Method and device for measuring the offset of the center of an objective lens in a lithography apparatus

Abstract

The present invention discloses a method and device for measuring the center offset of an objective lens in a lithography apparatus. The measurement method includes: aligning the center of a preset pattern on a mask plate with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure; placing a substrate to be exposed on a moving stage, and aligning the center of the moving stage with the theoretical projection center of the objective lens; moving the substrate to expose a preset area to be exposed on the substrate; wherein, the preset area to be exposed is centrosymmetric and includes at least four sub-areas to be exposed having the same distance from the center of the moving stage; obtaining the final actual image of the exposed substrate, and obtaining the corresponding final theoretical image after the substrate is exposed; performing correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least part of the final theoretical image corresponding to the preset area to be exposed. The present invention can improve the measurement accuracy of the center offset.

Description

Technical Field

[0001] The present invention relates to the technical field of lithography equipment, and in particular, to a method and device for measuring the center offset of an objective lens in a lithography equipment. Background Art

[0002] A lithography equipment is a core device for manufacturing chips, which can transfer fine patterns on a mask plate onto a substrate through exposure. Before performing the lithography process, it is necessary to calibrate the projection centers of the stage and the objective lens to ensure the accurate execution of the lithography process.

[0003] To calibrate the projection centers of the stage and the objective lens, it is necessary to first measure the center offset of the objective lens. In the related art, the field imaging alignment technology can be used to locate the center offset. The field imaging alignment technology designs some measurement patterns on the mask plate, then exposes them at specified positions on the silicon wafer, and finally extracts the coordinates of specified feature points in these images and calculates the average value of these feature point coordinates as the result of the center offset. However, the above method for measuring the center offset has the disadvantage of low accuracy. Summary of the Invention

[0004] The present invention provides a method and device for measuring the center offset of an objective lens in a lithography equipment to improve the measurement accuracy of the center offset.

[0005] According to one aspect of the present invention, there is provided a method for measuring the center offset of an objective lens in a lithography equipment, including:

[0006] Align the center of a preset pattern on the mask plate with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure;

[0007] Place the substrate to be exposed on the stage and align the center of the stage with the theoretical projection center of the objective lens;

[0008] Move the substrate to expose a preset area to be exposed on the substrate; wherein, the preset area to be exposed is centrosymmetric and includes at least four sub-areas to be exposed having the same distance from the center of the stage;

[0009] Obtain the final actual image of the substrate after exposure and obtain the corresponding final theoretical image of the substrate after exposure;

[0010] Perform correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least a part of the final theoretical image corresponding to the preset area to be exposed.

[0011] Optionally, obtaining the corresponding final theoretical image of the substrate after exposure includes:

[0012] Generate an initial theoretical image according to the exposure parameters of the substrate;

[0013] Generate the final theoretical image according to the initial theoretical image.

[0014] Optionally, the generating the final theoretical image according to the initial theoretical image includes:

[0015] Use the initial theoretical image as the final theoretical image;

[0016] Or, perform a first upsampling on the initial theoretical image to generate a first intermediate theoretical image;

[0017] Generate the final theoretical image according to the first intermediate theoretical image.

[0018] Optionally, the generating the final theoretical image according to the first intermediate theoretical image includes:

[0019] Use the first intermediate theoretical image as the final theoretical image;

[0020] Or, perform at least one of a stage orthogonal motion correction, a reticle alignment correction, and an objective magnification correction on the first intermediate theoretical image to obtain a second intermediate theoretical image;

[0021] Use the second intermediate theoretical image as the theoretical image.

[0022] Optionally, the performing at least one of a stage orthogonal motion correction, a reticle alignment correction, and an objective magnification correction on the first intermediate theoretical image to obtain a second intermediate theoretical image includes:

[0023] Perform a stage orthogonal motion correction, a reticle alignment correction, and an objective magnification correction on the first intermediate theoretical image to obtain the second intermediate theoretical image.

