WO2026009290A1 - Electron beam application device and method for controlling same - Google Patents

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

The present invention relates to an electron beam application device that generates an observation image of the inside of a sample using X-rays emitted by irradiating an electron beam onto a metal target as a probe, and a control method for the device.

To observe semiconductor devices, which are becoming increasingly miniaturized, a scanning electron microscope (SEM) is used. This microscope detects electrons emitted from the sample surface while scanning the sample with an electron beam, generating an image of the sample surface. While SEM can observe the sample surface with spatial resolution on the order of nanometers, it is not suitable for observing the interior of the sample.

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 to observe 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 the generation of X-ray tomographic images using X-ray transmission images from multiple directions obtained by irradiating a rotating sample with X-rays from directions perpendicular to the axis of rotation. In other words, the compound microscope of Patent Document 1 can generate not only an SEM image, which is an observation image of the sample surface, but also X-ray transmission images and X-ray tomographic images, which are observation images of the sample's interior.

Japanese Patent Application Laid-Open No. 2006-47206

However, in Patent Document 1, the sample must 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 sample's rotation axis, making it difficult to generate X-ray tomographic images with spatial resolution on the order of nm.

The present invention therefore aims to provide an electron beam application device and a control method thereof that can generate X-ray tomographic images without rotating the sample.

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.

The present invention also provides 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.

The present invention provides an electron beam application device and a control method thereof that can generate X-ray tomographic images without rotating the sample.

FIG. 1 is a diagram showing an example of the overall configuration of an electron beam application apparatus according to a first embodiment. A diagram showing the configuration of a metal target and an X-ray filter. A diagram showing a configuration in which a metal target and an X-ray shield are combined. FIG. 1 is a diagram showing a case where an SEM image is captured by the electron beam application device of the first embodiment. FIG. 1 is a diagram showing another example of the overall configuration of the electron beam application apparatus according to the first embodiment. A diagram showing the relationship between the X-ray focus, the sample, and the detection pixels. FIG. 1 shows X-rays detected at different X-ray focal positions. FIG. 1 is a diagram showing an example of the position of an X-ray focal point for generating an X-ray tomographic image in an arbitrary cross section perpendicular to the XY plane. FIG. 1 is a diagram showing an example of a processing flow according to a first embodiment; FIG. 10 is a diagram showing an example of a display screen according to the first embodiment; FIG. 10 is a diagram showing an example of the position of the X-ray focal spot that is sparsely controlled. FIG. 1 shows an example of two-dimensional arrangement of patterned X-ray focal positions. FIG. 1 is a diagram showing an example of a configuration for irradiating an electron beam with pulses. FIG. 10 is a diagram showing another example of a configuration for irradiating an electron beam with pulses. FIG. 10 is a diagram showing an example of the overall configuration of an electron beam application apparatus according to a second embodiment. FIG. 10 is a diagram showing a case where ion beam processing and SEM imaging are performed in the electron beam application device of Example 2. FIG. 10 is a diagram showing an example of the overall configuration of an electron beam application apparatus according to a third embodiment. FIG. 10 is a diagram showing another example of the overall configuration of the electron beam application apparatus according to the third embodiment.

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

An example of the overall configuration of the electron beam application device of Example 1 will be described using Figure 1. The electron beam application device includes a sample stage 3, an SEM mirror body 11, an X-ray imaging system 21, an electron detector 17, and a controller 4. The sample stage 3 holds the sample 1, which is the object of observation, and adjusts the position and tilt of the sample 1.

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 inside. The electron source 12 emits an electron beam 20 along the 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 top surface of the sample 1 by a magnetic field or electric field.

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 X-rays 25 are emitted 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, the larger the area where the electron beam 20 scatters within the metal target 22, the larger the size of the X-ray focal point 24. Therefore, it is preferable that the thickness of the metal target 22 be, for example, 1 μm or less. The metal target 22 may be combined with an X-ray filter or X-ray shielding.

Using Figure 2A, we will explain the configuration combining a metal target 22 and an X-ray filter 27. 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. Continuous X-rays have a broad energy distribution up to the acceleration energy of the electron beam 20, while 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 placed between the metal target 22 and the sample 1, and by using the X-ray filter 27 to block X-rays 25 in unnecessary energy bands, X-rays 25 in the desired energy band are irradiated onto the sample 1. Note that 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.

