Calibration wafer and method for determining metrology positioning bias

Abstract

A kind of calibration wafer and method for determining metrology positioning deviation, comprising: providing calibration wafer, which is provided with metrology monitor pad capable of being used for optical ellipsometric measurement, the film layer thickness of metrology monitor pad linearly changes in at least one preset direction;Calibration wafer is loaded to wafer bearing component, and linear scanning is carried out to target metrology monitor pad along preset direction using optical ellipsometric measurement equipment, to obtain the fitting regression line of film thickness with the change of scanning position, the theoretical center coordinates of target metrology monitor pad are obtained by fitting regression line;Charge-coupled device camera field of view center is positioned to theoretical center coordinates, and the actual thickness of film at theoretical center coordinates of target metrology monitor pad is obtained, the actual center coordinates corresponding to actual thickness of film are obtained by substituting actual thickness of film into fitting regression line, and the actual center coordinates are obtained based on actual center coordinates and theoretical center coordinates to obtain metrology positioning deviation.The method can significantly improve the calibration accuracy and reliability of optical ellipsometric measurement system.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and more specifically to a method for calibrating a wafer and determining measurement positioning deviations. Background Technology

[0002] Spectroscopic ellipsometry (SE) is a non-contact, non-destructive optical characterization technique based on the interaction between polarized light and a sample. It is widely used for the measurement of thin film thickness (THK) and optical critical dimension (OCD), with core applications concentrated in precision manufacturing fields such as semiconductors and optoelectronic materials.

[0003] The sample stage is the core component of the SE equipment that carries the wafer / sample and achieves precise positioning. It usually has XY-θ-Z multi-axis motion capability and is used to accurately move the THK / OCD pad on the dicing channel (i.e., the narrow area on the wafer that separates adjacent dies, where a THK / OCD measurement monitoring pad is reserved) under the measurement spot.

[0004] The stage movement accuracy and spot offset (the offset between the measured spot and the center of the charge-coupled device (CCD)) are important parameters of optical ellipsometric measurement equipment, both of which affect the actual measurement position and the final result. As manufacturing processes and nodes continue to advance, the size of the THK / OCD pad on the dicing path tends to decrease, and the requirements for the stage movement accuracy and spot position stability of optical ellipsometric measurement equipment are gradually increasing.

[0005] The existing method for determining the stage movement accuracy involves directly photographing the standard pattern on a graphic film and then calculating the pattern's position in the field of view. However, this method is heavily influenced by image quality and has relatively poor accuracy. Another method for determining the spot drift involves measuring the changes in parameters such as THK, Normalized Global Optical Fit (NGOF), and Mean Squared Error (MSE) in the pad area using line scan mode. However, this method is prone to boundary judgments and introduces some error. Therefore, the measurement results from the existing methods are not precise enough. Furthermore, the existing methods cannot simultaneously measure both the stage movement accuracy and the spot drift. Summary of the Invention

[0006] This application is made to address the aforementioned problems. According to a first aspect of this application, a calibration wafer is provided, wherein the calibration wafer is provided with a measurement monitoring pad capable of optical ellipsometric measurement, and the film thickness of the measurement monitoring pad varies linearly in at least one preset direction.

[0007] In one embodiment of this application, the calibration wafer has multiple patterned regions arranged in a preset direction, and each patterned region has two measurement monitoring pads, namely a first measurement monitoring pad and a second measurement monitoring pad. The preset direction includes a first preset direction and a second preset direction, wherein: the film thickness of the first measurement monitoring pad changes linearly in the first preset direction, and the first preset direction is parallel to the horizontal direction of the optical elliptic measurement system coordinate system; the film thickness of the second measurement monitoring pad changes linearly in the second preset direction, and the second preset direction is parallel to the vertical direction of the optical elliptic measurement system coordinate system.

[0008] In one embodiment of this application, the calibration wafer is provided with a plurality of patterned areas, and each patterned area is provided with a measurement monitoring pad. The preset direction is parallel to the notch direction of the calibration wafer or perpendicular to the notch direction of the calibration wafer.

[0009] In one embodiment of this application, the film thickness and thickness variation of the monitoring pads in different pattern regions in the preset direction are exactly the same; or, the film thickness of the monitoring pads in different pattern regions in the preset direction are different from each other.

[0010] In one embodiment of this application, the calibration wafer is provided with a plurality of patterned areas, each of the patterned areas is provided with a measurement monitoring pad, and the preset direction is the radial direction of the calibration wafer.

[0011] In one embodiment of this application, the measurement monitoring pad is a single-film structure.

[0012] According to a second aspect of this application, a method for determining a measurement positioning deviation is provided, the method comprising: providing a calibration wafer, wherein the calibration wafer is provided with a measurement monitoring pad capable of optical ellipsometric measurement, the film thickness of the measurement monitoring pad changing linearly in at least one preset direction; loading the calibration wafer onto a wafer carrier component, and using the optical ellipsometric measurement device to perform a line scan on a target measurement monitoring pad along the preset direction to obtain a fitted regression line of film thickness changing with scanning position, and obtaining the center thickness of the target measurement monitoring pad and the relationship between thickness and distance through the fitted regression line; positioning the field of view center of the CCD camera of the optical ellipsometric measurement device at the center coordinates of the measurement monitoring pad in the field of view, obtaining the actual film thickness at the theoretical center coordinates of the target measurement monitoring pad, and substituting the actual film thickness into the fitted regression line to obtain the deviation between the actual center coordinates and the theoretical center coordinates corresponding to the actual film thickness.

