A fusion calibration method and system for semiconductor measurement equipment

Abstract

The application discloses a fusion calibration method for a semiconductor measuring device, comprising the following steps: S1: performing optical navigator calibration to establish a first conversion relationship between a CCD camera image coordinate system and a workpiece table coordinate system; S2: performing SEM image calibration to establish a second conversion relationship between a SEM image coordinate system and the workpiece table coordinate system; S3: based on the first conversion matrix generated in S1 and the second conversion matrix generated in S2, realizing fusion calibration of the CCD camera image coordinate system, the SEM image coordinate system and the workpiece table coordinate system; wherein the fusion calibration is used for distinguishing repeated patterns through initial positioning of a large field of view of a CCD camera in semiconductor wafer measurement, and for precise positioning through high resolution of a SEM image, so as to achieve nm-level precision. The application has the advantages of significantly improving the precision, stability and efficiency of the semiconductor measuring device.

Description

Technical Field

[0001] This invention relates primarily to the field of semiconductor technology, and more specifically to a fusion calibration method and system for semiconductor measurement equipment. Background Technology

[0002] The critical dimensions of semiconductor chips have evolved from 125µm to 50nm and below. This reduction in critical dimensions allows for the number of devices on each chip to reach millions or even more. As the size decreases, it becomes more difficult to locate potential defects. Current CDSEM (Catalytic Reduction Microscopy) methods acquire scanning electron microscope images and use image algorithms to measure critical dimensions in order to find potential defects in the pattern (including various types of linewidths, circular holes, fillets, ellipses, gaps, etc.).

[0003] Electron beam metrology equipment, such as scanning electron microscopes (CDSEM), is widely used in semiconductor manufacturing due to its advantages of high resolution and high precision. When inspecting the microstructure of semiconductor wafers, electron beam metrology equipment needs to accurately identify and measure various pattern features to ensure chip performance and yield. One important indicator is repeatability, which is reflected in the dimensional deviation of multiple measurements of the same pattern feature. If multiple measurements fluctuate within a very small error range, it indicates that the equipment has good repeatability in terms of dimensional measurement accuracy.

[0004] The stability and accuracy of positioning directly affect the stability of multiple measurements. A method using a CCD camera for initial positioning and SEM images for precise positioning is proposed. Initial positioning with the CCD camera ensures stability, while precise positioning with SEM images ensures accuracy.

[0005] Currently, there are many repetitive patterns on 8 / 12-inch wafers. To distinguish these repetitive patterns, the advantage of a CCD camera's wide field of view is utilized to quickly locate the unique pattern / marker within that wide field of view, achieving stable identification. However, since a CCD's wide field of view only achieves micrometer-level resolution, the accuracy is not particularly high. Combining this with precise positioning using SEM images at higher magnification can achieve nanometer-level resolution, enabling rapid and accurate positioning of the pattern to be measured. The fusion positioning of CCD camera and SEM images requires high calibration accuracy, and currently, there is no calibration method that meets this requirement. Summary of the Invention

[0006] To address the technical problems existing in the prior art, the present invention provides a fusion calibration method and system for semiconductor measurement equipment that significantly improves the accuracy, stability and efficiency of semiconductor measurement equipment.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A fusion calibration method for semiconductor measurement equipment includes the following steps: S1: Perform optical navigator calibration to establish the first transformation relationship between the CCD camera image coordinate system and the workpiece stage coordinate system; wherein, S1 includes: S101: Take the first picture of the area containing n≥3 markers using a CCD camera, and obtain the coordinate point set (x1, y1) in the initial image coordinate system and the corresponding coordinate point set in the workpiece stage coordinate system. ,in , The origin of the image coordinate system is used as the reference point. S102: Move the workpiece stage i times, with each movement covering a distance of... And calculate the deviation distance in the image coordinate system using a matching localization algorithm. Thus, the coordinates of the image system for the i-th photograph are obtained. and workpiece stage coordinate system coordinates Generate n pairs of point data; i = 2 to n; S103: Based on n pairs of point data, the least squares method is used to perform fitting calculations to obtain the first transformation matrix; S2: Perform SEM image calibration to establish a second transformation relationship between the SEM image coordinate system and the workpiece stage coordinate system; wherein, S2 includes: S201: Take the first image of the region containing n≥3 markers using SEM imaging to obtain the coordinate point set (x1, y1) in the initial image coordinate system and the corresponding coordinate point set in the workpiece stage coordinate system. ,in , ; S202: Move the workpiece stage i times, with each movement covering a distance of... And calculate the deviation distance in the image coordinate system using a matching localization algorithm. Thus, the coordinates of the image system for the i-th photograph are obtained. and workpiece stage coordinate system coordinates Generate n pairs of point data; S203: Based on n pairs of point data, the least squares method is used to perform fitting calculations to obtain the second transformation matrix; S3: Based on the first transformation matrix generated by S1 and the second transformation matrix generated by S2, the fusion calibration of the CCD camera image coordinate system, the SEM image coordinate system and the workpiece stage coordinate system is realized; wherein, the fusion calibration is used in semiconductor wafer measurement to perform initial positioning through the large field of view of the CCD camera to distinguish repeating patterns, and to perform fine positioning through the high resolution of the SEM image to achieve nm-level accuracy.

