Wafer offset detection method

Abstract

This invention provides a wafer offset detection method, comprising: acquiring a first edge position of a scanning point scanned by a sensor to the edge of the wafer, wherein the sensor generates a first scanning signal when scanning the scanning point; acquiring a first distance between the position of a robot arm and a second position when the first scanning signal is generated; acquiring a second edge position of the scanning point when the robot arm is located in the second position by using the first edge position and the first distance; acquiring the offset center position when the wafer is offset by using the second edge position and the radius of the wafer; and acquiring the wafer offset by using the positional relationship between the offset center position and the reference center position. This invention eliminates the need for a centering unit in the equipment, avoiding the step of transporting the wafer to the centering unit, thereby improving process efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method for detecting wafer offset. Background Technology

[0002] In electronic semiconductor manufacturing equipment, wafer handling robots are responsible for transferring wafers between various workstations. As the core moving component of the machine, the accuracy of wafer placement directly affects the yield of semiconductor processing. Therefore, improving the accuracy of wafer handling is of paramount importance.

[0003] In existing technologies, to improve the accuracy of wafer placement by robotic arms, the wafer is placed in a mechanical or optical alignment unit before being fed into a key process unit, such as the spin coating unit. The alignment unit can acquire the wafer's positional offset data and correct the wafer's offset relative to the robotic fingers, so that the wafer fed into the process unit each time is consistent with the taught position, thereby ensuring process stability. However, this method reduces process efficiency.

[0004] Therefore, it is necessary to develop a novel wafer offset detection method to improve some of the problems mentioned above in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a wafer offset detection method that can improve process efficiency.

[0006] To achieve the above objectives, the wafer offset detection method provided by the present invention includes the following steps:

[0007] Set the reference center position of the wafer;

[0008] A robotic arm is used to move the wafer from a first position to a second position along the path.

[0009] The first edge position of the scanning point scanned by the sensor to the edge of the wafer is obtained, and a first scanning signal is generated when the sensor scans the scanning point;

[0010] Obtain the first distance between the position of the robotic arm and the second position when the first scanning signal is generated;

[0011] The second edge position of the scanning point is obtained by using the first edge position and the first distance when the robotic arm is in the second position;

[0012] The offset center position when the wafer is offset is obtained by using the second edge position and the radius of the wafer;

[0013] The offset of the wafer is obtained by the positional relationship between the offset center position and the reference center position.

[0014] The beneficial effects of the wafer offset detection method provided by this invention are as follows: During the process of the robot arm moving the wafer from a first position to a second position along the path, the first edge position of the scanning point of the sensor scanning the wafer edge is obtained and the first scanning signal is generated. The first distance between the position of the robot arm when the first scanning signal is generated and the second position is obtained. The second edge position is obtained by adding the first distance to the first edge position in the moving direction of the robot arm. The wafer edge is approximately circular, and the second edge position is a point on the circle. The offset center position of the wafer that is currently offset can be obtained by using the second edge position and the radius of the wafer. By calculating the relationship between the reference center position and the offset center position, the current offset of the wafer can be obtained. The offset of the wafer can be obtained without setting up an alignment unit in the equipment, thus avoiding the step of transporting the wafer to the alignment unit and improving process efficiency.

[0015] Optionally, the first position is the extended position of the robotic arm, the second position is the retracted position of the robotic arm, and the first scanning signal is the signal output when the wafer changes from obscuring the sensor to not obscuring it. Its advantages are: during the process of the robotic arm returning from the extended position to the retracted position, the distance between the offset center position and the reference center position is relatively close, which helps to reduce errors and improve the accuracy of offset detection; at the same time, the acceleration of the robotic arm is negative when approaching the retracted position, which helps to improve the sensor's recognition accuracy of the wafer's edge, thereby improving the accuracy of offset detection.

[0016] Optionally, obtaining the first edge position of the scanning point scanned by the sensor to the edge of the wafer includes: placing the wafer on a robotic arm so that the center of the wafer is located at the reference center position; using the robotic arm to move the wafer to obtain a second center position when the sensor is obscured by the edge of the wafer; using the robotic arm to continue moving the wafer to obtain a third center position when the wafer no longer obscures the sensor; and obtaining the first edge position using the radius of the wafer, the second center position, and the third center position. Its advantages are: it helps to reduce the setting error of the sensor and improves the accuracy of obtaining the first edge position.

