Wafer back cutting visual positioning system and positioning method

Abstract

The application discloses a wafer back cutting visual positioning system and a positioning method. The system comprises a moving platform, a rotating positioning mechanism, a prism assembly, an image taking mechanism and a laser generator. The rotating positioning mechanism and the prism assembly are arranged on the moving platform, and the prism assembly is arranged in a peripheral direction of the rotating positioning mechanism. The prism assembly comprises a prism module, and the prism module moves in X, Y and Z directions. The rotating positioning mechanism comprises a rotating motor and a ceramic suction cup. The output end of the rotating motor is provided with the ceramic suction cup, and the ceramic suction cup is uniformly provided with visual avoidance holes in a peripheral direction. The image taking mechanism comprises a high-power camera and a back-to-position camera. The prism module is arranged opposite to the visual avoidance holes and the back-to-position camera at two ends respectively. The high-power camera is used for shooting a wafer back image, and the back-to-position camera shoots a wafer front image through the prism module and obtains the center coordinates of the image. The application positions a cutting path to be cut on the wafer back.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor wafer manufacturing technology, and specifically relates to a wafer back-cut visual positioning system and positioning method. Background Technology

[0002] In semiconductor chip manufacturing, wafers need to be grouted. To improve processing accuracy, laser grooving is generally used. However, some wafers have special plating on the front side that prevents laser grooving and can only be grooved using water jet cutting. Water jet-processed wafers have wider surface cuts, longer grooving times, and lower processing accuracy. If laser grooving is used on the back side of the wafer, the lack of a pattern for positioning on the back side prevents the laser from grooving at the precise location.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a wafer back-cut visual positioning system and positioning method, thereby overcoming the defects in the prior art.

[0005] To achieve the above objectives, the present invention provides a wafer back-cutting visual positioning system, comprising a moving platform, a rotating positioning mechanism, a prism assembly, an image acquisition mechanism, and a laser generator; the image acquisition mechanism and the laser generator are mounted on a support; the moving platform is provided with the rotating positioning mechanism and the prism assembly, with the prism assembly arranged circumferentially around the rotating positioning mechanism; the moving platform moves in the X-axis and Y-axis directions; the prism assembly includes a prism module, which moves in the X-axis, Y-axis, and Z-axis directions; the rotating positioning mechanism includes a rotary motor and a ceramic chuck, the rotary motor being disposed within the moving platform, and the rotary motor... The machine output end is equipped with a ceramic suction cup, which is connected to an external vacuum device. The ceramic suction cup has visual clearance holes evenly arranged in the circumferential direction. The imaging mechanism includes a high-magnification camera and a back-facing camera. The back-facing camera is located outside the high-magnification camera. The two ends of the prism module are respectively positioned opposite to the visual clearance holes and the back-facing camera. The high-magnification camera is used to capture images of the back side of the wafer, and the back-facing camera captures images of the front side of the wafer through the prism module and obtains the center coordinates of the image. The coordinates of the high-magnification camera at the same position on the back side of the wafer are determined by the center coordinates of the front side image and the position of the back-facing camera, and the slotting position on the back side of the wafer is located.

[0006] Preferably, in the technical solution, the ceramic suction cup is provided with four visual avoidance holes, and the adjacent visual avoidance holes are spaced 90° apart. The outer sides of the three visual avoidance holes are respectively provided with corresponding prism components. The three prism components are respectively denoted as points A, B, and C. The line connecting points A and B is parallel to the Y-axis, and the line connecting point C and the center of the ceramic suction cup is parallel to the X-axis.

[0007] Preferably, in the technical solution, the prism assembly includes a prism module, an X-axis fine-tuning slide, a Y-axis fine-tuning slide, and a Z-axis fine-tuning slide. The X-axis fine-tuning slide is mounted on a moving platform outside the corresponding visual avoidance hole. A Y-axis fine-tuning slide is mounted on the X-axis fine-tuning slide, a Z-axis fine-tuning slide is mounted on the Y-axis fine-tuning slide, and the prism module is mounted on the Z-axis fine-tuning slide. The prism module includes a prism base, a right-angle reflecting prism, and a Daowei prism. The prism base is mounted on the Z-axis fine-tuning slide, and the top of the prism base has an entrance port and an exit port. The Daowei prism is inverted and placed inside the prism holder. Right-angle reflecting prisms are symmetrically arranged on both sides of the Daowei prism. Corresponding right-angle reflecting prisms are arranged below the entrance and exit. The entrance-right-angle reflecting prism-Daowei prism-right-angle reflecting prism-exit form a light propagation channel. The entrance is located below the visual avoidance hole, and the exit is located below the back-facing camera. The X-axis, Y-axis, and Z-axis coordinates of the entrance and exit are finely adjusted by the X-axis, Y-axis, and Z-axis fine-tuning slides, respectively.

