Electron beam application device and method for controlling same

Abstract

The purpose of the present invention is to provide an electron beam application device and a method for controlling the same, said electron beam application device being capable of generating an X-ray tomographic image without rotating a sample. This electron beam application device includes: an electron source that emits an electron beam; a deflector that deflects the electron beam; a metal target that, due to the electron beam impinging thereupon, releases X-rays emitted at the sample; an X-ray detector that detects the X-rays transmitted through the sample; and a controller that controls each component. The controller: controls the deflector and thereby changes the position of the X-ray focal point, which is the point at which the X-rays are released by the metal target; and generates an X-ray tomographic image of the sample on the basis of detection signals outputted from the X-ray detector according to the position of the X-ray focal point.

Description

Electron beam application device and its control method

[0001] The present invention relates to an electron beam application apparatus for generating an observation image of the inside of a sample using X-rays emitted by making an electron beam incident on a metal target as a probe, and a control method thereof.

[0002] To observe increasingly miniaturized semiconductor devices, scanning electron microscopes (SEMs) are used. These microscopes generate images of the sample surface by detecting electrons emitted from the surface while scanning the sample with an electron beam. While SEMs can observe the surface of a sample with a spatial resolution on the order of nanometers, they are not suitable for observing the interior of a sample.

[0003] Patent Document 1 discloses a compound microscope in which a metal target is moved along the path of an electron beam irradiated onto the sample in an SEM used for observing the surface of a sample, and an X-ray transmission image of the sample is generated using X-rays emitted from the metal target. Patent Document 1 also discloses generating an X-ray tomographic image using X-ray transmission images from multiple directions obtained by irradiating a rotating sample with X-rays from directions perpendicular to the rotation axis. That is, the compound microscope of Patent Document 1 can generate not only an SEM image, which is an observation image of the surface of the sample, but also an X-ray transmission image and an X-ray tomographic image, which are observation images of the interior of the sample.

[0004] Japanese Patent Application Laid-Open No. 2006-47206

[0005] However, in Patent Document 1, the sample needs to be rotated to generate an X-ray tomographic image, and the spatial resolution of the generated X-ray tomographic image depends on the accuracy of the rotation axis of the sample, making it difficult to generate an X-ray tomographic image with a spatial resolution on the order of nm.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an electron beam application apparatus capable of generating an X-ray tomographic image without rotating a sample, and a control method thereof.

[0007] In order to achieve the above object, the present invention provides an electron beam application device comprising an electron source that emits an electron beam, a deflector that deflects the electron beam, a metal target that emits X-rays that are irradiated onto a sample by the incidence of the electron beam, an X-ray detector that detects the X-rays that have passed through the sample, and a controller that controls each component, wherein the controller controls the deflector to change the position of the X-ray focal point, which is the point at which X-rays are emitted from the metal target, and generates an X-ray tomographic image of the sample based on a detection signal output from the X-ray detector in accordance with the position of the X-ray focal point.

[0008] The present invention also provides a control method for an electron beam application apparatus comprising an electron source that emits an electron beam, a deflector that deflects the electron beam, a metal target that emits X-rays that are irradiated onto a sample by the incidence of the electron beam, an X-ray detector that detects the X-rays that have passed through the sample, and a controller that controls each component, wherein the controller controls the deflector to change the position of the X-ray focal point, which is the point at which X-rays are emitted from the metal target, and generates an X-ray tomographic image of the sample based on a detection signal output from the X-ray detector in accordance with the position of the X-ray focal point.

[0009] According to the present invention, it is possible to provide an electron beam application apparatus capable of generating an X-ray tomographic image without rotating a sample, and a control method thereof.

[0010] FIG. 1 is a diagram showing an example of the overall configuration of an electron beam application apparatus of Example 1; FIG. 1 shows a configuration in which a metal target and an X-ray filter are combined; FIG. 1 shows a configuration in which a metal target and an X-ray shield are combined; FIG. 2 is a diagram showing a case in which an SEM image is taken with the electron beam application apparatus of Example 1; FIG. 3 is a diagram showing another example of the overall configuration of the electron beam application apparatus of Example 1; FIG. 4 is a diagram showing the relationship between the X-ray focus, the sample, and the detection pixel; FIG. 5 is a diagram showing X-rays detected for each different X-ray focus position; FIG. 6 is a diagram showing an example of the X-ray focus position for generating an X-ray tomographic image in an arbitrary cross section perpendicular to the XY plane; FIG. 7 is a diagram showing an example of the processing flow of Example 1; FIG. 8 is a diagram showing an example of the display screen of Example 1;

[0011] An embodiment of an electron beam application apparatus according to the present invention will now be described with reference to the accompanying drawings. The electron beam application apparatus generates an observation image of the sample surface by detecting signal electrons emitted by irradiating a sample with an electron beam, and also generates an observation image of the sample interior by irradiating the sample with X-rays.

