Semiconductor material laser stripping crack real-time online monitoring device and method based on laser ultrasound

Abstract

The invention relates to a semiconductor material laser stripping crack real-time online monitoring device and method based on laser ultrasound, and belongs to the technical field of semiconductor processing and nondestructive testing, the device combines a laser ultrasonic nondestructive testing technology and a laser stripping technology, laser is utilized to excite ultrasonic waves and detect the expansion condition of cracks in real time, and the laser stripping crack real-time online monitoring device and method based on laser ultrasound are obtained. Therefore, high-precision automatic detection of cracks is realized. By means of the device, real-time observation can be conducted on the expansion condition of cracks in the laser stripping piece, feedback data can be provided for a laser processing system, excessive expansion of the cracks is effectively avoided, and an innovative solution is provided for processing of third-generation semiconductor materials.

Description

Technical Field

[0001] The invention relates to a real-time online monitoring device and method for laser peeling cracks of semiconductor materials based on laser ultrasound, belonging to the technical field of semiconductor processing and nondestructive testing. Background Art

[0002] With the widespread application of third-generation semiconductor materials such as silicon carbide, its excellent properties such as high hardness, high strength, and high heat resistance have been rapidly developed in the fields of microelectronics, radio frequency, etc. These materials perform well in extreme environments such as high temperature, high frequency, and high power, promoting the demand for miniaturization and integration of electronic devices. However, in the process of laser processing of semiconductor materials, especially in the process of ingot stripping, the formation of cracks and voids has become a key issue affecting material quality and processing efficiency. Cracks not only damage the structural integrity of the material, but may also further expand, ultimately leading to a decrease in device performance. Therefore, real-time online monitoring of cracks during laser stripping is particularly important.

[0003] Traditional laser stripping crack detection methods usually rely on optical microscopes. Although this method can observe the existence of cracks, it has obvious limitations. First, the use of optical microscopes is not only time-consuming, but also requires contact with the surface of the ingot during the detection process, which may damage the internal structure of the ingot. Especially in high-precision processing, this contact detection method is difficult to meet the requirements. Secondly, optical microscopes cannot achieve real-time online monitoring and can only be used for post-processing after the processing is completed. It is impossible to warn and deal with crack extension problems in a timely manner. In order to solve the above problems, laser ultrasonic non-destructive testing technology, relying on its non-contact and high sensitivity characteristics, has become a more advanced defect detection method. This technology uses pulsed laser to excite ultrasonic waves, and then uses continuous laser to detect the propagation characteristics of ultrasonic waves, thereby realizing the detection of surface or internal defects of materials. Compared with optical microscopes, laser ultrasonic testing not only avoids the damage to materials caused by contact detection, but also can monitor the expansion of cracks in real time, thereby providing more accurate and timely feedback.

[0004] Laser ultrasonic crack detection technology, common detection methods or devices in the prior art such as patent documents CN113504182 A and CN 110146449 A, require the material to be immersed in a water tank or in a specific environment, and the material to be tested is tested in a static environment, that is, the detection device and the processing device are separate. The detection results are often used for offline quality control or subsequent analysis, and cannot be used for real-time online monitoring. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a real-time online monitoring device and method for laser peeling cracks based on laser ultrasound. The device combines laser ultrasonic nondestructive testing technology with laser peeling technology, uses laser to excite ultrasonic waves and detects the expansion of cracks in real time, thereby realizing high-precision automatic detection of cracks. Through this device, not only can the expansion of cracks in laser peeling be observed in real time, but also feedback data can be provided to the laser processing system, effectively avoiding excessive expansion of cracks, and providing an innovative solution for the processing of third-generation semiconductor materials.

[0006] The technical solution of the present invention is as follows:

[0007] A real-time online monitoring device for cracks in laser flaking of semiconductor materials based on laser ultrasound, comprising a PC master controller and an ultrashort pulse laser control unit, a pulse laser control unit, a spatial light modulator, a focusing system, a three-dimensional mobile platform, an electronic scanning galvanometer and a heterodyne interferometer vibrometer, and a crack feedback control system connected thereto, wherein the PC master controller is used to receive feedback signals from the crack feedback control system and send control instructions to other devices;

[0008] The ultrashort pulse laser control unit is used to emit ultrashort pulse laser to the spatial light modulator, and then to the surface of the ingot via the focusing system;

[0009] The pulse laser emitted by the pulse laser control unit is incident on the photodetector and lens through the polarization beam splitter. The photodetector is connected to the electronic scanning galvanometer and FPGA respectively. The light beam on the lens is incident on the surface of the ingot.

