Charged Particle Beam Device and Control Method of Charged Particle Beam Device

Abstract

In the present invention, a charged particle beam device includes: a movement mechanism that holds and moves a sample; a particle source that outputs a charged particle beam; a detector that detects a signal that is generated by irradiating the sample with the charged particle beam; and a controller that controls the movement mechanism, the particle source, and the detector. The controller determines an irradiation target area in the sample in accordance with the sample, moves the irradiation position of the charged particle beam in the irradiation target area, acquires a diffraction pattern obtained using the detection result from the detector at a different irradiation position, and controls the movement mechanism on the basis of an analysis result of the diffraction pattern so as to adjust the inclination of the sample.

Description

Technical Field

[0001] The present invention relates to a charged particle beam apparatus and a control method thereof.

Background Art

[0002] In the observation of a sample using a charged particle beam apparatus such as STEM (Scanning Transmission Electron Microscope) / TEM (Transmission Electron Microscope), an image corresponding to the sample structure projected in the direction of electron beam irradiation can be obtained. Focusing on the interface portion where two different substances are in contact, when the interface is parallel to the electron beam irradiation direction, the position of the boundary between the substances can be clearly confirmed in the observation image. On the other hand, when the interface is inclined with respect to the electron beam irradiation direction, the interface portion is projected obliquely and thus spreads in the inclination direction in the observation image, making it difficult to clearly confirm the position. For these reasons, the resolution of the image obtained depends on the relationship between the direction of electron beam irradiation and the orientation of the sample.

[0003] By aligning the interfaces in the sample structure with the traveling direction of the irradiated electron beam, a high-resolution image with reduced image blur can be obtained. As a method for obtaining such conditions, in many cases, such as in a semiconductor device sample fabricated on a crystal substrate, the direction of the interface in the sample structure and the direction of the crystal in the substrate part (crystal orientation) are made to coincide. The tilt direction of the entire sample is adjusted so that the direction of the crystal in the substrate part coincides with the direction of the irradiated electron beam. In some cases, the crystal orientation of the substrate part of the sample can be determined from the appearance of the sample, but in the case of a sample fabricated using a focused ion beam device or the like, the external appearance and the internal crystal direction are different and cannot be determined from the appearance. When the crystal orientation of the sample cannot be determined from the appearance, it is necessary to calculate the amount and direction of deviation of the crystal orientation of the sample using the diffraction pattern obtained by irradiating the electron beam. At this time, if an area other than the crystal region of the substrate part is included in the region irradiated with the electron beam, the obtained diffraction pattern will be a mixture of multiple pieces of information, making it difficult to calculate the amount and direction of deviation of the crystal orientation. Therefore, the electron beam is sized to fit within the crystal region and is stopped at one location within the crystal region for irradiation, and the diffraction pattern is acquired.

[0004] For example, Patent Document 1 discloses a technique for detecting a diffraction pattern in a transmission type charged particle microscope. During the recording of each frame, a scanning assembly for causing relative movement between the diffraction pattern and the detector is used so that each local intensity maximum value in the pattern traces a locus on the detector.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the STEM / TEM observation of a device thin-film sample, it is necessary to align the electron beam incident direction and the sample orientation during observation to perform high-precision length measurement. If the orientation is misaligned, the interface will be blurred and the length measurement accuracy will decrease. The adjustment of the sample orientation is performed by irradiating the electron beam into a single-crystalline region serving as a reference within the sample, and changing the sample tilt while measuring the deviation of the sample orientation based on the diffraction pattern formed by the electron beam transmitted through the sample.

[0007] During the adjustment operation, since the electron beam continues to irradiate a local region on the sample, crystalinity degradation and sample contamination due to damage are likely to occur, and failure of orientation adjustment and accuracy degradation may occur. Specifically, blurring of the diffraction pattern and disappearance of spots may occur, and it may become impossible to obtain a clear diffraction pattern. This is particularly problematic in the observation of thin samples such as semiconductor device samples manufactured by a fine process or in the use of a large current beam with a large convergence.

Means for Solving the Problem

[0008] A typical example of the invention disclosed in the present application is as follows. That is, a charged particle beam device includes a moving mechanism that holds and moves a sample, a particle source that outputs a charged particle beam, a detector that detects a signal generated by irradiating the charged particle beam onto the sample, and a controller that controls the moving mechanism, the particle source, and the detector. The controller determines an irradiation target region in the sample according to the sample, moves the irradiation position of the charged particle beam in the irradiation target region, acquires a diffraction pattern based on the detection results of the detector at different irradiation positions, and controls the moving mechanism based on the analysis result of the diffraction pattern to adjust the tilt of the sample.

Effect of the Invention

[0009] According to one aspect of the present invention, damage to the sample can be reduced in obtaining a diffraction pattern for adjusting the orientation of an observation sample. Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 3B

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Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not construed as being limited to the description content of the embodiments shown below. It will be readily understood by those skilled in the art that the specific configuration can be changed without departing from the spirit or gist of the present invention.

[0012] In the configuration of the invention described below, the same or similar configurations or functions are denoted by the same reference numerals, and redundant descriptions are omitted.

[0013] In this specification and the like, notations such as "first", "second", "third", etc. are attached to identify components, and do not necessarily limit numbers or order.

[0014] In the drawings and the like, the position, size, shape, and range, etc. of each component shown may not represent the actual position, size, shape, and range, etc. in order to facilitate the understanding of the invention. Therefore, in the present invention, it is not limited to the position, size, shape, and range, etc. disclosed in the drawings and the like.