[0012] An example of the overall configuration of the electron beam application apparatus of Example 1 will be described with reference to Figure 1. The electron beam application apparatus includes a sample stage 3, an SEM microscope body 11, an X-ray imaging system 21, an electron detector 17, and a controller 4. The sample stage 3 holds a sample 1 to be observed, and adjusts the position and tilt of the sample 1.

[0013] The SEM body 11 is evacuated by a vacuum pump (not shown) to a degree of vacuum that prevents the electron beam from scattering, and contains an electron source 12, an anode 13, a deflector 14, and an objective lens 15. The electron source 12 emits an electron beam 20 along an optical axis 19 of the SEM. The anode 13 provides acceleration energy to the electron beam 20 by an applied voltage. The deflector 14 deflects the electron beam 20 by a magnetic field or electric field. The objective lens 15 focuses the electron beam 20 on the upper surface of the sample 1 by a magnetic field or electric field.

[0014] The X-ray imaging system 21 includes a metal target 22, a target support 23, and an X-ray detector 26 for irradiating the sample 1 with X-rays 25 and detecting the X-rays 25 that pass through the sample 1. The metal target 22 is a plate made of a heavy metal with a high melting point, such as molybdenum or tungsten, and emits X-rays 25 when irradiated with an electron beam 20. The X-rays 25 are emitted from an X-ray focal point 24, which is the point at which the electron beam 20 is irradiated. Since a smaller size of the X-ray focal point 24 is preferable, when emitting X-rays 25 from the metal target 22, the electron beam 20 is focused on the upper surface of the metal target 22 by the objective lens 15 to a size on the order of nanometers. Furthermore, since the larger the area where the electron beam 20 scatters in the metal target 22, the larger the size of the X-ray focal point 24 becomes, the thickness of the metal target 22 is preferably 1 μm or less. The metal target 22 may be combined with an X-ray filter or an X-ray shield.

[0015] A configuration combining a metal target 22 and an X-ray filter 27 will be described using FIG. 2A . The X-rays 25 emitted from the metal target 22 include continuous X-rays generated by bremsstrahlung and characteristic X-rays generated by electron transitions within atoms. The continuous X-rays have a broad energy distribution up to the acceleration energy of the electron beam 20, while the characteristic X-rays have an energy value specific to each atom. The penetrating power of the X-rays 25 passing through the sample 1 and the detection sensitivity of the X-ray detector 26 depend on the energy of the X-rays 25. Therefore, an X-ray filter 27 is disposed between the metal target 22 and the sample 1, and the X-rays 25 in an unnecessary energy band are blocked by the X-ray filter 27, thereby irradiating the sample 1 with X-rays 25 in a desired energy band. The X-ray filter 27 is made of, for example, copper or aluminum, and different X-ray filters 27 may be used depending on the application.

[0016] A configuration combining a metal target 22 and an X-ray shield 28 will be described using Figure 2B. Because X-rays 25 emitted from the X-ray focal point 24 spread radially, they are not suitable for measuring X-ray diffraction (XRD) in a local area of ​​the sample 1. Therefore, an X-ray shield 28 with holes 29 is placed between the metal target 22 and the sample 1, and the area irradiated with the X-rays 25 is limited by the X-ray shield 28, thereby measuring X-ray diffraction in a local area of ​​the sample 1. Note that the X-ray shield 28 is made of lead or the like, and the size of the holes 29 may be set depending on the application. Returning to the description of Figure 1.

[0017] The target support part 23 is a member that supports the metal target 22, and moves on metal rails (not shown) to place the metal target 22 on the path of the electron beam 20 or move the metal target 22 away from the path of the electron beam 20. The movement of the target support part 23 on the metal rails improves the reproducibility of the position at which the metal target 22 is placed. Furthermore, if the target support part 23 is made of copper or the like, which has high thermal conductivity, heat generated in the metal target 22 by irradiation with the electron beam 20 can be easily dissipated via the target support part 23.

