A focus control method and device, scanning electron microscope and storage medium

Abstract

The embodiment of the present application provides a focus control method, comprising: dividing a region of interest into a plurality of image matrices of equal size in units of a preset number of image blocks; determining a focus origin of each image matrix and a focus parameter corresponding to the focus origin; applying the focus parameter corresponding to each focus origin to the image blocks other than the focus origin in the image matrix to which the focus origin belongs for image acquisition, and sequentially completing image acquisition of each image matrix. The embodiment of the present application also provides a device, a scanning electron microscope and a storage medium for implementing the method.

Description

Technical Field

[0001] This application relates to the field of scanning electron microscopy, and more particularly to a focusing control method, apparatus, scanning electron microscope, and storage medium. Background Technology

[0002] Currently, when users need to perform large-area microscopic imaging of samples, they typically need to use a scanning electron microscope (SEM) with automatic array scanning capabilities. When performing array scanning, the SEM usually decomposes the specified scanning area into several image blocks of equal area, then scans each of these image blocks one by one to obtain image data. Finally, software stitching or other methods are used to combine the image data into a panoramic image.

[0003] During the scanning of the image blocks one by one, due to factors such as the flatness of the sample under test, the focusing stability of the scanning electron microscope, and the influence of the external environment, the focal plane of different image blocks or the objective excitation of the scanning electron microscope needs to be adjusted according to the image feature sharpness. The existing solution for scanning electron microscopes is: fixed step autofocus, that is, after automatically focusing at a set position, the image is acquired, and then the same focusing parameters (objective current value and astigmatism value) are applied for a fixed number of subsequent steps to acquire images, and so on, scanning line by line. However, this solution has a long overall focusing time, resulting in a low overall imaging throughput. Summary of the Invention

[0004] In view of this, embodiments of this application aim to provide a focusing control method, apparatus, scanning electron microscope, and storage medium that can improve the overall imaging throughput and increase image acquisition efficiency during array scanning.

[0005] The technical solution of this application embodiment is implemented as follows:

[0006] This application provides a focusing control method, the method comprising:

[0007] The region of interest is divided into several image matrices of equal size, using a preset number of image blocks as units;

[0008] Determine the focal origin of each image matrix and the focal parameters corresponding to the focal origin;

[0009] The focusing parameters corresponding to each focusing origin are sequentially applied to the image blocks in the image matrix to which the focusing origin belongs, excluding the focusing origin, to acquire images, and the image acquisition of each image matrix is ​​completed in sequence.

[0010] In one embodiment, before dividing the region of interest into several image matrices of equal size, the method further includes:

[0011] The region of interest is decomposed into several image blocks of equal size.

[0012] In this embodiment of the application, the number of rows and columns of the image matrix may be the same or different; the number of rows and columns of the image matrix is ​​not less than 2.

[0013] In this embodiment of the application, determining the focal origin of each image matrix includes:

[0014] Determine the image block located at the center position in each of the image matrices;

[0015] The image block at the center position is determined as the focal origin of the image matrix.

[0016] In this embodiment of the application, determining the focusing parameters corresponding to the focusing origin includes:

[0017] Automatic focusing is performed on the determined focal origin to obtain the corresponding focusing parameters.

[0018] In one embodiment, the method for determining the focusing parameters corresponding to the focusing origin further includes:

[0019] The image corresponding to the focal origin is acquired.

[0020] This application also provides a focusing control device, which is applied to a scanning electron microscope and includes:

[0021] A partitioning unit is used to divide the region of interest into several image matrices of equal size, using a preset number of image blocks as units;

[0022] A determining unit is used to determine the focal origin of each of the image matrices and the focal parameters corresponding to the focal origin;

[0023] The image acquisition unit is used to sequentially apply the focusing parameters corresponding to each focusing origin to the image blocks other than the focusing origin in the image matrix to which the focusing origin belongs, and to complete the image acquisition of each image matrix in sequence.

[0024] This application also provides a scanning electron microscope, including:

[0025] The first processor is configured to divide the region of interest into several image matrices of equal size using a preset number of image blocks as units; and to determine the focal origin of each image matrix and the focal parameters corresponding to the focal origin.

[0026] An image processor is used to sequentially apply the focusing parameters corresponding to each focusing origin to the image blocks in the image matrix to which the focusing origin belongs, excluding the focusing origin, to acquire images, thereby completing the image acquisition of each image matrix in sequence.

[0027] This application also provides a scanning electron microscope, including: a first processor and a first memory for storing a computer program capable of running on the processor.