[0008] Preferably, in the technical solution, a laser rangefinder is mounted on the bracket, and the laser rangefinder is located on one side of the laser generator.

[0009] A wafer back-cut visual positioning method, the steps of which are: (1) calibrating the prism assembly; the calibration steps are: (a1) placing the half-wafer with a right-angled edge bare silicon wafer with the back side facing up on the ceramic chuck, moving the platform to move the prism module to the bottom of the back-alignment camera, adjusting the position of the prism module in the Z-axis direction so that the back-alignment camera can see the right-angle position of the bare silicon wafer through the prism module at the visual avoidance hole position;

[0010] (a2) The right-angled edge of the bare silicon wafer forms a wafer straight line on two opposite visual clearance holes. A high-magnification camera takes a picture of the wafer straight line and calculates the angle between the wafer straight line and the horizontal line passing through the center of the ceramic chuck. The rotary motor drives the ceramic chuck to rotate according to the angle to straighten the wafer straight line.

[0011] (a3) The moving platform moves the prism modules corresponding to both ends of the wafer straight line to the bottom of the back-alignment camera. The back-alignment camera views the wafer straight line at the corresponding position through the prism module. The position of the prism module in the X-axis and Y-axis directions is adjusted so that the image center of the back-alignment camera is always on the wafer straight line.

[0012] (a4) Use the method in (a3) ​​to calibrate the positions of the remaining prism modules in the X and Y axes;

[0013] (2) Calibrate the high-magnification camera position coordinates and the back-facing camera position coordinates of the visual avoidance hole position; the calibration method is: (b1) Place the half-wafer with right-angled edge bare silicon wafer with the back side facing up on the ceramic chuck, with the right-angled position located at the center of the corresponding visual avoidance hole;

[0014] (b2) The moving platform moves the bare silicon wafer. When the right-angle position moves to the center of the high-magnification camera image, it stops. The distance the moving platform moves along the X and Y axes at this time is recorded as the high-magnification camera position coordinates calibrated at the visual clearance hole position.

[0015] (b3) The moving platform moves the prism module to the bottom of the back-facing camera, switches to the back-facing camera, and the back-facing camera views the right angle position through the prism module. The distance the moving platform moves along the X and Y axes at this time is recorded as the coordinates of the back-facing camera position calibrated at the visual clearance hole position.

[0016] (3) Place the wafer to be processed with its back side facing up on the ceramic chuck. Move the prism assembly in the X-axis and Y-axis directions. When the outlet moves to the bottom of the back-alignment camera and the back-alignment camera sees the corresponding visual avoidance hole through the prism module, record the distance the moving platform moves in the X-axis and Y-axis directions as the center coordinates of the back-alignment camera image of the visual avoidance hole. Calculate the center coordinates of the high-magnification camera image of the visual avoidance hole based on the high-magnification camera position coordinates and the back-alignment camera position coordinates calibrated in step (2).

[0017] (4) Based on the center coordinates of the high-magnification camera image of the visual avoidance hole calculated in step (3), calculate the angle between the line connecting the center coordinates of the high-magnification camera image of the visual avoidance hole and the Y-axis. The rotary motor drives the wafer to rotate according to the angle until the angle is within the error range, and the cutting path to be cut on the back of the wafer is straightened.

[0018] (5) The laser generator performs laser cutting on the dicing track on the back of the wafer.

[0019] Preferably, in the technical solution, in step (2), the high-magnification camera position coordinates for calibrating the visual avoidance hole position are (X... hi ,Y hi The coordinates of the back-facing camera position, as determined by the visual obstacle avoidance hole position, are (X... bi ,Y bi ), i = (A, B, C).

