Method for obtaining wafer offset and method for teaching robot position before wafer measurement

Abstract

The present invention discloses a method for obtaining a wafer offset and a method for teaching a position of a manipulator before wafer measurement. The method for obtaining a wafer offset comprises the following steps: placing a wafer on a carrier so that the center of the wafer is approximately close to the rotation center of the carrier; the carrier drives the wafer to rotate to angles of 0°, 90°, 180° and 270°, and using a camera to respectively take images of the wafer edge at corresponding angles to obtain an image P. x 1. P y 1. P x 2. P y 2; Based on the image P x 1. P y 1. P x 2. P y 2. The position of the wafer edge, calculate the offset D of the wafer center relative to the rotation center of the carrier in the x and y directions x and D y The above method for obtaining the wafer offset does not require the wafer edge to be suspended, and is particularly suitable for the case where the wafer radius is smaller than the carrier radius, thereby expanding the scope of application of three-dimensional topography measurement and improving the reliability and accuracy of the measurement.

Description

Technical Field

[0001] The present invention relates to the field of measurement technology, and in particular to a method for obtaining a wafer offset and a method for teaching a manipulator point position before wafer measurement. Background Art

[0002] Three-dimensional morphology information is gaining increasing attention because it can more comprehensively and truly reflect the characteristics of the part surface and effectively evaluate the surface processing quality. By measuring the three-dimensional morphology, the surface quality of the part can be comprehensively evaluated, thereby verifying the advantages and disadvantages of the processing method and the rationality of the design requirements, and then guiding the optimization of the processing technology to achieve high-quality part surfaces and ensure their functional use.

[0003] Existing three-dimensional topography measurement methods usually use a carrier to drive the wafer to rotate, and the measuring probe collects three-dimensional topography data corresponding to different rotation radii of the wafer. If the center of the wafer is inconsistent with the rotation center of the carrier during rotation, the wafer will be displaced and the data cannot be accurately measured. Without protective measures, the wafer may even be thrown out of the carrier and damaged. The existing wafer positioning method requires the edge of the wafer to be suspended in the air, and the edge position of the wafer is measured using sensors that shoot up and down. However, this positioning method is not applicable to situations where the wafer radius is smaller than the carrier radius, which limits the applicability and measurement accuracy of the measuring equipment. Summary of the invention

[0004] Based on this, the present invention application provides a method for obtaining wafer offset and a method for teaching robot positions before wafer measurement to solve the problem of inaccurate wafer positioning and ensure the safety and accuracy of the measurement process.

[0005] A method for obtaining a wafer offset comprises the following steps:

[0006] Placing a wafer on a carrier so that the center of the wafer is approximately close to the rotation center of the carrier, wherein the radius of the wafer is smaller than the radius of the carrier;

[0007] The carrier drives the wafer to rotate to 0°, 90°, 180° and 270°, and the camera is used to take images of the wafer edge at the corresponding angles to obtain images P. x 1. P y 1. P x 2. P y 2. The camera is installed perpendicular to the plane of the carrier, and the edge of the wafer is within the field of view of the camera during the wafer rotation;

[0008] Based on the image P x 1. P y 1. P x 2. P y2. The position of the wafer edge, calculate the offset D of the wafer center relative to the rotation center of the carrier in the x and y directions x and D y .

[0009] In one embodiment, the image P x 1. P y 1. P x 2. P y 2. The position of the wafer edge, calculate the offset D of the wafer center relative to the rotation center of the carrier in the x and y directions x and D y The steps include:

[0010] e1) Calculate the image P respectively x 1. P x 2. P y 1. P y 2. The pixel position N of the wafer edge from the image start position x 1. N x 2. N y 1. N y 2;

[0011] e2) Calculate the offset D in the x direction using the following formula: x :

[0012]

[0013] Among them, N x 1 is image P x 1 The pixel position of the wafer edge from the image start position, N x 2 is image P x 2 is the pixel position of the wafer edge from the image start position, and R is the ratio between the pixel change in the photo and the physical distance the camera moves;

[0014] e3) Calculate the offset D in the y direction using the following formula y :

[0015]

[0016] Among them, N y 1 is image P y 1 The pixel position of the wafer edge from the image start position, N y 2 is image P y 2 is the pixel position of the wafer edge from the image start position, and R is the ratio between the pixel change in the photo and the physical distance the camera moves.

