pattern member 33a is generated so as to generate a predetermined phase difference π / 2 by ICP dry etching. (See FIG. 6), the portion of the silicon substrate 30a where the pattern member 33a is not formed was etched in the normal direction Dz. As a result, a π / 2 phase type diffraction grating DG was manufactured for 28 keV (wavelength 0.04 nm) X-ray.

  As another specific example of the first manufacturing method, in manufacturing a π / 2 phase type diffraction grating DG for 28 keV X-rays, first, a quartz substrate 30b is prepared, and this quartz substrate 30b is prepared. A platinum (Pt) film having a thickness of 1.5 μm was formed thereon by sputtering. Subsequently, a photosensitive resin layer 40 is applied on the main surface of the formed platinum film 33 by, for example, spin coating, and then, as a photolithography process, the photosensitive resin layer 40 is patterned by a lithography method, The patterned photosensitive resin layer 40 was removed. Subsequently, the platinum film 33 in the removed portion of the photosensitive resin layer 40 is removed by ICP dry etching using hydrogen iodide gas using the patterned photosensitive resin layer 40 as a mask. Patterned. Subsequently, using the patterned platinum film 33 as a mask, a depth corresponding to a thickness of 1.5 μm of the platinum pattern member 33 is generated so as to generate a predetermined phase difference π / 2 by ICP dry etching. At 4 μm (see FIG. 9), the portion of the silicon substrate 30a where the pattern member 33 was not formed was etched in the normal direction Dz. As a result, a π / 2 phase type diffraction grating DG was manufactured for 28 keV (wavelength 0.04 nm) X-ray.

  As a specific example of the second manufacturing method, when manufacturing a π / 2 phase diffraction grating DG for 28 keV (wavelength 0.04 nm) X-ray, first, a silicon substrate 30a is prepared, A photosensitive resin layer 40 is applied to the main surface of the silicon substrate 33a by 1.5 μm, for example, by spin coating or the like. Subsequently, as a photolithography process, the photosensitive resin layer 40 is patterned by a lithography method. Part of the photosensitive resin layer 40 was removed. Subsequently, the silicon substrate 30a on which the patterned photosensitive resin layer 40 is formed is immersed in a plating solution, and gold (Au) having a thickness of 1.0 μm is formed on the silicon substrate 30a by electroforming (electrolytic plating). A film was formed. Subsequently, the silicon substrate 30a on which the gold film 33a is formed is immersed in an organic solvent that dissolves the photosensitive resin layer 40, and the patterned photosensitive resin layer 40 is removed to form a gold pattern member 33a. It was done. Subsequently, with this gold pattern member 33a as a mask, a depth of 11.4 μm corresponding to a thickness of 1.0 μm of the pattern member 33a is generated so as to generate a predetermined phase difference π / 2 by ICP dry etching (see FIG. 6), the portion of the silicon substrate 30a where the pattern member 33a was not formed was etched in the normal direction Dz. As a result, a π / 2 phase type diffraction grating DG was manufactured for 28 keV (wavelength 0.04 nm) X-ray.

  As another specific example of the second manufacturing method, when manufacturing a π / 2 phase diffraction grating DG for 28 keV (wavelength 0.04 nm) X-ray, first, a quartz substrate 30b is prepared. Then, the photosensitive resin layer 40 is applied to the main surface of the quartz substrate 33b at a thickness of 2.0 μm, for example, by spin coating or the like. Subsequently, as a photolithography process, the photosensitive resin layer 40 is patterned by a lithography method. The patterned photosensitive resin layer 40 was removed. Subsequently, a quartz substrate 30b on which the patterned photosensitive resin layer 40 is formed is formed with a thickness of 1.6 μm on the quartz substrate 30b by a vacuum deposition method. On the film 33a, chromium (Cr) was formed to a thickness of 0.1 μm. Here, in a later-described etching process, since there is little difference in etching selectivity between quartz and gold, this chromium film is used as a gold protective film during etching. The chromium film may be used as an allowance for the optical distance of the second optical distance portion by adjusting the film thickness. Subsequently, the quartz substrate 30b on which the gold / chromium film 33 is formed is dipped in an organic solvent that dissolves the photosensitive resin layer 40, and the patterned photosensitive resin layer 40 is removed, so that a gold / chrome pattern is obtained. Member 33 was formed. Subsequently, with this gold / chrome pattern member 33 as a mask, the thickness of the gold / chrome pattern member 33 is 1.7 μm (= 1. The portion of the quartz substrate 30b having a depth of 7.6 μm corresponding to 6 μm + 0.1 μm (see FIG. 7) and not having the gold / chrome pattern member 33 formed thereon was etched in the normal direction Dz. As a result, a π / 2 phase type diffraction grating DG was manufactured for 28 keV (wavelength 0.04 nm) X-ray.

