Wafer automatic centering system and method

Abstract

The present application belongs to the field of wafer precision calibration, in particular to a wafer automatic centering system and method, comprising: a robot motion system, a camera sensor, a camera controller and an upper computer; the robot motion system is installed with a wafer and connected with the upper computer; the robot motion system is provided with the camera sensor, the camera sensor is arranged directly below the wafer, the field of view direction of the camera sensor is towards the bottom of the wafer, and the camera sensor moves along the X-axis direction of the wafer; the camera sensor is connected with the camera controller; the camera controller is connected with the upper computer; the upper computer is used for controlling the robot motion system, acquiring the teaching position coordinate value of the robot motion system; at the same time, receiving the wafer position deviation value sent by the camera controller and processing to obtain the wafer position coordinate and send the wafer position coordinate to the robot motion system, controlling the motion of the robot motion system and realizing the calibration of the wafer center transmission position.

Description

Technical Field

[0001] This invention belongs to the field of wafer precision calibration, specifically a wafer automatic alignment system and method. Background Technology

[0002] During wafer transport, slippage can occur on the robot's hand due to various reasons. If this slippage is not properly controlled, it can affect the stability of subsequent coating processes, leading to defects in the developing process and ultimately impacting chip production yield. Current automated compensation solutions for mass production use two through-beam sensors to calculate the wafer's coordinate variation by measuring the chord length. However, this method involves point measurement with a limited number of measurement points, potentially resulting in significant errors. This approach primarily utilizes the principle of visual imaging, where, with a fixed focal length, the distance represented by each pixel is fixed after imaging calibration at that focal length. Furthermore, this method measures a circular arc over a considerable number of points, allowing for a high tolerance for error. Therefore, designing a wafer alignment system capable of correcting or compensating for slippage, enabling smooth wafer transport and meeting various process specifications, is crucial. Summary of the Invention

[0003] The purpose of this invention is to provide an automatic wafer alignment system and method, which has a simple structure, low cost, multiple detection points, high precision, good stability, and a wide range of applications. It can be implemented in existing robot systems by adding some sensors, and overcomes the shortcomings of having a large number of measurement points and a high tolerance for error.

[0004] The technical solution adopted by the present invention to achieve the above objectives is: an automatic wafer alignment system, comprising: a robot motion system, a camera sensor, a camera controller, and a host computer;

[0005] The robot motion system is equipped with a wafer and connected to a host computer, and is used to move according to the control instructions of the host computer.

[0006] The robot motion system is equipped with a camera sensor, which is located directly below the wafer. The field of view of the camera sensor faces the bottom of the wafer, and the camera sensor moves along the X-axis of the wafer.

[0007] The camera sensor is connected to the camera controller and is used to send the acquired wafer images to the camera controller for processing.

[0008] The camera controller is connected to the host computer and is used to receive the actual position image of the wafer center sent by the camera sensor and the reference position image during the teaching of the robot motion system. It compares the two images, obtains the wafer position deviation value, and sends the obtained wafer position deviation value to the host computer.

[0009] The host computer is used to control the robot motion system and obtain the teaching position coordinates of the robot motion system. At the same time, it receives the wafer position deviation value sent by the camera controller, processes it to obtain the wafer placement position coordinates, and sends the wafer placement position coordinates to the robot motion system to perform motion control on the robot motion system and realize the calibration of the wafer center transport position.

[0010] The robot motion system includes: a robot controller and connected to it an X-axis linear motion slide, a Z-axis linear motion slide, a θ-axis rotary table, and a wafer gripper;

[0011] One end of the Z-axis linear motion slide is fixedly connected to the slider of the X-axis linear motion slide, so that the Z-axis linear motion slide moves along the X-axis direction.