[0024] Optionally, the generating the final theoretical image according to the initial theoretical image includes: performing a first upsampling on the initial theoretical image to generate a first intermediate theoretical image; generating the final theoretical image according to the first intermediate theoretical image;

[0025] The obtaining the final actual image of the exposed substrate includes:

[0026] Collect an initial actual image of the exposed substrate;

[0027] Perform a second upsampling on the initial actual image to obtain a first intermediate actual image;

[0028] Multiply and sum the parts of the first intermediate actual image corresponding to each sub-exposure area by the corresponding weight coefficients to obtain a second intermediate actual image;

[0029] Use the second intermediate actual image as the final actual image; wherein, the weight coefficient of the part of the first intermediate actual image corresponding to the sub-area to be exposed is positively correlated with the exposure time of the sub-area to be exposed.

[0030] Optionally, the parameters of the first upsampling and the second upsampling are the same.

[0031] Optionally, the region of interest includes sub-regions of interest corresponding to each of the sub-areas to be exposed; the area of the sub-region of interest is smaller than the area of the corresponding sub-area to be exposed, the sub-region of interest is a centrosymmetric figure, and the sizes and shapes of the sub-regions of interest are the same.

[0032] Optionally, the calculating the center offset by performing correlation matching between the region of interest of the final theoretical image and the final actual image includes:

[0033] When the offset is taken within the region of interest, the offset corresponding to the maximum correlation is used as the center offset.

[0034] According to another aspect of the present invention, there is provided a measuring device for the center offset of an objective lens in a lithographic apparatus, which is used to perform the method for measuring the center offset of an objective lens in a lithographic apparatus as described above. The measuring device for the center offset of an objective lens in a lithographic apparatus includes:

[0035] A first alignment module, configured to align the center of a preset pattern on a mask plate with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure;

[0036] A second alignment module, configured to place a substrate to be exposed on a moving stage and align the center of the moving stage with the theoretical projection center of the objective lens;

[0037] A moving module, configured to move the substrate to expose a preset area to be exposed on the substrate; wherein, the preset area to be exposed is centrosymmetric and includes at least four sub-areas to be exposed with the same distance from the center of the moving stage;

[0038] An acquisition module, configured to acquire the final actual image of the substrate after exposure and acquire the final theoretical image corresponding to the substrate after exposure;

[0039] A processing module, configured to perform correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least a part of the final theoretical image corresponding to the preset area to be exposed.

[0040] The method for measuring the offset of the center of the objective lens in the lithography equipment adopted in the technical solution of the embodiment of the present invention includes: aligning the center of a preset pattern on the mask plate with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure; placing the substrate to be exposed on the moving stage, and aligning the center of the moving stage with the theoretical projection center of the objective lens; moving the substrate to expose a preset exposure area on the substrate; wherein, the preset exposure area is centrosymmetric and includes at least four sub-exposure areas with the same distance from the center of the moving stage; obtaining the final actual image of the exposed substrate, and obtaining the corresponding final theoretical image after the substrate is exposed; performing correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least part of the final theoretical image corresponding to the preset exposure area. By designing a preset pattern on the mask plate and exposing it in the centrosymmetric preset exposure area on the substrate to obtain the final actual image, and performing correlation calculation with the final actual image after obtaining the final theoretical image to calculate the center offset, there are more points used for calculation in the image, and the calculation accuracy of the center offset is higher.

[0041] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Brief Description of the Drawings

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0043] Figure 1 It is a flowchart of a method for measuring the offset of the center of the objective lens of a lithography equipment provided by an embodiment of the present invention;

[0044] Figure 2 It is a schematic diagram of a preset pattern provided by an embodiment of the present invention;

[0045] Figure 3 It is a schematic structural diagram of a substrate provided by an embodiment of the present invention;

[0046] Figure 4 It is a schematic diagram of the final actual image of a substrate provided by an embodiment of the present invention;

[0047] Figure 5 It is a schematic diagram of the final theoretical image of a substrate provided by an embodiment of the present invention;

[0048] Figure 6Schematic diagram of superposition of the final theoretical image and the final actual image of a substrate provided by an embodiment of the present invention;

[0049] Figure 7 Schematic structural diagram of a measuring device for the offset of the center of an objective lens in a lithography apparatus provided by an embodiment of the present invention. Specific embodiments

[0050] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0052] Figure 1 Flowchart of a method for measuring the offset of the center of an objective lens of a lithography apparatus provided by an embodiment of the present invention, refer to Figure 1 . The method for measuring the offset of the center of an objective lens of a lithography apparatus includes:

