Charged particle beam apparatus and analysis method

Abstract

To provide a charged particle beam apparatus capable of shortening the acquisition time of a feature image.SOLUTION: In a charged particle beam apparatus according to the present invention, an image acquisition unit repeatedly performs processing for selecting one mode from among a plurality of modes for acquiring a feature image on the basis of a ratio of a region of a feature object occupying a field of view in an already acquired sample image, and processing for acquiring a feature image in the selected mode, thereby acquiring a plurality of feature images. The plurality of modes include a first mode in which a sample is scanned at a first scan speed to capture a sample image and a feature image is obtained by trimming the captured sample image, and a second mode in which a sample is scanned at a second scan speed faster than the first scan speed to capture a sample image, and a region of the feature object in the captured sample image is scanned at a third scan speed slower than the second scan speed to capture the feature image.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a charged particle beam device and an analysis method. [Background technology]

[0002] Particle analysis using a scanning electron microscope (SEM) or an electron probe microanalyzer (EPMA) is known.

[0003] For example, Patent Document 1 discloses a particle analysis method in which a backscattered electron image or a secondary electron image is acquired, particles are extracted using a contrast threshold value previously set using a standard sample or the like, characteristic X-rays are measured using an energy dispersive X-ray spectrometer, and the particles are classified using the intensity value or concentration value, and measurements are repeated until all measurements within a predetermined field of view are completed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-148499 Summary of the Invention [Problem to be solved by the invention]

[0005] In particle analysis, particle images are repeatedly acquired to analyze a large number of particles, which requires long measurement times to acquire particle images. [Means for solving the problem]

[0006] One aspect of the charged particle beam device according to the present invention is a measurement unit that scans the sample with a charged particle beam to capture an image of the sample; an image acquisition unit that acquires a plurality of sample images taken in a plurality of regions of the sample and acquires a feature image that is an image of a feature contained in the sample from each of the plurality of sample images; an analysis unit that acquires information about the feature object based on the feature image; Including, The image acquisition unit selecting one mode from a plurality of modes for acquiring the feature image based on the proportion of the area of ​​the feature in the field of view in the acquired sample image; acquiring the feature image in a selected mode; to obtain a plurality of the characteristic images; The plurality of modes include: a first mode in which the sample is scanned at a first scan speed to capture a sample image, and the captured sample image is trimmed to acquire the characteristic image; a second mode in which the sample is scanned at a second scan speed faster than the first scan speed to capture a sample image, and a region of the feature in the captured sample image is scanned at a third scan speed slower than the second scan speed to capture the feature image; Includes.

[0007] Such a charged particle beam device can shorten the time required to acquire a characteristic image.

[0008] One aspect of the analysis method according to the present invention is It is an analytical method in a charged particle beam device that scans a sample with a charged particle beam to capture a sample image. hand, acquiring a plurality of sample images photographed in a plurality of regions of the sample, and acquiring a feature image, which is an image of a feature contained in the sample, from each of the plurality of sample images; acquiring information about the feature based on the feature image; Including, The step of acquiring the characteristic image includes: selecting one mode from a plurality of modes for acquiring the feature image based on a proportion of the area of ​​the feature in a field of view in an acquired sample image; acquiring said characteristic image in a selected mode; to obtain a plurality of the characteristic images; The plurality of modes include: a first mode in which the sample is scanned at a first scan speed to capture a sample image, and the captured sample image is trimmed to acquire the characteristic image; a second mode in which the sample is scanned at a second scan speed faster than the first scan speed to capture a sample image, and a region of the feature in the captured sample image is scanned at a third scan speed slower than the second scan speed to capture the feature image; Includes.

[0009] Such an analysis method can shorten the time required to acquire a characteristic image. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an electron microscope according to a first embodiment. [Figure 2] FIG. 1 is a diagram showing an example of the configuration of a particle analysis device. [Figure 3] FIG. 4 is a diagram for explaining a first mode. [Figure 4] FIG. 10 is a diagram for explaining a second mode. [Figure 5] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 6] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 7] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 8] 10 is a flowchart showing an example of the flow of particle analysis processing by the particle analysis device. [Figure 9] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 10] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 11] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 12] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 13] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 14] FIG. 1 is a diagram for explaining a particle analysis method. [Figure 15] FIG. 2 is a diagram for explaining the order in which each region of a sample is analyzed. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the content of the present invention as defined in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0012] In the following, a scanning electron microscope that scans a sample with an electron beam to capture a sample image will be described as an example of the charged particle beam device according to the present invention. Note that the charged particle beam device according to the present invention may also be a device that scans a sample with a charged particle beam (such as an ion beam) other than an electron beam to capture a sample image.

[0013] 1. First embodiment 1.1. Configuration of an electron microscope First, an electron microscope according to a first embodiment will be described with reference to the drawings. 1 is a diagram showing an example of the configuration of an electron microscope 100 according to a first embodiment.

[0014] As shown in FIG. 1, the electron microscope 100 includes a measurement unit 10 and a particle analysis device 20.

[0015] The measurement unit 10 scans the sample S with an electron beam EB, detects electrons generated in the sample S, and captures a sample image. The sample image is an image obtained by scanning the sample S with a probe formed by the electron beam EB or the like, and detecting signals (electrons, X-rays, etc.) generated from the sample S. The sample image includes a secondary electron image and a backscattered electron image.

[0016] The measurement unit 10 includes an electron source 11, a converging lens 12, a scanning deflector 13, an objective lens 14, a sample stage 15, a backscattered electron detector 16, a secondary electron detector 17, an energy dispersive X-ray spectrometer 18, and a wavelength dispersive X-ray spectrometer 19.

[0017] The electron source 11 emits an electron beam EB. The electron source 11 is, for example, an electron gun that accelerates electrons emitted from a cathode by an anode and emits the electron beam EB.

[0018] The converging lens 12, together with the objective lens 14, converges the electron beam EB emitted from the electron source 11 to form an electron probe. The converging lens 12 can adjust the opening angle of the electron beam EB.

[0019] The scanning deflector 13 deflects the electron beam EB two-dimensionally. By the scanning deflector 13 deflecting the electron beam EB, the sample S can be scanned with the electron probe.