[0012] The slider of the Z-axis linear motion slide is fixed with an θ-axis turntable, which is used to place the wafer;

[0013] The wafer gripper is mounted on the Z-axis linear motion slide and moves synchronously along the Z-axis with the Z-axis linear motion slide to grip the wafer and place the wafer on the θ-axis turntable; the wafer gripper drives the wafer to move along the X-axis or Y-axis according to the robot controller command to achieve wafer centering calibration.

[0014] The robot controller is connected to the host computer.

[0015] The field of view of the camera sensor covers at least 1 / 6 of the arc length of the wafer.

[0016] The camera sensor is fixed on the slider of the X-axis linear motion slide to move along the X-axis with the wafer.

[0017] It also includes a backlight, which is used to make the edge of the wafer stand out in terms of brightness and darkness within the field of view of the camera sensor, so as to provide supplemental lighting for the wafer.

[0018] The backlight is positioned directly above the wafer. The top of the robot motion system is fixedly connected to the backlight via a lamp holder, so that the backlight moves along the X-axis direction with the robot motion system and remains fixed relative to the robot motion system.

[0019] An automated wafer alignment method includes the following steps:

[0020] 1) Teach the robot motion system to obtain the coordinates of the reference wafer center position when the robot motion system places the wafer, and take pictures of the wafer within the field of view by the camera sensor to obtain the reference position image of the wafer when the robot motion system is being taught.

[0021] 2) After the wafer gripper of the robot motion system picks up the wafer and places it on the θ-axis turntable, the camera sensor takes pictures of the wafer within the field of view and sends the acquired image of the actual position of the wafer center to the camera controller for processing.

[0022] 3) The camera controller receives the actual wafer center position image sent by the camera sensor, compares it with the reference position image during teaching, obtains the wafer position deviation value, and sends it to the host computer.

[0023] 4) The host computer obtains the wafer placement position coordinates based on the wafer position deviation value and the reference wafer center position coordinates, and sends them to the robot motion system to perform motion control on the robot motion system to achieve the calibration of the wafer center transport position.

[0024] Step 3) specifically includes:

[0025] (1) The camera controller receives the image of the actual position of the wafer center captured by the camera sensor, and after preprocessing, obtains the image of the preprocessed two-dimensional plane.

[0026] (2) Based on the characteristics of arc length and angle of the preprocessed two-dimensional plane image, the radius of the wafer is calculated, and then the position of the wafer center in the coordinate system within the camera's field of view is calculated.

[0027] (3) Compare the preprocessed two-dimensional plane image with the reference position image, taking the wafer center coordinates as the origin, to obtain the actual distances of the deviations between the X-axis and Y-axis of the two-dimensional plane image and the reference position image, i.e.:

[0028] Based on the position of the wafer center within the camera's field of view, the pixel deviation values ​​of the X and Y axes of the two-dimensional plane image are obtained. Based on the actual distance and pixel ratio, 1 pixel equals N millimeters, thus obtaining the actual deviation values ​​of the X and Y axes of the two-dimensional plane image, i.e., the wafer position deviation values ​​(ΔX, ΔY). Step (3), based on the characteristics of the two-dimensional plane image having arc length and angle, calculates the radius of the wafer, specifically as follows:

[0029] The radius of the wafer is:

[0030] R = 180°L / nπ

[0031] Where R is the radius of the wafer, n is the central angle corresponding to the arc length between the two points where the edge of the backlight intersects with the wafer in the two-dimensional plane image, and L is the arc length corresponding to the central angle;

[0032] Given the central angle measure and the corresponding arc length, the radius R of the wafer can be obtained.

[0033] Step 4) specifically includes:

[0034] The host computer transforms the wafer position deviation value (△X, △Y) calculated by the camera controller into the robot coordinate system and sends it to the robot controller.

[0035] The robot motion system performs addition and subtraction operations on the taught position coordinates and the wafer position deviation after coordinate transformation to obtain the actual wafer placement coordinates. The robot motion system controls the wafer grippers to adjust the wafer based on the actual wafer placement coordinates, thereby calibrating the wafer center transport position.