[0053] Step S110, align the center of a preset pattern on the mask plate with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure;

[0054] Specifically, a lithography apparatus includes a mask stage for carrying a mask, an objective lens, and a stage for carrying a substrate to be exposed. During the lithography process, the mask needs to be placed on the mask stage, and the substrate to be exposed needs to be placed on the stage. The center of the mask is aligned with the center of the objective lens, and the center of the stage needs to be aligned with the projection center of the objective lens. In this embodiment, first, the mask is placed on the mask stage, and the center of the preset pattern in the mask is aligned with the center of the objective lens. At this time, if the projection center of the objective lens on the stage coincides with the center of the stage, then the pattern formed by exposure on the substrate should be a preset pattern centered on the center of the stage and scaled by the magnification of the objective lens. If the projection center of the objective lens on the stage does not coincide with the center of the stage, then the center of the pattern formed by exposure on the substrate does not coincide with the center of the stage. In this embodiment, the mask can be a mask dedicated to various tests of the lithography apparatus, or a mask with a pattern corresponding to an actual product. The preset pattern can be understood as an alignment mark, such as Figure 2 as shown Figure 2 is a schematic diagram of a preset pattern provided by an embodiment of the present invention. The preset pattern is a centrosymmetric figure, which can be a "cross" shape, or a "rice" shape, etc. This embodiment does not limit this. The center point of the preset pattern is defined as O1. It should be noted that a circle of marking patterns can also be formed around the preset pattern to define and indicate the area where this part is the preset pattern.

[0055] Step S120: Place the substrate to be exposed on the stage, and align the center of the stage with the theoretical projection center of the objective lens;

[0056] Specifically, the substrate to be exposed is, for example, a rigid substrate such as a silicon substrate, a gallium arsenide substrate, or a silicon carbide substrate, or can also be a flexible substrate such as a polymer substrate. The center of the substrate to be exposed can be aligned with the center of the stage first, and then the stage is moved so that the center of the stage is aligned with the theoretical projection center of the objective lens. Of course, the center of the substrate to be exposed and the center of the stage can also be not aligned, and only the center of the stage needs to be moved to the theoretical projection center of the objective lens.

[0057] Step S130: Move the substrate to expose the preset exposure area of the substrate; wherein, the preset exposure area is centrosymmetric and includes at least four sub-exposure areas having the same distance from the center of the stage;

[0058] Specifically, as Figure 3 shown Figure 3Schematic diagram of a substrate provided by an embodiment of the present invention. The preset point O2 on the substrate is the point that aligns with the center point of the moving stage after being placed on the moving stage. Centered on the preset point O2, the preset area to be exposed on the substrate includes at least four sub-areas to be exposed, and each sub-area to be exposed is exposed using a preset pattern. The number of sub-areas to be exposed can be an even number to meet the requirement of central symmetry. In this embodiment, taking the preset area to be exposed including four sub-areas to be exposed as an example, the four sub-areas to be exposed are respectively defined as the first sub-area to be exposed P1, the second sub-area to be exposed P2, the third sub-area to be exposed P3, and the fourth sub-area to be exposed P4. The distance from each sub-area to be exposed to the preset point O2 is equal, and the connection line of the centers of two opposite sub-areas to be exposed is perpendicular, which is more convenient for subsequent correlation calculation. For example, the distance from each sub-area to be exposed to the preset point O2 is L. When exposing the sub-area to be exposed, the center point of the sub-area to be exposed is moved to the theoretical projection center of the objective lens through the moving stage to expose the sub-area to be exposed.

[0059] Step S140, obtain the final actual image of the exposed substrate, and obtain the corresponding final theoretical image after the substrate is exposed;

[0060] Specifically, as Figure 4 shown, Figure 4 Schematic diagram of a final actual image of a substrate provided by an embodiment of the present invention. When the exposure of the four sub-areas to be exposed is completed, the corresponding preset patterns on the mask are formed in the four sub-areas to be exposed of the substrate. In addition, for the convenience of description, the range of the sub-area to be exposed is represented by a rectangular dotted line frame in Figure 3 . The pattern corresponding to the first sub-area to be exposed P1 is the first actual exposure pattern P1’, the pattern corresponding to the second sub-area to be exposed P2 is the second actual exposure pattern P2’, the pattern corresponding to the third sub-area to be exposed P3 is the third actual exposure pattern P3’, and the pattern corresponding to the fourth sub-area to be exposed P4 is the fourth actual exposure pattern P4’.