[0008] Preferably, in steps S103 and S203, the coordinates of the image coordinate system and the workpiece stage coordinate system corresponding to each mark center are set to A(X,Y) and B(△X,△Y), respectively. The fitting process adopts a high-order nonlinear model, including linear terms, quadratic nonlinear terms, and cubic nonlinear terms, specifically:

[0009] Where a0-a9 and b0-b9 are model fitting coefficients.

[0010] Preferably, the fitting calculation includes a global fitting strategy: high-order coefficients are used for fitting the large field of view of the CCD camera, and low-order coefficients are used for fitting the small scanning range of the SEM image, in order to further optimize the calibration accuracy.

[0011] Preferably, the marker includes any one of a circular marker, a cross marker, a rectangular marker, or an image pattern; wherein the selection of the marker type is adapted to the pattern features of the semiconductor wafer.

[0012] Preferably, the fusion calibration is applied to a CDSEM device for measuring critical dimensions of semiconductor wafers, including defect detection of linewidth, circular holes, rounded corners, ellipses, or gaps.

[0013] The present invention also discloses a computer program product, comprising a computer program that, when executed by a processor, performs the steps of the method described above.

[0014] The present invention further discloses a computer-readable storage medium having a computer program stored thereon, the computer program executing the steps of the method described above when run by a processor.

[0015] The present invention also discloses a fusion calibration system for semiconductor measurement equipment, including an interconnected memory and a processor, wherein the memory stores a computer program that, when run by the processor, executes the steps of the method described above.

[0016] Compared with the prior art, the advantages of the present invention are as follows: The fusion calibration method of this invention significantly improves the accuracy, stability, and efficiency of semiconductor measurement equipment by combining the large-field-of-view initial positioning of an optical navigator / CCD camera with the high-resolution fine positioning of scanning electron microscope (SEM) images and employing a high-order nonlinear fitting strategy. Specifically: First, the CCD camera rapidly identifies unique patterns (such as repeating patterns) on the wafer within a μm-level field of view, achieving stable initial positioning and avoiding positioning deviations caused by limited field of view in existing technologies. Second, precise positioning is achieved using SEM images at nm-level magnification, and high-order nonlinear fitting models (such as linear + quadratic + cubic terms) compensate for image distortion, thus improving the calibration precision. The accuracy has been improved from the μm level to the nm level, effectively solving the problem of the lack of high-precision calibration methods in existing technologies. Furthermore, this method introduces a global optimization strategy, using high-order coefficients for fitting within the large field of view of the CCD and low-order coefficients for fitting within the small field of view of the SEM, further reducing cumulative errors and ensuring the robustness of the transformation matrix. Ultimately, this fusion calibration not only significantly improves the repeatability and accuracy of critical dimension measurements (such as linewidth and circular holes) (deviation fluctuations are controlled within a very small range), but also reduces the defect detection rate, improves the overall yield of 8 / 12-inch wafers, and optimizes the measurement process (such as reducing positioning time), supporting the efficient development of semiconductor manufacturing towards critical dimensions of 50nm and below. Overall, this method, through innovative coordinate system unification and fitting optimization, provides reliable nm-level accuracy assurance for CDSEM equipment, directly improving chip performance and manufacturing efficiency. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the optical navigator / CCD camera calibration of the present invention.

[0018] Figure 2 This is a schematic diagram of the first photograph taken during the calibration process of the optical navigator / CCD camera in this invention.