[0020] The objective lens 14 is a lens for forming an electron probe placed immediately in front of the sample S. The objective lens 14 includes, for example, a coil and a yoke. In the objective lens 14, the magnetic field lines generated by the coil are confined in a yoke made of a material with high magnetic permeability, and a notch is formed in part of the yoke, causing the densely distributed magnetic field lines to leak onto the optical axis.

[0021] A sample S is placed on the sample stage 15. The sample stage 15 supports the sample S. The sample stage 15 has a drive mechanism for moving the sample S. By moving the sample stage 15, the irradiation position of the electron beam EB on the sample S can be moved.

[0022] The backscattered electron detector 16 detects backscattered electrons generated in the sample S when the sample S is irradiated with the electron beam EB. The backscattered electrons are electrons that are emitted in the process of electrons that are incident on the sample S being scattered by elements that make up the sample S. The backscattered electron detector 16 is disposed, for example, directly below the objective lens 14. The backscattered electron detector 16 has an annular shape, and the electron beam EB is irradiated onto the sample S through a central hole in the backscattered electron detector 16. The backscattered electron detector 16 is, for example, a silicon semiconductor detector.

[0023] The secondary electron detector 17 detects secondary electrons emitted from the sample S when the sample S is irradiated with the electron beam EB. The secondary electrons are electrons excited in a solid by inelastic scattering of incident electrons and emitted into a vacuum. The secondary electron detector 17 is, for example, an ET detector (Everhart-Thornley detector).

[0024] The energy dispersive X-ray spectrometer (EDS) 18 is a detector for discriminating X-rays by energy and obtaining a spectrum. The energy dispersive X-ray spectrometer 18 detects characteristic X-rays generated in the sample S when the sample S is irradiated with an electron beam EB. This makes it possible to obtain an EDS spectrum.

[0025] The wavelength-dispersive X-ray spectrometer 19 (WDS) separates and detects X-rays of specific wavelengths by utilizing the Bragg reflection of X-rays by an analyzing crystal. The wavelength-dispersive X-ray spectrometer 19 obtains a spectrum for each wavelength of characteristic X-rays generated in the sample S when the sample S is irradiated with an electron beam EB by utilizing the Bragg reflection by the analyzing crystal.

[0026] The particle analysis device 20 performs particle analysis. That is, the particle analysis device 20 captures multiple sample images from multiple regions of the sample S, acquires particle images, which are images of particles contained in the sample S, from each of the multiple sample images, and acquires particle information based on the particle images. The particle information includes, for example, information on the shape of the particles, such as particle size, and information on the position of the particles. Furthermore, the particle analysis device 20 performs EDS analysis and WDS analysis on the particles based on the information on the position of the particles, and acquires information on the composition of the particles. The particle information includes information on the composition of the particles.

[0027] 2 is a diagram showing an example of the configuration of the particle analysis device 20. The particle analysis device 20 includes a processing unit 200, an operation unit 210, a display unit 220, and a storage unit 230, as shown in FIG.

[0028] The operation unit 210 is used by the user to input operation information, and outputs the input operation information to the processing unit 200. The functions of the operation unit 210 can be realized by input devices such as a keyboard, a mouse, buttons, a touch panel, and a touch pad.

[0029] The display unit 220 displays the image generated by the processing unit 200. The function of the display unit 220 can be realized by an LCD (Liquid Crystal Display), a touch panel display, or the like.

[0030] The storage unit 230 stores programs, data, etc. for the processing unit 200 to perform various calculation processes and various control processes. The storage unit 230 is also used as a working area for the processing unit 200, and is also used to temporarily store the results of calculations performed by the processing unit 200 in accordance with the various programs. The functions of the storage unit 230 can be realized by a RAM (Random Access Memory), a ROM (Read Only Memory), a hard disk, etc.

[0031] The functions of the processing unit 200 can be realized by executing programs stored in the storage unit 230 using various processors such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and a DSP (Digital Signal Processor). The processing unit 200 includes an image acquisition unit 202 and an analysis unit 204.

[0032] The image acquisition unit 202 acquires the sample image captured by the measurement unit 10, and acquires particle images from the acquired sample image. The image acquisition unit 202 repeats the process of acquiring the sample image and the process of acquiring particle images from the sample image to acquire multiple particle images.

[0033] The analysis unit 204 acquires information about the particles based on the multiple particle images acquired by the image acquisition unit 202 .

[0034] 1.2. How to obtain particle images 1.2.1. Particle image acquisition mode The electron microscope 100 has a first mode and a second mode as modes for acquiring particle images.

[0035] 1.2.2. First mode FIG. 3 is a diagram for explaining the first mode.

[0036] In the first mode, first, in the measurement unit 10, the sample S is scanned at a first scan speed to capture a sample image Is. The first scan speed is set to a scan speed at which the shape of the particles can be confirmed. The scan speed is the speed at which the electron probe is scanned, and the shorter the dwell time per pixel, the faster the scan speed. For example, in the first mode, a 1024 x 768 pixel sample image is captured at a scan speed where the dwell time per pixel is 4 μs / pixel. Note that the first scan speed can be changed as appropriate depending on the accuracy required for particle analysis.

[0037] The electron probe scans the sample S using a raster scan technique. That is, the electron probe draws a scanning line in the +X direction, moves the position where the scanning line is drawn in the -Y direction perpendicular to the +X direction, and then draws a scanning line in the +X direction with the electron probe, repeatedly scanning the sample S.

[0038] Next, the particle region is trimmed from the specimen image Is by image processing to obtain a particle image Ip. For example, the specimen image Is is first binarized, and the particle outlines are detected from the binarized specimen image Is. This makes it possible to extract the particle region from the specimen image Is. Next, a region that includes all of the extracted particle regions is cut out from the specimen image Is, thereby generating the particle image Ip. In this way, the particle image Ip can be obtained in the first mode.

[0039] 1.2.3. Second Mode FIG. 4 is a diagram for explaining the second mode.

[0040] In the second mode, first, in the measurement unit 10, the sample S is scanned at a second scan speed that is faster than the first scan speed to capture a sample image Is. The second scan speed is set to a speed at which particles can be confirmed. For example, in the second mode, a 1024 x 768 pixel sample image is captured at a scan speed where the dwell time per pixel is 1 μs / pixel. Note that the second scan speed can be changed as appropriate depending on the accuracy required for particle analysis.