[0013] In one embodiment of this application, the measurement positioning deviation includes the movement offset of the wafer carrier component. Obtaining the movement offset of the wafer carrier component includes: controlling the wafer carrier component to move the target measurement monitoring pad so that the CCD camera's field of view center is positioned at the theoretical center coordinates; using the optical ellipsometry measurement device to measure the actual thickness of the thin film at the theoretical center coordinates to obtain a first actual thickness of the thin film at the theoretical center coordinates; substituting the first actual thickness of the thin film into the fitted regression line to obtain a first actual center coordinate corresponding to the first actual thickness of the thin film; and obtaining the movement offset of the wafer carrier component based on the first actual center coordinate and the theoretical center coordinate.

[0014] In one embodiment of this application, the measurement positioning deviation includes the offset between the CCD camera field of view center and the spot center of the optical ellipsometric measuring device. Obtaining the offset between the CCD camera field of view center and the spot center includes: positioning the CCD camera field of view center of the optical ellipsometric measuring device to the theoretical center coordinates; measuring the film thickness at the theoretical center coordinates using the optical ellipsometric measuring device to obtain the second actual film thickness at the theoretical center coordinates; substituting the second actual film thickness into the fitted regression line to obtain the second actual center coordinates corresponding to the second actual film thickness; and obtaining the offset between the CCD camera field of view center and the spot center based on the second actual center coordinates and the theoretical center coordinates.

[0015] In one embodiment of this application, the calibration wafer is provided with a plurality of patterned regions in a preset direction, and each patterned region is provided with two target measurement monitoring pads, namely a first target measurement monitoring pad and a second target measurement monitoring pad. The preset direction includes a first preset direction and a second preset direction, wherein: the film thickness of the first target measurement monitoring pad changes linearly in the first preset direction, and the first preset direction is parallel to the horizontal direction of the system coordinate system of optical ellipsometric measurement; the film thickness of the second target measurement monitoring pad changes linearly in the second preset direction, and the second preset direction is parallel to the vertical direction of the system coordinate system of optical ellipsometric measurement; the measurement positioning deviation includes the deviation in the horizontal direction of the system coordinate system obtained based on the first target measurement monitoring pad and the deviation in the vertical direction of the system coordinate system obtained based on the second target measurement monitoring pad.

[0016] In one embodiment of this application, the film thickness and thickness variation of the monitoring pads in different pattern regions in the preset direction are exactly the same; or, the film thickness of the monitoring pads in different pattern regions in the preset direction are different from each other.

[0017] In one embodiment of this application, the calibration wafer is provided with a plurality of patterned areas, each of the patterned areas is provided with a target measurement monitoring pad, and the preset direction is the radial direction of the calibration wafer.

[0018] According to a third aspect of this application, an apparatus for determining measurement positioning deviation is provided, the apparatus comprising a memory and a processor, the memory storing a computer program executed by the processor, the computer program, when executed by the processor, causing the processor to perform the above-described method for determining measurement positioning deviation.

[0019] According to a fourth aspect of this application, a storage medium is provided that stores a computer program executed by a processor, the computer program, when executed by the processor, causing the processor to perform the above-described method for determining measurement positioning deviation.

[0020] According to a fifth aspect of this application, a computer program product is provided that, when run by a processor, causes the processor to perform the above-described method for determining measurement positioning deviation.

[0021] The calibration wafer and the method for determining the measurement positioning deviation of this application rely on the linear relationship between thickness and position to calculate the movement offset of the wafer carrier component and the offset of the spot center relative to the CCD camera's field of view on the same calibration structure. The linear thickness change does not rely on line scan boundary recognition or image image comparison, avoiding the errors caused by inaccurate boundary judgment and significant impact on image quality in line scan mode. This greatly improves the measurement stability and accuracy, thereby significantly improving the calibration accuracy and reliability of the optical ellipsometry measurement system. Attached Figure Description

[0022] The above and other objects, features, and advantages of the present invention will become more apparent from the more detailed description of the embodiments of the invention in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same parts or steps.

[0023] Figure 1 A schematic structural diagram of a calibration wafer according to an embodiment of this application is shown.

[0024] Figure 2A An example diagram is shown of a measurement monitoring pad for optical ellipticity measurement in a calibration wafer according to an embodiment of this application.

[0025] Figure 2B It shows according to Figure 2A The example shown is a schematic diagram illustrating the principle of determining measurement positioning deviation using a measurement monitoring pad.

[0026] Figure 3 A schematic diagram of the first and second measurement monitoring pads on the calibration wafer according to an embodiment of this application is shown.

[0027] Figure 4 A schematic flowchart illustrating a method for determining measurement positioning deviation according to an embodiment of this application is shown.

[0028] Figure 5 A table showing different tilt angles of the measurement monitoring pads on the calibration wafer and their corresponding detection limits used in the method for determining measurement positioning deviation according to embodiments of this application.

[0029] Figure 6 A schematic structural block diagram of an apparatus for determining measurement positioning deviation according to an embodiment of this application is shown. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described herein, all other embodiments obtained by those skilled in the art without inventive effort should fall within the protection scope of the present invention.