[0017] In one embodiment, the images P are respectively calculated x 1. Px 2. P y 1. P y The pixel position N of the wafer edge from the image start position in 2 x 1. N x 2. N y 1. N y 2 includes the following steps:

[0018] When using a color camera, convert the captured color image into a grayscale image;

[0019] The threshold segmentation method in image processing is used to set the brightness threshold range for the grayscale image to extract the highlight area;

[0020] Determine the pixel distance N between the lowest pixel point in the highlight area and the upper edge of the image. This distance is the pixel position of the edge of the wafer in the image.

[0021] In one of the embodiments, the brightness threshold range of the grayscale image is set to 200 to 255.

[0022] In one embodiment, the camera is a high-pixel camera equipped with a telecentric lens with minimal distortion.

[0023] A method for teaching position of a manipulator before wafer measurement, comprising the following steps:

[0024] Controlling the robot to place the wafer on the carrier so that the center of the wafer is approximately close to the rotation center of the carrier, wherein the radius of the wafer is smaller than the radius of the carrier;

[0025] The carrier drives the wafer to rotate to 0°, 90°, 180° and 270°, and the camera is used to take images of the wafer edge at the corresponding angles to obtain images P. x 1. P y 1. P x 2. P y 2. The camera is installed perpendicular to the plane of the carrier, and the edge of the wafer is within the field of view of the camera during the wafer rotation;

[0026] Based on the image P x 1. P y 1. P x 2. P y 2. The position of the wafer edge, calculate the offset D of the wafer center relative to the rotation center of the carrier in the x and y directions x and D y ;

[0027] Use offset D x and D y Correct the current teaching point of the robot to obtain accurate teaching point.

[0028] In one embodiment, the image P x 1. P y 1. P x 2. P y 2, the steps of calculating the offsets Dx and Dy of the wafer center relative to the rotation center of the carrier in the x-direction and the y-direction include:

[0029] Calculate the image P separately x 1. P x 2. P y 1. P y 2. The pixel position N of the wafer edge from the image start position x 1. N x 2. N y 1. N y 2;

[0030] The offset D in the x direction is calculated by the following formula: x :

[0031]

[0032] Among them, N x 1 is image P x 1 The pixel position of the wafer edge from the image start position, N x 2 is image P x 2 is the pixel position of the wafer edge from the image start position, and R is the ratio between the pixel change in the photo and the physical distance the camera moves;

[0033] The offset D in the y direction is calculated by the following formula: y :

[0034]

[0035] Among them, N y 1 is image P y 1 The pixel position of the wafer edge from the image start position, N y 2 is image P y 2 is the pixel position of the wafer edge from the image start position, and R is the ratio between the pixel change in the photo and the physical distance the camera moves.

[0036] In one embodiment, the images P are respectively calculated x 1. P x 2. P y 1. P y The pixel position N of the wafer edge from the image start position in 2 x 1. N x 2. N y1. N y 2 includes the following steps:

[0037] When using a color camera, convert the captured color image into a grayscale image;

[0038] The threshold segmentation method in image processing is used to set the brightness threshold range for the grayscale image to extract the highlight area;

[0039] Determine the pixel distance N between the lowest pixel point in the highlight area and the upper edge of the image. This distance is the pixel position of the edge of the wafer in the image.

[0040] In one of the embodiments, the brightness threshold range of the grayscale image is set to 200 to 255.

[0041] In one embodiment, the camera is a high-pixel camera equipped with a telecentric lens with minimal distortion.