[0017] Optionally, obtaining the offset center position of the wafer offset using the second edge position and the wafer radius includes: obtaining two second edge positions using two sensors; obtaining two undetermined center positions using the two second edge positions and the wafer radius; calculating the distances between the two undetermined center positions and the reference center position, and selecting the closer one as the offset center position. The advantages are: the wafer is approximately circular, and the second edge position is a point on the circle. When determining the offset center position using the two second edge positions and the wafer radius, two undetermined center positions are obtained. By judging the distances between the two undetermined center positions and the reference center position, the offset center position can be determined, reducing the number of sensors used, simplifying the equipment structure design, and lowering costs.

[0018] Optionally, the step of using a robotic arm to move the wafer includes: the robotic arm moving the wafer at a first speed; and when the distance between the edge of the wafer and the location of the sensor is less than a threshold, the robotic arm moving the wafer at a second speed, where the second speed is less than the first speed. The beneficial effect is that by reducing the speed of the robotic arm when the wafer is close to the sensor, the sensor's accuracy in recognizing the wafer edge is improved, signal hysteresis is reduced, and the accuracy of offset detection is enhanced.

[0019] Optionally, the sensor is a through-beam sensor, and the through-beam sensor is positioned perpendicular to the wafer.

[0020] Optionally, the sensor is connected to a servo system that drives the movement of the robotic arm, and the servo system is used to obtain the distance the robotic arm moves after the sensor generates a signal.

[0021] Optionally, the sensors are respectively disposed on both sides of the moving path of the center of the wafer.

[0022] Optionally, before acquiring the first edge position of the scanning point scanned by the sensor to the edge of the wafer, the method further includes: acquiring the delay of the sensor and the moving speed of the robot; and compensating for the first edge position and the second edge position based on the sensor delay and the moving speed of the robot. The advantage of this method is that compensating for the sensor delay helps improve the positional accuracy of the scanning point scanned by the sensor to the edge of the wafer.

[0023] Optionally, obtaining the delay of the sensor includes: using a robotic arm to move the wafer at a third speed and a fourth speed respectively; obtaining the third edge position and the fourth edge position of the scanning point scanned by the sensor to the edge of the wafer respectively; and obtaining the delay of the sensor based on the distance between the fourth edge position and the third edge position and the speed difference between the fourth speed and the third speed.

[0024] Optionally, before obtaining the first edge position of the scanning point scanned by the sensor to the edge of the wafer, the method further includes: calibrating the detection error of the sensor; the calibration of the detection error of the sensor includes: using the sensor to detect the position of a calibration point on the wafer to obtain the coordinates to be calibrated of the calibration point; using a calibration tool to detect the position of the calibration point to obtain the actual coordinates of the calibration point; calculating the coordinate relationship between the coordinates to be calibrated and the actual coordinates of the calibration point to obtain the position error value of the calibration point; and compensating for the detection error based on the position error value. Its beneficial effect is that it helps improve the positional accuracy of the sensor scanning at a specific location.

[0025] Optionally, before compensating for the detection error based on the position error value, the method further includes: establishing a linear relationship between the coordinates to be calibrated of the calibration point and the position error value of the calibration point, wherein the number of calibration points is at least two, and the calibration points are arranged at intervals; and obtaining the position error value of the intermediate point between the calibration points based on the linear relationship. The beneficial effect is that it helps improve the positional accuracy of points along the path between specific locations scanned by the sensor.

[0026] Optionally, the calibration point is the center of the wafer. Attached Figure Description

[0027] Figure 1 This is a flowchart of the wafer offset detection method in an embodiment of the present invention;

[0028] Figure 2 This is a flowchart illustrating the process of obtaining the first edge position of the scanning point scanned by the sensor to the edge of the wafer in an embodiment of the present invention;

[0029] Figure 3 This is a flowchart illustrating how the offset center position is obtained by using the second edge position and the wafer radius in an embodiment of the present invention.

[0030] Figure 4 This is a schematic diagram of the first edge position, the second edge position, and the first distance in an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram illustrating the determination of the offset center position through the second edge position in an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram illustrating the determination of the offset center position from two undetermined center positions in an embodiment of the present invention.

[0033] Figure 7 This is a schematic diagram illustrating the acquisition of the first edge position in an embodiment of the present invention;

[0034] Figure 8 This is a schematic diagram illustrating the calibration of the sensor's detection error in an embodiment of the present invention.