[0028] Wherein, when the first processor is used to run the computer program, it executes the steps of the above method.

[0029] This application also provides a storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described method.

[0030] The focusing control method, apparatus, scanning electron microscope, and storage medium provided in this application divide the region of interest into several image matrices of equal size, using a preset number of image blocks as units; determine the focusing origin and the focusing parameters corresponding to the focusing origin for each image matrix; and sequentially apply the focusing parameters corresponding to each focusing origin to the image blocks in the image matrix to which the focusing origin belongs, excluding the focusing origin itself, to acquire images, thereby completing the image acquisition for each image matrix in sequence. Compared with the previous line-by-line scanning acquisition method, the method of dividing the image matrix and determining the focusing origin in this application can greatly reduce the number of scanning focusing points, and the determination of the focusing origin position can avoid the problem of focusing on sample edges without image features, thereby improving the overall imaging throughput and image acquisition efficiency. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the focusing control method described in the embodiments of this application;

[0032] Figure 2 This is a schematic diagram of the focusing control method described in the application example of this application;

[0033] Figure 3 This is a schematic diagram of the image block division structure described in the application example of this application;

[0034] Figure 4 This is a schematic diagram of the image matrix partitioning structure described in the application example of this application;

[0035] Figure 5 This is a schematic diagram of the focal origin structure determined in the application example of this application;

[0036] Figure 6 This is a schematic diagram of a single image matrix scanning as described in the application example of this application;

[0037] Figure 7 This is a schematic diagram of the entire region of interest scan as described in the application example of this application;

[0038] Figure 8 This is a schematic diagram of a traditional fixed-step autofocus system.

[0039] Figure 9 This is a schematic diagram of the focusing control device described in an embodiment of this application;

[0040] Figure 10 This is a schematic diagram of the scanning electron microscope structure described in the embodiments of this application. Detailed Implementation

[0041] The present application will now be described in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. The present application will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] Example 1

[0043] This application provides a focusing control method, such as... Figure 1 As shown, the method includes:

[0044] Step 101: Divide the region of interest into several image matrices of equal size, using a preset number of image blocks as units;

[0045] Step 102: Determine the focal origin of each image matrix and the focal parameters corresponding to the focal origin;

[0046] Step 103: Apply the focusing parameters corresponding to each focusing origin to the image blocks in the image matrix to which the focusing origin belongs, excluding the focusing origin, and perform image acquisition in sequence to complete the image acquisition of each image matrix.

[0047] In practical applications, the embodiments of this application can select a region of interest (ROI) on the sample based on the sample analysis requirements. This region can also be called a large area, which is the area that needs to be photographed and observed as a whole.

[0048] In this embodiment of the application, before dividing the region of interest into several image matrices of equal size, the method further includes:

[0049] The region of interest is decomposed into several image blocks of equal size.

[0050] In practical applications, during the scanning and imaging process, an image is acquired for each image block.

[0051] In this embodiment of the application, the number of rows and columns of the image matrix may be the same or different; the number of rows and columns of the image matrix is ​​not less than 2.

[0052] In this embodiment, the number of image blocks in the image matrix can be set according to the actual sample analysis requirements. Typically, the number of image blocks in the image matrix is ​​not less than 4 (to ensure that the final number of focal origins is small, less than the number of focal origins in traditional focusing methods). That is, if the number of rows and columns in the image matrix are the same, then the image matrix is ​​a 2*2 matrix. Of course, the number of rows and columns can also be larger, such as 3*3 or 5*5, or the number of rows and columns can be different, such as 3*5, etc.

[0053] In this embodiment of the application, determining the focal origin of each image matrix includes:

[0054] Determine the image block located at the center position in each of the image matrices;

[0055] The image block at the center position is determined as the focal origin of the image matrix.

[0056] Here, if the image matrix is ​​3*3, then the image block in the second row and second column can be determined as the focal origin of the image matrix; for example, if the image matrix is ​​3*5, then the image block in the second row and third column can be determined as the focal origin of the image matrix.

[0057] In this embodiment of the application, determining the focusing parameters corresponding to the focusing origin includes:

[0058] Automatic focusing is performed on the determined focal origin to obtain the corresponding focusing parameters.

[0059] In this embodiment of the application, the method for determining the focusing parameters corresponding to the focusing origin further includes:

[0060] Acquire the image corresponding to the focal origin.