[0031] The movement accuracy of the sample stage (also known as the wafer carrier) is its movement offset. This movement offset refers to the positioning deviation of the actual moving position of the stage relative to the target theoretical position during the movement and positioning process. This manifests as the geometric center of the measurement monitoring pad failing to coincide with the preset alignment reference of the optical ellipsometer (which is the center of the CCD camera's field of view), and is considered a positioning error inherent to the stage itself. When the stage moves offset, the entire wafer on it undergoes a total translation in the device coordinate system. Existing methods for determining the stage's movement offset, as mentioned earlier, involve directly taking a picture of the pattern on the graphic piece and then calculating the pattern's position in the field of view to confirm the stage's movement offset. Specifically, the graphic piece with the pattern is fixed on the stage; the stage is controlled to move to the preset target position according to instructions (theoretically, the pattern should be at the specified coordinates in the SE device's field of view); the SE device's imaging system takes a picture of the pattern within the field of view; the algorithm identifies the actual position of the pattern in the picture, compares it with the preset theoretical position, and calculates the difference between the two. This difference is the stage's movement offset. The smaller the offset, the closer the actual position of the stage after movement is to the target position, and the higher the movement accuracy; conversely, the accuracy is insufficient. This scheme relies on the camera's pixels and image quality. The size of a single pixel is approximately 0.5µm / pixel, and the boundaries are blurred, making it difficult to achieve precise edge detection.

[0032] The spot drift, also known as the offset between the CCD camera's field of view center and the spot center of an optical ellipsometer, refers to the relative positional deviation caused by the misalignment of the measurement spot center and the CCD camera's field of view center, even when the stage is precisely positioned and the geometric center of the measurement pad coincides with the CCD camera's field of view center. This deviation is a systematic deviation between the measurement optical path and the visual alignment optical path. Existing methods for determining spot drift, as mentioned earlier, utilize line scan mode to measure the variation curves of parameters such as THK, Normalized Global Optical Fit (NGOF), and Mean Squared Error (MSE) in the pad area to determine the spot drift. Specifically, the stage is controlled to drive the pad to perform a linear scan (line scan mode) along a certain direction, allowing the light spot to sequentially scan different positions on the pad. THK, NGOF, and MSE data are collected in real time at each position along the light spot's scanning path. Curves showing the changes in these parameters are plotted. Due to the uniform structure of the pad, the curves will exhibit stable and fluctuating segments: stable segments correspond to the light spot completely covering the uniform area of ​​the pad, while fluctuating segments correspond to the light spot scanning to the edge of the pad or a non-uniform area. The midpoint or extreme point of the stable segment of the curve is the actual center position of the light spot. This is compared with the preset field of view center of the CCD camera; the difference is the offset of the light spot center (i.e., the light spot offset). The smaller the light spot offset, the higher the alignment between the light spot center and the CCD camera's field of view center, the lower the risk of signal distortion during measurement, and the better the stability of the light spot position; conversely, the larger the offset, the worse the stability.

[0033] As mentioned above, the existing solution cannot simultaneously measure the stage movement offset and the spot offset, and the measurement results are inaccurate.

[0034] Based on this, this application provides a calibration wafer and a method for determining measurement positioning deviation based on the calibration wafer, in order to solve the above problems.

[0035] Figure 1 A schematic structural diagram of a calibration wafer 100 according to an embodiment of this application is shown. Figure 1 As shown, the calibration wafer 100 is provided with a measurement monitoring pad 110 that can be used for optical elliptic measurement. The film thickness of the measurement monitoring pad 110 varies linearly in at least one preset direction (i.e., it has a tilt angle in at least one preset direction).

[0036] Because the film thickness of traditional uniform film measurement pads is basically the same at different positions, the center of the light spot can only be determined by the thickness stability range, and it is impossible to distinguish whether the offset is caused by stage movement error or light spot offset. The calibration wafer 100 of this application is provided with a measurement monitoring pad 110 whose film thickness varies linearly in at least one preset direction. The film thickness and scanning position have a unique linear relationship. Using this same thickness-position mapping relationship, the offset of the wafer carrier component movement and the light spot offset can be independently calculated and distinguished, realizing the simultaneous measurement of both positioning deviations. See below for reference. Figures 2A to 2B To describe.

[0037] Figure 2A An example diagram is shown of a measurement monitoring pad 110 for optical ellipticity measurement in a calibration wafer 100 according to an embodiment of this application; Figure 2B It shows according to Figure 2A The schematic diagram shown illustrates how the measurement monitoring pad 110 determines the measurement positioning deviation (stage movement offset and spot offset).

[0038] like Figure 2A As shown, the SiO2 film (for example only, not necessarily a SiO2 film) is tilted at an angle θ along the L direction. Its thickness and scanning position follow a linear function relationship: THK = T0 + L ⋅ tanθ. Where T0 is the reference film thickness at the geometric center, tanθ is a preset, known linear gradient coefficient, and L is the displacement relative to the reference position. After the stage moves the calibration wafer 100 to the theoretical coordinate position, the SE device performs a line scan on this linearly changing film, acquiring a series of discrete displacement coordinate L pairs with corresponding film thickness THK data. For example, L1 corresponds to THK1, L2 corresponds to THK2, and so on. Figure 2B As shown, by performing linear regression fitting on these data, a THK-L regression line can be obtained (such as the blue line in 2B). The stage movement offset and spot offset can be obtained based on this regression line.

[0039] Specifically, for the stage's movement offset, the stage movement target measurement monitoring pad 110 can be controlled to position the CCD camera's field of view center at the theoretical center coordinates, and a single SE measurement can be performed at this position to obtain the actual thickness value THK0. Substituting this thickness value into the fitted regression equation THK=T0+L⋅tanθ, the offset L0 between the actual position and the theoretical center position corresponding to this thickness can be solved, where L0=(THK0-T0) / tanθ, and L0 is the stage's movement offset in the L direction.