[0015] When acquiring a diffraction pattern for azimuth adjustment of an observation target sample, the charged particle beam device according to an embodiment of this specification does not fix the irradiation position, but scans the charged particle beam (primary beam or simply referred to as beam) in a minute region to expand the irradiation region. By the dispersion of the irradiation position, damage and contamination due to temperature rise and the like are reduced. Also, by capturing the information due to the region dispersion on average, more accurate azimuth adjustment becomes possible. The diffraction pattern includes a spot pattern and a Ronchigram.

[0016] The charged particle beam device determines the scanning region of the charged particle beam according to the target sample. The scanning region is, for example, a single crystal region. For example, when the sample is a semiconductor chip, a region in the silicon substrate can be selected as the scanning region. The charged particle beam device can obtain a fixed (identical) diffraction pattern even when scanning the beam in the single crystal region. Also, a sample with deflection can be adjusted to an average azimuth.

[0017] FIG. 1 is a diagram showing an example of the configuration of a scanning transmission electron microscope (STEM: Scanning Transmission Electron Microscopy) according to an embodiment of this specification.

[0018] STEM100 includes an electron optical column 101 and a control unit 102. The electron optical column 101 has an electron source 111, first and second condenser lenses 112, a condenser aperture 113, a deflector for axial misalignment correction 114, a stigmator 115, a deflector for image shift 116, an objective lens 117, a sample stage 118, an intermediate lens 119, a projection lens 120, and an electron detector group 121, a secondary electron detector 124. When not distinguishing the aforementioned devices included in the electron optical column 101, they are also described as target devices.

[0019] The sample stage 118 holds the sample 122. The sample 122 may be held by a sample holder fixed to the sample stage 118. The sample stage 118 or the sample holder or a combination thereof is an example of a moving mechanism that realizes the holding and movement of the sample 122. The sample stage 118 can be tilted about one or more tilt axes (rotation axes).

[0020] The electron beam emitted from the electron source 111, which is a particle source, is reduced by the first and second condenser lenses 112 and the radiation angle is limited by the condenser aperture 113. Further, after the axial adjustment of the electron beam is performed by the deflector for axial misalignment correction 114, the stigmator 115, and the deflector for image shift 116, the electron beam is irradiated onto the sample 122 from a direction substantially perpendicular to the sample 122 by the magnetic field on the front side of the sample of the objective lens 117.

[0021] The first and second condenser lenses 112, the condenser aperture 113, the deflector for axial misalignment correction 114, the stigmator 115, the deflector for image shift 116, the objective lens 117, the sample stage 118, the intermediate lens 119, and the projection lens 120 are examples of optical elements that adjust the direction and focus of the electron beam with respect to the sample 122.

[0022] The control unit 102 is a controller that generates a secondary electron image representing the surface structure of the sample 122 from the secondary electrons detected by the secondary electron detector 124 and displays it for the user. Usually, in the STEM 100, the diffraction pattern is formed near the rear focal plane located between the objective lens 117 and the intermediate lens 119 due to the influence of the magnetic field behind the objective lens 117. Also, the diffraction pattern is detected by the electron detector group 121 (hereinafter, also simply referred to as the detector 121). The detector 121 can include an annular dark field detector, a bright field detector, a CCD camera, etc. The detector 121 detects signals emitted from the sample 122 irradiated with an electron beam.

[0023] The computer, which is the control unit 102, controls the electron optical system column 101 using a plurality of control circuits. The control unit 102 includes an electron gun control circuit 151, an irradiation lens control circuit 152, a condenser aperture control circuit 153, an alignment correction deflector control circuit 154, a stigmator control circuit 155, an image shift deflector control circuit 156, an objective lens control circuit 157, a sample stage control circuit 158, an intermediate lens control circuit 159, a projection lens control circuit 160, a transmission scattering detector control circuit 161, and a secondary electron detector control circuit 163.

[0024] The control unit 102 creates arbitrary electron optical conditions by acquiring the values of each target device via each control circuit and inputting values to each target device via each control circuit. The control unit 102 is an example of a control mechanism that realizes the control of the electron optical system column 101.

[0025] The control unit 102 has a processor 171, a main storage device 172, an auxiliary storage device 173, an input device 174, an output device 175, and a network interface 176. Each device is connected to each other via a bus.

[0026] The processor 171 executes a program stored in the main storage device 172. By executing processing according to the program, the processor 171 functions as various functional units.

[0027] The main memory device 172 is a memory device such as a semiconductor memory, and stores programs and data executed by the processor 171. Further, the main memory device 172 is also used as a work area temporarily used by the program. For example, an operating system, a program for controlling the target device of STEM100, a program for acquiring an image of the sample 122, and a program for processing the acquired image are stored in the main memory device 172.

[0028] In this specification, when explaining the processing mainly based on STEM100 (control unit 102), it means that the processor 171 that executes any program is executing the processing.

[0029] The auxiliary storage device 173 is a storage device such as an HDD (Hard Disk Drive) and an SSD (Solid State Drive), and permanently stores data. The programs and data stored in the main memory device 172 may be stored in the auxiliary storage device 173. In this case, the processor 171 reads the programs and data from the auxiliary storage device 173 and loads them into the main memory device 172 when the control unit 102 is started or when processing is required.

[0030] The input device 174 is a device for a user to input instructions and information to the control unit 102, such as a keyboard, a mouse, and a touch panel. The output device 175 is a device for outputting an image, an analysis result, etc. to the user, such as a display and a printer. The network interface 176 is an interface for performing communication via a network.

[0031] In FIG. 1, the control unit 102 is described as one computer, but the control unit 102 may be configured using a plurality of computers. Note that at least a part of the functions of the control unit 102 may be realized using a logic circuit such as an ASIC or an FPGA configured for specific processing. Further, the primary charged particles irradiated to the sample 122 may be different from electrons.

