Method and device for directionally inducing growth of cracks in laser lift-off

Abstract

The invention discloses a method and a device for directionally inducing growth of cracks in laser lift-off, and relates to the technical field of silicon carbide crystal ingot slicing. The method comprises the steps that at least two lasers are utilized, multiple times of cross scanning is conducted on a preset plane in a crystal ingot through multi-pulse laser, the first time is a bow-shaped track, a specific included angle is formed between subsequent scanning and previous scanning, and focuses are longitudinally staggered, so that a mixed modified structure capable of restraining longitudinal cracks is formed; after scanning is completed, transverse ultrasonic vibration is applied to the crystal ingot immersed in the liquid, and cracks are promoted to directionally expand along the mixed modified structure so as to peel off the wafer. The device comprises a cylinder body, a frame body, and a holding unit, a laser irradiation unit, an ultrasonic unit, a control unit and a separation unit which are integrated on the frame body. Through the synergistic effect of cross scanning, focus dislocation, AI monitoring and ultrasonic directional excitation, accurate control and high-quality stripping of cracks are achieved, and the wafer surface quality, the yield and the machining efficiency are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide ingot slicing technology, specifically to a method and apparatus for directional induced growth of cracks during laser ablation. Background Technology

[0002] Silicon carbide, as a third-generation wide-bandgap semiconductor material, has wide applications in high-temperature, high-frequency, and high-power devices. However, its extremely high hardness and chemical inertness also make wafer slicing a key challenge and cost center in the manufacturing process.

[0003] Traditional multi-wire dicing technology suffers from problems such as high material loss (kerf loss), low dicing efficiency, and deep surface damage on wafers. Laser ablation technology, as an emerging non-contact dicing method, focuses a laser onto the interior of the ingot to form a modified layer, and then uses external force to separate the wafer along this layer. Theoretically, this can significantly reduce material loss and improve processing efficiency.

[0004] However, existing laser ablation technology still faces many challenges: First, the modified layer formed by laser scanning is usually relatively uniform, but during subsequent separation, the direction of crack propagation is difficult to control precisely, which can easily lead to unexpected longitudinal cracks, resulting in wafer breakage or deterioration of surface roughness; Second, the laser scanning process lacks real-time monitoring and feedback, making it impossible to dynamically adjust process parameters according to the microscopic differences in ingot quality, and yield and consistency are difficult to guarantee; Finally, the separation process relies heavily on mechanical stress, which carries risks such as uneven application and excessive instantaneous impact force, which can easily cause hidden damage to brittle silicon carbide wafers.

[0005] Therefore, there is an urgent need for a new laser ablation method and device that can precisely control the directional growth of cracks and achieve high-quality, high-efficiency slicing. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for directional induced crack growth in laser ablation, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for directional induced growth of cracks in laser ablation, used for slicing silicon carbide ingots, comprising the following steps: a. Set up at least two lasers and control the pulse parameters of the lasers, wherein the pulse envelope pulse width ranges from 200fs to 1000us, the sub-pulse pulse width ranges from 200fs to 50us, and the number of pulses is 1-15; b. Use a concentrator to focus the laser beam onto a preset plane at a preset depth inside the silicon carbide ingot, and use a CCD camera to correct the focus position. c. Control the laser to perform multiple cross scans: The first scan uses a bow-shaped trajectory to cover the entire preset plane to form a preliminary modified layer; the direction of each subsequent scan is at an angle of 1-110 degrees to the previous one, and the scanning focus is offset in the longitudinal direction to form a hybrid modified structure and suppress longitudinal cracks. d. During the scanning process, based on the crack images acquired by the sensors, artificial intelligence technology is used to analyze and dynamically adjust the laser parameters and the scanning process in real time. e. After scanning, apply adjustable transverse ultrasonic vibration to the ingot to promote the transverse propagation of cracks along the mixed modified structure until the wafer is peeled off. f. Clean the stripped wafer to remove surface residues and control the wafer surface roughness to within 20μm.