[0020] Preferably, in the technical solution, in step (3), the coordinates of the center of the back-facing camera image of the visual avoidance hole are (X... bi1 ,Ybi1 The center coordinates of the high-magnification camera image of the visual avoidance hole are (X... hi1 ,Y hi1 ).

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] By cooperating with a mobile platform, a rotating positioning mechanism, a prism assembly, and an image acquisition mechanism, the coordinate position of a high-magnification camera on the back of the wafer is calculated based on the measured image coordinates of the front side of the wafer and the calibrated camera coordinates. This allows for the positioning of the cutting path to be cut on the back of the wafer, solving the problem that laser cutting is not possible on the front side of the wafer and that back cutting is not feasible due to the inability to position the back of the wafer. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the wafer back-cut visual positioning system of the present invention;

[0024] Figure 2 This is a top view of the wafer back-cut visual positioning system of the present invention;

[0025] Figure 3 for Figure 2 Sectional view along axis AA;

[0026] Figure 4 This is a schematic diagram of the ceramic suction cup structure of the present invention;

[0027] Figure 5 This is a schematic diagram of the prism assembly structure of the present invention;

[0028] Figure 6 This is a left view of the prism assembly of the present invention;

[0029] Figure 7 for Figure 6 BB-direction sectional view;

[0030] Figure 8 This is a schematic diagram of the wafer back-cut visual positioning method of the present invention;

[0031] Figure 9 This is a schematic diagram of the prism assembly calibration process of the present invention;

[0032] Figure 10 This is a schematic diagram illustrating the calibration process for the high-magnification camera position coordinates and the back-to-back camera position coordinates of the present invention. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0034] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0035] like Figure 1-3 As shown, a wafer back-cut visual positioning system includes a moving platform 1, a rotating positioning mechanism 2, a prism assembly 3, an image acquisition mechanism 4, a laser generator 5, and a laser rangefinder 6. The image acquisition mechanism 4, the laser generator 5, and the laser rangefinder 6 are mounted on a support 7, with the laser rangefinder 6 located to one side of the laser generator 5. The moving platform 1 is equipped with the rotating positioning mechanism 2 and the prism assembly 3. The moving platform 1 moves along the X and Y axes via a sliding mechanism. The rotating positioning mechanism 2 includes a rotary motor 20 and a ceramic suction cup 21. The rotary motor 20 is located inside the moving platform 1, and the ceramic suction cup 21 is located at the output end of the rotary motor 20 and is connected to an external vacuum device. The image acquisition mechanism 4 includes a high-magnification camera 40, a back-alignment camera 41, and a light source 42 corresponding to the camera. The back-alignment camera 41 is located outside the high-magnification camera 40. The high-magnification camera 40 is used to capture images of the back side of the wafer, and the back-alignment camera 41 captures images of the front side of the wafer through the prism assembly 3 and obtains the center coordinates of the image.

[0036] like Figure 4 As shown, the ceramic suction cup 21 is provided with four visual avoidance holes 22, and the adjacent visual avoidance holes 22 are spaced 90° apart. The outer sides of three visual avoidance holes 22 are respectively provided with corresponding prism components 3. The three prism components 3 are denoted as points A, B and C, respectively. The line connecting points A and B is parallel to the Y-axis, and the line connecting point C and the center of the ceramic suction cup 21 is parallel to the X-axis.

[0037] like Figure 5-7As shown, the prism assembly 3 includes a prism module 30, an X-axis fine-tuning slide 31, a Y-axis fine-tuning slide 32, and a Z-axis fine-tuning slide 33. The X-axis fine-tuning slide 31 is mounted on the moving platform 1 outside the corresponding visual avoidance hole 22. The Y-axis fine-tuning slide 32 is mounted on the X-axis fine-tuning slide 31, the Z-axis fine-tuning slide 33 is mounted on the Y-axis fine-tuning slide 32, and the prism module 30 is mounted on the Z-axis fine-tuning slide 33. The prism module 30 includes a prism base 34, a right-angle reflecting prism 35, and a Daowei prism 36. The prism base 34 is mounted on the Z-axis fine-tuning slide 33, and the top of the prism base 34 has an entrance port 37 and an exit port 38. The Daowei prism 36 is inverted and placed inside the prism base 34. Right-angle reflecting prisms 35 are symmetrically arranged on both sides of the Daowei prism 36. Corresponding right-angle reflecting prisms 35 are respectively arranged below the entrance port 37 and the exit port 38. The light propagation channel is formed by entrance port 37-right-angle reflecting prism 35-Daowei prism 36-right-angle reflecting prism 35-exit port 38. Entrance port 37 is located below the visual avoidance hole 22, and exit port 38 is located below the back-facing camera 41. The X-axis, Y-axis, and Z-axis coordinates of entrance port 37 and exit port 38 are finely adjusted by the X-axis fine-tuning slide 31, Y-axis fine-tuning slide 32, and Z-axis fine-tuning slide 33, respectively.

