Charged particle beam device and processing method

Abstract

This charged particle beam device comprises: a particle source that outputs a charged particle beam; a stage that holds a sample; an optical system that adjusts the irradiation direction and the focal position of the charged particle beam with respect to the sample; a detector that detects a signal for generating an observation image of the sample; and a control unit. The control unit acquires an observation image of the sample, calculates an evaluation value for evaluating the degree of deviation of the focal position of an image for each of a plurality of regions in the observation image, and generates information regarding the three-dimensional shape of the sample on the basis of the evaluation values for the plurality of regions.

Description

Charged particle beam device and processing method

[0001] The present invention relates to a charged particle beam device.

[0002] When observing a sample using an electron microscope such as a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM), it is necessary to appropriately adjust the direction of the sample relative to the direction of the charged particle beam. For example, it is necessary to make the surface of the sample approximately perpendicular or approximately parallel to the direction of the charged particle beam. In this specification, when there is no particular distinction between a transmission electron microscope and a scanning transmission electron microscope, they will be referred to as a scanning transmission electron microscope.

[0003] For example, as shown in Figure 7A, when the surface of the sample is parallel to a plane S perpendicular to the direction of the charged particle beam indicated by the arrow, a clear observation image as shown in Figure 7B is acquired. As shown in Figure 7C, when the surface of the sample is inclined with respect to plane S, a blurred observation image as shown in Figure 7D is acquired. This relationship is based on the fact that the interfaces of the structures within the sample are perpendicular to the surface of the sample. This holds true in many cases for observation objects such as semiconductor devices in which the orientations of the structures and interfaces within the observation object are properly controlled.

[0004] For samples with single-crystalline regions, the tilt of the sample plane can be determined using the diffraction pattern obtained by irradiating the single-crystalline region with a charged particle beam. This method cannot be applied to samples without single-crystalline regions.

[0005] A technique for determining the surface shape of a sample is known from Patent Document 1 (see, for example, the abstract).

[0006] Japanese Patent Application Laid-Open No. 2022-185757

[0007] The technology described in Patent Document 1 is related to a scanning electron microscope, and requires multiple detectors to grasp the shape of the sample surface. Furthermore, the image observed with a general scanning transmission electron microscope does not change depending on the angle of the detector relative to the sample, unlike the information acquired using the multiple detectors described in Patent Document 1, so it is difficult to apply the technology described in Patent Document 1 as is.

[0008] The present invention provides a technique for generating information for adjusting the tilt of a sample relative to the irradiation direction of a charged particle beam.

[0009] A representative example of the invention disclosed in the present application is as follows: That is, a charged particle beam device includes a particle source that outputs a charged particle beam, a stage that holds a sample, an optical system that adjusts the irradiation direction and focal position of the charged particle beam with respect to the sample, a detector that detects a signal for generating an observation image of the sample, and a controller that controls the optical system, the stage, and the detector, wherein the controller acquires the observation image of the sample, calculates an evaluation value for each of a plurality of regions of the observation image that evaluates the degree of shift in the focal position of the image, and generates information on the three-dimensional shape of the sample based on the evaluation values ​​of the plurality of regions.

[0010] According to one aspect of the present invention, it is possible to generate information for adjusting the tilt of a sample relative to the irradiation direction of a charged particle beam. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0011] FIG. 1 is a diagram illustrating an example of the configuration of a scanning transmission electron microscope according to a first embodiment. FIG. 2 is a flowchart illustrating an example of a correction process executed by a control system according to the first embodiment. FIG. 3 is a diagram illustrating an example of an observation image according to the first embodiment. FIG. 4 is a graph illustrating a relationship between an evaluation value and a current of an objective lens in the first embodiment. FIG. 5 is a diagram illustrating an example of a method for calculating a three-dimensional shape of a sample according to the first embodiment. FIG. 6 is a diagram illustrating a method for calculating an evaluation value by the control system according to the first embodiment. FIG. 7 is a diagram illustrating a method for calculating an evaluation value by the control system according to the first embodiment. FIG. 8 is a diagram illustrating a problem. FIG. 9 is a diagram illustrating a problem. FIG. 10 is a diagram illustrating a problem.