[0035] Figure label:

[0036] 1. Calibration point; 2. Path between calibration points. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0038] To address the problems existing in the prior art, embodiments of the present invention provide a wafer offset detection method, referring to... Figure 1 and Figure 4 It includes the following steps:

[0039] S01: Set the reference center position of the wafer, where the reference center position is point o as shown in the figure;

[0040] S02: Use a robotic arm to move the wafer along the direction A shown in the figure from the first position to the second position. The second position is the position of the robotic arm when the center of the wafer is located at o' shown in the figure.

[0041] S03: Obtain the first edge position of the scanning point scanned by the sensor to the edge of the wafer. The first edge position is point a in the figure. When the sensor scans to the scanning point, it generates a first scanning signal.

[0042] S04: Obtain the first distance between the position of the robot arm and the second position when the first scanning signal is generated, the first distance is shown in Figure l1;

[0043] S05: Obtain the second edge position of the scanning point when the robotic arm is in the second position by using the first edge position and the first distance. The second edge position is point b in the figure.

[0044] S06: Obtain the offset center position when the wafer is offset by using the second edge position and the radius r of the wafer;

[0045] S07: The offset of the wafer is obtained by the positional relationship between the offset center position and the reference center position.

[0046] In some embodiments of the present invention, steps S03, S04, S05, S06 or S07 may be executed during the execution of step S02.

[0047] In some specific embodiments of the present invention, reference is made to Figure 4 The reference center position is point o in the figure. The reference center position can be set according to the specific structure of the robot. The reference center position can be the center point of the robot's handling fingers under ideal process conditions.

[0048] In some specific embodiments of the present invention, reference is made to Figure 4 After the wafer is placed on the robotic arm, there is a certain offset. The center of the offset is point o' in the figure, and the offset is the offset of point o' relative to point o in the figure.

[0049] In some specific embodiments of the present invention, reference is made to Figure 5 By setting two sensors, two first edge positions, namely points a1 and a2 in the figure, are obtained, and then two second edge positions, namely points b1 and b2 in the figure, are obtained. The offset center position is determined by points b1, b2 and radius r in the figure.

[0050] In some specific embodiments of the present invention, the second edge position is obtained by taking the first edge position as the starting point, the direction of movement of the wafer as the direction, and the first distance as the spacing.

[0051] In some embodiments of the present invention, the wafer is approximately circular, the edge of the wafer is a circle, and the second edge position is a point on the circle.

[0052] In some embodiments of the present invention, at least three sensors are used to obtain at least three second edge positions to determine the position of the offset center when the wafer is offset.

[0053] In some specific embodiments of the present invention, the robotic arm is driven by a servo system, the servo system including a servo motor and a servo encoder connected to the robotic arm, and the sensor connected to the probe port of the servo encoder is used by the servo system to obtain the first scanning signal.

[0054] In some specific embodiments of the present invention, reference is made to Figure 4 and Figure 5 The robotic arm moving the wafer from a first position to a second position along the path includes: the robotic arm moving the wafer from the retracted position to the extended position of the robotic arm, i.e., moving along direction A in the figure; or the robotic arm moving the wafer from the extended position to the retracted position of the robotic arm, i.e., moving in the opposite direction of direction A in the figure.

[0055] In other specific embodiments of the present invention, the first position and the second position can be any segment of the path of the robot arm, and the edge of the wafer must be detectable by the sensor when the wafer moves on the path.

[0056] In some specific embodiments of the present invention, a stop signal is generated when the robotic arm is in the second position, and the servo encoder obtains the number of rotations of the servo motor during the time period between the two signals based on the first scan signal and the stop signal to obtain the first distance.

[0057] In some embodiments of the present invention, the stop signal is not limited to using various types of displacement sensors to generate the stop signal when the robot is in the second position.

[0058] In some specific embodiments of the present invention, the sensor is a through-beam sensor, the line connecting the transmitting end and the receiving end of the through-beam sensor is perpendicular to the plane where the wafer is located, and the position of the through-beam sensor is the same as the position of the first edge when viewed perpendicular to the wafer.

[0059] In some specific embodiments of the present invention, the first scanning signal may be a signal generated when the sensor is blocked by the wafer during the process of the wafer moving from the retracted position to the extended position, or a signal generated when the sensor changes from being blocked by the wafer to being unblocked.

[0060] In some other embodiments of the present invention, the first scanning signal may be a signal generated when the sensor is blocked by the wafer during the process of the wafer moving from the extended position to the retracted position, or a signal generated when the sensor changes from being blocked by the wafer to being unblocked.

