A standard sample preparation method and standard sample for scanning electron microscope calibration

Abstract

The application discloses a standard sample preparation method and a standard sample for scanning electron microscope calibration, and meets the whole-process calibration requirements of "centering-adjusting an image-guiding calibration-scanning direction calibration-distortion calibration-angle calibration-magnification calibration" in a single standard sample, so that the calibration process is simplified without frequent moving of the standard sample; through the layout mode of the feature area, the moving amount of the standard sample in the calibration process is significantly reduced, and the calibration efficiency is improved; further through a differentiated film deposition mode, the feature height of each calibration area can be ensured to be consistent, the charging problem is reduced, and the contrast and conductivity under different imaging modes are ensured.

Description

Technical Field

[0001] This invention belongs to the field of microscope calibration, and more specifically, relates to a method for preparing standard samples and standard samples for scanning electron microscope calibration. Background Technology

[0002] Scanning electron microscopes (SEMs), as high-end scientific instruments, play an indispensable role in many fields such as materials science, biological research, and semiconductor manufacturing. By scanning the sample surface with an electron beam and detecting the signals generated by the interaction between electrons and the sample, they can reveal the microscopic morphology of the sample surface at nanometer-level resolution, providing crucial data support for scientific research and industrial production.

[0003] However, the accuracy of SEM observations and measurement data is highly dependent on precise calibration. Uncalibrated SEMs can exhibit image distortion and dimensional measurement deviations, potentially leading to errors in scientific judgment. In high-precision fields such as semiconductor chip manufacturing, this can even result in decreased product quality or production failure. Therefore, regular calibration is a core element in ensuring the reliable operation of SEMs, and the accuracy and efficiency of the calibration process depend entirely on the performance of the standard samples.

[0004] Existing standard samples are mostly designed with a single graphic as the core, which can only partially meet the needs of a certain calibration step and has not formed a feature design system "based on the whole process calibration logic". For example, some standard samples are only designed for magnification calibration, and some can only assist in focus adjustment. They cannot cover the complex requirements of the entire SEM "image adjustment-calibration" process and cannot meet the needs of scientific research and industrial production for high-precision and comprehensive calibration. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a standard sample preparation method and standard sample for scanning electron microscope calibration, thereby solving the technical problem that the existing standard sample preparation methods are difficult to meet the calibration requirements of the entire SEM process.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a method for preparing a standard sample for scanning electron microscope calibration is provided, comprising:

[0007] Based on calibration requirements, the sample substrate to be processed is determined, and the sample substrate is pretreated.

[0008] Based on the calibration steps of scanning electron microscopy, feature regions are laid out to obtain the relative positions of each feature region within the calibration area corresponding to the same microscope magnification; the feature regions are used to process feature patterns corresponding to the calibration requirements of different calibration steps.

[0009] For different microscope magnifications, the sample substrate is divided based on the relative positions of the feature regions within the calibration area corresponding to the same microscope magnification to obtain calibration areas corresponding to each microscope magnification, and a film is deposited on the calibration areas corresponding to each microscope magnification; wherein, different thin film deposition methods are used for calibration areas with magnifications greater than a preset magnification and calibration areas with magnifications less than a preset magnification.

[0010] Following the order of increasing microscope magnification, each feature region within the calibration area corresponding to different microscope magnifications is processed sequentially to form feature patterns corresponding to the calibration requirements of each calibration step under different microscope magnifications, thus obtaining standard samples.

[0011] The physical arrangement order of the feature regions matches the execution order of the calibration steps; the feature patterns include image adjustment feature patterns for testing image adjustment capabilities, and direction-type calibration feature patterns, distortion calibration feature patterns, basic angle calibration feature patterns, and magnification calibration feature patterns for calibration.

[0012] According to the above-mentioned standard sample preparation method for scanning electron microscope calibration, the orientation calibration feature pattern includes lens rotation mirror detection feature and transverse and longitudinal axis direction detection feature; wherein, the lens rotation mirror detection feature corresponds to a substrate corner-cut structure, and the transverse and longitudinal axis direction detection feature corresponds to an asymmetric one-dimensional grating structure.