[0040] To determine the spot offset, the center of the CCD camera's field of view can be precisely positioned at the geometric center of the measurement monitoring pad 110 to completely eliminate the influence of stage movement error on the measurement. Subsequently, SE measurement is performed at this fixed position to measure the actual film thickness THK1. Substituting the measured thickness THK1 into THK=T0+L⋅tanθ, the actual physical position corresponding to this thickness can be solved: L1=(THK1-T0) / tanθ. Since the stage has been precisely positioned and the center of the monitoring pad coincides with the center of the CCD's field of view, the solved L1 accurately reflects the offset of the spot center relative to the center of the CCD camera's field of view.

[0041] In one embodiment of this application, a plurality of patterned regions are provided on the calibration wafer 100 in the aforementioned preset direction. Each patterned region is provided with two measurement monitoring pads 110, namely a first measurement monitoring pad and a second measurement monitoring pad. The preset direction includes a first preset direction and a second preset direction, wherein: the film thickness of the first measurement monitoring pad changes linearly in the first preset direction, which is parallel to the horizontal direction of the system coordinate system of optical elliptic measurement; the film thickness of the second measurement monitoring pad changes linearly in the second preset direction, which is parallel to the vertical direction of the system coordinate system of optical elliptic measurement. Figure 3 This illustrates such an example. For instance... Figure 3 As shown, the arrow indicates the slope direction of the measurement monitoring pad. A set of measurement monitoring pads consists of two measurement monitoring pads with a slope of 90 degrees. Figure 3 PADX and PADY in the system coordinate system can be used to measure the stage movement offset and spot offset in the horizontal direction (X direction) and vertical direction (Y direction) of the system coordinate system, respectively.

[0042] In this embodiment, by setting a first measurement monitoring pad with a film thickness that linearly varies along the horizontal direction parallel to the system coordinate system and a second measurement monitoring pad with a film thickness that linearly varies along the vertical direction in multiple patterned areas of the calibration wafer 100, the stage movement offset and the offset of the spot center relative to the CCD camera's field of view can be independently calculated in the X and Y orthogonal dimensions, avoiding directional coupling interference and achieving accurate separation and quantification of two-dimensional positioning deviation. Moreover, the multi-area layout enables multi-point repeated measurement and statistical analysis, effectively improving measurement stability and reliability. Furthermore, since the thickness change direction is strictly parallel to the system coordinate system, the offset in the corresponding direction can be directly mapped without complex coordinate transformations, greatly simplifying the calculation and calibration process and comprehensively improving the positioning accuracy and calibration efficiency of the optical ellipsometry system.

[0043] In this embodiment, the film thickness and thickness variation of the measurement monitoring pads 110 in different pattern regions along a preset direction are completely identical; or, the film thickness of the measurement monitoring pads 110 in different pattern regions along a preset direction is different from each other. By setting the measurement monitoring pads 110 in different pattern regions along the same preset direction on the calibration wafer 100 to have either completely identical film thickness and thickness variation, or different thicknesses with no overlap, effective differentiation and precise positioning of different pattern regions can be achieved while ensuring measurement accuracy. When the thickness variation of each monitoring pad is consistent along the same preset direction, it ensures a unified measurement benchmark and stable testing accuracy, facilitating the differentiation of measurement results in different regions. When the thicknesses of each monitoring pad are different and do not overlap, the actual position corresponding to the light spot can be uniquely determined directly based solely on the measured thickness value, further simplifying the positioning logic and improving the accuracy and uniqueness of position identification. This balances measurement consistency, regional differentiation, and positioning accuracy, making the calibration and testing of the entire optical ellipsometric measurement system more flexible and reliable.

[0044] In another embodiment of this application, the calibration wafer 100 is provided with multiple patterned regions, and each patterned region is provided with a measurement monitoring pad 110, with the preset direction being the radial direction of the calibration wafer 100. In this embodiment, by setting the calibration wafer 100 as multiple patterned regions, and configuring a measurement monitoring pad 110 with a linearly varying film thickness along the radial direction of the wafer in each patterned region, it is possible to accurately quantify and distinguish the stage movement offset and the offset of the spot center relative to the CCD camera's field of view in the radial dimension of the wafer. In addition, multiple patterned regions can provide multi-point measurement and statistical verification, improving measurement stability and repeatability. The linearly varying film thickness along the radial direction can directly convert the radial position deviation into a thickness difference, realizing an intuitive and efficient solution for the wafer's radial positioning error, thereby adapting to the measurement and calibration requirements of radial distribution, and comprehensively improving the positioning accuracy, identification reliability, and calibration applicability of the optical ellipsometric measurement system in the radial direction.

