Double-step scanning feature matching type large-range high-precision plane measurement method and system

Abstract

The invention discloses a double-step scanning feature matching type large-range high-precision plane measurement method and system, and the method comprises the steps: carrying out the preliminary scanning of a to-be-measured object at different positions for multiple times, and obtaining the height distribution information of the to-be-measured object and a system scale; performing global high-precision scanning on the to-be-measured object based on the height distribution information of the to-be-measured object to obtain a plurality of high-precision scanning images; the vertical position difference distribution of the surface of the to-be-measured object and the system scale is used as compensation information, and global high-precision measurement data of the to-be-measured object is determined according to the high-precision scanning image; a plurality of positioning marks are arranged on the system scale, the system scale is located between the scanning device and the object to be measured, and the positioning marks are filled with various colors with high contrast. The system cost can be reduced, and the measurement efficiency can be improved.

Description

Technical Field

[0001] This invention belongs to the field of planar measurement technology, specifically relating to a two-step scanning feature matching method and system for large-range, high-precision planar measurement. Background Technology

[0002] Large-area, high-precision planar geometry measurement plays a crucial role in modern industry and scientific research. With continuous technological advancements, the demand for rapid, high-precision planar geometry measurement of large-area samples is increasing. This measurement technology has broad application prospects in semiconductor manufacturing, precision machining, optical component production, and biological sample analysis.

[0003] Taking the semiconductor industry as an example, with the continuous increase in wafer size and the continuous shrinking of integrated circuit manufacturing processes, the precise measurement of the microstructure on the surface of large-size wafers has become particularly important. Similarly, in the manufacturing of large optical components, such as large and complex planar optical structures, it is necessary to ensure extremely high positioning accuracy over a wide range, which poses a severe challenge to measurement technology.

[0004] Furthermore, in the field of biomedical research, large-scale, high-precision measurement techniques can be used to analyze large-area biological samples, such as tissue sections or gene chips, which is of great significance for disease diagnosis and drug development. These applications require not only high global precision but also the ability to rapidly process large amounts of data to improve research efficiency.

[0005] Traditional measurement methods often struggle to balance the goals of large-scale measurement and high precision. High-precision measurement is typically limited to small areas, while large-scale measurement often sacrifices accuracy. Currently popular high-precision, large-scale measurement methods are based on interferometric alignment. This method requires precise focusing, leading to long measurement times, and necessitates additional focusing sensors, resulting in high measurement costs, making it difficult to meet the efficiency requirements of modern industrial production. Summary of the Invention

[0006] This invention provides a two-step scanning feature matching method and system for large-area high-precision planar measurement, which can solve the problems of high cost and low efficiency of current high-precision large-area planar measurement methods.

[0007] In a first aspect, embodiments of the present invention provide a two-step scanning feature matching method for large-range, high-precision planar measurement, the method comprising:

[0008] Multiple preliminary scans of the object under test are performed at different locations to obtain the height distribution information of the object under test and the system scale. The object under test occupies multiple scanning fields of view, and multiple positioning marks are set on the system scale. The system scale is located between the scanning device and the object under test. The positioning marks are filled with multiple high-contrast colors, and each scanning field of view includes at least one positioning mark.

[0009] Based on the height distribution information of the object under test, a global high-precision scan of the object under test is performed to obtain multiple high-precision scan images.

[0010] The vertical position difference distribution between the surface of the object under test and the system scale is used as compensation information. Based on the high-precision scan image, the global high-precision measurement data of the object under test is determined. The high-precision measurement data includes the size and three-dimensional position information of the features on the object under test. The vertical position difference distribution is the distribution of the vertical height difference between the object under test and the system scale. The vertical position difference distribution is determined based on the height distribution information of the object under test and the system scale.

[0011] Secondly, embodiments of the present invention provide a dual-step scanning feature matching type large-range high-precision planar measurement system, including a scanning device, an image processing module, and a system scale;

[0012] The scanning device is used to perform multiple preliminary scans of the object to be tested at different locations, in which the object to be tested occupies multiple scanning fields of view;

[0013] The image processing module is used to determine the height distribution information of the object under test and the system scale based on the preliminary scan image. The system scale is equipped with multiple positioning marks and is located between the scanning device and the object under test. The positioning marks are filled with multiple high-contrast colors, and at least one positioning mark is included in a scanning field of view.

[0014] The scanning device is also used to perform a global high-precision scan of the object under test based on the height distribution information of the object under test to obtain multiple high-precision scan images.