[0013] According to the above-mentioned standard sample preparation method for scanning electron microscope calibration, the distortion calibration feature pattern includes a first screen center positioning feature, a line segment length and included angle deviation detection feature, and a first rotation angle recognition feature; wherein, the first screen center positioning feature corresponds to a concentric circle structure, the line segment length and included angle deviation detection feature corresponds to a circle structure containing multiple diameters with equal included angles, and the first rotation angle recognition feature corresponds to a circle structure with asymmetrical markings on a diameter line segment.

[0014] According to the above-mentioned standard sample preparation method for scanning electron microscope calibration, the basic angle calibration feature pattern includes multi-angle calibration features and a second rotation angle identification feature; wherein, the multi-angle calibration features correspond to a multi-angle line segment structure, and the second rotation angle identification feature corresponds to a line segment structure with asymmetric markings.

[0015] According to the above-mentioned standard sample preparation method for scanning electron microscope calibration, the magnification calibration feature pattern includes a multi-magnification feature, a second screen center positioning feature, and a third rotation angle recognition feature; the multi-magnification feature corresponds to a nested multi-size square structure, the second screen center positioning feature corresponds to a square structure with a specific mark set at the center, and the third rotation angle recognition feature corresponds to a square structure with an asymmetrical mark set on one side.

[0016] According to the above-mentioned standard sample preparation method for scanning electron microscope calibration, the scanning electron microscope-based calibration step involves feature region layout to obtain the relative positions of each feature region within the calibration area corresponding to the same microscope magnification. Specifically, this includes:

[0017] For any type of feature pattern, the multiple features included in the any type of feature pattern are merged to obtain the same type of merged feature corresponding to the any type of feature pattern;

[0018] Feature matching is performed based on the same type of merged features corresponding to various feature patterns. Different merged features are further merged to obtain cross-class merged features.

[0019] Assign corresponding feature regions to each cross-class merged feature and the remaining single-class merged features;

[0020] Based on the calibration steps corresponding to each cross-class merging feature and the remaining single-class merging features, as well as the execution order of each calibration step, the relative positions of each feature region within the calibration area corresponding to the same microscope magnification are determined; wherein, the physical arrangement order of the feature regions matches the execution order of the calibration steps, and the feature regions corresponding to consecutively executed calibration steps are directly adjacent.

[0021] According to the above-mentioned standard sample preparation method for scanning electron microscope calibration, the step of dividing the sample substrate based on the relative positions between characteristic regions within the calibration region corresponding to the same microscope magnification to obtain the calibration region corresponding to each microscope magnification specifically includes:

[0022] Following the order of increasing microscope magnification, the processing area corresponding to the current microscope magnification is divided into a feature area and a processing area corresponding to the next microscope magnification, based on the relative positions of each feature area within the calibration area corresponding to the current microscope magnification and the same microscope magnification. The processing area corresponding to the smallest microscope magnification is the complete processing area of ​​the sample substrate.

[0023] According to the above-described standard sample preparation method for scanning electron microscope calibration, different thin film deposition methods are used for calibration areas with magnifications greater than a preset value and calibration areas with magnifications less than a preset value, specifically including:

[0024] For calibration areas smaller than the preset magnification, a 70nm chromium thin film is deposited;

[0025] For calibration regions with a magnification greater than a preset value, a combined thin film consisting of 20 nm chromium and 50 nm gold is deposited.

[0026] According to a second aspect of the invention, a standard sample for scanning electron microscope calibration is provided, the standard sample being prepared based on the method described in the first aspect.