[0045] In another embodiment of this application, a plurality of patterned regions are provided on the calibration wafer 100, and each patterned region is provided with a measurement monitoring pad 110, the preset direction of which is parallel to the notch of the calibration wafer 100 (e.g. Figure 3The notch 120 shown is in the direction of the notch, or perpendicular to the notch direction of the calibration wafer 100. In this embodiment, by matching the preset direction of the linearly varying film thickness of the measurement monitoring pad 110 with the parallel or perpendicular orientation of the wafer notch, the measurement direction can be precisely aligned with the reference direction of the wafer process using the inherent physical identifier of the wafer notch as the positioning reference. This adapts to the operation logic of using the notch as a reference during wafer production and inspection. At the same time, the linearly varying film thickness of the measurement monitoring pad 110 arranged along these two directions can accurately quantify and independently calibrate the stage movement offset parallel to and perpendicular to the notch direction, and the offset of the spot center relative to the CCD camera's field of view center, respectively. This achieves decoupled measurement of positioning errors in two orthogonal dimensions, effectively avoiding mutual interference between offsets in different directions. The multi-point measurement data of multiple pattern areas can also form a statistical verification of the notch reference direction, further improving the stability, repeatability, and accuracy of positioning error measurement under this orthogonal dual-dimensional system, and optimizing the positioning calibration capability of the optical ellipsometric measurement system for the wafer notch reference.

[0046] In the embodiments of this application, the measurement monitoring pad 110 can be a single-film structure. The single-film structure of the measurement monitoring pad 110 is simple in structure, easy to control in process, and ensures better uniformity and thickness consistency of the film layers. It can effectively avoid interface reflections, stress differences, and inter-film interference between multilayer films, making the linear relationship between thickness and position more stable and accurate, thereby significantly improving the reliability and measurement accuracy of thickness-position mapping. At the same time, the single-film structure simplifies the preparation process of the calibration wafer 100, reduces process complexity and cost, and its single optical response facilitates the analysis of ellipticity measurement data and the calculation of offset, further improving the system calibration efficiency and stability.

[0047] Based on the above description, the calibration wafer 100 according to the embodiment of this application is provided with a measurement monitoring pad whose film thickness varies linearly in at least one preset direction. This effectively solves the problem that the prior art cannot simultaneously measure stage positioning accuracy and spot offset, and the measurement accuracy is insufficient. Relying on the linear relationship between thickness and position, the movement offset of the wafer carrier component and the offset of the spot center relative to the CCD camera's field of view can be calculated separately on the same calibration structure, realizing the simultaneous measurement of the two deviations. The linear thickness change does not rely on line scan boundary recognition or image image comparison, avoiding the errors caused by inaccurate boundary judgment and large image quality impact in line scan mode. The position offset can be accurately deduced directly from the thickness value, greatly improving the measurement stability and accuracy, thereby significantly improving the calibration accuracy and reliability of the optical ellipsometry measurement system.

[0048] The following is combined with Figure 4This application describes a method 200 for determining measurement positioning deviations according to an embodiment of the present application. The method determines the measurement positioning deviations (including stage movement offset and the offset of the spot center relative to the CCD camera's field of view center) based on the calibration wafer described above according to an embodiment of the present application. Figure 4 As shown, the method 200 for determining measurement positioning deviation according to an embodiment of this application may include the following steps: In step S210, a calibration wafer is provided, on which a measurement monitoring pad capable of optical ellipsometric measurement is provided, and the film thickness of the measurement monitoring pad varies linearly in at least one preset direction.

[0049] In step S220, the calibration wafer is loaded onto the wafer carrier component, and the target measurement and monitoring pad is scanned along a preset direction using an optical ellipsometry device to obtain a fitted regression line of the film thickness as a function of the scanning position. The theoretical center coordinates of the target measurement and monitoring pad are obtained through the fitted regression line.

[0050] In step S230, the CCD camera field of view center of the optical ellipsometry measuring device is positioned at the theoretical center coordinates, the actual thickness of the film at the theoretical center coordinates of the target measurement monitoring pad is obtained, the actual thickness of the film is substituted into the fitted regression line to obtain the actual center coordinates corresponding to the actual thickness of the film, and the measurement positioning deviation is obtained based on the actual center coordinates and the theoretical center coordinates.

[0051] As mentioned above, method 200 uses a calibration wafer with a film thickness that varies linearly along at least one preset direction. First, it establishes a thickness-position fitting regression line using line scanning and determines the theoretical center coordinates. Then, it aligns the CCD camera's field of view with these theoretical center coordinates and measures the actual thickness. Substituting the measured thickness into the regression line, it obtains the actual center coordinates. Finally, it obtains the measurement positioning deviation by comparing the theoretical and actual center coordinates. This method does not rely on line scanning boundary judgment or image image comparison, effectively avoiding problems such as boundary recognition errors and significant impact on image quality in existing technologies. At the same time, it can independently calculate and distinguish the wafer-supporting component movement offset and the offset of the spot center relative to the CCD camera's field of view based on the same set of thickness-position linear mapping relationships, achieving accurate quantification and simultaneous measurement of the two positioning deviations, significantly improving measurement accuracy and system calibration efficiency.

[0052] In the embodiments of this application, the measurement positioning deviation includes the movement offset of the wafer carrier component. Obtaining the movement offset of the wafer carrier component includes: controlling the wafer carrier component to move the target measurement monitoring pad so that the center of the CCD camera's field of view is positioned at the theoretical center coordinates; using an optical ellipsometry measurement device to measure the actual thickness of the thin film at the theoretical center coordinates to obtain the first actual thickness of the thin film at the theoretical center coordinates; substituting the first actual thickness of the thin film into the fitted regression line to obtain the first actual center coordinates corresponding to the first actual thickness of the thin film; and obtaining the movement offset of the wafer carrier component based on the first actual center coordinates and the theoretical center coordinates.