[0018] The X-ray detector 26 has a plurality of detection pixels that detect X-rays 25 that have passed through the sample 1, and transmits a detection signal from each detection pixel to the controller 4. The detection pixels of the X-ray detector 26 are, for example, rectangular with sides of 100 μm or less, and are arranged in a two-dimensional array of several thousand by several thousand pixels. An X-ray transmission image of the sample 1 is generated based on the detection signals transmitted from the X-ray detector 26 in which the detection pixels are arranged in a two-dimensional array. Note that the X-ray detector 26 is not limited to a grid-like arrangement in which the detection pixels are arranged vertically and horizontally, and may also be one in which the detection pixels are arranged radially and circumferentially.

[0019] The electron detector 17 detects signal electrons 16 such as secondary electrons and backscattered electrons emitted from the sample 1 in response to irradiation with the electron beam 20, and transmits a detection signal to the controller 4. When the signal electrons 16 emitted from the sample 1 are detected, the metal target 22 is moved away from the path of the electron beam 20, as shown in FIG. 3. An SEM image of the sample 1 is generated based on a detection signal transmitted from the electron detector 17 each time the deflector 14 changes the irradiation position of the electron beam 20 on the sample 1. A plurality of electron detectors 17 may be provided so that the secondary electrons and backscattered electrons emitted from the sample 1 can be detected simultaneously and separately.

[0020] The controller 4 is a device that controls the operation of each component, and is, for example, a general-purpose computer. The computer includes a processor such as a CPU (Central Processing Unit) and memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The controller 4 also generates an observation image of the sample 1 based on detection signals transmitted from the X-ray detector 26 and the electron detector 17. That is, an X-ray transmission image of the sample 1 is generated based on the detection signal transmitted from the X-ray detector 26, and an SEM image of the sample 1 is generated based on the detection signal transmitted from the electron detector 17. The position of the electron detector 17 is not limited to being below the objective lens 15 as shown in FIGS. 1 and 3 .

[0021] Another example of the overall configuration of the electron beam application apparatus of the first embodiment will be described with reference to FIG. 4 . In FIG. 4 , an acceleration tube 18 is provided to which a positive potential, e.g., +10 kV, is applied with respect to the sample 1, and an electron detector 17 is disposed within the acceleration tube 18 above the objective lens 15, i.e., on the side of the electron source 12. The same potential as that of the acceleration tube 18 is applied to the electron detector 17 in FIG. 4 . By applying a positive potential with respect to the sample 1 to the acceleration tube 18 and the electron detector 17, even signal electrons 16 having an energy of 100 eV or less can be detected by the electron detector 17 disposed above the objective lens 15. Furthermore, the electron detector 17 illustrated in FIG. 4 detects signal electrons 16 emitted from a metal target 22 disposed on the path of the electron beam 20, making it possible to monitor the convergence state of the electron beam 20 irradiated on the metal target 22, i.e., the beam diameter and beam shape.

[0022] Incidentally, it is necessary to acquire X-ray transmission images from a plurality of directions in order to generate an X-ray tomographic image of the sample 1. Hereinafter, the X-ray transmission images from a plurality of directions acquired by the electron beam application apparatus of the first embodiment will be described.

[0023] The relationship between the X-ray focal point 24, the region of interest 2 of the sample 1, and the detection pixels of the X-ray detector 26 will be described using Figure 5. Figure 5 shows the metal target 22, the sample 1, and the X-ray detector 26 arranged in a coordinate system in which the optical axis 19 of the SEM is the Z axis, and two axes that are perpendicular to the Z axis and perpendicular to each other are the X axis and the Y axis. Note that Figure 5 is an XZ plane where Y = 0, and the Z coordinates of the metal target 22, the sample 1, and the X-ray detector 26 are z Ｔ and Z Ｓ and Z Ｄ In addition, the distance L between the metal target 22 and the sample 1 Ｔ haz Ｔ and Z Ｓ From this, the distance L between the sample 1 and the X-ray detector 26 Ｄ haz Ｓ and Z Ｄ and the magnification ratio M of the X-ray transmission image generated based on the detection signal transmitted from the X-ray detector 26 is given by the following equation:

[0024] M = (L Ｄ +L Ｔ) / L Ｔ ... (Equation 1) The detection pixel of the X-ray detector 26 has a length in the X direction of d ｐ_ｘ , the length in the Y direction is d ｐ_ｙ and 2N in the X direction. ｘ pcs, 2N in Y direction ｙ The pieces are arranged.