[0041] Next, particle regions are detected in the sample image Is by image processing, and in the measurement unit 10, based on the particle region detection results, a region including all particle regions in the sample S is scanned at a third scan speed slower than the second scan speed to capture a particle image Ip. The third scan speed is, for example, the same as the first scan speed. For example, in the second mode, the particle image Ip is captured at a scan speed at which the dwell time per pixel is 4 μs / pixel. Note that the third scan speed is not particularly limited as long as it is slower than the second scan speed; for example, it may be slower or faster than the first scan speed. In this way, the particle image Ip can be acquired in the second mode.

[0042] 1.2.4. Particle image acquisition time In the first mode, if the number of pixels (resolution) of the sample image Is is R and the dwell time per pixel is D, the imaging time of the sample image Is is expressed as the product R × D of the number of pixels R and the dwell time D. Note that the time required to crop the sample image Is and acquire the particle image Ip is negligible because it is extremely short compared to the imaging time. Therefore, the acquisition time of the particle image Ip in the first mode is expressed as the product R × D.

[0043] In the second mode, the photographing time of the specimen image Is is expressed as R×D1, where R is the number of pixels and D1 is the dwell time per pixel when photographing the specimen image Is. Also, the photographing time of the particle image Ip is expressed as S×D2, where S is the number of pixels in the particle region in the specimen image Is and D2 is the dwell time per pixel. Therefore, the acquisition time for acquiring a particle image in the second mode is expressed as R×D1+S×D2.

[0044] Depending on the proportion of the particle area in the field of view in the sample image Is, the acquisition time of the particle image Ip in the second mode may be shorter than the acquisition time of the particle image Ip in the first mode, or the acquisition time of the particle image Ip in the first mode may be shorter than the acquisition time of the particle image Ip in the second mode.

[0045] The proportion of particles in the field of view can be expressed, for example, by the number of pixels S in the particle region in the sample image Is, assuming a constant resolution of the sample image Is. Therefore, when the number of pixels S in the particle region is less than a predetermined number, the acquisition time R×D1+S×D2 of the particle image Ip in the second mode becomes shorter than the acquisition time R×D of the particle image Ip in the first mode. Furthermore, when the number of pixels S in the particle region is greater than a predetermined number, the acquisition time R×D of the particle image Ip in the first mode becomes shorter than the acquisition time R×D1+S×D2 of the particle image Ip in the second mode. Therefore, by switching modes depending on the number of pixels S in the particle region, the acquisition time of the particle image Ip can be shortened.

[0046] If the acquisition time R×D of the particle image Ip in the first mode is shorter than the acquisition time R×D1+S×D2 of the particle image Ip in the second mode, then R×D<R×D1+S×D2となる。そのため、S> When (R×(D-D1)) / D2 is satisfied, the acquisition time R×D of the particle image Ip in the first mode becomes shorter than the acquisition time R×D1+S×D2 of the particle image Ip in the second mode. Therefore, when the number of pixels S in the particle region is greater than the threshold (R×(D-D1)) / D2, the particle image Ip is acquired in the first mode, and when the number of pixels S in the particle region is equal to or less than the threshold (R×(D-D1)) / D2, the particle image Ip is acquired in the second mode. This allows the acquisition time of the particle image Ip to be shortened.

[0047] Here, it is not possible to know the proportion of particles in the field of view of the area to be photographed, i.e., the area before photographing. Therefore, the proportion of particles in the field of view of the area to be photographed is estimated from the sample image Is that has already been acquired. Specifically, the number of pixels in the particle area in each sample image that has already been acquired is calculated to calculate the average number of pixels, and the average number of pixels is compared with a threshold to select the acquisition mode for the area to be photographed.

[0048] 1.3. Particle analysis method 5 to 7 are diagrams for explaining the particle analysis method, in which X-axis and Y-axis perpendicular to each other are shown.

[0049] In particle analysis, as shown in Figure 5, analysis is performed in the +X direction starting from region S-1 in the first column, followed by regions S-2, S-3, and S-4. After analysis is complete up to the last region S-4 in the first column, the analysis moves in the -Y direction and begins in the +X direction with the first region S-5 in the second column. Analysis is performed in the same order for regions from the third column onwards. In this way, analysis is performed from region S-1 to region Sn (n is an integer greater than or equal to 2).

[0050] First, analysis is performed on region S-1 of sample S. Since no sample image has been acquired in region S-1, particle image Ip-1 is acquired in the initially set first mode. Next, image processing is performed on particle image Ip-1 to acquire information on the particle's position (coordinates) and shape. Next, EDS analysis is performed on the particles to acquire particle composition information. Through the above steps, information on the particles in region S-1 can be acquired. Note that, although the initial setting is set to the first mode and particle image Ip-1 is acquired in the first mode, it is also possible to set the initial setting to the second mode and acquire particle image Ip-1 of region S-1 in the second mode.

[0051] Next, as shown in Figure 6, we analyze region S-2 of sample S. First, we select a mode to acquire particle image Ip-2 of region S-2. The mode is selected based on the proportion of the particle area in the field of view in the acquired sample image. Here, the average number of pixels in the particle area in the sample image is used as the proportion of the particle area in the field of view. The number of pixels in the particle area in the sample image is obtained by detecting the particle outline from particle image Ip-1 using image processing and counting the number of pixels within the outline.

[0052] As shown in Figure 6, the acquired specimen image is only for region S-1, so the number of pixels in the particle region in region S-1 is used as the average pixel number S. If the average pixel number S of the acquired specimen image is greater than the threshold (R × (D - D1)) / D2, specimen image Is-2 is acquired in the first mode. If the average pixel number S is equal to or less than the threshold, specimen image Is-2 is acquired in the second mode.

[0053] Next, as with region S-1, information on the particle position and particle shape is obtained from the acquired particle image Ip-2 by image processing, and EDS analysis is performed on the particles to obtain particle composition information. Through these steps, information on the particles in region S-2 can be obtained.