[0027] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0028] Based on the calibration steps of scanning electron microscopy, feature regions are laid out to obtain the relative positions of each feature region within the calibration area corresponding to the same microscope magnification. Then, for different microscope magnifications, based on the relative positions of each feature region within the calibration area corresponding to the same microscope magnification, the sample substrate is divided to obtain calibration areas corresponding to each microscope magnification, and a film is deposited on each calibration area corresponding to each microscope magnification. Different thin film deposition methods are used for calibration areas above and below a preset magnification. Next, following the order of increasing microscope magnification, each feature region within the calibration area corresponding to different microscope magnifications is processed sequentially to form feature patterns corresponding to the calibration requirements of each calibration step at different microscope magnifications, thus obtaining a standard sample. The physical arrangement of the feature regions matches the execution order of the calibration steps. The feature patterns include image adjustment feature patterns for testing image adjustment capabilities, as well as orientation calibration feature patterns, distortion calibration feature patterns, basic angle calibration feature patterns, and magnification calibration feature patterns for calibration. A single standard sample satisfies the entire calibration process requirements of "centering-image adjustment-navigation calibration-scanning orientation calibration-distortion calibration-angle calibration-magnification calibration," eliminating the need for frequent standard sample adjustments and simplifying the calibration process. The layout of the feature regions significantly reduces the amount of standard sample movement during calibration, improving calibration efficiency. Furthermore, differentiated thin-film deposition methods ensure high consistency of features across calibration areas, reducing charge issues and guaranteeing contrast and conductivity under different imaging modes. Attached Figure Description

[0029] Figure 1 This is a schematic flowchart of a standard sample preparation method for scanning electron microscope calibration provided in an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the lens rotation mirror detection feature provided in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the detection features in the horizontal and vertical axes provided in an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the optical path alignment features provided in an embodiment of the present invention;

[0033] Figure 5 A schematic diagram illustrating the focusing and astigmatism adjustment features provided in an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of similar merged features of the distortion calibration feature pattern provided in an embodiment of the present invention;

[0035] Figure 7 A schematic diagram of similar merged features of the basic angle calibration feature pattern provided in the embodiments of the present invention;

[0036] Figure 8 This is a schematic diagram of similar merged features of the magnification calibration feature pattern provided in an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, 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 and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] This invention provides a method for preparing standard samples for scanning electron microscope calibration, such as... Figure 1 As shown, it includes:

[0039] Step 110: Based on calibration requirements, determine the sample substrate to be processed and preprocess the sample substrate;

[0040] Step 120: Based on the calibration steps of the scanning electron microscope, feature regions are laid out to obtain the relative positions of each feature region within the calibration area corresponding to the same microscope magnification; the feature regions are used to process feature patterns corresponding to the calibration requirements of different calibration steps.

[0041] Step 130: For different microscope magnifications, the sample substrate is divided based on the relative positions of the feature regions within the calibration area corresponding to the same microscope magnification to obtain calibration areas corresponding to each microscope magnification, and a film is deposited on the calibration areas corresponding to each microscope magnification; wherein, different thin film deposition methods are used for calibration areas with magnifications greater than a preset magnification and calibration areas with magnifications less than a preset magnification.

[0042] Step 140: Process each feature region within the calibration area corresponding to different microscope magnifications in order of increasing microscope magnification to form feature patterns that meet the calibration requirements of each calibration step under different microscope magnifications, and obtain standard samples.

[0043] The physical arrangement order of the feature regions matches the execution order of the calibration steps; the feature patterns include image adjustment feature patterns for testing image adjustment capabilities, and direction-type calibration feature patterns, distortion calibration feature patterns, basic angle calibration feature patterns, and magnification calibration feature patterns for calibration.

[0044] Specifically, in order to prepare a multifunctional and integrated standard sample, the layout of its surface feature pattern strictly corresponds to the standardized SEM calibration process, which can guide users to complete the entire calibration process from image preprocessing to precise calibration of various parameters in an efficient, orderly and continuous manner, thereby significantly improving the efficiency, convenience and overall accuracy of the calibration work.

[0045] To achieve the above objectives, the embodiments of the present invention first select the sample substrate to be processed based on calibration requirements. For example, a square silicon wafer with a side length of not less than 5 mm can be used. The microscopic feature etching area of ​​the standard sample is a square area with a side length of not less than 4 mm. Subsequently, according to the calibration requirements of different microscope magnifications, this microscopic feature etching area will be divided into several sub-regions of different sizes to prepare microscopic features corresponding to the microscope magnification, ensuring the coverage of full magnification calibration. After selecting the sample substrate, it needs to be pre-treated, such as cleaning and surface planarization, to ensure the accuracy of subsequent uniform film deposition and high-precision pattern etching.

