An image acquisition method, device, scanning electron microscope and storage medium

Abstract

This application provides an image acquisition method, comprising: acquiring the objective current value and the Z-axis parameter of the sample stage corresponding to a clear image at a first reference position in the region of interest; determining the Z-axis parameters of the sample stage corresponding to clear images at several second reference positions based on the Z-axis parameters of the sample stage, while keeping the objective current value constant; determining the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to clear images at different reference positions; determining the stake information for Z-axis interpolation during image acquisition based on the height difference and the depth of field of a scanning electron microscope; and acquiring the image of the region of interest based on the stake information and the objective current value. This application also provides an apparatus, 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 an image acquisition method, apparatus, scanning electron microscope, and storage medium. Background Technology

[0002] With the rapid development of science and technology, scanning electron microscopes (SEMs) are being used more and more widely. To gain a more comprehensive understanding of sample information, SEMs are increasingly being applied to image acquisition over large areas. When performing array scanning on a sample, factors such as sample flatness and coil hysteresis can cause some areas to require refocusing. Currently, the mainstream focusing method involves adjusting the electromagnetic lenses of the scanning particle beam microscope to determine a suitable focusing current value.

[0003] However, the above method requires repeated adjustments to determine the appropriate focusing current value, and the accuracy of the working distance of the scanning electron microscope can only be judged by the clarity of the image focus, which consumes a long focusing time. In addition, for samples with poor conductivity, the long focusing time can easily damage the sample, especially for samples with poor conductivity, which are prone to charge accumulation and affect image quality. Summary of the Invention

[0004] In view of this, embodiments of this application aim to provide an image acquisition method, apparatus, scanning electron microscope, and storage medium that can improve the image acquisition throughput during array scanning, thereby reducing damage to the sample.

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

[0006] This application provides an image acquisition method, the method comprising:

[0007] Obtain the objective current value and the Z-axis parameters of the sample stage when the image at the first reference position in the region of interest is clear;

[0008] With the objective current value remaining constant, the Z-axis parameters of the sample stage are determined based on the Z-axis parameters of the sample stage when the images are clear at several second reference positions.

[0009] The height difference of the sample in the preset direction is determined based on the Z-axis parameters of the sample stage when the image is clear at different reference positions.

[0010] Based on the height difference and the depth of field of the scanning electron microscope, the stake point information of Z-axis interpolation during image acquisition is determined;

[0011] Image acquisition of the region of interest is performed based on the pile point information and the objective lens current value.

[0012] The step of acquiring the objective current value and the Z-axis parameters of the sample stage when the image at the first reference position in the region of interest is clear includes:

[0013] Control the electron beam to move to the first reference position;

[0014] Adjust the objective current value of the scanning electron microscope until a clear image is obtained;

[0015] Record the Z-axis parameters of the sample stage when the image is clear.

[0016] The step of determining the Z-axis parameters of the sample stage corresponding to clear images at several second reference positions based on the Z-axis parameters of the sample stage includes:

[0017] For each second reference position, the total travel distance of the sample stage and the step size of each movement during the autofocusing process are configured based on the sample surface features.

[0018] Image acquisition is performed after each step the sample stage moves, until the total travel distance is completed;

[0019] Select the image with the best quality from all the acquired images, and record the Z-axis parameters of the sample stage when acquiring the image with the best quality.

[0020] The step of determining the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to when the image is clear at different reference positions includes:

[0021] On the two-dimensional plane where the sample is located, obtain the Z-axis parameters of the sample stage corresponding to the reference positions located at the two sides of the sample in a preset direction when the image is clear;

[0022] Calculate the difference between the two Z-axis parameters;

[0023] The difference is determined to be the height difference of the sample in the preset direction.

[0024] The stake point information for Z-axis interpolation during image acquisition, based on the height difference and the depth of field of the scanning electron microscope, includes:

[0025] The number of stake points for Z-axis interpolation in the preset direction is determined based on the height difference of the sample in the preset direction and the depth of field of the scanning electron microscope.

