Imaging device, and image generation method

Abstract

To provide an imaging apparatus and an image generation method which can highly accurately acquire a restructured image.SOLUTION: An imaging apparatus comprises: a circular disk 21 with opening which is formed with an opening 211 through which X-rays pass; and a vacuum suction ring 24 which has an inner peripheral ring 242 and an outer peripheral ring 241 having different heights and fixes a position of the opening 211 with respect to a subject 41. The imaging apparatus further comprises: a rotary stage 22 which holds the subject 41 and the circular disk 21 with opening fixed by the vacuum suction ring 24 and can rotate at a desired angle around a rotary shaft 221 along a direction vertical to a surface of the subject 41; and a primary detector 14 in which line-shaped pixels are arranged in a prescribed pixel pitch. The imaging apparatus also comprises: an image forming mirror 13 which forms an image of the X-rays passing through the subject 41 and the opening 211 in the primary detector 14; and a control analysis unit 31 which corrects coordinates of an image intensity profile detected by the primary detector 14 to reconstruct the image of the subject from the corrected image intensity profile.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This embodiment relates to an imaging device and an image generation method.

Background Art

[0002] A transmission X-ray microscope is known as an apparatus for observing the structure of a subject with high resolution and non-destructively.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of this embodiment is to provide an imaging device and an image generation method capable of acquiring a reconstructed image with high precision.

Means for Solving the Problems

[0005] The imaging device according to this embodiment includes a sample holding plate in which an opening through which imaging light irradiated on a subject can pass is formed. The imaging device also has a first surface to which the subject can be fixed and a second surface to which the sample holding plate can be fixed and which is formed parallel to the first surface at a height different from that of the first surface, and further includes a fixing member that fixes the position of the opening with respect to the subject. Furthermore, the imaging device includes a rotating member that holds the subject fixed by the fixing member and the sample holding plate and is rotatable at a desired angle about a rotation axis along a direction perpendicular to the surface of the subject, and a detector in which a plurality of linear pixels each having a linear light-receiving surface extending in a first direction are arranged side by side in a second direction orthogonal to the first direction. The imaging device also includes an imaging optical member that forms an image of the imaging light passing through the subject and the opening on the detection surface of the detector, and an image processing unit that corrects the coordinates of the image intensity profile detected by the detector and reconstructs an image of the subject from the corrected image intensity profile.

Brief Description of the Drawings

[0006]

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Embodiments for Carrying Out the Invention

[0007] Hereinafter, embodiments will be described with reference to the drawings. (First Embodiment) The imaging device of the embodiment is, for example, a transmission X-ray microscope. The transmission X-ray microscope is an imaging optical system using electromagnetic waves with a short wavelength and has a high resolution of about several tens of nm. Also, since X-rays have a high transmittance, it is possible to observe the internal structure of a relatively thick specimen such as a silicon wafer on which a semiconductor device or the like is formed on the surface.

[0008] FIG. 1 is a schematic diagram for explaining an example of the configuration of the imaging device of the embodiment. The imaging device includes an X-ray source 11, an illumination mirror 12, an imaging mirror 13, and a one-dimensional detector 14. The imaging device also includes a disk 21 with an opening, a rotary stage 22, a stage drive unit 23, a vacuum suction ring 24, and a control and analysis unit 31.

[0009] The X-ray source 11 is an X-ray source that generates X-rays by irradiating an electron beam onto a target made of molybdenum or the like. The illumination mirror 12 is used to condense the X-rays emitted from the X-ray source 11 toward the opening 211 of the disk 21 with an opening. For example, a Montel mirror is used for the illumination mirror 12.

[0010] The disk 21 with an opening as a sample holding plate is a thin disk-shaped member having an opening 211 at its center. The opening 211 preferably has a point-symmetric shape such as a circle or a regular polygon with an even number of vertices. The disk 21 with an opening is held at its periphery by a rotary stage 22 and is arranged parallel to the X-Y plane. The rotary stage 22 as a rotating member is a member that supports the disk 21 with an opening so that it can be rotated to a desired angle with the Z direction as the rotation axis 211. The rotary stage 22 has a chuck which is a hollow ring-shaped member. The disk 21 with an opening is placed on the chuck of the rotary stage 22 so that the center of the opening 211 coincides as much as possible with the rotation axis 221.