[0010] The three-dimensional mobile platform is used to place the monitored crystal ingot, the electronic scanning galvanometer is used to scan the surface of the crystal ingot and input it into the heterodyne interferometer vibrometer, the heterodyne interferometer vibrometer is used to convert the signal and input it into the FPGA, the FPGA is used to obtain the vibration displacement map and the ultrasonic propagation path map, the display is connected to the FPGA to display the processing results of the FPGA; the FPGA is connected to the PC master controller through the crack feedback control system.

[0011] Preferably, the light beam on the lens is incident on the surface of the ingot near the ultrashort pulse light position area through the first reflector and the second reflector to excite the ultrasonic wave. The two reflectors can more accurately adjust the light path to make it close to the ultrashort pulse light position area.

[0012] Preferably, on the surface of the ingot, the horizontal distance between the incident position of the pulsed laser through the lens and the incident point position of the laser from the focusing system is controlled to be within 1 mm.

[0013] Preferably, a third reflector is provided between the electronic scanning galvanometer and the surface of the crystal ingot, so as to better scan the area to be scanned in the existing optical path.

[0014] A real-time online monitoring method for laser peeling cracks of semiconductor materials based on laser ultrasound comprises the following steps:

[0015] (1) The PC master controller first sends a control command to the ultrashort pulse laser control unit to control the ultrashort pulse laser to be incident on the spatial light modulator. The spatial light modulator receives the control command from the PC master controller, modulates the ultrashort pulse laser into a split beam and injects it into the focusing system. The PC master controller can adjust the focal length of the focusing system. The focusing system injects the split light into a certain depth inside the ingot to be stripped to perform laser processing operations.

[0016] (2) After the PC master controller sends a single ultrashort pulse laser emission command to the ultrashort pulse laser control unit, it delays for at least 100 μs and then sends a control command to the 1064 / 355 nm pulse laser control unit to emit a set number of times N. 2 The multi-pulse laser has the same parameters for each pulse laser emission. The pulse laser first passes through a polarization beam splitter (PBS), enters a photodetector as a trigger signal for the operation of a heterodyne interferometer vibrometer and an electronic scanning galvanometer, and enters a lens. After the first reflector and the second reflector precisely adjust the direction of the optical path, the pulse laser is incident on the surface of the ingot near the position of the ultrashort pulse light to excite ultrasonic waves. At the same time, the incident position of the pulse laser and the position of the laser incident point from the focusing system are controlled to be within a horizontal distance of 1 mm.

[0017] (3) After receiving the trigger signal instruction from the pulse laser, the FPGA starts signal acquisition. After receiving the trigger signal, the electronic scanning galvanometer adjusts its position once. The PC master controller controls the electronic scanning galvanometer to adjust the position frequency to be consistent with the pulse laser repetition frequency. The number of times the electronic scanning galvanometer moves is consistent with the number of times the pulse laser is emitted. The relative position of the scanning area and the pulse laser and ultrashort pulse laser remains unchanged. Each time the pulse laser is emitted, the electronic scanning galvanometer moves its position once, and receives the measurement light from each point returned by the third reflector and the electronic scanning galvanometer into the heterodyne interferometer vibrometer.

[0018] Ultrashort pulse laser is used as the processing laser for laser peeling. Every time the laser is emitted, it triggers the pulse laser to emit N 2 The pulse laser excites the material to produce ultrasonic waves. Each time the pulse laser is emitted, it triggers the scanning galvanometer to move and the vibrometer to collect data.

[0019] (4) The heterodyne interferometer vibrometer uses an internal photodetector to convert the interfering optical signal into a low-frequency electrical signal with high frequencies filtered out, and sends the electrical signal to a high-speed FPGA system for signal storage and demodulation. The demodulation includes down-mixing, inverse tangent demodulation, phase unwrapping, and fast Fourier transform, and can output the vibration signal of each position over time. In addition, the amplitude of each vibration signal at the same time can be plotted to obtain a one-dimensional or two-dimensional ultrasonic propagation path diagram at different times. The display is used to display the vibration displacement diagram and the one-dimensional or two-dimensional ultrasonic propagation path diagram.