[0025] The coordinates of the X-ray focal point 24, which is the point where the deflected electron beam 20 is irradiated, are (x Ｔ , 0, z Ｔ ), the coordinates of the region of interest 2 of the sample 1 are (x Ｓ , 0, z Ｓ ), the angle θx formed by the X-rays emitted from the X-ray focal point 24 and transmitted through the region of interest 2 with the Z axis is given by the following equation:

[0026] θx=arctan {(x Ｓ -x Ｔ ) / L Ｔ} (Equation 2) That is, by deflecting the electron beam 20 using the deflector 14 to change the position of the X-ray focal point 24, the transmission angle θx of the X-rays passing through the region of interest 2 can be controlled.

[0027] The coordinates of the detection pixel where the X-rays that have passed through the region of interest 2 of the sample 1 at a transmission angle θx reach are (x Ｄ , 0, z Ｄ ) X coordinate x Ｄ is expressed as follows:

[0028] x Ｄ = x Ｔ + (L Ｄ +L Ｔ ) tan θx (Equation 3) That is, it is possible to identify detection pixels that detect X-rays that have passed through the region of interest 2 at a transmission angle θx in accordance with a change in the position of the X-ray focal point 24. Note that by changing the position of the X-ray focal point 24, not only in the XZ plane where Y=0 exemplified in FIG. 5 but also in the XZ plane where Y≈0 or in any YZ plane, it is possible to control the transmission angle of X-rays that pass through the region of interest 2 and identify detection pixels that detect the X-rays.

[0029] The X-rays detected at different X-ray focal positions will be described with reference to FIG. 6. In FIG. 6, the metal target 22, the sample 1, and the X-ray detector 26 arranged in the same manner as in FIG. 5 are shown, and the coordinates (0, 0, z Ｓ ) and incident on the center of each detection pixel of the X-ray detector 26. The X-rays detected by each detection pixel of the X-ray detector 26 include not only the X-rays indicated by the solid lines but also X-rays that are incident at positions shifted by the X-direction length dp_x of the detection pixel.

[0030] X-rays emitted from different X-ray focal points pass through the region of interest 2 at different transmission angles and are detected by the X-ray detector 26, so that X-ray transmission images from multiple directions are acquired. The acquired X-ray transmission images from multiple directions are used to generate X-ray tomographic images. X-ray tomographic images can be generated using known methods, such as analytical methods such as back projection and algebraic methods such as algebraic image reconstruction.

[0031] The range Ω of transmission angles detected by the X-ray imaging system illustrated in FIG.

[0032] Ω=2・arctan {(d ｐ＿ｘ ・N ｘ ) / L Ｄ} (Equation 4) When generating an X-ray tomographic image, it is preferable that the transmission angle range Ω is 180° or more. However, according to (Equation 4), d ｐ＿ｘ = 100 μm, N ｘ = 1000, L Ｄ When the transmission angle range Ω is 50 mm, Ω is 90°, which is less than 180°. When the transmission angle range Ω is less than 180°, a high-resolution X-ray tomographic image may be generated using a machine learning processor such as NeRF (Neural Radiance Field).

[0033] Distortion and deflection aberrations that occur due to the deflection of the electron beam 20 adversely affect the generation of X-ray tomographic images. Distortion occurs when the irradiation position of the electron beam 20 deviates from its original position, so the amount of deflection of the electron beam 20 may be controlled so as to cancel out the deviation of the irradiation position of the electron beam 20. Deflection aberrations occur when the beam shape of the electron beam 20 is asymmetrically distorted, so an aberration corrector that corrects deflection aberrations may be placed on the path of the electron beam 20. The aberration corrector is, for example, a deflector used in a moving objective lens (MOL).

[0034] Furthermore, the generation of X-ray tomographic images is not limited to the XZ plane where Y=0 as in Fig. 6, but can also be performed in any cross section perpendicular to the XY plane by changing the position of the X-ray focal point 24 as illustrated in Fig. 7. That is, by acquiring X-ray transmission images at the positions of the X-ray focal points 24 aligned on the dotted line in Fig. 7, an X-ray tomographic image can be generated in a cross section perpendicular to the XY plane and including the dotted line. Furthermore, by using X-ray tomographic images generated in each of a plurality of cross sections perpendicular to the XY plane, an X-ray tomographic image in a cross section parallel to the XY plane can also be generated.

[0035] An example of the processing flow of the first embodiment will be described for each processing step with reference to FIG.

[0036] (S801) The sample 1 to be observed is set on the sample stage 3.

[0037] (S802) The operator sets the observation position using an SEM image or an X-ray transmission image of the sample 1. When generating an SEM image, the metal target 22 is moved away from the path of the electron beam 20 as shown in FIG. 3, and when generating an X-ray transmission image, the metal target 22 is moved onto the path of the electron beam 20 as shown in FIG.