[0046] Subsequently, the layout of feature regions is planned based on the calibration procedure logic of scanning electron microscopy. This plan establishes the relative positional relationships between various feature regions serving different calibration sub-items (such as image adjustment, orientation calibration, distortion calibration, angle calibration, and magnification calibration) at the same microscope magnification. These feature regions are used to process feature patterns corresponding to the calibration requirements of different calibration steps. These feature patterns include image adjustment feature patterns for testing image adjustment capabilities, as well as various types of feature patterns used for calibration, such as orientation calibration feature patterns, distortion calibration feature patterns, basic angle calibration feature patterns, and magnification calibration feature patterns.

[0047] It should be noted that, in order to achieve accuracy and consistency throughout the calibration process, this invention has established unified quantitative design rules:

[0048] (1) Line width / spacing benchmark: The total size of the maximum graphic on the screen at the corresponding magnification is D. The default line width w and spacing s are approximately equal to D / 20 to ensure that the lines and spacing are adapted to the screen's capacity limit while ensuring that the features are clearly distinguishable. The specific magnification ratio and the line width / spacing correspondence are shown in Table 1.

[0049]

[0050] (2) Concentric graphics (circle / square): A single area can accommodate 5 levels, and the total size = 10w + 10s ≈ D (because each level contains opposite side lines, and the line width and spacing each occupy 5 sets of double-sided distribution).

[0051] (3) Raster graphics: A single area can accommodate 10 lines, and the total size = 10w + 9s ≈ D (because the lines are distributed on one side, the number of spacings is less than the number of lines).

[0052] (4) Marking size reference: The line width of both the asymmetric mark and the center mark is equal to w, which is consistent with the main feature to avoid interfering with the recognition and measurement of the main feature.

[0053] In some embodiments, the orientation calibration feature pattern includes lens rotation and mirror detection features and transverse and longitudinal axis orientation detection features. In low-magnification (1-5x) optical calibration steps, the standard sample needs to provide lens rotation and mirror detection features to eliminate the possibility of lens rotation or mirroring. Therefore, the lens rotation and mirror detection features can be designed as a corner-cut substrate structure. For example, a right-angled triangle with sides of 0.5mm × 1mm can be cut from a corner of a square substrate that has no microscopic features, ensuring that the lens rotation and mirroring state can be uniquely determined from the image, enabling rapid lens calibration. Figure 2As shown. Additionally, some low-magnification (below 30x) calibration steps require verification of the correct x and y component directions of the scan signal. Considering the requirement for the maximum image size at the corresponding magnification, the detection features along the horizontal and vertical axes can be designed as follows: Figure 3 The asymmetric one-dimensional grating structure shown adopts a dual-directional design of horizontal and vertical. The grating period can be set to D / 10, and the line width and spacing to D / 20. A line with an angle of 90° ± 0.1° is placed at an asymmetric position (offset = D / 4) at the center of the grating, with a line width of D / 20, where D is the maximum side length of the feature region at the corresponding magnification. The line length only needs to avoid making the pattern symmetrical, providing a clear directional reference to confirm the direction of the scanning signal.

[0054] In other embodiments, the distortion calibration feature pattern includes a first screen center positioning feature, a line segment length and included angle deviation detection feature, and a first rotation angle recognition feature. Specifically, based on the calibration requirement of locating to the screen center during image distortion calibration, the first screen center positioning feature can be designed as a concentric circle structure. The outer circle diameter can be set to D, and the line width and spacing can be set to D / 20. Based on the calibration requirement of measuring vertical lengths during image distortion calibration, which necessitates rotating at multiple angles and measuring the included angles, the line segment length and included angle deviation detection feature can be designed as a circle structure containing multiple diameters with equal included angles. For example, four diameters with equal included angles (45°±0.1°) can be set within the circle, with a line segment length of D and a line width of D / 20. Utilizing the constant length of the circle diameter in any direction and the equal included angle setting, the degree of distortion can be accurately quantified by measuring the line segment length deviation and included angle. Furthermore, when rotating multiple angles during the image distortion calibration process, it is necessary to confirm the current angle to eliminate the influence of rotational symmetry. Therefore, the first rotation angle recognition feature can be designed as a circular structure with an asymmetric mark on a diameter line segment. For example, a short line segment can be set as an asymmetric mark on a diameter line segment, with a line width of D / 20 and a length not exceeding the diameter length to avoid creating symmetry in the image. The angle between the line segment and the corresponding diameter is 90°±0.1°, which is used for rotation angle recognition.