[0020] (5) The crack size is obtained by calculating the vibration displacement through the corresponding function ∑f(v, t), or the crack size is obtained by image processing of the ultrasonic propagation path diagram;

[0021] When it is detected that the crack size exceeds the set threshold, the crack feedback control system will send a feedback signal to the PC master controller, and the PC master controller sends an instruction to stop the ultrashort pulse laser emission or set the ultrashort pulse laser pulse width parameter to increase, the energy and repetition rate parameters to decrease, and sends a phase adjustment control instruction to the spatial light modulator to change the energy distribution of the ultrashort pulse scanning laser. The purpose of this is to adjust the laser processing parameters in real time to prevent the crack from further expanding, ensure the stability and processing quality of the processing process, and at the same time, by optimizing the laser energy distribution, reduce the risk of crack generation, and improve processing efficiency and reliability; if the PC master controller does not receive the feedback instruction, wait for the 1064 / 355nm pulse laser emission count to stop, that is, after the ultrashort pulse laser control instruction is sent, set the timing, and after the timing ends and no feedback signal is received, the PC master controller sends a control instruction to the three-dimensional mobile platform. Each time the mobile platform adjusts its position, the absolute position of the area where the laser is scanned on the ingot changes, thereby realizing laser scanning of the set route in laser stripping. Repeating the above operations can perform real-time crack monitoring on the laser stripping of semiconductor materials.

[0022] Preferably, in step (3), the initial position of the electronic scanning galvanometer is set at the lower left corner of the area to be measured, and the specific movement method when adjusting the position is as follows: first move N times in the vertical direction, each time moving a preset step length S, then move right once in the horizontal direction, move a preset step length S, then move down N times in the vertical direction, move right once in the horizontal direction again, continue to move N times in the vertical direction, move right once in the horizontal direction, until a total of N times in the horizontal direction are moved, the entire scanning process is completed, and then move left N preset steps in the horizontal direction to return to the initial position.

[0023] Further preferably, in step (3), N is an even number.

[0024] Preferably, in step (5), the crack size is obtained through function calculation. For a single defect material, the length, width or depth of the defect is linearly related to the sound wave arrival time t or the sound wave vibration amplitude v in the one-dimensional vibration displacement diagram after simulation calculation. The mathematical expression can be expressed as L=k·v+b or L=k'·t+b', where L represents the length or width of the crack, k and k' are proportional coefficients, b and b' are constants, and these parameters need to be verified through experiments and simulations. At the edge of the defect, the sound wave amplitude will increase sharply. By detecting the point where the sound wave amplitude increases sharply, the crack boundary can be determined. The specific method is to calculate the amplitude change rate between adjacent detection points. When the change rate exceeds the set threshold, the crack boundary is determined.

[0025] Preferably, in step (5), the crack size is obtained using the ultrasonic wave propagation path diagram. When the ultrasonic wave propagation path diagram is scan B, the change of the acoustic wave amplitude at different positions over time is determined. When the ultrasonic wave propagation path diagram is scan C, the amplitude at each position at a certain moment is determined to generate a two-dimensional distribution diagram. The image processing step includes denoising, contrast enhancement, and canndy edge detection in FPGA, thereby calculating the length and width of the crack.

[0026] Preferably, in step (5), the three-dimensional mobile platform moves in the following manner: first, it moves in the vertical direction. 1 Each time, move the preset step length l, then move right once in the horizontal direction, move a preset step length l, and then move down K in the vertical direction 1 Move right again in the horizontal direction, and then move K in the vertical direction. 1 times, and move right once horizontally, until the total horizontal movement is K 2 At this time, the scanning process of one layer of laser peeling is completed, and then it moves left in the horizontal direction K 2 The platform returns to the initial position with a preset step length, the first layer of ultra-short pulse laser scanning ingot stripping is completed, and the displacement platform moves up one w, waiting to start the second layer of laser stripping scanning.

[0027] More preferably, K 2 Is an even number.