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention should not be construed as being limited to the description of the embodiments shown below. Those skilled in the art will readily understand that the specific configuration can be changed without departing from the spirit or intent of the present invention.

[0013] In the configuration of the invention described below, the same or similar configurations or functions are denoted by the same reference numerals, and redundant explanations will be omitted.

[0014] In this specification, the terms "first," "second," "third," etc. are used to identify components and do not necessarily limit the number or order.

[0015] To facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings etc. may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not limited to the position, size, shape, range, etc. disclosed in the drawings etc.

[0016] 1 is a diagram showing an example of the configuration of a scanning transmission electron microscope (STEM) according to Example 1. The present invention can also be applied to a transmission electron microscope (TEM).

[0017] The STEM 100 comprises an electron optical system column 101 and a control system 102 .

[0018] The electron optical system column 101 has an electron source 111, an electrode 112, a condenser lens 113, a condenser aperture 114, an axis adjustment deflector 115, an aberration correction device 116, a scan deflector 117, an objective lens 118, a stage 119, an objective aperture 120, an axis adjustment deflector 121, a selected area aperture 122, an imaging lens 123, and a detector 124.

[0019] The control system 102 is composed of a control device 141 and a computer 142. The control system 102 controls the electron optical system column 101 using multiple control circuits. More specifically, the control system 102 obtains values ​​of the target device via the control circuit and creates any desired electron optical conditions by inputting values ​​to the target device via the control circuit. The electron optical conditions include, for example, the focal position, the diameter and shape of the charged particle beam (probe), and aberration. The focal position can be controlled by adjusting the current of the objective lens 118. The astigmatism can be controlled by adjusting the current of the aberration corrector 116.

[0020] The control system 102 generates an image from the signal detected by the detector 124. The control system 102 of this embodiment analyzes the image and calculates the tilt of the sample with respect to a plane perpendicular to the direction of the charged particle beam. Furthermore, the control system 102 of this embodiment controls the electron optical system column 101 to reduce the tilt of the sample with respect to the plane.

[0021] Fig. 2 is a flowchart illustrating an example of correction processing executed by the control system 102 according to the first embodiment. Figs. 3A and 3B are diagrams illustrating an example of an observation image according to the first embodiment.

[0022] The control system 102 adjusts adjustment parameters corresponding to electron optical conditions and acquires a plurality of observation images (through-focus images) with different focal positions of the charged particle beam (step S101). At this time, the control system 102 stores the adjustment parameters and the observation images in association with each other.

[0023] Here, consider the case where the sample is inclined with respect to plane S, as shown in Fig. 3A. Plane S is a plane perpendicular to the direction of the charged particle beam. When a charged particle beam focused at position A is irradiated, an observation image such as that shown in Fig. 3B is acquired. The image at position A in the observation image is clear, but the images at other positions are blurred.

[0024] The control system 102 generates sample position information relating to the position of the sample in the direction of the charged particle beam using the multiple observation images (step S102). For example, the sample position information is generated in the following procedure.

[0025] (S102-1) The control system 102 selects one observation image and divides the observation image into a plurality of regions.

[0026] (S102-2) The control system 102 calculates an evaluation value for each region to evaluate the degree of image defocus. In this embodiment, the control system 102 calculates an evaluation value corresponding to sharpness. The method for calculating the evaluation value will be described later.

[0027] (S102-3) The control system 102 determines whether or not processing has been completed for all the observed images. If processing has not been completed for all the observed images, the control system 102 returns to S102-1.

[0028] (S102-4) When processing for all observed images is completed, the control system 102 calculates the current of the objective lens 118 that maximizes the evaluation value of each region, based on the evaluation value of each region. Fig. 4 is a graph showing the relationship between the evaluation value and the current of the objective lens 118 in Example 1.

[0029] The horizontal axis of the graph represents the current of the objective lens 118, and the vertical axis represents the evaluation value. The points on the graph represent the evaluation value calculated from the observed image. The curve represents a fitting function (Gaussian function) fitted to the evaluation value. Based on the fitting function, the control system 102 calculates the current (optimum current) of the objective lens 118 that maximizes the evaluation value.