[0008] Preferably, the total number of laser scans in step c is 1-N times, and is dynamically determined based on the quality of the silicon carbide ingot.

[0009] Preferably, in step c, the focal position of the second and subsequent laser scans is offset longitudinally relative to the previous scan, in order to limit the propagation range of the longitudinal crack.

[0010] Preferably, the artificial intelligence technology in step d includes deep learning, visual image processing, or large model artificial intelligence technology.

[0011] Preferably, the frequency and amplitude of the ultrasonic vibration in step e are set according to the characteristics of the hybrid modified structure.

[0012] Preferably, the cleaning in step f is performed using a predetermined solvent.

[0013] A laser ablation crack directional induction growth device includes a cylinder and a frame fixed on the cylinder. A holding unit is installed on the cylinder. The holding unit includes a worktable and a lifting drive. The worktable is used to load the silicon carbide ingot to be cut. The lifting drive is fixedly connected to the bottom end of the cylinder and its output end is fixedly connected to the worktable. An ultrasonic unit, comprising an ultrasonic generator fixed on a cylinder, the output end of which is located inside the cylinder, and the cylinder containing a liquid as the ultrasonic transmission medium. The frame is equipped with a laser irradiation unit, which includes a laser and a concentrator located at the bottom of the laser. The concentrator is used to adjust the focal position of the laser. Sensors for real-time acquisition of images of cracks on the surface of crystal ingots and CCD cameras for correcting the focus position of lasers.

[0014] Control unit, which is equipped with a device for collecting sensor and CCD data, analyzing the data, and providing feedback to adjust the laser pulse parameters; The frame is also equipped with a detachment unit, which is used in conjunction with the ultrasonic unit to automatically peel the wafer off the ingot.

[0015] Preferably, the detachment unit includes an air pump fixed to the frame, a flexible hose fixedly connected to the air pump's air intake, an air pipe one fixedly connected to the bottom end of the flexible hose, an air pipe two connected to the front end of the air pipe one, an air pipe three fixedly connected to the front end of the air pipe two, and a suction cup fixedly connected to the bottom end of the air pipe three; the suction cup is in contact with the upper surface of the crystal ingot; the frame is provided with a driving unit, which is used to drive the suction cup to move to the position in contact with the crystal ingot.

[0016] Preferably, the drive unit includes a fixed plate fixed to the frame, a motor fixedly connected to the fixed plate, an electric clamp fixedly connected to the output shaft of the motor, and the electric clamp clamping with the air tube; a slider fixedly connected to the air tube, slide rails symmetrically provided on the left and right sides of the slider, the slide rails being double slide rails and fixedly connected to the cylinder; the slider is slidably connected to the slide rails, and the upper part of the slide rails is a quarter-circle shape.

[0017] Preferably, the second air tube is made of an elastic material and is threaded with a lead screw, which is self-locking and has its bottom end rotatably connected to the inner wall of the second air tube; the second air tube has two reinforcing rods inside, and the two ends of the reinforcing rods are fixedly connected to the first air tube and the third air tube, respectively; a winding machine is fixedly connected to the frame, and a pull rope is wound on the winding machine's reel, with the bottom end of the pull rope fixedly connected to the second air tube.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention applies a stable and controllable lateral pre-separation force to the wafer before ultrasonic separation. This pre-tightening force is aligned with the uniform lateral stress generated by the ultrasonic unit through the liquid medium. The two work synergistically to effectively suppress the longitudinal propagation of cracks into the wafer body and ensure that separation energy is efficiently guided to a predetermined plane. This composite separation mode of "mechanical pre-tightening + ultrasonic excitation" fundamentally solves the problem of random crack propagation, thereby significantly improving wafer surface roughness (controllable within 20 μm) and yield, and avoiding mechanical damage through non-contact force control in the device.