[0061] In one embodiment of this application, images of each image matrix can be acquired sequentially from left to right and from top to bottom (or other scanning orders). For a single image matrix, firstly, automatic focusing is performed on a determined focal origin to obtain focusing parameters, and the image corresponding to that focal origin is acquired; then, based on the focusing parameters corresponding to the focal origin, images of other image blocks in the image matrix are acquired in a left-to-right and top-to-bottom order (or other scanning orders).

[0062] The method described in this application is illustrated below with an application example, such as... Figure 2 As shown, it includes:

[0063] Step 1: Decompose the region of interest into several image blocks of equal size;

[0064] like Figure 3 As shown, taking the irregular polygon in the figure as the observation target (region of interest) as an example, the region is divided into 81 image blocks of 9*9.

[0065] Step 2: Combine the decomposed image blocks sequentially into a 3x3 image matrix;

[0066] like Figure 4 As shown, the 81 image blocks of the 9*9 grid are divided into 9 image matrices according to the 3*3 grid.

[0067] Step 3: Use the center image block of each image matrix as the focal origin;

[0068] like Figure 5 As shown, the central image block of each 3*3 image matrix is ​​used as the focal origin.

[0069] Step 4: Begin array scanning;

[0070] Step 5: Starting from the image matrix in the upper left corner, automatically focus on the focus origin, obtain the focus parameters, and acquire the image corresponding to the focus origin;

[0071] Step 6: Apply the focusing parameters of the focusing origin to the remaining image blocks of the image matrix, and perform image acquisition sequentially;

[0072] like Figure 6 As shown, the focusing parameters are applied to the remaining image blocks in the image matrix in a top-to-bottom, left-to-right order to acquire images.

[0073] Step 7: After the current matrix acquisition is completed, proceed to the next image matrix for image acquisition;

[0074] Here, for each image matrix, the focus origin is automatically focused first, and then images of other image blocks are acquired based on the focus parameters of the focus origin in a preset order.

[0075] Step 8: Repeat steps 5 to 7 until all image matrices have been acquired, such as... Figure 7 As shown.

[0076] The following scenario illustrates the effect of this application compared to traditional focusing scanning methods. Here, traditional scanning methods refer to fixed-step autofocus. Taking a fixed step size of 5 as an example, ... Figure 8As shown, the first image block of the region of interest is automatically focused for image acquisition. The same focusing parameters are applied to the subsequent five images, and automatic focusing is performed again on the sixth image, scanning line by line until the entire region is acquired. Taking a 6x6 region as an example, the number of focus points is 6. Applying the method of this embodiment, dividing the region into a 3x3 matrix, the final number of focus points can be 4. See Table 1 for details, using the acquisition of a semiconductor sample as an example.

[0077]

[0078]

[0079] Table 1

[0080] Note: Number of focus points (traditional focus) = Number of images acquired / (focus step size + 1);

[0081] Number of focus points (block focus) = Number of images captured / (Number of rows in the matrix * Number of columns in the matrix);

[0082] Total imaging time = number of focal points * focusing time + number of images * (time for each image + time for each motion image);

[0083] Acquisition throughput = Acquisition area / Total imaging time;

[0084] Total imaging time improvement rate = (Total imaging time of conventional focusing - Total imaging time of block scanning focusing) / Total imaging time of conventional focusing.

[0085] As can be seen from Table 1, the focusing method of this application embodiment achieves the goal of increasing throughput by significantly reducing the number of focal points. Compared with traditional focusing methods, its total imaging time is increased by 45%, and the acquisition throughput is nearly doubled.

[0086] Furthermore, compared to the traditional method of acquiring images by pre-focusing a portion of a specified scanning area (which involves pre-focusing on a portion of the area, calculating the focus value, and finally obtaining the focus parameters for each image block; since the sample surface is uneven, and the pre-focus parameters are calculated using a fitted function, the focus parameters are prone to calculation errors in areas with significant undulations, leading to defocusing and affecting overall image clarity), this embodiment can adjust the size of the acquisition block according to the sample properties and focus on the sample surface in real time. This avoids defocusing caused by factors such as sample flatness and conductivity, thus ensuring image clarity.

[0087] Example 2

[0088] To implement the method of the embodiments of this application, the embodiments of this application also provide a focusing control device, such as... Figure 9As shown, the device is used in a scanning electron microscope and includes:

[0089] The partitioning unit 901 is used to divide the region of interest into several image matrices of equal size, using a preset number of image blocks as units;

[0090] The determining unit 902 is used to determine the focal origin of each of the image matrices and the focal parameters corresponding to the focal origin;

[0091] The image acquisition unit 903 is used to sequentially apply the focusing parameters corresponding to each focusing origin to the image blocks in the image matrix to which the focusing origin belongs, excluding the focusing origin, to acquire images, thereby completing the image acquisition of each image matrix in sequence.