[0032] STEM1 irradiates the electron beam converged on the sample 122 and scans the converged electron beam using a deflection coil such as the deflection device 116 for image shift. The detector 121 is used to record signals at each scanning position on the sample, and the control unit 102 displays the image. The detector 121 can include multiple types of detectors such as an annular dark field detector, an annular bright field detector, a bright field detector, and a CCD camera. By detecting transmitted or scattered electrons with the detector selected by lens adjustment under the sample, a desired type of image can be obtained.

[0033] Figure 2 shows a flowchart of the outline of the process executed by STEM1. STEM1 automatically adjusts the sample stage 118 so that the deviation between the orientation of the sample 122 and the incident direction of the electron beam onto the sample 122 is minimized.

[0034] In the STEM observation of the sample 122, by aligning the electron beam incident direction and the sample orientation during observation, high-precision length measurement becomes possible. When the sample orientation deviates from the electron beam incident direction, the interface blurs and the length measurement accuracy decreases. The adjustment of the sample orientation utilizes the diffraction pattern formed by the electron beam transmitted through the sample 122. STEM1 changes the sample tilt while measuring the deviation amount of the sample orientation based on the diffraction pattern.

[0035] For obtaining the diffraction pattern, STEM1 scans a specific region of the sample 122 with the electron beam. When obtaining the diffraction pattern for orientation adjustment, by scanning the electron beam in the target region, the irradiation region can be expanded, and damage and contamination of the sample 122 can be reduced.

[0036] One embodiment of this specification selects a single crystal region (hereinafter also simply referred to as a crystal region) within the sample 122 as the target region for obtaining the diffraction pattern. For example, in a semiconductor device, a silicon substrate is generally composed of single crystal silicon and has a sufficient size for damage reduction. In the example described below, STEM1 scans the region within the silicon substrate of the sample 122 with the electron beam to obtain a diffraction pattern.

[0037] Referring to FIG. 2, the control unit 102 determines an irradiation target area for obtaining a diffraction pattern in the sample 122 (S11). Details of the method for specifying the irradiation target area will be described later. Next, the control unit 102 scans the irradiation target area determined in step S11 with an electron beam to obtain a diffraction pattern (S12).

[0038] Next, the control unit 102 determines the amount of deviation of the sample 122 from the electron beam incident direction in terms of orientation based on the diffraction pattern (S13). Further, the control unit 102 controls the sample stage 118 based on the orientation deviation amount determined in step S103 to adjust the inclination of the sample 122 (S14). Thereby, the crystal orientation of the sample can be aligned with the incident angle of the electron beam to minimize the deviation. If possible, instead of controlling the inclination of the sample, the incident angle of the electron beam may be adjusted.

[0039] Hereinafter, a method (S11) for determining an irradiation target area for obtaining a diffraction pattern for orientation adjustment in the sample 122 will be described. Here, it is assumed that the control unit 102 selects a single crystal region as the irradiation target area. Note that any area within the sample 122 from which a diffraction pattern can be obtained may be selected as the irradiation target area.

[0040] The area and method for specifying the irradiation target area are specified for each sample 122, and the STEM 1 determines the irradiation target area according to the sample 122. In one embodiment, the control unit 102 may refer to sample information including information on the sample structure and determine the area of the size and shape indicated by the sample information as the irradiation target area. In one embodiment, the control unit 102 may refer to a signal obtained by irradiating the sample 122 with an electron beam and determine the area in the specified substance state as the irradiation target area. An example of the specified substance state is a single crystal structure.

[0041] FIG. 3A is an observation image schematically showing an overall appearance example including a semiconductor sample and a support structure of the semiconductor sample. FIG. 3A is a secondary electron image. In FIG. 3A, the semiconductor sample 200 is composed of a rectangular thinned region 202 and support portions 207 (only one of them is indicated by a reference numeral) on both sides thereof. The support portion 207 is coupled to the base portion 208 on the lower side of FIG. 3A. In FIG. 3A, the thinned region 202 is a region of the semiconductor sample 200 thinned by irradiating, for example, a convergent ion beam from the upper direction of the figure. The support portion 207 is a non-thinned, thick region. The base portion 208 is also a thick region.

[0042] Since the electron beam passes through the thinned region 202 of the semiconductor sample 200, the thinned region 202 is an observable region. The observable region is a region in the sample through which the electron beam can pass (including direct electrons and scattered electrons). On the other hand, the thick support portion 207 and the base portion 208 are regions through which the electron beam cannot pass and are unobservable regions. Other regions in FIG. 3A are spaces (vacuum regions) where no substance exists. The electron beam passes through the vacuum region without being scattered. The vacuum region is an unobservable region and is a non-single crystal region (also simply referred to as a non-crystalline region) described later in this specification. Hereinafter, the thinned region of the semiconductor sample is also referred to as a semiconductor thinned sample.

[0043] The control unit 102 acquires a secondary electron observation image or a STEM observation image of the sample 200, and moves the sample stage 118 so that the initial position (initial irradiation position) 211 is located near the center within the field of view, for example, by pattern matching. FIG. 3B shows a partially enlarged view of the observation image of the semiconductor thinned sample 202. The semiconductor thinned sample (observable region) 202 includes a substrate region 201 made of single crystal silicon and an element region (structural region) 203 on the substrate region 201. The element region 203 is a non-single crystal region. In this example, the initial position 211 is located substantially at the center within the substrate region 201.

[0044] The control unit 102 determines the irradiation target area 213 within the substrate area 201. The control unit 102 acquires a diffraction pattern while scanning the sample. The control unit 102 searches for an area where the diffraction pattern does not change from the initial position 211 and determines it as the irradiation target area 213.