[0028] The beneficial effects of the present invention are:

[0029] The present invention is characterized in that it combines laser peeling and ultrasonic testing, and uses real-time signal processing and feedback mechanism to adjust laser processing parameters during laser processing, thereby reducing the formation of harmful cracks and voids during laser processing, improving the quality control level of laser peeling process, and realizing the connection between processing and testing through an automated control system.

[0030] The present invention can realize real-time online monitoring during the laser peeling process, directly detect cracks generated during the dynamic processing process through a real-time feedback mechanism, adjust laser processing parameters in time, and optimize the processing process.

[0031] In the present invention, laser ultrasonic technology is used in combination with an optimized signal processing algorithm, and the crack size is analyzed from both the vibration signal displacement and the sound wave propagation path image processing, which has significant advantages in detection accuracy and sensitivity.

[0032] In the present invention, a non-contact method is adopted to avoid physical contact with the material to be tested and possible damage, and is particularly suitable for high-energy semiconductor material laser stripping processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the present invention; wherein: 1, a first reflector, 2, a second reflector, 3, a third reflector;

[0034] Figure 2 It is a schematic diagram of the operation steps of the real-time online monitoring device for laser peeling cracks based on laser ultrasound;

[0035] Figure 3 This is the crack signal processing flow chart;

[0036] Figure 4 This is a typical one-dimensional diagram of the acoustic wave propagation path after the presence of a crack;

[0037] Figure 5 This is a typical two-dimensional diagram of the acoustic wave propagation path after the presence of a crack. DETAILED DESCRIPTION

[0038] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings, but is not limited thereto.

[0039] Embodiment 1:

[0040] A real-time online monitoring device for laser peeling cracks of semiconductor materials based on laser ultrasound, such as Figure 1 As shown, it includes a PC master controller and an ultrashort pulse laser control unit, a pulse laser control unit, a spatial light modulator, a focusing system, a three-dimensional mobile platform, an electronic scanning galvanometer and a heterodyne interferometer vibrometer, and a crack feedback control system connected thereto. The PC master controller is used to receive feedback signals from the crack feedback control system and send control instructions to other devices.

[0041] The ultrashort pulse laser control unit is used to emit ultrashort pulse lasers to the spatial light modulator, and then to the surface of the ingot through the focusing system. The ultrashort pulse laser and ultrashort pulse laser control unit can use the WD-HE-800-tunable of White Dwarf HE OPCPA, with adjustable pulse width of picosecond or femtosecond, external triggering, laser power greater than 100mW, and adjustable energy repetition rate. The spatial light modulator shifts the frequency by 40MHz or 80MHz. The focusing system is composed of a combination of lenses with different focal lengths, and the focal length is adjustable from 20mm to 100mm.

[0042] The pulse laser emitted by the pulse laser control unit is incident on the photodetector and lens through the polarization beam splitter. The photodetector is connected to the electronic scanning galvanometer and FPGA respectively. The light beam on the lens is incident on the surface of the ingot. TM -A-1064-10W-SF, can be externally triggered, trigger 1064nm or 355nm pulse laser, pulse width less than 20ns, single pulse energy 2mJ-100mJ adjustable, repetition rate 1-100Hz adjustable.

[0043] The three-dimensional mobile platform is used to place the monitored crystal ingot, the electronic scanning galvanometer is used to scan the surface of the crystal ingot and input it into the heterodyne interferometer vibrometer, the heterodyne interferometer vibrometer is used to convert the signal and input it into the FPGA, the FPGA is used to obtain the vibration displacement map and the ultrasonic propagation path map, the display is connected to the FPGA to display the processing results of the FPGA; the FPGA is connected to the PC master controller through the crack feedback control system.

[0044] The light beam on the lens is incident on the surface of the ingot near the ultrashort pulse light position area through the first reflector and the second reflector to excite the ultrasonic wave. The two reflectors can more accurately adjust the light path to make it close to the ultrashort pulse light position area.

[0045] On the surface of the ingot, the incident position of the pulsed laser through the lens and the laser incident point position from the focusing system are controlled to be within 1 mm in horizontal distance.

[0046] A third reflector is provided between the electronic scanning galvanometer and the surface of the crystal ingot, so as to better scan the area to be scanned in the existing optical path.