[0019] This invention integrates complex multi-step processes into a smooth, automated processing system through a highly integrated and intelligent device architecture, significantly improving processing reliability and efficiency. The device integrates a holding unit, laser irradiation unit, ultrasonic unit, detachment unit, and a core control unit. Based on real-time monitoring data from sensors and a CCD camera, the control unit dynamically adjusts laser parameters and scanning paths using artificial intelligence technology, achieving adaptive processing to microscopic differences in the quality of silicon carbide ingots. Furthermore, the linked design of the detachment unit and the holding unit (lifting drive component) allows the wafer to be automatically lifted off the liquid surface and transferred the instant it is separated under ultrasonic action, achieving unmanned "separation-wafer removal" operation. This not only avoids the risks, contamination, and efficiency bottlenecks associated with manual operation but also ensures the consistency and high yield of the detachment quality of each wafer in mass production through data-driven processes and closed-loop feedback throughout the entire process. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention; Figure 2 This is a rear view schematic diagram of the device in this invention; Figure 3 This is a schematic diagram of the disassembled structure of the device in this invention; Figure 4 This is a cross-sectional view of the cylindrical body in this invention; Figure 5 This is a schematic cross-sectional view of the second trachea in this invention; Figure 6 This is a schematic diagram of the frame structure in this invention; Figure 7 This is a schematic diagram of the laser irradiation unit in this invention; Figure 8 This is a flowchart of the method of the present invention; Figure 9 This is a schematic diagram of the first laser scanning path in this invention; Figure 10 This is a schematic diagram of the second laser scanning path in this invention; Figure 11 This is a schematic diagram of the third laser scanning path in this invention.

[0021] The attached diagram lists the components represented by each number as follows: 1. Cylinder; 2. Frame; 3. Workbench; 4. Lifting drive; 5. Ultrasonic generator; 6. Laser; 7. Concentrator; 8. Sensor; 9. CCD camera; 10. Control unit; 11. Air pump; 12. Hoses; 13. Air hose 1; 14. Air hose 2; 15. Air hose 3; 16. Suction cup; 17. Fixing plate; 18. Motor; 19. Electric clamp; 20. Slider; 21. Slide rail; 22. Lead screw; 23. Reinforcing rod; 24. Winding machine; 25. Pull rope. Detailed Implementation

[0022] Please see Figure 1-11 This invention provides a technical solution: a method for directional induced growth of cracks in laser ablation, used for slicing silicon carbide ingots, comprising the following steps: a. Set up at least two lasers 6 and control the pulse parameters of the lasers 6, wherein the pulse envelope pulse width ranges from 200fs to 1000us, the sub-pulse pulse width ranges from 200fs to 50us, and the number of pulses is 1-15. b. The laser beam is focused by the condenser 7 onto a preset plane at a preset depth inside the silicon carbide ingot, and the focus position is corrected by the CCD camera 9. c. Control the laser 6 to perform multiple cross scans: The first scan uses a bow-shaped trajectory to cover the entire preset plane to form a preliminary modified layer; the direction of each subsequent scan is at an angle of 1-110 degrees to the previous one, and the scanning focus is offset in the longitudinal direction to form a hybrid modified structure and suppress longitudinal cracks. d. During the scanning process, based on the crack images acquired by sensor 8, artificial intelligence technology is used to analyze and dynamically adjust the laser parameters and scanning process in real time. e. After scanning, apply adjustable transverse ultrasonic vibration to the ingot to promote the transverse propagation of cracks along the mixed modified structure until the wafer is peeled off. f. Clean the stripped wafer to remove surface residues and control the wafer surface roughness to within 20μm; As a further aspect of the present invention, the total number of laser scans in step c is 1-N times, and is dynamically determined according to the quality of the silicon carbide ingot; As a further aspect of the present invention, in step c, the focal position of the second and subsequent laser scans is offset in the longitudinal direction relative to the previous scan, so as to limit the propagation range of the longitudinal crack. As a further aspect of the present invention, the artificial intelligence technology in step d includes deep learning, visual image processing, or large model artificial intelligence technology. As a further aspect of the present invention, the frequency and amplitude of the ultrasonic vibration in step e are set according to the characteristics of the hybrid modified structure; As a further aspect of the present invention, the cleaning in step f is performed using a predetermined solvent.