[0015] The image processing module is also used to use the vertical position difference distribution between the surface of the object under test and the system scale as compensation information to determine the global high-precision measurement data of the object under test based on the high-precision scan image. The high-precision measurement data includes the size and three-dimensional coordinate data of each feature on the object under test. The vertical position difference distribution is the distribution of the vertical height difference between the object under test and the system scale, which is determined based on the height distribution information of the object under test and the system scale.

[0016] The beneficial effects of the embodiments of the present invention compared with the prior art are as follows: According to the method provided by the present invention, the scanning device performs a secondary scan based on the height information of the object to be measured obtained from the initial scan, and no precise focusing is required in each scan, which can save the time of precise focusing and improve the measurement efficiency; since no precise focusing is required, the system does not need to set up an additional focusing sensor, which can save the manufacturing cost of the system; high-precision scanning based on the height distribution information of the object to be measured can also improve the measurement accuracy. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a dual-step scanning feature matching type large-range high-precision planar measurement system provided in an embodiment of the present invention;

[0018] Figure 2 A schematic diagram of a system scale provided in an embodiment of the present invention;

[0019] Figure 3 The flowchart illustrates the implementation of a two-step scanning feature matching method for large-range, high-precision planar measurement, as provided in an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram illustrating the relationship between sharpness index and defocus distance, provided by an embodiment of the present invention.

[0021] Figure 5 A schematic diagram of a global coordinate system provided for an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram illustrating the relationship between sharpness index and Z-axis scanning distance, provided by an embodiment of the present invention.

[0023] Figure 7 A schematic diagram of an image coordinate system provided in an embodiment of the present invention;

[0024] Figure 8 This is a schematic diagram illustrating the relationship between the defocus distance and the measured dimension, provided as an embodiment of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0026] Figure 1 The diagram shown illustrates the structure of a dual-step scanning feature-matching large-range high-precision planar measurement system according to an embodiment of the present invention. As an example and not a limitation, system 100 may include a scanning device 110, a system scale 120, and an image processing module 130.

[0027] In one possible implementation, see Figure 1The system 100 may also include modules such as a precision motion stage 140 and an objective lens driver 150 for driving the scanning device 110.

[0028] In one example, see Figure 1 The scanning device 110 may include an objective lens, a tube lens, and a CMOS sensor.

[0029] The objective lens driver 150 can be positioned above the objective lens to drive the movement of the objective lens in the scanning device.

[0030] Optionally, the scanning device 110 may also include an illumination module.

[0031] In one example, see Figure 2 Multiple positioning marks can be set on the system scale 120, and at least one positioning mark is included in each scanning field of view on the system scale 120. The system scale 120 can be located between the object to be measured and the scanning device 110.

[0032] Optionally, the system scale 120 can be made of a transparent material, such as a glass plate, or an opaque material.

[0033] Optionally, the material of the system scale 120 can be the same as that of the object being measured to eliminate the effects of thermal expansion and improve measurement accuracy.

[0034] In one example, the global position of each positioning marker on system scale 120 is known. See also Figure 2 The positioning markers can be filled with a variety of high-contrast colors (two are shown here). This ensures that at least one fill color of the positioning marker can be identified regardless of changes in lighting conditions or background color in the scene; thus increasing the recognition probability of the positioning markers and improving the reliability, adaptability, and accuracy of scanning measurements.

[0035] For example, see Figure 2 The fill color of the pattern inside the positioning mark must not coincide with the outer border of the positioning mark to avoid errors caused by the color of the object being measured being the same as the inner fill color.

[0036] It should be understood that, see Figure 2 This invention does not limit the specific shape of each type of positioning mark or each fill color inside the positioning mark; the shape of the positioning mark can be a circle, a square, a cross, a square, or even a non-connected graphic, etc.

[0037] Optionally, the system 100 may also include a stage 160 for placing the object to be measured. A precision motion stage 140 may be positioned below the stage 160 to move the object to be measured.

[0038] In one possible implementation, the scanning device 110 can perform multiple preliminary scans of the object under test at different positions to obtain multiple preliminary scan images. Then, the image processing module 130 can determine the height distribution information of the object under test and the system scale based on the preliminary scan images. The scanning device 110 then performs a high-precision scan of the object under test based on the height distribution information to obtain multiple high-precision scan images. The image processing module 130 can use the vertical position difference distribution between the surface of the object under test and the system scale 120 as compensation information to determine the global high-precision measurement data of the object under test based on the high-precision scan images.

[0039] For example, the vertical position difference distribution is the distribution of the vertical height difference between the object to be measured and the system scale, which can be determined based on the height distribution information of the object to be measured and the system scale.