[0042] The above-mentioned method for obtaining wafer offset and the method for teaching the robot position before wafer measurement do not require the edge of the wafer to be suspended in the air, and are particularly suitable for situations where the wafer radius is smaller than the carrier radius, thereby expanding the scope of application of three-dimensional morphology measurement and improving the reliability and accuracy of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic diagram of a wafer measurement device in an embodiment of the present invention;

[0044] Figure 2 A flow chart of a method for obtaining a wafer offset;

[0045] Figure 3 Schematic diagram of the pixel position at the edge of the wafer;

[0046] Figure 4 is a schematic diagram of the offset of the wafer center relative to the rotation center in the x direction;

[0047] Figure 5 Schematic diagram of the offset of the wafer center relative to the rotation center in the y direction;

[0048] Figure 6 This is a flow chart of the robot position teaching method before wafer measurement.

[0049] Explanation of the reference numerals: 1. carrier; 2. wafer; 3. measuring probe; 4. camera; 5. manipulator. DETAILED DESCRIPTION

[0050] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the specific implementation methods of the present invention are described clearly and completely below in conjunction with the accompanying drawings. Obviously, the specific details described below are only part of the embodiments of the present invention, and the present invention can also be implemented in many other embodiments different from those described herein. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0051] In this document, when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time. The directional words such as front, back, top, and bottom involved are defined by the positions of the parts in the drawings and the positions of the parts relative to each other, just for the clarity and convenience of expressing the technical solution. It should be understood that the use of the directional words should not limit the scope of protection claimed in the present invention.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0053] Figure 1 is a schematic diagram of a wafer measurement device, such as Figure 1 As shown, the wafer measurement device includes a rotation drive assembly (not shown in the figure), a Y-axis drive assembly (not shown in the figure), a measuring probe 3 and a control system. The rotation drive assembly is used to drive the wafer 2 to rotate at a constant speed around the θ axis. The rotation drive assembly includes a rotating table and a carrier 1. The rotating table is arranged on the platform 1. The carrier 1 is placed on the rotating table. During measurement, the object to be measured is placed on the carrier 1. The Y-axis drive assembly is used to drive the measuring probe 3 to move along the Y-axis direction.

[0054] Since wafer 2 needs to be rotated by carrier plate 1 when measuring, if the center of wafer 2 is not consistent with the rotation center of carrier plate 1 during rotation, wafer 2 will be displaced and data cannot be accurately measured. If there is no protective measure, wafer 2 may even be thrown out of carrier plate 1 and damaged. Therefore, how to accurately place wafer 2 on carrier plate 1 and ensure that its center coincides with the rotation center becomes a crucial step in the entire measurement process.

[0055] The present application provides a method for wafer positioning using a camera. Figure 1As shown, a camera perpendicular to the surface of the wafer is used to take pictures of the edge of the wafer when the carrier 1 is rotated to different angles. Preferably, the camera uses a high-pixel camera with a telecentric lens with minimal distortion. Camera 4 is mounted on the Y-axis drive assembly, and camera 4 is perpendicular to the plane of the carrier 1. Adjust the focal length of camera 4 so that the focus is accurate when it photographs the edge of the wafer on the carrier 1. Adjust the brightness of the light source of camera 4 so that the imaging of the wafer portion in the photo is close to or reaches full white, and the portion of the carrier 1 in the photo is darker, so that the edge of the wafer can be clearly distinguished (because the surface of the polished wafer is highly smooth, when the brightness of the light source of camera 4 is high enough, the imaging of the wafer surface will be close to or reach white).

[0056] In one embodiment of the present application, a method for obtaining a wafer offset using a camera is provided, such as Figure 2 As shown, the method comprises the following steps:

[0057] S100 : placing a wafer on a carrier 1 so that the center of the wafer is approximately close to the rotation center of the carrier 1 , wherein the radius of the wafer is smaller than the radius of the carrier 1 .

[0058] S200: The carrier plate 1 drives the wafer to rotate to angles of 0°, 90°, 180° and 270°, and the camera 4 is used to capture images of the wafer edge at corresponding angles to obtain images P x 1. P y 1. P x 2. P y 2, wherein the camera 4 is installed perpendicular to the plane of the carrier plate 1, and the edge of the wafer is within the field of view of the camera 4 during the wafer rotation process.