[0026] The total number of Z-axis interpolation points and the Z-axis parameters corresponding to each point are determined based on the number of Z-axis interpolation points in different preset directions during the acquisition of the region of interest image.

[0027] The step of acquiring the image of the region of interest based on the pile point information and the objective lens current value includes:

[0028] Based on image acquisition requirements, the region of interest is divided into several image blocks of equal size; wherein, a sub-region composed of a predetermined number of adjacent image blocks contains one of the stake points; the number of image blocks is greater than the total number of stake points;

[0029] Image acquisition of the region of interest is performed based on the objective lens current value and the Z-axis parameters of the pile points contained in each sub-region.

[0030] This application also provides an image acquisition device, which is applied to a scanning electron microscope and includes:

[0031] The processing unit is configured to acquire the objective current value and the Z-axis parameter of the sample stage corresponding to a clear image at a first reference position in the region of interest; while keeping the objective current value constant, determine the Z-axis parameters of the sample stage corresponding to a number of clear images at second reference positions based on the Z-axis parameters of the sample stage; determine the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to clear images at different reference positions; and determine the stake point information of Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope.

[0032] An image acquisition unit is used to acquire images of the region of interest based on the stake point information and the objective lens current value.

[0033] This application also provides a scanning electron microscope, including:

[0034] A first processor is configured to acquire the objective current value and the Z-axis parameter of the sample stage corresponding to a clear image at a first reference position in the region of interest; while keeping the objective current value constant, determine the Z-axis parameters of the sample stage corresponding to a number of clear images at second reference positions based on the Z-axis parameters of the sample stage; determine the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to clear images at different reference positions; and determine the stake information of Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope.

[0035] An image processor is used to acquire images of the region of interest based on the stake point information and the objective lens current value.

[0036] 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.

[0037] Wherein, when the first processor is used to run the computer program, it executes the steps of the above method.

[0038] 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.

[0039] The image acquisition method, apparatus, scanning electron microscope, and storage medium provided in this application acquire the objective current value and Z-axis parameters of the sample stage corresponding to a clear image at a first reference position in the region of interest. While keeping the objective current value constant, the Z-axis parameters of the sample stage corresponding to clear images at several second reference positions are determined based on the Z-axis parameters of the sample stage. The height difference of the sample in a preset direction is determined based on the Z-axis parameters of the sample stage corresponding to clear images at different reference positions. Based on the height difference and the depth of field of the scanning electron microscope, stake information for Z-axis interpolation during image acquisition is determined. Image acquisition of the region of interest is performed based on the stake information and the objective current value. This application embodiment determines the Z-axis parameters for subsequent array scanning by interpolation after acquiring the corresponding Z-axis parameters at the reference positions. Subsequently, image acquisition is performed based on the determined Z-axis parameters while keeping the objective current value constant, eliminating the need for focusing time, increasing overall imaging throughput, and improving image acquisition efficiency. Furthermore, for samples with poor conductivity, this application embodiment eliminates the need for prolonged focusing, reducing or avoiding damage to the sample. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the image acquisition method described in the embodiments of this application;

[0041] Figure 2 This is a schematic diagram of Z-axis parameter adjustment in the scanning electron microscope described in the embodiments of this application;

[0042] Figure 3 This is a schematic diagram of the sample reference position as described in the embodiments of this application;

[0043] Figure 4 This is a schematic diagram of the sample reference position and pile point position as described in the application example of this application;

[0044] Figure 5 This is a schematic diagram of the image acquisition device described in the embodiments of this application;

[0045] Figure 6 This is a schematic diagram of the scanning electron microscope structure described in the embodiments of this application. Figure 1 ;

[0046] Figure 7 This is a schematic diagram of the scanning electron microscope structure described in the embodiments of this application. Figure 2 . Detailed Implementation

[0047] 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.