[0038] Whether an SEM image or an X-ray transmission image is to be used is selected on the display screen exemplified in Fig. 8. The display screen in Fig. 8 has a condition setting section 31 and an image display section 32. In the condition setting section 31, an observation image is selected from an SEM image, an X-ray transmission image, and an X-ray tomographic image, and the acceleration voltage, irradiation current, etc. of the electron beam 20 are set. Also, whether or not the metal target 22 is on the path of the electron beam 20 is displayed. The image display section 32 displays the SEM image, the X-ray transmission image, and the X-ray tomographic image.

[0039] (S803) The controller 4 acquires X-ray transmission images from multiple directions based on the observation position set in S802. That is, the controller 4 changes the position of the X-ray focal point 24 by deflecting the electron beam 20 using the deflector 14, and acquires X-ray transmission images for each different position of the X-ray focal point 24. Since the transmission angle of the X-ray transmission image varies depending on the position of the X-ray focal point 24, X-ray transmission images from multiple directions are acquired.

[0040] (S804) The controller 4 generates an X-ray tomographic image using the X-ray transmission images from multiple directions acquired in S803, and displays the generated X-ray tomographic image on a screen. The display screen shown in FIG. 8 is used to display the X-ray tomographic image, for example. The X-, Y-, and Z-sections of the X-ray tomographic image may be displayed separately. Also, previously acquired observation images may be read out and displayed on the image display unit 32.

[0041] To improve the spatial resolution of the X-ray tomographic image generated in S804, it is preferable to control the transmission angle of the X-ray transmission image more precisely. However, the more precisely the transmission angle is controlled, the more X-ray transmission images are acquired, and the longer the time required to generate the X-ray tomographic image. Therefore, the X-ray tomographic image may be generated by sparsely acquiring X-ray transmission images from multiple directions and utilizing a restoration process by compressed sensing for the multiple sparsely acquired X-ray transmission images. In other words, by sparsely acquiring X-ray transmission images, the number of X-ray transmission images is reduced, thereby shortening the time required to generate the X-ray tomographic image, and by utilizing a restoration process by compressed sensing, a decrease in the spatial resolution of the generated X-ray tomographic image is suppressed.

[0042] FIG. 10 shows an example of the positions of X-ray focal points 24 under sparse control. While the number of X-ray focal points 24 without sparse control is 64 (= 8 × 8), the number of X-ray focal points 24 under sparse control is six, as indicated by black circles. That is, sparse control reduces the number of acquired X-ray transmission images to approximately 1 / 10 (≈ 6 / 64), and the number of acquired X-ray transmission images to approximately 1 / 10, thereby shortening the time required to acquire the X-ray transmission images. Furthermore, the number of times the electron beam 20 is irradiated onto the metal target 22 is reduced, thereby reducing the amount of heat generated by the metal target 22.

[0043] Furthermore, the time required for the restoration process by compressed sensing may be reduced by patterning the combination of sparsely controlled positions of the X-ray focal point 24 and repeatedly using the patterned combination of positions. For example, if the pattern of combinations of positions of the X-ray focal point 24 illustrated in Fig. 10 is arranged two-dimensionally as shown in Fig. 11, the restoration process within the pattern can be repeatedly used, thereby reducing the time required for the restoration process.

[0044] To sparsely control the position of the X-ray focal point 24, it is necessary to irradiate the metal target 22 with the electron beam 20 in pulses. That is, when the electron beam 20 is deflected from a position P1 of one X-ray focal point 24 to a position P2 of another X-ray focal point 24, if the electron beam 20 is continuously irradiated, X-rays are also emitted between the positions P1 and P2, and the X-rays detected during this period become noise, adversely affecting the generated X-ray tomographic image.

[0045] An example of a configuration for pulsed irradiation of the electron beam 20 will be described with reference to Fig. 12. In Fig. 12, a blanker electrode 35 and an aperture 37 are provided downstream of the electron source 12 and the anode 13. The blanker electrode 35 is a pair of parallel plates facing each other, one of which is connected to a blanker power supply 36 and the other is grounded. The blanker power supply 36 outputs a negative pulse voltage at a predetermined timing. The aperture 37 has a hole through which the electron beam 20 passes.