[0055] In other embodiments, the basic angle calibration feature pattern includes multi-angle calibration features and a second rotation angle recognition feature. Since the calibration steps corresponding to the image's basic angle calibration require positioning to the screen center, the multi-angle calibration features can be designed as multi-angle line segment structures. For example, a horizontal line segment can be used as the main line, with its center as the origin. An intersecting line segment is set for each fixed rotation angle, which can be selected as 15° / 30° / 45° (tolerance ±0.1°), forming a multi-angle calibration reference. The line segment width can be set to D / 20, and the center of the main line segment can serve as a marker for screen center positioning. Furthermore, some calibration steps corresponding to the image's basic angle calibration require confirming the rotation angle; therefore, the second rotation angle recognition feature can be correspondingly set with a line segment structure bearing asymmetrical markings. For example, a short line segment can be set as an asymmetric marker on a line segment, with the line width set to D / 20. If other line segments exist, the length of the asymmetric marker will not intersect with other line segments, and the angle between the asymmetric marker and the line segment to which the asymmetric marker is set will be 90°±0.1°, which is used for rotation angle identification.

[0056] In other embodiments, the magnification calibration feature pattern includes a multi-magnification feature, a second screen center positioning feature, and a third rotation angle recognition feature. Specifically, based on the full-range magnification calibration requirements, the multi-magnification feature can be designed as a nested multi-size square structure corresponding to all magnification ranges, covering all ranges by magnification level; that is, one square corresponds to one magnification range. The line width and spacing of the squares can be set to D / 20, and the right angles of the squares can simultaneously perform deflection angle and included angle fine-tuning. Based on the requirement of positioning to the screen center in the magnification calibration step, the second screen center positioning feature can be designed as a square structure with a specific mark at the center, such as a cross-shaped or dot-shaped center mark. The line width is set to D / 20. If a cross-shaped center mark is used, the intersection angle of the cross mark can be set to 90°±0.1° to ensure the center positioning accuracy during calibration. In addition, based on the requirement of identifying the rotation angle in the magnification calibration step, the third rotation angle identification feature can be designed as a square structure with an asymmetrical mark on one side. The asymmetrical mark can be a short line segment, the line width of which can be set to D / 20, and the angle between the line segment and the side length is 90°±0.1°, for rotation angle identification.

[0057] In other embodiments, the image adjustment feature pattern used to test image adjustment capabilities includes optical path alignment features and focus and astigmatism adjustment features. Optical path alignment requires adjusting the gun alignment coil, condenser lens coil, objective lens coil, and objective lens alignment coil at low magnification (typically 30-1000x). Depending on the requirements of the alignment process, the standard sample needs to have a uniform morphology and clear features at the corresponding magnification to observe the uniformity of the coil magnetic field and check for nonlinear problems such as distortion, barrel distortion, and pincushion distortion. Therefore, the optical path alignment feature can be designed as an equally spaced rectangular dot matrix structure, where the linewidth and spacing can be set to D / 20, and the number of dots can be set to 10×10, such as... Figure 4 As shown. Furthermore, based on the focusing and astigmatism correction requirements (300,000-200,000x magnification across all settings, requiring multi-directional boundaries, circular features, and good conductivity), and the need to move the circle to the center of the screen and rotate the image after focusing and astigmatism correction to preliminarily determine if distortion exists, the focusing and astigmatism adjustment feature can be designed as a circular structure with at least two mutually perpendicular diameters inside, such as... Figure 5 As shown. This design facilitates focus / astigmatism adjustment. The center of the intersecting diameters is used to locate the center of the screen, and the length and included angle of the two diameters can be measured for preliminary judgment of image distortion.

