Pre-alignment method for wafer having edge-damaged notch

Abstract

Provided in the present disclosure is a pre-alignment method for a wafer having an edge-damaged notch, the method comprising: S1, by means of a calibration console, driving a wafer to rotate, and using a photosensitive diode to acquire a signal for output; S2, performing data processing to obtain a translation deviation amount of the wafer center and a zero position, as well as at least two rotation angles; S3, performing initial alignment; S4, acquiring a coded image of the wafer, and successively performing grey processing, edge processing, contour extraction and center point position calculation; S5, determining whether the center coordinates of at least two fixed characters are obtained; if no, returning the wafer to an initial position, and replacing with a second rotation angle to repeat S3-S5; and if so, entering S6; S6, calculating the deviation between the center coordinates of the at least two fixed characters and the center coordinates of the preset positions to determine whether the deviation exceeds a preset threshold; if so, returning the wafer to the initial position, and replacing with the second rotation angle to repeat S3-S5; and if no, confirming the current rotation angle as a rotation angle corresponding to a positioning notch; and S7, performing pre-alignment on the basis of the confirmed rotation angle and the translation deviation amount.

Description

Pre-alignment method for wafers with edge damage and notches

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to Chinese patent application number 202311466543.8 filed with the State Intellectual Property Office of China on November 3, 2023, entitled “Pre-alignment method for wafers with edge damaged notches,” the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0003] The present disclosure relates to the technical field of chip optical detection, and in particular to a pre-alignment method for a wafer with an edge damage notch. Background Art

[0004] In the chip lithography production process, 8-inch or 12-inch wafers are usually used as processing raw materials, and go through multiple process flows such as wafer loading and transporting, pre-alignment, code recognition (OCR), alignment and overlay, exposure, and development. Among them, pre-alignment is a key process flow in the early stage, and its accuracy directly affects the success or failure of the subsequent lithography process. The key technologies of pre-alignment include three aspects: one is to calculate the eccentricity of the wafer; the second is to calculate the rotation angle of the wafer positioning notch; the third is to calibrate the wafer position by driving the calibration table based on the eccentricity and the rotation angle of the positioning notch. The traditional method of wafer pre-alignment is optical edge patrol pre-alignment, that is, the voltage surge generated by the wafer positioning notch position is used to determine the positioning notch rotation angle.

[0005] 8-inch and 12-inch wafers are large in size and brittle in nature, so they are prone to edge damage during transportation and use. For traditional optical edge patrol pre-alignment, when there is a small damaged notch on the edge of the wafer that does not affect the subsequent process, the damaged notch will also produce a voltage surge, which makes it impossible to confirm which voltage surge corresponds to the positioning notch. At this time, only the eccentricity of the wafer can be determined, but the rotation angle of the wafer positioning notch cannot be determined. The wafer cannot be accurately calibrated in the direction of rotation, which makes it impossible to carry out the subsequent overlay alignment process and the wafer can only be scrapped, which undoubtedly causes a huge waste of materials. In addition, the relevant technology only uses optical edge patrol to position and calibrate the wafer, and the calibration accuracy is relatively low.

[0006] Summary of the Invention

[0007] (1) Technical issues to be resolved

[0008] In response to the above problems, the present disclosure provides a pre-alignment method for wafers with edge damage notches, which is used to solve technical problems such as the difficulty in determining the rotation angle of the wafer positioning notch and the low calibration accuracy of traditional methods.

[0009] (2) Technical solution

[0010] The present disclosure provides a pre-alignment method for wafers with edge damage and notches, which is applied to wafers with edge damage and notches, including: S1, driving the wafer to rotate through a calibration table, and using a photodiode to collect light quantity signals and convert them into voltage signals for output; S2, performing data processing on the voltage signal output by S1 to obtain a translation deviation between the center of the wafer and the zero position and at least two rotation angles; S3, performing preliminary alignment on the wafer according to the translation deviation and the first rotation angle; wherein the first rotation angle is any one of the at least two rotation angles; S4, using an optical character recognition device to collect a coded image of the wafer, and performing grayscale processing, edge processing, contour extraction, and center point position calculation in sequence; S5, judging whether at least two fixed characters in the code are obtained The center coordinates of the character; if not, the first rotation angle is the rotation angle corresponding to the damaged notch, so that the wafer returns to the initial position before S3, and the second rotation angle is replaced and repeated S3~S5; if so, enter S6; S6, calculate the deviation between the center coordinates of at least two fixed characters and the preset position coordinates of the center of the fixed character, and judge whether the deviation exceeds the preset threshold; if so, the first rotation angle is the rotation angle corresponding to the damaged notch, so that the wafer returns to the initial position before S3, and the second rotation angle is replaced and repeated S3~S5 until the rotation angle corresponding to the positioning notch is confirmed; if not, confirm that the current rotation angle is the rotation angle corresponding to the positioning notch; S7, pre-align the wafer according to the rotation angle and translation deviation corresponding to the positioning notch confirmed in S6.