[0019] Figure 3 This is a schematic diagram of the 2nd...nth photo taken during the calibration process of the optical navigator / CCD camera in this invention.

[0020] Figure 4 This is a schematic diagram of the global fitting process during the calibration of the optical navigator / CCD camera in this invention.

[0021] Figure 5 This is a schematic diagram of SEM image calibration in this invention.

[0022] Figure 6 This is a schematic diagram of the first photograph taken during the SEM image calibration process in this invention.

[0023] Figure 7 This is a schematic diagram of the 2nd...nth image capture during the SEM image calibration process in this invention.

[0024] Figure 8 This is a schematic diagram of global fitting during the SEM image calibration process in this invention.

[0025] Figure 9 This is a flowchart of an embodiment of the fusion calibration method of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 9 As shown, the fusion calibration method for semiconductor measurement equipment provided in this embodiment of the invention includes the following steps: S1: As Figure 1 As shown, optical navigator calibration is performed to establish the first transformation relationship between the CCD camera image coordinate system and the workpiece stage coordinate system, and to perform calibration from the image coordinate system to the workpiece stage coordinate system. The transformation matrix is ​​directly calculated using the known image coordinates of n ≥ 3 points and the corresponding workpiece stage coordinates (x, y values ​​output by the laser interferometer). Specific steps include: S101: As Figure 2 As shown, with the image coordinate system position as the reference origin, the CCD camera takes the first picture of the area containing n ≥ 3 markers (such as circular markers), ensuring that the camera's field of view can cover all markers. The coordinates (x1, y1) of the markers in the image coordinate system and the corresponding coordinates in the workpiece stage coordinate system are recorded sequentially. At this point, one point-to-point pair has been completed.

[0028] S102: As Figure 3 As shown, the workpiece stage is moved i times (i=2 to n), and the distance moved each time is... The offset distance in the image coordinate system is calculated using a matching localization algorithm. Thus, the coordinates of the image system for the i-th photograph are obtained. and workpiece stage coordinate system coordinates Let i = 2, 3...9, and move the workpiece stage cyclically to obtain n pairs of point data.

[0029] S103: Fitting Solution Based on n pairs of point data, the least squares method is used for fitting calculation to obtain the first transformation matrix; the fitting process adopts a high-order nonlinear model to compensate for image distortion, and the high-order nonlinear model includes linear terms, quadratic nonlinear terms and cubic nonlinear terms. like Figure 4As shown, assume that the coordinates of each mark center in the image coordinate system and the workpiece stage coordinate system are A(X,Y) and B(△X,△Y), respectively. The fitting solution can be obtained through linear and nonlinear fitting using the following formula: Linear distortion

[0030] pseudolinear

[0031] Linear + 2nd order nonlinear

[0032] Linear + 2nd order nonlinear + 3rd order nonlinear

[0033] Because CCD images have a large field of view, higher coefficients are selected for fitting within the global range, while lower coefficients are selected for fitting within the small green area of ​​the SEM image, further improving the global calibration accuracy. For example, the Hitachi CDSEMCG4000 device has a field of view (FOV) of 1298.077µm at 104x magnification and 0.75µm at 180,000x magnification. Lower coefficients are selected within a field of view of 0.3~1µm; higher coefficients are selected within a field of view of 500~1500µm.

[0034] S2: As Figure 5 As shown, SEM image calibration mainly involves calibrating the SEM image coordinate system to the workpiece stage coordinate system, establishing the transformation relationship between SEM pixel coordinates and workpiece stage world coordinates. The transformation matrix is ​​directly calculated using the known image coordinates of n≥3 points and the corresponding workpiece stage coordinates (x, y values ​​output by the laser interferometer). Specific steps include: S201: Take the first image of the area containing n≥3 markers using SEM imaging. Using the image coordinate system position as the reference origin, ensure that the camera's field of view covers all points. Sequentially record the coordinates (x1, y1) of the circular markers in the image coordinate system and the corresponding coordinates in the workpiece stage coordinate system. At this point, one point-to-point pair has been completed, such as... Figure 6 As shown.

[0035] S202: Move the workpiece stage i times (i=2 to n), the distance of the i-th movement of the workpiece stage is... The deviation distance in the image coordinate system is calculated using a matching localization algorithm. Thus, the coordinates of the image system for the i-th photograph are obtained. and workpiece stage coordinate system coordinates By cyclically moving the workpiece stage, n pairs of point data can be obtained, such as... Figure 7 As shown.