[0038] The wafer back-cutting visual positioning system also includes a controller, which is connected to a high-magnification camera 40, a back-alignment camera 41, a laser rangefinder 6, a rotary motor 20, a servo motor of the sliding mechanism of the moving platform 1, and a laser generator 5. The controller receives visual images collected by the high-magnification camera 40 and the back-alignment camera 41, and wafer thickness information collected by the laser rangefinder 6. It controls the rotary motor 20 to rotate, controls the servo motor to drive the moving platform 1 to move in the X and Y axis directions, and controls the laser generator 5 to output laser for cutting.

[0039] like Figure 8 As shown, a wafer back-cut visual positioning method includes the following steps: (1) calibrating the prism assembly; as shown Figure 9As shown, the calibration steps are as follows: (a1) Place the half-wafer with a right-angled edge on the ceramic chuck with the back side facing up. The servo motor controls the moving platform to move the outlet of the A-point prism module to below the back-facing camera. Adjust the Z-axis fine-tuning slide by turning the knob to adjust the position of the outlet of the A-point prism module in the Z-axis direction so that the back-facing camera can see the right-angle position of the bare silicon wafer through the outlet of the A-point prism module at the A-point visual clearance hole position. Then, the servo motor controls the moving platform to move the outlet of the B-point prism module to below the back-facing camera. Repeat the above operation so that the back-facing camera can see the right-angle position of the bare silicon wafer through the outlet of the B-point prism module at the B-point visual clearance hole position. Then, the servo motor controls the moving platform to move the outlet of the C-point prism module to below the back-facing camera. Repeat the above operation so that the back-facing camera can see the right-angle position of the bare silicon wafer through the outlet of the C-point prism module at the C-point visual clearance hole position.

[0040] (a2) The right-angled edge of the bare silicon wafer forms a wafer straight line on the visual clearance holes at points A and B. A high-magnification camera takes pictures of the wafer straight line. The angle between the wafer straight line and the horizontal line passing through the center of the ceramic chuck is calculated based on the captured image. The rotary motor drives the ceramic chuck to rotate according to the angle, straightening the wafer straight line so that the wafer straight line is parallel to the horizontal line passing through the center of the ceramic chuck.

[0041] (a3) The moving platform moves the outlet of the A-point prism module to below the back-alignment camera. The back-alignment camera views the wafer straight line at the corresponding position through the outlet of the A-point prism module. Adjust the X-axis and Y-axis fine-tuning slides with knobs to adjust the position of the inlet and outlet of the A-point prism module in the X-axis and Y-axis directions, so that the image center of the back-alignment camera is always on the wafer straight line. The moving platform moves the outlet of the B-point prism module to below the back-alignment camera, and the above operation is repeated.

[0042] (a4) Rotate the bare silicon wafer by 90°. The right-angled edge of the bare silicon wafer forms a wafer straight line on the visual clearance hole at point C. The high-magnification camera takes a picture of the wafer straight line. Calculate the angle between the wafer straight line and the horizontal line passing through the center of the ceramic chuck based on the captured image. The rotary motor drives the ceramic chuck to rotate according to the angle, straightening the wafer straight line so that it is parallel to the horizontal line passing through the center of the ceramic chuck. The moving platform moves the outlet of the C-point prism module to below the back-facing camera. The back-facing camera views the wafer straight line at the corresponding position through the outlet of the C-point prism module. Adjust the X-axis and Y-axis fine-tuning slides with the knobs to adjust the position of the inlet and outlet of the C-point prism module in the X-axis and Y-axis directions so that the image center of the back-facing camera is always on the wafer straight line.