  In each of these specific examples, a step of filling the space of the first optical distance portion 12a with a solid may be further performed in order to improve mechanical strength. As one specific example, in the case of manufacturing a π / 2 phase type diffraction grating DG for 28 keV (wavelength 0.04 nm) X-ray, first, a silicon substrate 30a is prepared, and sputtering is performed on the silicon substrate 30a. Gold (Au) was deposited to a thickness of 2.0 μm by the method. Subsequently, a photosensitive resin layer 40 is applied on the principal surface of the gold 33 thus formed by, for example, spin coating, and then, as a photolithography process, the photosensitive resin layer 40 is patterned by a lithography method. The patterned photosensitive resin layer 40 was removed. Subsequently, the silicon substrate 30a is immersed in aqua regia, and the gold film 33 in the removed portion of the photosensitive resin layer 40 is removed by wet etching using the patterned photosensitive resin layer 40 as a mask. The film 33 was patterned to form a gold pattern member 33a. Subsequently, using this patterned gold pattern member 33a as a mask, a depth corresponding to a thickness of 2.0 μm of the pattern member 33 is 13.3 μm so as to generate a predetermined phase difference π / 2 by ICP dry etching. (See FIG. 10), the portion of the silicon substrate 30a where the pattern member 33a was not formed was etched in the normal direction Dz. Subsequently, the space formed by the gold pattern member 33a and the wall portion 32 of the silicon substrate 30a was filled with PMMA. As a result, a π / 2 phase diffraction grating DG was manufactured for 28 keV (wavelength 0.04 nm) X-rays with improved mechanical strength.

  As described above, in the phase type diffraction grating DG in the present embodiment, the outermost exposed optical element exposed to the outside among the plurality of optical elements of the second optical distance portion 12b, FIG. In the example shown, the second optical element portion 12b2 is formed with a thickness having a surface roughness that is allowed by specifications for, for example, scattering of electromagnetic waves propagating through the phase type diffraction grating DG. Therefore, without considering the roughness of the surface, the second optical distance portion 12b is made of gold (Au) as a single optical element, for example, by electroforming, for example, a thickness of about 3 μm in the case of π / 2 type. Also, for example, in the case of π type, if it is formed with a thickness of about 6 μm, the film formation is relatively thick. For example, in the case of π / 2 type with a thickness of about 3 μm, this is the result of observation with a laser microscope. As shown in FIG. 12, the surface is very rough for electromagnetic waves having a wavelength such as X-rays, but the phase-type diffraction grating DG in the present embodiment has a surface as described above. Since the roughness is taken into consideration, the surface roughness can be further reduced. For example, as a specific example of the phase type diffraction grating DG in the present embodiment, it is an observation result of a laser microscope on the phase type diffraction grating DG of silicon 8.1 μm / gold (Au) 1.5 μm by the first manufacturing method described above. It is as shown in FIG. In the example shown in FIG. 12, the roughness Ra is 32 Å (angstrom), but in the example shown in FIG. 11, the roughness Ra is 1 粗 (the roughness Ra is an arithmetic average roughness according to JIS B0601; 2001). Is). As a result, the performance of the phase type diffraction grating DG in the present embodiment is improved, and electromagnetic waves can be diffracted with higher accuracy.

  In the phase type diffraction grating DG in the present embodiment, one optical element of the first optical distance portion 12a is gas or vacuum, and the second optical distance portion 12b is a plurality of optical elements. And the outermost exposed optical element of the second optical distance portion 12b includes the remaining optical elements of the plurality of optical elements of the second optical distance portion 12b excluding the outermost exposed optical element. It is formed of a material having a refractive index lower than the refractive index. Therefore, in such a phase type diffraction grating DG, the optical element of the first optical distance portion 12b is formed of air or vacuum, and the optical element of the second optical distance portion 12b is the remaining optical element. The thickness of the phase type diffraction grating DG can be further reduced as compared with the case where it is formed of elements. As a result, even when the phase type diffraction grating DG is used for diffraction of electromagnetic waves such as X-rays radiated from a point wave source, so-called oblique incidence in the peripheral region of the phase type diffraction grating is reduced, and the phase type diffraction grating DG performance degradation can be reduced.