Using Figure 2B, we will explain the configuration combining a metal target 22 and an X-ray shield 28. Because the X-rays 25 emitted from the X-ray focal point 24 spread radially, they are not suitable for measuring X-ray diffraction (XRD) of a localized 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 by the X-rays 25 is limited by the X-ray shield 28, thereby measuring X-ray diffraction of a localized 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. Return to the explanation of Figure 1.

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 it away from the path of the electron beam 20. By moving the target support part 23 on metal rails, the position at which the metal target 22 is placed can be more reproducible. Furthermore, if the target support part 23 is made of copper or other materials with high thermal conductivity, the heat generated in the metal target 22 by irradiation with the electron beam 20 can be more easily dissipated via the target support part 23.

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. An X-ray transmission image of the sample 1 is generated based on the detection signals transmitted from the X-ray detector 26, whose 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 have detection pixels arranged radially and circumferentially.

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 Figure 3. An SEM image of the sample 1 is generated based on the 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. Multiple 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.

The controller 4 is a device that controls the operation of each part, and is, for example, a general-purpose computer. The computer has 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 the detection signals sent 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 signals sent from the X-ray detector 26, and an SEM image of the sample 1 is generated based on the detection signals sent 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 Figures 1 and 3.

Another example of the overall configuration of the electron beam application apparatus of Example 1 will be described using Figure 4. In Figure 4, an acceleration tube 18 is provided to which a positive potential, for example +10 kV, is applied relative 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 electron source 12 side. The same potential as that of the acceleration tube 18 is applied to the electron detector 17 in Figure 4. By applying a positive potential relative to the sample 1 to the acceleration tube 18 and electron detector 17, even signal electrons 16 with energies 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 Figure 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 onto the metal target 22, i.e., the beam diameter and beam shape.

In order to generate an X-ray tomographic image of sample 1, it is necessary to acquire X-ray transmission images from multiple directions. Below, we will explain the X-ray transmission images from multiple directions acquired by the electron beam application device of Example 1.

The relationship between the X-ray focal point 24, the region of interest 2 on 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 orthogonal to the Z axis and orthogonal to each other are the X axis and the Y axis. Note that Figure 5 shows the XZ plane where Y = 0, and the Z coordinates of the metal target 22, the sample 1, and the X-ray detector 26 are _zT , _zS , and _zD , respectively. Furthermore, the distance L _T between the metal target 22 and the sample 1 can be calculated from _zT and _zS , and the distance L _D between the sample 1 and the X-ray detector 26 can be calculated from _zS and _zD , respectively. 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:

M=( _LD + _LT )/ _LT ... (Formula 1)
The detection pixels of the X-ray detector 26 have an X-direction length of d _{p — x} and a Y-direction length of d _{p — y} , and are arranged in 2N _x rows in the X direction and 2N _y rows in the Y direction.

When the coordinates of the X-ray focal point 24, which is the point irradiated with the deflected electron beam 20, are ( _xT , 0, _zT ) and the coordinates of the region of interest 2 on the sample 1 are ( _xS , 0, _zS ), the angle θx that the X-rays emitted from the X-ray focal point 24 and transmitted through the region of interest 2 make with the Z axis is given by the following equation:

θx=arctan {(x _S - x _T )/L _T }... (Formula 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.

The X coordinate _xD of the coordinates ( _xD , 0, _zD ) of the detection pixel reached by the X-rays that have passed through the region of interest 2 of the sample 1 at a transmission angle θx is given by the following equation.

x _D = x _T + (L _D + L _T )・tanθx… (Formula 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, not only in the XZ plane where Y=0 illustrated in Fig. 5, but also in the XZ plane where Y≈0 or any YZ plane, by changing the position of the X-ray focal point 24, it is possible to control the transmission angle of the X-rays that pass through the region of interest 2 and identify detection pixels that detect the X-rays.

