A method for dynamic focusing of a scanning electron microscope by ternary function fitting and related apparatus

Abstract

The application discloses a ternary function fitting dynamic focusing method of a scanning electron microscope and related equipment. The method comprises the following steps: acquiring a first imaging graph and a first focusing parameter, dividing the first imaging graph into a plurality of first subgraphs; acquiring a first target subgraph, acquiring a second focusing parameter according to the position of the first target subgraph and the first focusing parameter; scanning a sample at a position corresponding to the second focusing parameter according to the second focusing parameter, obtaining a plurality of third target subgraphs, and merging the first target subgraph and the third target subgraphs to obtain an output imaging graph. The ternary function fitting dynamic focusing method of the scanning electron microscope provided by the application can obtain a clearer output imaging graph more quickly and simply, and solves the problem of blurred image quality in the edge region of a scanning field when an electron beam scans the scanning field in the prior art.

Description

Technical Field

[0001] This invention relates to the field of electron microscopy scanning imaging technology, and in particular to a ternary function fitting dynamic focusing method and related equipment for scanning electron microscopes. Background Technology

[0002] In existing technologies, scanning electron microscopy (SEM) is a type of electron microscope. It uses an electron beam as the illumination source, focusing a very fine electron beam to illuminate the sample surface in a grating-like scanning manner. Information about the sample surface is obtained by detecting backscattered electrons, secondary electrons, and Auger electrons generated by the sample, which are then collected and processed to obtain a magnified grayscale image of the microscopic morphology. Focusing is a crucial operation in SEM imaging; the degree of focus adjustment determines the final image quality. The principle is to change the coil current of the objective lens (electromagnetic lens), altering the trajectory and direction of electrons through the electromagnetic lens region, thus converging the electron beam onto the sample surface. The parameters typically displayed are the working distance or the objective lens current value. In cases of large scanning fields or low magnification, the optimal scanning value for the central region may not be applicable to other areas of the scanning field, especially the edge regions. When the electron beam scans the scanning field, its ideal focal length changes accordingly at different positions, which can easily cause image blurring in the edge areas of the scanning field.

[0003] Therefore, existing technologies still need to be improved and enhanced. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, a ternary function fitting dynamic focusing method and related equipment for scanning electron microscopes are provided, aiming to solve the problem of blurred image quality in the edge region of the scanning field when the electron beam scans in the scanning field.

[0005] A first aspect of the present invention provides a ternary function fitting dynamic focusing method for scanning electron microscopes, comprising:

[0006] Obtain a first image and a first focusing parameter, wherein the first focusing parameter is the focusing parameter corresponding to the first image, and divide the first image into multiple first sub-images;

[0007] Obtain a first target sub-image, which is the sub-image with the highest clarity in the first sub-image. Obtain a second focus parameter based on the position of the first target sub-image and the first focus parameter. The second focus parameter is the focus parameter of the position corresponding to the second target sub-image. The second target sub-image is the sub-image in the first sub-image other than the first target sub-image.

[0008] The sample at the position corresponding to the second focusing parameter is scanned according to the second focusing parameter to obtain multiple third target sub-images. The first target sub-image and the third target sub-images are merged to obtain the output imaging image.

[0009] The aforementioned ternary function fitting dynamic focusing method for scanning electron microscopes, wherein acquiring the first image includes:

[0010] A range of focusing parameters is obtained. Within the range of focusing parameters, the target sample is scanned at a preset step interval to obtain multiple initial imaging images. The initial imaging image with the highest resolution is selected as the first imaging image.

[0011] The focusing parameters corresponding to the first imaging image are obtained as the first focusing parameters.

[0012] The aforementioned ternary function fitting dynamic focusing method for scanning electron microscopes, wherein dividing the first image into multiple first sub-images includes:

[0013] The scanning field is divided into multiple square sub-blocks of the same size, wherein the number of rows and columns of each square sub-block is odd.

[0014] Based on the position of the square sub-block, the first image is divided into multiple first sub-images.