[0046] 12, when the blanker power supply 36 does not output a pulse voltage, the electron beam 20 passes through the aperture 37, and when the blanker power supply 36 outputs a pulse voltage, the electron beam 20 is deflected as shown by the dotted line and does not pass through the aperture 37. In other words, by controlling the output of the blanker power supply 36, the electron beam 20 can be pulsed to produce a pulsed electron beam 38, which can be irradiated onto the metal target 22. Furthermore, with the configuration of FIG. 12, an existing high-brightness electron source such as a cold cathode electron gun or a Schottky electron gun can be used.

[0047] Another example of a configuration for pulsed irradiation of the electron beam 20 will be described using FIG. 13 . In FIG. 13 , a photoelectric film 42, a transparent substrate 41, a condenser lens 43, a viewport 46, and a pulsed light source 44 are provided upstream of the anode 13. The pulsed light source 44 is located outside the SEM body 11 and emits pulsed light 45. The viewport 46 is a transmission window provided in the SEM body 11 and transmits the pulsed light 45. The condenser lens 43 is located between the viewport 46 and the transparent substrate 41 and condenses the pulsed light 45. A photoelectric film 42 is formed on the surface of the transparent substrate 41 facing the anode 13, and the condensed pulsed light 45 is irradiated onto the photoelectric film 42 through the transparent substrate 41. The photoelectric film 42 is a film that emits a pulsed electron beam 47 when irradiated with the pulsed light 45. For example, the photoelectric film 42 can be obtained by adsorbing cesium and oxygen onto the surface of a highly doped p-type GaAs active layer. A voltage V0 is applied to the photoelectric film 42 from a cathode power supply 48, and a voltage V1 is applied to the anode 13 from an anode power supply 49, so that the pulsed electron beam 47 is accelerated by the potential difference between V0 and V1.

[0048] 13, the pulsed electron beam 47 can be irradiated onto the metal target 22 at the same timing as the emission of the pulsed light 45 from the pulsed light source 44. Furthermore, with the configuration of Fig. 13, the irradiation timing of the pulsed electron beam 47 can be controlled on the order of picoseconds, and a pulsed electron beam 47 with brightness equivalent to that of a Schottky electron gun can be obtained.

[0049] The position at which the pulsed light 45 is irradiated may be controlled in order to correct distortion that occurs due to deflection of the pulsed electron beam 47 by the deflector 14. When the pulsed light 45 is irradiated onto the photoelectric film 42 at a position deviated from the optical axis 19 of the SEM, the pulsed electron beam 47 emitted from the photoelectric film 42 is also emitted at a position deviated from the optical axis 19 of the SEM, and therefore the pulsed electron beam 47 is deflected by the electric field formed between the photoelectric film 42 and the anode 13. Therefore, distortion is corrected by controlling the position at which the pulsed electron beam 47 is emitted, i.e., the position at which the pulsed light 45 is irradiated, so that the deflection by the deflector 14 is canceled out by the deflection between the photoelectric film 42 and the anode 13.

[0050] The position irradiated with the pulsed light 45 is controlled by using a galvanometer mirror or the like disposed between the pulsed light source 44 and the photoelectric film 42. That is, the position irradiated with the pulsed light 45 is controlled by adjusting the mirror angle of the galvanometer mirror. In addition to the galvanometer mirror, the irradiation position and spot shape of the pulsed light 45 may also be controlled by a spatial phase modulator.

[0051] 11, when the combination of positions of the patterned X-ray focal point 24 is repeated, a galvanometer mirror is used to control the position of the X-ray focal point 24 within the pattern, and the deflector 14 is used to move the pattern. That is, by controlling the galvanometer mirror and the deflector 14 in combination, the time required to generate a high-resolution X-ray tomographic image can be shortened.

[0052] Furthermore, when the surface of the photoelectric film 42 has a negative electron affinity (NEA), the pulsed electron beam 47 emitted from the photoelectric film 42 has a relatively narrow energy width and small chromatic aberration, so that deflection aberration can be suppressed. Returning to the explanation of FIG.

[0053] (S805) The controller 4 determines whether or not the observation of the sample 1 has been completed. If the observation has been completed, the process proceeds to S806, and if not, the process returns to S802 and the observation position is reset.

[0054] (S806) The controller 4 determines whether or not the specimen 1 to be observed is to be replaced. If the specimen 1 is to be replaced, the process returns to S801, and a new specimen 1 is set on the specimen stage 3. If the specimen 1 is not to be replaced, the process flow ends.

[0055] 8, the position of the X-ray focal point 24 is changed by controlling the deflector 14, and X-ray transmission images with different transmission angles are acquired depending on the position of the X-ray focal point 24, so that an X-ray tomographic image can be generated without rotating the sample 1. In addition, an SEM image can be obtained by moving the metal target 22 away from the path of the electron beam 20.