[0047] Polarization beam splitter PBS, lens, first reflector, second reflector: wavelength corresponding to pulse laser is 1064nm or 355nm, size 25.4mm, Thorlabs. Photodetector can be Thorlabs, PDA10D2, 900-2600nm. Third reflector and electronic scanning galvanometer can be 1550nm, Thorlabs, galvanometer model GVS002. Heterodyne interferometer vibrometer can be Polytec PSV QTec 3D, 1550nm continuous laser, output laser power within 10mW, line width less than 2kHz. FPGA can be selected with main frequency of 1.333GHz, memory 4GB, AXU5EVB-E, ALINX. LCD1284 display can be selected for display, with supporting FPGA development board, ALINX. The crack feedback control system is a high-speed circuit board composed of stm32f103vet6 chips. Through wireless sensor modules such as lora modules, it receives crack parameters from FPGA in real time, and packages a set of information about crack length, width, depth, and whether it exceeds the threshold. It transmits this set of information, that is, feedback electrical signals to the PC end, and has an alarm device. The three-dimensional mobile platform has an accuracy of 0.05mm, is connected to the stepper motor, and is controlled by the PC master controller. The PC master controller is an industrial tablet computer that can control multiple system units. The optional PPC-1010H-J is from Yanwei Technology Company.

[0048] Embodiment 2:

[0049] A method for real-time online monitoring of cracks in laser peeling of semiconductor materials based on laser ultrasound, wherein the device system used is as described in Example 1, and the method comprises the following steps: Figure 2 , Figure 3 As shown:

[0050] (1) The PC master controller first sends control instructions to the ultrashort pulse laser control unit to control the ultrashort pulse laser to be incident on the spatial light modulator. The spatial light modulator receives the control instructions from the PC master controller, modulates the ultrashort pulse laser into a split beam and injects it into the focusing system. The PC master controller can adjust the focal length of the focusing system. The focusing system injects the split light into a certain depth inside the ingot to be peeled for laser processing.

[0051] (2) After the PC master controller sends a single ultrashort pulse laser emission command to the ultrashort pulse laser control unit, it delays for at least 100 μs and then sends a control command to the 1064 / 355 nm pulse laser control unit to emit a set number of times N. 2The multi-pulse laser has the same parameters for each emitted pulse laser; the pulse laser first passes through a polarization beam splitter (PBS), enters the photodetector as a trigger signal for the operation of a heterodyne interferometer vibrometer and an electronic scanning galvanometer, and enters the lens. After the first reflector and the second reflector precisely adjust the direction of the optical path, the pulse laser is incident on the surface of the ingot near the position of the ultrashort pulse light to excite ultrasonic waves; at the same time, the incident position of the pulse laser and the laser incident point position from the focusing system control the horizontal distance within 1 mm.

[0052] (3) After receiving the trigger signal instruction from the pulse laser, the FPGA starts signal acquisition. After receiving the trigger signal, the electronic scanning galvanometer adjusts its position once. The PC master controller controls the electronic scanning galvanometer to adjust the position frequency to be consistent with the pulse laser repetition frequency. The number of times the electronic scanning galvanometer moves is consistent with the number of times the pulse laser is emitted. The relative position of the scanning area and the pulse laser and ultrashort pulse laser remains unchanged. Every time the pulse laser is emitted, the electronic scanning galvanometer moves once and receives the measurement light from each point returned by the third reflector and the electronic scanning galvanometer into the heterodyne interferometer vibrometer.

[0053] Ultrashort pulse laser is used as the processing laser for laser peeling. Every time the laser is emitted, it triggers the pulse laser to emit N 2 The pulsed laser excites the material to produce ultrasonic waves. Each time a pulse of laser is emitted, it triggers the movement of the scanning galvanometer and the collection of data by the vibrometer.

[0054] The initial position of the electronic scanning galvanometer is set at the lower left corner of the area to be measured. The specific movement method when adjusting the position is as follows: first move N times in the vertical direction (N is an even number), each time moving the preset step length S, then move right once in the horizontal direction, move a preset step length S, then move down N times in the vertical direction, move right once in the horizontal direction again, continue to move N times in the vertical direction, move right once in the horizontal direction, until a total of N times in the horizontal direction, complete the entire scanning process, and then move left N preset steps in the horizontal direction to return to the initial position.