[0043] (2) Calibrate the high-magnification camera position coordinates and the back-facing camera position coordinates of the visual avoidance hole positions at points A, B, and C; such as Figure 10As shown, the calibration method is as follows: (b1) Place the half-wafer with right-angled edge bare silicon wafer with the back side facing up on the ceramic chuck, with the right-angle position located at the center of the visual clearance hole at points A and B;

[0044] (b2) The moving platform moves the bare silicon wafer. When the right-angle position at the center of the visual avoidance hole at point A moves to the center of the high-magnification camera image, it stops. The distance the moving platform moves along the X and Y axes at this time is recorded as the high-magnification camera position coordinates (X, Y) for calibrating the position of the visual avoidance hole at point A. hA Y hA );

[0045] (b3) The moving platform moves the outlet of the A-point prism module to below the back-facing camera, switches to the back-facing camera, and the back-facing camera views the right-angle position at the center of the visual avoidance hole at point A through the outlet of the A-point prism module. The distance the moving platform moves along the X and Y axes at this time is recorded as the position coordinates of the back-facing camera for calibrating the position of the visual avoidance hole at point A (X... bA Y bA );

[0046] (b4) Repeat steps (b2)-(b3) to record the high-magnification camera position coordinates (X) of the visual avoidance hole location at point B. hB Y hB ) and the position coordinates of the back-facing camera (X) bB Y bB );

[0047] (b5) Rotate the bare silicon wafer by 90° and repeat the operations (b2)-(b3) to record the high-magnification camera position coordinates (X) of the visual avoidance hole position at point C. hC Y hC ) and the position coordinates of the back-facing camera (X) bC Y bC );

[0048] (3) Place the wafer to be processed with its back side facing up on the ceramic chuck. Move the moving platform to move the outlet of the prism module at point A in the X and Y directions. When the outlet moves to below the back-alignment camera, and the back-alignment camera sees the visual avoidance hole at point A through the prism module, record the distance the moving platform moves in the X and Y directions at this time as the coordinates of the back-alignment camera image center of the visual avoidance hole at point A (X... bA1 ,Y bA1 According to the high-magnification camera position coordinates (X) of the visual avoidance hole at point A, as determined in step (2). hA Y hA ) and the position coordinates of the back-facing camera (X) bA Y bA ), calculate the center coordinates (X, X) of the high-magnification camera image of the visual obstacle avoidance hole at point A. hA1 ,YhA1 ):

[0049] (X) hA1 ,Y hA1 ) = (X hA -X bA +X bA1 , Y hA +Y bA -Y bA1 );

[0050] Similarly, the coordinates (X, X) of the center of the high-magnification camera image of the visual obstacle avoidance aperture at point B are calculated using the method described above. hB1 ,Y hB1 ):

[0051] (X) hB1 ,Y hB1 ) = (X hB -X bB +X bB1 , Y hB +Y bB -Y bB1 );

[0052] The coordinates of the high-magnification camera image center of point C (X) for visual obstacle avoidance hole hC1 ,Y hC1 ):

[0053] (X) hC1 ,Y hC1 ) = (X hC +X bC -X bC1 , Y hC -Y bC +Y bC1 );

[0054] (4) Based on the high-magnification camera image center coordinates of the visual avoidance holes at points A and B calculated in step (3), calculate the angle θ between the line AB connecting the high-magnification camera image center coordinates of the visual avoidance holes at points A and B and the Y-axis. The rotary motor drives the wafer to rotate according to the angle θ until the angle θ is within the error range, and the Y-axis cutting path AB to be cut on the back of the wafer is straightened.

[0055] Verify whether the Y-axis cleavage AB is straight: Take the midpoint O0 of AB as the intersection of the Y-axis cleavage and the X-axis cleavage at the center of the wafer. Based on the size of the wafer die, calculate the intersection O1 of the Y-axis cleavage and the X-axis cleavage near the visual clearance hole at point C along the line connecting O0 and point C. Move the platform to move the outlet of the prism module at point C to the back-facing camera below the back-facing camera to check whether the front of the wafer corresponds to the intersection of the Y-axis cleavage and the X-axis cleavage at position 01. If so, verify that the Y-axis cleavage AB is straight.