[0036] S203: Based on n pairs of point data, the least squares method is used to perform fitting calculations to obtain the second transformation matrix; the fitting process adopts a high-order nonlinear model, including linear terms, quadratic nonlinear terms, and cubic nonlinear terms; like Figure 8 As shown, assume that the coordinates of each mark center in the image coordinate system and the workpiece stage coordinate system are A(X,Y) and B(△X,△Y), respectively. The fitting solution can be obtained through linear and nonlinear fitting using the following formula: Linear distortion

[0037] pseudolinear

[0038] Linear + 2nd order nonlinear

[0039] Linear + 2nd order nonlinear + 3rd order nonlinear

[0040] Where a0-a9 and b0-b9 are model fitting coefficients.

[0041] Since the SEM scanning range ranges from hundreds of nm to hundreds of μm, the field of view of the image varies greatly. A higher coefficient is selected for fitting in the global range, and a lower coefficient is selected for fitting in the small green area to further improve the global calibration accuracy.

[0042] S3: Based on the first transformation matrix generated by S1 and the second transformation matrix generated by S2, the fusion calibration of the CCD camera image coordinate system, the SEM image coordinate system and the workpiece stage coordinate system is realized; wherein, the fusion calibration is used in semiconductor wafer measurement to perform initial positioning through the large field of view of the CCD camera to distinguish repeating patterns, and to perform fine positioning through the high resolution of the SEM image to achieve nm-level accuracy.

[0043] In the aforementioned optical navigator / CCD camera calibration method, the circular marker is just an example; various types of markers can be used, such as circular, cross, rectangular, or image patterns. The fitting method can be fourth-order nonlinear or higher nonlinear, as well as other combined optimization methods. Similarly, in the SEM image calibration method, the circular marker is just an example; various types of markers can be used, such as circular, cross, rectangular, or image patterns. The fitting method can be fourth-order nonlinear or higher nonlinear, as well as other combined optimization methods. For example, a pseudo-linear model can be used when computational resources are limited.

[0044] The fusion calibration method of this invention significantly improves the accuracy, stability, and efficiency of semiconductor measurement equipment by combining the large-field-of-view initial positioning of an optical navigator / CCD camera with the high-resolution fine positioning of scanning electron microscope (SEM) images and employing a high-order nonlinear fitting strategy. Specifically: First, the CCD camera rapidly identifies unique patterns (such as repeating patterns) on the wafer within a μm-level field of view, achieving stable initial positioning and avoiding positioning deviations caused by limited field of view in existing technologies. Second, precise positioning is achieved using SEM images at nm-level magnification, and high-order nonlinear fitting models (such as linear + quadratic + cubic terms) compensate for image distortion, thus improving the calibration precision. The accuracy has been improved from the μm level to the nm level, effectively solving the problem of the lack of high-precision calibration methods in existing technologies. Furthermore, this method introduces a global optimization strategy, using high-order coefficients for fitting within the large field of view of the CCD and low-order coefficients for fitting within the small field of view of the SEM, further reducing cumulative errors and ensuring the robustness of the transformation matrix. Ultimately, this fusion calibration not only significantly improves the repeatability and accuracy of critical dimension measurements (such as linewidth and circular holes) (deviation fluctuations are controlled within a very small range), but also reduces the defect detection rate, improves the overall yield of 8 / 12-inch wafers, and optimizes the measurement process (such as reducing positioning time), supporting the efficient development of semiconductor manufacturing towards critical dimensions of 50nm and below. Overall, this method, through innovative coordinate system unification and fitting optimization, provides reliable nm-level accuracy assurance for CDSEM equipment, directly improving chip performance and manufacturing efficiency.

[0045] Definitions: CDSEM (Critical Dimension Scanning Electron Microscope): a scanning electron microscope for critical dimensions.

[0046] SEM (Scanning Electron Microscope): Scanning electron microscope.

[0047] This invention also discloses a computer program product, comprising a computer program that, when run by a processor, performs the steps of the method described above. This invention further discloses a computer-readable storage medium storing a computer program that, when run by a processor, performs the steps of the method described above. This invention also discloses a fusion calibration system for semiconductor measurement equipment, comprising an interconnected memory and a processor, wherein the memory stores a computer program that, when run by a processor, performs the steps of the method described above. The products, media, and systems of this invention, corresponding to the methods described above, also possess the advantages described above.