[0061] Figure 5 Schematic diagram of a final theoretical image of a substrate provided by an embodiment of the present invention. Among them, the final theoretical image of the substrate is an image with the same exposure parameters as the final actual image and no central offset of the objective lens of the lithography equipment. The center points O3 of the four theoretical exposure patterns in the final theoretical image are aligned with the theoretical projection points of the objective lens. Of course, considering other compensations, there will also be a certain deviation in the center point O3, which will be described in detail later. In the final theoretical pattern, the pattern corresponding to the first sub-area to be exposed P1 is the first theoretical exposure pattern P1”, the pattern corresponding to the second sub-area to be exposed P2 is the second theoretical exposure pattern P2”, the pattern corresponding to the third sub-area to be exposed P3 is the third theoretical exposure pattern P3”, and the pattern corresponding to the fourth sub-area to be exposed P4 is the fourth theoretical exposure pattern P4”.

[0062] The positions of the corresponding sub-areas to be exposed in the final theoretical image and the final actual image are different. As Figure 6 shown, Figure 6 This is a schematic diagram of the superposition of the final theoretical image and the final actual image of a substrate provided by an embodiment of the present invention. The offset (m, n) between the preset point O2 in the final actual image and the center point O3 in the final theoretical image represents the center offset of the objective lens. Of course, it can be understood that when the final actual image and the final theoretical image are superposed, the edges of the corresponding substrate are aligned.

[0063] Step S150, perform correlation matching on the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least part of the corresponding preset area to be exposed in the final theoretical image.

[0064] Specifically, as described above, due to the deviation between the final theoretical image and the final actual image, the offset value of the final actual image relative to the final theoretical image when the correlation is the largest can be obtained through correlation calculation. When the correlation between the two is the largest, they coincide, and thus the offset value at this time is also the center offset of the objective lens. In addition, the differences between the parts of the corresponding unexposed areas in the final theoretical image and the final actual image are relatively small. Therefore, a region of interest (ROI) is selected in the final theoretical image. The region of interest includes the image corresponding to at least part of the sub-area to be exposed, and correlation calculation is performed with the final actual image. It is not necessary to calculate the entire final theoretical image, which can greatly reduce the amount of computation. In addition, in this embodiment, it is not necessary to calculate the center offset by extracting feature points. The calculation accuracy of the final center offset does not depend on the extraction accuracy of the feature points. By using the method of the correlation of two images to calculate the center offset, there are more points used for calculation in the image, and the calculation accuracy of the center offset is higher.

[0065] The measurement method for the center offset of the objective lens in the lithography equipment adopted in the technical solution of this embodiment includes: aligning the center of a preset pattern on the mask plate with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure; placing the substrate to be exposed on the moving stage, and aligning the center of the moving stage with the theoretical projection center of the objective lens; moving the substrate to expose a preset exposure area on the substrate; wherein, the preset exposure area is centrosymmetric and includes at least four sub-exposure areas with the same distance from the center of the moving stage; obtaining the final actual image of the exposed substrate, and obtaining the corresponding final theoretical image after the substrate is exposed; performing correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least a part of the final theoretical image corresponding to the preset exposure area. By designing a preset pattern on the mask plate, exposing the preset exposure area on the substrate that is centrosymmetric to obtain the final actual image, and performing correlation calculation with the final actual image after obtaining the final theoretical image to calculate the center offset, there are more points used for calculation in the image, and the calculation accuracy of the center offset is higher.

[0066] Optionally, in the above embodiment, as Figure 3 shown, the distance between each sub-exposure area and the preset point O2 on the substrate is L, and the distance L can be controlled within a quarter of the field of view on the premise of meeting the imaging quality. Of course, the distance L needs to ensure that there is no overlapping part between different sub-exposure areas.