  In the phase type diffraction grating DG in the present embodiment, the outermost exposed optical element of the second optical distance portion 12b is any one of gold, platinum, and iridium, and the second optical distance portion The remaining optical element 12b is one of silicon, quartz and aluminium. In the example shown in FIG. 1, the first optical element portion 12b1 formed of any one of silicon, quartz, and aluminum as the remaining optical elements, and gold, platinum, and the outermost exposed optical elements as the remaining optical elements. A second optical distance portion 12b is formed by the second optical element portion 12b2 formed of any of iridium.

  As described above, according to the present embodiment, any one of gold, platinum, and iridium, which is a substance having a relatively large refractive index and a relatively large phase change per unit length, and any one of silicon, quartz, and aluminum. A phase type diffraction grating in which the second optical distance portion 12b is formed is provided. Therefore, in the phase type diffraction grating DG in this embodiment, the optical element of the first optical distance portion 12a is formed of air or vacuum, and the optical element of the second optical distance portion 12b is silicon. Compared with the case where it is formed of either quartz or aluminum, the thickness can be further reduced. Therefore, even when the phase type diffraction grating DG is used for diffraction of electromagnetic waves such as X-rays radiated from a point wave source, so-called oblique incidence in the peripheral region of the phase type diffraction grating is reduced, and the phase type diffraction grating DG Performance degradation can be reduced.

  Moreover, in the manufacturing method of the phase type diffraction grating DG in the present embodiment, the exposed surface of the optical distance portion based on the pattern member 33 is formed with a thickness having a surface roughness allowed by specifications. For this reason, the manufacturing method of the phase type diffraction grating DG in this embodiment can manufacture the phase type diffraction grating DG that can further reduce the roughness of the surface.

(Talbot interferometer and Talbot low interferometer)
Since the phase type diffraction grating DG of the above embodiment can manufacture a relatively thin phase type diffraction grating DG while further reducing the surface roughness, the phase type diffraction grating DG has the following characteristics: It can be suitably used for a Talbot interferometer and a Talbot-Lau interferometer for lines. An X-ray Talbot interferometer and an X-ray Talbot-low interferometer using the phase type diffraction grating DG will be described.

  FIG. 13 is a perspective view showing a configuration of an X-ray Talbot interferometer in the embodiment. FIG. 14 is a top view showing a configuration of an X-ray Talbot-Lau interferometer in the embodiment.

  As shown in FIG. 13, an X-ray Talbot interferometer 100A according to the embodiment includes an X-ray source 101 that emits X-rays having a predetermined wavelength, and a phase type that diffracts X-rays emitted from the X-ray source 101. The first and second diffraction gratings 102 and 103 include a first diffraction grating 102 and an amplitude-type second diffraction grating 103 that forms an image contrast by diffracting the X-rays diffracted by the first diffraction grating 102. Are set to the conditions constituting the X-ray Talbot interferometer. Then, the X-ray with the image contrast generated by the second diffraction grating 103 is detected by, for example, an X-ray image detector 105 that detects the X-ray. In the X-ray Talbot interferometer 100A, the first diffraction grating 102 is the phase diffraction grating DG. The conditions constituting the Talbot interferometer 100A are expressed by the above-described Expression 1 and Expression 2.

  In the X-ray Talbot interferometer 100A having such a configuration, X-rays are irradiated from the X-ray source 101 toward the first diffraction grating 102. This irradiated X-ray produces a Talbot effect at the first diffraction grating 102 to form a Talbot image. This Talbot image is acted on by the second diffraction grating 103 to form an image contrast of moire fringes. Then, this image contrast is detected by the X-ray image detector 105.

  Here, when the subject S is arranged between the X-ray source 101 and the first diffraction grating 102, the moire fringes are modulated by the subject S, and the modulation amount is caused by the refraction effect by the subject S. It is proportional to the angle at which the X-ray is bent. For this reason, the subject S and its internal structure are detected by analyzing the moire fringes.

  In the Talbot interferometer 100A configured as shown in FIG. 13, the X-ray source 101 is a single point light source, and such a single point light source forms a single slit (single slit). The X-ray radiated from the X-ray source 101 passes through the single slit of the single slit plate and is directed toward the first diffraction grating 102 via the subject S. Is emitted. The slit is an elongated rectangular opening extending in one direction.