[0036] The reference wafer center position coordinates of the robot motion system are the position coordinates R of the wafer gripper in the camera coordinate system and the rotation coordinate θ of the θ-axis turntable, that is, the coordinates (R, θ) in polar coordinates.

[0037] The robot motion system controls the wafer grippers to adjust the wafer based on the actual coordinates of the wafer placement.

[0038] When the wafer position deviation values ​​(△X, △Y) are both positive, compensation is performed by addition based on the coordinate values ​​(R, θ) of the reference wafer center position.

[0039] When the wafer position deviation values ​​(△X, △Y) are both negative, compensation is performed by subtraction based on the coordinate values ​​(R, θ) of the reference wafer center position.

[0040] When the wafer position deviation values ​​(△X, △Y) are both positive and negative, compensation is performed by addition and subtraction operations based on the coordinate values ​​(R, θ) of the reference wafer center position.

[0041] Wherein, the wafer position deviation value = wafer center coordinates in the two-dimensional plane image - reference wafer center coordinates.

[0042] The present invention has the following beneficial effects and advantages:

[0043] 1. This invention employs two system docking methods that match the CCD measurement system and the robot controller, enabling the upgrade and optimization of a robot without calibration functionality to include this calibration function;

[0044] 2. This invention analyzes many pixels within an image, fits and calculates the center of a circle, allows for a large error, and can eliminate necessary error points, resulting in a large amount of redundancy;

[0045] 3. The principle of this invention is simple. By integrating a robot with a CCD system, it can achieve various robot applications, and due to its multi-point detection and calculation capabilities, it has high accuracy. The overall system accuracy can reach ±0.1mm.

[0046] 4. This invention can be implemented by adding some sensors to existing wafer robot systems. It enables customized opening and closing within the machine, saving necessary process transport time. Attached Figure Description

[0047] Figure 1 A schematic diagram of the structural framework of the wafer alignment system of the present invention;

[0048] Figure 2 Front view of the robot motion system of the present invention;

[0049] Figure 3 The present invention provides a two-dimensional planar image of a wafer under the field of view of a camera sensor.

[0050] Figure 4 The diagram illustrating the principle of output deviation of the camera controller of the present invention. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0052] like Figure 1 As shown, the present invention mainly comprises five parts: a robot motion system, a camera sensor, a camera controller, a backlight, and a host computer;

[0053] A wafer is mounted on the robot motion system and connected to a host computer for movement according to the control commands of the host computer. The robot motion system is equipped with a camera sensor, which is located directly below the wafer, with the field of view of the camera sensor facing the bottom of the wafer, and the camera sensor moves along the X-axis of the wafer; and ensures that at least 1 / 6 of the arc length is within the camera's field of view. The robot system is responsible for transporting the wafer so that the wafer is above the camera sensor.

[0054] The camera sensor is connected to the camera controller and is used to send the acquired wafer images to the camera controller for processing;

[0055] The camera controller is connected to the host computer to receive the actual position image of the wafer center sent by the camera sensor and the reference position image during the teaching of the robot motion system. It compares the two images, obtains the wafer position deviation value, and sends the obtained wafer position deviation value to the host computer.

[0056] The camera controller's function is to process images captured by the camera sensor to determine the deviation value of the center of the circle. (Processing: Images captured by the camera sensor are two-dimensional plane images composed of pixels. After the image pixels are calibrated by a calibration plate, each pixel on the plane corresponds to a certain actual distance, i.e., 1 pixel equals N millimeters. Since the total number of pixels in the camera is fixed, the images captured within the entire camera's field of view form a planar coordinate system of X and Y. When the controller is set to process a specific area within the captured image (1 / 6 of the arc within the field of view), the radius can be calculated because the image within this area has arc length and angle characteristics. This allows the calculation of the center's position within the camera's field of view coordinate system. The arc of the wafer edge is segmented and calculated, and then the center is fitted to obtain the wafer's center position. The controller also has the function of calculating the difference between two captured images; one image is set as the baseline, and the difference between the subsequent positions and the baseline is the deviation value of the wafer's center position within the camera's field of view coordinate system.)