[0015] The aforementioned ternary function fitting dynamic focusing method for scanning electron microscopes, wherein obtaining the second focusing parameters based on the position of the first target sub-image and the first focusing parameters includes:

[0016] The target distance and target angle are obtained based on the position of the first target sub-image, wherein the target distance is the distance between the center points of the first target sub-image and the second target sub-image, and the target angle is the angle between the line connecting the center points of the first target sub-image and the second target sub-image and the vertical direction;

[0017] The second focusing parameter is obtained based on the target distance, target angle, and the first focusing parameter.

[0018] The aforementioned ternary function fitting dynamic focusing method for scanning electron microscopes, wherein obtaining the second focusing parameter based on the target distance, target angle, and the first focusing parameter includes:

[0019] Obtain the target coefficients, and then obtain the target function based on the target coefficients;

[0020] The second focusing parameter is obtained according to the objective function;

[0021] The objective function is:

[0022] V = a0 * L2 +a1*θ 2 +a2*I 2 +a3*L*θ+a4*L*I+a5*θ*I+a6*

[0023] L+a7*θ+a8*I+a9;

[0024] Wherein, V is the second focusing parameter, I is the first focusing parameter, L is the target distance, θ is the target angle, and a0, a1, a2, a3, a4, a5, a6, a7, a8, and a9 are target coefficients.

[0025] The aforementioned ternary function fitting dynamic focusing method for scanning electron microscopes, wherein obtaining the target coefficients includes:

[0026] Obtain a target sub-image group, which is the set of sub-images with the highest resolution corresponding to the square sub-block when the scanning electron microscope scans the experimental sample;

[0027] Obtain the target parameter set, which is the set of focusing parameters corresponding to each position of the sub-map in the target sub-map set;

[0028] The target coefficients are obtained based on the target parameter set.

[0029] The described ternary function fitting dynamic focusing method for scanning electron microscopy, wherein the step of scanning the sample at the position corresponding to the second focusing parameter according to the second focusing parameter to obtain multiple third target sub-images includes:

[0030] The current of the focusing coil of the scanning electron microscope is changed according to the second focusing parameter to scan and image the sample at the position corresponding to the second focusing parameter, so as to obtain multiple third target sub-images.

[0031] A second aspect of the present invention provides a ternary function fitting dynamic focusing device for a scanning electron microscope, comprising:

[0032] An image segmentation module is used to obtain a first imaging image and a first focusing parameter, wherein the first focusing parameter is the focusing parameter corresponding to the first imaging image, and to divide the first imaging image into multiple first sub-images.

[0033] The parameter extraction module is used to obtain a first target sub-image, which is the sub-image with the highest clarity in the first sub-image. The second focus parameter is obtained based on the position of the first target sub-image and the first focus parameter. The second focus parameter is the focus parameter of the position corresponding to the second target sub-image. The second target sub-image is the sub-image in the first sub-image other than the first target sub-image.

[0034] The output module is used to scan the sample at the position corresponding to the second focusing parameter according to the second focusing parameter, obtain multiple third target sub-images, and merge the first target sub-image and the third target sub-images to obtain an output imaging image.

[0035] A third aspect of the present invention provides a terminal comprising: a processor and a storage medium communicatively connected to the processor, the storage medium being adapted to store a plurality of instructions, and the processor being adapted to invoke the instructions in the storage medium to execute the steps of implementing the ternary function fitting dynamic focusing method for scanning electron microscopes as described in any of the preceding claims.

[0036] In a fourth aspect, the present invention provides a storage medium storing one or more programs that can be executed by one or more processors to implement the steps of the ternary function fitting dynamic focusing method for scanning electron microscopes as described in any of the preceding claims.