The X-rays detected at each different X-ray focal position will be described using Figure 6. Figure 6 shows the metal target 22, sample 1, and X-ray detector 26 arranged in the same manner as in Figure 5, and further shows by solid lines the X-rays that pass through the region of interest 2 at coordinates (0, 0, z _S ) and are incident on the center of each detection pixel of the X-ray detector 26. Note that the X-rays detected by each detection pixel of the X-ray detector 26 include not only the X-rays shown by the solid lines, but also X-rays that are incident at a position shifted by the X-direction length dp_x of the detection pixel.

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, resulting in X-ray transmission images from multiple directions. 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, or algebraic methods such as algebraic image reconstruction.

The range Ω of transmission angles detected by the X-ray imaging system illustrated in Figure 6 is given by the following formula:

Ω=2・arctan {(d _{p_x}・N _x )/ _LD } … (Formula 4)
When generating an X-ray tomographic image, the transmission angle range Ω is preferably 180° or more. However, according to (Equation 4), when d _{p — x} = 100 μm, N _x = 1000, and L _D = 50 mm, Ω = 90°, which is less than 180°. If the transmission angle range Ω is less than 180°, a machine learning processor such as NeRF (Neural Radiance Field) may be used to generate a high-resolution X-ray tomographic image.

Incidentally, distortion and deflection aberrations that occur as a result of the deflection of the electron beam 20 have an adverse effect on the generation of X-ray tomographic images. Distortion aberrations occur 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 in the irradiation position of the electron beam 20. Deflection aberrations occur when the beam shape of the electron beam 20 is distorted asymmetrically, so an aberration corrector that corrects deflection aberrations may be placed on the path of the electron beam 20. An aberration corrector is, for example, a deflector used in a moving objective lens (MOL).

Furthermore, the generation of X-ray tomographic images is not limited to the XZ plane where Y=0 as in Figure 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 Figure 7. In other words, by acquiring an X-ray transmission image at the position of the X-ray focal point 24 aligned on the dotted line in Figure 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 multiple cross sections perpendicular to the XY plane, it is also possible to generate an X-ray tomographic image in a cross section parallel to the XY plane.

Using Figure 8, an example of the processing flow of Example 1 will be explained step by step.

(S801)
A sample 1 to be observed is set on a sample stage 3 .

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

Which of the SEM image or X-ray transmission image is used is selected on the display screen shown in Figure 8. The display screen in Figure 8 has a condition setting section 31 and an image display section 32. The condition setting section 31 selects the image to be observed from the SEM image, X-ray transmission image, and X-ray tomographic image, and also sets the acceleration voltage and irradiation current of the electron beam 20. It also displays whether the metal target 22 is on the path of the electron beam 20. The image display section 32 displays the SEM image, X-ray transmission image, and X-ray tomographic image.

(S803)
The controller 4 acquires X-ray transmission images from a plurality of 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 a plurality of directions are acquired.

(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.

In order 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 it takes to generate the X-ray tomographic image. Therefore, X-ray transmission images may be acquired sparsely from multiple directions, and the X-ray tomographic image may be generated by utilizing restoration processing using 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, shortening the time required to generate the X-ray tomographic image, and by utilizing restoration processing using compressed sensing, the degradation of the spatial resolution of the generated X-ray tomographic image is suppressed.

Figure 10 shows an example of the position of an X-ray focal spot 24 under sparse control. While the number of X-ray focal spots 24 without sparse control is 64 (= 8 x 8), the number of X-ray focal spots 24 under sparse control is indicated by black circles and is 6. In other words, with sparse control, the number of acquired X-ray transmission images is reduced to approximately 1/10 (≒ 6/64), and the number of acquired X-ray transmission images is also reduced to approximately 1/10, thereby shortening the time required to acquire X-ray transmission images. Furthermore, because the number of times the electron beam 20 is irradiated onto the metal target 22 is reduced, the amount of heat generated by the metal target 22 can be reduced.

Furthermore, the time required for the restoration process using compressed sensing may be shortened by patterning the combinations of sparsely controlled X-ray focal points 24 positions and repeatedly using the patterned combinations of positions. For example, if the pattern of combinations of X-ray focal points 24 positions illustrated in Figure 10 is arranged two-dimensionally as shown in Figure 11, the restoration process within the pattern can be repeatedly used, thereby shortening the time required for the restoration process.