[0030] (S102-5) The control system 102 calculates the focal position at which the specimen is in focus in each region based on the optimal current for each region. Note that the relationship between the excitation current of the objective lens 118 and the focal point is assumed to be defined in advance.

[0031] (S102-6) The control system 102 outputs the focal position of each region as sample position information. The focal position in each region can be used as information representing the position of the sample in the region in the direction of the charged particle beam.

[0032] This concludes the description of the process in step S102.

[0033] The control system 102 calculates the three-dimensional shape of the sample based on the sample position information (step S103). Here, the three-dimensional shape of the sample refers to the three-dimensional shape of the surface of the sample, the central plane in the thickness direction of the sample, or a plane corresponding to a specific depth position in the thickness direction of the sample that is determined according to the observation conditions.

[0034] FIG. 5 is a diagram illustrating an example of a method for calculating the three-dimensional shape of a sample in Example 1. The control system 102 estimates the three-dimensional shape of the sample by fitting a surface function to the focal position where the sample is in focus in each region using a RANSAC algorithm or the like, as shown in FIG. 5 . If the sample has a hole, the evaluation value of that region will be significantly different from that of other regions. By using a robust fitting method such as the RANSAC algorithm, fitting that excludes the evaluation values ​​of the aforementioned regions becomes possible. Note that the present invention is not limited to the method for estimating the three-dimensional shape of the sample. The control system 102 calculates the tilt angle between the sample and a plane perpendicular to the direction of the charged particle beam. In FIG. 5 , two tilt angles (X tilt angle and Y tilt angle) are calculated.

[0035] When the coordinates corresponding to the position in the field of view are expressed by two components, X and Y, the surface function used to estimate the three-dimensional shape of the sample can use a form that includes, in addition to a term consisting of linear coefficients of X and Y, a term consisting of quadratic or higher order coefficients of X and Y. In this case, the linear coefficients of X and Y correspond to the linear change of the sample surface in each coordinate axis direction, i.e., the amount of tilt, and the quadratic or higher order coefficients correspond to the warp or deflection of the sample surface.

[0036] If a sample is warped or bent, the tilt of the sample may vary depending on the region within the observation field of view. In this case, the average tilt of the entire sample can be calculated using the first-order coefficients described above. To accurately calculate the tilt of a local region on the sample, second-order or higher coefficients can be used to obtain the local tilt. This allows accurate adjustment of the tilt of a sample to the local region being observed, even for samples with warping or bends.

[0037] In this case, methods for expressing the warp or deflection of the sample can be used, such as using a high-order polynomial, or by interpolating a portion of the distribution of focal positions where the sample is in focus in each measured region.

[0038] The control system 102 calculates an optimal tilt control angle based on the three-dimensional shape of the sample (step S104). For example, if the three-dimensional shape of the sample is substantially flat, the control system 102 calculates the tilt angle between a plane perpendicular to the direction of the charged particle beam and the sample surface. In FIG. 5 , two tilt angles (X tilt angle, Y tilt angle) are calculated. The control system 102 calculates the difference between the two tilt angles and a target tilt angle as the optimal tilt control angle. For example, if the three-dimensional shape of the sample is not substantially flat, the control system 102 calculates the tilt angle between a plane perpendicular to the direction of the charged particle beam and a plane formed by a local region specified by the user.

[0039] The control system 102 corrects the stage 119 and the focus based on the optimum tilt control angle and information on the three-dimensional shape of the sample (step S105).

[0040] The control system 102 determines whether to end the correction (step S106). For example, if the number of corrections is greater than a predetermined value, the control system 102 ends the correction. Furthermore, the control system 102 calculates the amount of tilt of the sample with respect to a plane perpendicular to the direction of the charged particle beam using the observation image acquired after the correction, and ends the correction if the amount of tilt is small.

[0041] The control system 102 may acquire an observation image and then calculate the evaluation value of each region of the image. That is, the control system 102 may calculate the evaluation value in parallel with the acquisition of the observation image. This allows for efficient calculation.