[0048] Example 1

[0049] This application provides an image acquisition method, such as... Figure 1 As shown, the method includes:

[0050] Step 101: Obtain the objective current value and the Z-axis parameters of the sample stage when the image at the first reference position in the region of interest is clear;

[0051] Step 102: With the objective lens current value remaining unchanged, determine the Z-axis parameters of the sample stage corresponding to the clear images at several second reference positions based on the Z-axis parameters of the sample stage.

[0052] Step 103: Determine the height difference of the sample in the preset direction based on the Z-axis parameters of the sample stage when the image is clear at different reference positions;

[0053] Step 104: Determine the stake point information for Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope;

[0054] Step 105: Based on the pile information and the objective lens current value, perform image acquisition of the region of interest.

[0055] 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.

[0056] In this embodiment of the application, obtaining the objective current value and the Z-axis parameters of the sample stage corresponding to a clear image at the first reference position in the region of interest includes:

[0057] Control the electron beam to move to the first reference position;

[0058] Adjust the objective current value of the scanning electron microscope until a clear image is obtained;

[0059] Record the Z-axis parameters of the sample stage when the image is clear.

[0060] In this embodiment of the application, the first reference position can be any position on the sample surface. The setting of the first reference position is mainly used to determine the subsequent objective lens current value so that the Z-axis parameters can be obtained when the objective lens current value is constant.

[0061] In this embodiment of the application, determining the Z-axis parameters of the sample stage corresponding to clear images at several second reference positions based on the Z-axis parameters of the sample stage includes:

[0062] For each second reference position, the total travel distance of the sample stage and the step size of each movement during the autofocusing process are configured based on the sample surface features.

[0063] Image acquisition is performed after each step the sample stage moves, until the total travel distance is completed;

[0064] Select the image with the best quality from all the acquired images, and record the Z-axis parameters of the sample stage when acquiring the image with the best quality.

[0065] Here, the total travel distance and the step size for each movement can be set based on experience, and image acquisition is performed after each step. For samples with large surface features, the step size can be set longer; conversely, for samples with small surface features, the step size can be set shorter to acquire more images and Z-axis parameters, resulting in more accurate data acquisition. Taking a total travel distance of ±15µm and a step size of 2µm as an example, images are acquired after each movement of the sample stage along the Z-axis, i.e., image acquisition is performed at positions such as ±2µm, ±4µm, etc.

[0066] In this embodiment, the second reference position is a number of preset positions on the sample surface other than the first reference position. These positions are distributed across the sample surface. In one embodiment, for a rectangular sample surface, the positions near the four corners of the rectangle can be set as the second reference positions to subsequently determine the height difference of the entire sample's region of interest. Of course, for samples with a larger area, in addition to setting the second reference positions at the corners, more second reference positions can also be set at the middle of the sample to more comprehensively present the height characteristics of the sample surface.

[0067] In this embodiment of the application, the Z-axis parameter directly reflects the height of the sample stage, such as... Figure 2 As shown, in practical applications, the initial position 0 of the Z-axis parameter can be set. When the sample stage 2 moves up and down, the Z-axis parameter will be adjusted by "+" or "-" from the initial position 0. Of course, the Z-axis parameter, which is the height of the sample stage, ultimately determines the working distance of the scanning electron microscope; the working distance is the distance between the objective lens 3 and the sample 1 (4 indicates the optical axis), as shown... Figure 2 As shown.

[0068] In practical applications, this embodiment achieves automatic focusing by adjusting the Z-axis parameters. Specifically, it adjusts the height of the sample stage's Z-axis with a certain displacement accuracy, thereby changing the working distance and ensuring the acquired image remains within the depth of field. The Z-axis parameter adjustment works as follows: at a preset magnification, the sample stage is moved by a fixed step size by adjusting the Z-axis parameters, and images are acquired after each movement. Then, the algorithm automatically selects the Z-axis parameters that provide the best image quality. Figure 2 This is a schematic diagram of focusing using a scanning electron microscope by adjusting the Z-axis parameter.