[0045] Figure 4 shows an example of a diffraction pattern obtained by irradiating a single crystal area with an electron beam. The sample includes a single crystal area 261 and a non-single crystal area 262. The electron beam 251 is irradiating the single crystal area 261. Regardless of the irradiation position within the single crystal area 261, the same diffraction pattern can be acquired. The acquired diffraction pattern 310 is composed of a plurality of regularly two-dimensionally arranged spots. By performing area recognition (blob analysis, etc.) on the diffraction pattern 310, a diffraction pattern 320 in which each spot can be clearly discriminated is obtained. The blob analysis binarizes the diffraction pattern 310 to determine the outer shape of each spot.

[0046] Figure 5 shows an example of a diffraction pattern obtained by irradiating a non-single crystal area with an electron beam. The electron beam 251 is irradiating the non-single crystal area 262. The acquired diffraction pattern 315 is composed of one spot. By performing area recognition (blob analysis) on the diffraction pattern 315, a diffraction pattern 325 in which the spot can be clearly discriminated is obtained. The blob analysis binarizes the diffraction pattern 315 to determine the outer shape of each spot.

[0047] As shown in FIGS. 4 and 5, the diffraction pattern 310 of the single crystal area and the diffraction pattern 315 of the non-single crystal area have different pattern shapes. The pattern obtained from the single crystal area is composed of a plurality of periodic diffraction spots corresponding to the crystal structure. The pattern obtained from the non-single crystal area is composed of only one spot through which the beam has passed.

[0048] As described above, the control unit 102 obtains a list indicating the coordinates, size, etc. of each spot through binarization processing and blob analysis. The control unit 102 may determine the irradiation target area by evaluating the number of diffraction spots with respect to the diffraction pattern obtained at the irradiation position to be evaluated. For example, when the number of spots in the pattern is 1 or less than a reference, the control unit 102 can determine that it is a non-single crystal region. Also, when the number of spots is more than the reference, the control unit 102 can determine that it is a single crystal region.

[0049] In another example, the control unit 102 can detect the boundary between the single crystal region 261 and the non-single crystal region 262 by moving the irradiation position of the electron beam and comparing the diffraction pattern obtained at each position with the diffraction pattern obtained at the initial position. As an example, the single crystal region 261 and the non-single crystal region 262 can be distinguished by comparing the position, size, or number, etc. of each spot in the diffraction pattern obtained by performing blob analysis on each of the diffraction patterns obtained at each position and the diffraction pattern obtained at the initial position.

[0050] The control unit 102 may evaluate the similarity between the diffraction pattern obtained at the initial position, which is the reference irradiation position, and the diffraction pattern obtained at the irradiation position to be evaluated. The control unit 102 calculates the similarity degree of the two diffraction patterns and determines the position where the similarity degree becomes a threshold value as the boundary of the irradiation target area.

[0051] The similarity degree of the two patterns can be calculated, for example, from the match / mismatch of the luminance values of each pixel of the diffraction pattern. When the total number of pixels whose luminance value difference exceeds a predetermined reference is smaller than the threshold value, it may be determined that the two diffraction patterns are similar. Note that the calculation method of the similarity degree of the diffraction pattern can be appropriately determined by design. Note that more accurate comparison is possible by blob analysis, but it may be omitted.

[0052] Figures 4 and 5 show diffraction patterns consisting of a plurality of spots arranged in a two-dimensional array. Such a diffraction pattern is obtained on the diffraction plane by irradiating a sample with a parallel electron beam. As an example of another diffraction pattern, a Ronchigram can be used. A Ronchigram is a diffraction pattern formed on the diffraction plane when the beam irradiating the sample is converged.

[0053] Figure 6 shows examples of a single crystal region, a non-single crystal region, and a non-transmission region of an electron beam, which are discriminated based on a diffraction pattern in the observation image shown in Fig. 3A. The single crystal region 351 coincides with the substrate region (single crystal region) 201 shown in Fig. 3B. The non-transmission region 353 coincides with the regions of the support portion 207 and the base portion 208 in Fig. 3A. The non-single crystal region 352 is composed of the element region 203 shown in Fig. 3B and the vacuum region in Fig. 3A.

[0054] Figure 7 shows a flowchart of an example of a process for determining the boundary of a single crystal region. In this example, as described above, the control unit 102 discriminates a single crystal region based on the diffraction pattern of the sample.

[0055] First, the control unit 102 moves the stage 118 to a predetermined observation field of view (S101). At this time, the control unit 102 scans the sample with an electron beam to acquire an observation image of the sample by secondary electrons. Depending on the sample, instead of the secondary electron image, a bright field image or a dark field image can also be used. The control unit 102 moves the stage 118 so that the sample is at a predetermined position within the observation field of view by matching with a pattern held in advance. The control unit 102 determines an initial irradiation position for sample orientation alignment from the single crystal region (substrate region). The initial irradiation position may be specified in advance within the pattern.

[0056] Next, the control unit 102 sets the electron beam to spot irradiation (S102) and irradiates the electron beam to the initial position (S103). The control unit 102 acquires the diffraction pattern at the initial position and stores it in the storage device (S104).

[0057] Next, the control unit 102 moves the electron beam irradiation position (S105), acquires a new diffraction pattern, and stores it in the storage device (S106). The moving direction and moving distance may be determined based on preset control information. Details will be described later.

[0058] The control unit 102 determines whether the current irradiation position is the last irradiation target location in the current search area (S107). For example, one or a plurality of one-dimensional or two-dimensional search areas may be set for searching the irradiation target area. The search area is specified by its position and shape (size) with respect to the initial position, for example. The control unit 102 sequentially irradiates a spot-shaped electron beam at different positions in each specified search area to acquire a diffraction pattern. When the irradiation position reaches the edge of the current search area, it is determined that the location is the last irradiation target location.