[0056] (5) The laser generator performs laser cutting on the cleaving track AB on the back side of the wafer. The moving platform moves accordingly in the X-axis direction according to the spacing between the cleaving tracks in the Y-axis direction. The laser generator completes the processing of the cleaving track in the Y-axis direction on the back side of the wafer.

[0057] (6) The rotary motor drives the ceramic suction cup to rotate 90°, changing the original X-axis direction of the back side to the Y-axis direction. Repeat steps (3)-(4) to straighten the Y-axis cutting path on the back side of the wafer. After verifying whether it is straight, the laser generator performs laser cutting on the Y-axis cutting path. The moving platform moves accordingly in the X-axis direction according to the spacing between the Y-axis cutting paths. The laser generator completes the Y-axis cutting path on the back side of the wafer, and all the cutting paths on the back side of the wafer are completed.

[0058] During the processing, the laser rangefinder and laser generator form a laser focus tracking and compensation mechanism, which detects the wafer thickness and laser focus position information in real time, and compensates for the laser focus to ensure the accuracy of laser cutting.

[0059] By cooperating with a mobile platform, a rotating positioning mechanism, a prism assembly, and an image acquisition mechanism, the coordinate position of a high-magnification camera on the back of the wafer is calculated based on the measured image coordinates of the front side of the wafer and the calibrated camera coordinates. This allows for the positioning of the cutting path to be cut on the back of the wafer, solving the problem that laser cutting is not possible on the front side of the wafer and that back cutting is not feasible due to the inability to position the back of the wafer.

[0060] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A positioning method for a wafer back-cut visual positioning system, the system comprising a moving platform, a rotating positioning mechanism, a prism assembly, an image acquisition mechanism, and a laser generator; the image acquisition mechanism and the laser generator are mounted on a support; the moving platform is provided with the rotating positioning mechanism and the prism assembly, and the prism assembly is arranged circumferentially around the rotating positioning mechanism; the moving platform moves in the X-axis and Y-axis directions; the prism assembly includes a prism module, which moves in the X-axis, Y-axis, and Z-axis directions; the rotating positioning mechanism includes a rotary motor and a ceramic chuck, the rotary motor is mounted inside the moving platform, the output end of the rotary motor is provided with a ceramic chuck, the ceramic chuck is connected to an external vacuum device, and the ceramic chuck has visual clearance holes evenly arranged circumferentially; the image acquisition mechanism includes a high-magnification camera and a back-alignment camera, the back-alignment camera is located outside the high-magnification camera, and the two ends of the prism module are respectively positioned opposite to the visual clearance holes and the back-alignment camera; the high-magnification camera is used to capture an image of the back side of the wafer, and the back-alignment camera captures an image of the front side of the wafer through the prism module and obtains the center coordinates of the image; The steps are as follows: (1) Calibrate the prism assembly; the calibration steps are as follows: (a1) Place the half-wafer with right-angled edge bare silicon wafer with the back side facing up on the ceramic chuck, move the platform to move the prism module to the bottom of the back-alignment camera, adjust the position of the prism module in the Z-axis direction so that the back-alignment camera can see the right-angle position of the bare silicon wafer through the prism module at the visual clearance hole position. (a2) The right-angled edge of the bare silicon wafer forms a wafer straight line on two opposite visual clearance holes. A high-magnification camera takes a picture of the wafer straight line and calculates the angle between the wafer straight line and the horizontal line passing through the center of the ceramic chuck. The rotary motor drives the ceramic chuck to rotate according to the angle to straighten the wafer straight line. (a3) The moving platform moves the prism modules corresponding to both ends of the wafer straight line to the bottom of the back-alignment camera. The back-alignment camera views the wafer straight line at the corresponding position through the prism module. The position of the prism module in the X-axis and Y-axis directions is adjusted so that the image center of the back-alignment camera is always on the wafer straight line. (a4) Use the method in (a3) ​​to calibrate the positions of the remaining prism modules in the X and Y axes; (2) Calibrate the high-magnification camera position coordinates and the back-facing camera position coordinates of the visual avoidance hole position; the calibration method is: (b1) Place the half-wafer with right-angled edge bare silicon wafer with the back side facing up on the ceramic chuck, with the right-angled position located at the center of the corresponding visual avoidance hole; (b2) The moving platform moves the bare silicon wafer. When the right-angle position moves to the center of the high-magnification camera image, it stops. The distance the moving platform moves along the X and Y axes at this time is recorded as the high-magnification camera position coordinates calibrated at the visual clearance hole position. (b3) The moving platform moves the prism module to the bottom of the back-facing camera, switches to the back-facing camera, and the back-facing camera views the right angle position through the prism module. The distance the moving platform moves along the X and Y axes at this time is recorded as the coordinates of the back-facing camera position calibrated at the visual clearance hole position. (3) Place the wafer to be processed with its back side facing up on the ceramic chuck. Move the prism assembly in the X-axis and Y-axis directions. When the outlet moves to the bottom of the back-alignment camera and the back-alignment camera sees the corresponding visual avoidance hole through the prism module, record the distance the moving platform moves in the X-axis and Y-axis directions as the center coordinates of the back-alignment camera image of the visual avoidance hole. Calculate the center coordinates of the high-magnification camera image of the visual avoidance hole based on the high-magnification camera position coordinates and the back-alignment camera position coordinates calibrated in step (2). (4) Based on the center coordinates of the high-magnification camera image of the visual avoidance hole calculated in step (3), calculate the angle between the line connecting the center coordinates of the high-magnification camera image of the visual avoidance hole and the Y-axis. The rotary motor drives the wafer to rotate according to the angle until the angle is within the error range, and the cutting path to be cut on the back of the wafer is straightened. (5) The laser generator performs laser cutting on the dicing track on the back of the wafer.

