A measurement system and method for center positioning of a motion platform

Abstract

The present invention relates to the field of wafer defect detection, and provides a measurement system and method for centering a motion platform. The system includes a motion platform, which includes a Y-axis motion platform and a Theta rotation platform. The Y-axis motion platform moves linearly along the Y-axis direction, and the Theta rotation platform rotates around the rotation center point O. An incident optical path that focuses a light spot on the wafer to form a scanning center point O<supgt;,< / supgt>. An imaging optical path that collects the energy of scattered light or reflected light on the wafer to form a scanning image. And a wafer arranged on the Theta rotation platform, with a characteristic pattern provided on the wafer. The offset between the rotation center point O and the scanning center point O<supgt;,< / supgt> is determined by scanning the characteristic pattern and calculating coordinates, and the motion platform is adjusted to align the rotation center point O with the scanning center point O<supgt;,< / supgt>. The present invention can achieve the alignment of the optical scanning point and the center point of the rotation platform in the wafer defect detection system, effectively improving the accuracy of the wafer defect detection result.

Description

Technical Field

[0001] The present invention relates to the field of wafer defect detection, and in particular to a measurement system and method for center positioning of a motion platform. Background Art

[0002] Wafer defect detection is an important part of the wafer manufacturing process. In recent years, wafer defect detection methods based on optical scanning imaging have been widely used. This detection method usually requires focusing the light spot on the surface or inside of the wafer, and then scanning the wafer through a moving stage or optical head, and synchronously receiving light reflection or light scattering signals to generate a wafer image. Furthermore, by analyzing the image data of the wafer image, effective detection and classification of wafer defects can be achieved.

[0003] In the process of scanning the wafer, in order to obtain accurate scanning results, it is necessary to first calibrate the platform system used for wafer scanning. Common platform systems in the prior art include XY scanning platforms and Y-Theta motion platforms. Compared with XY scanning platforms, Y-Theta motion platforms have the advantages of continuous scanning and high yield, so they are widely used. However, the Y-Theta motion platform also has the problem of slightly poor positioning accuracy. Even if the adjustment of the Y-axis of the Y-Theta motion platform and the central rotation axis of the Theta rotation table is ideal, the adjustment deviation of the optical virtual scanning point will still affect the imaging. And unlike the XY scanning platform, the center deviation of the scanning point generated by the Y-Theta motion platform is difficult to eliminate by correcting the image later. Therefore, the center positioning accuracy of the Y-Theta motion platform will directly affect the position accuracy of the defect detection, and it is necessary to propose a measurement system and method that can effectively and easily perform center positioning on the Y-Theta motion platform. Summary of the invention

[0004] In order to at least partially solve the above problems in the prior art, the present invention provides a measurement system for center positioning of a motion platform, comprising:

[0005] A motion platform, comprising a Y-axis motion platform and a Theta rotation platform, wherein the Y-axis motion platform is configured to move linearly along the Y-axis direction, and the Theta rotation platform is configured to rotate along a rotation center point O;

[0006] The incident light path is configured to focus the light spot on the wafer to form a scanning center point O , ;

[0007] an imaging optical path configured to collect energy of scattered light or reflected light on the wafer to form a scan image; and

[0008] The wafer is arranged on the Theta rotating platform, and a characteristic pattern is provided on the wafer, wherein the rotation center point O is determined by scanning the characteristic pattern and calculating the coordinates thereof. , and adjusting the motion platform so that the rotation center point O is aligned with the scanning center point O. , alignment.

[0009] In one embodiment of the present invention, the incident light path includes an incident light power control module, a polarization control module, a beam shaping module and a spot scanning module, wherein the incident light path is incident obliquely or vertically from the surface of the wafer.

[0010] In one embodiment of the present invention, it is provided that the imaging optical path includes an optical power control module, a polarization control module, a beam shaping module and a photoelectric conversion module, wherein the imaging optical path is configured to perform single-channel acquisition or multi-channel acquisition.