  On the other hand, the Talbot-Lau interferometer 100B includes an X-ray source 101, a multi-slit plate 104, a first diffraction grating 102, and a second diffraction grating 103, as shown in FIG. That is, the Talbot-Lau interferometer 100B further includes a multi-slit plate 104 in which a plurality of slits are formed in parallel on the X-ray emission side of the X-ray source 101 in addition to the Talbot interferometer 100A shown in FIG. Is done. In the Talbot-Lau interferometer 100B, each slit of the multi-slit plate 104 becomes an X-ray point light source by using the multi-slit plate 104. The X-ray dose emitted toward one diffraction grating 102 increases. For this reason, the Talbot-Lau interferometer 100B can obtain better moire fringes.

(X-ray imaging device)
The phase-type diffraction grating DG can be used for various optical devices, but can be suitably used for an X-ray imaging device, for example. In particular, an X-ray imaging apparatus using an X-ray Talbot interferometer treats X-rays as waves, and detects a phase shift of X-rays caused by passing through the subject, thereby obtaining a transmission image of the subject. This is one of the methods, and is expected to improve the sensitivity by about 1000 times compared with the absorption contrast method that obtains an image in which the magnitude of X-ray absorption by the subject is a contrast, and thereby the X-ray irradiation dose is, for example, 1/100 to There is an advantage that it can be reduced to 1/1000. In the present embodiment, an X-ray imaging apparatus including an X-ray Talbot interferometer using the phase type diffraction grating DG will be described.

  FIG. 15 is an explanatory diagram illustrating a configuration of the X-ray imaging apparatus according to the embodiment. In FIG. 15, an X-ray imaging apparatus 200 includes an X-ray imaging unit 201, a second diffraction grating 202, a first diffraction grating 203, and an X-ray source 204. Furthermore, in this embodiment, an X-ray source is provided. An X-ray power supply unit 205 that supplies power to 204, a camera control unit 206 that controls the imaging operation of the X-ray imaging unit 201, a processing unit 207 that controls the overall operation of the X-ray imaging apparatus 200, and an X-ray power supply And an X-ray control unit 208 that controls the X-ray emission operation in the X-ray source 204 by controlling the power supply operation of the unit 205.

  The X-ray source 204 is a device that emits X-rays by being supplied with power from the X-ray power supply unit 205 and emits X-rays toward the first diffraction grating 203. The X-ray source 204 emits X-rays when, for example, a high voltage supplied from the X-ray power supply unit 205 is applied between the cathode and the anode, and electrons emitted from the cathode filament collide with the anode. Device.

  The first diffraction grating 203 is a transmission type diffraction grating that generates a Talbot effect by X-rays emitted from the X-ray source 204. The first diffraction grating 203 is, for example, the phase type diffraction grating DG manufactured by the method of manufacturing the phase type diffraction grating DG in the above-described embodiment. The first diffraction grating 203 is configured so as to satisfy the conditions for causing the Talbot effect, and is a grating sufficiently coarser than the wavelength of X-rays emitted from the X-ray source 204, for example, a grating constant (period of the diffraction grating). d is a phase type diffraction grating in which the wavelength of the X-ray is about 20 or more.

  The second diffraction grating 202 is a transmission-type amplitude diffraction grating that is disposed at a position that is approximately a Talbot distance L away from the first diffraction grating 203 and that diffracts the X-rays diffracted by the first diffraction grating 203.

  These first and second diffraction gratings 203 and 202 are set to conditions that constitute the Talbot interferometer represented by the above-described Expression 1 and Expression 2.

  The X-ray imaging unit 201 is an apparatus that captures an X-ray image diffracted by the second diffraction grating 202. The X-ray imaging unit 201 includes, for example, a flat panel detector (FPD) including a two-dimensional image sensor in which a thin film layer including a scintillator that absorbs X-ray energy and emits fluorescence is formed on a light receiving surface, and incident photons. An image intensifier unit that converts the electrons into electrons on the photocathode, doubles the electrons on the microchannel plate, and causes the doubled electrons to collide with phosphors to emit light, and the output light of the image intensifier unit An image intensifier camera including a two-dimensional image sensor.

  The processing unit 207 is a device that controls the overall operation of the X-ray imaging apparatus 200 by controlling each unit of the X-ray imaging apparatus 200. For example, the processing unit 207 includes a microprocessor and its peripheral circuits. An image processing unit 271 and a system control unit 272 are provided.