[0057] The host computer is used to control the robot motion system and obtain the teaching position coordinates of the robot motion system. At the same time, it receives the wafer position deviation value sent by the camera controller, processes it to obtain the wafer placement position coordinates, and sends the wafer placement position coordinates to the robot motion system to perform motion control on the robot motion system and realize the calibration of the wafer center transport position.

[0058] The host computer coordinates the robot system and the camera controller system. It sends the wafer position deviation value calculated by the camera controller, after coordinate transformation, to the robot controller. The robot then performs addition and subtraction operations on the coordinate values ​​at the robot's base target position (R and θ coordinates of the taught position) during wafer placement to correct wafer transfer deviations and calibrate the wafer's center transport position. The sent wafer position data, after specific calculations, guides the robot to compensate for deviations.

[0059] The backlight is positioned above the wafer, highlighting the contrast between light and shadow at the wafer's edge within the camera's field of view. This provides supplemental lighting for the wafer, enabling more accurate edge detection. Figure 3 As shown, this invention provides a two-dimensional planar image of a wafer within the field of view of the camera sensor. The top of the robot motion system is fixedly connected to a backlight via a lamp holder, enabling the backlight to move along the X-axis direction with the robot motion system while maintaining a fixed position relative to the robot motion system.

[0060] The camera controller and host computer system belong to the control system and are used to analyze the linkage between camera images and data.

[0061] like Figure 2 As shown, the robot motion system of the present invention includes: a robot controller and X-axis linear motion slide, Z-axis linear motion slide, θ-axis rotary table and wafer gripper connected thereto;

[0062] One end of the Z-axis linear motion slide is fixedly connected to the slider of the X-axis linear motion slide, so that the Z-axis linear motion slide moves along the X-axis direction.

[0063] The slider of the Z-axis linear motion slide is fixed with an θ-axis turntable, which is used to place the wafer;

[0064] The wafer gripper is mounted on the Z-axis linear motion slide and moves synchronously along the Z-axis with the Z-axis linear motion slide. It is used to grip the wafer and place the wafer on the θ-axis turntable. The wafer gripper drives the wafer to move along the X-axis or Y-axis according to the robot controller command to achieve wafer centering calibration.

[0065] The robot controller is connected to a host computer. The camera sensor is fixed on the slider of the X-axis linear motion slide to move along the X-axis with the wafer.

[0066] This embodiment uses a self-designed multi-axis motion system, but existing wafer robots, such as the SANKYO SR7165-1010 wafer robot, can also be used.

[0067] The robot motion system of this application first needs to confirm the concentric position of the wafer on the gripper and the center defined by the gripper stop on the robot's gripper. Since the limited range of the robot's finger stop is larger than the size of the wafer in actual use (otherwise the robot cannot grasp the wafer smoothly), a stop ring is needed on the stop on the edge of the finger so that the center of the wafer coincides with the center defined by the finger stop, thus making the center defined by the finger stop concentric with the center of the wafer.

[0068] The robot motion system functions to transport the wafer and perform final compensation. It has X, Z, θ, and R axes. It can transport the wafer and correct its position in the X and Y directions (i.e., the planar direction) based on position error information fed back from the host computer. The camera sensor is used to take pictures at a specific position when the robot's gripper moves the wafer to a specific height above the camera (to meet the requirements of camera photography and cleaning, which requires maintaining a specific focal length) and the edge of the wafer is within 1 / 6 of the camera's field of view. This specific position allows the camera sensor, wafer, and backlight to form a relatively fixed position, but this specific position will change depending on the robot's X-axis position.