[0011] In one embodiment of the present invention, it is provided that a platform coordinate system XOY based on the rotation center point O and a platform coordinate system XOY based on the scanning center point O are constructed. , Scanning image coordinate system X_laserO , Y_laser, to align the rotation center point O with the scanning center point O , The offset between the platform coordinate system and the scanned image coordinate system is represented by X_offset representing the offset in the X-axis direction and Y_offset representing the offset in the Y-axis direction, wherein the first feature point A(R,θ) in the platform coordinate system is plotted against the corresponding second feature point A(R,θ) in the scanned image coordinate system. , (R , ,θ , ) is expressed as follows:

[0012] ;

[0013] Where R represents the distance between the first feature point A and the rotation center point O, θ represents the angle between OA and the negative Y-axis direction of the platform coordinate system XOY, and R , Indicates the second feature point A , The detected position A ,, With scanning center point O , The distance between , OA , OA ,, The angle between

[0014] The offset X_offset in the X-axis direction and the offset Y_offset in the Y-axis direction between the platform coordinate system and the scanned image coordinate system will cause distortion of the scanned image. When R < X_offset, the first feature point A will be missed during scanning; when Y_offset is less than zero, and when, the first feature point A will be missed during scanning; when Y_offset is greater than zero, and when, the first feature point A will be scanned repeatedly. The mapping relationship between the coordinates of the repeatedly scanned feature points and the platform coordinate system is expressed by the following formula:

[0015] .

[0016] In an embodiment of the present invention, it is stipulated that when the wafer is placed on the Theta rotation platform, there are offsets Xc and Yc between the center Oc of the wafer and the rotation center point O. The offset between the center Oc of the wafer and the rotation center point O will cause translation of the scanned image.

[0017] In an embodiment of the present invention, it is stipulated that the feature pattern includes a first feature pattern and a second feature pattern. The first feature pattern is a circle with a first radius, and the second feature pattern is a circle with a second radius. Scanning and coordinate calculation are performed on the feature pattern to determine the offset between the rotation center point O and the scanning center point O , and adjusting the motion platform so that the rotation center point O and the scanning center point O , alignment includes the following steps:

[0018] Scanning the feature pattern area of the wafer to generate a calibration image, and determining the position coordinates of the first feature pattern and the second feature pattern in the calibration image;

[0019] Calculating the offset Y_offset in the Y-axis direction between the scanning center point O , and the rotation center point O based on the position coordinates of the first feature pattern;

[0020] Calculating the offset X_offset in the X-axis direction between the scanning center point O , and the rotation center point O based on the position coordinates of the second feature pattern;

[0021] Judging whether the offsets of the scanning center point O , in the X-axis direction and the Y-axis direction from the rotation center point O are within the set range;

[0022] When the scanning center point O ,When the offset from the rotation center point O in the X-axis direction and / or Y-axis direction is not within the set range, the scanning center point O is adjusted according to the calculation results. , and\or the position of the rotation center point O; and

[0023] When scanning center point O , The center positioning of the motion platform is completed when the offset from the rotation center point O in the X-axis direction and the Y-axis direction is within the set range.

[0024] In one embodiment of the present invention, it is provided that the scanning center point O is calculated based on the position coordinates of the first characteristic pattern. , The offset Y_offset from the rotation center point O in the Y axis direction includes the following steps:

[0025] The scanning result of the first characteristic pattern is analyzed, wherein the standard circular curve of the first characteristic pattern fluctuates due to deviation in the R-Theta view, and the corresponding relationship between the maximum value and the minimum value of the standard circular curve of the first characteristic pattern is expressed as follows:

[0026] ;

[0027] because , , the corresponding relationship between the maximum and minimum values ​​of the standard circular curve of the first characteristic pattern is approximately expressed as follows:

[0028] ;as well as

[0029] The scanning center point O is calculated based on the correspondence between the maximum and minimum values ​​of the standard circular curve of the first characteristic pattern. , The offset from the rotation center point O in the Y-axis direction is expressed as follows:

[0030] .

[0031] In one embodiment of the present invention, it is provided that the scanning center point O is calculated based on the position coordinates of the second characteristic pattern. , The offset X_offset from the rotation center point O in the X-axis direction includes the following steps:

[0032] The scanning result of the second characteristic pattern is analyzed, wherein the standard circular curve of the second characteristic pattern fluctuates due to deviation in the R-Theta view, and the corresponding relationship between the maximum value and the minimum value of the standard circular curve of the second characteristic pattern is expressed as follows:

[0033] ;as well as

[0034] Based on the calculated Y_offset and , calculate the scanning center point O , The offset from the rotation center point O in the X-axis direction is expressed as follows:

[0035] .