  The system control unit 272 controls the X-ray emission operation in the X-ray source 204 via the X-ray power source unit 205 by transmitting and receiving control signals to and from the X-ray control unit 208, and the camera control unit 206 The imaging operation of the X-ray imaging unit 201 is controlled by transmitting and receiving control signals between the two. Under the control of the system control unit 272, X-rays are emitted toward the subject S, an image generated thereby is captured by the X-ray imaging unit 201, and an image signal is input to the processing unit 207 via the camera control unit 206. The

  The image processing unit 271 processes the image signal generated by the X-ray imaging unit 201 and generates an image of the subject S.

  Next, the operation of the X-ray imaging apparatus of this embodiment will be described. For example, the subject S is placed between the X-ray source 204 and the first diffraction grating 203 by placing the subject S on an imaging table including the X-ray source 204 inside (rear surface), and the X-ray imaging apparatus 200. When the user (operator) instructs the subject S to capture an image of the subject S from the operation unit (not shown), the system control unit 272 of the processing unit 207 controls the X-ray control unit 208 to irradiate X toward the subject S. Is output. In response to this control signal, the X-ray control unit 208 causes the X-ray power source unit 205 to supply power to the X-ray source 204, and the X-ray source 204 emits X-rays and irradiates the subject S with X-rays.

  The irradiated X-ray passes through the first diffraction grating 203 through the subject S, is diffracted by the first diffraction grating 203, and is a self-image of the first diffraction grating 203 at a position away from the Talbot distance L (= Z1). A Talbot image T is formed.

  The formed X-ray Talbot image T is diffracted by the second diffraction grating 202 to generate moire and form an image of moire fringes. This moire fringe image is captured by the X-ray imaging unit 201 whose exposure time is controlled by the system control unit 272, for example.

  The X-ray imaging unit 201 outputs an image signal of the moire fringe image to the processing unit 207 via the camera control unit 206. This image signal is processed by the image processing unit 271 of the processing unit 207.

  Here, since the subject S is disposed between the X-ray source 204 and the first diffraction grating 203, the phase of the X-ray that has passed through the subject S is shifted with respect to the X-ray that does not pass through the subject S. For this reason, the X-rays incident on the first diffraction grating 203 include distortion in the wavefront, and the Talbot image T is deformed accordingly. For this reason, the moire fringes of the image generated by the superposition of the Talbot image T and the second diffraction grating 202 are modulated by the subject S, and the X-rays are bent by the refraction effect by the subject S. Proportional to angle. Therefore, the subject S and its internal structure can be detected by analyzing the moire fringes. Further, by imaging the subject S from a plurality of angles, a tomographic image of the subject S can be formed by X-ray phase CT (computed tomography).

  In the X-ray imaging apparatus 200 of the present embodiment, the first diffraction grating 201 constituting the Talbot interferometer uses a relatively thin phase type diffraction grating DG while further reducing the surface roughness. It is possible to obtain a clearer X-ray image that is more reliably diffracted.

  In the X-ray imaging apparatus 200 described above, the Talbot interferometer is configured by the X-ray source 204, the first diffraction grating 203, and the second diffraction grating 202. However, a multi-slit plate is provided on the X-ray emission side of the X-ray source 204. Furthermore, a Talbot-Lau interferometer may be configured by arranging it. By using such a Talbot-Lau interferometer, the X-ray dose irradiated to the subject S can be increased as compared with the case of a single slit, a better moire fringe can be obtained, and the subject S with higher accuracy can be obtained. An image is obtained.

  In the X-ray imaging apparatus 200 described above, the subject S is disposed between the X-ray source 204 and the first diffraction grating 203, but the subject S is disposed between the first diffraction grating 203 and the second diffraction grating 202. May be arranged.

  Further, in the above-described X-ray imaging apparatus 200, an X-ray image is captured by the X-ray imaging unit 201 and electronic data of the image is obtained, but may be captured by an X-ray film.