[0040] For example, high-precision measurement data may include the size and three-dimensional position information of features on the object to be measured, and global high-precision measurement data may also include the overall size of the object to be measured.

[0041] In one example, during a preliminary scan, the defocus distance of the object under test can be controlled by moving the scanning device vertically using the objective lens driver 150, or by moving the object vertically using the precision stage 140. During a high-precision scan, the defocus distance of the object under test can be controlled by moving the object vertically using the precision stage 140.

[0042] According to the system provided by the present invention, the scanning device performs a second scan based on the height information of the object to be measured obtained from the first scan. Precision focusing is not required in each scan, which can save the time of precision focusing and improve the measurement efficiency. Since precision focusing is not required, the system does not need to be equipped with an additional focusing sensor, which can save the manufacturing cost of the system.

[0043] Figure 3 The diagram shown illustrates a flowchart of a two-step scanning feature-matching method for large-range, high-precision planar measurement according to an embodiment of the present invention. As an example and not a limitation, method 300 may include steps S301-S303, and method 300 can be applied to the aforementioned system 100. The steps are described below.

[0044] S301 performs multiple preliminary scans of the object under test at different locations to obtain the height distribution information of the object under test and the system scale.

[0045] In one possible implementation, the scanning device can move to multiple positions to perform scanning, changing the vertical distance to the object under test at the same position to perform a preliminary scan of the object, obtaining multiple preliminary scan images corresponding to each position. Then, based on... Figure 4The relationship between the image sharpness index and defocus distance of the scanning device shown is illustrated. The vertical height of the object under test and the system scale at the current position is determined based on the sharpness of multiple preliminary scan images corresponding to the object under test and the positioning marker at the current position. By fitting a series of discrete vertical heights of the object under test and the system scale, the height distribution information of the object under test and the system scale can be obtained.

[0046] For example, see Figure 5 The height distribution information of the object under test and the system scale is based on the global coordinate system XYZ.

[0047] In one example, image sharpness analysis can be performed on the preliminary scan image corresponding to the current position based on the relationship between the sharpness index of the scanning device and the defocus distance, to obtain the relationship between the sharpness index and the Z-axis scanning distance (i.e., the vertical distance between the object under test and the scanning device) (see...). Figure 6 This allows us to obtain the vertical height of the positioning marker at the current position and the vertical height of the object under test at the current position.

[0048] For example, the scan results are clearest when the distance between the object being scanned and the scanning device is equal to the working distance of the scanning device.

[0049] In one example, a spline difference fitting algorithm can be used to fit the height distribution information of the object under test and the height distribution information of the system scale.

[0050] S302, based on the height distribution information of the object under test, perform a global high-precision scan of the object under test to obtain multiple high-precision scan images.

[0051] In one possible implementation, the distance between the object under test and the scanning device can be kept equal to the working distance of the scanning device based on the height distribution information of the object under test, so that the scanning device can perform a global high-precision scan of the object under test and obtain multiple high-precision scan images.

[0052] For example, see Figure 2 Compared to the size of the object being measured, the scanning field of view of the scanning device is relatively small. Therefore, it is necessary to move the device multiple times to scan the global information of the object being measured and obtain multiple high-precision scan images.

[0053] In one example, in practical applications, there is inevitably a slight error between the distance between the scanning device and the object under test and the working distance of the scanning device. Therefore, in high-precision scanning, the defocus distance of the object under test can be self-calibrated in real time based on the actual distance between the two and the height distribution information of the object under test; thereby eliminating the influence of errors such as thermal fluctuations and improving the accuracy of the scanning results.

[0054] S303 uses the vertical position difference distribution between the surface of the object under test and the system scale as compensation information to determine the global high-precision measurement data of the object under test based on the high-precision scan image.

[0055] In one possible implementation, the current feature and current positioning marker in the image coordinate system xoy can be determined first based on the high-precision scanned image (see...). Figure 7 The relative planar position information of the positioning mark is obtained by using the surface of the object under test as a reference during high-precision scanning, and because the positioning mark and the object under test are not on the same plane. Therefore, the clarity of the positioning mark in the high-precision scan image is low, and the relative planar position information of the current positioning mark has a certain error. The relative planar position information of the current positioning mark can be compensated for by the vertical difference distribution between the positioning mark and the object under test to obtain the high-precision planar position information of the current positioning mark. Then, based on the high-precision planar position information of the current positioning mark, the known two-dimensional global position of the current positioning mark, and the relative planar information of the current feature, the two-dimensional global position information of the current feature is determined. Finally, the global information of the current feature within each field of view and the height distribution information of the object under test are stitched together to obtain the global high-precision measurement data of the object under test.