[0069] In this embodiment of the application, determining the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to when the image is clear at different reference positions includes:

[0070] On the two-dimensional plane where the sample is located, obtain the Z-axis parameters of the sample stage corresponding to the two reference positions located at the edge of the sample in a preset direction when the image is clear;

[0071] Calculate the difference between the two Z-axis parameters;

[0072] The difference is determined to be the height difference of the sample in the preset direction.

[0073] Here, when the sample is rectangular, the preset direction may include: two first preset directions where the two long sides of the sample are located and two second preset directions where the two short sides of the sample are located.

[0074] In one embodiment, with Figure 3 Taking the sample shown as an example, Figure 3 The Center 0, located at the center, is the first reference position, and Corner 1-Corner 4, located at the four corners, are the four second reference positions. The height difference h1 between Corner 1 and Corner 2, the height difference h2 between Corner 1 and Corner 3, the height difference h4 between Corner 3 and Corner 4, and the height difference h3 between Corner 2 and Corner 4 are calculated respectively to obtain the height difference of the sample in the X and Y directions at the four edges.

[0075] In this embodiment of the application, the determination of the stake point information for Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope includes:

[0076] The number of stake points for Z-axis interpolation in the preset direction is determined based on the height difference of the sample in the preset direction and the depth of field of the scanning electron microscope.

[0077] The total number of Z-axis interpolation points and the Z-axis parameters corresponding to each point are determined based on the number of Z-axis interpolation points in different preset directions during the acquisition of the region of interest image.

[0078] In practical applications, the Z-axis parameters at various locations on the sample can be calculated using a three-point fitting function for automatic interpolation. The stake interpolation method involves pre-focusing a portion of a specified region (region of interest) (first and second reference positions), then calculating the pre-focused values ​​to obtain the focusing parameters corresponding to each image block within the region of interest. Therefore, stakes at the sample edge can be interpolated at positions 20–30 μm near the edge.

[0079] In one embodiment, such as Figure 3 As shown, the number of interpolation points can be set automatically based on the height difference of the selected area and the depth of field d of the machine (a fixed parameter of the machine itself, the parameter value is different for each machine). The interpolation requires at least three points (Rm*Cn (Rm*Cn≥3), a prerequisite for the application of the focusing method in this application). The number of interpolation points for row and column differences is shown below:

[0080] Rm = Max(h2 / d, h3 / d);

[0081] Cn = Max(h1 / d, h4 / d).

[0082] In this embodiment of the application, the image acquisition of the region of interest based on the pile point information and the objective lens current value includes:

[0083] Based on image acquisition requirements, the region of interest is divided into several image blocks of equal size; wherein, a sub-region composed of a predetermined number of adjacent image blocks contains one of the stake points; the number of image blocks is greater than the total number of stake points;

[0084] Image acquisition of the region of interest is performed based on the objective lens current value and the Z-axis parameters of the pile points contained in each sub-region.

[0085] In one embodiment, the region of interest can be divided into M rows and N columns of image blocks according to the user's image acquisition requirements. Taking the first row as an example, starting from the first image block, every m image blocks include one of the stake points. When scanning the m image blocks, the constant objective lens current value and the Z-axis parameter corresponding to the stake point are used to acquire images, thereby obtaining the images corresponding to each of the m image blocks.

[0086] The method described in this application is illustrated below with an application example, including:

[0087] Step 1: Set the selected area (region of interest) of 4*3mm on the sample. 2,like Figure 4 As shown, the coordinates of the center position 0 (first reference position) and the four corner positions 1, 2, 3, 4 (second reference positions) are stored respectively;

[0088] Step 2: Control the electron beam to move to the center position 0 of the selected area, adjust the objective lens current value, obtain a clear image, and record the current Z-axis parameter (Z0) of the sample stage;

[0089] Step 3: Keeping the objective lens current value constant, move the electron beam to corner position 1;

[0090] Step 4: Set the total travel distance of the sample stage during the autofocus process to ±15µm, with each step being 2µm. Then, acquire 1k images at positions such as ±2µm, ±4µm, etc.