[0059] Next, the control unit 102 discriminates the single crystal area within the obtained one-dimensional / two-dimensional area (S108). As a method for discriminating the single crystal area, for example, the similarity between the diffraction pattern at the initial position and each of the acquired diffraction patterns is calculated, and the position where the similarity exceeds the threshold is determined as the boundary of the single crystal area.

[0060] Next, the control unit 102 determines whether evaluation of different areas is necessary (S109). If the evaluation of all the preset search areas has been completed, evaluation of different areas is not necessary (S109: NO). If unevaluated areas remain, evaluation of those areas is necessary (S109: YES).

[0061] If unevaluated areas remain (S109: YES), the control unit 102 returns to step S103. If the evaluation of all search areas has been completed (S109: NO), the control unit 102 determines the single crystal area within the field of view from the discrimination result obtained in step S108 (S110).

[0062] FIG. 8 shows an example of a search area. In the example of FIG. 8, one two-dimensional search area 401 is specified. The two-dimensional search area 401 is a rectangle that includes the substrate area 201 with the initial position as the center. The control unit 102 scans the two-dimensional search area 401 with an electron beam to obtain a diffraction pattern at each irradiation position.

[0063] The control unit 102, for example, moves the irradiation position of the electron beam at a constant pitch from the left end to the right end of the two-dimensional search area 401 and obtains a diffraction pattern at each movement destination. When the irradiation position reaches the right end, the control unit 102 moves the electron beam to a position that is a predetermined distance below the previous irradiation position at the left end of the two-dimensional search area 401. The control unit 102 repeats the above process to obtain a diffraction pattern over the entire two-dimensional search area 401.

[0064] Note that the search area can have an arbitrary shape including the initial position. For example, the search area and the observation field area may coincide.

[0065] FIG. 9 shows an example of a search area. In the example of FIG. 9, two one-dimensional search areas 411 and 412 are specified. In the example shown in FIG. 9, the one-dimensional search area 411 is a straight line (axis) that passes through the initial position 211 and extends in the left-right direction. The one-dimensional search area 412 is a straight line (axis) that passes through the initial position 211 and extends in the up-down direction. The angle formed by the one-dimensional search areas 411 and 412 is a right angle.

[0066] In the example shown in FIG. 9, the substrate area 201, which is a single crystal area, is rectangular (including a square). The one-dimensional search area 411 is parallel to one side of the substrate area 201, and the one-dimensional search area 412 is parallel to the side adjacent to the above one side. Therefore, the boundary of the single crystal area can be estimated from the four single crystal area boundary positions in the one-dimensional search areas 411 and 412. Note that the two one-dimensional search areas are non-parallel, but their angles do not have to be right angles. Also, the one-dimensional search area does not have to pass through the initial position.

[0067] The control unit 102, for example, acquires diffraction patterns at a plurality of points in the one-dimensional search region 411, discriminates the single crystal region, then acquires diffraction patterns at a plurality of points in the one-dimensional search region 412, and discriminates the single crystal region.

[0068] First, on the one-dimensional search region 411, the control unit 102 moves the electron beam in the right direction from the initial position 211 at a constant pitch, and acquires a diffraction pattern at each position. Thereafter, on the one-dimensional search region 411, the control unit 102 moves the electron beam in the left direction from the initial position 211 at a constant pitch, and acquires a diffraction pattern at each position. Also, the movement on the one-dimensional search region 411 does not necessarily have to start from the initial position 211, and the electron beam may be moved at a constant pitch from one end of the one-dimensional search region 411 toward the other end. The control unit 102 identifies the boundary position of the single crystal region on the one-dimensional search region 411 by analyzing the diffraction pattern.

[0069] Next, on the one-dimensional search region 412, the control unit 102 moves the electron beam in the upward direction from the initial position 211 at a constant pitch, and acquires a diffraction pattern at each position. Thereafter, on the one-dimensional search region 412, the control unit 102 moves the electron beam in the downward direction from the initial position 211 at a constant pitch, and acquires a diffraction pattern at each position. Also, the movement on the one-dimensional search region 412 does not necessarily have to start from the initial position 211, and the electron beam may be moved at a constant pitch from one end of the one-dimensional search region 412 toward the other end. The control unit 102 identifies the boundary position of the single crystal region on the one-dimensional search region 412 by analyzing the diffraction pattern.

[0070] In one embodiment of this specification, the control unit 102 may identify the single crystal region boundary without referring to the designated search region. Each time the control unit 102 acquires a diffraction pattern at one or a plurality of irradiation positions in the one-dimensional search region, the control unit 102 compares the diffraction pattern at the initial position with the newly acquired diffraction pattern. The control unit 102 determines a position where the similarity is less than the threshold value as the boundary position of the single crystal region in the one-dimensional search region.

[0071] The control unit 102 executes similar processing in a plurality of one-dimensional search regions extending radially from the initial position. By connecting the single crystal region boundary positions of all the one-dimensional search regions, the single crystal region can be identified.

[0072] In the following, other example methods for determining an irradiation target region for obtaining a diffraction pattern for sample orientation adjustment will be described. In one embodiment of the present specification, the control unit 102 may be determined using a plurality of scanning transmission microscope images obtained using signal components at different scattering angles. Examples of these plurality of scanning transmission microscope images are a bright field image (bright field signal) and a dark field image (dark field signal) of the sample. The observation image can be obtained in a shorter time than the diffraction pattern.