[0048] The present invention can implement all or part of the processes in the methods of the above embodiments, or it can be implemented by hardware related to computer program instructions. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the above method embodiments. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or some intermediate form. The computer-readable storage medium includes: any entity or device capable of carrying computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. The memory is used to store computer programs and / or modules. The processor implements various functions by running or executing the computer programs and / or modules stored in the memory, and by calling data stored in the memory. The memory may include high-speed random access memory, as well as non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital (SD) cards, flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0049] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A fusion calibration method for semiconductor measurement equipment, characterized in that, Includes the following steps: S1: Perform optical navigator calibration to establish the first transformation relationship between the CCD camera image coordinate system and the workpiece stage coordinate system; wherein, S1 includes: S101: Take the first picture of the area containing n≥3 markers using a CCD camera, and obtain the coordinate point set (x1, y1) in the initial image coordinate system and the corresponding coordinate point set in the workpiece stage coordinate system. ,in , The origin of the image coordinate system is used as the reference point. S102: Move the workpiece stage i times, with each movement covering a distance of... And calculate the deviation distance in the image coordinate system using a matching localization algorithm. Thus, the coordinates of the image system for the i-th photograph are obtained. and workpiece stage coordinate system coordinates Generate n pairs of point data; i = 2 to n; S103: Based on n pairs of point data, the least squares method is used to perform fitting calculations to obtain the first transformation matrix; S2: Perform SEM image calibration to establish a second transformation relationship between the SEM image coordinate system and the workpiece stage coordinate system; wherein, S2 includes: S201: Take the first image of the region containing n≥3 markers using SEM imaging to obtain the coordinate point set (x1, y1) in the initial image coordinate system and the corresponding coordinate point set in the workpiece stage coordinate system. ,in , ; S202: Move the workpiece stage i times, with each movement covering a distance of... And calculate the deviation distance in the image coordinate system using a matching localization algorithm. Thus, the coordinates of the image system for the i-th photograph are obtained. and workpiece stage coordinate system coordinates Generate n pairs of point data; S203: Based on n pairs of point data, the least squares method is used to perform fitting calculations to obtain the second transformation matrix; S3: Based on the first transformation matrix generated by S1 and the second transformation matrix generated by S2, the fusion calibration of the CCD camera image coordinate system, the SEM image coordinate system and the workpiece stage coordinate system is realized; wherein, the fusion calibration is used in semiconductor wafer measurement to perform initial positioning through the large field of view of the CCD camera to distinguish repeating patterns, and to perform fine positioning through the high resolution of the SEM image to achieve nm-level accuracy.

2. The fusion calibration method for semiconductor measurement equipment according to claim 1, characterized in that, In steps S103 and S203, the coordinates of the image coordinate system and the workpiece stage coordinate system corresponding to each mark center are set to A(X,Y) and B(△X,△Y), respectively. The fitting process adopts a high-order nonlinear model, including linear terms, quadratic nonlinear terms, and cubic nonlinear terms, specifically: Where a0-a9 and b0-b9 are model fitting coefficients.

3. The fusion calibration method for semiconductor measurement equipment according to claim 2, characterized in that, The fitting calculation includes a global fitting strategy: high-order coefficients are used for fitting the large field of view of the CCD camera, and low-order coefficients are used for fitting the small scanning range of the SEM image, in order to further optimize the calibration accuracy.

4. The fusion calibration method for semiconductor measurement equipment according to claim 1, 2, or 3, characterized in that, The markers include any one of circular markers, cross markers, rectangular markers, or image patterns; wherein the selection of the marker type is adapted to the pattern features of the semiconductor wafer.

5. The fusion calibration method for semiconductor measurement equipment according to claim 1, 2, or 3, characterized in that, The fusion calibration is applied to CDSEM equipment for measuring critical dimensions of semiconductor wafers, including defect detection of linewidth, circular holes, fillets, ellipses, or gaps.

6. A computer program product, comprising a computer program, characterized in that, The computer program is executed by the processor to perform the steps of the method as described in any one of claims 1-5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, The computer program, when run by a processor, performs the steps of the method as described in any one of claims 1-5.

8. A fusion calibration system for semiconductor measurement equipment, comprising an interconnected memory and a processor, wherein the memory stores a computer program, characterized in that, The computer program, when run by a processor, performs the steps of the method as described in any one of claims 1-5.

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