[0067] Optionally, obtaining the corresponding final theoretical image after the substrate is exposed includes:

[0068] Generating an initial theoretical image according to the exposure parameters of the substrate;

[0069] Specifically, the exposure parameters of the substrate include, for example, the exposure time, and further can be the standard exposure time. The image corresponding to the substrate under the standard exposure time can be calculated by theoretical means, and the image obtained by theoretical calculation is used as the initial theoretical image. In the initial theoretical image, the projection center of the objective lens coincides with the position of the corresponding center point of the moving stage on the substrate (i.e., the preset point O2). Of course, it should be noted that the resolution of the initial theoretical image is the same as that of the image acquisition device for acquiring the actual image of the substrate.

[0070] Generating a final theoretical image according to the initial theoretical image. Specifically, the initial theoretical image can be directly used as the final theoretical image, or can be compensated to obtain the final theoretical image, so as to further improve the calculation accuracy of the center offset.

[0071] Optionally, as described above, in some embodiments, generating a final theoretical image according to the initial theoretical image includes:

[0072] Use the initial theoretical image as the final theoretical image. At this time, the amount of calculation required by the measurement method of the center offset is small, which can improve the processing speed.

[0073] In some other embodiments, optionally, generating the final theoretical image according to the initial theoretical image includes:

[0074] Performing first upsampling on the initial theoretical image to generate a first intermediate theoretical image;

[0075] Specifically, in the field imaging technology, the resolution of the acquired image depends on the accuracy of the image acquisition device, and the resolution of the image is related to the calculation accuracy of the center offset. When the resolution of the image is high, the calculation accuracy of the center offset is also relatively high; in the related art, due to the limited accuracy of the image acquisition device, it is relatively difficult to improve the calculation accuracy of the center offset by improving the accuracy of the image acquisition device. In this embodiment, the initial theoretical image can be first upsampled to improve the resolution of the image.

[0076] Exemplarily, the initial theoretical image can be first upsampled through the following formulas (1) to (3).

[0077] (1)

[0078] Where f(x) is the original point of upsampling, F(x) is the gray value of the sampling point in the original image, S(x) is the interpolation filter, and △ is the sampling period. Formula (1) represents the interpolation of upsampling the original image.

[0079] (2)

[0080] Where R represents the width of the central region in the interpolation filter.

[0081] F(x, y) = P(x, y)(1 - x)(1 - y) + P(x + 1, y)x(1 - y) + P(x, y + 1)(1 - x)y + P(x + 1, y + 1)xy (3)

[0082] Where F(x, y) is the gray value of the point (x, y) in the upsampled image. P(x, y) is the gray value of the point in the original image that is closest to the interpolation point.

[0083] After generating the first intermediate theoretical image, the final theoretical image can be determined according to the first intermediate theoretical image to improve the calculation accuracy of the center offset.

[0084] Furthermore, after performing the first upsampling process on the initial theoretical image, to ensure that the sizes of the two images for correlation calculation match, the actual image also needs to be upsampled. Specifically, obtaining the final actual image of the exposed substrate includes:

[0085] Collect the initial actual image of the substrate after exposure.

[0086] Specifically, after the exposure of all four sub-areas to be exposed is completed, an image acquisition device can be used to collect the initial actual image of the substrate. The resolution of the initial theoretical image is the same as that of the initial actual image.

[0087] Perform a second upsampling on the initial actual image to obtain a first intermediate actual image.

[0088] Specifically, to avoid the influence of the upsampling process on the correlation calculation between the final actual image and the final theoretical image, the parameters of the second upsampling can be set to be the same as those of the first upsampling. That is to say, the processing steps of the second upsampling also include the above formulas (1) to (3), and the corresponding sampling period △ and the width R of the central region in the interpolation filter are also the same.

[0089] Multiply the parts of each sub-area to be exposed corresponding to the first intermediate actual image by the corresponding weight coefficients and sum them up to obtain a second intermediate actual image; use the second intermediate actual image as the final actual image; among them, the weight coefficient of the part corresponding to the sub-area to be exposed in the first intermediate actual image is positively correlated with the exposure time of the sub-area to be exposed.