[0073] Since the electron beam undergoes strong diffraction in the single crystal region, the on-axis (zeroth-order) electron beam intensity decreases and the surrounding electron beam intensity increases. The on-axis intensity approximately corresponds to the bright field signal intensity, and the surrounding intensity approximately corresponds to the dark field signal intensity. The bright field image and the dark field image have a complementary relationship, and the sum of their intensities can be approximately regarded as a certain constant value.

[0074] The control unit 102 generates an image representing the comparison result between the bright field image and the dark field image. The comparison result image can be generated, for example, using the difference value between the luminance value of each pixel in the bright field image and the luminance value (intensity value) of each pixel in the dark field image. The control unit 102 performs image analysis on the generated difference image and identifies a single crystal region having the same structure (including crystal orientation) as the initial position. The method of image analysis is arbitrary, and a continuous region including the initial position and composed of pixels with luminance within a predetermined range from the luminance at the initial position may be regarded as the single crystal region.

[0075] In another example, the control unit 102 may refer to the bright field image and the dark field image independently. In both the bright field image and the dark field image, a region determined as a single crystal region according to the luminance of the pixels as described above may be determined as the single crystal region of the sample.

[0076] In one embodiment of the present specification, the control unit 102 determines the irradiation target area based on signals from different areas of the split detector. This enables high-speed processing. For example, an annular dark-field detector can be divided into a plurality of areas in the circumferential and radial directions. Different divided areas detect scattered electron components with different scattering directions or scattering angles. As an example, the control unit 102 calculates the difference between signals detected in different areas on the detector. In a single-crystal area and a non-single-crystal area or an area having a different crystal orientation, the diffraction patterns formed on the detector are significantly different, so the amount of signal obtained in each divided detection area varies greatly. Therefore, the difference between signals detected in different areas on the detector is significantly different between the single-crystal area and other areas. In addition, it is also possible to determine the area by using the ratio, product, etc. of the signals.

[0077] The control unit 102 may define as a single-crystal area a continuous area including the initial position, where the difference in the aforementioned detection signals at the position is within a predetermined range of difference values with respect to the difference in the detection signals at the initial irradiation position. The position where the intensity of the difference changes beyond the threshold value is determined as the boundary between the single-crystal area and the non-single-crystal area.

[0078] In one embodiment of the present specification, after determining the initial position of the sample, the control unit 102 may determine the irradiation target area from the information of the sample to be measured that is held in advance, regardless of the detection signal of the sample. For example, the control unit 102 holds information defining the position and shape of the irradiation target area with reference to the initial position, and determines the area indicated by the information as the irradiation target area.

[0079] FIG. 10 shows a configuration example of the sample information stored in the control unit 102 in the storage device. The sample information manages information about the sample to be observed. The control unit 102 can refer to the sample information for adjusting the orientation of the sample.

[0080] The example of sample information shown in FIG. 10 has a table structure including a plurality of columns 501 to 511. The sample number column 501 indicates a number for identifying the sample to be measured, and the sample grid number column 502 indicates a number for identifying the grid where the sample is installed.

[0081] The sample mounting position number column 503 in the grid indicates a number corresponding to the location where the sample is mounted on the sample grid. The described number indicates the number of the semi-circular mesh-shaped sample mounting protrusions and the number of the coordinates (address) within the protrusions, or the coordinates on the mesh where regions are provided in a grid pattern. Once the mounting position number is determined, it is determined at which address (X: ~μm, Y: ~μm) on the grid the sample is attached. Note that the position of the sample may be slightly shifted from the reference position within each address depending on the mounting condition of the sample.

[0082] The sample position correction coordinate X column 504 and the sample position correction coordinate Y column 505 indicate the amount by which the sample is shifted from the reference position of the mounting location. The sample rotation angle column 506 indicates the angle by which the sample is tilted with respect to the horizontal reference within the grid. It indicates the angle (in-plane rotation amount) for correcting (rotating) the direction of beam irradiation during observation. Note that the tilt amounts of the α-axis and β-axis of the sample stage are angles in a direction perpendicular to the plane and are different from the sample rotation angle.

[0083] The width column 507 and the height column 508 of the observable region respectively indicate the width and height of the observable region of the sample. The observable region is the region in the sample that has been thinned and through which the electron beam can pass and be observed. In the example shown in FIG. 3A, the thinned region 202 is the observable region.

[0084] The distance column 509 from the sample end to the crystal region end indicates the distance from the sample end to the crystal region end (single crystal region end). The width column 510 of the crystal region indicates the width of the crystal region (single crystal region) including the initial position in the sample. The height column 511 of the crystal region indicates the height of the crystal region (single crystal region) including the initial position in the sample.

[0085] The parameters indicated by columns 507 to 511 have the following relationships. Width of observable region = Width of single crystal region Height of observable region = Distance from sample end to single crystal region + Height of single crystal region

[0086] After the control unit 102 aligns the sample within the observation field of view and identifies the initial position, it may determine the irradiation target region for obtaining a diffraction pattern for azimuth adjustment from the initial position and the sample information. For example, the initial position is the center of the single crystal region, and the irradiation target region is determined based on the single crystal region indicated by the sample information. For example, it may be determined as a region inside by a preset numerical value within the single crystal region. Alternatively, if a predetermined size is set in advance for the irradiation target region and it can be determined from the sample information that the single crystal region within the sample is not smaller than the predetermined size, irradiation may be performed on the region of the predetermined size.

[0087] The sample information may be referred to for determining the search region described with reference to FIG. 8 or FIG. 9. For example, in the example shown in FIG. 8, the initial position is the center of the single crystal region, and the two-dimensional search region 401 may include the single crystal region indicated by the sample information and be determined as a region larger than the single crystal region by a predetermined size. In the example shown in FIG. 9, the one-dimensional search regions 411 and 412 are determined according to the height and width of the single crystal region, and may be set, for example, to be a predetermined number longer than them.