2. The positioning method of the wafer back-cut visual positioning system according to claim 1, characterized in that: The ceramic suction cup is provided with four visual avoidance holes, with a 90° interval between adjacent visual avoidance holes. A corresponding prism assembly is provided on the outer side of three of the visual avoidance holes. The three prism assemblies are denoted as points A, B, and C, respectively. The line connecting points A and B is parallel to the Y-axis, and the line connecting point C and the center of the ceramic suction cup is parallel to the X-axis.

3. The positioning method of the wafer back-cut visual positioning system according to claim 2, characterized in that: The prism assembly includes a prism module, an X-axis fine-tuning slide, a Y-axis fine-tuning slide, and a Z-axis fine-tuning slide. The X-axis fine-tuning slide is mounted on a moving platform outside the corresponding visual avoidance aperture. A Y-axis fine-tuning slide is mounted on the X-axis fine-tuning slide, a Z-axis fine-tuning slide is mounted on the Y-axis fine-tuning slide, and the prism module is mounted on the Z-axis fine-tuning slide. The prism module includes a prism mount, a right-angle reflecting prism, and a Daowei prism. The prism mount is mounted on the Z-axis fine-tuning slide, and the top of the prism mount has an entrance port and an exit port. The mirror is inverted in the inner cavity of the prism holder. Right-angle reflecting prisms are symmetrically arranged on both sides of the Daowei prism. Corresponding right-angle reflecting prisms are respectively arranged below the entrance and exit. The entrance-right-angle reflecting prism-Daowei prism-right-angle reflecting prism-exit form a light propagation channel. The entrance is located below the visual avoidance hole, and the exit is located below the back-facing camera. The X-axis, Y-axis, and Z-axis coordinates of the entrance and exit are finely adjusted by the X-axis fine-tuning slide, Y-axis fine-tuning slide, and Z-axis fine-tuning slide, respectively.

4. The positioning method of the wafer back-cut visual positioning system according to claim 1, characterized in that: A laser rangefinder is mounted on the bracket and is located on one side of the laser generator.

5. The positioning method of the wafer back-cut visual positioning system according to claim 1, characterized in that: In step (2), the high-magnification camera position coordinates for visual obstacle avoidance hole location calibration are (X... hi ,Y hi The coordinates of the back-facing camera position, as determined by the visual obstacle avoidance hole position, are (X...). bi ,Y bi ), i = (A, B, C).

6. The positioning method of the wafer back-cut visual positioning system according to claim 1, characterized in that: In step (3), the coordinates of the center of the back-facing camera image of the visual avoidance hole are (X... bi1 ,Y bi1 The center coordinates of the high-magnification camera image of the visual avoidance hole are (X... hi1 ,Y hi1 ).

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