[0054] Next, as shown in Figure 7, region S-3 of sample S is analyzed. First, a mode for acquiring particle image Ip-3 of region S-3 is selected. To select the mode, the number of pixels in the particle region in the previously acquired sample image Is-1 and the number of pixels in the particle region in sample image Is-2 are calculated, and the average pixel count S is calculated. If the average pixel count S is greater than a threshold, particle image Ip-3 is acquired in the first mode. If the average pixel count S is equal to or less than the threshold, particle image Ip-3 is acquired in the second mode. In this manner, the mode can be selected. Next, as with regions S-1 and S-2, image processing is performed to acquire particle position and shape information from the acquired particle image Ip-3, and EDS analysis is performed to acquire particle composition information. Through these steps, particle information for region S-3 can be acquired.

[0055] For example, when analyzing region Sm (m is an integer greater than or equal to 2), the number of pixels in the particle region is calculated in each of the previously acquired sample images Is-1, Is-2, ..., and Is-(m-1), and the average pixel count S is calculated. Then, if the average pixel count S is greater than a threshold, particle image Ip-m is acquired in the first mode. If the average pixel count S is equal to or less than the threshold, particle image Ip-m is acquired in the second mode. Next, image processing is performed to obtain information on the particle position and particle shape from the acquired particle image Ip-m, and EDS analysis is performed to obtain particle composition information. Through these steps, information on the particles in region Sm can be obtained. In this way, analysis is performed from region S-1 to region Sn.

[0056] Processing FIG. 8 is a flowchart showing an example of the flow of particle analysis processing by the particle analysis device 20.

[0057] Here, the region to be analyzed of the sample S is set in advance by the user. The image acquisition unit 202 divides the region to be analyzed into n regions, each corresponding to a scanning range of the electron beam, and determines the region to be analyzed in one go. Here, the image acquisition unit 202 divides the region to be analyzed into n regions, and analyzes the regions in order from region S-1 (N=1) to region Sn (N=n).

[0058] When the user inputs an instruction to start particle analysis to the particle analysis device 20 via the operation unit 210, the image acquisition unit 202 acquires a particle image Ip-1 in a first mode in an area S-1 of the sample S, with N=1 (step S100). The image acquisition unit 202 scans the area S-1 of the sample S at a first scan speed to acquire a sample image Is-1. Next, the image acquisition unit 202 detects a particle area from the sample image Is-1, and acquires a particle image Ip-1 by trimming the particle area from the sample image Is-1.

[0059] Next, the analysis unit 204 performs image processing on the acquired particle image Ip-1 to acquire information on the position and shape of the particles (step S102).

[0060] Next, the analysis unit 204 acquires information about the particle composition from the results of the EDS analysis in the measurement unit 10 (step S104). The analysis unit 204 identifies particles in the sample S from the information about the particle positions, and causes the measurement unit 10 to irradiate the particles in the sample S with an electron beam EB. Characteristic X-rays emitted from the particles as a result of irradiation with the electron beam EB are detected by the energy dispersive X-ray spectrometer 18, and an EDS spectrum is obtained. In this way, the analysis unit 204 acquires the EDS spectrum. The analysis unit 204 performs qualitative and quantitative analysis on the EDS spectrum to acquire information about the particle composition.

[0061] Although the case where the analysis unit 204 performs EDS analysis has been described here, the analysis unit 204 may also perform WDS analysis to acquire information on the particle composition. Alternatively, the analysis unit 204 may also perform both EDS analysis and WDS analysis to acquire information on the particle composition.

[0062] Next, the image acquisition unit 202 determines whether or not the analysis of the last region Sn of the regions to be analyzed on the sample S has been completed, that is, whether or not N=n is satisfied (step S106).

[0063] If the image acquisition unit 202 determines that the analysis of the last region Sn has not been completed, that is, if it determines that N=n is not satisfied (No in step S106), it sets N=N+1, moves the sample S on the sample stage 15, and moves the scanning range from region S-1 to region S-2 (step S108).

[0064] Next, the image acquisition unit 202 calculates the number of pixels S in the particle region in the acquired sample image Is-1 (step S110). The image acquisition unit 202 detects the contour of the particle in the sample image Is-1 and counts the number of pixels within the detected contour. Here, since the acquired sample image Is-1 is only the sample image Is-1, the number of pixels in the particle region in the sample image Is-1 is used as the average pixel number S. Next, the image acquisition unit 202 determines whether the average pixel number S is greater than a threshold value (R × (D - D1)) / D2 (step S112).

[0065] If the image acquisition unit 202 determines that the average pixel number S is greater than the threshold value (Yes in step S112), it acquires a particle image Ip-2 in the first mode (step S114). The image acquisition unit 202 causes the measurement unit 10 to scan the sample S at a first scan speed to capture a sample image Is-2, and then crops the captured sample image Is-2 to acquire a particle image Ip-2.

[0066] Furthermore, if the image acquisition unit 202 determines that the average pixel number S is equal to or less than the threshold value (No in step S112), it acquires a particle image Ip-2 in the second mode (step S116). The image acquisition unit 202 causes the measurement unit 10 to scan the sample S at a second scan speed to capture a sample image Is-2. Next, the image acquisition unit 202 detects particle regions in the captured sample image Is-2 by image processing, and based on the detection result, causes the measurement unit 10 to scan the particle regions in the sample S at a third scan speed slower than the second scan speed to capture a particle image Ip-2. In this way, the image acquisition unit 202 acquires the particle image Ip-2.

[0067] After acquiring particle image Ip-2 in the first mode (after step S114) or after acquiring particle image Ip-2 in the second mode (after step S116), the process returns to step S102, and analysis unit 204 acquires particle position information and particle shape information by image processing of particle image Ip-2 (step S102). Next, analysis unit 204 acquires particle composition information from the results of EDS analysis in measurement unit 10 (step S104).

[0068] The image acquisition unit 202 determines whether the analysis of the last region Sn has been completed (step S 106), if it is determined that the analysis of the last region Sn has not been completed (No in step S106), N=N+1 is set, the sample S is moved on the sample stage 15, and the scanning range is moved from region S-2 to region S-3 (step S108).