[0042] Although the reference plane for calculating the tilt angle is a plane perpendicular to the direction of the charged particle beam, a similar effect can be achieved by using a different plane as the reference plane. For example, a tilt angle calculated using a plane inclined at a known fixed angle with respect to a plane perpendicular to the direction of the charged particle beam as the reference plane can be used as a tilt angle with respect to a plane substantially perpendicular to the direction of the charged particle beam by subtracting the known fixed angle from the calculated tilt angle. Because the angle reference can be determined arbitrarily, the reference plane for calculating the tilt angle is not limited to a plane perpendicular to the direction of the charged particle beam and can be arbitrarily set by the user. Examples of arbitrarily set reference planes include a plane perpendicular to the direction of the charged particle beam, a reference horizontal plane in the design of the stage, and a central axis in the design of the electron optical system column.

[0043] Here, a method for calculating the evaluation value will be described. In this embodiment, an evaluation value for evaluating sharpness is calculated using an observed image to which a wavelet transform has been applied. The wavelet transform converts an image into wavelets (small localized waves / bases) that are superimposed with different scales and positions. This makes it possible to evaluate local frequency information while maintaining the positional information of the image.

[0044] The wavelet transform will now be described. It is assumed that the scaling function φ(x) and the wavelet function ψ(x) satisfy the two-scale relationship shown in equations (1) and (2).

[0045]

[0046]

[0047] Any function f ｊ (x) can be decomposed into two functions as shown in equation (3).

[0048]

[0049] where j is the level of the wavelet transform, s （ｊ） is the scaling factor for level j, w （ｊ） is the wavelet coefficient at level j. （ｊ） and w （ｊ） is expressed as in equations (4) and (5).

[0050]

[0051]

[0052] Here, p ｋ is the scaling filter, q ｋ are wavelet filters, and they have a relationship known as a quadrature mirror filter. Several filters that hold true under certain conditions are known, and a representative example is the Daubechie wavelet. As an example, the Daubechie wavelet with support 4 is shown in Equations (6) and (7).

[0053]

[0054]

[0055] p ｋ is a low-pass filter, q ｋ acts as a high-pass filter, so the function f ｊ The coefficient s obtained by expanding (x) （ｊ） , w （ｊ） are respectively f ｊ (x) corresponds to the low frequency component and high frequency component. （ｊ） Filter again ｋ、 q ｋ By applying （ｊ＋１） , w （ｊ＋１） By repeating this, f ｊ (x) can be expanded in the form shown in equation (8).

[0056]

[0057] Each component of the obtained g(x) corresponds to a frequency component with a period that differs by two times in resolution. This is multi-resolution analysis using the discrete wavelet transform. Below is an example of applying multi-resolution analysis using the discrete wavelet transform to a two-dimensional array f(m, n). When f(m, n) is multiplied by a level 0 scaling function s （０） Considering (m, n), the transformation along the m-axis is shown as in equations (9) and (10).

[0058]

[0059]

[0060] Further obtained s （ｊ＋１、ｘ） (m, n), w （ｊ＋１、ｘ） When (m, n) is transformed along the n-axis, four components are obtained as shown in equations (11), (12), (13), and (14).

[0061]

[0062]

[0063]

[0064]

[0065] The above four components are expressed as in equations (15), (16), (17), and (18).

[0066]

[0067]

[0068]

[0069]

[0070] s （ｊ＋１） (m, n) is s （ｊ） Low frequency components of (m, n), w （ｊ＋１、ｈ） (m, n) is the direction along the m axis (horizontal direction), w （ｊ＋１、ｖ） (m, n) is the direction along the n axis (vertical direction), w （ｊ＋１、ｄ） (m, n) is the high frequency component in the diagonal direction.

[0071] The control system 102 （ｊ＋１、ｈ） (m, n) and / or w （ｊ＋１、ｖ） Based on (m, n), an evaluation value for each region is calculated.

[0072] 6A, 6B, and 6C are diagrams for explaining a method for calculating an evaluation value by the control system 102 according to the first embodiment.

[0073] 6A shows an observed image 600, FIG. 6B shows a horizontal wavelet transform image (1HL) 601 at level 1 of the observed image, and FIG. 6C shows a vertical wavelet transform image (1LH) 602 at level 1 of the observed image.