[0059] S300: Based on the image P x 1. P y 1. P x 2. P y 2, calculate the offset D of the wafer center relative to the rotation center of the carrier 1 in the x and y directions x and D y The images at 0° and 180° angles are used to determine the wafer offset in the x-direction. The images at 90° and 270° angles are used to determine the wafer offset in the y-direction.

[0060] In one embodiment, the image P x 1. P y 1. P x 2. P y 2, calculate the offset D of the wafer center relative to the rotation center of the carrier 1 in the x and y directions x and D y The steps include:

[0061] Step S310: Calculate the image P x 1. P x 2. P y 1. P y 2. The pixel position N of the wafer edge from the image start position x 1. N x 2. N y 1. N y 2.

[0062] Below is N x 1 as an example, a method for calculating the pixel position of the wafer edge from the image starting position is described.

[0063] Step S311: when a color camera is used, converting the captured color image into a grayscale image;

[0064] Step S312: using the threshold segmentation method in image processing to set a brightness threshold range for the grayscale image to extract a highlight area;

[0065] Step S313: Determine the pixel distance N between the bottom pixel in the highlight area and the upper edge of the image x 1, which is the pixel position of the wafer edge in the image (see Figure 3 ).

[0066] By the same method, calculate N x 2. N y 1. N y 2.

[0067] Step S320: Calculate the offset D in the x direction x .

[0068] If the center of the wafer is offset in the x direction from the rotation center of carrier 1, when carrier 1 is rotated to 0°, the wafer will shift to the right or left in the camera field of view. Similarly, at 180°, the wafer will also show a shift in the opposite direction. This shift is reflected in the image captured by the camera as a displacement change of the edge of the wafer. This shift can be quantified by comparing the pixel position of the edge of the wafer at 0° and 180°.

[0069] When the carrier 1 rotates to 0°, the camera will capture a position on the edge of the wafer (P x 1), and record the pixel position of the wafer edge from the left edge of the image, denoted as N x 1. Similarly, when the carrier plate 1 rotates to 180°, the camera will capture the position of the wafer edge again (P x 2) and record the pixel position of the wafer edge from the left edge of the image, recorded as N x 2.

[0070] like Figure 4 As shown, C1 is the tray rotation center, C2 is the 0° wafer center, C3 is the 180° wafer center, and N x 1 is the pixel position of the 0° wafer edge from the image start position, N x 2 is the pixel position of the 180° wafer edge from the image start position, D x is the offset in the x direction, D x =X2, calculate X2 by the following formula:

[0071]

[0072] Among them, N x 1. N x 2 is the number of pixels from the edge of the wafer to the starting position of the image at angles of 0° and 180° respectively, and R is the proportional coefficient between the image pixels and the actual physical distance, which is obtained in advance by the camera calibration method.

[0073] The calibration method of the ratio R is as follows:

[0074] 1. Place a wafer on the carrier 1, move the camera so that the edge of the wafer appears in the center of the camera field of view, take a picture when the camera is stationary, obtain image P1, and calculate the pixel position N1 of the wafer edge at this time;

[0075] 2. Move the camera so that the edge of the wafer is still within the camera’s field of view. When the camera is stationary, record the distance S moved and take a photo to obtain image P2. Calculate the pixel position N2 of the edge of the wafer at this time.

[0076] 3. Calculate the ratio R of the amount of pixel change in the photo to the physical distance the camera moves by the following formula:

[0077] R=|N1-N2|÷S

[0078] Step S330: Calculate the offset D in the y direction y .

[0079] If the center of the wafer is offset in the y direction from the rotation center of carrier 1, when carrier 1 is rotated to 90°, the wafer will shift to the left or right in the camera field of view. Similarly, at 270°, the wafer will also show a shift in the opposite direction. This shift is reflected in the image captured by the camera as a displacement change of the edge of the wafer. This shift can be quantified by comparing the pixel position of the edge of the wafer at 90° and 270° angles.