[0069] The image acquisition unit 202 calculates the number of pixels in the particle region in the acquired specimen image Is-1 and the number of pixels in the particle region in the specimen image Is-2, calculates the average pixel number S (step S110), and determines whether the average pixel number S is greater than a threshold value (step S112). If the image acquisition unit 202 determines that the average pixel number S is greater than the threshold value (Yes in step S112), it acquires a particle image Ip-3 in the first mode (step S114). If the image acquisition unit 202 determines that the average pixel number S is equal to or less than the threshold value (No in step S112), it acquires a particle image Ip-3 in the second mode (step S116). The analysis unit 204 acquires particle position information and particle shape information from the particle image Ip-3 (step S102) and acquires particle composition information from the results of EDS analysis (step S104).

[0070] The image acquisition unit 202 and the analysis unit 204 repeat the processes of steps S108, S110, S112, S114, S116, S102, S104, and S106 until it is determined that the analysis of the last region Sn has been completed.

[0071] When the image acquisition unit 202 determines that the analysis of the last region Sn has ended (Yes in step S106), it ends the particle analysis process.

[0072] Effects The electron microscope 100 includes a measurement unit 10 that scans a sample S with an electron beam EB to capture a sample image, an image acquisition unit 202 that acquires multiple sample images Is captured in multiple regions of the sample S and acquires a particle image Ip, which is an image of a particle contained in the sample S, from each of the multiple sample images Is, and an analysis unit 204 that acquires information about the particles based on the particle image Ip. The image acquisition unit 202 also acquires multiple particle images Ip by repeating the following steps: selecting one mode from multiple modes for acquiring the particle image Ip based on the proportion of the particle area occupying the field of view in the acquired sample image Is; and acquiring the particle image Ip in the selected mode. The multiple modes also include a first mode in which the sample S is scanned at a first scan speed to capture a sample image Is, and the captured sample image Is is then cropped to obtain a particle image Ip, and a second mode in which the sample S is scanned at a second scan speed faster than the first scan speed to capture a sample image Is, and the particle region in the captured sample image Is is scanned at a third scan speed slower than the second scan speed to capture a particle image Ip.

[0073] Therefore, the electron microscope 100 can shorten the time required to acquire a particle image. Therefore, for example, the electron microscope 100 can perform particle analysis in a short time. Furthermore, for example, the electron microscope 100 can shorten the time required to acquire a particle image, thereby lengthening the measurement time required for EDS analysis, thereby improving the accuracy of the EDS analysis.

[0074] In the electron microscope 100, the image acquisition unit 202 calculates the average value of the pixel count of the particle region in the acquired specimen image in the process of selecting a mode, and selects one mode from multiple modes based on this average value. Therefore, the electron microscope 100 can accurately estimate the proportion of the particle region occupying the field of view. Therefore, the electron microscope 100 can accurately select an acquisition mode, and the time required to acquire a particle image can be shortened.

[0075] In the electron microscope 100, the image acquisition unit 202, in the process of selecting the mode, obtains the number of pixels in the particle region in each acquired specimen image, calculates the average number of pixels, and acquires the particle image in the first mode if the average number of pixels is greater than a threshold value. If R is the dwell time per pixel when capturing a sample image in the first mode, D is the dwell time per pixel when capturing a sample image in the second mode, D1 is the dwell time per pixel when capturing a particle image in the second mode, and D2 is the dwell time per pixel when capturing a particle image in the second mode, the threshold is (R×(D−D1)) / D2. Therefore, the electron microscope 100 can shorten the time required to capture a particle image.

[0076] In the electron microscope 100, the residence time of the electron beam EB per pixel when capturing a sample image in the second mode is shorter than the residence time of the electron beam EB per pixel when capturing a sample image in the first mode, so the second scan speed can be made faster than the first scan speed.

[0077] The analysis method in the electron microscope 100 includes the steps of acquiring multiple sample images taken in multiple regions of the sample S, acquiring particle images including images of particles contained in the sample S from each of the multiple sample images, and acquiring particle information based on the particle images. The step of acquiring particle images involves repeatedly selecting one mode from multiple modes for acquiring particle images based on the proportion of the particle area occupying the field of view in the acquired sample images, and acquiring the particle image in the selected mode, thereby acquiring multiple particle images. The multiple modes include a first mode in which the sample S is scanned at a first scan speed to acquire a sample image, and the acquired sample image is then cropped to acquire a particle image, and a second mode in which the sample S is scanned at a second scan speed faster than the first scan speed to acquire a sample image, and the particle area in the acquired sample image is scanned at a third scan speed slower than the second scan speed to acquire a particle image.

[0078] Therefore, the analysis method using the electron microscope 100 can shorten the time required to acquire a particle image.

[0079] 2. Second embodiment 2.1. Electron microscope Next, an electron microscope according to a second embodiment will be described. The configuration of the electron microscope according to the second embodiment is the same as the configuration of the electron microscope 100 shown in Figures 1 and 2 described above, and therefore a description thereof will be omitted.

[0080] 2.2. Particle analysis method 9 to 11 are diagrams for explaining the particle analysis method. Below, differences from the example of the particle analysis method in the first embodiment described above will be explained, and explanation of similarities will be omitted.

[0081] In the first embodiment shown in FIGS. 6 and 7 described above, the average number of pixels in the particle region in the acquired sample image is calculated, and the mode is selected based on whether the average number of pixels is greater than a threshold value.

[0082] In contrast, in the second embodiment, when capturing a sample image of a first region of the sample S, the average number of pixels in the particle region is calculated in the sample image of a second region that is already acquired and adjacent to the first region, and a mode is selected based on whether the average number of pixels is greater than a threshold value. The particle analysis method in the second embodiment will be described below with reference to FIGS. 9 to 11.

[0083] First, analysis of region S-1 of sample S is performed. Analysis of region S-1 is performed in the same manner as in the first embodiment described above. Next, analysis of region S-2 of sample S is performed. In region S-2, the only sample image that has been acquired and is an adjacent region is the sample image Is-1 of region S-1. Therefore, analysis of region S-2 of sample S is performed in the same manner as the process of analyzing region S-2 in the first embodiment described above.