In order to sparsely control the position of the X-ray focal point 24, it is necessary to irradiate the metal target 22 with pulses of electron beam 20. In other words, when deflecting the electron beam 20 from position P1 of one X-ray focal point 24 to position P2 of another X-ray focal point 24, if the electron beam 20 is continuously irradiated, X-rays will also be emitted between positions P1 and P2, and the X-rays detected during this time will become noise, adversely affecting the generated X-ray tomographic image.

An example of a configuration for irradiating the electron beam 20 in pulses will be described using Figure 12. In Figure 12, a blanker electrode 35 and an aperture 37 are provided downstream of the electron source 12 and 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.

With the configuration of Figure 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 Figure 12, it is possible to use existing high-brightness electron sources such as cold cathode electron guns and Schottky electron guns.

Using Figure 13, another example of a configuration for pulsed irradiation of an electron beam 20 will be described. In Figure 13, a photoelectric film 42, a transparent substrate 41, a condensing 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 transparent window provided in the SEM body 11 and allows the pulsed light 45 to pass through. The condensing 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 pulsed light 45, and is obtained, for example, by using highly doped p-type GaAs as the active layer and adsorbing cesium and oxygen onto its surface. 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 the pulsed electron beam 47 is accelerated by the potential difference between V0 and V1.

With the configuration of Figure 13, the pulsed electron beam 47 can be irradiated onto the metal target 22 at the same time that the pulsed light 45 is emitted from the pulsed light source 44. Furthermore, with the configuration of Figure 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.

Furthermore, in order to correct distortion that occurs due to deflection of the pulsed electron beam 47 by the deflector 14, the position at which the pulsed light 45 is irradiated may be controlled. When the pulsed light 45 is irradiated onto the photoelectric film 42 while shifted from the optical axis 19 of the SEM, the pulsed electron beam 47 emitted from the photoelectric film 42 is also emitted while shifted from the optical axis 19 of the SEM, and the pulsed electron beam 47 is deflected by the electric field formed between the photoelectric film 42 and the anode 13. Therefore, distortion can be 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.

To control the position where the pulsed light 45 is irradiated, a galvanometer mirror or the like placed between the pulsed light source 44 and the photoelectric film 42 is used. In other words, the position where the pulsed light 45 is irradiated is controlled by adjusting the mirror angle of the galvanometer mirror. In addition to a galvanometer mirror, the irradiation position and spot shape of the pulsed light 45 may also be controlled by a spatial phase modulator.

When repeating the combination of positions of the patterned X-ray focal point 24 as shown in Figure 11, a galvanometer mirror is used to control the position of the X-ray focal point 24 within the pattern, and a deflector 14 is used to move the pattern. In other words, by controlling the galvanometer mirror and deflector 14 in combination, the time required to generate a high-resolution X-ray tomographic image can be shortened.

Furthermore, if 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, making it possible to suppress deflection aberration. Return to the explanation of Figure 8.

(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, where the observation position is reset.

(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, where a new specimen 1 is set on the specimen stage 3. If the specimen 1 is not to be replaced, the process flow ends.

According to the processing flow illustrated in Figure 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, making it possible to generate X-ray tomographic images without rotating the sample 1. Furthermore, an SEM image can be obtained by moving the metal target 22 away from the path of the electron beam 20.

An example of the overall configuration of the electron beam application device of Example 2 will be described using Figure 14. Note that Figure 14 is the same as Figure 4 except that a focused ion beam device 51 has been added, so the following description will mainly focus on the focused ion beam device 51.

The focused ion beam device 51 is a device that generates an ion beam used for processing and observing the sample 1. In other words, 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 by, for example, cutting it into any shape using the sputtering phenomenon, or to generate an observation image by detecting charged particles emitted from the sample 1. Note that the observation image generated by detecting charged particles emitted in conjunction with ion beam irradiation is called a SIM (Scanning Ion Microscope) image. It is also preferable that the observation area of the sample 1 be positioned so that it overlaps the intersection of the optical axis 53 of the focused ion beam device and the optical axis 19 of the SEM.

Using Figure 15, the arrangement when processing the sample 1 with the ion beam 52 will be explained. 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 has been generated.