[0023] See Figure 1-7 A laser ablation crack directional induction growth device includes a cylinder 1 and a frame 2 fixed on the cylinder 1. The cylinder 1 is equipped with The holding unit includes a worktable 3 and a lifting drive 4. The worktable 3 is used to load the silicon carbide ingot to be cut. The lifting drive 4 is fixedly connected to the bottom end of the cylinder 1 and its output end is fixedly connected to the worktable 3. The ultrasonic unit includes an ultrasonic generator 5 fixed on the cylinder 1. The output end of the ultrasonic generator 5 is located inside the cylinder 1, and the inside of the cylinder 1 is filled with a liquid as the ultrasonic transmission medium. Mounted on frame 2 The laser irradiation unit includes a laser 6 and a concentrator 7 disposed at the bottom of the laser 6. The concentrator 7 is used to adjust the focal position of the laser 6. Sensor 8 for real-time acquisition of images of cracks on the surface of ingots and CCD camera 9 for correcting the focal position of laser 6.

[0024] Control unit 10 is installed to collect data from sensor 8 and CCD, analyze the data, and provide feedback to adjust the laser pulse parameters. The frame 2 is also equipped with a detachment unit, which is used in conjunction with the ultrasonic unit to automatically peel the wafer off the ingot. During operation, the laser 6 is activated, and the focus of the laser 6 is controlled at a specific thickness position inside the crystal ingot by controlling the concentrator 7. Then, the laser can be controlled to start scanning inside the crystal ingot to form a modified layer. After the laser scan is completed, the lifting drive 4 is activated to move the worktable 3 downwards. The worktable 3 then moves the crystal ingot downwards. Once the crystal ingot is immersed in the ultrasonic liquid transmission medium inside the cylinder 1, the lifting drive 4 is stopped and the ultrasonic generator 5 is activated. The ultrasonic generator 5 generates a powerful ultrasonic field, which transmits energy evenly to the crystal ingot through the liquid. The liquid, as the sound transmission medium, can evenly coat the entire surface of the crystal ingot with ultrasonic energy. When the ultrasonic waves generate a "cavitation effect" (the formation and violent collapse of tiny bubbles in the liquid), these microjets and shock waves act simultaneously on the entire surface of the crystal ingot, thereby evenly "injecting" stress into the internal modified layer, achieving the effect of separating the wafer. The propagation of ultrasonic waves through the liquid makes the stress distribution extremely uniform, which can better protect the crystal ingot and has good process controllability, making it suitable for separating wafers of any complex shape. Once the wafer is separated from the ingot, it can be separated from the ingot by using a detachment unit, and then the wafer can be removed.