[0084] Next, as shown in Figure 9, region S-3 of sample S is analyzed. In region S-3, the only adjacent sample image that has already been acquired is sample image Is-2. Therefore, the number of pixels in the particle region in sample image Is-2 is calculated. Then, if the calculated average pixel number S is greater than a threshold (R × (D - D1)) / D2, particle image Ip-3 is acquired in the first mode. If the average pixel number is equal to or less than the threshold, particle image Ip-3 is acquired in the second mode.

[0085] Next, region S-4 of sample S is analyzed. In region S-4, the only adjacent sample image that has already been acquired is sample image Is-3. Therefore, the number of pixels in the particle region in sample image Is-3 is calculated. Then, if the calculated average pixel number S is greater than a threshold (R × (D - D1)) / D2, particle image Ip-4 is acquired in the first mode. If the average pixel number is equal to or less than the threshold, particle image Ip-4 is acquired in the second mode.

[0086] Next, as shown in Figure 10, region S-5 of sample S is analyzed. In region S-5, the sample images that have already been acquired and are adjacent to region S-5 are sample image Is-1 and sample image Is-2. Therefore, the number of pixels in the particle region in sample image Is-1 and the number of pixels in the particle region in sample image Is-2 are calculated, and the average number of pixels S is calculated. Then, if the average number of pixels S is greater than a threshold (R × (D - D1)) / D2, particle image Ip-5 is acquired in the first mode, and if the average number of pixels S is equal to or less than the threshold, particle image Ip-5 is acquired in the second mode.

[0087] Next, as shown in Figure 11, region S-6 of sample S is analyzed. In region S-6, the four specimen images that have been acquired and are adjacent to region S-6 are specimen image Is-1, specimen image Is-2, specimen image Is-3, and specimen image Is-5. Therefore, in each of these four specimen images, the number of pixels in the particle region is calculated to determine the average number of pixels S. Then, if the calculated average number of pixels S is greater than a threshold (R × (D - D1)) / D2, particle image Ip-6 is acquired in the first mode. If the average number of pixels S is equal to or less than the threshold, particle image Ip-6 is acquired in the second mode. In this manner, analysis is performed from region S-1 to region Sn.

[0088] Processing The particle analysis process in the electron microscope 100 according to the second embodiment is similar to that in the electron microscope 100 according to the first embodiment, except for the process of calculating the average number of pixels S in the particle region shown in step S110 in Fig. 8. Below, differences from the example of the particle analysis method according to the first embodiment described above will be explained, and explanation of similarities will be omitted.

[0089] In step S110, when capturing a sample image of a first region of the sample S, the image acquisition unit 202 calculates the average number of pixels S of the particle region in the sample image of a second region adjacent to the first region, which is an already acquired sample image, and determines whether the average number of pixels S is greater than a threshold value. If the average number of pixels S is greater than the threshold value, the image acquisition unit 202 acquires the particle image in the first mode, and if the average number of pixels S is equal to or less than the threshold value, the image acquisition unit 202 acquires the particle image in the second mode.

[0090] Effects In the electron microscope 100, when capturing a sample image of a first region of the sample S, the image acquisition unit 202 calculates the average number of pixels in the particle region in the sample image of a second region that is adjacent to the first region, which is an already acquired sample image, and selects one mode from multiple modes based on this average value. Therefore, the electron microscope 100 can accurately estimate the proportion of the particle region that occupies the field of view. Therefore, the electron microscope 100 can accurately select an acquisition mode, and the time required to acquire a particle image can be shortened.

[0091] 3. Third embodiment 3.1. Electron microscope Next, an electron microscope according to a third embodiment will be described. The configuration of the electron microscope according to the third embodiment is the same as the configuration of the electron microscope 100 shown in Figures 1 and 2 described above, and therefore a description thereof will be omitted.

[0092] 3.2. Particle analysis method 12 to 14 are diagrams for explaining the particle analysis method. Below, differences from the example of the particle analysis method in the first embodiment described above will be explained, and explanation of similarities will be omitted.

[0093] In the first embodiment shown in FIGS. 6 and 7 described above, the average number of pixels S in the particle region in the acquired specimen image is calculated, and the mode is selected based on whether the average number of pixels S is greater than a threshold value.

[0094] In contrast, in the third embodiment, when a specimen image of a second region is captured after a specimen image of a first region, if the specimen images of the first region and the second region are adjacent to each other, the number of pixels in the particle region in the specimen image of the first region is calculated, and a mode is selected based on whether or not the number of pixels is greater than a threshold value. That is, the number of pixels in the particle region in the specimen image captured immediately before is calculated, and the number of pixels is compared with a threshold value to select a mode.

[0095] On the other hand, if the specimen image in the first region and the specimen image in the second region are not adjacent, the number of pixels in the particle region in the specimen image in the third region adjacent to the second region is calculated, and the mode is selected based on whether the number of pixels is greater than a threshold value.

[0096] First, region S-1 of sample S is analyzed. The analysis of region S-1 is performed in the same manner as in the first embodiment described above. Next, region S-2 of sample S is analyzed. In region S-2, the region photographed immediately before is region S-1. Therefore, the number of pixels in the particle region in sample image Is-1 is calculated. Then, if the calculated number of pixels S is greater than a threshold value (R × (D - D1)) / D2, particle image Ip-2 is acquired in the first mode, and if the number of pixels S is equal to or less than the threshold value, particle image Ip-2 is acquired in the second mode.

[0097] Next, region S-3 is analyzed as shown in Figure 12. In region S-3, the region photographed immediately before is region S-2. Therefore, the number of pixels in the particle region is calculated in specimen image Is-2. Then, if the calculated number of pixels S is greater than the threshold (R × (D - D1)) / D2, particle image Ip-3 is acquired in the first mode. If the number of pixels S is equal to or less than the threshold, particle image Ip-3 is acquired in the second mode.

[0098] Next, region S-4 is analyzed as shown in Figure 13. In region S-4, the region photographed immediately before is region S-3. Therefore, the number of pixels in the particle region is calculated in specimen image Is-3. Then, if the calculated number of pixels S is greater than the threshold (R × (D - D1)) / D2, particle image Ip-4 is acquired in the first mode. If the number of pixels is equal to or less than the threshold, particle image Ip-4 is acquired in the second mode.