[0061] In some embodiments of the present invention, the first edge position, the first distance, the second edge position, the reference center position, and the offset center position are all located within the plane of the wafer.

[0062] In some specific embodiments of the present invention, reference is made to Figure 4 and Figure 5 The first position is the extended position of the robotic arm, and the second position is the retracted position of the robotic arm, that is, the robotic arm retracts along direction A in the figure. The first scanning signal is the signal output when the wafer changes from blocking the sensor to not blocking it.

[0063] In some specific embodiments of the present invention, reference is made to Figure 2 and Figure 7 The step S03, which involves obtaining the first edge position of the scanning point detected by the sensor at the edge of the wafer, includes:

[0064] S031: Place the wafer on the robotic arm so that the center of the wafer is located at the reference center position, i.e., point o in the figure;

[0065] S032: Use the robotic arm to move the wafer to obtain the second center position when the sensor is blocked by the edge of the wafer, i.e., point o1 in the figure;

[0066] S033: Use the robotic arm to drive the wafer to continue moving, and obtain the third center position when the wafer no longer blocks the sensor, i.e. point o2 in the figure;

[0067] S034: The first edge position, i.e. point a in the figure, is obtained by the radius of the wafer, the second center position, and the third center position.

[0068] In some specific embodiments of the present invention, reference is made to Figure 2 and Figure 7In step S032, the robotic arm moves the wafer from the reference center position, i.e., along direction B in the figure from the retracted position to the extended position. When the sensor is obstructed by the edge of the wafer, the sensor generates a second scanning signal. The servo system obtains the distance between the robotic arm at the retracted position and the position where the second scanning signal was generated as a second distance, i.e., in Figure 12. The robotic arm continues to move the wafer. When the sensor is no longer obstructed by the edge of the wafer, the sensor generates a third scanning signal. The servo system... The service system obtains the distance between the robotic arm at the retracted position and the position where the third scan signal is generated as the third distance, as shown in Figure 13; the second center position, i.e., point o1 in the figure, and the third center position, i.e., point o2 in the figure, can be obtained based on the movement direction of the robotic arm, the reference center position, the second distance, and the third distance; based on the second center position, the third center position, and the radius of the wafer, the first edge position of the scan from the sensor to the edge of the wafer, i.e., point a in the figure, can be obtained by means of a general equation of a circle or the Pythagorean theorem, not limited to the method of the general equation of a circle or the Pythagorean theorem.

[0069] It should be noted that the sensor is a through-beam sensor. Since the line connecting the transmitter and receiver of the through-beam sensor is perpendicular to the plane of the wafer, the position of the through-beam sensor is the same as the position of the first edge when viewed from a perspective perpendicular to the wafer. That is, the position of the first edge is determined by the position of the through-beam sensor.

[0070] In some specific embodiments, the sensor is an AWC sensor on a semiconductor device robotic arm.

[0071] In some embodiments of the present invention, reference is made to Figure 3 and Figure 6 The step S06, which involves obtaining the offset center position of the wafer during offset by using the second edge position and the radius of the wafer, includes:

[0072] S061: Use the two sensors to obtain the two second edge positions, namely point b1 and point b2 in the figure;

[0073] S062: Two center positions to be determined are obtained by using the two second edge positions and the wafer radius, namely point o' and point o” in the figure;

[0074] S063: Calculate the distances between the two centers to be determined and the reference center, and take the one with the closer distance as the offset center position.

[0075] In some specific embodiments of the present invention, reference is made to Figure 6By setting two sensors, two second edge positions are obtained. The wafer is approximately circular, and the edge of the wafer is a circle. The two second edge positions are points on two circles. Combined with the radius of the wafer, two center positions to be determined can be obtained, namely point o' and point o” in the figure. The offset center position is the one of the two center positions to be determined that is closer to the reference center position. Finally, point o' is determined as the offset center position.

[0076] In some embodiments of the present invention, the step of using a robotic arm to move the wafer includes: the robotic arm moving the wafer at a first speed; when the distance between the edge of the wafer and the location of the sensor is less than a threshold, the robotic arm moving the wafer at a second speed, wherein the second speed is less than the first speed.

[0077] In some embodiments of the present invention, the threshold ranges from 1 mm to 5 cm.