[0080] like Figure 5 As shown, C1 is the tray rotation center, C2 is the 90° wafer center, C3 is the 270° wafer center, and N y 1 is the pixel position of the 90° wafer edge from the image start position, N y2 is the pixel position of the 270° wafer edge from the image start position, D y is the offset in the y direction, D y =Y2, calculate Y2 by the following formula:

[0081] The offset in the y direction is calculated by the following formula:

[0082]

[0083] Among them, N y 1. N y 2 is the number of pixels from the wafer edge to the image start position at angles of 90° and 270° respectively, and R is the proportional coefficient between the image pixels and the actual physical distance, which is obtained in advance by the camera calibration method.

[0084] In another embodiment of the present application, a 5-point teaching method for a wafer measurement robot is provided, such as Figure 6 As shown, the following steps are included:

[0085] Step 610 : Control the robot 5 to place the wafer on the carrier 1 so that the center of the wafer is roughly close to the rotation center of the carrier 1 , wherein the radius of the wafer is smaller than the radius of the carrier 1 .

[0086] Step 620: The carrier plate 1 drives the wafer to rotate to the angles of 0°, 90°, 180° and 270°, and uses a camera to take images of the wafer edge at the corresponding angles to obtain images P x 1. P y 1. P x 2. P y 2, wherein the camera is installed perpendicular to the plane of the carrier plate 1, and the edge of the wafer is within the field of view of the camera during the wafer rotation;

[0087] Step 630: Based on the image P x 1. P y 1. P x 2. P y 2, calculate the offset D of the wafer center relative to the rotation center of the carrier 1 in the x and y directions x and D y ;

[0088] D x , D y The calculation method is the same as in the above-mentioned embodiment and will not be described again here.

[0089] Step 640: Use offset D x and D y The current teaching point of the robot 5 is corrected to obtain an accurate teaching point.

[0090] Through the method of the present invention, the wafer can be accurately positioned on the carrier 1, so that the center of the wafer is consistent with the rotation center of the carrier 1, so that no deviation occurs during rotation. This precise positioning not only improves the accuracy of three-dimensional morphology measurement, but also effectively avoids the risk of the wafer being thrown out during rotation, thereby ensuring the safety of the wafer. In addition, the present invention adopts a camera-assisted measurement method, which does not require the edge of the wafer to be suspended in the air, and is particularly suitable for situations where the radius of the wafer is smaller than the radius of the carrier 1, thereby expanding the scope of application of three-dimensional morphology measurement and improving the reliability and accuracy of the measurement.

[0091] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for obtaining a wafer offset, characterized in that: The following steps are involved: Placing a wafer on a carrier so that the center of the wafer is approximately close to the rotation center of the carrier, wherein the radius of the wafer is smaller than the radius of the carrier; The carrier drives the wafer to rotate to 0°, 90°, 180° and 270°, and the camera is used to take images of the wafer edge at the corresponding angles to obtain images P. x 1. P y 1. P x 2. P y 2. The camera is installed perpendicular to the plane of the carrier, and the edge of the wafer is within the field of view of the camera during the wafer rotation; Based on the image P x 1. P y 1. P x 2. P y 2. The position of the wafer edge, calculate the offset D of the wafer center relative to the rotation center of the carrier in the x and y directions x and D y .

2. The method for obtaining wafer offset according to claim 1, characterized in that: The image P x 1. P y 1. P x 2. P y 2. The position of the wafer edge, calculate the offset D of the wafer center relative to the rotation center of the carrier in the x and y directions x and D y The steps include: e1) Calculate the image P respectively x 1. P x 2. P y 1. P y 2. The pixel position N of the wafer edge from the image start position x 1. N x 2. N y 1. N y 2; e2) Calculate the offset D in the x direction using the following formula: x : Among them, N x 1 is image P x 1 The pixel position of the wafer edge from the image start position, N x 2 is image P x 2 is the pixel position of the wafer edge from the image start position, and R is the ratio between the pixel change in the photo and the physical distance the camera moves; e3) Calculate the offset D in the y direction using the following formula y : Among them, N y 1 is image P y 1 The pixel position of the wafer edge from the image start position, N y 2 is image P y 2 is the pixel position of the wafer edge from the image start position, and R is the ratio between the pixel change in the photo and the physical distance the camera moves.