[0011] The specimen 41 is, for example, a silicon wafer on which a semiconductor device is formed. The specimen 41 is held by a vacuum suction ring 24 and is placed below the disk 21 with an opening so that its surface is parallel to the disk 21 with an opening. FIG. 2 is a perspective view of the vacuum suction ring. As shown in FIG. 2, the vacuum suction ring 24 as a fixing member is a ring-shaped member having an opening at its center. There is a step 240 on the upper surface, and the upper surface (the first surface) of the inner peripheral ring 242 located inside the step 240 is formed lower than the upper surface (the second surface) of the outer peripheral ring 241 located outside the step 240. The inner peripheral ring 242 is a holding portion for the specimen 41, and the outer peripheral ring 241 is a connecting portion with the disk 21 with an opening. That is, the specimen 41 is placed on the upper surface of the inner peripheral ring 242 with its surface (the surface on which the pattern is formed) facing upward. Also, the disk 21 with an opening is placed on the upper surface of the outer peripheral ring.

[0012] FIG. 3 is a schematic diagram for explaining the positional relationship between the disk 21 with an opening held by the vacuum suction ring 24 and the specimen 41. FIG. 3 is an enlarged view of the rectangular region A indicated by the dotted line in FIG. 1. When the pixel pitch of the one-dimensional detector 14 described later is P, the wavelength of the X-ray emitted from the light source 11 is λ, and the imaging magnification by the imaging mirror 13 described later is M, it is desirable to set the distance L between the upper surface of the specimen 41 and the lower surface of the disk 21 with an opening to be equal to or less than (P^2) / {(M^2)×λ}. By setting it in this way, it becomes possible to suppress the influence of the Fresnel interference fringes due to the opening 211. That is, the height of the step 240 of the vacuum suction ring 24 is set so that when the specimen 41 and the disk 21 with an opening are placed on the vacuum suction ring 24, the distance L between the upper surface of the specimen 41 and the lower surface of the disk 21 with an opening is equal to or less than (P^2) / {(M^2)×λ}.

[0013] The vacuum suction ring 24 has a hollow structure. Three vacuum suction ports 244 are provided in the inner peripheral ring 242. The upper surface of the vacuum suction port 244 is formed to be higher than the upper surface of the inner peripheral ring 242 by a predetermined height. Also, three vacuum suction ports 243 are provided in the outer peripheral ring 241. The upper surface of the vacuum suction port 243 is formed to be higher than the upper surface of the outer peripheral ring 241 by a predetermined height. Suction holes 245 are provided in all the vacuum suction ports 243 and 244. Further, a connection hole 246 for connecting one end of the tube 26 is provided in the outer peripheral ring 241.

[0014] As shown in FIG. 1, a vacuum pump 25 is connected to the other end of the tube 26. The test specimen 41 is placed on the upper surface of the inner peripheral ring 242, and the vacuum pump 25 is driven with the disk 21 with an opening placed on the upper surface of the outer peripheral ring. By this, the upper surface of the vacuum suction port 244 and the lower surface of the test specimen 41 are fixed by vacuum suction, and the upper surface of the vacuum suction port 243 and the lower surface of the disk 21 with an opening are fixed. That is, by vacuum suction, the test specimen 41 and the disk 21 with an opening are fixed to the vacuum suction ring 24 in a state of being supported at three points respectively. At this time, when viewed from above in the Z direction, after adjusting the position of the disk 21 with an opening so that the observation target area of the test specimen 41 is exposed from the opening 211, the test specimen 41 and the disk 21 with an opening are fixed to the vacuum suction ring 24 by vacuum suction.

[0015] In this way, by fixing the test specimen 41 and the disk 21 with an opening to the vacuum suction ring 24 by vacuum suction, it is possible to prevent displacement between the disk 21 with an opening and the test specimen 41 even when the disk 21 with an opening is rotated during observation. The test specimen 41, the vacuum suction ring 24, and the disk 21 with an opening, which are suction-fixed to each other, are placed so that the center of the opening 211 coincides as much as possible with the rotation axis 221 of the rotation stage 22. Note that three or more vacuum suction ports 244 and 243 may be provided respectively to hold the test specimen 41 and the disk 21 with an opening at multiple points.