[0036] In one embodiment of the present invention, the characteristic pattern includes a third characteristic pattern, the third characteristic pattern is a dot grid pattern, wherein the characteristic pattern is scanned and the coordinates are calculated to determine the rotation center point O and the scanning center point O , and adjusting the motion platform so that the rotation center point O is aligned with the scanning center point O. , Alignment consists of the following steps:

[0037] Scanning and imaging the third characteristic pattern;

[0038] The scanning result of the third characteristic pattern is analyzed, wherein when the tangential distortion of the third characteristic pattern exceeds the set range, it indicates that the rotation center point O is aligned with the scanning center point O. , There is an offset X_offset in the X-axis direction. When the radial distortion of the third characteristic pattern exceeds the set range, it means that the rotation center point O is different from the scanning center point O. , There is an offset Y_offset in the Y-axis direction;

[0039] When the tangential distortion and / or radial distortion of the scanned image exceeds a set range, adjusting the offset of the scanning center point and the rotating platform center point based on the calculation result; and

[0040] When the tangential distortion and radial distortion of the scanned image do not exceed the set range, the platform center positioning adjustment is ended.

[0041] The present invention also provides a method for measuring the center positioning of a motion platform, which comprises the following steps:

[0042] Providing a wafer, wherein the wafer is provided with a characteristic pattern;

[0043] Placing the wafer on the Theta rotating platform of the motion platform, wherein the motion platform includes a Y-axis motion platform and a Theta rotating platform, the Y-axis motion platform is configured to move linearly along the Y-axis direction, and the Theta rotating platform is configured to rotate along a rotation center point O;

[0044] The incident light path focuses the light spot on the wafer to form the scanning center point O , ;

[0045] Collecting the energy of scattered light or reflected light on the wafer through an imaging optical path to form a scanning image; and

[0046] The rotation center point O and the scanning center point O are determined by scanning the characteristic pattern and calculating the coordinates. , and adjusting the motion platform so that the rotation center point O is aligned with the scanning center point O. , alignment.

[0047] The present invention has at least the following beneficial effects: The present invention proposes a measurement system and method for center positioning of a motion platform, which can realize the alignment of the optical scanning point and the center point of the rotating platform in the wafer defect detection system, thereby effectively improving the accuracy of the wafer defect detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] To further illustrate the advantages and features of various embodiments of the present invention, a more detailed description of various embodiments of the present invention will be presented with reference to the accompanying drawings. It will be understood that these drawings only depict typical embodiments of the present invention and are therefore not to be considered as limiting the scope thereof. In the accompanying drawings, for clarity, identical or corresponding parts will be represented by identical or similar reference numerals.

[0049] Figure 1 A schematic diagram of a measurement system for center positioning of a motion platform in one embodiment of the present invention is shown.

[0050] Figure 2 A schematic diagram showing an image coordinate system and a platform coordinate system of a measurement system in an embodiment of the present invention is shown.

[0051] Figure 3 A schematic diagram showing a characteristic pattern in a wafer coordinate system and a platform coordinate system in one embodiment of the present invention is shown.

[0052] FIG. 4 is a schematic flow chart showing a method for measuring the center positioning of a motion platform in an embodiment of the present invention.

[0053] Figure 5a -d is a schematic diagram showing the scanning results of a characteristic pattern in one embodiment of the present invention.

[0054] Figure 6 A schematic diagram of a characteristic pattern in a wafer coordinate system and a platform coordinate system according to another embodiment of the present invention is shown.

[0055] 7a-c are schematic diagrams showing scanning results of a characteristic image affected by deviations in the X and Y directions in another embodiment of the present invention.

[0056] Figure 8 A schematic flow chart of a method for measuring the center positioning of a motion platform in another embodiment of the present invention is shown.

[0057] Figure 9a -c is a schematic diagram showing the scanning results of a feature image in another embodiment of the present invention. DETAILED DESCRIPTION

[0058] It should be noted that the components in the figures may be shown exaggeratedly for the sake of illustration and are not necessarily true to scale. In the figures, identical or functionally identical components are provided with the same reference numerals.

[0059] In the present invention, unless otherwise specified, "arranged on...", "arranged above..." and "arranged above..." do not exclude the existence of an intermediate between the two. In addition, "arranged on or above..." merely indicates the relative positional relationship between two components, and in certain cases, such as after reversing the product direction, it can also be converted into "arranged below or below...", and vice versa.

[0060] In the present invention, each embodiment is only intended to illustrate the aspects of the present invention and should not be construed as limiting.

[0061] In the present invention, unless otherwise specified, the quantifiers "a", "an" and "an" do not exclude the presence of a plurality of elements.

[0062] It should also be noted that in the embodiments of the present invention, for the sake of clarity and simplicity, only a portion of the parts or components may be shown, but those of ordinary skill in the art will understand that under the teachings of the present invention, the required parts or components may be added according to the needs of the specific scenario. In addition, unless otherwise specified, the features in different embodiments of the present invention may be combined with each other. For example, a feature in the second embodiment may be used to replace a corresponding or functionally identical or similar feature in the first embodiment, and the resulting embodiment also falls within the disclosure scope or recorded scope of the present application.