[0037] Beneficial Effects: Compared with existing technologies, this invention provides a ternary function fitting dynamic focusing method and related equipment for scanning electron microscopes. In the ternary function fitting dynamic focusing method for scanning electron microscopes provided by this invention, a first imaging image and a first focusing parameter are obtained. The first focusing parameter is the focusing parameter corresponding to the first imaging image. The first imaging image is divided into multiple first sub-images. Then, a first target sub-image is obtained, which is the sub-image with the highest clarity among the first sub-images. A second focusing parameter is obtained based on the position of the first target sub-image and the first focusing parameter. The second focusing parameter is the focusing parameter at the position corresponding to the second target sub-image. The second target sub-image is the sub-image in the first sub-image excluding the first target sub-image. Finally, the sample at the position corresponding to the second focusing parameter is scanned according to the second focusing parameter to obtain multiple third target sub-images. The first target sub-images and the third target sub-images are merged to obtain the output imaging image. This method can separate the nonlinear system and linear components of the actual system, minimizing the influence of nonlinearity. This allows for a faster and simpler way to obtain a clearer output imaging image, solving the problem of blurred image quality in the edge region of the scanning field when the electron beam scans in the scanning field, as in existing technologies. Attached Figure Description

[0038] Figure 1 A flowchart illustrating an embodiment of the ternary function fitting dynamic focusing method for scanning electron microscopes provided by the present invention;

[0039] Figure 2 A scanning electron microscope (SEM) structural diagram illustrating an embodiment of the ternary function fitting dynamic focusing method for a scanning electron microscope provided by the present invention;

[0040] Figure 3A block diagram in an embodiment of the ternary function fitting dynamic focusing method for scanning electron microscope provided by the present invention;

[0041] Figure 4 A system schematic diagram in an embodiment of the ternary function fitting dynamic focusing method for scanning electron microscopes provided by the present invention;

[0042] Figure 5 A schematic diagram of an embodiment of the ternary function fitting dynamic focusing device for a scanning electron microscope provided by the present invention;

[0043] Figure 6 A schematic diagram of the structure of an embodiment of the terminal provided by the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0045] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0046] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0047] Example 1

[0048] The ternary function fitting dynamic focusing method for scanning electron microscopes provided in this embodiment can be executed by a terminal, which can be, but is not limited to, a smart electron microscope, a computer, etc. The following explanation uses a scanning electron microscope as an example. Figure 1As shown, the ternary function fitting dynamic focusing method for scanning electron microscopes provided in this embodiment includes the following steps:

[0049] In this embodiment, a ternary function fitting dynamic focusing method for scanning electron microscopes is provided. For example... Figure 1 As shown, the ternary function fitting dynamic focusing method for scanning electron microscopes provided by this invention includes the following steps:

[0050] S100: Obtain a first image and a first focusing parameter, wherein the first focusing parameter is the focusing parameter corresponding to the first image, and divide the first image into multiple first sub-images.

[0051] The acquisition of the first image includes:

[0052] S110. Obtain the focusing parameter range, and scan the target sample with the focusing parameters at preset step intervals within the focusing parameter range to obtain multiple initial imaging images. Obtain the initial imaging image with the highest clarity as the first imaging image.

[0053] S120. Obtain the focusing parameters corresponding to the first imaging image as the first focusing parameters.

[0054] Specifically, the sample to be tested is first placed in the sample chamber of the scanning electron microscope (SEM), and then the user can set the focusing parameter range of the objective lens. The SEM acquires the user-set parameters and performs scanning according to those parameters. Figure 2 As shown.

[0055] In this embodiment, the accelerating voltage of the scanning electron microscope is set to 30 kV, the beam current is set to between 1 pA and 200 nA, the magnification is set to 5K times, the working focal length (focusing parameter value) of the objective lens is set to between 10.00 mm and 10.60 mm, and the preset step size is 0.01 mm. In other embodiments, the preset step size can be set to a larger or smaller value according to the accuracy requirements.

[0056] Within the objective lens's focusing parameters (equivalent working distance), the focusing parameters of the scanning electron microscope are varied according to a preset step size. Each time the preset step size is changed, one image of the sample to be tested is acquired. The acquired image of the sample to be tested is the initial imaging image. It is easy to see that in this embodiment, there are 61 initial imaging images. Then, the image with the highest clarity among the initial imaging images is selected as the first imaging image.

[0057] Specifically, in this embodiment, a Fourier algorithm is used to evaluate the sharpness of the initial image, and the image with the highest sharpness evaluation score is determined as the optimal focused image. In this embodiment, the optimal focused image is the first image, and the focusing parameters corresponding to the optimal focused image, that is, the focusing value of its corresponding objective lens focal length, are obtained as the first focusing parameter. Therefore, the first focusing parameter is the optimal focusing value I.