[0016] The imaging mirror 13 as an imaging optical member condenses the X-rays that have passed through the aperture 211 and transmitted through the observation region 411 of the subject 41, and forms an image of the subject 41 on the detection surface 141 of the one-dimensional detector 14. Note that the size of the detection surface 141 shall be sufficiently larger than the size of the image to be formed. FIG. 4 is a schematic diagram for explaining the configuration of the one-dimensional detector. As shown in FIG. 4, the one-dimensional detector 14 is configured by arranging line-shaped pixels 142 extending in the D2 direction at equal intervals in the D1 direction within the detection surface 141. Note that the D1 direction and the D2 direction are orthogonal to each other. The image of the subject 41 arranged parallel to the X-Y plane is formed on the D1-D2 plane of the detection surface 141. That is, the D1 direction of the detection surface 141 corresponds to the X direction of the subject 41. Further, the D2 direction of the detection surface 141 corresponds to the Y direction of the subject 41. For the one-dimensional detector 14, for example, a superconducting strip detector in which a plurality of superconducting strips (superconducting single-photon detectors) are arranged is used. In order to make the cross-sectional area of the superconducting strip 142, which is a line-shaped pixel, small enough for the segmentation of the superconducting region to occur, the width and thickness of the superconducting strip 142 are preferably formed to be 200 nm or less. In the following description, the sum of the width of one superconducting strip 142 and the interval between adjacent superconducting strips 142 is defined as the pixel pitch P.

[0017] FIG. 5 is a schematic circuit configuration diagram of the one-dimensional detector. As shown in FIG. 5, the one-dimensional detector 14 includes a current source 143 that is connected to the other end of the superconducting strip 142 with one end grounded and supplies a bias current Ib to the superconducting strip 142, an amplifier 144 that amplifies the electrical signal generated in the superconducting strip 142, and a measuring instrument 145 that counts the pulsed electrical signal detected at the time of detecting an X-ray photon based on the output signal of the amplifier 144. Note that the current source 143, the amplifier 144, and the measuring instrument 145 can also be provided outside the one-dimensional detector 14. For example, the current source 143, the amplifier 144, and the measuring instrument 145 can be provided within the control and analysis unit 31.

[0018] FIG. 6 is a diagram for explaining the detection principle of X-ray photons in a superconducting strip. First, the superconducting strip 142 is cooled below the transition temperature by a refrigerator (not shown) to make it superconducting. Then, a bias current Ib slightly less than the critical current for maintaining the superconducting state of the superconducting strip 142 is supplied from the current source 143. In this state, X-ray photons are incident on the superconducting strip 142.

[0019] At this time, the width of the superconducting strip 142 (the length W in the D1 direction in FIG. 4) and the thickness are formed to be about 200 nm, and the cross-sectional area of the superconducting strip 142 is small. Therefore, when X-ray photons are absorbed by the superconducting strip 142, as shown in FIG. 5, a region (hot spot region) 51 that transitions to normal conduction, called a hot spot, is formed in the superconducting region 50 of the superconducting strip 142. Since the electrical resistance of the hot spot region 51 increases, as shown in FIG. 6, the bias current Ib bypasses the hot spot region 51 and flows in another region, the bypass region 52.

[0020] When a current equal to or greater than the critical current flows through the bypass region 52, the bypass region 52 transitions to normal conduction and the electrical resistance increases, and finally the superconducting region 50 is divided. That is, a state (divided state) in which the superconducting region of the superconducting strip 142 described above is divided occurs. After that, since the hot spot region 51 and the bypass region 52 that have transitioned to normal conduction quickly disappear by cooling, a pulsed electrical signal is generated by the temporary electrical resistance generated by the division of the superconducting region 50. By amplifying this pulsed electrical signal with the amplifier 144 and counting it with the measuring device 145, the number of X-ray photons can be detected. The number of X-ray photons (photons) for each superconducting strip 142 counted by the measuring device 145, that is, the detection result of the one-dimensional detector 14, is output to the control and analysis unit 31.

[0021] The control and analysis unit 31 as the image processing unit analyzes the detection results output from the one-dimensional detector 14 and reconstructs the image of the subject 41. For the control and analysis unit 31, for example, a personal computer equipped with a central processing unit (CPU) and a memory (RAM) can be used. The operation of reconstructing the image of the subject 41 is, for example, stored in the memory in advance as a program and executed by the CPU, so it is performed software-wise. Also, the operation of reconstructing the image of the subject 41 may be performed by one or more processors configured as hardware. For example, it may be a processor configured as an electronic circuit, or a processor configured as an integrated circuit such as an FPGA (Field Programmable Gate Array). Also, the control and analysis unit 31 outputs a control signal to the stage drive unit 23 that rotates the rotation stage 22, and instructs the rotation timing, rotation angle, etc.