[0063] It should also be noted that within the scope of the present invention, the terms "same", "equal", "equal to" and the like do not mean that the values ​​of the two are absolutely equal, but allow a certain reasonable error, that is, the terms also cover "substantially the same", "substantially equal", "substantially equal to". By analogy, in the present invention, the terms "perpendicular to", "parallel to" and the like indicating directions also cover the meanings of "substantially perpendicular to" and "substantially parallel to".

[0064] In addition, the numbering of the steps of the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps can be executed in different orders.

[0065] The present invention will be further described below in conjunction with specific embodiments with reference to the accompanying drawings.

[0066] Figure 1FIG. 2 is a schematic diagram showing a measurement system for center positioning of a motion platform in one embodiment of the present invention. Figure 1 As shown, the measurement system includes a Y-axis motion platform 101 , a Theta rotation platform 102 , a wafer 103 , an incident light path 104 , and an imaging light path 105 .

[0067] The Y-axis motion platform 101 is configured to move linearly along the Y-axis direction, and the Theta rotation platform 102 is configured to rotate along the rotation center point O, wherein the Y-axis motion platform 101 and the Theta rotation platform 102 can be integrated together or separately arranged.

[0068] The wafer 103 is arranged on the Theta rotating platform 102 , wherein the center of the wafer 103 may coincide with the center of the Theta rotating platform 102 , or may be offset.

[0069] The incident light path 104 is configured to focus the light spot on the surface of the wafer 103 and form a scanning center point O , ,exist Figure 1 The incident light path 104 is shown in a simplified manner, and may include an incident light power control module, a polarization control module, a beam shaping module, and a spot scanning module, wherein the incident light path 104 may be obliquely incident or vertically incident.

[0070] The imaging optical path 105 is configured to collect the energy of scattered light or reflected light and form a detection optical channel. Figure 1 The imaging optical path 105 is shown in a simplified manner, and may include a collection light power control module, a polarization control module, a beam shaping module, and a photoelectric conversion module, etc., wherein the imaging optical path 105 may be a single-channel collection or a multi-channel collection.

[0071] Figure 2 FIG. 1 is a schematic diagram showing an image coordinate system and a platform coordinate system of a measurement system in one embodiment of the present invention. Figure 2 As shown, the platform coordinate system XOY based on the rotation center point O and the platform coordinate system XOY based on the scanning center point O , Scanning image coordinate system X_laserO , There may be deviations between X_offset and Y_offset. For the first feature point A(R,θ) in the platform coordinate system, there is a corresponding second feature point A in the scanned image coordinate system. , (R , ,θ , ), where the first feature point A and the second feature point A ,The mapping relationship between them can be expressed as follows:

[0072]

[0073] Where, R represents the distance between the first feature point A and the rotation center point O, θ represents the angle between OA and the negative Y-axis direction of the platform coordinate system XOY, and R , Indicates the second feature point A , The detected position A ,, With scanning center point O , The distance between , OA , OA ,, The angle between the first feature point A and the second feature point A , It is the same point in space, but in the spatial coordinate system and the scanning coordinate system, the mapped coordinates are inconsistent due to position deviation.

[0074] Due to the existence of the deviations X_offset and Y_offset, the scanned image will be distorted. When the position coordinate R of the first feature point A < X_offset, the measurement system will miss the feature point. When Y_offset is less than zero and When Y_offset is greater than zero, and When , the measurement system will repeatedly scan the feature point, where the mapping relationship between the coordinates of the repeatedly scanned feature point and the platform coordinate system can be expressed as follows:

[0075] .

[0076] Figure 3 FIG. 1 is a schematic diagram showing a characteristic pattern in a wafer coordinate system and a platform coordinate system in one embodiment of the present invention. Figure 3 As shown, when the wafer 103 is placed on the Theta rotating platform 102, there may be deviations Xc and Yc between the center Oc of the wafer 103 and the center O of the Theta rotating platform 102. Figure 3 Taking the illustrated case as an example, the deviation may be -250um, 350um. The wafer 103 may be provided with a first characteristic pattern 301 and a second characteristic pattern 302, wherein the first characteristic pattern 301 may be a circle with a larger radius, and the second characteristic pattern 302 may be a circle with a smaller radius. The deviation between the center of the wafer 103 and the center of the Theta rotating platform 102 will not cause image distortion, but will cause image translation.