[0091] Step 5: Automatically record and apply the Z-axis parameter (Z1) of the sample stage when the image quality is optimal in the acquired images;

[0092] Step 6: Move the electron beam to the corner positions 2, 3, and 4 of the selected area respectively, and repeat steps 4 and 5 to record the Z-axis parameters Z2, Z3, and Z4;

[0093] Step 7: Determine the height difference of the selected area according to the corresponding Z-axis parameters: h1 = Z1 - Z2 = 30um, h2 = Z1 - Z3 = 45um, h3 = Z2 - Z4 = 50um, h4 = Z3 - Z4 = 25um;

[0094] Step 8: Based on the height difference and depth of field (d=±5um) of the selected area, set the number of stake points for automatic interpolation (Rm*Cn=5*3);

[0095] Here, Rm = Max(h2 / d,h3 / d) = Max(45 / 10,50 / 10) = Max(4.5,5) = 5;

[0096] Cn=Max(h1 / d,h4 / d)=Max(30 / 10,25 / 10)=Max(3,2.5)=3.

[0097] Step 9: Based on the objective lens current value and the Z-axis parameter corresponding to each stake point, image acquisition is performed row by row starting from the first image (first image block).

[0098] The following scenario illustrates the effect of this application compared to traditional focusing scanning methods. Here, traditional scanning refers to fixed-step autofocus. Taking a fixed step size of 5 as an example, the acquisition area size is 0.5*0.5mm. 2First, 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. This process is repeated line by line until the entire region is acquired. As shown in Table 1, this is an example of acquiring a semiconductor sample.

[0099]

[0100]

[0101] Table 1

[0102] Note: Total imaging time = number of focal points * focusing time + number of images * (single image imaging time + single image motion time);

[0103] Acquisition throughput = Acquisition area / Total imaging time;

[0104] Total imaging time improvement rate = (Total imaging time of conventional focusing - Total imaging time of block scanning focusing) / Total imaging time of conventional focusing;

[0105] As can be seen from Table 1 above, the embodiments of this application do not require time for focusing. The focusing parameters are calculated and saved during the stake point setting stage. During the array scanning imaging stage, the saved parameters can be directly applied at the corresponding positions to complete image acquisition, which greatly shortens the total imaging time and thus improves the overall imaging throughput. Compared with traditional focusing methods, its total imaging time is reduced by 59%, and the acquisition throughput is more than doubled.

[0106] Example 2

[0107] To implement the method of the embodiments of this application, the embodiments of this application also provide an image acquisition device, such as... Figure 5 As shown, the device is used in a scanning electron microscope and includes:

[0108] The processing unit 501 is configured to acquire the objective current value and the Z-axis parameter of the sample stage corresponding to a clear image at a first reference position in the region of interest; while keeping the objective current value constant, determine the Z-axis parameters of the sample stage corresponding to a number of clear images at second reference positions based on the Z-axis parameters of the sample stage; determine the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to clear images at different reference positions; and determine the stake point information of Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope.

[0109] The image acquisition unit 502 is used to acquire images of the region of interest based on the stake point information and the objective lens current value.

[0110] In this embodiment of the application, the processing unit 501 acquires the objective current value and the Z-axis parameters of the sample stage corresponding to a clear image at the first reference position in the region of interest, including:

[0111] Control the electron beam to move to the first reference position;

[0112] Adjust the objective current value of the scanning electron microscope until a clear image is obtained;

[0113] Record the Z-axis parameters of the sample stage when the image is clear.

[0114] In this embodiment of the application, the processing unit 501 determines the Z-axis parameters of the sample stage corresponding to several second reference positions where the image is clear, based on the Z-axis parameters of the sample stage, including:

[0115] For each second reference position, the total travel distance of the sample stage and the step size of each movement during the autofocusing process are configured based on the sample surface features.