[0022] Note that the imaging device of the embodiment is not limited to the configuration in which the subject 41 is arranged below the disk 21 with an opening as shown in FIG. 1, and as shown in FIG. 7, the subject 41 may be arranged above the disk 21 with an opening. FIG. 7 is a schematic diagram for explaining another configuration example of the imaging device of the embodiment. In the case of the imaging device having the configuration shown in FIG. 7, the vacuum suction ports 243 of the vacuum suction ring 24 are arranged on the lower surface of the outer peripheral ring 241. The lower surface of the vacuum suction port 243 is formed higher than the lower surface of the outer peripheral ring 241 by a predetermined height, and the lower surface of the vacuum suction port 243 and the upper surface of the disk 21 with an opening are fixed by the suction holes 245 provided in the vacuum suction port 243. At this time, when viewed from below in the Z direction, after adjusting the position of the disk 21 with an opening so that the observation region 411 of the subject 41 is exposed from the opening 211, the subject 41 and the disk 21 with an opening are fixed to the vacuum suction ring 24 by vacuum suction. That is, in the case of the configuration shown in FIG. 7, the subject 41 is placed on the inner peripheral ring 242 with the back surface (the surface on which no pattern is formed) facing upward.

[0023] Next, an image generation method will be described. Prior to the image generation method of the embodiment, the image generation method of the comparative example will be described. FIG. 8 is an explanatory diagram of image reconstruction. Taking as an example the case of observing a subject 41 with a pattern formed as shown in FIG. 8(A), it will be described below. First, as shown in FIG. 8(B)(a), the subject 41 is set on the rotary stage 22, and X-rays are irradiated from the light source 11 onto the subject 41 on the rotary stage 22. In each of the diagrams of FIGS. 8(B)(a) to (d), the upper part is a diagram showing the positional relationship between the subject 41 and the pixel 142 of the primary detector 41, and the lower part shows an example of an image intensity profile. In the upper diagrams of FIGS. 8(B)(a) to (d), the subject 41 is shown as a thick-line rectangle, and the linear pixel 142 is shown as a hatched strip-shaped rectangle. Also, FIGS. 8(B)(a), (b), (c), and (d) show the cases of rotation angles of 0°, 30°, 60°, and 90°, respectively.

[0024] Then, the X-rays transmitted through the subject 41 are imaged on the detection surface 141 of the primary detector 14. In the primary detector 14, the number of X-ray photons (#ph) is detected for each linear pixel (superconducting strip) 142 by counting the pulsed electrical signals generated by the segmentation of the superconducting region 50 with the measuring instrument 145. Then, by plotting the intensity of the X-rays (the number of X-ray photons) detected by each pixel 142 against the coordinates of each pixel, an image intensity profile as shown in FIG. 8(B)(a) is obtained. That is, an image intensity profile when the rotation angle of the subject 41 is 0° is obtained.

[0025] Similarly, while rotating the rotary stage 22 by arbitrary rotation angles (Δθ), image intensity profiles are acquired at each rotation angle (FIGS. 8(B)(b) to (d)). Then, an image is reconstructed from all the acquired image intensity profiles using the projection slice theorem to obtain an image of the subject 41. Specifically, the image intensity profiles acquired at each rotation angle are Fourier-transformed, and contour lines of the Fourier-transformed profiles at all the rotation angles are created to generate a Fourier-transformed image of the X-ray transmission image of the subject 41. FIG. 8(C) is a diagram schematically showing the generated Fourier-transformed image. The X-ray transmission image of the subject 41 is reconstructed by inverse Fourier-transforming the Fourier-transformed image of the X-ray transmission image of the subject 41. FIG. 8(D) shows the reconstructed image of the subject 41.

[0026] At the time of image generation, while rotating the rotary stage 22 by arbitrary rotation angles (Δθ) with the rotation axis 221 of the rotary stage 22 and the center of the observation region 411 of the subject 41, that is, the center 211C of the aperture 211 being aligned, image intensity profiles are acquired at each rotation angle. In the image generation method of the above-described comparative example, due to mechanical errors of the rotary stage 22 or the like, the position of the rotation axis 221 may deviate from the center 211C of the aperture 211 during setting or rotation. FIGS. 9 and 10 are diagrams for explaining the position of the subject (observation region) for each rotation angle, FIG. 9 shows the case where the rotation axis and the aperture center are aligned, and FIG. 10 shows the case where the rotation axis and the aperture center are not aligned.