[0058] Based on the image features of the aforementioned various feature patterns and the execution steps of each calibration step in the entire microscope calibration process, feature regions corresponding to the same microscope magnification are laid out. It should be noted that, in planning the layout of feature regions in this embodiment of the invention, the movement of the standard sample is minimized during microscope calibration, thereby improving calibration efficiency. The standard setting for the layout planning is that the physical arrangement order of each feature region is consistent with the execution order of the calibration steps. Specifically, for the lens rotation mirror detection feature, since it has a corner-cut substrate structure, the substrate needs to be directly processed. Therefore, this feature can be disregarded in the layout of feature regions corresponding to the same microscope magnification and in subsequent calibration region division steps.

[0059] In some embodiments, to minimize the movement of standard samples during calibration, when arranging feature regions at the same microscope magnification, feature regions can be merged and then reassigned based on the compatibility between feature patterns of the same type and between feature patterns of different types. This approach ensures that features corresponding to adjacent calibration steps are located in the same or adjacent feature regions, and also reduces the number of feature regions, thereby ensuring that full-magnification microscopic features can be arranged within a limited space.

[0060] Specifically, for any type of feature pattern, the various features included in that type of feature pattern can be merged to obtain the corresponding merged features of that type of feature pattern. For example, for a distortion calibration feature pattern, the features it contains are compatible with each other. Therefore, its first screen center positioning feature, line segment length and included angle deviation detection feature, and first rotation angle recognition feature can be merged to obtain, as shown below. Figure 6 The similar merged features are shown below. Similarly, for the basic angle calibration feature pattern, it can be determined that its multi-angle calibration features and second rotation angle recognition features are compatible, therefore they are merged to obtain the following: Figure 7 The similar merged features are shown below. For the magnification calibration feature pattern, it can be determined that its multi-magnification features, second screen center positioning features, and third rotation angle recognition features are also compatible. Therefore, these three features can be merged to obtain the following: Figure 8 The feature shown is the merging of similar types.

[0061] Subsequently, feature matching is performed based on the similar merged features corresponding to various feature patterns. The matched different merged features are then further merged to obtain cross-class merged features. Here, the compatibility of the similar merged features corresponding to various feature patterns can be determined based on their image characteristics, allowing for further merging of compatible different merged features. For example, since the similar merged features of the distortion calibration feature pattern and the similar merged features of the basic angle calibration feature pattern have high similarity, and the similar merged features of the distortion calibration feature pattern contain the characteristics required by the similar merged features of the basic angle calibration feature pattern, they can be merged. For instance, only the similar merged features of the distortion calibration feature pattern can be retained.

[0062] After completing the above two-stage merging operation, corresponding feature regions can be assigned to each cross-class merged feature and the remaining single-class merged features. Then, based on the calibration steps corresponding to each cross-class merged feature and the remaining single-class merged features, and the execution order of each calibration step, the relative positions between the feature regions are determined. The layout principle for determining the relative positions between feature regions is that the physical arrangement order of the feature regions matches the execution order of the calibration steps, and the feature regions corresponding to consecutively executed calibration steps are directly adjacent.

[0063] After determining the relative positions of the feature regions within the calibration area corresponding to the same microscope magnification, the pre-treated substrate surface is divided into regions to meet the calibration requirements of different microscope magnifications. An independent calibration region is assigned to each magnification, and a coating is applied to the calibration region corresponding to each microscope magnification. The independent calibration region assignment for each magnification can be based on the number of feature regions and their relative positions. During coating, different thin film deposition methods are used for calibration regions with magnifications greater than a preset value and those with magnifications less than a preset value to ensure high consistency of features across regions, reduce charging issues, and guarantee contrast and conductivity under different imaging modes.