[0011] According to an embodiment of the present disclosure, the process further includes: S8, performing secondary alignment on the wafer according to the rotation angle corresponding to the positioning notch confirmed in S6 and the center coordinates of at least two fixed characters.

[0012] According to an embodiment of the present disclosure, S3 includes: S31, according to the first rotation angle Δθ i , the wafer is rotated -Δθ by the calibration stage i ; S32, calculate the rotation -Δθ according to the translation deviation ΔX, ΔY i The translation deviation ΔX′ i , ΔY′ i ; S33, the wafer is driven to move in the X direction -ΔX′ by the calibration stage i , Y translation -ΔY′ i , complete the initial alignment.

[0013] According to an embodiment of the present disclosure, S32 includes: calculating the rotation -Δθ according to the following formula: i The translation deviation ΔX′ i , ΔY′ i :

[0014] Where Δθ i is the first rotation angle, ΔX and ΔY are the translation deviations in the X and Y directions respectively, and ΔX′ i , ΔY′ i Rotation -Δθ i The translation deviation in the X and Y directions is n, and the number of damaged gaps is n.

[0015] According to an embodiment of the present disclosure, the grayscale processing in S4 includes: using the cvtColor function in OpenCV to convert the collected encoded image into a grayscale image, and then optimizing the image quality of the grayscale image.

[0016] According to an embodiment of the present disclosure, optimizing the image quality of a grayscale image includes: bilateral filtering processing, performing bilateral filtering on the grayscale image to suppress noise; and normalization processing, using the normalize function in OpenCV to normalize the image after bilateral filtering.

[0017] According to an embodiment of the present disclosure, the edge processing in S4 includes: using the Canny function in OpenCV to perform edge detection on the normalized image; the contour extraction in S4 includes: using the findContours function in OpenCV to convert the information obtained by edge detection into contour information, and extract the contour graphics of at least two fixed characters in the code; the center point position calculation in S4 includes: using two fixed characters, and using the minimum circumscribed rectangle method to calculate the center coordinates A of each of the two fixed characters according to the contour graphics of each of the two fixed characters. i (x ai ,y ai ), B i (x bi ,y bi ).

[0018] According to an embodiment of the present disclosure, the length membership function and the width membership function in S42 are respectively one of a triangle membership function, a trapezoidal membership function, and a piecewise linear membership function.

[0019] According to an embodiment of the present disclosure, the center coordinates A of the two fixed characters are calculated in S6. i (x ai ,y ai ), B i (x bi ,y bi ) and the preset position coordinate A′0(x′ a0 ,y′ a0 ), B′0(x′ b0 ,y′ b0) includes: using the midpoint coordinates of the line connecting the centers of two fixed characters Coordinates of the midpoint of the line connecting the center of the preset position Calculate the deviation using the following formula:

[0020] Where ΔX ABi , ΔY ABi The X and Y deviations of the line connecting the centers of the two fixed characters; Δθ ABi It is the angular deviation of the line connecting the centers of two fixed characters.

[0021] According to an embodiment of the present disclosure, S6 includes: determining ΔX ABi , ΔY ABi and Δθ ABi Whether one of the deviations exceeds a corresponding preset threshold; if so, the first rotation angle is the rotation angle corresponding to the damaged notch; if not, the current rotation angle is confirmed to be the rotation angle corresponding to the positioning notch.

[0022] According to an embodiment of the present disclosure, S8 includes: S81, according to the angle deviation Δθ of the line connecting the centers of the two fixed characters, ABi , the wafer is rotated -Δθ by the calibration stage ABi S82, using an optical character recognition device to collect the coded image of the wafer, and then perform grayscale processing, edge processing, contour extraction, center point position calculation and rotation -Δθ ABi The center coordinate A′ i (x′ ai ,y′ ai ), B′ i (x′ bi ,y′ bi ); S83, according to the center coordinate A' i (x′ ai ,y′ ai ), B′ i (x′ bi ,y′ bi ) Calculate the deviation ΔX′ from the preset position coordinates of the fixed character center ABi , ΔY′ ABi ; S84, the wafer is driven to translate in the X direction -ΔX′ by the calibration stage ABi , Y translation -ΔY′ ABi , completing the secondary alignment. (3) Beneficial effects

[0023] The pre-alignment method for wafers with edge damage and notches disclosed in the present invention does not require additional hardware structures in the process flow. By utilizing the camera in the optical character recognition device in the subsequent process, when it collects and identifies the coded characters on the wafer surface, a graphic vision algorithm is added to realize the extraction of the center coordinate position of the wafer coded characters; further, by judging whether the deviation between the center coordinate and the center coordinate of the preset position exceeds a preset threshold, the rotation angle corresponding to the positioning notch is confirmed, so that the wafer can be pre-aligned; because the positioning accuracy of the graphic vision algorithm is higher than the positioning accuracy of the optical edge patrol, the wafer is re-positioned by fixing the deviation between the center coordinate of the character and the center coordinate of the preset position, thereby further improving the calibration accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 schematically shows an application scenario of a method for pre-aligning a wafer with an edge damage notch according to an embodiment of the present disclosure;