[0090] Specifically, in this embodiment, since each sub-area to be exposed needs to be exposed, that is, four exposures are performed, and the exposure times of the four exposures may be different. Therefore, considering the influence of different exposure times on the final actual image, the images corresponding to each sub-area to be exposed can be multiplied by the corresponding weight coefficients. Exemplarily, if the weight coefficient corresponding to the standard exposure time is 1, the weight coefficient corresponding to the sub-area to be exposed is the exposure time of the sub-area to be exposed divided by the standard exposure time. Assume that the second intermediate actual image is P0, the image corresponding to the first sub-area to be exposed is P11, the image corresponding to the second sub-area to be exposed is P21, the image corresponding to the third sub-area to be exposed is P31, and the image corresponding to the fourth sub-area to be exposed is P41. The weight coefficients corresponding to the first sub-area to the fourth sub-area to be exposed are K1, K2, K3, and K4 in sequence, then P0 = P11 * K1 + P21 * K2 + P31 * K3 + P41 * K4. Further, considering the influence brought by image fusion, it can be set that P0 = P11 * K1 * 0.25 + P21 * K2 * 0.25 + P31 * K3 * 0.25 + P41 * K4 * 0.25. Use the second intermediate actual image as the final actual image to further improve the calculation accuracy of the center offset.

[0091] Optionally, in some embodiments, generating a final theoretical image based on the first intermediate theoretical image includes: using the first intermediate theoretical image as the final theoretical image. That is, directly using the initial theoretical image after the first upsampling process as the final theoretical image, and increasing the resolution of the image through the first upsampling process.

[0092] Optionally, in some other embodiments, generating a final theoretical image based on the first intermediate theoretical image includes: performing at least one of stage orthogonal motion correction, reticle alignment correction, and objective magnification correction on the first intermediate theoretical image to obtain a second intermediate theoretical image; using the second intermediate theoretical image as the theoretical image.

[0093] Specifically, when the lithography apparatus exposes the substrate, it will actually be affected by stage orthogonal motion deviation, reticle alignment deviation, objective magnification deviation, etc. In the related art, the calculation of the center offset in the field imaging technology does not consider the influence of the above deviations, resulting in poor calculation accuracy of the center offset. In this embodiment, when calculating the theoretical image, the influence of the above deviations is considered to further improve the calculation accuracy of the center offset. More specifically, the orthogonal motion deviation of the stage can be corrected by the first correction formula, and the first correction formula is:

[0094] ρ(y) = y / cosθ (4)

[0095] where θ can be obtained from the measurement of the stage orthogonality. y represents the y coordinate on the initial theoretical image; ρ(y) represents the corrected y coordinate. It should be noted that the points on the initial theoretical image have x coordinates and y coordinates, and the x coordinates do not need to be corrected.

[0096] The reticle alignment correction can be corrected by the second correction formula, and the second correction formula is:

[0097] ξ(y) = y + J(x, y) (5)

[0098] where J is the fixed deviation value corresponding to the reticle, which is fixed when the reticle leaves the factory. ξ(y) represents the corrected y coordinate.

[0099] The objective magnification correction can be directly multiplied by the magnification correction coefficient KI, and the magnification correction coefficient KI can be obtained from the objective magnification measurement part.

[0100] Preferably, the stage orthogonal motion correction, reticle alignment correction, and objective magnification correction can be performed on the first intermediate theoretical image to obtain the second intermediate theoretical image, thereby greatly improving the calculation accuracy of the center offset. After the above corrections, the final theoretical image can be expressed as: P5 = ρ(P) * ξ(P) * KI. Where P5 represents the coordinate of the point P on the initial theoretical image in the final theoretical image after correction.

[0101] Optionally, in some other embodiments, the influence caused by errors due to environmental parameters can also be applied to the first intermediate theoretical image. For example, when there are changes in temperature, pressure, etc., there will also be a certain deformation in the final actual image. Therefore, temperature and pressure corrections can be performed on the first intermediate theoretical image, and corresponding correction coefficients can be multiplied during the correction. Specifically, the specific correction coefficients can be obtained through testing. In this embodiment, the calculation process of the center offset takes into account the influence brought by each process during actual lithography, thereby further improving the calculation accuracy of the center offset.