[0025] See Figure 4-6 As a further embodiment of the present invention, the detachment unit includes an air pump 11 fixed on the frame 2. A hose 12 is fixedly connected to the air pump 11's air intake port. An air pipe 13 is fixedly connected to the bottom end of the hose 12. An air pipe 14 is connected to the front end of the air pipe 13. An air pipe 15 is fixedly connected to the front end of the air pipe 14. A suction cup 16 is fixedly connected to the bottom end of the air pipe 15. The suction cup 16 is attached to the upper surface of the crystal ingot. A driving unit is provided on the frame 2. The driving unit is used to drive the suction cup 16 to move to the position attached to the crystal ingot. See Figure 6 As a further embodiment of the present invention, the drive unit includes a fixed plate 17 fixed on the frame 2, a motor 18 fixedly connected to the fixed plate 17, an electric clamp 19 fixedly connected to the output shaft of the motor 18, and the electric clamp 19 clamping and engaging with the air tube 13; a slider 20 fixedly connected to the air tube 13, slide rails 21 symmetrically provided on the left and right sides of the slider 20, the slide rails 21 being double slide rails and fixedly connected to the cylinder 1; the slider 20 and the slide rails 21 being slidably connected, and the upper part of the slide rails 21 being a quarter-circle shape; During operation, before starting the lifting drive 4 to move the worktable 3 downward, the motor 18 is started to drive the electric clamp 19 to rotate. The electric clamp 19 then drives the suction cup 16 to rotate to the position of adhering to the upper surface of the crystal ingot through the air pipe 13, air pipe 2 14 and air pipe 3 15. At this time, the vacuum pump 11 is started. The vacuum pump 11 can create a negative pressure inside the suction cup 16 by vacuuming air, so that the suction cup 16 is firmly adhering to the surface of the crystal ingot. Once the suction cup 16 is stably attached to the surface of the crystal ingot, the electric clamp 19 can be driven to release the air pipe 13. As the lifting drive 4 moves the worktable 3 and the crystal ingot downwards, the suction cup 16, air pipe 13, air pipe 2 14, and air pipe 3 15 all move downwards simultaneously. When the crystal ingot is submerged in the liquid, air pipe 13, air pipe 2 14, and air pipe 3 15 also move to a position in contact with the liquid. Since air pipe 13, air pipe 2 14, and air pipe 3 15 contain air, they will experience buoyancy on the liquid surface and exert a force on the wafer to be separated on the upper surface of the crystal ingot. After the ultrasonic generator is activated, the modified layer inside the crystal ingot begins to split continuously. During the splitting process, the wafer is subjected to an upward force, which can effectively prevent longitudinal splitting of cracks. At the same time, after the modified layer is completely split, the wafer can detach from the crystal ingot immediately, which can effectively save the time of wafer separation.

[0026] See Figure 5As a further embodiment of the present invention, the second air tube 14 is made of an elastic material and a screw 22 is threadedly connected to the second air tube 14. The screw 22 has self-locking properties and its bottom end is rotatably connected to the inner wall of the second air tube 14. Two reinforcing rods 23 are provided inside the second air tube 14, and the two ends of the reinforcing rods 23 are fixedly connected to the first air tube 13 and the third air tube 15, respectively. A winding machine 24 is fixedly connected to the frame 2, and a pull rope 25 is wound on the winding wheel of the winding machine 24. The bottom end of the pull rope 25 is fixedly connected to the second air tube 14. During operation, rotating the lead screw 22 can compress the second air tube 14, reducing the air content inside the second air tube 14, thereby reducing the buoyancy of the second air tube 14. The buoyancy of the second air tube 14 can be adjusted according to the size of the wafer to be separated, so that the sum of the buoyancy of the three air tubes is just greater than the separation force required to separate the wafer. After the wafer is separated, starting the winding machine 24 can wind up the pull rope 25, which will pull the second air tube 14 upward to its original position.

Claims

1. A method for directional induced crack growth in laser ablation, used for slicing silicon carbide ingots, characterized in that, Includes the following steps: a. Set up at least two lasers (6) and control the pulse parameters of the lasers (6), wherein the pulse envelope pulse width ranges from 200fs to 1000us, the sub-pulse pulse width ranges from 200fs to 50us, and the number of pulses is 1-15. b. The laser beam is focused by the condenser (7) and aligned with the preset plane at a preset depth inside the silicon carbide ingot, and the focus position is corrected by the CCD camera (9). c. Control the laser (6) to perform multiple cross scans: The first scan uses a bow-shaped trajectory to cover the entire preset plane to form a preliminary modified layer; the direction of each subsequent scan is at an angle of 1°-110° to the previous one, and the scanning focus is offset in the longitudinal direction to form a mixed modified structure and suppress longitudinal cracks. d. During the scanning process, based on the crack images collected by the sensor (8), artificial intelligence technology is used to analyze and dynamically adjust the laser parameters and scanning process in real time. e. After scanning, apply adjustable transverse ultrasonic vibration to the ingot to promote the transverse propagation of cracks along the mixed modified structure until the wafer is peeled off. f. Clean the stripped wafer to remove surface residues and control the wafer surface roughness to within 20μm.