3. The method for obtaining wafer offset according to claim 2, characterized in that: The images P are calculated respectively x 1. P x 2. P y 1. P y The pixel position N of the wafer edge from the image start position in 2 x 1. N x 2. N y 1. N y 2 includes the following steps: When using a color camera, convert the captured color image into a grayscale image; The threshold segmentation method in image processing is used to set the brightness threshold range for the grayscale image to extract the highlight area; Determine the pixel distance N between the lowest pixel point in the highlight area and the upper edge of the image. This distance is the pixel position of the edge of the wafer in the image.

4. The method for obtaining wafer offset according to claim 3, characterized in that: The brightness threshold range of the grayscale image is set to 200 to 255.

5. The method for obtaining wafer offset according to claim 1, characterized in that: The camera is a high-pixel camera equipped with a telecentric lens with minimal distortion.

6. A method for teaching robot position before wafer measurement, characterized in that: The following steps are involved: Controlling the robot to place the wafer on the carrier so that the center of the wafer is approximately close to the rotation center of the carrier, wherein the radius of the wafer is smaller than the radius of the carrier; The carrier drives the wafer to rotate to 0°, 90°, 180° and 270°, and the camera is used to take images of the wafer edge at the corresponding angles to obtain images P. x 1. P y 1. P x 2. P y 2. The camera is installed perpendicular to the plane of the carrier, and the edge of the wafer is within the field of view of the camera during the wafer rotation; Based on the image P x 1. P y 1. P x 2. P y 2. The position of the wafer edge, calculate the offset D of the wafer center relative to the rotation center of the carrier in the x and y directions x and D y ; Use offset D x and D y Correct the current teaching point of the robot to obtain accurate teaching point.

7. The method for teaching the position of a manipulator before wafer measurement according to claim 6, characterized in that: The image P x 1. P y 1. P x 2. P y 2. The position of the wafer edge, calculate the offset D of the wafer center relative to the rotation center of the carrier in the x and y directions x and D y The steps include: Calculate the image P separately x 1. P x 2. P y 1. P y 2. The pixel position N of the wafer edge from the image start position x 1. N x 2. N y 1. N y 2; The offset D in the x direction is calculated by the following formula: x : Among them, N x 1 is image P x 1 The pixel position of the wafer edge from the image start position, N x 2 is image P x 2 is the pixel position of the wafer edge from the image start position, and R is the ratio between the pixel change in the photo and the physical distance the camera moves; The offset D in the y direction is calculated by the following formula: y : Among them, N y 1 is image P y 1 The pixel position of the wafer edge from the image start position, N y 2 is image P y 2 is the pixel position of the wafer edge from the image start position, and R is the ratio between the pixel change in the photo and the physical distance the camera moves.

8. The method for teaching the position of a manipulator before wafer measurement according to claim 7, characterized in that: The images P are calculated respectively x 1. P x 2. P y 1. P y The pixel position N of the wafer edge from the image start position in 2 x 1. N x 2. N y 1. N y 2 includes the following steps: When using a color camera, convert the captured color image into a grayscale image; The threshold segmentation method in image processing is used to set the brightness threshold range for the grayscale image to extract the highlight area; Determine the pixel distance N between the lowest pixel point in the highlight area and the upper edge of the image. This distance is the pixel position of the edge of the wafer in the image.

9. The method for teaching robot position before wafer measurement according to claim 8, characterized in that: The brightness threshold range of the grayscale image is set to 200 to 255.

10. The method for obtaining wafer offset according to claim 6, characterized in that: The camera is a high-pixel camera equipped with a telecentric lens with minimal distortion.

Images