[0058] After obtaining the first image and the first focusing parameters, the first image is divided into multiple first sub-images.

[0059] The step of dividing the first image into multiple first sub-images includes:

[0060] S130. Divide the scanning field into multiple square sub-blocks of the same size, wherein the number of rows and columns of the square sub-blocks are both odd.

[0061] S140. Based on the position of the square sub-block, the first image is divided into multiple first sub-images.

[0062] Specifically, the aspect ratio of the overall scanning field of a scanning electron microscope is generally 1:1. The scanning field is divided into several square sub-blocks according to its length and width proportions. When dividing the scanning field proportionally, it is necessary to ensure that each sub-block has a symmetrical counterpart about the center within the scanning field. Therefore, the length or width of the scanning field is divided into an odd number of equal parts. That is, in this embodiment, the scanning field is divided proportionally into several equally sized square sub-blocks, and the number of rows and columns of each square sub-block is odd, meaning the distribution of the square sub-blocks is symmetrical about the center. (Refer to...) Figure 3 In this embodiment, the scanning field is divided into 25 square sub-blocks, and then the first imaging image is divided into multiple first sub-images according to the position of the square sub-blocks. That is, the first imaging image is divided into 25 first sub-images.

[0063] S200. Obtain a first target sub-image, which is the sub-image with the highest clarity in the first sub-image. Obtain a second focus parameter based on the position of the first target sub-image and the first focus parameter. The second focus parameter is the focus parameter of the position corresponding to the second target sub-image. The second target sub-image is a sub-image in the first sub-image other than the first target sub-image.

[0064] Specifically, Fourier transform is used to evaluate the sharpness of each first sub-image to obtain the first target sub-image with the highest sharpness. The step of obtaining the second focusing parameters based on the position of the first target sub-image and the first focusing parameters includes:

[0065] S210. Obtain the target distance and target angle based on the position of the first target sub-image, wherein the target distance is the distance between the center points of the first target sub-image and the second target sub-image, and the target angle is the angle between the line connecting the center points of the first target sub-image and the second target sub-image and the vertical direction;

[0066] Specifically, the position of the first target sub-image is first obtained. Typically, the first target sub-image is the sub-image in the middle of the scanning field. Taking the center point of the first target sub-image as the center point, a polar coordinate system (L, θ) is established. Specifically, the distance from the center position of the second target sub-image to the center point of the first target sub-image, which is also the center position of the scanning field, is represented by the variable L. The angle between the line connecting the centers and the positive vertical direction is represented by θ (that is, the position of the sub-block is represented by polar coordinates with the center of the scanning field as the center). The correspondence between (L, θ) and V is obtained, and the functional relationship V = f(L, θ, I) is fitted, which is the focusing parameter equation of the second target sub-image.

[0067] Then, the coordinates (L, θ) of the center point of each second target sub-image in the scanning field are determined. Specifically, the second target sub-image is the sub-image of the first sub-image excluding the first target sub-image. Here, L is the target distance, and θ is the target angle.

[0068] S220. Obtain the second focusing parameter based on the target distance, target angle, and the first focusing parameter.

[0069] The step of obtaining the second focusing parameter based on the target distance, target angle, and the first focusing parameter includes:

[0070] S221. Obtain the target coefficients and obtain the target function based on the target coefficients.

[0071] The acquisition of the target coefficient includes:

[0072] Obtain a target sub-image group, which is the set of sub-images with the highest resolution corresponding to the square sub-block when the scanning electron microscope scans the experimental sample;

[0073] Obtain the target parameter set, which is the set of focusing parameters corresponding to each position of the sub-map in the target sub-map set;

[0074] The target coefficients are obtained based on the target parameter set.