[0055] (4) The heterodyne interferometer vibrometer uses an internal photodetector to convert the interfering optical signal into a low-frequency electrical signal that filters out the high frequency, and sends the electrical signal to a high-speed FPGA system for signal storage and demodulation. The demodulation includes down-mixing, inverse tangent demodulation, phase unwrapping, and fast Fourier transform, which can output the vibration signal of each position over time. In addition, the amplitude of each vibration signal at the same time can be plotted to obtain a one-dimensional or two-dimensional ultrasonic propagation path diagram at different times. The display is used to display the vibration displacement diagram and the one-dimensional or two-dimensional ultrasonic propagation path diagram.

[0056] (5) The crack size is obtained by calculating the vibration displacement through the corresponding function ∑f(v, t), or the crack size is obtained by image processing of the ultrasonic propagation path diagram.

[0057] The crack size is obtained through function calculation. For a single defect material, the length, width or depth of the defect is linearly related to the sound wave arrival time t or the sound wave vibration amplitude v in the one-dimensional vibration displacement diagram after simulation calculation. The mathematical expression can be expressed as L=k·v+b or L=k'·t+b', where L represents the length or width of the crack, k and k' are proportional coefficients, b and b' are constants. These parameters need to be verified through experiments and simulations. At the edge of the defect, the sound wave amplitude will increase sharply. By detecting the point where the sound wave amplitude increases sharply, the crack boundary can be determined. The specific method is to calculate the amplitude change rate between adjacent detection points. When the change rate exceeds the set threshold, the crack boundary is determined.

[0058] The crack size is obtained using the ultrasonic propagation path diagram. When the ultrasonic propagation path diagram is scan B, the change of the acoustic wave amplitude at different positions over time is determined. When the ultrasonic propagation path diagram is scan C, the amplitude at each position at a certain moment is determined to generate a two-dimensional distribution diagram. The image processing steps include denoising, contrast enhancement, and canndy edge detection in FPGA, so as to calculate the length and width of the crack.

[0059] When it is detected that the crack size exceeds the set threshold, the crack feedback control system will send a feedback signal to the PC master controller, and the PC master controller sends an instruction to stop the ultrashort pulse laser emission or set the ultrashort pulse laser pulse width parameter to increase, the energy and repetition rate parameters to decrease, and sends a phase adjustment control instruction to the spatial light modulator to change the energy distribution of the ultrashort pulse scanning laser. The purpose of this is to adjust the laser processing parameters in real time to prevent the crack from further expanding, ensure the stability and processing quality of the processing process, and at the same time, by optimizing the laser energy distribution, reduce the risk of crack generation, and improve processing efficiency and reliability; if the PC master controller does not receive the feedback instruction, wait for the 1064 / 355nm pulse laser emission count to stop, that is, after the ultrashort pulse laser control instruction is sent, set the timing, and after the timing ends and no feedback signal is received, the PC master controller sends a control instruction to the three-dimensional mobile platform. Each time the mobile platform adjusts its position, the absolute position of the area where the laser is scanned on the ingot changes, thereby realizing laser scanning of the set route in laser stripping. Repeating the above operations can perform real-time crack monitoring on the laser stripping of semiconductor materials.

[0060] The specific movement of the three-dimensional mobile platform is as follows: First, move K in the vertical direction 1 Each time, move the preset step length l, then move right once in the horizontal direction, move a preset step length l, and then move down K in the vertical direction1 Move right again in the horizontal direction, and then move K in the vertical direction. 1 times, and move right once horizontally, until the total horizontal movement is K 2 Times (K 2 is an even number); at this time, the scanning process of one layer of laser peeling is completed, and then it moves left in the horizontal direction K 2 The platform returns to the initial position with a preset step length, the first layer of ultra-short pulse laser scanning ingot stripping is completed, and the displacement platform moves up one w, waiting to start the second layer of laser stripping scanning.

[0061] Depend on Figure 4 It can be seen that the one-dimensional sound wave path propagation diagram generates an obvious reflected wave with an angle when encountering a defect. Figure 5 It can be seen that after the two-dimensional path diagram encounters a defect, the sound wave at the defect is no longer complete, and the abnormal sound wave propagation position is the defect location.