[0069] This invention discloses an automatic wafer alignment method, comprising the following steps:

[0070] 1) Teach the robot motion system to obtain the coordinates of the reference wafer center position when the robot motion system places the wafer, and take pictures of the wafer within the field of view by the camera sensor to obtain the reference position image of the wafer when the robot motion system is being taught.

[0071] 2) After the wafer gripper of the robot motion system picks up the wafer and places it on the θ-axis turntable, the camera sensor takes pictures of the wafer within the field of view and sends the acquired image of the actual position of the wafer center to the camera controller for processing.

[0072] 3) The camera controller receives the actual wafer center position image sent by the camera sensor, compares it with the reference position image during teaching, obtains the wafer position deviation value, and sends it to the host computer.

[0073] 3-1) The camera controller receives the image of the actual position of the wafer center captured by the camera sensor, and after preprocessing, obtains the preprocessed two-dimensional plane image;

[0074] 3-2) Based on the characteristics of arc length and angle in the preprocessed two-dimensional plane image, the radius of the wafer is calculated, and then the position of the wafer center in the coordinate system within the camera's field of view is calculated;

[0075] The radius of the wafer is:

[0076] R = 180°L / nπ

[0077] Where R is the radius of the wafer, n is the central angle corresponding to the arc length between the two points where the edge of the backlight intersects with the wafer in the two-dimensional plane image, and L is the arc length corresponding to the central angle;

[0078] Given the central angle measure and the corresponding arc length, the radius R of the wafer can be obtained.

[0079] 3-3) Compare the preprocessed two-dimensional plane image with the reference position image, taking the wafer center coordinates as the origin, to obtain the actual distance of the deviation between the two-dimensional plane image's X-axis and Y-axis and the reference position image, i.e.:

[0080] like Figure 4 As shown in the diagram illustrating the principle of camera controller output deviation of the present invention, the pixel deviation values ​​of the X-axis and Y-axis of the two-dimensional plane image are obtained based on the position of the wafer center in the coordinate system within the camera's field of view. Based on the actual distance and pixel ratio, 1 pixel equals N millimeters, and thus the actual deviation values ​​of the X-axis and Y-axis of the two-dimensional plane image are obtained, i.e., the wafer position deviation values ​​(△X, △Y).

[0081] 4) The host computer obtains the wafer placement position coordinates based on the wafer position deviation value and the reference wafer center position coordinates, and sends them to the robot motion system. The host computer then performs motion control on the robot motion system to calibrate the wafer center transport position. Specifically:

[0082] The host computer transforms the wafer position deviation value (△X, △Y) calculated by the camera controller into the robot coordinate system and sends it to the robot controller.

[0083] The robot motion system performs addition and subtraction operations on the taught position coordinates and the wafer position deviation values ​​after coordinate transformation to obtain the actual wafer placement coordinates. The robot motion system then controls the wafer grippers to adjust the wafer based on these actual placement coordinates. Specifically:

[0084] The reference wafer center position coordinates of the robot motion system are the position coordinates R of the wafer gripper in the camera coordinate system and the rotation coordinate θ of the θ-axis turntable, that is, the coordinates (R, θ) in polar coordinates.

[0085] When the wafer position deviation values ​​(△X, △Y) are both positive, compensation is performed by subtraction based on the coordinate values ​​(R, θ) of the reference wafer center position.

[0086] When the wafer position deviation values ​​(△X, △Y) are both negative, compensation is performed by addition based on the coordinate values ​​(R, θ) of the reference wafer center position.

[0087] When the wafer position deviation values ​​(△X, △Y) are both positive and negative, compensation is performed by addition and subtraction operations based on the coordinate values ​​(R, θ) of the reference wafer center position to complete the compensation and achieve the calibration of the wafer center transport position.

[0088] Wherein, the wafer position deviation value = wafer center coordinates in the two-dimensional plane image - reference wafer center coordinates.