[0074] The horizontal wavelet transformed image 601 is （１、ｈ） (m, n) and shows the high frequency components (image changes) of the observed image 600 in the horizontal direction. （１、ｖ） (m, n) and show the high-frequency components (image changes) of the observed image 600 in the vertical direction. In the horizontal wavelet-transformed image (1HL) 601 and the vertical wavelet-transformed image (1LH) 602, changes from bright to dark regions are shown by bright lines, and the greater the change, the brighter the line (closer to white). Changes from dark to bright regions are shown by dark lines, and the greater the change, the darker the line (closer to black).

[0075] As described above, the wavelet transform of the low-frequency component image ((j+1)LL) at level j+1 can produce the horizontal wavelet transform image ((j+2)HL) and vertical wavelet transform image ((j+2)LH) at level j+2. Images at higher levels represent information with lower spatial frequencies (resolution).

[0076] Within a sample, especially in regions containing structures such as edges, when the image is in focus, the intensity change in the image is steep, and the absolute value of the wavelet transform coefficients is large. Conversely, when the image is out of focus, the image intensity in that region is relatively gradual, as information from a wider area than in the in-focus condition is used to obtain the image intensity, and the absolute value of the wavelet transform coefficients is small. Therefore, the absolute value of the wavelet transform coefficients indicates the degree of focus deviation.

[0077] In this embodiment, the control system 102 determines an evaluation value for a region based on the horizontal wavelet transform coefficients and / or vertical wavelet transform coefficients of an arbitrary level j+1. For example, the control system 102 calculates the absolute value of the horizontal wavelet transform coefficients of level 1 as the horizontal evaluation value of the observed image, and calculates the absolute value of the vertical wavelet transform coefficients of level 1 as the vertical evaluation value of the observed image. The control system 102 determines an overall evaluation value for the observed image using the horizontal evaluation value and the vertical evaluation value. As the overall evaluation value, the horizontal evaluation value or the vertical evaluation value may be used as is. However, when the sample has structural variations mainly in only one direction or when the astigmatism deviates from the optimal condition, it is desirable to calculate the overall evaluation value using both the horizontal evaluation value and the vertical evaluation value in order to determine the optimal condition. A typical example is to calculate the product of the two as the overall evaluation value for the observed image.

[0078] The absolute values ​​of the wavelet transform coefficients may be determined from noise-removed data or from an image that has undergone information restoration processing using techniques such as neural networks, compressed sensing, etc. Although several algorithms are known as methods for obtaining wavelet transform coefficients, the type of algorithm is not important in the present invention.

[0079] The overall evaluation value may be a horizontal evaluation value, a vertical evaluation value, or a value calculated by the sum, geometric mean, or arithmetic mean of the horizontal and vertical evaluation values.

[0080] The evaluation value may be calculated using a differential filter, a Sobel filter, a Prewitt filter, a Laplacian filter, a kernel filter, a discrete wavelet transform, a Fourier transform, a discrete cosine transform, a correlation function, or the like.

[0081] Similar processing can be achieved using an observation image obtained using a charged particle beam with astigmatism. In this case, if the relationship between the shape of the charged particle beam and the current of the aberration corrector 116 is known in advance, sample position information can be generated from this relationship.

[0082] It is not necessary to use the observation image obtained using the transmitted electron beam. For example, a detector that measures reflected electrons or secondary electrons may be provided, and the correction observation image may be obtained using the detector.

[0083] According to Example 1, even if the sample does not have a single crystal region, the three-dimensional shape of the sample can be calculated, and further, the tilt of the sample can be calculated. Furthermore, automatic correction for reducing the tilt of the sample relative to the aforementioned plane can be performed at high speed.

[0084] The second embodiment differs from the first embodiment in that sample position information is generated using a small number of observation images. The second embodiment will be described below, focusing on the differences from the first embodiment.

[0085] The configuration of the scanning transmission electron microscope of the second embodiment is the same as that of the first embodiment. The flow of processing executed by the control system 102 of the second embodiment is also the same as that of the first embodiment. However, the method of generating sample position information is different.