Claims

1. A real-time online monitoring device for laser peeling cracks of semiconductor materials based on laser ultrasound, characterized in that: It includes a PC master controller and an ultrashort pulse laser control unit, a pulse laser control unit, a spatial light modulator, a focusing system, a three-dimensional mobile platform, an electronic scanning galvanometer and a heterodyne interferometer vibrometer, and a crack feedback control system connected thereto. The PC master controller is used to receive feedback signals from the crack feedback control system and send control instructions to other devices. The ultrashort pulse laser control unit is used to emit ultrashort pulse laser to the spatial light modulator, and then to the surface of the ingot via the focusing system; The pulse laser emitted by the pulse laser control unit is incident on the photodetector and lens through the polarization beam splitter. The photodetector is connected to the electronic scanning galvanometer and FPGA respectively. The light beam on the lens is incident on the surface of the ingot. The three-dimensional mobile platform is used to place the monitored crystal ingot, the electronic scanning galvanometer is used to scan the surface of the crystal ingot and input it into the heterodyne interferometer vibrometer, the heterodyne interferometer vibrometer is used to convert the signal and input it into the FPGA, the FPGA is used to obtain the vibration displacement map and the ultrasonic propagation path map, the display is connected to the FPGA to display the processing results of the FPGA; the FPGA is connected to the PC master controller through the crack feedback control system.

2. The real-time online monitoring device for laser peeling cracks of semiconductor materials based on laser ultrasound according to claim 1 is characterized in that: The light beam on the lens is incident on the surface of the ingot near the position of the ultrashort pulse light through the first reflector and the second reflector to excite ultrasonic waves. A third reflector is provided between the electronic scanning galvanometer and the surface of the ingot.

3. The real-time online monitoring device for laser peeling cracks of semiconductor materials based on laser ultrasound according to claim 1 is characterized in that: On the ingot surface, the horizontal distance between the incident position of the pulsed laser through the lens and the incident point position of the laser from the focusing system is within 1 mm.

4. A monitoring method for a real-time online monitoring device for laser peeling cracks of semiconductor materials based on laser ultrasound according to any one of claims 1 to 3, characterized in that: The steps include: (1) The PC master controller first sends a control command to the ultrashort pulse laser control unit to control the ultrashort pulse laser to be incident on the spatial light modulator. The spatial light modulator receives the control command from the PC master controller, modulates and splits the ultrashort pulse laser and injects it into the focusing system. The PC master controller adjusts the focal length of the focusing system, and the focusing system injects the split light into a certain depth inside the ingot to be stripped to perform laser processing operations. (2) After the PC master controller sends a single ultrashort pulse laser emission command to the ultrashort pulse laser control unit, it delays for at least 100 μs and then sends a control command to the 1064 / 355 nm pulse laser control unit to emit a set number of times N. 2 The multi-pulse laser has the same parameters for each pulse laser emission; the pulse laser first passes through a polarization beam splitter, enters a photodetector as a trigger signal for the operation of a heterodyne interferometer vibrometer and an electronic scanning galvanometer, and enters a lens, and after the first reflector and the second reflector adjust the direction of the optical path, the pulse laser is incident on the surface of the ingot near the position of the ultrashort pulse light to excite ultrasonic waves; at the same time, the incident position of the pulse laser and the laser incident point position from the focusing system are controlled to be within a horizontal distance of 1 mm; (3) After receiving the trigger signal instruction from the pulse laser, the FPGA starts signal acquisition. After receiving the trigger signal, the electronic scanning galvanometer adjusts its position once. The PC master controller controls the electronic scanning galvanometer to adjust the position frequency to be consistent with the pulse laser repetition frequency. The number of times the electronic scanning galvanometer moves is consistent with the number of times the pulse laser is emitted. The relative position of the scanning area and the pulse laser and ultrashort pulse laser remains unchanged. Each time the pulse laser is emitted, the electronic scanning galvanometer moves its position once, and receives the measurement light from each point returned by the third reflector and the electronic scanning galvanometer into the heterodyne interferometer vibrometer. (4) The heterodyne interferometer vibrometer uses an internal photodetector to convert the interfering optical signal into a low-frequency electrical signal with the high frequency filtered out, and sends the electrical signal to the FPGA system for signal storage and demodulation. The demodulation includes down-mixing, inverse tangent demodulation, phase unwrapping and fast Fourier transform, and the output is the vibration signal of each position over time. In addition, the amplitude of each vibration signal at the same time is plotted to obtain a one-dimensional or two-dimensional ultrasonic propagation path diagram at different times. The display is used to display the vibration displacement diagram and the one-dimensional or two-dimensional ultrasonic propagation path diagram. (5) The crack size is obtained by calculating the vibration displacement through the corresponding function ∑f(v, t), or the crack size is obtained by image processing of the ultrasonic propagation path diagram; When it is detected that the size of the crack exceeds the set threshold, the crack feedback control system will send a feedback signal to the PC master controller, and the PC master controller sends an instruction to stop the ultrashort pulse laser emission or set the ultrashort pulse laser pulse width parameter to increase, the energy and repetition rate parameters to decrease, and sends a phase adjustment control instruction to the spatial light modulator to change the energy distribution of the ultrashort pulse scanning laser; if the PC master controller does not receive the feedback instruction, it waits for the 1064 / 355nm pulse laser emission count to stop, that is, after the ultrashort pulse laser control instruction is sent, it sets the timing, and after the timing ends and no feedback signal is received, the PC master controller sends a control instruction to the three-dimensional mobile platform. Every time the mobile platform adjusts its position, the absolute position of the area scanning the laser on the ingot changes, thereby realizing laser scanning of the set route during laser stripping. Repeating the above operations can perform real-time crack monitoring on the laser stripping of semiconductor materials.