[0078] In some embodiments of the present invention, reference is made to Figure 4 , Figure 5 and Figure 6 The sensors are respectively set on both sides of the moving path of the center of the wafer, that is, when the center of the wafer moves along direction C in the figure, the two sensors are set on both sides of the moving path of the center of the wafer.

[0079] In some embodiments of the present invention, the sensor is connected to a servo system that drives the movement of the robotic arm, and the servo system is used to obtain the movement distance of the robotic arm after the sensor generates a signal.

[0080] In some embodiments of the present invention, after obtaining the offset of the wafer, the position of the robot is adjusted by a motor so that the center of the wafer is located at the reference center position.

[0081] In some embodiments of the present invention, before obtaining the first edge position of the scanning point scanned by the sensor to the edge of the wafer, the method further includes: obtaining the delay of the sensor and the moving speed of the robot; and compensating the first edge position and the second edge position according to the delay of the sensor and the moving speed of the robot.

[0082] In some embodiments of the present invention, obtaining the delay of the sensor includes: using a robotic arm to move the wafer at a third speed and a fourth speed respectively; obtaining the third edge position and the fourth edge position of the scanning point scanned by the sensor to the edge of the wafer respectively; and obtaining the delay of the sensor based on the distance between the fourth edge position and the third edge position and the speed difference between the fourth speed and the third speed.

[0083] In some specific embodiments, the speed difference between the fourth speed and the third speed ranges from 1 mm / s to 600 mm / s.

[0084] Furthermore, the speed difference between the fourth speed and the third speed can be in the range of 100, 200, 300, 400, 500 or 600 mm / s.

[0085] Specifically, the third speed can be 1 mm / s, and the fourth speed can be 600 mm / s.

[0086] In some specific embodiments, the distance between the third edge position and the fourth edge position is obtained by the difference in the rotation distance when the servo system receives the signals from the sensor respectively.

[0087] In some specific embodiments, the delay td of the sensor is (S2-S1) / (V2-V1), where S1 is the distance the wafer moves when the wafer movement servo system probe port receives the sensor at the third speed, S2 is the distance the wafer moves when the wafer movement servo system probe port receives the sensor at the fourth speed, (S2-S1) is the distance between the fourth edge position and the third edge position, V1 is the third speed, V2 is the fourth speed, and (V2-V1) is the speed difference between the fourth speed and the third speed.

[0088] In some embodiments of the present invention, before obtaining the first edge position of the scanning point scanned by the sensor to the edge of the wafer, the method further includes: calibrating the detection error of the sensor; the calibration of the detection error of the sensor includes: using the sensor to detect the position of a calibration point on the wafer to obtain the coordinates to be calibrated of the calibration point; using a calibration tool to detect the position of the calibration point to obtain the actual coordinates of the calibration point; calculating the coordinate relationship between the coordinates to be calibrated and the actual coordinates of the calibration point to obtain the position error value of the calibration point; and compensating for the detection error based on the position error value.

[0089] In some embodiments of the present invention, before compensating for the detection error based on the position error value, the method further includes: establishing a linear relationship between the coordinates to be calibrated of the calibration point and the position error value of the calibration point, wherein the number of calibration points is at least two, and the calibration points are arranged at intervals; and obtaining the position error value of the intermediate point between the calibration points based on the linear relationship.

[0090] In some specific embodiments, reference is made to Figure 8The number of calibration points 1 can be 25, and the 25 calibration points 1 form a rectangular array to realize the error position calibration of 25 points within the rectangular area.

[0091] In some specific embodiments, reference is made to Figure 8 Select any two adjacent calibration points 1 from the 25 calibration points 1, and establish the linear relationship between the coordinates to be calibrated of the two adjacent calibration points 1 and the position error value of the calibration points, so as to realize the error position calibration at any position on the path 2 between the two adjacent calibration points.

[0092] In some specific embodiments, the calibration point can be the center of the wafer. By setting the wafer at different positions, the calibration point is used as the center of the wafer at different positions to detect the error.

[0093] In some specific embodiments of the present invention, the calibration tool can be various high-precision distance detection tools, which establish a coordinate system with a specified point as the origin and detect the actual coordinates of the calibration point.