[0086] Here, a method for generating sample position information from one observation image will be described. First, the control system 102 divides the observation image into multiple regions and calculates an evaluation value for each region. The method for calculating the evaluation value is the same as in Example 1. The control system 102 calculates the degree of change in the evaluation value between adjacent regions. The degree of change in the evaluation value is correlated with the difference in elevation between the sample position in the irradiation direction of the charged particle beam. The correlation between the change in the evaluation value and the deviation from the focal position can be determined theoretically or experimentally. Therefore, based on this correlation, the control system 102 generates the relationship between the relative height of the sample within the observation field from the degree of change in the evaluation value as sample position information. Note that the correlation here includes correlations other than linear correlations.

[0087] If the degree of image blur changes symmetrically with the amount of focal position shift, it is difficult to determine the vertical relationship of the sample position from a single observation image, but it is possible to determine the absolute value of the tilt angle. Therefore, the control content can be adjusted based on the determined tilt angle, and by combining it with other auxiliary information, the amount of sample tilt can be corrected from information about the sample surface.

[0088] On the other hand, the control system 102 generates sample position information from multiple observation images and integrates each piece of sample position information to output sample position information that represents the relative height relationship within the observation field, including the up-down relationship.

[0089] In addition, when an optical system having an aberration component other than focus is used, sample position information representing the relative height relationship within the observation field, including the vertical relationship of height, can be generated from a single observation image. As a specific example, when the optical system has two-fold symmetric astigmatism, horizontal and vertical evaluation values ​​are calculated as the evaluation values ​​for the region. When the optical system has astigmatism, the shape of the charged particle beam differs between the regions before and after the circle of least confusion. Therefore, the evaluation values ​​for an image obtained by irradiating a sample with a charged particle beam upstream of the circle of least confusion and an image obtained by irradiating a sample with a charged particle beam downstream of the circle of least confusion differ in the direction of image blur. By utilizing these characteristics, the vertical relationship of relative heights within the observation field can be determined.

[0090] According to the second embodiment, the three-dimensional shape of the sample can be calculated from a small number of observation images, and automatic correction for reducing the tilt amount of the sample relative to the aforementioned surface can be performed at high speed.

[0091] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments are provided to explain the present invention in detail, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, some of the configurations of each embodiment can be added to, deleted from, or replaced with other configurations.

[0092] Furthermore, some or all of the above-described configurations, functions, processing units, processing means, etc. may be implemented in hardware, for example, by designing them as integrated circuits. The present invention can also be realized by software program code that implements the functions of the embodiments. In this case, a storage medium on which the program code is recorded 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 implements the functions of the above-described embodiments, and the program code itself and the storage medium on which it is stored constitute the present invention. Examples of storage media for providing such program code include flexible disks, CD-ROMs, DVD-ROMs, hard disks, solid-state drives (SSDs), optical disks, magneto-optical disks, CD-Rs, magnetic tape, non-volatile memory cards, and ROMs.

[0093] Furthermore, the program code that realizes the functions described in this embodiment can be implemented in a wide range of programming or scripting languages, such as assembler, C / C++, perl, Shell, PHP, Python, and Java.

[0094] Furthermore, the program code of the software that realizes the functions of the embodiments may be distributed via a network and stored in a storage means such as a computer's hard disk or memory, or in a storage medium such as a CD-RW or CD-R, and the processor of the computer may read and execute the program code stored in the storage means or the storage medium.

[0095] In the above-described embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all control lines and information lines are necessarily shown in the product. All components may be interconnected.

Claims

1. A charged particle beam device comprising: a particle source that outputs a charged particle beam; a stage that holds a sample; an optical system that adjusts the irradiation direction and focal position of the charged particle beam with respect to the sample; a detector that detects signals for generating an observation image of the sample; and a control unit that controls the optical system, the stage, and the detector, wherein the control unit obtains the observation image of the sample; calculates an evaluation value that evaluates the degree of shift in the focal position of the image for each of a plurality of regions of the observation image; and generates information on the three-dimensional shape of the sample based on the evaluation values ​​of the plurality of regions.

2. A charged particle beam device as described in claim 1, characterized in that the control unit calculates the inclination between a surface formed by a region of the sample and a reference surface based on information on the three-dimensional shape of the sample.

3. A charged particle beam device according to claim 2, characterized in that the control unit controls the stage so as to reduce the tilt based on the calculation result of the tilt.