  In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

DG phase diffraction grating 11 support portion 12 grating 12a first optical distance portion 12b second optical distance portion 30 substrate 31 substrate base 32 substrate wall 33 pattern member 100A X-ray Talbot interferometer 100B for X-ray Talbot-Lau interferometer 102, 203 First diffraction grating 103, 202 Second diffraction grating 104 Multi slit plate 200 X-ray imaging device

Claims (14)

A plurality of first optical distance portions having a first thickness corresponding to the first optical distance and arranged according to a predetermined rule; and a predetermined amount for X-rays passing through the first optical distance portion. A second optical distance portion having a second thickness corresponding to a second optical distance causing a phase difference and arranged according to the plurality of first optical distance portions; In preparation,
The first optical distance portion is composed of one optical element;
The second optical distance portion is composed of a plurality of optical elements,
One optical element of the first optical distance portion has a refractive index higher than each refractive index of the plurality of optical elements of the second optical distance portion;
Of the plurality of optical elements in the second optical distance portion, the outermost exposed optical element exposed to the outside is a thickness having a surface roughness allowed by specifications. Type diffraction grating. One optical element of the first optical distance portion is a gas or a vacuum;
The outermost exposed optical element of the second optical distance portion is the refractive index of the remaining optical elements excluding the outermost exposed optical element of the plurality of optical elements of the second optical distance portion. The phase-type diffraction grating according to claim 1, wherein the phase-type diffraction grating is a substance having a lower refractive index. The outermost exposed optical element of the second optical distance portion is one of gold, platinum and iridium;
The phase type diffraction grating according to claim 2, wherein the remaining optical element of the second optical distance portion is any one of silicon, quartz, and aluminum. One optical element of the first optical distance portion is a gas or a vacuum;
An outermost exposed adjacent optical element adjacent to the outermost exposed optical element of the second optical distance portion is an optical element adjacent to the outermost exposed in a plurality of optical elements of the second optical distance portion. The phase-type diffraction grating according to claim 1, wherein the phase-type diffraction grating is a substance having a refractive index lower than that of the remaining optical elements excluding the elements. The optical element adjacent to the outermost exposed portion of the second optical distance portion is one of gold, platinum and iridium;
The phase type diffraction grating according to claim 4, wherein the remaining optical element of the second optical distance portion is any one of silicon, quartz, and aluminum. The phase type diffraction grating according to claim 1, wherein one optical element of the first optical distance portion is a resin material. The sum of the thicknesses of the plurality of optical elements is equal to the second thickness of the second optical distance portion, and the product of the refractive index and the thickness required for each of the plurality of optical elements. The phase type diffraction grating according to any one of claims 1 to 6, wherein each sum of is equal to the second optical distance. A pattern member forming step of forming a plurality of pattern members arranged in accordance with a predetermined rule on the substrate with a thickness having a surface roughness allowed by the specifications;
The plurality of pattern members are not formed in the pattern member forming step at a depth corresponding to the thickness of the plurality of pattern members formed in the pattern member forming step so as to cause a predetermined phase difference. An etching process for etching a portion of the substrate. A method for manufacturing a phase-type diffraction grating. The pattern member forming step includes
A film forming step of forming a film of the pattern member material on the substrate with a thickness having a surface roughness allowed by the specifications;
The phase type diffraction grating according to claim 8, further comprising a patterning step of patterning the film formed in the film forming step so as to be a plurality of pattern members arranged according to the predetermined rule. Manufacturing method. The pattern member forming step includes
A patterning layer forming step of forming on the substrate a patterning layer patterned so that the substrate in a region corresponding to a plurality of pattern members arranged according to the predetermined rule faces the outside;
A film forming step of forming a film of the pattern member material on the substrate after the patterning layer forming step with a thickness having a surface roughness allowed by specifications;
The method according to claim 8, further comprising a removing step of removing the patterning layer. The method of manufacturing a phase type diffraction grating according to any one of claims 8 to 10, wherein the etching in the etching step is wet etching or dry etching.   The method of manufacturing a phase type diffraction grating according to any one of claims 8 to 11, wherein a phase type diffraction grating used for an X-ray Talbot interferometer or an X-ray Talbot-low interferometer is manufactured.   A phase type diffraction grating manufactured by the method of manufacturing a phase type diffraction grating according to any one of claims 8 to 11. An X-ray source emitting X-rays;
A Talbot interferometer or a Talbot-low interferometer irradiated with X-rays emitted from the X-ray source;
An X-ray imaging device that captures an X-ray image by the Talbot interferometer or the Talbot-Lau interferometer,
An X-ray imaging apparatus, wherein the Talbot interferometer or the Talbot-Lau interferometer includes the phase-type diffraction grating according to any one of claims 1 to 7 and 13.