[0102] Optionally, calculating the center offset by performing correlation matching between the region of interest of the final theoretical image and the final actual image includes: when the offset amount takes values in the region of interest, the offset amount corresponding to the maximum correlation is used as the center offset. The correlation can be calculated by the following formula:

[0103] (6)

[0104] wherein, the upper and lower limits of i and j form the region of interest. P0 is the final actual image, and P5 is the final theoretical image. When R(m, n) is the largest, the values of m and n represent the final center offset.

[0105] Optionally, referring to Figure 5 , in the above embodiment, the region of interest includes sub-regions of interest SROI corresponding to each sub-exposure area to be exposed. The area of the sub-region of interest SROI is smaller than the area of the corresponding sub-exposure area to be exposed. The sub-region of interest SROI is a centrosymmetric figure, and the sizes and shapes of the sub-regions of interest SROI are the same.

[0106] Specifically, the size of each sub-exposure area to be exposed is usually relatively large. For example, its outer contour is located within a square with a side length of 500 microns. In this embodiment, the region of interest can be selected to reduce the calculation amount, and a centrosymmetric figure is selected in each sub-exposure area to be exposed, and the shapes and sizes of the sub-regions of interest SROI are exactly the same, so that the region of interest can retain the different parts between the final theoretical image and the final actual image to a greater extent, improving the calculation accuracy of the center offset. Of course, in some other embodiments, the region of interest can also be an overall region, which includes each sub-exposure area to be exposed, and the area of the region of interest is smaller than the area of the final theoretical image.

[0107] Based on the same inventive concept, the present invention also provides a measuring device for the center offset of an objective lens in a lithography apparatus, which is used to execute the method for measuring the center offset of an objective lens in a lithography apparatus provided in any embodiment of the present invention. As Figure 7 shown, Figure 7Schematic structural diagram of a measurement device for the center offset of an objective lens in a lithography apparatus provided by an embodiment of the present invention. The measurement device includes:

[0108] A first alignment module 21 for aligning the center of a preset pattern on a mask plate with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure;

[0109] A second alignment module 22 for placing a substrate to be exposed on a moving stage and aligning the center of the moving stage with the theoretical center of the objective lens;

[0110] A moving module 23 for moving the substrate to expose a preset exposure area of the substrate; wherein, the preset exposure area is centrosymmetric and includes at least four sub-exposure areas having the same distance from the center of the moving stage;

[0111] An acquisition module 24 for acquiring the final actual image of the exposed substrate and acquiring the corresponding final theoretical image after the substrate is exposed;

[0112] A processing module 25 for performing correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least a part of the final theoretical image corresponding to the preset exposure area.

[0113] The specific working process of the measurement device for the center offset of the objective lens in the lithography apparatus can refer to the description of the measurement method part of the present invention, which will not be elaborated here. The measurement device provided by this embodiment designs a preset pattern on the mask plate, exposes the preset exposure area that is centrosymmetric on the substrate to obtain the final actual image, and performs correlation calculation with the final actual image after obtaining the final theoretical image to calculate the center offset. There are more points used for calculation in the image, and the calculation accuracy of the center offset is higher.

[0114] It should be understood that various forms of the processes shown above can be used, reordering, adding or deleting steps. For example, the steps described in the present invention can be executed in parallel, sequentially, or in different orders, as long as the desired results of the technical solution of the present invention can be achieved. No limitation is imposed herein.

[0115] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for measuring the offset of the center of an objective lens in a lithography apparatus, characterized in that, Including: Align the center of a preset pattern on the reticle with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure; Place the substrate to be exposed on the stage, and align the center of the stage with the theoretical projection center of the objective lens; Move the substrate to expose a preset area to be exposed on the substrate; wherein, the preset area to be exposed is centrosymmetric and includes at least four sub-areas to be exposed with the same distance from the center of the stage; Obtain the final actual image of the substrate after exposure, and obtain the corresponding final theoretical image of the substrate after exposure; Perform correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least a part of the final theoretical image corresponding to the preset area to be exposed; Wherein, performing correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset includes: when the offset is taken within the region of interest, taking the offset corresponding to the maximum correlation as the center offset; the correlation is calculated by the following formula: ； Wherein, the upper and lower limits of i and j form the region of interest, P0 is the final actual image, P5 is the final theoretical image, and when R(m, n) is the largest, the values of m and n represent the final center offset.