4. A charged particle beam device as described in claim 2, wherein the control unit: acquires a plurality of the observation images by changing at least one of the focal position of the charged particle beam and the position of the sample on the stage; calculates the evaluation values ​​of the plurality of regions for each of the plurality of observation images; generates sample position information representing the position of the sample in the irradiation direction of the charged particle beam in each of the plurality of regions based on the evaluation values ​​of the plurality of regions in each of the plurality of observation images; estimates a three-dimensional shape of the sample based on the sample position information; and generates information on the three-dimensional shape of the sample based on the result of the estimation.

5. A charged particle beam device as described in claim 4, wherein the control unit: stores adjustment parameters of the optical system in association with the observation images; calculates an index representing the sharpness of the images of the multiple regions of one of the observation images as the evaluation value for each of the multiple observation images; identifies the value of the adjustment parameter at which the evaluation value is maximum or minimum by analyzing the relationship between the adjustment parameter and the evaluation values ​​of the multiple regions for the multiple observation images; and generates the sample position information based on the identified value of the adjustment parameter.

6. A charged particle beam device as described in claim 1, characterized in that the control unit generates information on the three-dimensional shape of the sample based on the degree of change in the evaluation values ​​of the multiple regions.

7. A charged particle beam device according to claim 6, characterized in that the control unit obtains the observation image using the optical system having astigmatism.

8. A charged particle beam device as described in claim 1, characterized in that the control unit controls the irradiation direction of the charged particle beam so as to be approximately perpendicular to a surface formed by a region of the sample, based on information on the three-dimensional shape of the sample.

9. A processing method executed by a charged particle beam device, the charged particle beam device having: a particle source that outputs a charged particle beam; a stage that holds a sample; an optical system that adjusts the irradiation direction and focal position of the charged particle beam with respect to the sample; a detector that detects a signal for generating an observation image of the sample; and a control unit that controls the optical system, the stage, and the detector, the processing method comprising: a first step in which the control unit obtains an observation image of the sample; a second step in which the control unit calculates an evaluation value that evaluates the degree of shift in the focal position of an image for each of a plurality of regions of the observation image; and a third step in which the control unit generates information on the three-dimensional shape of the sample based on the evaluation values ​​of the plurality of regions.

10. A processing method according to claim 9, comprising: a step in which the control unit calculates the inclination between a surface formed by a region of the sample and a reference surface based on information on the three-dimensional shape of the sample; and a step in which the control unit controls the stage so as to reduce the inclination.

11. A processing method as described in claim 10, wherein the first step includes a step in which the control unit acquires a plurality of the observation images by changing at least one of the focal position of the charged particle beam and the position of the sample on the stage; the second step includes a step in which the control unit calculates the evaluation values ​​of the plurality of regions for each of the plurality of observation images, and the control unit generates sample position information representing the position of the sample in the irradiation direction of the charged particle beam in each of the plurality of regions based on the evaluation values ​​of the plurality of regions in each of the plurality of observation images; and the third step includes a step in which the control unit estimates a three-dimensional shape of the sample based on the sample position information, and the control unit generates information on the three-dimensional shape of the sample based on the result of the estimation.

12. A processing method as described in claim 11, wherein the first step includes a step in which the control unit stores adjustment parameters of the optical system in correspondence with the observation images, and the second step includes a step in which the control unit calculates, for each of the plurality of observation images, an index representing the sharpness of the images of the plurality of regions of one of the observation images as the evaluation value, the control unit identifies the value of the adjustment parameter at which the evaluation value is maximum or minimum by analyzing the relationship between the adjustment parameter and the evaluation values ​​of the plurality of regions for the plurality of observation images, and the control unit generates the sample position information based on the identified value of the adjustment parameter.

13. A processing method as described in claim 9, characterized in that the third step includes a step in which the control unit generates information on the three-dimensional shape of the sample based on the degree of change in the evaluation values ​​of the multiple regions.

14. A processing method according to claim 13, characterized in that the first step includes a step in which the control unit obtains the observation image using the optical system having astigmatism.

15. A processing method as described in claim 9, characterized in that the control unit includes a step of controlling the irradiation direction of the charged particle beam so as to be approximately perpendicular to a surface formed by a region of the sample, based on information on the three-dimensional shape of the sample.