[0025] FIG2 schematically shows a flow chart of a method for pre-aligning a wafer with an edge damage notch according to an embodiment of the present disclosure;

[0026] FIG3 schematically shows a schematic diagram of a wafer structure with an edge damage notch and a wafer code according to an embodiment of the present disclosure;

[0027] FIG4 schematically shows a schematic diagram of voltage output when the wafer has no edge damage and is concentric with the calibration stage according to an embodiment of the present disclosure;

[0028] FIG5 schematically shows a schematic diagram of voltage output when the wafer has no edge damage and is eccentric to the calibration stage according to an embodiment of the present disclosure;

[0029] FIG6 schematically shows a schematic diagram of voltage output when a wafer has edge damage and is eccentric to a calibration stage according to an embodiment of the present disclosure;

[0030] FIG7 schematically shows the position diagram of the center coordinates of two fixed characters and the center coordinates of a preset position according to an embodiment of the present disclosure;

[0031] Description of reference numerals:

[0032] 1. Wafer; 2. Calibration table; 3. LED light source; 4. Photosensitive diode; 5. Optical character recognition device; 6. Positioning notch; 7. Wafer code; 8. First damage notch; 9. Second damage notch. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0034] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0035] It should be noted that if directional indications are involved in the embodiments of the present disclosure, the directional indications are only used to explain the relative positional relationship, movement status, etc. between the components under a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0036] The use of ordinal numbers such as "first," "second," and "third" in the specification and claims to modify corresponding elements does not in itself imply or represent any ordinal number of the elements, nor does it represent the order of one element relative to another or the order in the manufacturing method. The use of such ordinal numbers is only used to clearly distinguish one element with a certain name from another element with the same name.

[0037] FIG1 schematically shows an application scenario of a method for pre-aligning a wafer with an edge damage gap according to an embodiment of the present disclosure.

[0038] As shown in Figure 1, the application scenario according to this embodiment may include a wafer 1, a calibration stage 2, an LED light source 3, a photodiode 4, and an optical character recognition device 5. The calibration stage 2 is used to drive the wafer 1 to rotate and can also perform quantitative X- and Y-direction translation to calibrate the position of the wafer 1; the LED light source 3 is used to provide continuous and stable illumination; the photodiode 4 is used to receive the light intensity of the LED light source 3 and convert the light intensity signal into a voltage signal through photoelectric conversion; the optical character recognition device 5, or OCR device, is mainly composed of an OCR camera, an OCR telecentric lens, and a software processing system. It is used to collect and recognize wafer codes and is a subsequent process flow of the pre-alignment process.

[0039] The pre-alignment method works as follows: an LED light source 3 is positioned near the bottom edge of wafer 1, and a photodiode 4 is positioned near the top edge. Due to the eccentricity and positioning notch of wafer 1, the amount of light received by photodiode 4 changes during wafer 1 rotation, causing the voltage converted by photoelectric conversion by photodiode 4 to change accordingly. When wafer 1 is not eccentric and has no positioning notch, the output voltage is constant; when wafer 1 is eccentric, the output voltage waveform is a sine wave; when wafer 1 has a positioning notch, a sudden voltage surge occurs at the location of the notch. The hardware circuit transmits this voltage change to the software system. Through software conversion and calculation, the relationship between the voltage change and the wafer eccentricity and the rotation angle of the notch is determined. This control then controls the rotation and movement of the calibration stage 2 to position wafer 1 at the preset position, achieving wafer pre-alignment.

[0040] Related technologies typically use the voltage spike generated at the wafer's positioning notch location to determine the notch's rotation angle. However, when a damaged notch is located on the wafer edge, voltage spikes are generated at multiple locations, making it impossible to identify which voltage spike corresponds to the notch, and thus, to determine the wafer's notch rotation angle. Furthermore, related technologies rely solely on optical edge tracking to locate and calibrate the wafer, resulting in relatively low calibration accuracy.

[0041] Based on this, the present disclosure provides a pre-alignment method for wafers with edge damage and notches, which is applied to wafers with edge damage and notches, see Figure 2, including: S1, driving the wafer 1 to rotate through the calibration table 2, using the photodiode 4 to collect the light signal and convert it into a voltage signal output; S2, performing data processing on the voltage signal output by S1 to obtain the translation deviation between the center of the wafer 1 and the zero position and at least two rotation angles; S3, performing preliminary alignment on the wafer 1 according to the translation deviation and the first rotation angle; wherein the first rotation angle is any one of the at least two rotation angles; S4, using the optical character recognition device 5 to collect the coded image of the wafer 1, and performing grayscale processing, edge processing, contour extraction, and center point position calculation in sequence; S5, judging whether the coded center is obtained The center coordinates of at least two fixed characters; if not, the first rotation angle is the rotation angle corresponding to the damaged notch, so that the wafer 1 returns to the initial position before S3, and the second rotation angle is replaced and repeated S3~S5; if so, enter S6; S6, calculate the deviation between the center coordinates of at least two fixed characters and the preset position coordinates of the center of the fixed characters, and judge whether the deviation exceeds the preset threshold; if so, the first rotation angle is the rotation angle corresponding to the damaged notch, so that the wafer 1 returns to the initial position before S3, and the second rotation angle is replaced and repeated S3~S5, until the rotation angle corresponding to the positioning notch is confirmed; if not, confirm that the current rotation angle is the rotation angle corresponding to the positioning notch; S7, pre-align the wafer 1 according to the rotation angle and translation deviation corresponding to the positioning notch confirmed in S6.