By repeatedly processing the sample 1 with the ion beam 52 and observing it with SEM and SIM images, and creating a tomographic image of the sample 1 from multiple SEM and SIM images, it is possible to compare the X-ray tomographic image created in advance with the tomographic image created from multiple SEM and SIM images. By comparing X-ray tomographic images with each other, artifacts contained in the X-ray tomographic image become clear, and the parameters used to create the X-ray tomographic image can be adjusted based on the comparison results to reduce the artifacts.

An example of the overall configuration of the electron beam application apparatus of Example 3 will be described using Figure 16. Note that Figure 16 adds a pump light source 62 to Figure 1, so the following description will mainly focus on the pump light source 62.

The pump light source 62 is a device that emits pump light 61 used to excite the sample 1. In other words, by irradiating the sample 1 with 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 while the sample 1 is excited. 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 target support 23 are positioned so as not to block the optical path of the pump light 61.

Furthermore, when irradiating the metal target 22 with a pulsed electron beam 47 using the configuration of Figure 13, 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 excitation of the sample 1 is not limited to that using the pump light 61.

Another example of the overall configuration of the electron beam application device of Example 3 will be described using Figure 17. Note that Figure 17 adds a needle electrode 71 and a voltage source 72 to Figure 1, so the following description will mainly focus on the needle electrode 71 and the voltage source 72.

The needle-shaped electrode 71 is an electrode used to apply a voltage to a localized area of the sample 1, and has an extremely thin needle shape. The needle-shaped electrode 71 is positioned in the localized area of the sample 1 using an SEM image.

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.

The sample 1 is excited by applying a periodic voltage output from the voltage source 72 to a localized region of the sample 1 using the needle electrode 71. Since the localized region of the sample 1 is represented by an equivalent circuit consisting of a resistor, capacitor, and inductor, the period of the voltage output from the voltage source 72 may be set according to the resonant frequency of that equivalent circuit. 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.

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

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 electrode, 72: Voltage source.

Claims (12)

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,
The electron beam application device is characterized in that 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. The electron beam application apparatus according to claim 1,
Electron beam application equipment further comprising a detector for monitoring a convergence state of the electron beam incident on the metal target. 2. The electron beam application apparatus according to claim 1,
The electron beam application device is 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. 2. The electron beam application apparatus according to claim 1,
The electron beam application device is characterized in that the controller generates the X-ray tomographic image after performing a restoration process using compressed sensing on the X-ray transmission image obtained by sparsely controlling the position of the X-ray focal point. 5. The electron beam application apparatus according to claim 4,
The electron beam application device is characterized in that the controller patterns a combination of positions of the X-ray focal points that are sparsely controlled, and repeatedly uses the patterned combination of positions. 2. The electron beam application apparatus according to claim 1,
The electron beam application device further comprises a pulsing unit that pulses the electron beam incident on the metal target. 7. The electron beam application apparatus according to claim 6,
an electron beam application device, 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 the electron beam does not pass through the hole when a pulse voltage is applied thereto. 7. The electron beam application apparatus according to claim 6,
The electron beam application device is characterized in that the pulsating unit has a pulsed light source that emits pulsed light, and a photoelectric film that emits a pulsed electron beam when irradiated with the pulsed light. 9. The electron beam application apparatus according to claim 8,
The electron beam application device is characterized in that the pulsing unit further has a galvanometer mirror that controls the position of the pulsed light irradiated onto the photoelectric film so as to cancel out distortion aberration that occurs when the electron beam is deflected by the deflector. 7. The electron beam application apparatus according to claim 6,
further comprising an excitation unit that excites the sample,
Electron beam application equipment, characterized in that the controller synchronizes excitation of the sample by the excitation unit with incidence of the electron beam pulsed by the pulsation unit onto the metal target. 2. The electron beam application apparatus according to claim 1,
a focused ion beam device for generating an ion beam for processing the sample;
the controller creates a tomographic image of the sample using a plurality of surface observation images obtained by repeating the processing using the ion beam and the acquisition of surface observation images of the sample, and adjusts parameters used to generate the X-ray tomographic image based on a comparison result between the tomographic image and the X-ray tomographic image. A control method for an electron beam application apparatus including 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 of the components, comprising:
a control method characterized in that the controller changes the position of the X-ray focal point, which is the point at which X-rays are emitted from the metal target, by controlling the deflector, 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.