[0027] The case of rotating the observation region 411 that passes through the center 211C, has a dotted pattern in the X and Y directions, and has a circular pattern on the dotted line extending in the Y direction will be described. As shown in FIG. 9(A), when the position of the rotation axis 221 coincides with the center 211C of the opening 211, the position of the opening center 211C does not change even if the rotation stage 22 is rotated. FIG. 9(B) is a diagram showing the observation regions 411 when the rotation stage 22 is rotated by 0°, 30°, 60°, and 90° superimposed. When the rotation axis 211 coincides with the center 211C, as shown in FIG. 9(B), the position of the opening 211 does not change even as the rotation angle advances, and the position of the center 211C also does not change.

[0028] On the other hand, as shown in FIG. 10(A), when the position of the rotation axis 221 does not coincide with the center 211C of the opening 211, the position of the opening center 211C changes when the rotation stage 22 is rotated. FIG. 10(B) is a diagram showing the observation regions 411 when the rotation stage 22 is rotated by 0°, 30°, 60°, and 90° superimposed. When the rotation axis 211 does not coincide with the center 211C, as shown in FIG. 10(B), as the rotation angle advances, the position of the opening 211 changes, and the position of the center 211C also changes in the X and Y directions.

[0029] FIG. 11 is a diagram for explaining the displacement of the opening center due to the rotation axis misalignment. Among the diagrams of the 2 rows × 4 columns = 8 observation regions 411 shown in FIG. 11, the upper 4 show the case where the rotation axis 221 coincides with the opening center 211C (no displacement), and the lower 4 show the case where the rotation axis 221 and the opening center 211C are misaligned (displacement). Also, from the left end to the right end, the first column shows the position of the observation region 411 when the rotation angle is 0°, the second column shows the position when the rotation angle is 30°, the third column shows the position when the rotation angle is 60°, and the fourth column shows the position when the rotation angle is 90°.

[0030] As shown in the first column, let C be the X coordinate of the aperture center when the rotation angle is 0°. When the rotation angle is 30° (second column), if there is no misalignment, the X coordinate of the aperture center remains C. On the other hand, if there is misalignment, the X coordinate of the aperture center becomes B1 and moves to a position different from C. When the rotation angle reaches 60° (third column), if there is no misalignment, the X coordinate of the aperture center remains C, but if there is misalignment, the X coordinate of the aperture center becomes B2 and the distance from C increases. When the rotation angle reaches 90° (fourth column), if there is no misalignment, the X coordinate of the aperture center remains C, but if there is misalignment, the X coordinate of the aperture center becomes B3 and the distance from C further increases.

[0031] In this way, when obtaining the image intensity profile while rotating the rotation stage 22 with the position of the rotation axis 221 shifted from the center 211C of the aperture 211, X-ray photons are detected at pixels different from the pixels that should originally be detected. When reconstructing the image using the projection slice theorem, since the image intensity profile is integrated based on the pixel positions, if the position of the aperture center 211C shifts depending on the rotation angle due to the misalignment of the rotation axis 211, correct integration cannot be performed and the accuracy of the reconstructed image decreases.

[0032] Therefore, the image generation method of the embodiment calculates the amount of misalignment of the position of the center 211C of the aperture 211 in the image intensity profile for each rotation angle, corrects the position of the image intensity profile, and then reconstructs the image. Hereinafter, the image generation method of the embodiment will be described with reference to FIG. 12. FIG. 12 is a flowchart for explaining an example of the image generation method in the first embodiment.

[0033] Prior to the observation, as pre-observation preparation, the subject 41 is placed on the rotation stage 22. That is, when viewed from the Z direction, the subject 41 and the disk 21 with an aperture are aligned so that the region to be observed of the subject 41 is exposed from the aperture 211 of the disk 21 with an aperture, and both are fixed by the vacuum suction ring 24. Then, the disk 21 with an aperture is fixed to the rotation stage 22 to complete the installation of the subject 41.

[0034] When the above preparatory work is completed, observation (image generation) is started. First, the step angle Δθ of the rotary stage 22 is set (S1). The step angle Δθ is the interval of the angle for acquiring the image intensity profile. In normal observation, while rotating the rotary stage 22 in the range of 0° or more and less than 180°, the image intensity profile is acquired. Next, the rotation angle θ of the rotary stage 22 is set to 0° (initial value) (S2).

[0035] X-rays are irradiated from the light source 11, and the image intensity profile of the subject 41 is acquired (S3). When θ + Δθ is less than 180° (the maximum value of the observation angle) (S4, NO), the step angle Δθ is added to the current rotation angle θ to calculate the next rotation angle θ, and the rotary stage 22 is rotated to the next rotation angle θ (S5). Then, S3 is executed to acquire the image intensity profile at the set rotation angle θ.