[0056] An example of the overall configuration of the electron beam application apparatus of Example 2 will be described with reference to Fig. 14. Note that Fig. 14 is obtained by adding a focused ion beam apparatus 51 to Fig. 4, and therefore, the focused ion beam apparatus 51 will be mainly described below.

[0057] The focused ion beam device 51 is a device that generates an ion beam used for processing and observing the sample 1. That is, by irradiating the surface of the sample 1 with a focused ion beam from the focused ion beam device 51, it is possible to process the surface of the sample 1, for example, by grinding it into a desired shape using the sputtering phenomenon, or to generate an observation image by detecting charged particles emitted from the sample 1. Note that an observation image generated by detecting charged particles emitted in association with ion beam irradiation is called a SIM (Scanning Ion Microscope) image. In addition, it is preferable that the observation area of ​​the sample 1 be positioned so as to overlap the intersection of the optical axis 53 of the focused ion beam device and the optical axis 19 of the SEM.

[0058] 15 will be used to explain the arrangement when processing the sample 1 with the ion beam 52. When processing with the ion beam 52, the sample stage 3 is tilted so that the surface of the sample 1 is perpendicular to the optical axis 53 of the focused ion beam device. If the tilted sample stage 3 interferes with the X-ray detector 26, the X-ray detector 26 may be retracted to a position where it does not interfere with the sample stage 3. Processing of the sample 1 with the ion beam 52 is performed after an X-ray tomographic image is generated.

[0059] By repeating the processing of the sample 1 with the ion beam 52 and the observation with SEM images or SIM images, and creating a tomographic image of the sample 1 from the multiple SEM images or SIM images, it is possible to compare the X-ray tomographic image created in advance with the tomographic image created from the multiple SEM images or SIM images. By comparing the X-ray tomographic image with the tomographic image, artifacts contained in the X-ray tomographic image become clear, and therefore the parameters used to create the X-ray tomographic image may be adjusted based on the comparison results so as to reduce the artifacts.

[0060] An example of the overall configuration of an electron beam application apparatus according to the third embodiment will be described with reference to Fig. 16. Since Fig. 16 is obtained by adding a pump light source 62 to Fig. 1, the pump light source 62 will be mainly described below.

[0061] The pump light source 62 is a device that emits pump light 61 used to excite the sample 1. That is, by irradiating the sample 1 with the pump light 61 from the pump light source 62, it is possible to generate an SEM image, an X-ray transmission image, or an X-ray tomographic image in an excited state of the sample 1. The wavelength of the pump light 61 is selected according to the band gap of the semiconductor contained in the sample 1, etc. The metal target 22 and the target support 23 are positioned so as not to block the optical path of the pump light 61.

[0062] 13 , when the metal target 22 is irradiated with the pulsed electron beam 47, the irradiation timing of the pump light source 62 and the pulsed light source 44 may be synchronized. By synchronizing the irradiation timing, an X-ray tomographic image of the sample 1 during excitation can be accurately generated. Note that the excitation of the sample 1 is not limited to that by the pump light 61.

[0063] Another example of the overall configuration of the electron beam application apparatus of Example 3 will be described with reference to Fig. 17. Note that Fig. 17 is obtained by adding a needle electrode 71 and a voltage source 72 to Fig. 1, and therefore the following description will mainly focus on the needle electrode 71 and the voltage source 72.

[0064] The needle-like electrode 71 is an electrode for applying a voltage to a local region of the sample 1, and has an extremely thin needle shape. The needle-like electrode 71 is positioned in the local region of the sample 1 using an SEM image.

[0065] The voltage source 72 is an arbitrary waveform generator such as a function generator, and outputs a periodic voltage. The voltage source 72 is connected to the needle electrode 71.

[0066] The sample 1 is excited by applying a periodic voltage output from the voltage source 72 to a local region of the sample 1 by the needle electrode 71. Note that since the local region of the sample 1 is represented by an equivalent circuit consisting of a resistor, a capacitor, and an inductor, the period of the voltage output from the voltage source 72 may be set according to the resonant frequency of the equivalent circuit. Note that if the X-rays 25 irradiated onto the sample 1 are pulsed, the reference signal of the voltage source 72 and the signal for pulsing the electron beam 20 may be synchronized. By synchronizing the two signals, an X-ray tomographic image of the sample 1 during excitation can be accurately generated.