[0075] Specifically, when determining the target coefficients of the fitting function, it is necessary to first obtain the target sub-image group, which is obtained by scanning the experimental sample using a scanning electron microscope (SEM) before obtaining the first image. Specifically, the SEM individually adjusts the focusing parameters on each square sub-block, scans, and evaluates image sharpness. When the sub-image corresponding to the square sub-block has the highest sharpness, that sub-image is acquired to obtain the target sub-image group. That is, the target sub-image group includes the sharpest image corresponding to each square sub-block. The focusing parameter value corresponding to the sub-image at each position in the target sub-image group is obtained as the optimal focusing value for the center position of that sub-block. The focusing parameter of the sub-image at the middle position of the target sub-image group is set as I′, and the focusing parameters of the sub-images excluding the middle position in the target sub-image group are set as variable V′. Extract the target distance L′ and target angle θ′ corresponding to the sub-images excluding the middle position in the target sub-image group, and fit a ternary function in a three-dimensional coordinate system. Since the result value is closer to the reference value I′ the closer the scanning point is to the center in this embodiment, a binomial function is selected for fitting.

[0076] V′=a0*L′ 2 +a1*θ′ 2 +a2*I′ 2 +a3*L′*θ′+a4*L′*I′+a5*θ′*

[0077] I′+a6*L′+a7*θ′+a8*I′+a9;

[0078] Specifically, a0, a1, a2, a3, a4, a5, a6, a7, a8, and a9 are the target coefficients. When determining the target coefficients of the fitted function, the function values ​​at the known coordinate points should be as close to the true values ​​as possible. Therefore, a squared error loss function needs to be constructed first. The loss calculation formula for each point is as follows:

[0079]

[0080] The target loss function is obtained by summing up the errors from all points. In the formula for calculating the loss function, each coefficient has a maximum order of 2. Taking the partial derivative with respect to each coefficient results in a maximum order of 1. Setting all partial derivatives to 0 allows us to find a unique optimal solution for the coefficients, ultimately yielding the values ​​of the target coefficients a0, a1, a2, a3, a4, a5, a6, a7, a8, and a9.

[0081] S222 obtains the second focusing parameter according to the objective function;

[0082] The objective function is:

[0083] V = a0 * L 2 +a1*θ 2 +a2*I 2 +a3*L*θ+a4*L*I+a5*θ*I+a6*

[0084] L+a7*θ+a8*I+a9;

[0085] Wherein, V is the second focusing parameter, I is the first focusing parameter, L is the target distance, θ is the target angle, and a0, a1, a2, a3, a4, a5, a6, a7, a8, and a9 are target coefficients.

[0086] Specifically, by substituting the obtained target coefficients into the target function, the value of the second focusing parameter V can be obtained based on the target distance L, the target angle θ, and the first focusing parameter I.

[0087] Refer again Figure 1 The three-variable function fitting dynamic focusing method for scanning electron microscopy further includes the following steps:

[0088] S300: Scan the sample at the position corresponding to the second focusing parameter according to the second focusing parameter to obtain multiple third target sub-images, and merge the first target sub-image and the third target sub-image to obtain the output imaging image.

[0089] The step of scanning the sample at the position corresponding to the second focusing parameter according to the second focusing parameter yields multiple third target sub-images, including:

[0090] The current of the focusing coil of the scanning electron microscope is changed according to the second focusing parameter to scan and image the sample at the position corresponding to the second focusing parameter, so as to obtain multiple third target sub-images.

[0091] Specifically, the second focusing parameter corresponding to each square sub-block in the scanning field, excluding the square sub-block corresponding to the first target sub-image, is calculated through the objective function. When the electron beam scans the corresponding square sub-block during scanning, the focusing coil current is changed accordingly based on the corresponding second focusing parameter to image the sample, thereby obtaining multiple third target sub-images. The first target sub-image and the third target sub-images are then merged to obtain the final output image.