[0088] Hereinafter, the sample azimuth adjustment process will be described. FIG. 11 is a flowchart of an example of the sample azimuth adjustment process. The sample azimuth adjustment process is executed after the irradiation target region for obtaining a diffraction pattern is determined.

[0089] First, in step S201, the control unit 102 acquires the current sample stage tilt amount (A). The sample stage tilt amount can be represented, for example, by the tilt angles on two different axes of the α-axis and the β-axis.

[0090] Next, in step S202, the control unit 102 adjusts the sample stage to the inclination amount (B) corresponding to the initial conditions used for adjustment. The initial conditions are set in advance within the control unit 102.

[0091] Next, in step S203, the control unit 102 calculates the difference between the sample stage inclination amount (A) and the sample stage inclination amount (B). Further, in step S204, the control unit 102 calculates the inclination change amount (C) from the difference.

[0092] In step S205, the control unit 102 determines the irradiated target area after inclination from the information on the single crystal area obtained in advance and the inclination change amount (C). The information on the single crystal area obtained in advance is shown in the width column 510 of the single crystal area and the height column 511 of the single crystal area in the sample information described with reference to FIG. 10.

[0093] When the sample is inclined, the apparent upper area of the single crystal area as seen from the observation direction (the axial direction in which the primary beam is irradiated) changes. When the normal line of the single crystal area coincides with the observation direction, the observed single crystal area and the actual single crystal area coincide. However, when the single crystal area is inclined with respect to the observation direction, the shape of the single crystal area seen in the observation direction changes to a shape (size) corresponding to the angle. Step S205 determines the irradiated target area of the primary electron beam that changes according to the angle of the sample.

[0094] Next, in step 206, the control unit 102 scans the electron beam within the irradiated target area determined in step S205. In step S207, the control unit 102 acquires the diffraction pattern of the irradiated target area.

[0095] Next, in step S208, the control unit 102 changes the inclination amount of the sample stage. The change direction and the change amount follow a predefined setting. In step S209, the control unit 102 determines a new irradiated target area from the information on the single crystal area obtained in advance and the current stage inclination amount. The processing of this step is the same as that of step S205.

[0096] Next, in step 210, the control unit 102 scans the electron beam within the irradiation target area determined in step S209. In step S211, the control unit 102 acquires the diffraction pattern of the irradiation target area.

[0097] In step S212, the control unit 102 determines whether acquisition has been completed for all target tilt conditions. If unmeasured tilt conditions remain (S212: NO), the flow returns to step S208. If measurement for all tilt conditions has been completed (S212: YES), the flow proceeds to step S213.

[0098] In step S213, the control unit 102 calculates the optimal tilt amount of the sample for sample measurement from the diffraction patterns obtained at different multiple tilt angles. Further, in step S214, the control unit 102 adjusts the tilt amount of the sample stage to the calculated conditions. If no additional adjustment is required (S215: NO), the control unit 102 ends this flow. If additional adjustment is required, the flow returns to step S208.

[0099] As described above, the control unit 102 moves the irradiation position of the electron beam in the irradiation target area and acquires the diffraction pattern based on the detection results of the detector at different irradiation positions. The control unit 102 controls the sample stage 108 based on the analysis result of the diffraction pattern to adjust the tilt of the sample. There are several methods for acquiring the diffraction pattern. In one method, the detector 121 continuously detects the signal from the sample while the irradiation position of the electron beam is moving and generates a diffraction pattern. One diffraction pattern is generated from the continuously detected signals.

[0100] In another method, the control unit 102 generates a diffraction pattern from the diffraction patterns of the detector 121 detection signals at different irradiation positions. For example, the control unit 102 generates a new diffraction pattern by summing or averaging a plurality of diffraction patterns acquired by the detector 121 at different irradiation positions of the electron beam.

[0101] As described above, in step S213, the control unit 102 determines an optimal sample orientation from the diffraction patterns obtained at a plurality of different tilt angles. Various methods for determining the optimal sample orientation are known, and the control unit 102 may use any of these methods. The methods described below each enable the determination of the optimal sample orientation.

[0102] For example, the control unit 102 acquires diffraction patterns under a plurality of conditions in which the sample tilt angle is changed, and controls the angle of the sample stage 118 based on the positions of the spots included in the diffraction patterns. For example, the control unit 102 fits a circle to the spot group on each pattern and measures the distance and direction from the center of the circle to the center position of the diffraction pattern. The control unit 102 can determine appropriate tilt conditions from the change in the measurement results with respect to the tilt angle. Alternatively, the control unit 102 may evaluate the correlation coefficient between the diffraction patterns obtained under each condition in which the sample is tilted and the diffraction pattern (reference) in the target orientation. The orientation at which the correlation value is maximized can be determined as the optimal sample orientation.

[0103] Another method is to utilize the Kikuchi pattern. In a transmission electron microscope, the plane near the objective lens focus where the irradiated beam converges to a point is called the diffraction plane, and the pattern formed on that plane is called the diffraction pattern. In particular, when the beam irradiating the sample is converged (non-parallel), the pattern formed in the shape of a diffraction plane is called a Ronchigram. A Ronchigram is a type of convergent beam electron diffraction pattern (CBED Pattern). The diffraction pattern includes the spot-like pattern formed when the above beam converges to a point and the Ronchigram.

[0104] The Kikuchi pattern is a linear pattern formed on the diffraction plane when an electron beam irradiates a crystalline material. The Kikuchi pattern appears in a superimposed form on any of the spot-like pattern or the Ronchigram diffraction patterns.