[0056] For example, the field of view corresponding to the high-progress scan image currently being processed is the current field of view. The current positioning marker is the positioning marker of the system scale within the current field of view, and the current feature is the feature of the object to be measured within the current field of view.

[0057] In one example, the relationship between the defocus distance of the scanning device and the size being measured can be used (see...). Figure 8 The high-precision planar position information of the current positioning mark is obtained by compensating for the relative planar position information of the current positioning mark based on the vertical position difference distribution between the object under test and the system scale.

[0058] According to the method provided by the present invention, the scanning device performs a second scan based on the height information of the object to be measured obtained from the first scan. Precision focusing is not required in each scan, which can save the time of precision focusing and improve the measurement efficiency. Since precision focusing is not required, the system does not need to set up an additional focusing sensor, which can save the manufacturing cost of the system. High-precision scanning based on the height distribution information of the object to be measured can also improve the measurement accuracy.

[0059] Compared with traditional interferometric alignment measurement methods where the scanning device stops after scanning at each position to calculate the two-dimensional distance between two adjacent scanning positions, this invention calculates high-precision global measurement data of the object under test based on the known global position information of the positioning markers during image processing in parallel with the scanning process. It can achieve continuous and efficient planar measurement of the object under test, realize "flying shooting" of the object under test, and is suitable for high-speed, large-range, and high-precision measurement scenarios.

[0060] Optionally, see Figure 5 If a location marker obscures the key features of the object being measured, for example... Figure 5 If the positioning mark A4 obscures the key feature B1, then after slightly moving the system scale to expose the obscured key feature, proceed with the following steps S304-S306.

[0061] S304, based on the moved system scale, perform a local scan of the region where the unknown local features are located, and obtain high-precision measurement data of the unknown local features and high-precision measurement data of at least two known local features after updates.

[0062] For example, if the system scale moves but the object under test does not move, the height distribution information of the object under test determined in step S301 remains valid. Based on the height distribution information of the object under test, a high-precision local scan can be performed on the region containing the unknown local features to obtain a high-precision local scan image. Then, based on a method similar to that in step S303, the high-precision measurement data updated with the unknown local features and at least two known local features is determined.

[0063] For example, a local feature of location could be a feature that was occluded by a positioning marker before the system scale moved. A known local feature could be a feature that was not occluded by a positioning marker before the system scale moved.

[0064] S305, determine the movement parameters of the system scale based on high-precision measurement data updated from at least two known local features and historical high-precision measurement data.

[0065] For example, since the high-precision planar position information of the object under test is calculated based on the global position of the positioning marker, even if the object under test does not actually move after the system scale moves, its two-dimensional coordinate values ​​in the global coordinate system will change. The movement parameters of the system scale, such as the translation and rotation of the system scale, can be determined based on the high-precision measurement data updated with known local features and historical high-precision measurement data.

[0066] S306: Based on the movement parameters, high-precision measurement data of unknown local features and historical high-precision measurement data of all known local features are stitched together to obtain high-precision measurement data of all features of the object under test.

[0067] Instead of controlling the system to precisely move the system scale according to set parameters, the hardware requirements of the system can be simplified, the robustness of the system can be improved, and the system cost and complexity can be reduced by calculating the movement parameters of the system scale based on known local features.

[0068] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0069] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

Claims

1. A two-step scanning feature matching method for large-range, high-precision planar measurement, characterized in that, include: Multiple preliminary scans are performed on the object to be tested at different locations to obtain the height distribution information of the object to be tested and the system scale. The object to be tested occupies multiple scanning fields of view, and multiple positioning marks are set on the system scale. The system scale is located between the scanning device and the object to be tested. The positioning marks are filled with multiple high-contrast colors, and at least one positioning mark is included in each scanning field of view. Based on the height distribution information of the object under test, a global high-precision scan of the object under test is performed to obtain multiple high-precision scan images; The vertical position difference distribution between the surface of the object under test and the system scale is used as compensation information. Based on the high-precision scan image, the global high-precision measurement data of the object under test is determined. The high-precision measurement data includes the size and three-dimensional position information of the features on the object under test. The vertical position difference distribution is the distribution of the vertical height difference between the object under test and the system scale, and the vertical position difference distribution is determined based on the height distribution information of the object under test and the system scale.