[0116] Image acquisition is performed after each step the sample stage moves, until the total travel distance is completed;

[0117] Select the image with the best quality from all the acquired images, and record the Z-axis parameters of the sample stage when acquiring the image with the best quality.

[0118] In this embodiment of the application, the processing unit 501 determines the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to when the image is clear at different reference positions, including:

[0119] On the two-dimensional plane where the sample is located, obtain the Z-axis parameters of the sample stage corresponding to the reference positions located at the two sides of the sample in a preset direction when the image is clear;

[0120] Calculate the difference between the two Z-axis parameters;

[0121] The difference is determined to be the height difference of the sample in the preset direction.

[0122] In this embodiment of the application, the processing unit 501 determines the stake point information for Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope, including:

[0123] The number of stake points for Z-axis interpolation in the preset direction is determined based on the height difference of the sample in the preset direction and the depth of field of the scanning electron microscope.

[0124] The total number of Z-axis interpolation points and the Z-axis parameters corresponding to each point are determined based on the number of Z-axis interpolation points in different preset directions during the acquisition of the region of interest image.

[0125] In this embodiment of the application, the image acquisition unit 502 performs image acquisition of the region of interest based on the stake point information and the objective lens current value, including:

[0126] Based on image acquisition requirements, the region of interest is divided into several image blocks of equal size; wherein, a sub-region composed of a predetermined number of adjacent image blocks contains one of the stake points; the number of image blocks is greater than the total number of stake points;

[0127] Image acquisition of the region of interest is performed based on the objective lens current value and the Z-axis parameters of the pile points contained in each sub-region.

[0128] In practical applications, the processing unit 501 can be implemented by a processor in the image acquisition device; the image acquisition unit 502 can be implemented by an imaging device in the image acquisition device.

[0129] It should be noted that the image acquisition 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.

[0130] In one embodiment, in Figure 6 The scanning electron microscope shown includes: a Z-axis controller 1, a rangefinder 2, a sample 3, a nanometer-precision sample stage 4, a microscope tube 5, an electron gun 6, and a control module. The rangefinder 2 detects the Z-axis movement distance of the sample stage, and the Z-axis controller 1 controls the sample stage 4 to move in fixed steps along the Z-axis. The control module then processes the acquired image of the reference position to obtain optimal Z-axis parameters, which are used to control the working distance of the scanning particle beam microscope. The combined use of the Z-axis controller 1, the rangefinder 2, and the control module enables… Figure 5 The functions of the processing unit 501 and the image acquisition unit 502 described herein.

[0131] Example 3

[0132] 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 7 As shown, the scanning electron microscope 700 includes:

[0133] The image processor 701 is capable of acquiring and / or processing sample images.

[0134] The first processor 702 is connected to the image processor 701 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 of the above-mentioned technical solutions of the scanning electron microscope when running a computer program;

[0135] The computer program is stored in the first memory 703.

[0136] Specifically, the first processor 702 is used to acquire the objective current value and the Z-axis parameter of the sample stage corresponding to a clear image at a first reference position in the region of interest; while keeping the objective current value constant, it determines the Z-axis parameters of the sample stage corresponding to a number of clear images at second reference positions based on the Z-axis parameters of the sample stage; it determines the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to clear images at different reference positions; and it determines the stake information of Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope.

[0137] Image processor 701 is used to acquire images of the region of interest based on the stake point information and the objective lens current value.

[0138] In this embodiment of the application, the first processor 702 acquires the objective current value and the Z-axis parameters of the sample stage corresponding to a clear image at a first reference position in the region of interest, including:

[0139] Control the electron beam to move to the first reference position;

[0140] Adjust the objective current value of the scanning electron microscope until a clear image is obtained;

[0141] Record the Z-axis parameters of the sample stage when the image is clear.