[0099] Next, as shown in FIG. 14, region S-5 is analyzed. The region photographed immediately before in region S-5 is region S-4. However, region S-4 is located at the end of the region to be analyzed in the +X direction, and region S-5 is located at the end in the -X direction. In other words, region S-4 and region S-5 are not adjacent to each other. In this case, the number of pixels S of the particle region in the specimen image Is-1 of region S-1 adjacent to region S-5 is calculated. Then, if the calculated number of pixels S is greater than the threshold (R×(D−D1)) / D2, particle image Ip-5 is acquired in the first mode. When the number of pixels S is equal to or smaller than the threshold, a particle image Ip-5 is acquired in the second mode.

[0100] Here, region S-1, which has the longest side length tangent to region S-5, is selected as the region adjacent to region S-5. Note that, as the region adjacent to region S-5, the number of pixels in the particle region may be calculated in the acquired specimen images of all regions adjacent to region S-5, and the average number of pixels may be calculated. For example, since region S-1 and region S-2 are adjacent to region S-5, the number of pixels in the particle region in specimen image Is-1 and the number of pixels in the particle region in specimen image Is-2 may be calculated, and the average number of pixels may be calculated.

[0101] Processing The particle analysis process in the electron microscope 100 according to the third embodiment is similar to that in the electron microscope 100 according to the first embodiment, except for the process of calculating the average number of pixels S in the particle region shown in step S110 in Fig. 8. Below, differences from the example of the particle analysis method according to the first embodiment described above will be explained, and explanation of similarities will be omitted.

[0102] In step S110, when capturing a specimen image of a second region after capturing a specimen image of a first region, if the specimen image of the first region and the specimen image of the second region are adjacent, the image capture unit 202 calculates the number of pixels in the particle region in the specimen image of the first region and selects a mode depending on whether the number of pixels is greater than a threshold value. Also, if the specimen image of the first region and the specimen image of the second region are not adjacent, the image capture unit 202 calculates the number of pixels in the particle region in the specimen image of a third region adjacent to the second region and selects a mode depending on whether the number of pixels is greater than a threshold value.

[0103] Effects In the electron microscope 100, in the process of selecting a mode, when a specimen image of a second region is captured after a specimen image of a first region, if the specimen images of the first region and the second region are adjacent, the image acquisition unit 202 calculates the number of pixels in the particle region in the specimen image of the first region and selects the mode based on whether or not the number of pixels is greater than a threshold value. Also, if the specimen images of the first region and the second region are not adjacent, the image acquisition unit 202 calculates the number of pixels in the particle region in the specimen image of a third region adjacent to the second region and selects the mode based on whether or not the number of pixels is greater than a threshold value. Therefore, the electron microscope 100 can accurately estimate the proportion of the particle region in the field of view. Therefore, the electron microscope 100 can accurately select a mode and shorten the time required to acquire particle images.

[0104] 3.5. Variations In the third embodiment described above, when a sample image of a second region is captured after a sample image of a first region, if the sample image of the first region and the sample image of the second region are not adjacent, the image acquisition unit 202 calculates the number of pixels in the particle region in the sample image of the third region adjacent to the second region. However, even if the sample image of the first region and the sample image of the second region are not adjacent, the image acquisition unit 202 may calculate the number of pixels in the particle region in the sample image of the first region. That is, in the process of selecting a mode, when a sample image of the second region is captured after a sample image of the first region, the image acquisition unit 202 may always calculate the number of pixels in the particle region in the sample image of the first region, and select a mode depending on whether the number of pixels is greater than a threshold.

[0105] 4. Variations 4.1. First Variant In the first to third embodiments described above, the dwell time of the electron beam per pixel when photographing a specimen image in the second mode is shorter than the dwell time of the electron beam per pixel when photographing a specimen image in the first mode. Therefore, the second scan speed when photographing a specimen image in the second mode is shorter than the first scan speed when photographing a specimen image in the first mode. Faster than a standard.

[0106] Alternatively, the resolution of the sample image in the second mode may be lower than the resolution of the sample image in the first mode, while maintaining the electron beam dwell time per pixel constant. This allows the second scan speed when capturing the sample image in the second mode to be faster than the first scan speed when capturing the sample image in the first mode. The resolution of the sample image corresponds to the number of pixels in the sample image. The scan speed is inversely proportional to the resolution (number of pixels) of the sample image. Therefore, by lowering the resolution of the sample image, i.e., by reducing the number of pixels in the sample image, the scan speed can be increased. The resolution of the sample image in the second mode is set, for example, to a resolution at which particles can be identified. The resolution of the sample image in the second mode can be changed as appropriate depending on the accuracy required for particle analysis.

[0107] The resolution of the particle image in the second mode is set to be higher than the resolution of the sample image in the second mode. The resolution of the particle image in the second mode may be the same as or higher than the resolution of the sample image in the first mode.

[0108] 4.2. Second Variant In the above-described first to third embodiments, a particle image, which is an image of particles contained in the sample S, is acquired from the sample image to acquire information about the particles. That is, although the particles contained in the sample S are the subject of analysis, the subject of analysis is not limited to particles.

[0109] For example, in the electron microscope 100, a feature image, which is an image of a feature contained in the sample S, may be acquired from the sample image to acquire information about the feature. The feature may be, for example, a defect such as a crystal defect, or an inclusion in steel. In sample images such as secondary electron images and backscattered electron images, these defects and inclusions are photographed with a contrast different from that of the base material of the sample S, just like particles. Therefore, feature features such as defects and inclusions can be extracted from the sample image by image processing, just like the particles described above. Therefore, feature features such as defects and inclusions can be analyzed using techniques similar to the particle analysis described above.

[0110] 4.3. Third Variant FIG. 15 is a diagram for explaining the order in which each region of the sample S is analyzed.

[0111] In the first to third embodiments described above, after each region in the first row is analyzed in the +X direction, the movement is made in the -Y direction, and each region in the second row is analyzed in the +X direction, as shown in Fig. 5. The second and subsequent rows are analyzed in the same order, and the entire region to be analyzed on the sample S is analyzed.