5. The real-time online monitoring method for laser peeling cracks of semiconductor materials based on laser ultrasound according to claim 4 is characterized in that: In step (3), the initial position of the electronic scanning galvanometer is set at the lower left corner of the area to be measured. The specific movement method when adjusting the position is as follows: first move N times in the vertical direction, each time moving a preset step length S, then move right once in the horizontal direction, move a preset step length S, then move down N times in the vertical direction, move right once in the horizontal direction again, continue to move N times in the vertical direction, move right once in the horizontal direction, until a total of N times in the horizontal direction are moved, the entire scanning process is completed, and then move left N preset steps in the horizontal direction to return to the initial position.

6. The real-time online monitoring method for laser peeling cracks of semiconductor materials based on laser ultrasound according to claim 5 is characterized in that: In step (3), N is an even number.

7. The real-time online monitoring method for laser peeling cracks of semiconductor materials based on laser ultrasound according to claim 4 is characterized in that: In step (5), the crack size is obtained through function calculation. For a single defect material, the length, width or depth of the defect is linearly related to the sound wave arrival time t or the sound wave vibration amplitude v in the one-dimensional vibration displacement diagram after simulation calculation. The mathematical expression is L=k·v+b or L=k'·t+b', where L represents the length or width of the crack, k and k' are proportional coefficients, b and b' are constants, and the amplitude change rate between adjacent detection points is calculated. When the change rate exceeds the set threshold, the crack boundary is determined.

8. The real-time online monitoring method for laser peeling cracks of semiconductor materials based on laser ultrasound according to claim 4 is characterized in that: In step (5), the crack size is obtained using the ultrasonic wave propagation path diagram. When the ultrasonic wave propagation path diagram is scanB, the change of the acoustic wave amplitude at different positions over time is determined. When the ultrasonic wave propagation path diagram is scanC, the amplitude at each position at a certain moment is determined to generate a two-dimensional distribution diagram. The image processing step includes denoising, contrast enhancement, and canndy edge detection in FPGA, so as to calculate the length and width of the crack.

9. The real-time online monitoring method for laser peeling cracks of semiconductor materials based on laser ultrasound according to claim 4 is characterized in that: In step (5), the specific movement method of the three-dimensional mobile platform is as follows: first, it moves K1 times in the vertical direction, each time with a preset step length of l, then moves right once in the horizontal direction, moves a preset step length of l, then moves down K1 times in the vertical direction, moves right once in the horizontal direction again, continues to move K1 times in the vertical direction, and moves right once in the horizontal direction, until it moves K2 times in total in the horizontal direction; at this time, the scanning process of one layer of laser stripping is completed, and then it moves left K2 preset steps in the horizontal direction to return to the initial position, the ultrashort pulse laser scanning ingot stripping of the first layer is completed, and the displacement platform moves up one w, waiting to start the laser stripping scanning of the second layer.

10. The real-time online monitoring method for laser peeling cracks of semiconductor materials based on laser ultrasound according to claim 9, characterized in that: K2 is an even number.

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