[0092] Reference Figure 4 , Figure 4This is a schematic diagram of the ternary function fitting dynamic focusing method for scanning electron microscopes proposed in this embodiment. It can be seen that by using this method, after obtaining the target function through multiple initial focusing operations, subsequent focusing on other samples does not require repetitive operations. Only the focusing parameters corresponding to the image with the highest clarity in this scan need to be found using an image sharpness evaluation method. Based on the target function, the optimal focusing values ​​corresponding to the positions of each square sub-block in the scanning field can be obtained. Then, when the corresponding position is scanned, the objective lens current is adjusted accordingly, and sample imaging is performed. This method separates the nonlinear system and linear components of the actual system, minimizing the influence of nonlinearity. This allows for a faster and simpler way to obtain a clearer output image. Compared with existing image processing methods, this method simplifies the process of segmented image acquisition and processing large amounts of image data. Compared with neural network methods, it significantly saves computation time, reduces computational difficulty, and provides higher accuracy and stability of numerical results.

[0093] In summary, this embodiment provides a ternary function fitting dynamic focusing method for scanning electron microscopes. It involves acquiring a first imaging image and first focusing parameters (the focusing parameters corresponding to the first imaging image), dividing the first imaging image into multiple first sub-images, and then acquiring a first target sub-image (the sub-image with the highest clarity among the first sub-images). Based on the position of the first target sub-image and the first focusing parameters, a second focusing parameter is acquired (the focusing parameters at the position corresponding to the second target sub-image). The second target sub-image is any sub-image in the first sub-image except for the first target sub-image. Finally, the sample at the position corresponding to the second focusing parameter is scanned according to the second focusing parameter to obtain multiple third target sub-images. The first and third target sub-images are then merged to obtain the output imaging image. This method separates the nonlinear and linear components of the actual system, minimizing the impact of nonlinearity. This allows for a faster and simpler acquisition of a clearer output imaging image, solving the problem of blurred image quality in the scanning field edge region when the electron beam scans the scanning field in existing technologies.

[0094] It should be understood that although the steps in the flowcharts shown in the accompanying drawings are displayed sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of the steps in this invention, and these steps can be executed in other orders. Moreover, at least a portion of the steps in this invention may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0095] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM), etc.

[0096] Example 2

[0097] Based on the above embodiments, the present invention also provides a ternary function fitting dynamic focusing device for scanning electron microscopes, the functional module of which is shown in the figure below. Figure 5 As shown, the ternary function fitting dynamic focusing device of the scanning electron microscope includes:

[0098] An image segmentation module is used to obtain a first imaging image and a first focusing parameter, wherein the first focusing parameter is the focusing parameter corresponding to the first imaging image, and to divide the first imaging image into multiple first sub-images, as specifically described in Embodiment 1.

[0099] The parameter extraction module is used to obtain a first target sub-image, which is the sub-image with the highest clarity in the first sub-image. The second focus parameter is obtained according to the position of the first target sub-image and the first focus parameter. The second focus parameter is the focus parameter of the position corresponding to the second target sub-image. The second target sub-image is a sub-image in the first sub-image other than the first target sub-image, as specifically described in Embodiment 1.

[0100] The output module is used to scan the sample at the position corresponding to the second focusing parameter according to the second focusing parameter to obtain multiple third target sub-images, and merge the first target sub-image and the third target sub-image to obtain an output imaging image, as specifically described in Embodiment 1.

[0101] Example 3

[0102] Based on the ternary function fitting dynamic focusing method for scanning electron microscopes described in Embodiment 1 above, the present invention also provides a terminal, the principle block diagram of which is as follows: Figure 6 As shown. The terminal includes a memory 10 and a processor 20. The memory 10 stores a ternary function fitting dynamic focusing program for a scanning electron microscope. When the processor 10 executes the computer program, it can perform at least the following steps:

[0103] Obtain a first image and a first focusing parameter, wherein the first focusing parameter is the focusing parameter corresponding to the first image, and divide the first image into multiple first sub-images;

[0104] Obtain a first target sub-image, which is the sub-image with the highest clarity in the first sub-image. Obtain a second focus parameter based on the position of the first target sub-image and the first focus parameter. The second focus parameter is the focus parameter of the position corresponding to the second target sub-image. The second target sub-image is the sub-image in the first sub-image other than the first target sub-image.

[0105] The sample at the position corresponding to the second focusing parameter is scanned according to the second focusing parameter to obtain multiple third target sub-images. The first target sub-image and the third target sub-images are merged to obtain the output imaging image.