[0089] This position is established as the reference in the coordinate system of the image captured by the camera sensor when it takes a picture. With the wafers in a concentric position, the positions for each wafer pick-up and placement are taught. During normal wafer transport, when the robot picks up a wafer again, the camera sensor takes a picture of the wafer. The camera controller performs image processing and calculations to determine the deviation between the current position of the wafer on the robot's finger and the reference position. This deviation is then communicated to the host computer. The host computer performs coordinate transformation based on the deviation value obtained from the image and performs addition and subtraction compensation calculations with the taught coordinate values. Based on the deviation, it calculates the corresponding compensation value required by the robot. When the robot places the wafer, it places it according to the calculated coordinate values, and the coordinates at the wafer placement teaching position are adjusted for compensation.

[0090] This invention is based on a simple principle. By integrating a robot with a CCD system, it enables various robot applications, and due to its multi-point detection and computation capabilities, it achieves high accuracy. The overall system accuracy can reach ±0.1mm. This can be achieved by adding a few sensors to existing wafer robot systems. It also allows for customized opening and closing within the machine, saving necessary process transport time.

[0091] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, extensions, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. An automated wafer alignment system, characterized in that, include: Robot motion system, camera sensor, camera controller, and host computer; The robot motion system is equipped with a wafer and connected to a host computer, and is used to move according to the control instructions of the host computer. The robot motion system is equipped with a camera sensor, which is located directly below the wafer. The field of view of the camera sensor faces the bottom of the wafer, and the camera sensor moves along the X-axis of the wafer. The camera sensor is connected to the camera controller and is used to send the acquired wafer images to the camera controller for processing. The camera controller is connected to the host computer and is used to receive the actual position image of the wafer center sent by the camera sensor and the reference position image during the teaching of the robot motion system. It compares the two images, obtains the wafer position deviation value, and sends the obtained wafer position deviation value to the host computer. The host computer is used to control the robot motion system and obtain the teaching position coordinates of the robot motion system. At the same time, it receives the wafer position deviation value sent by the camera controller, processes it to obtain the wafer placement position coordinates, and sends the wafer placement position coordinates to the robot motion system to perform motion control on the robot motion system and realize the calibration of the wafer center transport position.

2. The automatic wafer alignment system according to claim 1, characterized in that, The robot motion system includes: a robot controller and connected to it an X-axis linear motion slide, a Z-axis linear motion slide, a θ-axis rotary table, and a wafer gripper; One end of the Z-axis linear motion slide is fixedly connected to the slider of the X-axis linear motion slide, so that the Z-axis linear motion slide moves along the X-axis direction. The slider of the Z-axis linear motion slide is fixed with an θ-axis turntable, which is used to place the wafer; The wafer gripper is mounted on the Z-axis linear motion slide and moves synchronously along the Z-axis with the Z-axis linear motion slide to grip the wafer and place the wafer on the θ-axis turntable; the wafer gripper drives the wafer to move along the X-axis or Y-axis according to the robot controller command to achieve wafer centering calibration. The robot controller is connected to the host computer.

3. The automatic wafer alignment system according to claim 1, characterized in that, The field of view of the camera sensor covers at least 1 / 6 of the arc length of the wafer.

4. The automatic wafer alignment system according to claim 1, characterized in that, The camera sensor is fixed on the slider of the X-axis linear motion slide to move along the X-axis with the wafer.

5. The automatic wafer alignment system according to claim 1, characterized in that, It also includes a backlight, which is used to make the edge of the wafer stand out in terms of brightness and darkness within the field of view of the camera sensor, so as to provide supplemental lighting for the wafer. The backlight is positioned directly above the wafer. The top of the robot motion system is fixedly connected to the backlight via a lamp holder, so that the backlight moves along the X-axis direction with the robot motion system and remains fixed relative to the robot motion system.