[0092] In this embodiment of the application, before the partitioning unit 901 divides the region of interest into several image matrices of equal size, it is further used for

[0093] The region of interest is decomposed into several image blocks of equal size.

[0094] In this embodiment of the application, the number of rows and columns of the image matrix may be the same or different; the number of rows and columns of the image matrix is ​​not less than 2.

[0095] In this embodiment of the application, the determining unit 902 determines the focal origin of each image matrix, including:

[0096] Determine the image block located at the center position in each of the image matrices;

[0097] The image block at the center position is determined as the focal origin of the image matrix.

[0098] In this embodiment of the application, the determining unit 902 determines the focusing parameters corresponding to the focusing origin, including:

[0099] Automatic focusing is performed on the determined focal origin to obtain the corresponding focusing parameters.

[0100] In this embodiment of the application, when the determining unit 902 determines the focusing parameters corresponding to the focusing origin, it is also used for

[0101] Acquire the image corresponding to the focal origin.

[0102] In practical applications, the division unit 901 and the determination unit 902 can be implemented by the processor in the focusing control device; the image acquisition unit 903 can be implemented by the imaging device in the focusing control device.

[0103] It should be noted that the focusing control device provided in the above embodiments is only illustrated by the division of the above program modules. In actual applications, the above processing can be assigned to different program modules as needed, that is, the internal structure of the device can be divided into different program modules to complete all or part of the processing described above. In addition, the device and method embodiments provided in the above embodiments belong to the same concept, and their specific implementation process can be found in the method embodiments, which will not be repeated here.

[0104] Example 3

[0105] To implement the method of the embodiments of this application, a hardware implementation based on the above-described program modules is provided. Furthermore, to implement the method of the embodiments of this application, a scanning electron microscope is also provided, such as... Figure 10 As shown, the scanning electron microscope 1000 includes:

[0106] The image processor 1001 is capable of acquiring and / or processing sample images.

[0107] The first processor 1002 is connected to the image processor 1001 to enable information interaction with the image processor and / or other modules in the scanning electron microscope, and to execute the methods provided by one or more technical solutions of the scanning electron microscope when running a computer program;

[0108] The computer program is stored in the first memory 1003.

[0109] Specifically, the first processor 1002 is used to divide the region of interest into several image matrices of equal size in units of a preset number of image blocks; and to determine the focal origin of each image matrix and the focal parameters corresponding to the focal origin;

[0110] The image processor 1001 is used to sequentially apply the focusing parameters corresponding to each focusing origin to the image blocks in the image matrix to which the focusing origin belongs, excluding the focusing origin, to acquire images, thereby completing the image acquisition of each image matrix in sequence.

[0111] In this embodiment of the application, before the first processor 1002 divides the region of interest into several image matrices of equal size, it is further used to...

[0112] The region of interest is decomposed into several image blocks of equal size.

[0113] In this embodiment of the application, the number of rows and columns of the image matrix may be the same or different; the number of rows and columns of the image matrix is ​​not less than 2.

[0114] In this embodiment of the application, the first processor 1002 determines the focal origin of each of the image matrices, including:

[0115] Determine the image block located at the center position in each of the image matrices;

[0116] The image block at the center position is determined as the focal origin of the image matrix.

[0117] In this embodiment of the application, the first processor 1002 determines the focusing parameters corresponding to the focusing origin, including:

[0118] Automatic focusing is performed on the determined focal origin to obtain the corresponding focusing parameters.

[0119] In this embodiment of the application, when the first processor 1002 determines the focusing parameters corresponding to the focusing origin, it is also used for

[0120] Acquire the image corresponding to the focal origin.

[0121] It should be noted that the specific processing procedures of the image processor 1001 and the first processor 1002 can be understood with reference to the above method, and will not be repeated here.

[0122] Of course, in practical applications, the various components in the scanning electron microscope 1000 are coupled together via a bus system 1004. It can be understood that the bus system 1004 is used to achieve communication between these components. In addition to a data bus, the bus system 1004 also includes a power bus, a control bus, and a status signal bus. However, for clarity, in... Figure 10 The general labeled all buses as Bus System 1004.

[0123] The first memory 1003 in this embodiment is used to store various types of data to support the operation of the scanning electron microscope 1000. Examples of such data include any computer program used to operate on the scanning electron microscope 1000.