[0106] The acquisition of the first image includes:

[0107] A range of focusing parameters is obtained. Within the range of focusing parameters, the target sample is scanned at a preset step interval to obtain multiple initial imaging images. The initial imaging image with the highest resolution is selected as the first imaging image.

[0108] The focusing parameters corresponding to the first imaging image are obtained as the first focusing parameters.

[0109] The step of dividing the first image into multiple first sub-images includes:

[0110] The scanning field is divided into multiple square sub-blocks of the same size, wherein the number of rows and columns of each square sub-block is odd.

[0111] Based on the position of the square sub-block, the first image is divided into multiple first sub-images.

[0112] The step of obtaining the second focusing parameter based on the position of the first target sub-image and the first focusing parameter includes:

[0113] The target distance and target angle are obtained based on the position of the first target sub-image, wherein the target distance is the distance between the center points of the first target sub-image and the second target sub-image, and the target angle is the angle between the line connecting the center points of the first target sub-image and the second target sub-image and the vertical direction;

[0114] The second focusing parameter is obtained based on the target distance, target angle, and the first focusing parameter.

[0115] The step of obtaining the second focusing parameter based on the target distance, target angle, and the first focusing parameter includes:

[0116] Obtain the target coefficients, and then obtain the target function based on the target coefficients;

[0117] The second focusing parameter is obtained according to the objective function;

[0118] The objective function is:

[0119] V = a0 * L 2 +a1*θ 2 +a2*I 2 +a3*L*θ+a4*L*I+a5*θ*I+a6*L+a7*θ+a8*I+a9;

[0120] Wherein, V is the second focusing parameter, I is the first focusing parameter, L is the target distance, θ is the target angle, and a0, a1, a2, a3, a4, a5, a6, a7, a8, and a9 are target coefficients.

[0121] The acquisition of the target coefficient includes:

[0122] Obtain a target sub-image group, which is the set of sub-images with the highest resolution corresponding to the square sub-block when the scanning electron microscope scans the experimental sample;

[0123] Obtain the target parameter set, which is the set of focusing parameters corresponding to each position of the sub-map in the target sub-map set;

[0124] The target coefficients are obtained based on the target parameter set.

[0125] The step of scanning the sample at the position corresponding to the second focusing parameter according to the second focusing parameter to obtain multiple third target sub-images includes:

[0126] The current in the focusing coil of the scanning electron microscope is changed according to the second focusing parameter to scan and image the sample at the position corresponding to the second focusing parameter, so as to obtain multiple third target sub-images.

[0127] Example 4

[0128] The present invention also provides a storage medium storing one or more programs that can be executed by one or more processors to implement the steps of the ternary function fitting dynamic focusing method for scanning electron microscopes described in the above embodiments.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dynamic focusing method for fitting a ternary function in a scanning electron microscope, characterized in that, include: Obtain a first image and a first focusing parameter, wherein the first focusing parameter is the focusing parameter corresponding to the first image, and divide the first image into multiple first sub-images; Obtain a first target sub-image, which is the sub-image with the highest clarity in the first sub-image. Obtain a second focus parameter based on the position of the first target sub-image and the first focus parameter. The second focus parameter is the focus parameter of the position corresponding to the second target sub-image. The second target sub-image is the sub-image in the first sub-image other than the first target sub-image. The sample at the position corresponding to the second focusing parameter is scanned according to the second focusing parameter to obtain multiple third target sub-images. The first target sub-image and the third target sub-images are merged to obtain the output imaging image. The step of obtaining the second focusing parameter based on the position of the first target sub-image and the first focusing parameter includes: The target distance and target angle are obtained based on the position of the first target sub-image, wherein the target distance is the distance between the center points of the first target sub-image and the second target sub-image, and the target angle is the angle between the line connecting the center points of the first target sub-image and the second target sub-image and the vertical direction; The second focusing parameter is obtained based on the target distance, the target angle, and the first focusing parameter; The step of obtaining the second focusing parameter based on the target distance, target angle, and the first focusing parameter includes: Obtain the target coefficients, and then obtain the target function based on the target coefficients; The second focusing parameter is obtained according to the objective function; The objective function is: ； in, V The second focusing parameter is... I The first focusing parameter is... L The target distance is... For the target angle, 、 、 、 、 、 、 、 、 、 is the target coefficient.