[0053] For example, for a target measurement and monitoring pad PADX with theoretical center coordinates (X0, Y0), the stage can be moved to position the target measurement and monitoring pad PADX so that the CCD camera's field of view center is located at the theoretical center coordinates (X0, Y0). A single SE measurement is then performed at this position to obtain the actual thickness value THK0. Substituting this thickness value into the fitted regression equation THK=T0+L⋅tanθ, the offset L0 between the actual position and the theoretical center position corresponding to this thickness can be solved, where L0=(THK0-T0) / tanθ. This L0 is the stage's offset in the L direction. To make the results more accurate, the above process can be repeated multiple times to obtain multiple L0 values, and their three standard deviations can be calculated as the stage's offset in the X direction. Similarly, the same operation can be performed on the Y-direction measurement and monitoring pad (PADY) to obtain the stage's offset in the Y direction.

[0054] In the embodiments of this application, the measurement positioning deviation includes the offset between the CCD camera field of view center and the spot center of the optical ellipsometric measuring device. Obtaining the offset between the CCD camera field of view center and the spot center includes: positioning the CCD camera field of view center of the optical ellipsometric measuring device to the theoretical center coordinates; measuring the film thickness at the theoretical center coordinates using the optical ellipsometric measuring device to obtain the second actual film thickness at the theoretical center coordinates; substituting the second actual film thickness into the fitted regression line to obtain the second actual center coordinates corresponding to the second actual film thickness; and obtaining the offset between the CCD camera field of view center and the spot center based on the second actual center coordinates and the theoretical center coordinates.

[0055] For the spot offset, the CCD camera's field of view center of the optical ellipsometer can be precisely positioned to the geometric center of the target measurement monitoring pad (PADX) through the Recipe Calibration Procedure (RCP) teaching operation. Then, the film thickness THK1 is measured according to the site alignment measurement procedure for patterned wafers (PW). Substituting the measured thickness THK1 into THK = T0 + L⋅tanθ, the actual physical position corresponding to this thickness can be solved: L1 = (THK1 - T0) / tanθ, which is the offset between the CCD camera's field of view center and the spot center in the X direction. Similarly, the same operation is performed on the Y-direction measurement monitoring pad (PADY) to obtain the offset between the CCD camera's field of view center and the spot center in the Y direction.

[0056] In the embodiments of this application, a plurality of patterned regions are provided on the calibration wafer in a preset direction. Each patterned region is provided with two target measurement monitoring pads, namely a first target measurement monitoring pad and a second target measurement monitoring pad. The preset direction includes a first preset direction and a second preset direction, wherein: the film thickness of the first target measurement monitoring pad changes linearly in the first preset direction, which is parallel to the horizontal direction of the system coordinate system of optical elliptic measurement; the film thickness of the second target measurement monitoring pad changes linearly in the second preset direction, which is parallel to the vertical direction of the system coordinate system of optical elliptic measurement; the measurement positioning deviation includes the deviation in the horizontal direction of the system coordinate system obtained based on the first target measurement monitoring pad and the deviation in the vertical direction of the system coordinate system obtained based on the second target measurement monitoring pad.

[0057] In this embodiment, by setting a first target measurement monitoring pad with a film thickness that linearly varies along the horizontal direction parallel to the system coordinate system and a second target measurement monitoring pad with a film thickness that linearly varies along the vertical direction in multiple patterned areas of the calibration wafer, the stage movement offset and the offset of the spot center relative to the CCD camera's field of view can be independently calculated in the X and Y orthogonal dimensions. This avoids directional coupling interference and achieves accurate separation and quantification of two-dimensional positioning deviations. Moreover, the multi-region layout enables multi-point repeated measurements and statistical analysis, effectively improving measurement stability and reliability. Furthermore, since the thickness variation direction is strictly parallel to the system coordinate system, the offset in the corresponding direction can be directly mapped without complex coordinate transformations, greatly simplifying the calculation and calibration process and comprehensively improving the positioning accuracy and calibration efficiency of the optical ellipsometric measurement system.

[0058] In this embodiment, the film thickness and thickness variation of the measurement monitoring pads in different pattern regions along a preset direction are completely identical; or, the film thickness of the measurement monitoring pads in different pattern regions along a preset direction is different from each other. By setting the measurement monitoring pads in different pattern regions along the same preset direction on the calibration wafer to have either completely identical film thickness and thickness variation, or different thicknesses with no overlap, effective differentiation and precise positioning of different pattern regions can be achieved while ensuring measurement accuracy. When the thickness variation of each monitoring pad is consistent along the same preset direction, it ensures a unified measurement benchmark and stable testing accuracy, facilitating the differentiation of measurement results in different regions. When the thicknesses of each monitoring pad are different and do not overlap, the actual position corresponding to the light spot can be uniquely determined directly based solely on the measured thickness value, further simplifying the positioning logic and improving the accuracy and uniqueness of position identification. This balances measurement consistency, regional differentiation, and positioning accuracy, making the calibration and testing of the entire optical ellipsometric measurement system more flexible and reliable.

[0059] In the embodiments of this application, multiple patterned regions are provided on the calibration wafer, and a target measurement monitoring pad is provided in each patterned region, with the preset direction being the radial direction of the calibration wafer. In this embodiment, by setting the calibration wafer as multiple patterned regions and configuring a measurement monitoring pad with a linearly varying film thickness along the radial direction of the wafer in each patterned region, accurate quantification and regional differentiation of stage movement offset and the offset of the spot center relative to the CCD camera's field of view center can be achieved in the radial dimension of the wafer. In addition, multiple patterned regions can provide multi-point measurement and statistical verification, improving measurement stability and repeatability. The linearly varying film thickness along the radial direction can directly convert radial position deviation into thickness difference, realizing intuitive and efficient calculation of wafer radial positioning error, thereby adapting to the measurement and calibration requirements of radial distribution, and comprehensively improving the positioning accuracy, identification reliability, and calibration applicability of the optical ellipsometric measurement system in the radial direction.