[0142] In this embodiment of the application, the first processor 702 determines the Z-axis parameters of the sample stage corresponding to several second reference positions where the image is clear, based on the Z-axis parameters of the sample stage, including:

[0143] For each second reference position, the total travel distance of the sample stage and the step size of each movement during the autofocusing process are configured based on the sample surface features.

[0144] Image acquisition is performed after each step the sample stage moves, until the total travel distance is completed;

[0145] Select the image with the best quality from all the acquired images, and record the Z-axis parameters of the sample stage when acquiring the image with the best quality.

[0146] In this embodiment of the application, the first processor 702 determines the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to when the image is clear at different reference positions, including:

[0147] On the two-dimensional plane where the sample is located, obtain the Z-axis parameters of the sample stage corresponding to the reference positions located at the two sides of the sample in a preset direction when the image is clear;

[0148] Calculate the difference between the two Z-axis parameters;

[0149] The difference is determined to be the height difference of the sample in the preset direction.

[0150] In this embodiment of the application, the first processor 702 determines the stake point information for Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope, including:

[0151] The number of stake points for Z-axis interpolation in the preset direction is determined based on the height difference of the sample in the preset direction and the depth of field of the scanning electron microscope.

[0152] The total number of Z-axis interpolation points and the Z-axis parameters corresponding to each point are determined based on the number of Z-axis interpolation points in different preset directions during the acquisition of the region of interest image.

[0153] In this embodiment of the application, the image processor 701 performs image acquisition of the region of interest based on the stake point information and the objective lens current value, including:

[0154] Based on image acquisition requirements, the region of interest is divided into several image blocks of equal size; wherein, a sub-region composed of a predetermined number of adjacent image blocks contains one of the stake points; the number of image blocks is greater than the total number of stake points;

[0155] Image acquisition of the region of interest is performed based on the objective lens current value and the Z-axis parameters of the pile points contained in each sub-region.

[0156] It should be noted that the specific processing procedures of the image processor 701 and the first processor 702 can be understood by referring to the above method, and will not be repeated here.

[0157] Of course, in practical applications, the various components in the scanning electron microscope 700 are coupled together via a bus system 704. It can be understood that the bus system 704 is used to achieve communication between these components. In addition to a data bus, the bus system 704 also includes a power bus, a control bus, and a status signal bus. However, for clarity, in... Figure 7 The general designated all buses as Bus System 704.

[0158] The first memory 703 in this embodiment is used to store various types of data to support the operation of the scanning electron microscope 700. Examples of such data include any computer program used to operate on the scanning electron microscope 700.

[0159] The methods disclosed in the embodiments of this application can be applied to the first processor 702, or implemented by the first processor 702. The first processor 702 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 702. The first processor 702 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 702 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 reflected 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 703. The first processor 702 reads the information in the first memory 703 and completes the steps of the aforementioned method in combination with its hardware.

[0160] In an exemplary embodiment, the scanning electron microscope 700 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 methods.

[0161] 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 703 storing a computer program. This computer program can be executed by the first processor 702 of the scanning electron microscope 700 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.

[0162] 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.

[0163] Furthermore, the technical solutions described in the embodiments of this application can be combined arbitrarily without conflict.

[0164] 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. An image acquisition method, characterized in that, The method includes: Obtain the objective current value and the Z-axis parameters of the sample stage when the image at the first reference position in the region of interest is clear; With the objective current value remaining constant, the Z-axis parameters of the sample stage are determined based on the Z-axis parameters of the sample stage when the images are clear at several second reference positions. The height difference of the sample in the preset direction is determined based on the Z-axis parameters of the sample stage when the image is clear at different reference positions. Based on the height difference and the depth of field of the scanning electron microscope, the stake point information of Z-axis interpolation during image acquisition is determined; Image acquisition of the region of interest is performed based on the pile point information and the objective lens current value; The stake point information for determining Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope includes: The number of stake points for Z-axis interpolation in the preset direction is determined based on the height difference of the sample in the preset direction and the depth of field of the scanning electron microscope. The total number of Z-axis interpolation points and the Z-axis parameters corresponding to each point are determined based on the number of Z-axis interpolation points in different preset directions during the acquisition of the region of interest image.