[0067] The above describes the embodiments of the present invention. The present invention is not limited to the above embodiments, and the components can be modified and embodied without departing from the spirit of the invention. Furthermore, multiple components disclosed in the above embodiments may be combined as appropriate. Furthermore, some components may be omitted from all the components shown in the above embodiments.

[0068] 1: sample, 2: area of ​​interest, 3: sample stage, 4: controller, 11: SEM body, 12: electron source, 13: anode, 14: deflector, 15: objective lens, 16: signal electrons, 17: electron detector, 18: acceleration tube, 19: SEM optical axis, 20: electron beam, 21: X-ray imaging system, 22: metal target, 23: target support, 24: X-ray focus, 25: X-ray, 26: X-ray detector, 27: X-ray filter, 28: X-ray shield, 29: hole, 31: condition setting unit, 32: image display unit, 35: blanker electrode, 36: blanker power supply, 37: aperture, 38: pulsed electron beam, 41: transparent substrate, 42: photoelectric film, 43: condenser lens, 44: pulsed light source, 45: pulsed light, 46: viewport, 47: pulsed electron beam, 48: cathode power supply, 49: anode power supply, 51: focused ion beam device, 52: ion beam, 53: optical axis of focused ion beam device, 61: pump light, 62: pump light source, 71: needle-shaped electrode, 72: voltage source.

Claims

1. An electron beam application device comprising an electron source that emits an electron beam, a deflector that deflects the electron beam, a metal target that emits X-rays that are irradiated onto a sample by the incidence of the electron beam, an X-ray detector that detects the X-rays that have passed through the sample, and a controller that controls each component, wherein the controller controls the deflector to change the position of the X-ray focal point, which is the point at which X-rays are emitted from the metal target, and generates an X-ray tomographic image of the sample based on a detection signal output from the X-ray detector in accordance with the position of the X-ray focal point.

2. An electron beam application device according to claim 1, further comprising a detector for monitoring the convergence state of the electron beam incident on the metal target.

3. An electron beam application device according to claim 1, characterized in that the controller generates an X-ray tomographic image in a cross section parallel to the metal target based on X-ray tomographic images generated in each of a plurality of cross sections perpendicular to the metal target.

4. An electron beam application device as described in claim 1, characterized in that the controller performs a restoration process using compressed sensing on an X-ray transmission image obtained by sparsely controlling the position of the X-ray focal point, and then generates the X-ray tomographic image.

5. An electron beam application device according to claim 4, characterized in that the controller patterns the combinations of positions of the X-ray focal points that are sparsely controlled, and repeatedly uses the patterned combinations of positions.

6. An electron beam application device according to claim 1, further comprising a pulsing unit for pulsating the electron beam incident on the metal target.

7. An electron beam application device according to claim 6, wherein the pulsing unit comprises an aperture having a hole through which the electron beam passes, and a blanker electrode that deflects the electron beam so that it does not pass through the hole when a pulse voltage is applied.

8. An electron beam application device according to claim 6, characterized in that the pulsing unit has a pulsed light source that emits pulsed light, and a photoelectric film that emits pulsed electron beams when irradiated with the pulsed light.

9. An electron beam application device according to claim 8, wherein the pulsing unit further comprises a galvanometer mirror for controlling the position of the pulsed light irradiated onto the photoelectric film so as to cancel out distortion aberrations that occur when the electron beam is deflected by the deflector.

10. An electron beam application device according to claim 6, further comprising an excitation unit for exciting the sample, wherein the controller synchronizes the excitation of the sample by the excitation unit with the incidence of the electron beam pulsed by the pulsation unit onto the metal target.

11. An electron beam application apparatus according to claim 1, further comprising a focused ion beam device that generates an ion beam for processing the sample, wherein the controller creates a tomographic image of the sample using a plurality of surface observation images obtained by repeating processing with the ion beam and obtaining surface observation images of the sample, and adjusts parameters used to generate the X-ray tomographic image based on the results of comparing the tomographic image with the X-ray tomographic image.

12. A control method for an electron beam application device comprising an electron source that emits an electron beam, a deflector that deflects the electron beam, a metal target that emits X-rays that are irradiated onto a sample by the incidence of the electron beam, an X-ray detector that detects the X-rays that have passed through the sample, and a controller that controls each component, wherein the controller controls the deflector to change the position of the X-ray focal point, which is the point at which X-rays are emitted from the metal target, and generates an X-ray tomographic image of the sample based on a detection signal output from the X-ray detector in accordance with the position of the X-ray focal point.

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