[0060] Based on the above description, the method 200 for determining measurement positioning deviation according to the embodiments of this application uses a calibration wafer with a film thickness that varies linearly along at least one preset direction. First, a thickness-position fitting regression line is established using line scanning to determine the theoretical center coordinates. Then, the center of the CCD camera's field of view is aligned with the theoretical center coordinates, and the actual thickness is measured. The actual center coordinates are obtained by substituting them into the regression line. Finally, the measurement positioning deviation is obtained by the difference between the theoretical center coordinates and the actual center coordinates. This method does not rely on line scanning boundary judgment or image image comparison, and can effectively avoid problems such as boundary recognition errors and significant impact on image quality in the prior art. At the same time, it can independently calculate and distinguish the wafer carrier component movement offset and the offset of the spot center relative to the CCD camera's field of view based on the same set of thickness-position linear mapping relationships, realizing accurate quantification and simultaneous measurement of the two positioning deviations, significantly improving measurement accuracy and system calibration efficiency.

[0061] Overall, this application improves upon existing solutions in both speed and accuracy, and eliminates the influence of subjective human factors. Specifically, regarding speed, existing methods for measuring spot offset require measuring the film thickness at multiple locations on the pad, while this application only requires measuring the film thickness at one location (theoretical center coordinates), significantly improving speed. Regarding subjectivity, existing methods require manual observation of the stable segment of the curve to obtain the actual center position of the spot, which is subject to subjective human factors. This application only requires measuring the thickness and substituting it into the THK-L regression line to obtain the spot offset, thus eliminating the influence of subjective human factors. Regarding the improved accuracy, as mentioned above, the thickness at the center position is T0. Due to the gentle slope, this can be simplified to the thickness obtained from planar spot testing, which is also T0. After offset L, the thickness is T0 + L⋅tanθ, and the thickness change is L⋅tanθ. When the thickness change exceeds the repeatability (dynamic stability, 6 times the standard deviation) of the SE measurement, it can be detected. Therefore, the detection accuracy of this application is 6 sigma / tanθ. Taking T0=2000A as an example, the dynamic stability of SE is 6sigma=2A. Figure 5 The table shown is a data table of the corresponding θ and limits. It can be seen that the accuracy (detection limit of L) can reach below 0.1um. Therefore, the existing methods that rely on camera pixels and image imaging quality to measure stage movement offset have a single pixel size of about 0.5um / pixel. The accuracy of this application can reach below 0.1um, which is an order of magnitude improvement.

[0062] The following is combined with Figure 6 A schematic structural block diagram of an apparatus 300 for determining measurement positioning deviation according to an embodiment of this application is described. Figure 6As shown, the apparatus 300 for determining measurement positioning deviation in this embodiment of the application may include a memory 310 and a processor 330. The memory 310 stores a computer program that is executed by the processor 330. When the computer program is executed by the processor 330, it causes the processor to perform the method 200 for determining measurement positioning deviation described above. Those skilled in the art can understand the structure and operation of the apparatus 300 for determining measurement positioning deviation in conjunction with the foregoing description; for the sake of brevity, it will not be described again here.

[0063] Furthermore, according to embodiments of this application, a storage medium is also provided, on which program instructions are stored. When the program instructions are executed by a computer or processor, they are used to perform the method 200 for determining measurement deviation according to embodiments of this application. The storage medium may, for example, include a memory card of a smartphone, a storage component of a tablet computer, a hard disk of a personal computer, a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a portable compact disc read-only memory (CD-ROM), a USB memory, or any combination of the above storage media. A computer-readable storage medium may be any combination of one or more computer-readable storage media.

[0064] Furthermore, according to embodiments of this application, a computer program product is also provided, which can be stored on a cloud or local storage medium. When this computer program product is run by a computer or processor, it is used to execute the method 200 for determining measurement positioning deviation according to embodiments of this application.

[0065] Although exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above exemplary embodiments are merely illustrative and are not intended to limit the scope of the invention. Various changes and modifications can be made therein by those skilled in the art without departing from the scope and spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as claimed in the appended claims.

[0066] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0067] In the several embodiments provided by this invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed.

[0068] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0069] Similarly, it should be understood that, in order to streamline the invention and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the description of exemplary embodiments of the invention. However, the method of the invention should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the corresponding claims, its inventive point lies in solving the corresponding technical problem with fewer features than all of those in a single disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0070] Those skilled in the art will understand that, apart from the mutual exclusion of features, all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or elements of any method or apparatus so disclosed may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0071] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0072] The various component embodiments of the present invention can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some modules in the article analysis device according to embodiments of the present invention. The present invention can also be implemented as an apparatus program (e.g., a computer program and computer program product) for performing part or all of the methods described herein. Such programs implementing the present invention can be stored on a computer-readable medium or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0073] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0074] The above are merely specific embodiments or descriptions of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A calibration wafer, characterized in that, The calibration wafer is provided with a measurement monitoring pad that can be used for optical ellipticity measurement, and the film thickness of the measurement monitoring pad varies linearly in at least one preset direction.