[0077] FIG4 is a schematic diagram showing a flow chart of a method for measuring the center positioning of a motion platform in one embodiment of the present invention. Figure 4 As shown, the method comprises the following steps:

[0078] Step 401 : Scan the characteristic pattern area of ​​the wafer 103 to generate a calibration image, and determine the position coordinates of the first characteristic pattern 301 in the calibration image.

[0079] Step 402: Calculate the scanning center point O based on the position coordinates of the first characteristic pattern 301. , The offset from the rotation center O in the Y direction.

[0080] Step 403: Determine the position coordinates of the second characteristic pattern 302 in the calibration image.

[0081] Step 404: Calculate the scanning center point O based on the position coordinates of the second characteristic pattern 302. , The offset from the rotation center O in the X-axis direction.

[0082] Step 405: Determine the scanning center point O , Whether the offset from the rotation center point O in the X-axis direction and the Y-axis direction is within the set range.

[0083] Step 406: When scanning center point O , When the offset from the rotation center point O in the X-axis direction and / or Y-axis direction is not within the set range, the scanning center point O is adjusted according to the calculation results. , and\or the position of the rotation center point O for adjustment.

[0084] Step 407: When scanning center point O , The center positioning of the motion platform is completed when the offset from the rotation center point O in the X-axis direction and the Y-axis direction is within the set range.

[0085] The steps of the method are described in detail below with reference to the accompanying drawings.

[0086] In step 401, a first characteristic pattern 301 on the surface of the wafer 103 is scanned and imaged. The first characteristic pattern 301 may be a circle with a radius R of 50 mm, wherein the Y-axis motion platform 101 and the Theta rotation platform 102 may be moved to scan at the center point O , High-precision scanning is performed within the range of 50mm±2.5mm.

[0087] Figure 5a -d shows a schematic diagram of the scanning result of a characteristic pattern in one embodiment of the present invention. Figure 5a FIG. 3 shows a schematic diagram of the first characteristic pattern 301 in the scanned image coordinate system. Figure 5bA schematic diagram of converting the scanned image of the first characteristic pattern 301 into an XY rectangular coordinate system is shown, wherein the gray curve represents the scan result with deviations X_offset, Y_offset, Xc and Yc, and the black curve represents the ideal scan result with all deviations being zero.

[0088] In step 402, the scanning result of the first characteristic pattern 301 is analyzed. The standard circular curve of the first characteristic pattern 301 fluctuates in the R-Theta view due to deviation. The corresponding relationship between the maximum value and the minimum value is expressed as follows:

[0089] .

[0090] When the R radius is larger, , , the corresponding relationship between the maximum and minimum values ​​can be approximately expressed as follows:

[0091] .

[0092] According to the corresponding relationship between the maximum value and the minimum value, the scanning center point O can be calculated. , The offset from the rotation center point O in the Y-axis direction is expressed as follows:

[0093] .

[0094] In step 403, the second characteristic pattern 302 on the surface of the wafer 103 is scanned and imaged. The second characteristic pattern 302 is a circle with a smaller radius than the first characteristic pattern 301, and its radius is 1 mm. The Y-axis motion platform 101 and the Theta rotation platform 102 can be moved to scan the center point O. , High-precision scanning is performed within the range of 0mm-5mm. Figure 5c FIG. 3 shows a schematic diagram of the second characteristic pattern 302 in the scanned image coordinate system. Figure 5d A schematic diagram of converting the scanned image of the second characteristic pattern into an XY rectangular coordinate system is shown, wherein the gray curve represents the scanned result with deviations X_offset, Y_offset, Xc and Yc, and the black curve represents the scanned result in an ideal state where all deviations are zero. Since the radius of the second characteristic pattern 302 is small, the scanned image is greatly affected by the deviation X_offset in the X-axis direction, resulting in obvious distortion.

[0095] In step 404, the scanning result of the second characteristic pattern 302 is analyzed. The standard circular curve of the second characteristic pattern 302 fluctuates in the R-Theta view due to deviation, and the corresponding relationship between the maximum and minimum values ​​is the same as that of the first characteristic pattern 302, which is expressed as the following formula:

[0096] .

[0097] According to the calculated Y_offset and , the scanning center point O can be calculated , The offset from the rotation center point O in the X-axis direction is expressed as follows:

[0098] .

[0099] In step 405, the values ​​of the deviations X_offset and Y_offset in the X-axis direction and the Y-axis direction are judged. If the values ​​are not within the set range, step 406 is entered. Based on the calculation results, the position of the motion platform is adjusted by motion control or manual mechanical adjustment, and the position of the scanning spot can also be optically adjusted. The deviation between the scanning center point and the center point of the rotating platform is measured and positioned again through steps 401-405. If the values ​​are within the set range, step 407 is entered, and the platform center positioning adjustment is completed. In this embodiment, the measurement value and positioning accuracy of the deviations X_offset and Y_offset are better than 5um.