[0105] The control unit 102 acquires a diffraction pattern including a plurality of Kikuchi lines, and controls the angle of the sample stage 118 based on the positions of the Kikuchi lines included in the diffraction pattern. For example, the control unit 102 calculates the zone axis of the sample by performing an analysis based on a plurality of intersections where two Kikuchi lines intersect. The control unit 102 can calculate the tilt angle, which is the angle for tilting the sample, based on the zone axis and the irradiation direction of the electron beam.

[0106] For example, for each of a plurality of triangles formed from the intersections of a plurality of Kikuchi lines, the control unit 102 can calculate the center and radius of the inscribed circle, and calculate the zone axis of the sample based on the center and radius of the inscribed circle. Alternatively, the control unit 102 may calculate the coordinates where the sum of the distances from a plurality of intersections is minimized as the zone axis of the sample.

[0107] Note that the present invention is not limited to the above-described embodiments and includes various modifications. Regarding the content described by taking the apparatus configuration of STEM as an example, it can also be implemented in the apparatus configuration of TEM. Further, for example, the above-described embodiments are those in which the configuration is described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, it is possible to add, delete, or replace a part of the configuration of each embodiment with other configurations.

[0108] In addition, each of the above configurations, functions, processing units, processing means, etc. may be realized in hardware by designing a part or all of them, for example, by using an integrated circuit. Further, the present invention can also be realized by a program code of software that realizes the functions of the embodiments. In this case, a storage medium recording the program code is provided to a computer, and a processor included in the computer reads the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code itself and the storage medium storing it constitute the present invention. As a storage medium for supplying such a program code, for example, a flexible disk, CD-ROM, DVD-ROM, hard disk, SSD (Solid State Drive), optical disk, magneto-optical disk, CD-R, magnetic tape, non-volatile memory card, ROM, etc. are used.

[0109] Also, the program code for realizing the functions described in this embodiment can be implemented in a wide range of programs or script languages such as assembler, C / C++, perl, Shell, PHP, Python, Java, etc.

[0110] Furthermore, the program code of the software that realizes the functions of the embodiments may be distributed via a network, stored in a storage means such as a hard disk or memory of a computer or a storage medium such as a CD-RW or CD-R, and the processor included in the computer may read and execute the program code stored in the storage means or the storage medium.

[0111] In the above embodiments, the control lines and information lines indicate those considered necessary for explanation, and not necessarily all control lines and information lines are shown on the product. All components may be interconnected.

Claims

1. A moving mechanism that holds and moves a sample, A particle source that outputs a charged particle beam, A detector that detects a signal generated by irradiating the sample with the charged particle beam, A controller that controls the moving mechanism, the particle source, and the detector, and The controller Determines an irradiation target region in the sample according to the sample, Moves the irradiation position of the charged particle beam in the irradiation target region, and obtains a diffraction pattern based on the detection results of the detector at different irradiation positions, A charged particle beam device that controls the moving mechanism based on the analysis result of the diffraction pattern to adjust the inclination of the sample.

2. The charged particle beam device according to Claim 1, The controller Pre-holds sample information including information on the structure of the sample, A charged particle beam device that determines the irradiation target region based on the sample information.

3. The charged particle beam device according to Claim 1, The irradiation target region is a single crystal region in the sample, A charged particle beam device in which the controller determines the single crystal region based on the detection signal of the detector.

4. The charged particle beam device according to Claim 1, The detector continuously detects the signal while the irradiation position is moving in order to generate the diffraction pattern, a charged particle beam device.

5. The charged particle beam device according to Claim 1, A charged particle beam device in which the controller generates the diffraction pattern to be analyzed from the diffraction patterns of the detection signals at each of the different irradiation positions.

6. The charged particle beam device according to Claim 1, A charged particle beam device in which the controller controls the moving mechanism based on the position of the spots included in the diffraction pattern.

7. The charged particle beam device according to Claim 1, A charged particle beam device in which the controller controls the moving mechanism based on the position of the Kikuchi lines included in the diffraction pattern.

8. The charged particle beam device according to Claim 1, A charged particle beam device in which the controller determines the irradiation target region by evaluating the similarity between the diffraction pattern obtained at a reference irradiation position and the diffraction pattern obtained at an irradiation position to be evaluated.

9. The charged particle beam device according to Claim 1, The controller determines the irradiation target region by evaluating at least one of the number or position of diffraction spots with respect to a diffraction pattern obtained at an irradiation position to be evaluated, the charged particle beam apparatus.

10. The charged particle beam apparatus according to claim 1, wherein the controller determines the irradiation target region using diffraction patterns obtained at a plurality of irradiation positions where the irradiation positions are changed with respect to two different directions, the charged particle beam apparatus.

11. The charged particle beam apparatus according to claim 1, wherein the controller determines the irradiation target region using a plurality of signal components corresponding to different scattering angles, the charged particle beam apparatus.

12. The charged particle beam apparatus according to claim 1, wherein the controller determines the irradiation target region using a plurality of signal components corresponding to different scattering directions, the charged particle beam apparatus.

13. A method for controlling a charged particle beam apparatus that observes a sample by irradiating a charged particle beam, wherein the charged particle beam apparatus includes a moving mechanism that holds and moves a sample, a particle source that outputs a charged particle beam, and a detector that detects a signal generated by irradiating the charged particle beam onto the sample, the control method includes a controller determining the irradiation target region in the sample according to the sample, moving the irradiation position of the charged particle beam in the irradiation target region, and acquiring a diffraction pattern based on the detection signal of the detector at different irradiation positions, and controlling the moving mechanism based on the analysis result of the diffraction pattern to adjust the inclination of the sample, the control method of the charged particle beam apparatus.

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