[0064] In some embodiments, the processing area corresponding to the current microscope magnification can be divided into a feature area and a processing area corresponding to the next microscope magnification, based on the relative positions of the feature areas within the calibration area corresponding to the current microscope magnification and the microscope magnification itself, in ascending order of microscope magnification. The processing area corresponding to the smallest microscope magnification is the complete processing area of ​​the sample substrate, i.e., the microscopic feature etching area of ​​the standard sample mentioned above. Considering the convenience of subsequent thin film deposition and the uniformity of the coating, the corner of the processing area corresponding to the current microscope magnification (e.g., the lower right corner) can be designated as the processing area corresponding to the next microscope magnification. This ensures that the processing areas corresponding to the largest magnifications (e.g., 5000x and above) are concentrated in the corners of the entire substrate. When implementing differentiated thin film deposition processes for calibration areas at different magnifications, there are clear and regular boundaries between the differentiated coating areas.

[0065] In some embodiments, a 70 nm chromium film can be deposited for calibration regions with a magnification smaller than a preset value; for calibration regions with a magnification larger than a preset value, a combined film of 20 nm chromium and 50 nm gold can be deposited.

[0066] Finally, following the order of increasing microscope magnification, each feature region within the calibration area corresponding to different microscope magnifications is processed sequentially to form feature patterns corresponding to the calibration requirements of each calibration step under different microscope magnifications, thus obtaining standard samples.

[0067] In summary, the preparation method provided by this invention involves laying out feature regions based on the calibration steps of a scanning electron microscope to obtain the relative positions of each feature region within the calibration area corresponding to the same microscope magnification. Then, for different microscope magnifications, based on the relative positions of each feature region within the calibration area corresponding to the same microscope magnification, the sample substrate is divided to obtain calibration areas corresponding to each microscope magnification, and a film is deposited on each calibration area corresponding to each microscope magnification. Different thin film deposition methods are used for calibration areas with magnifications greater than a preset value and calibration areas with magnifications less than a preset value. Next, following the order of increasing microscope magnification, each feature region within the calibration area corresponding to different microscope magnifications is processed sequentially to form feature patterns corresponding to the calibration requirements of each calibration step at different microscope magnifications. A standard sample is obtained; the physical arrangement order of the feature regions matches the execution order of the calibration steps; the feature patterns include image adjustment feature patterns for testing image adjustment capabilities, and orientation calibration feature patterns, distortion calibration feature patterns, basic angle calibration feature patterns, and magnification calibration feature patterns for calibration. A single standard sample satisfies the entire calibration process requirements of "centering-image adjustment-navigation calibration-scanning orientation calibration-distortion calibration-angle calibration-magnification calibration," eliminating the need for frequent standard sample adjustments and simplifying the calibration process. The feature region layout significantly reduces the amount of standard sample movement during calibration, improving calibration efficiency. Furthermore, differentiated thin-film deposition methods ensure high consistency of features across calibration areas, reducing charge issues and guaranteeing contrast and conductivity under different imaging modes.

[0068] This invention also provides a standard sample for scanning electron microscope calibration, which is prepared based on the standard sample preparation method for scanning electron microscope calibration as described in any of the above embodiments.

[0069] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0070] 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 method for preparing a standard sample for scanning electron microscope calibration, characterized in that, include: Based on calibration requirements, the sample substrate to be processed is determined, and the sample substrate is pretreated. Based on the calibration steps of scanning electron microscopy, feature regions are laid out to obtain the relative positions of each feature region within the calibration area corresponding to the same microscope magnification; the feature regions are used to process feature patterns corresponding to the calibration requirements of different calibration steps. For different microscope magnifications, the sample substrate is divided based on the relative positions of the feature regions within the calibration area corresponding to the same microscope magnification to obtain calibration areas corresponding to each microscope magnification, and a film is deposited on the calibration areas corresponding to each microscope magnification; wherein, different thin film deposition methods are used for calibration areas with magnifications greater than a preset magnification and calibration areas with magnifications less than a preset magnification. Following the order of increasing microscope magnification, each feature region within the calibration area corresponding to different microscope magnifications is processed sequentially to form feature patterns corresponding to the calibration requirements of each calibration step under different microscope magnifications, thus obtaining standard samples. The physical arrangement order of the feature regions matches the execution order of the calibration steps; the feature patterns include image adjustment feature patterns for testing image adjustment capabilities, and directional calibration feature patterns, distortion calibration feature patterns, basic angle calibration feature patterns, and magnification calibration feature patterns for calibration. The calibration step based on scanning electron microscopy involves feature region layout to obtain the relative positions of each feature region within the calibration area corresponding to the same microscope magnification. Specifically, this includes: For any type of feature pattern, the multiple features included in the any type of feature pattern are merged to obtain the same type of merged feature corresponding to the any type of feature pattern; Feature matching is performed based on the same type of merged features corresponding to various feature patterns. Different merged features are further merged to obtain cross-class merged features. Assign corresponding feature regions to each cross-class merged feature and the remaining single-class merged features; Based on the calibration steps corresponding to each cross-class merging feature and the remaining single-class merging features, as well as the execution order of each calibration step, the relative positions of each feature region within the calibration area corresponding to the same microscope magnification are determined; wherein, the physical arrangement order of the feature regions matches the execution order of the calibration steps, and the feature regions corresponding to consecutively executed calibration steps are directly adjacent.