[0042] The pre-alignment method disclosed in the present invention does not require additional hardware structure. It utilizes the OCR camera in the optical character recognition device 5 in the subsequent process. When it collects and identifies the coded characters on the surface of the wafer 1, it adds a graphic vision algorithm to realize the extraction of the center coordinates of the wafer coded characters. Generally, each wafer is engraved with a string of wafer codes 7 (as shown in Figure 3) at a fixed position (generally just above the positioning notch), and the first two digits of the coded characters in the wafer code 7 (Figure 3 uses the "Y-" character) are fixed, and only the last few characters change. Therefore, the distance between the center line coordinate position of the first two fixed characters and the coordinate position of the wafer positioning notch is fixed. It should be noted that the present invention can not only use the center coordinate position of the first two fixed characters for collection and calculation, but also use the center coordinates of two or more fixed characters at any position in the wafer code for collection and calculation. For the convenience of explanation, the following is further explained with the first two fixed characters.

[0043] By rotating the wafer to the position of each voltage surge, if the first two fixed characters are not fully collected or the center line coordinate deviation exceeds the preset threshold range, it means that the voltage surge at this location is caused by the first damaged notch 8 or the second damaged notch 9. The preset threshold range here can be determined by comprehensively considering the repeatability of the entire device and the etching accuracy of the coded characters. A damaged notch is a small damaged notch that is easily present on the edge during transportation or use. The damaged notch does not affect subsequent process processing, as shown in Figure 3. If the center line coordinate deviation of the first two fixed characters is within the preset threshold range, it means that the voltage surge at this location is caused by the positioning notch 6 (Notch). The positioning notch is used to position the wafer in the θ direction and calculate the positioning rotation angle of the wafer. At this time, the positioning notch rotation angle can be determined. The wafer can be accurately calibrated by the determined eccentricity and positioning notch rotation angle.

[0044] On the basis of the above embodiment, the method further includes: S8, performing secondary alignment on the wafer 1 according to the rotation angle corresponding to the positioning notch confirmed in S6 and the center coordinates of at least two fixed characters.

[0045] Since a graphic vision algorithm has been added to the first two fixed characters of the wafer code, and the positioning accuracy of the graphic vision algorithm is higher than the positioning accuracy of the optical edge patrol, after determining the wafer positioning notch, the wafer can be roughly calibrated by the eccentricity and the positioning notch rotation angle, and then the wafer can be positioned for the second time by the coordinate deviation of the center line of the first two fixed characters to further improve the calibration accuracy.

[0046] Specifically, as shown in Figure 1, wafer 1 is placed on calibration stage 2. LED light source 3 is turned on, partially blocking light from the edge of wafer 1. Unblocked light is received by photodiode 4, which converts the light intensity signal into a voltage signal through photoelectric conversion and transmits the signal to the software system. As calibration stage 2 rotates wafer 1 360°, the amount of blocked light changes, causing the voltage signal output by photodiode 4 to change.

[0047] There are three types of changes:

[0048] ① If wafer 1 has no edge damage and is concentric with calibration stage 2, photodiode 4 receives light and converts it into photoelectric energy, resulting in a constant output voltage. There is a voltage spike only at positioning notch 6, as shown in Figure 4. At this point, the wafer's eccentricity is zero, and the translational deviation is also zero. The angle Δθ0 from the initial position to the voltage spike is the positioning notch rotation angle. Δθ0 is the rotation angle from the initial position to positioning notch 6.

[0049] ② If wafer 1 has no edge damage and is eccentric to calibration stage 2, the light received by photodiode 4, after photoelectric conversion, produces a sinusoidal output voltage waveform, with a sudden voltage spike at positioning notch 6, as shown in Figure 5. The voltage difference between the peak and trough of the sine wave can be used to determine the translational deviation and eccentricity between the wafer and the zero position of calibration stage 2. The angle Δθ0 from the initial position to the voltage spike is the positioning notch rotation angle.

[0050] ③ If the wafer 1 has edge damage, such as the first damage notch 8 or the second damage notch 9, and is eccentric to the calibration stage 2, the photodiode 4 receives light and then converts it into a photoelectric conversion. Its output voltage waveform is a sine wave, and there are voltage spikes at the positioning notch 6, the first damage notch 8, and the second damage notch 9, as shown in Figure 6. At this time, the translation deviation and eccentricity between the wafer and the zero position of the calibration stage 2 can be obtained based on the voltage difference between the peak and trough of the sine wave, and the angles Δθ0, Δθ1, ... Δθ from the initial position to the voltage spike position can be obtained. n is the rotation angle of the positioning notch or the rotation angle of the broken notch, where n is the number of broken notches.