[0100] Figure 6 FIG. 2 shows a schematic diagram of a characteristic pattern in another embodiment of the present invention in the wafer coordinate system and the platform coordinate system. Figure 6 As shown, the third characteristic pattern 601 is a grid point pattern with a side length of 200um, wherein there may be deviations Xc, Yc and angle deviations θc between the wafer coordinate system and the platform coordinate system, and a set of parameter values ​​of the deviation may be -250um, 350um and The measurement method based on the third characteristic pattern 601 has no strict requirements on the placement deviation Xc, Yc and the angle deviation θc in the wafer coordinate system, and allows the wafer to be analyzed under non-center symmetrical placement conditions to obtain the values ​​of the deviations X_offset and Y_offset.

[0101] 7a-c are schematic diagrams showing scanning results of a characteristic image affected by deviations in the X and Y directions in another embodiment of the present invention. Figure 7aThe figure shows a schematic diagram of the third characteristic pattern 601 under the influence of the X-direction deviation between the scanning center point and the rotating platform center point, which is displayed in the scanning image coordinate system after image conversion to the XY rectangular coordinate system. The gray curve is the scanning result after considering Xc, Yc and the angle deviation θc, and the black curve is the ideal state scanning result when all deviations are zero. X_offset will produce tangential distortion to the third characteristic pattern 601. When X_offset is greater than zero, it will produce distortion in the clockwise direction, and when X_offset is less than zero, it will produce distortion in the counterclockwise direction. Figure 7a The X_offset of the third characteristic pattern 601 is shown to be 525 um. By analyzing the scanning results, it can be seen that a straight line closest to the center point will become a curve due to distortion, and the Y positive end and the Y negative end of the straight line will have a deviation, and the deviation is approximately equal to 2*X_offset. Figure 7b FIG. 6 is a schematic diagram showing the third characteristic pattern 601 after the offset adjustment in the scanning image coordinate system after the image is converted into the XY rectangular coordinate system. Figure 7b As shown in the figure, after the offset adjustment, X_offset is reduced to 24um. The gray curve is the scanning result after considering Xc, Yc and angle deviation θc. The black curve is the ideal state scanning result with all deviations zero. By adjusting and iterating the scanning results, the deviation X_offset can be reduced to approach the ideal result.

[0102] Figure 8 FIG. 2 is a flow chart showing a method for measuring the center positioning of a motion platform in another embodiment of the present invention. Figure 8 As shown, the measurement method for positioning the center of the motion platform based on the third characteristic pattern 601 includes the following steps:

[0103] Step 801 : Scanning and imaging the third characteristic pattern 601 on the surface of the wafer by a measuring system, wherein the measuring system can scan with high precision within the range of 0 mm to 5 mm using a movable platform.

[0104] Step 802: Analyze the scanning result of the third characteristic pattern 601 to obtain the offset information of the scanning center point and the rotating platform center point in the X and Y directions.

[0105] Step 803: Determine whether there is obvious tangential distortion in the image. If there is, it indicates that there is obvious X-direction deviation X_offset.

[0106] Step 804: determine whether there is obvious radial distortion in the image. If there is, it indicates that there is obvious Y-direction deviation Y_offset.

[0107] Step 805: When there is obvious tangential distortion and / or obvious radial distortion in the image, the offset of the scanning center point and the rotating platform center point is adjusted based on the calculation result.

[0108] Step 806: When there is no obvious tangential distortion and radial distortion in the image, the platform center positioning adjustment is ended.

[0109] Figure 9a -c is a schematic diagram showing the scanning results of a feature image in another embodiment of the present invention. Figure 9a FIG. 6 shows a schematic diagram of the third characteristic pattern 601 in the scanning image coordinate system after image conversion to the XY rectangular coordinate system under the combined influence of the deviations in the two directions of the scanning center point and the rotating platform center point. Figure 9a Analysis shows that there is obvious tangential distortion, but no obvious radial distortion. Figure 9b The schematic diagram shows the third characteristic pattern 601 after one offset adjustment, which is displayed in the scanned image coordinate system after image conversion to the XY rectangular coordinate system, wherein there is obvious tangential distortion and slight radial distortion. Fig.9c The schematic diagram shows that after two offset adjustments, the characteristic pattern 601 in the scanning image coordinate system is converted into an XY rectangular coordinate system, wherein there is a slight tangential distortion and radial distortion. If it is determined in step 803 and step 804 that the tangential distortion and radial distortion of the image are both within the set range, then step 806 is entered to end the platform center positioning adjustment.