2. The method according to claim 1, characterized in that, The process involves performing multiple preliminary scans of the object under test at different locations to obtain height distribution information of the object under test and the system scale, including: By changing the vertical distance between the object under test and the scanning device at different positions, a preliminary scan of the object under test is performed to obtain multiple preliminary scan images corresponding to each position; Based on the relationship between the resolution index and the defocus distance of the scanning device, and according to the resolution of the object under test and the positioning mark in multiple preliminary scan images corresponding to the current position, the vertical height of the object under test and the system scale at the current position is determined. The height distribution information of the object under test and the height distribution information of the system scale are obtained by fitting the vertical height of the object under test at different positions and the vertical height of the system scale at different positions, respectively.

3. The method according to claim 1, characterized in that, The method involves performing a global high-precision scan of the object under test based on its height distribution information to obtain multiple high-precision scan images, including: Based on the height distribution information of the object under test, the distance between the object under test and the scanning device is kept constant at the working distance of the scanning device, and a global high-precision scan is performed on the object under test to obtain multiple high-precision scan images.

4. The method according to claim 3, characterized in that, When performing the high-precision scan, the method further includes: The defocus distance of the object under test is self-calibrated based on the height distribution information of the object under test and the actual distance between the object under test and the scanning device.

5. The method according to claim 3, characterized in that, The step of using the vertical position difference distribution between the surface of the object under test and the system scale as compensation information, and determining the global high-precision measurement data of the object under test based on the high-precision scan image, includes: The relative planar position information of the current positioning mark and the current feature are determined based on the high-precision scan image obtained by scanning the current field of view, wherein the current positioning mark is within the current field of view, and the current feature is the feature of the object to be measured within the current field of view; The high-precision planar position information of the current positioning mark is obtained by compensating the relative planar position information of the current positioning mark based on the vertical position difference distribution; Based on the high-precision planar position information, the global position of the current positioning marker, and the relative planar position information of the current feature, the global position information of the current feature is determined; By stitching together the global position information of the current feature within each field of view and the height distribution information of the object under test, high-precision global measurement data of the object under test is obtained.

6. The method according to claim 5, characterized in that, The step of compensating the relative planar position information based on the vertical position difference distribution to obtain the high-precision planar position information of the current positioning marker includes: Based on the relationship between the defocus distance of the scanning device and the measured size, the high-precision planar position information of the current positioning mark is obtained by compensating the relative planar position information of the current positioning mark according to the vertical position difference distribution.

7. The method according to any one of claims 1-6, characterized in that, If a positioning marker obscures a key feature of the object under test, the method further includes: Based on the moved system scale, a local scan is performed on the area where the unknown local feature is located to obtain high-precision measurement data of the unknown local feature and high-precision measurement data of at least two known local features after updates. The object to be measured includes the unknown local feature and the at least two known local features. The unknown local feature was occluded by the positioning mark in the previous scan measurement. The movement parameters of the system scale are determined based on the high-precision measurement data updated from the at least two known local features and the historical high-precision measurement data. By stitching together the high-precision measurement data of the unknown local features and the historical high-precision measurement data of all known local features obtained in the previous scan measurement according to the movement parameters, high-precision measurement data of all features of the object under test can be obtained.

8. The method according to claim 1, characterized in that, The material of the system scale is the same as that of the object being measured.

9. A dual-step scanning feature-matching large-range high-precision planar measurement system, characterized in that, Includes scanning device, image processing module and system scale; The scanning device is used to perform multiple preliminary scans of the object to be tested at different locations, wherein the object to be tested occupies multiple scanning fields of view; The image processing module is used to determine the height distribution information of the object under test and the system scale based on the preliminary scan image. The system scale is provided with multiple positioning marks. The system scale is located between the scanning device and the object under test. The positioning marks are filled with multiple high-contrast colors. At least one positioning mark is included in a scanning field of view. The scanning device is also used to perform a global high-precision scan of the object under test based on the height distribution information of the object under test to obtain multiple high-precision scan images. The image processing module is further configured to use the vertical position difference distribution between the surface of the object under test and the system scale as compensation information, and determine the global high-precision measurement data of the object under test based on the high-precision scan image. The high-precision measurement data includes the size and three-dimensional coordinate data of each feature on the object under test. The vertical position difference distribution is the distribution of the vertical height difference between the object under test and the system scale, and the vertical position difference distribution is determined based on the height distribution information of the object under test and the system scale.

10. The system according to claim 9, characterized in that, During the preliminary scan, the defocus distance of the object under test is controlled by the objective lens driver or the precision motion stage. During the high-precision scan, the defocus distance of the object under test is controlled by the precision motion stage.

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