[0051] On the basis of the above embodiment, S3 includes: S31, according to the first rotation angle Δθ i , the wafer 1 is first rotated by -Δθ through the calibration stage 2 i ; S32, calculate the rotation -Δθ according to the translation deviation ΔX, ΔY i The translation deviation ΔX′ i , ΔY′ i ; S33, the calibration stage 2 drives the wafer 1 to move in the X direction -ΔX′ i , Y translation -ΔY′ i , complete the initial alignment.

[0052] For scenarios 1 and 2, photodiode 4 transmits a voltage signal to the software system. The software then converts and calculates the wafer center's X-axis deviation ΔX, Y-axis deviation ΔY, and the positioning notch's rotational deviation Δθ0. The zero position is set at the center of the initial position of calibration stage 2. By controlling rotation stage 2 to rotate -Δθ0, the positioning notch's rotation angle is compensated. Because wafer 1 is eccentric to calibration stage 2, the X-axis and Y-axis translational deviations of the wafer center from the zero position also change, becoming ΔX′0 and ΔY′0, respectively.

[0053] Based on the above embodiment, S32 includes: calculating the rotation -Δθ according to the following formula: i The translation deviation ΔX′ i , ΔY′ i :

[0054] Where Δθ i is the first rotation angle, ΔX and ΔY are the translation deviations in the X and Y directions respectively, and ΔX′ i , ΔY′ i Rotation -Δθ i The translation deviation in the X and Y directions is n, and the number of damaged gaps is n.

[0055] Substituting Δθ0 into the calculation formula (1) (2) yields ΔX′0, ΔY′0. At this time, driving the calibration stage 2 to translate -ΔX′0 in the X direction and -ΔY′0 in the Y direction achieves the initial alignment of the wafer 1.

[0056] For case ③, the software system first converts and calculates the deviation ΔX in the X direction and ΔY in the Y direction between the wafer center and the zero position. However, due to the presence of edge damage and notches, multiple voltage spikes will occur, resulting in multiple rotation angles Δθ0, Δθ1, ... Δθ n ,To determine the rotation angle corresponding to the positioning notch, ,subsequent graphics vision algorithm processing is required.

[0057] First drive the calibration stage 2 to rotate -Δθ i Then, Δθ i Substitute into formula (1) (2) to find ΔX′ i , ΔY′ i , drive the calibration stage 2 to translate -ΔX′ in the X direction i , translate in the Y direction -ΔY′ iThe wafer code image is captured using the OCR camera of the existing optical character recognition device 5. The installation position of the OCR camera of optical character recognition device 5 has been determined. A rectangular coordinate system is established with the center of the OCR camera's field of view as the zero point. The zero position of calibration stage 2 is calibrated using a calibration wafer. The center coordinates of the first two fixed characters of the wafer code are extracted through steps such as image grayscale processing, bilateral filtering, normalization, Canny edge processing, contour extraction, and center point position calculation.

[0058] The present invention utilizes its original hardware and only adds a graphic vision algorithm of the first two fixed characters of the wafer code into the software processing system to realize the calculation and extraction of the coordinates of the center line connecting the two fixed characters.

[0059] On the basis of the above embodiment, the grayscale processing in S4 includes: using the cvtColor function in OpenCV to convert the collected coded image into a grayscale image, and then optimizing the image quality of the grayscale image.

[0060] You can directly call the cvtColor() function provided in OpenCV to convert color images into grayscale.

[0061] Based on the above embodiment, the grayscale image quality optimization includes: bilateral filtering processing, performing bilateral filtering on the grayscale image to suppress noise; normalization processing, using the normalize function in OpenCV to normalize the image after bilateral filtering.

[0062] Bilateral filtering is a nonlinear filtering method that compromises the spatial proximity and pixel value similarity of an image. It simultaneously considers spatial, information, and grayscale similarity to achieve edge-preserving denoising. It is simple, non-iterative, and performs local processing. Bilateral filtering effectively preserves image edge details while filtering out low-frequency noise. OpenCV provides the bilateralFilter() function to implement bilateral filtering. Simply specify the parameters (int d, double sigmaColor, and double sigmaSpace) based on your needs; determine the input image and the boundary mode to output the target image after bilateral filtering.

[0063] Image normalization involves converting an original image into a standardized form through a series of transformations. This standard form is invariant to affine transformations such as translation, rotation, and scaling. Normalization distributes pixel grayscale values ​​within the [0, 1] range, preventing image contrast and uneven pixel brightness distribution from interfering with subsequent image processing. In practice, image normalization is performed directly using the normalize() function provided by OpenCV.