6. A method for automatic wafer alignment, characterized in that, Includes the following steps: 1) Teach the robot motion system to obtain the coordinates of the reference wafer center position when the robot motion system places the wafer, and take pictures of the wafer within the field of view by the camera sensor to obtain the reference position image of the wafer when the robot motion system is being taught. 2) After the wafer gripper of the robot motion system picks up the wafer and places it on the θ-axis turntable, the camera sensor takes pictures of the wafer within the field of view and sends the acquired image of the actual position of the wafer center to the camera controller for processing. 3) The camera controller receives the actual wafer center position image sent by the camera sensor, compares it with the reference position image during teaching, obtains the wafer position deviation value, and sends it to the host computer. 4) The host computer obtains the wafer placement position coordinates based on the wafer position deviation value and the reference wafer center position coordinates, and sends them to the robot motion system to perform motion control on the robot motion system to achieve the calibration of the wafer center transport position.

7. The automatic wafer alignment method according to claim 6, characterized in that, Step 3) specifically includes: (1) The camera controller receives the image of the actual position of the wafer center captured by the camera sensor, and after preprocessing, obtains the image of the preprocessed two-dimensional plane. (2) Based on the characteristics of arc length and angle of the preprocessed two-dimensional plane image, the radius of the wafer is calculated, and then the position of the wafer center in the coordinate system within the camera's field of view is calculated. (3) Compare the preprocessed two-dimensional plane image with the reference position image, taking the wafer center coordinates as the origin, to obtain the actual distances of the deviations between the X-axis and Y-axis of the two-dimensional plane image and the reference position image, i.e.: Based on the position of the wafer center in the coordinate system within the camera's field of view, the pixel deviation values ​​of the X and Y axes of the two-dimensional plane image are obtained. Based on the actual distance and pixel ratio, 1 pixel equals N millimeters, and then the actual deviation values ​​of the X and Y axes of the two-dimensional plane image are obtained, that is, the wafer position deviation values ​​(△X, △Y).

8. The automatic wafer alignment method according to claim 7, characterized in that, Step (2) involves calculating the radius of the wafer based on the characteristics of arc length and angle in a two-dimensional plane image. Specifically: The radius of the wafer is: R = 180°L / nπ Where R is the radius of the wafer, n is the central angle corresponding to the arc length between the two points where the edge of the backlight intersects with the wafer in the two-dimensional plane image, and L is the arc length corresponding to the central angle; Given the central angle measure and the corresponding arc length, the radius R of the wafer in the two-dimensional plane image can be obtained.

9. The automatic wafer alignment method according to claim 6, characterized in that, Step 4) specifically includes: The host computer transforms the wafer position deviation value (△X, △Y) calculated by the camera controller into the robot coordinate system and sends it to the robot controller. The robot motion system performs addition and subtraction operations on the taught position coordinates and the wafer position deviation after coordinate transformation to obtain the actual wafer placement coordinates. The robot motion system controls the wafer grippers to adjust the wafer based on the actual wafer placement coordinates, thereby calibrating the wafer center transport position.

10. The automatic wafer alignment method according to claim 9, characterized in that, The reference wafer center position coordinates of the robot motion system are the position coordinates R of the wafer gripper in the camera coordinate system and the rotation coordinate θ of the θ-axis turntable, that is, the coordinates (R, θ) in polar coordinates. The robot motion system controls the wafer grippers to adjust the wafer based on the actual coordinates of the wafer placement. When the wafer position deviation values ​​(△X, △Y) are both positive, compensation is performed by subtraction based on the coordinate values ​​(R, θ) of the reference wafer center position. When the wafer position deviation values ​​(△X, △Y) are both negative, compensation is performed by addition based on the coordinate values ​​(R, θ) of the reference wafer center position. When the wafer position deviation values ​​(△X, △Y) are both positive and negative, compensation is performed by addition and subtraction based on the coordinate values ​​(R, θ) of the reference wafer center position. Wherein, wafer position deviation value = wafer center coordinates in two-dimensional plane image - reference wafer center coordinates.

Images