[0110] The above-mentioned measurement method of the center positioning of the motion platform can theoretically adjust the system to the optimal state of the optical scanning system. Of course, the measurement value of the deviation X_offset, Y_offset and the positioning accuracy are still limited by the system scanning and imaging accuracy.

[0111] Although various embodiments of the present invention are described above, it should be understood that they are presented as examples only and not as limitations. It is obvious to those skilled in the relevant art that various combinations, modifications and changes can be made thereto without departing from the spirit and scope of the present invention. Therefore, the breadth and scope of the present invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should only be defined according to the attached claims and their equivalents.

Claims

1. A measurement system for center positioning of a motion platform, characterized in that: include: A motion platform, comprising a Y-axis motion platform and a Theta rotation platform, wherein the Y-axis motion platform is configured to move linearly along the Y-axis direction, and the Theta rotation platform is configured to rotate along a rotation center point O; An incident light path, configured to focus the light spot on the wafer to form a scanning center point O′; An imaging optical path configured to collect energy of scattered light or reflected light on the wafer to form a scan image; as well as A wafer is arranged on the Theta rotating platform, and a feature pattern is provided on the wafer, wherein the feature pattern includes a first feature pattern and a second feature pattern, wherein the first feature pattern is a circle with a first radius, and the second feature pattern is a circle with a second radius, wherein the offset between the rotation center point O and the scanning center point O′ is determined by scanning the feature pattern and calculating the coordinates, and the motion platform is adjusted to align the rotation center point O with the scanning center point O′, comprising the following steps: Calculate the offset Y_offset between the scanning center point O′ and the rotation center point O in the Y-axis direction based on the position coordinates of the first characteristic pattern; Calculate the offset X_offset between the scanning center point O′ and the rotation center point O in the X-axis direction based on the position coordinates of the second characteristic pattern; Determine whether the offset between the scanning center point O′ and the rotation center point O in the X-axis direction and the Y-axis direction is within the set range; When the offset between the scanning center point O′ and the rotation center point O in the X-axis direction and / or the Y-axis direction is not within the set range, adjusting the positions of the scanning center point O′ and / or the rotation center point O according to the calculation result; and When the offset between the scanning center point O′ and the rotation center point O in the X-axis direction and the Y-axis direction is within the set range, the center positioning of the motion platform is completed.

2. The motion platform center positioning measurement system according to claim 1, characterized in that: The incident light path comprises an incident light power control module, a polarization control module, a beam shaping module and a light spot scanning module, wherein the incident light path is incident obliquely or vertically from the surface of the wafer.

3. The motion platform center positioning measurement system according to claim 1, characterized in that: The imaging optical path comprises an optical power control module, a polarization control module, a beam shaping module and a photoelectric conversion module, wherein the imaging optical path is configured to perform single-channel acquisition or multi-channel acquisition.

4. The motion platform center positioning measurement system according to claim 1, characterized in that: Construct a platform coordinate system XOY based on the rotation center point O and a scanning image coordinate system X_laserO′Y_laser based on the scanning center point O′, so as to express the offset between the rotation center point O and the scanning center point O′ as the offset between the platform coordinate system and the scanning image coordinate system, with X_offset representing the offset in the X-axis direction and Y_offset representing the offset in the Y-axis direction, wherein the mapping relationship between the first feature point A(R, θ) in the platform coordinate system and its corresponding second feature point A′(R′, θ′) in the scanning image coordinate system is expressed as follows: θ'=θ+arcsin(X_offset / R) Wherein, R represents the distance between the first feature point A and the rotation center point O, θ represents the angle between OA and the negative Y-axis direction of the platform coordinate system XOY, R′ represents the distance between the detected position A″ of the second feature point A′ and the scanning center point O′, and θ′ represents the angle between OA′ and OA″; The offset X_offset in the X-axis direction and the offset Y_offset in the Y-axis direction between the platform coordinate system and the scanned image coordinate system will cause distortion of the scanned image. When R < X_offset, the first feature point A will be missed in scanning; when Y_offset is less than zero, and then, the first feature point A will be missed in scanning; when Y_offset is greater than zero, and then, the first feature point A will be scanned repeatedly. The mapping relationship between the coordinates of the repeatedly scanned feature points and the platform coordinate system is expressed by the following formula: θ′=θ+PI-arcsin(X_offset / R).