[0064] On the basis of the above embodiment, the edge processing in S4 includes: using the Canny function in OpenCV to perform edge detection on the normalized image; the contour extraction in S4 includes: using the findContours function in OpenCV to convert the information obtained by edge detection into contour information, and extract the contour graphics of at least two fixed characters in the code; the center point position calculation in S4 includes: using two fixed characters, and using the minimum circumscribed rectangle method to calculate the graphic center coordinates A of each of the two fixed characters according to the contour graphics of each of the two fixed characters. i (x ai ,y ai ), B i (x bi ,y bi ).

[0065] Canny edge detection is a relatively good edge detection method, and its detected boundary continuity and aggregation are the highest. In actual operation, the Canny() function provided by OpenCV is directly used to perform edge detection by inputting the low threshold, high threshold, size value of the Soble operator, and input image. The information obtained by Canny edge detection is converted into contour information using the findContours() function provided by OpenCV, and the contour graphics of the first two fixed characters of the wafer code are extracted. The minimum enclosing rectangle method is then used to calculate the graphic center coordinates of the first two fixed characters of the wafer code. In actual operation, the cv2.boundingRect() function provided by OpenCV is directly used to calculate the graphic center coordinates A of each fixed character. i (x ai ,y ai ), B i (x bi ,y bi ).

[0066] Calculate the coordinate deviation of the line connecting the centers of the first two fixed characters and make a judgment. There are three cases as follows:

[0067] ④ If the center coordinates of the first two fixed characters do not appear, it means Δθ i The corresponding character is a damaged notch. At this time, it means that the fixed character is outside the OCR field of view. Therefore, the center line coordinate information of the first two fixed characters cannot be obtained by using the above image processing method.

[0068] ⑤ If the center coordinates A of the first two fixed characters appear at the same time i (x ai ,y ai ), B i (x bi ,ybi ), as shown in Figure 7. Then calculate the preset position coordinate A′0(x′ a0 ,y′ a0 ), B′0(x′ b0 ,y′ b0 The preset position is the standard position for wafer placement. Then calculate the deviation ΔX between the center line coordinates and the preset position center line coordinates. ABi , ΔY ABi , Δθ ABi Among them, the X and Y deviations of the center line are expressed as the midpoint coordinates of the center line. Coordinates of the midpoint of the line connecting the preset center The deviation is expressed as .

[0069] If ΔX ABi , ΔY ABi , Δθ ABi If any one of them exceeds the set threshold range, it means that Δθ i It corresponds to the rotation angle of the damaged notch.

[0070] ⑥If ΔX ABi , ΔY ABi , Δθ ABi are all within the threshold range set above, then Δθ i The corresponding is the positioning notch rotation angle.

[0071] Based on the above embodiment, the center coordinates A of the two fixed characters are calculated in S6. i (x ai ,y ai ), B i (x bi ,y bi ) and the fixed character center preset position coordinate A′0(x′ a0 ,y′ a0 ), B′0(x′ b0 ,y′ b0 ) include:

[0072] Use the midpoint coordinates of the line connecting the centers of two fixed characters Coordinates of the midpoint of the line connecting the center of the fixed character preset position Calculate the deviation using the following formula:

[0073] Where ΔX ABi , ΔY ABi The X and Y deviations of the line connecting the centers of the two fixed characters; Δθ ABiIt is the angular deviation of the line connecting the centers of two fixed characters.

[0074] Based on the above embodiment, S6 includes: judging ΔX ABi , ΔY ABi and Δθ ABi Whether one of the deviations exceeds a corresponding preset threshold; if so, the first rotation angle is the rotation angle corresponding to the damaged notch; if not, the current rotation angle is confirmed to be the rotation angle corresponding to the positioning notch.

[0075] If the deviation ΔX ABi , ΔY ABi , Δθ ABi If any of the values ​​exceeds the set threshold, it means that Δθ0 corresponds to a damaged notch. In this case, the damaged notch is near the positioning notch, so the fixed character is within the OCR field of view. The threshold range of the deviation is determined by comprehensively considering the repeatability of the entire device and the etching accuracy of the coded character.

[0076] Based on the above embodiment, ΔX in S6 ABi The corresponding preset threshold is generally set to (-100μm, 100μm), ΔY ABi The corresponding preset threshold is generally set to (-100μm, 100μm), Δθ ABi The corresponding preset threshold is generally set to (-360", 360".

[0077] When the fourth and fifth situations occur, the calibration platform 2 moves ΔX′ in the X direction. i , translate ΔY′ in the Y direction i , and then rotate Δθ i angle and return to the original position.

[0078] Then Δθ i+1 Substitute into the above steps S3 to S6, if Δθ i+1 The corresponding rotation angle of the positioning gap is stopped; if Δθ i+1 Corresponding to the rotation angle of the damaged notch, continue to repeat the above steps and substitute Δθ i+2 Test Δθ i+2 Is it the positioning notch rotation angle? Similarly, substitute Δθ i+3 , Δθ i+4 ...Δθ n Verify one by one until the Δθth i (i=0,1,2,3……n) is the rotation angle of the positioning notch.