2. The method according to claim 1, characterized in that: The total number of laser scans in step c is 1-N, and is dynamically determined based on the quality of the silicon carbide ingot.

3. The method according to claim 1, characterized in that: In step c, the focal position of the second and subsequent laser scans is offset longitudinally relative to the previous scan in order to limit the propagation range of the longitudinal crack.

4. The method according to claim 1, characterized in that: The artificial intelligence technology in step d includes deep learning, visual image processing, or large model artificial intelligence technology.

5. The method according to claim 1, characterized in that: In step e, the frequency and amplitude of the ultrasonic vibration are set according to the characteristics of the hybrid modified structure.

6. The method according to claim 1, characterized in that: The cleaning in step f is performed using a predetermined solvent.

7. A laser ablation crack directional induction growth device, comprising a cylinder (1) and a frame (2) fixed on the cylinder (1), characterized in that: The cylinder (1) is equipped with The holding unit includes a worktable (3) and a lifting drive (4). The worktable (3) is used to load the silicon carbide ingot to be cut. The lifting drive (4) is fixedly connected to the bottom end of the cylinder (1) and its output end is fixedly connected to the worktable (3). An ultrasonic unit, comprising an ultrasonic generator (5) fixed on a cylinder (1), the output end of the ultrasonic generator (5) being located inside the cylinder (1), and the cylinder (1) containing a liquid as the ultrasonic transmission medium. The frame (2) is equipped with The laser irradiation unit includes a laser (6) and a concentrator (7) disposed at the bottom of the laser (6), the concentrator (7) being used to adjust the focal position of the laser (6); A sensor (8) for real-time acquisition of images of cracks on the surface of ingots and a CCD camera (9) for correcting the focal position of the laser (6).

8. Control unit (10), which is equipped with a device for collecting data from the sensor (8) and CCD, analyzing the data, and providing feedback to adjust the laser pulse parameters; The frame (2) is also provided with a detachment unit, which is used in conjunction with the ultrasonic unit to automatically peel the wafer off the ingot.

9. The laser ablation crack directional induction growth device according to claim 7, characterized in that: The detachment unit includes a vacuum pump (11) fixed on the frame (2). The vacuum pump (11) has a hose (12) fixedly connected to its suction port. The bottom end of the hose (12) is fixedly connected to an air pipe (13). The front end of the air pipe (13) is connected to an air pipe (2) (14). The front end of the air pipe (2) (14) is fixedly connected to an air pipe (3) (15). The bottom end of the air pipe (3) (15) is fixedly connected to a suction cup (16). The suction cup (16) is attached to the upper surface of the crystal ingot. The frame (2) is provided with a driving unit, which is used to drive the suction cup (16) to move to the position attached to the crystal ingot.

10. The laser ablation crack directional induction growth device according to claim 8, characterized in that: The drive unit includes a fixed plate (17) fixed on the frame (2), a motor (18) fixedly connected to the fixed plate (17), an electric clamp (19) fixedly connected to the output shaft of the motor (18), and the electric clamp (19) clamping and cooperating with the first air tube (13); a slider (20) fixedly connected to the first air tube (13), and slide rails (21) symmetrically provided on the left and right sides of the slider (20), the slide rails (21) are double slides and the slide rails (21) are fixedly connected to the cylinder (1); the slider (20) is slidably connected to the slide rails (21), and the upper part of the slide rails (21) is a quarter ring shape. A laser ablation crack directional induction growth device according to claim 8, characterized in that: The second air tube (14) is made of elastic material and a screw (22) is threaded onto the second air tube (14). The screw (22) is self-locking and its bottom end is rotatably connected to the inner wall of the second air tube (14). Two reinforcing rods (23) are provided inside the second air tube (14). The two ends of the reinforcing rods (23) are fixedly connected to the first air tube (13) and the third air tube (15) respectively. A winding machine (24) is fixedly connected to the frame (2). A pull rope (25) is wound on the winding wheel of the winding machine (24). The bottom end of the pull rope (25) is fixedly connected to the second air tube (14).

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