2. The method for measuring the offset of the objective lens center in the lithography apparatus according to claim 1, characterized in that, The obtaining of the corresponding final theoretical image of the substrate after exposure includes: Generate an initial theoretical image according to the exposure parameters of the substrate; Generate the final theoretical image according to the initial theoretical image.

3. The method for measuring the offset of the objective lens center in the lithography apparatus according to claim 2, characterized in that, The generating of the final theoretical image according to the initial theoretical image includes: Taking the initial theoretical image as the final theoretical image; Or, performing first upsampling on the initial theoretical image to generate a first intermediate theoretical image; Generate the final theoretical image according to the first intermediate theoretical image.

4. The method for measuring the offset of the objective lens center in the lithography apparatus according to claim 3, wherein The generating of the final theoretical image according to the first intermediate theoretical image includes: Taking the first intermediate theoretical image as the final theoretical image; Or, performing at least one of stage orthogonal movement correction, reticle scale line correction, and objective lens magnification correction on the first intermediate theoretical image to obtain a second intermediate theoretical image; Taking the second intermediate theoretical image as the theoretical image.

5. The method for measuring the offset of the objective lens center in the lithography apparatus according to claim 4, characterized in that, The performing of at least one of stage orthogonal movement correction, reticle scale line correction, and objective lens magnification correction on the first intermediate theoretical image to obtain a second intermediate theoretical image includes: Performing stage orthogonal movement correction, reticle scale line correction, and objective lens magnification correction on the first intermediate theoretical image to obtain the second intermediate theoretical image.

6. The method for measuring the offset of the objective lens center in a lithography apparatus according to claim 3, characterized in that, The generating of the final theoretical image according to the initial theoretical image includes: performing first upsampling on the initial theoretical image to generate a first intermediate theoretical image; generating the final theoretical image according to the first intermediate theoretical image; The obtaining of the final actual image of the substrate after exposure includes: Collect the initial actual image of the substrate after exposure; Perform second upsampling on the initial actual image to obtain a first intermediate actual image; Multiply the parts of the first intermediate actual image corresponding to each sub-exposure area by the corresponding weight coefficients and sum them up to obtain a second intermediate actual image; Use the second intermediate actual image as the final actual image; wherein, the weight coefficient of the part of the first intermediate actual image corresponding to the sub-exposure area is positively correlated with the exposure time of the sub-exposure area.

7. The method for measuring the offset of the objective lens center in the lithography apparatus according to claim 6, characterized in that, The parameters of the first upsampling and the second upsampling are the same.

8. The method for measuring the offset of the objective lens center in a lithography apparatus according to claim 1, characterized in that, The region of interest includes sub-regions of interest corresponding to each of the sub-exposure areas; the area of the sub-region of interest is smaller than the area of the corresponding sub-exposure area, the sub-region of interest is a centrosymmetric figure, and the sizes and shapes of the sub-regions of interest are the same.

9. The method for measuring the center offset of an objective lens in a lithographic apparatus according to claim 1, characterized in that The calculating the center offset by performing correlation matching between the region of interest of the final theoretical image and the final actual image includes: When the offset amount is taken within the region of interest, the offset amount corresponding to the maximum correlation is used as the center offset.

10. A measuring device for the center offset of an objective lens in a lithographic apparatus, which is used to perform the method for measuring the center offset of the objective lens in the lithographic apparatus according to any one of claims 1-9, characterized in that, The measuring device for the center offset of the objective lens in a lithography apparatus includes: A first alignment module for aligning the center of a preset pattern on the mask with the center of the objective lens; wherein, the preset pattern is a centrosymmetric figure; A second alignment module for placing the substrate to be exposed on a moving stage and aligning the center of the moving stage with the theoretical projection center of the objective lens; A moving module for moving the substrate to expose a preset exposure area of the substrate; wherein, the preset exposure area is centrosymmetric and includes at least four sub-exposure areas having the same distance from the center of the moving stage; An acquisition module for acquiring the final actual image of the substrate after exposure and acquiring the corresponding final theoretical image of the substrate after exposure; A processing module for performing correlation matching between the region of interest of the final theoretical image and the final actual image to calculate the center offset; wherein, the region of interest includes at least a part of the final theoretical image corresponding to the preset exposure area.

Images