[0124] The methods disclosed in the embodiments of this application can be applied to the first processor 1002, or implemented by the first processor 1002. The first processor 1002 may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by the integrated logic circuit of the hardware or by instructions in the form of software in the first processor 1002. The first processor 1002 may be a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The first processor 1002 can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor or any conventional processor, etc. The steps of the methods disclosed in the embodiments of this application can be directly manifested as being executed by a hardware decoding processor, or being executed by a combination of hardware and software modules in the decoding processor. The software modules may be located in a storage medium, which is located in the first memory 1003. The first processor 1002 reads the information in the first memory 1003 and completes the steps of the aforementioned method in combination with its hardware.

[0125] In an exemplary embodiment, the scanning electron microscope 1000 may be implemented by one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), general-purpose processors, controllers, microcontrollers (MCUs), microprocessors, or other electronic components to perform the aforementioned method.

[0126] In an exemplary embodiment, this application also provides a storage medium, namely a computer storage medium, specifically a computer-readable storage medium, such as a first memory 1003 storing a computer program. This computer program can be executed by the first processor 1002 of the scanning electron microscope 1000 to complete the steps described in the aforementioned scanning electron microscope method. The computer-readable storage medium can be a memory such as FRAM, ROM, PROM, EPROM, EEPROM, Flash Memory, magnetic surface memory, optical disc, or CD-ROM.

[0127] It should be noted that terms such as "first" and "second" are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0128] Furthermore, the technical solutions described in the embodiments of this application can be combined arbitrarily without conflict.

[0129] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application.

Claims

1. A focusing control method, characterized in that, The method includes: The region of interest is divided into several image matrices of equal size, using a preset number of image blocks as units; Identify the image block located at the center position in each of the image matrices, determine the image block at the center position as the focal origin of the image matrix, and determine the focal parameters corresponding to the focal origin; The focusing parameters corresponding to each focusing origin are sequentially applied to the image blocks other than the focusing origin in the image matrix to which the focusing origin belongs for image acquisition. The image acquisition of each image matrix is ​​completed in sequence. For each image matrix, the images of other image blocks in the image matrix other than the focusing origin are acquired according to the focusing parameters in a preset order. The preset order includes from left to right and from top to bottom.

2. The method according to claim 1, characterized in that, Before dividing the region of interest into several image matrices of equal size, the method further includes: The region of interest is decomposed into several image blocks of equal size.

3. The method according to claim 1, characterized in that, The number of rows and columns of the image matrix may be the same or different; the number of rows and columns of the image matrix is ​​not less than 2.

4. The method according to claim 1, characterized in that, Determining the focusing parameters corresponding to the focusing origin includes: Automatic focusing is performed on the determined focal origin to obtain the corresponding focusing parameters.

5. The method according to claim 4, characterized in that, The method for determining the focusing parameters corresponding to the focusing origin further includes: The image corresponding to the focal origin is acquired.

6. A focusing control device, characterized in that, The device is used in a scanning electron microscope and includes: A partitioning unit is used to divide the region of interest into several image matrices of equal size, using a preset number of image blocks as units; A determining unit is used to determine the image block located at the center position in each of the image matrices, determine the image block at the center position as the focal origin of the image matrix, and determine the focal parameters corresponding to the focal origin; An image acquisition unit is used to sequentially apply the focusing parameters corresponding to each focusing origin to the image blocks other than the focusing origin in the image matrix to which the focusing origin belongs, and to acquire images of each image matrix in sequence. For each image matrix, images of other image blocks in the image matrix other than the focusing origin are acquired according to a preset order based on the focusing parameters. The preset order includes from left to right and from top to bottom.

7. A scanning electron microscope, characterized in that, include: The first processor is used to divide the region of interest into several image matrices of equal size, using a preset number of image blocks as units; Identify the image block located at the center position in each of the image matrices, determine the image block at the center position as the focal origin of the image matrix, and determine the focal parameters corresponding to the focal origin; An image processor is used to sequentially apply the focusing parameters corresponding to each focusing origin to image blocks other than the focusing origin in the image matrix to which the focusing origin belongs for image acquisition, and sequentially complete the image acquisition of each image matrix. For each image matrix, images of other image blocks in the image matrix other than the focusing origin are acquired according to a preset order based on the focusing parameters. The preset order includes from left to right and from top to bottom.

8. A scanning electron microscope, characterized in that, include: A first processor and a first memory for storing computer programs capable of running on the processor. Wherein, when the first processor is used to run the computer program, it performs the steps of the method according to any one of claims 1 to 5.

9. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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