[0036] On the other hand, when θ + Δθ is 180° (the maximum value of the observation angle) or more (S4, YES), since the acquisition of the image intensity profile in the set rotation angle range is completed, the process proceeds to S6. In S6, the positions of the acquired image intensity profiles are corrected for each rotation angle. FIG. 13 is a diagram for explaining the position correction method of the image intensity profile in the first embodiment. Among the 3 rows × 2 columns = 6 image intensity profiles shown in FIG. 13, the left column shows the profile before correction, and the right column shows the profile after correction. The upper row shows the profile when the rotation angle is θ1, the middle row shows the profile when the rotation angle is θ2, and the lower row shows the profile when the rotation angle is θ3. For example, the image intensity profile acquired at the rotation angle θ1 is the profile P11 shown on the upper left side, and the profile after position correction is the profile P12 shown on the upper right side. The position correction of the image intensity profile in S6 will be described with reference to FIG. 13.

[0037] First, in the image intensity profile obtained for each rotation angle, the pixel position of the aperture center 211C is estimated. When the aperture 211 is circular, assuming that at least a part of the X-rays passes through all of the observation region 411, it can be estimated that the pixel position where the intensity is maximum in the image intensity profile corresponds to the aperture center 211C. Alternatively, the midpoint of the range (L1 to R1) where the X-ray intensity is observed in the image intensity profile may be estimated to correspond to the aperture center 211C.

[0038] When there is no axial deviation of the rotation axis 221, the positions of the aperture center 211C in the image intensity profiles at all rotation angles are at the same position. Therefore, correct the positions of the respective image intensity profiles so that the positions of the estimated aperture center 211C in the image intensity profiles at all rotation angles are at the same position. For example, correct the coordinates so that the pixel position of the aperture center 211C in all the image intensity profiles comes to the origin (X = 0).

[0039] As shown in FIG. 13, for the case where the pixel position of the aperture center 211C in the image intensity profile P11 at the rotation angle θ1 is estimated to be C1, the pixel position of the aperture center 211C in the image intensity profile P21 at the rotation angle θ2 is estimated to be C2, and the pixel position of the aperture center 211C in the image intensity profile P31 at the rotation angle θ3 is estimated to be C3, the correction method will be specifically described. The image intensity profile P11 at the rotation angle θ1 shown on the upper left is corrected to the image intensity profile P21 where the pixel position of the aperture center 211C is 0 as shown on the upper right by shifting the image intensity profile only by C1 in the negative X direction. The image intensity profile P21 at the rotation angle θ2 shown in the middle left is corrected to the image intensity profile P22 where the pixel position of the aperture center 211C is 0 as shown in the middle right by shifting the image intensity profile only by C2 in the negative X direction. The image intensity profile P31 at the rotation angle θ3 shown on the lower left is corrected to the image intensity profile P32 where the pixel position of the aperture center 211C is 0 as shown on the lower right by shifting the image intensity profile only by C3 in the negative X direction.

[0040] Finally, using the image intensity profiles of all the rotation angles corrected in S6, an X-ray transmission image of the observation region 411 is reconstructed (S7), and a series of procedures related to the image generation method of the embodiment are terminated.

[0041] As described above, according to the imaging apparatus of the embodiment, since the positional relationship between the subject 41 and the opening 211C is fixed by the vacuum suction ring 24, only the X-rays passing through the observation region 411 are detected by the one-dimensional detector 14. Therefore, even if the rotation axis 221 of the rotary stage 22 fluctuates, it is possible to correct the coordinates from the obtained image intensity profile, and a highly accurate reconstructed image can be obtained. (Second Embodiment) Next, the second embodiment will be described. The image generation method of this embodiment is different from that of the first embodiment described above in the coordinate correction method of the image intensity profile. The configurations of the imaging apparatus and the image forming apparatus are the same as those of the first embodiment described above, so the description thereof will be omitted, and hereinafter, only the differences from the first embodiment will be described.

[0042] In the first embodiment described above, the coordinates are corrected using the center of the image intensity profile. In contrast, in this embodiment, a reference image intensity profile is created from the reconstructed image, and the coordinates of the image intensity profile are corrected. Hereinafter, the image generation method of the embodiment will be described with reference to FIGS. 14 to 16. FIG. 14 is a flowchart for explaining an example of the image generation method in the second embodiment. FIG. 15 is a diagram for explaining the change of the reconstructed image in the second embodiment. FIG. 16 is a diagram for explaining the position correction method of the image intensity profile in the second embodiment.