2. The calibration wafer according to claim 1, characterized in that, The calibration wafer has multiple patterned regions arranged in the preset direction, and each patterned region has two measurement monitoring pads, namely a first measurement monitoring pad and a second measurement monitoring pad. The preset direction includes a first preset direction and a second preset direction, wherein: The thickness of the film layer of the first measurement monitoring pad varies linearly in the first preset direction, which is parallel to the horizontal direction of the system coordinate system of optical elliptic measurement. The thickness of the film layer of the second measurement monitoring pad varies linearly in the second preset direction, which is parallel to the vertical direction of the system coordinate system of the optical elliptic measurement.

3. The calibration wafer according to claim 2, characterized in that, The film thickness and thickness variation of the measurement and monitoring pads in different pattern regions of the preset direction are exactly the same; or, the film thickness of the measurement and monitoring pads in different pattern regions of the preset direction are different from each other.

4. The calibration wafer according to claim 1, characterized in that, The calibration wafer has multiple patterned areas, and each patterned area has a measurement monitoring pad. The preset direction is the radial direction of the calibration wafer.

5. The calibration wafer according to any one of claims 1-4, characterized in that, The measurement and monitoring pad has a single-film structure.

6. A method for determining measurement positioning deviation, characterized in that, The method includes: A calibration wafer is provided, on which a measurement monitoring pad capable of optical ellipsometric measurement is provided, wherein the film thickness of the measurement monitoring pad varies linearly in at least one preset direction. The calibration wafer is loaded onto the wafer carrier component, and the target measurement and monitoring pad is scanned along the preset direction using an optical elliptic measurement device to obtain a fitted regression line of the film thickness as a function of the scanning position. The theoretical center coordinates of the target measurement and monitoring pad are obtained through the fitted regression line. The center of the field of view of the charge-coupled device camera of the optical ellipsometry is located at the theoretical center coordinates. The actual thickness of the film at the theoretical center coordinates of the target measurement monitoring pad is obtained. The actual thickness of the film is substituted into the fitted regression line to obtain the actual center coordinates corresponding to the actual thickness of the film. The measurement positioning deviation is obtained based on the actual center coordinates and the theoretical center coordinates.

7. The method according to claim 6, characterized in that, The measurement positioning deviation includes the displacement of the wafer carrier component. Obtaining the displacement of the wafer carrier component includes: The wafer carrier component is controlled to move the target measurement and monitoring pad so that the field of view center of the charge-coupled device camera is positioned at the theoretical center coordinates. The optical ellipsometry measuring device is used to measure the actual thickness of the thin film at the theoretical center coordinates to obtain the first actual thickness of the thin film at the theoretical center coordinates. Substituting the actual thickness of the first film into the fitted regression line, the first actual center coordinates corresponding to the actual thickness of the first film are obtained. Based on the first actual center coordinates and the theoretical center coordinates, the movement offset of the wafer carrier component is obtained.

8. The method according to claim 6, characterized in that, The measurement positioning deviation includes the offset between the center of the field of view of the charge-coupled device (CCD) camera and the center of the light spot in the optical ellipsometric measurement device. Obtaining the offset between the center of the field of view of the CCD camera and the center of the light spot includes: The field of view center of the charge-coupled device camera of the optical elliptic measuring device is located at the theoretical center coordinates, and the film thickness at the theoretical center coordinates is measured using the optical elliptic measuring device to obtain the second actual film thickness at the theoretical center coordinates. Substituting the actual thickness of the second film into the fitted regression line, the second actual center coordinates corresponding to the actual thickness of the second film are obtained. Based on the second actual center coordinates and the theoretical center coordinates, the offset between the field of view center and the spot center of the charge-coupled device camera is obtained.

9. The method according to any one of claims 6-8, characterized in that, The calibration wafer has multiple patterned regions arranged in the preset direction, and each patterned region has two target measurement monitoring pads, namely a first target measurement monitoring pad and a second target measurement monitoring pad. The preset direction includes a first preset direction and a second preset direction, wherein: The film thickness of the first target measurement and monitoring pad varies linearly in the first preset direction, which is parallel to the horizontal direction of the system coordinate system of optical ellipsometric measurement. The film thickness of the second target measurement monitoring pad varies linearly in the second preset direction, which is parallel to the vertical direction of the system coordinate system of optical elliptic measurement. The measurement positioning deviation includes the horizontal deviation of the system coordinate system obtained based on the first target measurement monitoring pad and the vertical deviation of the system coordinate system obtained based on the second target measurement monitoring pad.

10. The method according to claim 9, characterized in that, The film thickness and thickness variation of the monitoring pads in different pattern regions of the preset direction are exactly the same; or, the film thickness of the monitoring pads in different pattern regions of the preset direction are different from each other.

11. The method according to any one of claims 6-8, characterized in that, The calibration wafer has multiple patterned areas, and each patterned area has a target measurement monitoring pad. The preset direction is the radial direction of the calibration wafer.

12. An apparatus for determining measurement positioning deviation, characterized in that, The device includes a memory and a processor, the memory storing a computer program executed by the processor, the computer program, when executed by the processor, causing the processor to perform the method for determining measurement positioning deviation as described in any one of claims 6-11.

13. A storage medium, characterized in that, The storage medium stores a computer program that is executed by a processor, which, when executed by the processor, causes the processor to perform the method for determining measurement positioning deviation as described in any one of claims 6-11.

14. A computer program product, characterized in that, When the computer program product is run by a processor, the processor performs the method for determining measurement positioning deviation as described in any one of claims 6-11.

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