2. The method for preparing standard samples for scanning electron microscope calibration as described in claim 1, characterized in that, The directional calibration feature pattern includes lens rotation mirror detection features and horizontal and vertical axis direction detection features; wherein, the lens rotation mirror detection features correspond to a substrate corner-cut structure, and the horizontal and vertical axis direction detection features correspond to an asymmetric one-dimensional grating structure.

3. The method for preparing standard samples for scanning electron microscope calibration as described in claim 1, characterized in that, The distortion calibration feature pattern includes a first screen center positioning feature, a line segment length and included angle deviation detection feature, and a first rotation angle recognition feature; wherein, the first screen center positioning feature corresponds to a concentric circle structure, the line segment length and included angle deviation detection feature corresponds to a circle structure containing multiple diameters with equal included angles, and the first rotation angle recognition feature corresponds to a circle structure with asymmetrical markings on a diameter line segment.

4. The method for preparing standard samples for scanning electron microscope calibration as described in claim 1, characterized in that, The basic angle calibration feature pattern includes a multi-angle calibration feature and a second rotation angle recognition feature; wherein, the multi-angle calibration feature corresponds to a multi-angle line segment structure, and the second rotation angle recognition feature corresponds to a line segment structure with asymmetric markings.

5. The method for preparing standard samples for scanning electron microscope calibration as described in claim 1, characterized in that, The magnification calibration feature pattern includes a multi-magnification feature, a second screen center positioning feature, and a third rotation angle recognition feature; the multi-magnification feature corresponds to a nested multi-size square structure, the second screen center positioning feature corresponds to a square structure with a specific mark set at the center, and the third rotation angle recognition feature corresponds to a square structure with an asymmetrical mark set on one side.

6. The method for preparing a standard sample for scanning electron microscope calibration as described in any one of claims 1 to 5, characterized in that, The step of dividing the sample substrate based on the relative positions of feature regions within the calibration region corresponding to the same microscope magnification to obtain calibration regions corresponding to each microscope magnification specifically includes: Following the order of increasing microscope magnification, the processing area corresponding to the current microscope magnification is divided into a feature area and a processing area corresponding to the next microscope magnification, based on the relative positions of each feature area within the calibration area corresponding to the current microscope magnification and the same microscope magnification. The processing area corresponding to the smallest microscope magnification is the complete processing area of ​​the sample substrate.

7. The method for preparing standard samples for scanning electron microscope calibration as described in any one of claims 1 to 5, characterized in that, The different thin film deposition methods used for calibration regions with magnification greater than the preset magnification and calibration regions with magnification less than the preset magnification specifically include: For calibration areas smaller than the preset magnification, a 70nm chromium thin film is deposited; For calibration regions with a magnification greater than a preset value, a combined thin film consisting of 20 nm chromium and 50 nm gold is deposited.

8. A standard sample for scanning electron microscope calibration, characterized in that, The standard sample is prepared based on the standard sample preparation method for scanning electron microscope calibration as described in any one of claims 1 to 7.

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