[0079] The wafer pre-alignment method disclosed in the present invention realizes the extraction of the center coordinate position of the wafer coding character by adding a graphic vision algorithm without adding any additional hardware structure. Then, by judging whether the center line coordinate position of the first two fixed characters exists and whether its position deviation is within the set threshold range, it is judged which are the damaged notches and which are the real wafer positioning notches. In this way, even if the edge of the wafer is damaged, the rotation angle of the wafer positioning notch can still be effectively determined, and the wafer can be accurately pre-aligned.

[0080] Based on the above embodiment, S8 includes: S81, according to the angle deviation Δθ of the line connecting the centers of the two fixed characters ABi , the wafer 1 is first rotated by -Δθ through the calibration stage 2 ABi S82, using the optical character recognition device 5 to collect the coded image of the wafer 1, and then perform grayscale processing, edge processing, contour extraction, center point position calculation and rotation -Δθ ABi The center coordinate A′ i (x′ ai , y′ ai ), B′ i (x′ bi , y′ bi ); S83, according to the center coordinate A' i (x′ ai ,y′ ai ), B′ i (x′ bi ,y′ bi ) Calculate the deviation ΔX′ from the preset position coordinates of the fixed character center ABi , ΔY′ ABi ; S84, the calibration stage 2 drives the wafer 1 to translate in the X direction -ΔX′ ABi , Y translation -ΔY′ ABi , completing the secondary alignment.

[0081] When the Δθth i (i=0,1,2,3……n) is the rotation angle corresponding to the positioning notch, and the deviation between the coordinate position of the center line and the preset position of the fixed character center can be used to calibrate the wafer for the second time. First, drive the calibration stage 2 to rotate -Δθ ABi , and read out the center coordinate position A′ of the first two fixed characters after rotation i (x′ ai ,y′ ai ), B′ i (x′ bi ,y′ bi ). The position coordinate A′ is read out. i (x′ ai ,y′ ai ), B′i (x′ bi ,y′ bi ) is substituted into formulas (3) and (4) to calculate the X-direction deviation ΔX′ from the preset position at this time ABi , Y-direction deviation ΔY′ ABi Then drive the calibration stage to translate -ΔX′ in the X direction ABi , translate in the Y direction -ΔY′ ABi , the wafer can be pre-aligned with higher precision.

[0082] The present invention can calibrate wafers with edge damage and notches by adding a graphic vision algorithm without adding additional hardware structure, has good compatibility and avoids waste of materials; since a graphic vision algorithm for the first two fixed characters of the wafer encoding is added, and the accuracy of the graphic vision algorithm is higher than the accuracy of the optical edge patrol, after confirming the wafer positioning notch, the wafer is re-positioned and calibrated through the center line coordinate deviation of the first two fixed characters, which can further improve the pre-alignment accuracy of the wafer.

[0083] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure. Industrial Applicability

[0084] The present disclosure provides a pre-alignment method for a wafer with an edge damage notch, comprising: S1, driving the wafer to rotate through a calibration table, and using a photosensitive diode to collect signal output; S2, performing data processing to obtain a translation deviation between the wafer center and the zero position, and at least two rotation angles; S3, performing initial alignment; S4, collecting a coded image of the wafer, and sequentially performing grayscale processing, edge processing, contour extraction, and center point position calculation; S5, judging whether the center coordinates of at least two fixed characters are obtained; if not, returning the wafer to an initial position, replacing the second rotation angle and repeating S3 to S5; if so, entering S6; S6, calculating the deviation between the center coordinates of at least two fixed characters and the center coordinates of a preset position, and judging whether the deviation exceeds a preset threshold; if so, returning the wafer to an initial position, replacing the second rotation angle and repeating S3 to S5; if not, confirming that the current rotation angle is the rotation angle corresponding to the positioning notch; S7, performing pre-alignment based on the confirmed rotation angle and translation deviation.

[0085] Furthermore, it is understood that the pre-alignment method for wafers with edge damage notches disclosed herein is reproducible and can be used in a variety of applications. For example, the pre-alignment method for wafers with edge damage notches disclosed herein can be used in the field of optical inspection technology.

Claims

1. A pre-alignment method for a wafer with an edge damage notch, applied to a wafer with an edge damage notch, characterized in that: include: S1, driving the wafer (1) to rotate via the calibration platform (2), collecting light quantity signals using the photodiode (4) and converting them into voltage signals for output; S2, performing data processing on the voltage signal output by S1 to obtain a translation deviation between the center of the wafer (1) and a zero position and at least two rotation angles; S3, performing preliminary alignment on the wafer (1) according to the translation deviation and the first rotation angle; wherein the first rotation angle is any one of the at least two rotation angles; S4, using an optical character recognition device (5) to collect a coded image of the wafer (1), and sequentially perform grayscale processing, edge processing, contour extraction, and center point position calculation; S5, determining whether the center coordinates of at least two fixed characters in the code are obtained; if not, the first rotation angle is the rotation angle corresponding to the damaged notch, so that the wafer (1) returns to the initial position before S3, and the second rotation angle is replaced and S3 to S5 are repeated; if so, entering S6; S6, calculating the deviation between the center coordinates of the at least two fixed characters and the preset position coordinates of the center of the fixed characters, and determining whether the deviation exceeds a preset threshold; if so, the first rotation angle is the rotation angle corresponding to the damaged notch, so that the wafer (1) returns to the initial position before S3, and the second rotation angle is replaced and S3 to S5 are repeated until the rotation angle corresponding to the positioning notch is confirmed; if not, confirming that the current rotation angle is the rotation angle corresponding to the positioning notch; S7, pre-aligning the wafer (1) according to the rotation angle corresponding to the positioning notch confirmed in S6 and the translation deviation.