[0043] Observation Preparation (Installation of the Specimen 41 on the Rotation Stage 22): Since the procedures of each of S1 to S5 are the same as those of the first embodiment shown in FIG. 12, the description thereof is omitted. After the acquisition of the image intensity profile within the set rotation angle range is completed (S4, YES), an X-ray transmission image of the observation region 411 is reconstructed using the obtained image intensity profile (S6). Note that the image intensity profile used in S6 is the image intensity profile obtained in S3 (without coordinate correction). As shown in FIG. 15(A), when observing the observation region 411 in which a pattern is formed using the circular aperture 211 such that the left half region is less permeable to X-rays and the right half region is more permeable to X-rays, if an axial deviation of the rotation axis 221 occurs, an image in which the boundary between the region where X-rays are less permeable and the region where X-rays are more permeable is blurred, as shown in FIG. 15(B), for example, is reconstructed.

[0044] Next, from the generated reconstructed image, an image intensity profile for each rotation angle is calculated (S7). Specifically, the image intensity of the obtained reconstructed image is integrated in the direction of the inclination angle θ. By plotting the integrated value with the direction orthogonal to the angle θ as the X-axis, a reference image intensity profile is created. The reconstructed image obtained at this time corresponds to the image of the observation region 411. In this way, for each of all the rotation angles at which the image intensity profile was obtained in S3, a reference image intensity profile is calculated.

[0045] The reference image intensity profile integrated in the direction of the inclination angle θ corresponds to the image intensity profile obtained at the rotation angle θ. At the same angle θ, the reference image intensity profile generated in S7 and the image intensity profile obtained in S3 are compared, and the coordinates of the image intensity profile are corrected so that the two match most closely (S8).

[0046] Of the nine image intensity profiles shown in Fig. 16, which are 3 rows × 3 columns, the left column shows the pre-correction profile (measurement profile) obtained in S3. Also, the middle column shows the reference image intensity profile (reference profile) generated in S7. Furthermore, the right column shows the image intensity profile with coordinate correction in S8 (post-correction profile). The upper row shows the profile when the rotation angle is θ1, the middle row shows the profile when the rotation angle is θ2, and the lower row shows the profile when the rotation angle is θ3. For example, the image intensity profile obtained at the rotation angle θ1 is the profile P11 shown in the upper left. The reference image intensity profile at the angle θ1 created from the image reconstructed using the measurement profile shown in the left column is the profile Pr11 shown in the middle of the upper row. The profile Pc11 shown in the upper right is the result of position-correcting the profile P11 based on the profile Pr11.

[0047] The coordinate correction in S8 may be performed, for example, so that the coordinates at which the X-ray intensity peaks match, or so that the area of the difference region between the image intensity profile obtained in S3 and the reference image intensity profile is minimized, or using other logic. Fig. 16 shows as an example the case of performing correction so that the coordinates at which the X-ray intensity peaks match. For example, at the rotation angle θ2, let the position where the X-ray intensity peaks in the measurement profile P12 be C12, and the position where the X-ray intensity peaks in the reference profile Pr12 be Cr12. The measurement profile P12 is shifted in the X direction by (Cr12 - C12) so that the position where the X-ray intensity peaks becomes Cr12, and the post-correction profile Pc21 is generated. The image intensity profiles for other rotation angles are corrected in the same way.

[0048] Subsequently, an X-ray transmission image of the observation region 411 is reconstructed (S9) using the image intensity profile corrected in S8. The corrected image intensity profile is compared with the reference image intensity profile. If the difference between the two exceeds a predetermined range (the degree of coincidence does not meet the predetermined range) (S10, NO), the process returns to S7, and the reference image intensity profile is calculated using the reconstructed image generated in S9. Note that, as a parameter indicating the difference (degree of coincidence) between the two in S10, for example, the difference in image intensity between the two at each coordinate can be cited.

[0049] If the difference between the two is within the predetermined range (the degree of coincidence reaches the predetermined range) (S10, YES), the reconstructed image generated in S9 is taken as the X-ray transmission image of the observation region 411, and a series of procedures regarding the image generation method of the embodiment are terminated. FIG. 15(C) shows the reconstructed image after repeating the procedures from S7 to S10 m times. As described above, by repeatedly executing the generation of the reference image intensity profile and the correction of the image intensity profile, the degree of blurring of the boundary between the region where X-rays are less likely to penetrate and the region where X-rays are more likely to penetrate due to the rotation axis misalignment is reduced, and an image close to the observation region 411 shown in FIG. 15(A) can be obtained.