2. The ternary function fitting dynamic focusing method for scanning electron microscopy according to claim 1, characterized in that, The acquisition of the first image includes: A range of focusing parameters is obtained. Within the range of focusing parameters, the target sample is scanned at a preset step interval to obtain multiple initial imaging images. The initial imaging image with the highest resolution is selected as the first imaging image. The focusing parameters corresponding to the first imaging image are obtained as the first focusing parameters.

3. The ternary function fitting dynamic focusing method for scanning electron microscopy according to claim 2, characterized in that, The step of dividing the first image into multiple first sub-images includes: The scanning field is divided into multiple square sub-blocks of the same size, wherein the number of rows and columns of each square sub-block is odd. Based on the position of the square sub-block, the first image is divided into multiple first sub-images.

4. The ternary function fitting dynamic focusing method for scanning electron microscopy according to claim 3, characterized in that, The acquisition of the target coefficient includes: Obtain a target sub-image group, which is the set of sub-images with the highest resolution corresponding to the square sub-block when the scanning electron microscope scans the experimental sample; Obtain the target parameter set, which is the set of focusing parameters corresponding to each position of the sub-map in the target sub-map set; The target coefficients are obtained based on the target parameter set.

5. The ternary function fitting dynamic focusing method for scanning electron microscopy according to claim 1, characterized in that, The step of scanning the sample at the position corresponding to the second focusing parameter according to the second focusing parameter yields multiple third target sub-images, including: The current of the focusing coil of the scanning electron microscope is changed according to the second focusing parameter to scan and image the sample at the position corresponding to the second focusing parameter, so as to obtain multiple third target sub-images.

6. A ternary function fitting dynamic focusing device for a scanning electron microscope, characterized in that, The device includes: An image segmentation module is used to obtain a first imaging image and a first focusing parameter, wherein the first focusing parameter is the focusing parameter corresponding to the first imaging image, and to divide the first imaging image into multiple first sub-images. The parameter extraction module is used to obtain a first target sub-image, which is the sub-image with the highest clarity in the first sub-image. The second focus parameter is obtained based on the position of the first target sub-image and the first focus parameter. The second focus parameter is the focus parameter of the position corresponding to the second target sub-image. The second target sub-image is the sub-image in the first sub-image other than the first target sub-image. The output module is used to scan the sample at the position corresponding to the second focusing parameter according to the second focusing parameter, obtain multiple third target sub-images, and merge the first target sub-image and the third target sub-images to obtain an output imaging image; The step of obtaining the second focusing parameter based on the position of the first target sub-image and the first focusing parameter includes: The target distance and target angle are obtained based on the position of the first target sub-image, wherein the target distance is the distance between the center points of the first target sub-image and the second target sub-image, and the target angle is the angle between the line connecting the center points of the first target sub-image and the second target sub-image and the vertical direction; The second focusing parameter is obtained based on the target distance, the target angle, and the first focusing parameter; The step of obtaining the second focusing parameter based on the target distance, target angle, and the first focusing parameter includes: Obtain the target coefficients, and then obtain the target function based on the target coefficients; The second focusing parameter is obtained according to the objective function; The objective function is: ； in, V The second focusing parameter is... I The first focusing parameter is... L The target distance is... For the target angle, 、 、 、 、 、 、 、 、 、 is the target coefficient.

7. A terminal, characterized in that, The terminal includes: a processor and a storage medium communicatively connected to the processor. The storage medium is adapted to store multiple instructions, and the processor is adapted to call the instructions in the storage medium to execute the steps of implementing the ternary function fitting dynamic focusing method for scanning electron microscopes according to any one of claims 1-5.

8. A storage medium, characterized in that, The storage medium stores one or more programs, which can be executed by one or more processors to implement the steps of the ternary function fitting dynamic focusing method for scanning electron microscopes as described in any one of claims 1-5.

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