[0112] 15, after each region in the first row is analyzed in the +X direction, the system moves in the -Y direction and each region in the second row is analyzed in the -X direction. After each region in the second row is analyzed, the system moves in the -Y direction and each region in the third row is analyzed in the +X direction. The fourth row and subsequent rows are analyzed in the same order until the entire region to be analyzed on the sample S is analyzed.

[0113] The order in which the regions of the sample S are analyzed is not limited to the examples shown in FIGS. 5 and 15, and the analysis may be performed in any order.

[0114] 4.4. Fourth Variant In the first embodiment described above, the average value of the pixel counts in particle regions (average pixel count S) in multiple acquired specimen images is compared with a threshold value, but the representative value representing the pixel counts in particle regions is not limited to the average value. For example, the median or mode of the pixel counts in particle regions may be used as the representative value and compared with the threshold value.

[0115] 4.5. Fifth Variant In the above-described first to third embodiments, the charged particle beam device according to the present invention is described as a scanning electron microscope, but the charged particle beam device according to the present invention is not limited to a scanning electron microscope. The charged particle beam device according to the present invention may be, for example, a scanning transmission electron microscope (STEM), an electron beam microanalyzer (EPMA), a focused ion beam device (FIB), or the like. In other words, the charged particle beam device according to the present invention is not particularly limited as long as it is a device that can capture an image of a sample by scanning the sample with a charged particle beam such as an electron beam or an ion beam.

[0116] The above-described embodiment and modifications are merely examples, and the present invention is not limited to these. For example, the embodiments and modifications can be combined as appropriate.

[0117] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes configurations that are substantially identical to the configurations described in the embodiments. A substantially identical configuration means, for example, a configuration with the same function, method, and result, or a configuration with the same purpose and effect. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects or purposes as the configurations described in the embodiments. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments. [Explanation of symbols]

[0118] 10... measurement unit, 11... electron source, 12... converging lens, 13... scanning deflector, 14... objective lens, 15... sample stage, 16... backscattered electron detector, 17... secondary electron detector, 18... energy dispersive X-ray spectrometer, 19... wavelength dispersive X-ray spectrometer, 20... particle analysis device, 100... electron microscope, 200... processing unit, 202... image acquisition unit, 204... analysis unit, 210... operation unit, 220... display unit, 230... memory unit

Claims

1. a measurement unit that scans the sample with a charged particle beam to capture an image of the sample; an image acquisition unit that acquires a plurality of sample images taken in a plurality of regions of the sample and acquires a feature image that is an image of a feature contained in the sample from each of the plurality of sample images; an analysis unit that acquires information about the feature object based on the feature image; Including, The image acquisition unit selecting one mode from a plurality of modes for acquiring the feature image based on the proportion of the area of ​​the feature in the field of view in the acquired sample image; acquiring the feature image in a selected mode; to obtain a plurality of the characteristic images; The plurality of modes include: a first mode in which the sample is scanned at a first scan speed to capture a sample image, and the captured sample image is trimmed to acquire the characteristic image; a second mode in which the sample is scanned at a second scan speed faster than the first scan speed to capture a sample image, and a region of the feature in the captured sample image is scanned at a third scan speed slower than the second scan speed to capture the feature image; A charged particle beam device comprising:

2. In claim 1, In the process of selecting a mode, the image acquisition unit calculating a representative value of said ratio in the acquired sample images; a charged particle beam device that selects one mode from the plurality of modes based on the representative value;

3. In claim 2, In the process of selecting a mode, the image acquisition unit determining the number of pixels in the region of the feature in each of the acquired sample images, and calculating the average number of pixels; When the average number of pixels is greater than a threshold, the feature image is acquired in the first mode; a charged particle beam device, wherein the threshold value is (R×(D−D1)) / D2, where R is the number of pixels of a sample image, D is a dwell time per pixel when capturing a sample image in the first mode, D1 is a dwell time per pixel when capturing a sample image in the second mode, and D2 is a dwell time per pixel when capturing a particle image in the second mode.

4. In claim 1, In the process of selecting a mode, the image acquisition unit When capturing a sample image of a first region of the sample, a representative value of the ratio is calculated in a sample image of a second region that is already captured and is adjacent to the first region; a charged particle beam device that selects one mode from the plurality of modes based on the representative value;

5. In claim 1, In the process of selecting a mode, the image acquisition unit When a sample image of a second area is photographed after a sample image of a first area, the ratio is calculated in the sample image of the first area; a charged particle beam device that selects one mode from the plurality of modes based on the ratio in the sample image of the first region;

6. In claim 1, In the process of selecting a mode, when a sample image of a second area is captured after a sample image of a first area, the image acquisition unit When the first area and the second area are adjacent to each other, the ratio is calculated in the specimen image of the first area, and one mode is selected from the plurality of modes based on the ratio in the specimen image of the first area; When the first region and the second region are not adjacent to each other, the ratio is calculated in a sample image of a third region adjacent to the second region, and one mode is selected from the plurality of modes based on the ratio in the sample image of the first region.

7. In any one of claims 1 to 6, a residence time of the charged particle beam per pixel when capturing a sample image in the second mode is shorter than a residence time of the charged particle beam per pixel when capturing a sample image in the first mode.

8. In any one of claims 1 to 6, A charged particle beam device, wherein the resolution of the sample image in the second mode is lower than the resolution of the sample image in the first mode.

9. An analysis method for a charged particle beam device that scans a sample with a charged particle beam to capture a sample image, comprising: acquiring a plurality of sample images photographed in a plurality of regions of the sample, and acquiring a feature image, which is an image of a feature contained in the sample, from each of the plurality of sample images; acquiring information about the feature based on the feature image; Including, The step of acquiring the characteristic image includes: selecting one mode from a plurality of modes for acquiring the feature image based on a proportion of the area of ​​the feature in a field of view in an acquired sample image; acquiring said characteristic image in a selected mode; to obtain a plurality of the characteristic images; The plurality of modes include: a first mode in which the sample is scanned at a first scan speed to capture a sample image, and the captured sample image is trimmed to acquire the characteristic image; a second mode in which the sample is scanned at a second scan speed faster than the first scan speed to capture a sample image, and a region of the feature in the captured sample image is scanned at a third scan speed slower than the second scan speed to capture the feature image; An analysis method including:

Images