2. The method according to claim 1, characterized in that, The acquisition of the objective current value and the Z-axis parameters of the sample stage corresponding to the image being clear at the first reference position in the region of interest includes: Control the electron beam to move to the first reference position; Adjust the objective current value of the scanning electron microscope until a clear image is obtained; Record the Z-axis parameters of the sample stage when the image is clear.

3. The method according to claim 1, characterized in that, The determination of the Z-axis parameters of the sample stage at several second reference positions where the image is clear, based on the Z-axis parameters of the sample stage, includes: For each second reference position, the total travel distance of the sample stage and the step size of each movement during the autofocusing process are configured based on the sample surface features. Image acquisition is performed after each step the sample stage moves, until the total travel distance is completed; Select the image with the best quality from all the acquired images, and record the Z-axis parameters of the sample stage when acquiring the image with the best quality.

4. The method according to claim 1, characterized in that, The method of determining the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to when the image is clear at different reference positions includes: On the two-dimensional plane where the sample is located, obtain the Z-axis parameters of the sample stage corresponding to the reference positions located at the two sides of the sample in a preset direction when the image is clear; Calculate the difference between the two Z-axis parameters; The difference is determined to be the height difference of the sample in the preset direction.

5. The method according to claim 1, characterized in that, The image acquisition of the region of interest based on the stake point information and the objective lens current value includes: Based on image acquisition requirements, the region of interest is divided into several image blocks of equal size; wherein, a sub-region composed of a predetermined number of adjacent image blocks contains one of the stake points; the number of image blocks is greater than the total number of stake points; Image acquisition of the region of interest is performed based on the objective lens current value and the Z-axis parameters of the pile points contained in each sub-region.

6. An image acquisition device, characterized in that, The device is used in a scanning electron microscope and includes: The processing unit is configured to acquire the objective current value and the Z-axis parameter of the sample stage corresponding to a clear image at a first reference position in the region of interest; while keeping the objective current value constant, determine the Z-axis parameters of the sample stage corresponding to a number of clear images at second reference positions based on the Z-axis parameters of the sample stage; determine the height difference of the sample in a preset direction based on the Z-axis parameters of the sample stage corresponding to clear images at different reference positions; and determine the stake point information of Z-axis interpolation during image acquisition based on the height difference and the depth of field of the scanning electron microscope. The processing unit is also used to determine the number of stake points for Z-axis interpolation in the preset direction based on the height difference of the sample in the preset direction and the depth of field of the scanning electron microscope; and to determine the total number of stake points for Z-axis interpolation and the Z-axis parameter corresponding to each stake point during the acquisition of the region of interest image based on the number of stake points for Z-axis interpolation in different preset directions. An image acquisition unit is used to acquire images of the region of interest based on the stake point information and the objective lens current value.

7. A scanning electron microscope, characterized in that, include: The first processor is used to acquire the objective current value and the Z-axis parameters of the sample stage when the image at the first reference position in the region of interest is clear. With the objective current value remaining constant, the Z-axis parameters of the sample stage are determined based on the Z-axis parameters of the sample stage when the images are clear at several second reference positions; the height difference of the sample in a preset direction is determined based on the Z-axis parameters of the sample stage when the images are clear at different reference positions; and the stake information of Z-axis interpolation during image acquisition is determined based on the height difference and the depth of field of the scanning electron microscope. The first processor is further configured to determine the number of stake points for the Z-axis interpolation in the preset direction based on the height difference of the sample in a preset direction and the depth of field of the scanning electron microscope; The total number of Z-axis interpolation points and the Z-axis parameters corresponding to each Z-axis point are determined based on the number of Z-axis interpolation points in different preset directions during the image acquisition of the region of interest. An image processor is used to acquire images of the region of interest based on the stake point information and the objective lens current value.

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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