[0050] Thus, according to the image generation method of the embodiment, even when it is difficult to discriminate the aperture center 211C from the image intensity profile or when the shape of the aperture 211 is not point-symmetrical, it is possible to accurately correct the coordinates of the image intensity profile. Therefore, a highly accurate reconstructed image can be obtained.

[0051] Although some embodiments of the present invention have been described, these embodiments are shown as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0052] 11… Light source, 12… Illumination mirror, 13… Imaging mirror, 14… One-dimensional detector, 21… Disk with opening, 22… Rotation stage, 23… Stage drive unit, 24… Vacuum suction ring, 25… Vacuum pump, 26… Tube, 31… Control and analysis unit, 41… Specimen, 50… Superconducting region, 51… Hot spot region, 52… Detour region, 141… Detection surface, 142… Superconducting strip, 143… Current source, 144… Amplifier, 145… Measuring instrument, 211… Opening, 221… Rotation axis, 240… Step, 241… Outer peripheral ring, 242… Inner peripheral ring, 243, 244… Vacuum suction ports, 245… Suction holes, 246… Connection holes, 411… Observation region

Claims

1. A sample holding plate having an opening through which imaging light irradiated onto a subject can pass; A fixing member having a first surface to which the subject can be fixed and a second surface to which the sample holding plate can be fixed and which is formed parallel to the first surface at a height different from that of the first surface, and fixing the position of the opening with respect to the subject; A rotating member that holds the subject fixed by the fixing member and the sample holding plate and is rotatable at a desired angle about a rotation axis along a direction perpendicular to the surface of the subject; A detector in which a plurality of linear pixels having a linear light receiving surface extending in a first direction are arranged side by side in a second direction orthogonal to the first direction; An imaging optical member that forms an image of the imaging light passing through the subject and the opening on the detection surface of the detector; An image processing unit that corrects the coordinates of the image intensity profile detected by the detector and reconstructs an image of the subject from the corrected image intensity profile; An imaging device comprising:

2. The imaging device according to claim 1, wherein the distance from the upper surface of the sample fixed to the first surface to the second surface is equal to or less than a value obtained by dividing the square of the pixel pitch of the linear pixels of the detector by the product of the square of the magnification of the imaging optical member and the wavelength of the imaging light.

3. The imaging device according to claim 1, wherein the linear pixel is a superconducting single photon detector.

4. The imaging device according to claim 1, wherein the image processing unit corrects the coordinates of the image intensity profile with reference to the center coordinates of the image intensity profile detected by the detector.

5. The imaging device according to claim 1, wherein the image processing unit calculates a reference image intensity profile by integrating the image of the subject reconstructed from the image intensity profile in the direction of the angle by which the subject is rotated by the rotating member, and corrects the coordinates of the image intensity profile with reference to the reference image intensity profile.

6. The imaging device according to claim 5, wherein the reconstruction of the image of the subject and the correction of the coordinates of the image intensity profile are repeatedly performed until the difference between the reference image intensity profile and the image intensity profile falls within a preset allowable range.

7. Irradiating imaging light onto a subject fixedly installed at a predetermined distance from a sample holding plate; While rotating the subject by a predetermined angle each time, the imaging light that has passed through the opening formed in the sample holding plate among the imaging light that has passed through the subject is detected each time of rotation, and an image intensity profile is generated for each rotation angle. In an image generation method for reconstructing an image of the subject using the image intensity profile, For all of the rotation angles, calculating the center coordinates of the image intensity profile; For all of the rotation angles, correcting the coordinates of the image intensity profile with the center coordinates regarded as the coordinate origin; Reconstructing the image of the subject using the image intensity profile after coordinate correction; An image generation method, characterized by including the above steps.

8. Irradiating an imaging light to a subject fixedly installed at a predetermined distance from a sample holding plate; While rotating the subject by a predetermined angle each time, the imaging light that has passed through the opening formed in the sample holding plate among the imaging light that has passed through the subject is detected each time of rotation, and an image intensity profile is generated for each rotation angle. In an image generation method for reconstructing an image of the subject using the image intensity profile, Calculating a reference image intensity profile by integrating the image of the subject reconstructed from the image intensity profile in the direction of the angle by which the subject is rotated by the rotating member; For all of the rotation angles, correcting the coordinates of the image intensity profile based on the reference image intensity profile; An image generation method, characterized by including the above steps.

Images