5. The motion platform center positioning measurement system according to claim 4, characterized in that: When the wafer is placed on the Theta rotating platform, the center O of the wafer c There are offsets Xc and Yc from the rotation center point O, where the center O of the wafer c The deviation from the rotation center point O will cause the scanned image to shift.

6. The motion platform center positioning measurement system according to claim 5, characterized in that: Calculating the offset Y_offset between the scanning center point O′ and the rotation center point O in the Y-axis direction based on the position coordinates of the first characteristic pattern includes the following steps: The scanning result of the first characteristic pattern is analyzed, wherein the standard circular curve of the first characteristic pattern fluctuates due to deviation in the R-Theta view, and the corresponding relationship between the maximum value and the minimum value of the standard circular curve of the first characteristic pattern is expressed as follows: because The corresponding relationship between the maximum and minimum values ​​of the standard circular curve of the first characteristic pattern is approximately expressed as follows: as well as The offset between the scanning center point O′ and the rotation center point O in the Y-axis direction is calculated based on the correspondence between the maximum and minimum values ​​of the standard circular curve of the first characteristic pattern, and is expressed as follows:

7. The motion platform center positioning measurement system according to claim 6, characterized in that: Calculating the offset X_offset between the scanning center point O′ and the rotation center point O in the X-axis direction based on the position coordinates of the second characteristic pattern includes the following steps: The scanning result of the second characteristic pattern is analyzed, wherein the standard circular curve of the second characteristic pattern fluctuates due to deviation in the R-Theta view, and the corresponding relationship between the maximum value and the minimum value of the standard circular curve of the second characteristic pattern is expressed as follows: as well as According to the calculated Y_offset and Calculate the offset between the scanning center point O′ and the rotation center point O in the X-axis direction, expressed as the following formula:

8. The motion platform center positioning measurement system according to claim 7, characterized in that: The characteristic pattern includes a third characteristic pattern, and the third characteristic pattern is a dot grid pattern, wherein scanning the characteristic pattern and calculating coordinates to determine the offset between the rotation center point O and the scanning center point O′, and adjusting the motion platform to align the rotation center point O with the scanning center point O′ comprises the following steps: Scanning and imaging the third characteristic pattern; The scanning result of the third characteristic pattern is analyzed, wherein when the tangential distortion of the third characteristic pattern exceeds the set range, it indicates that the rotation center point O and the scanning center point O′ have an offset X_offset in the X-axis direction, and when the radial distortion of the third characteristic pattern exceeds the set range, it indicates that the rotation center point O and the scanning center point O′ have an offset Y_offset in the Y-axis direction; When the tangential distortion and / or radial distortion of the scanned image exceeds a set range, adjusting the offset of the scanning center point and the rotating platform center point based on the calculation result; and When the tangential distortion and radial distortion of the scanned image do not exceed the set range, the platform center positioning adjustment is ended.

9. A method for measuring the center positioning of a motion platform, characterized in that: The following steps are involved: Providing a wafer, wherein the wafer is provided with a characteristic pattern, the characteristic pattern comprising a first characteristic pattern and a second characteristic pattern, and the first characteristic pattern is a circle with a first radius; Placing the wafer on the Theta rotating platform of the motion platform, wherein the motion platform includes a Y-axis motion platform and a Theta rotating platform, the Y-axis motion platform is configured to move linearly along the Y-axis direction, and the Theta rotating platform is configured to rotate along a rotation center point O; The light spot is focused on the wafer by the incident light path to form a scanning center point O′; The energy of scattered light or reflected light on the wafer is collected by an imaging optical path to form a scanning image; as well as The method comprises the following steps: determining the offset between the rotation center point O and the scanning center point O′ by scanning the characteristic pattern and calculating the coordinates, and adjusting the motion platform to align the rotation center point O with the scanning center point O′. Calculate the offset Y_offset between the scanning center point O′ and the rotation center point O in the Y-axis direction based on the position coordinates of the first characteristic pattern; Calculate the offset X_offset between the scanning center point O′ and the rotation center point O in the X-axis direction based on the position coordinates of the second characteristic pattern; Determine whether the offset between the scanning center point O′ and the rotation center point O in the X-axis direction and the Y-axis direction is within the set range; When the offset between the scanning center point O′ and the rotation center point O in the X-axis direction and / or the Y-axis direction is not within the set range, adjusting the positions of the scanning center point O′ and / or the rotation center point O according to the calculation result; and When the offset between the scanning center point O′ and the rotation center point O in the X-axis direction and the Y-axis direction is within the set range, the center positioning of the motion platform is completed.

Images