2. The pre-alignment method for wafers with edge damage notches according to claim 1, characterized in that: Also includes: S8, performing secondary alignment on the wafer (1) according to the rotation angle corresponding to the positioning notch confirmed in S6 and the center coordinates of the at least two fixed characters.

3. The pre-alignment method for wafers with edge damage notches according to claim 1, characterized in that: The S3 includes: S31, according to the first rotation angle Δθ i The calibration platform (2) drives the wafer (1) to rotate -Δθ i ; S32, calculating the rotation -Δθ according to the translation deviation ΔX, ΔY i The translation deviation ΔX′ i , ΔY′ i ; S33, driving the wafer (1) to translate in the X direction by -ΔX′ through the calibration platform (2) i , Y translation -ΔY′ i , complete the initial alignment.

4. The pre-alignment method for wafers with edge damage notches according to claim 3, characterized in that: The S32 includes: The rotation -Δθ is calculated according to the following formula i The translation deviation ΔX′ i , ΔY′ i : Among them, Δθ i is the first rotation angle, ΔX and ΔY are the translation deviations in the X and Y directions respectively, and ΔX′ i , ΔY′ i They are respectively rotated -Δθ i The translation deviation in the X and Y directions is n, and n is the number of damaged gaps.

5. The pre-alignment method for wafers with edge damage notches according to claim 2, characterized in that: The grayscale processing in S4 includes: The collected coded image is converted into a grayscale image by using the cvtColor function in OpenCV, and then the image quality of the grayscale image is optimized.

6. The pre-alignment method for wafers with edge damage notches according to claim 5, characterized in that: Optimizing the image quality of the grayscale image includes: Bilateral filtering processing, performing bilateral filtering on the grayscale image to suppress noise; Normalization processing, using the normalize function in OpenCV, normalizes the image after bilateral filtering.

7. The pre-alignment method for wafers with edge damage notches according to claim 1, characterized in that: The edge processing in S4 includes: using the Canny function in OpenCV to perform edge detection on the normalized image; The contour extraction in S4 includes: using the findContours function in OpenCV to convert the information obtained by edge detection into contour information, and extracting the contour graphics of at least two fixed characters in the code; The center point position calculation in S4 includes: using two fixed characters, and using the minimum circumscribed rectangle method to calculate the graphic center coordinates A of the two fixed characters respectively according to the contour graphics of the two fixed characters. i (x ai ,y ai ), B i (x bi ,y bi ).

8. The pre-alignment method for wafers with edge damage notches according to claim 1, characterized in that: In step S6, the center coordinates A of the two fixed characters are calculated. i (x ai ,y ai ), B i (x bi ,y bi ) and the preset position coordinate A′0(x′ a0 ,y′ a0 ), B′0(x′ b0 ,y′ b0 ) include: Use the midpoint coordinates of the line connecting the centers of the two fixed characters The midpoint coordinates of the line connecting the center of the preset position with the center of the fixed character The deviation is calculated as follows: Where ΔX ABi , ΔY ABi The X and Y deviations of the center line of the two fixed characters respectively; Δθ ABi It is the angular deviation of the line connecting the centers of two fixed characters.

9. The pre-alignment method for wafers with edge damage notches according to claim 8, characterized in that: The S6 includes: Determine the ΔX ABi , ΔY ABi and Δθ ABi Whether one of the deviations exceeds the corresponding preset threshold; if so, the first rotation angle is the rotation angle corresponding to the damaged notch; if not, confirming that the current rotation angle is the rotation angle corresponding to the positioning notch.

10. The pre-alignment method for wafers with edge damage notches according to claim 2, characterized in that: The S8 includes: S81, according to the angle deviation Δθ of the center line of the two fixed characters ABi The calibration platform (2) drives the wafer (1) to rotate -Δθ ABi ; S82, using an optical character recognition device (5) to collect the coded image of the wafer (1), and sequentially perform grayscale processing, edge processing, contour extraction, center point position calculation and rotation -Δθ ABi The center coordinate A′ i (x′ ai ,y′ ai ), B′ i (x′ bi ,y′ bi ); S83, according to the center coordinate A′ i (x′ ai ,y′ ai ), B′ i (x′ bi ,y′ bi ) Calculate the deviation ΔX′ from the preset position coordinates of the fixed character center ABi , ΔY′ ABi ; S84, driving the wafer (1) to translate in the X direction by -ΔX′ through the calibration platform (2) ABi , Y translation -ΔY′ ABi , completing the secondary alignment.

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