[0094] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A method for detecting wafer offset, characterized in that, The process includes the following steps: setting a reference center position for the wafer; using a robotic arm to move the wafer from a first position to a second position along a path; acquiring the sensor delay and the robotic arm's movement speed; the sensors are respectively positioned on both sides of the movement path of the wafer's center. The system acquires a first edge position of a scanning point detected by a sensor at the edge of the wafer, and generates a first scanning signal when the sensor detects the scanning point. The first edge position is compensated based on the sensor's delay and the robot's moving speed. A first distance is obtained between the robot's position and a second position when the first scanning signal is generated. The second edge position of the scanning point when the robot is in the second position is obtained by using the compensated first edge position and the first distance; the second edge position is compensated according to the sensor delay and the robot's moving speed; The offset center position of the wafer during offset is obtained by using the compensated second edge position and the radius of the wafer, including: Two second edge positions are obtained using the two sensors; two center positions to be determined are obtained using the two second edge positions and the wafer radius; the distances between the two center positions to be determined and the reference center position are calculated, and the one with the closer distance is taken as the offset center position; the offset of the wafer is obtained using the positional relationship between the offset center position and the reference center position.

2. The wafer offset detection method according to claim 1, characterized in that, The first position is the extended position of the robotic arm, the second position is the retracted position of the robotic arm, and the first scanning signal is the signal output when the wafer changes from blocking the sensor to not blocking it.

3. The wafer offset detection method according to claim 1, characterized in that, The step of obtaining the first edge position of the scanning point scanned by the sensor to the edge of the wafer includes: placing the wafer on a robotic arm so that the center of the wafer is located at the reference center position; using the robotic arm to move the wafer to obtain a second center position when the sensor is obscured by the edge of the wafer; using the robotic arm to continue moving the wafer to obtain a third center position when the wafer no longer obscures the sensor; and obtaining the first edge position through the radius of the wafer, the second center position, and the third center position.

4. The wafer offset detection method according to any one of claims 1 to 3, characterized in that, The method of using a robotic arm to move the wafer includes: the robotic arm moving the wafer at a first speed; when the distance between the edge of the wafer and the location of the sensor is less than a threshold, the robotic arm moving the wafer at a second speed, the second speed being less than the first speed.

5. The wafer offset detection method according to claim 4, characterized in that, The sensor is a through-beam sensor, and the through-beam sensor is positioned perpendicular to the wafer.

6. The wafer offset detection method according to claim 4, characterized in that, The sensor is connected to a servo system that drives the movement of the robotic arm, and the servo system is used to obtain the distance the robotic arm moves after the sensor generates a signal.

7. The wafer offset detection method according to claim 1, characterized in that, The method of obtaining the delay of the sensor includes: using a robotic arm to move the wafer at a third speed and a fourth speed respectively; obtaining the third edge position and the fourth edge position of the scanning point scanned by the sensor to the edge of the wafer respectively; and obtaining the delay of the sensor based on the distance between the fourth edge position and the third edge position and the speed difference between the fourth speed and the third speed.

8. The wafer offset detection method according to claim 6, characterized in that, Before acquiring the first edge position of the scanning point scanned by the sensor to the edge of the wafer, the method further includes: acquiring the delay of the probe port of the servo system and the moving speed of the robot, and compensating the first edge position and the second edge position according to the delay of the probe port and the moving speed of the robot.

9. The wafer offset detection method according to claim 6, characterized in that, Before acquiring the first edge position of the scanning point scanned by the sensor to the edge of the wafer, the method further includes: acquiring the encoder delay of the servo system and the moving speed of the robot, and compensating the first edge position and the second edge position according to the encoder delay and the moving speed of the robot.

10. The wafer offset detection method according to claim 1, characterized in that, Before obtaining the first edge position of the scanning point scanned by the sensor to the edge of the wafer, the method further includes: calibrating the detection error of the sensor; the calibration of the detection error of the sensor includes: using the sensor to detect the position of the calibration point on the wafer to obtain the coordinates to be calibrated of the calibration point; using a calibration tool to detect the position of the calibration point to obtain the actual coordinates of the calibration point; calculating the coordinate relationship between the coordinates to be calibrated and the actual coordinates of the calibration point to obtain the position error value of the calibration point; and compensating for the detection error based on the position error value.

11. The wafer offset detection method according to claim 10, characterized in that, Before compensating the detection error based on the position error value, the method further includes: establishing a linear relationship between the coordinates to be calibrated of the calibration point and the position error value of the calibration point, wherein the number of calibration points is at least 2, and the calibration points are arranged at intervals; and obtaining the position error value of the intermediate point between the calibration points based on the linear relationship.

12. The wafer offset detection method according to claim 10, characterized in that, The calibration point is the center of the wafer.

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