CN120696575B - Method for stripping silicon carbide by using circulating ultrasonic medium assisted ultrasonic waves - Google Patents

Abstract

This invention discloses a method for ultrasonic exfoliation of silicon carbide using a circulating ultrasonic medium-assisted process, comprising the following steps: S1. A near-infrared femtosecond laser is compressed to the diffraction limit and focused at 300 μm inside a silicon carbide wafer. The laser is controlled to scan layer by layer to form a continuous brittle modified layer with a thickness of 100 μm inside the silicon carbide wafer. S2. A single-ring cut is made along the side of the silicon carbide wafer using an ultraviolet laser, penetrating the modified layer to a depth of 80 μm to 120 μm with a narrow slit, extending to a depth of 10 μm to 30 μm in the substrate, forming a narrow annular opening groove. S3. A miniature ultrasonic probe is embedded at an inclined angle into the bottom of the annular opening groove, and a suspension is injected to form a stable liquid film. An initial stage of ultrasonic crack initiation is performed, followed by an expansion stage where the crack is driven to propagate along the plane of the modified layer. S4. The separated silicon carbide sheet is adsorbed using a vacuum suction cup, and any remaining liquid film is removed. This invention can control crack path deviation, heat-affected zone range, and surface roughness to extremely low levels.

Description

Method for stripping silicon carbide by using circulating ultrasonic medium assisted ultrasonic waves

Technical Field

The invention relates to the technical field of third-generation semiconductor material precision machining, in particular to a method for stripping silicon carbide by using circulating ultrasonic medium assisted ultrasonic waves.

Background

In the flaking process of silicon carbide wafers, conventional laser modification processes present a significant risk of thermal damage. The prior art generally employs high energy density lasers, such as energy densities greater than 10 ⁸W/cm², to modify the full thickness of silicon carbide wafers to form internal crack or void layers. This high energy laser machining approach then inevitably creates microcracks on the wafer surface that may penetrate into the functional layer, leading to reduced device performance and even failure. Researches show that the density of microcracks on the surface of a silicon carbide wafer processed by the traditional laser can reach 125 strips/cm ², and the reliability and the electrical performance of the device are seriously affected. In addition, the laser thermal effect can also cause local material performance degradation, further limiting machining accuracy and quality.

For stripping of 300um grade ultrathin silicon carbide wafers, mechanical stripping is a common traditional method, and then the method relies on accurate matching of stress, so that wafer fracture is easily caused by uneven stress distribution in actual operation. Experimental data show that the cracking rate of mechanical stripping is as high as 38%, and the yield is less than 60%. Especially in the processing of large-size (6-8 inch) wafers, the instability problem of mechanical stripping is more remarkable, and the subsequent processing and performance of devices are further affected because the propagation direction and speed of cracks cannot be effectively controlled in the mechanical stripping process, so that the surface roughness of the stripped wafer is higher (Ra >2 μm).

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for stripping silicon carbide by using circulating ultrasonic medium in an auxiliary ultrasonic mode, wherein the crack path deviation, the heat affected zone range and the surface roughness can be controlled to be very low.

The invention is realized by the following technical scheme that the method for stripping silicon carbide by using circulating ultrasonic medium assisted ultrasonic waves comprises the following steps:

S1, combining an aspheric lens and a self-adaptive optical module to cooperatively focus, compressing near infrared femtosecond laser to a diffraction limit and focusing the near infrared femtosecond laser to 300um in a silicon carbide wafer, enabling a laser focus to be parallel to the surface of the silicon carbide wafer, controlling the laser to form a continuous brittle modified layer with the thickness of 100um in the silicon carbide wafer in a layer-by-layer scanning mode, and regulating and controlling the void ratio of the modified layer through an energy density gradient to generate a uniform micropore and crack network;

S2, sleeving a rubber sleeve on the periphery of the ultrasonic probe, starting ultrasonic, simultaneously starting a microfluidic system to inject suspension into the rubber sleeve, enabling the suspension to wrap the ultrasonic probe to form a stable liquid film, transmitting vibration energy through the liquid film, firstly carrying out ultrasonic crack initiation through an initial stage, then carrying out ultrasonic driving crack 360-degree expansion along the plane of the modified layer through an expansion stage, monitoring the expansion speed and path precision in real time, immediately stopping ultrasonic driving after an acoustic emission sensor captures a crack closing signal, and removing the ultrasonic probe together with the rubber sleeve;

s3, adsorbing the separated silicon carbide slices by using a vacuum chuck.

Further, before step S2 is executed, ultraviolet laser is utilized to conduct single-circle annular cutting along the side face of the silicon carbide wafer, a narrow slit of 15um to 30um penetrates through the position of the modified layer with the depth of 80um to 120um and extends to the position of the substrate with the depth of 10um to 30um, a narrow slit annular opening groove is formed, and then the miniature ultrasonic probe is embedded into the bottom of the annular opening groove at an inclined angle.

Further, when the step S2 is executed, a plurality of ultrasonic probes are circumferentially distributed on the modified layer, and the interval between every two adjacent ultrasonic probes is 10mm-100mm.

The near infrared femtosecond laser in the step S1 adopts a femtosecond fiber laser as a light source, wherein the wavelength range of the femtosecond fiber laser is 1000nm to 1100nm, the pulse width range is 300fs to 500fs, the repetition frequency range is 50kHz to 200kHz, and the diameter range of a focusing light spot is smaller than 5um;

The energy density gradually changes from 0.8J/cm ^z at the top to 1.2J/cm ^z at the bottom in the thickness direction of the modified layer, silicon carbide crystal lattice directional dissociation is induced, uniformly distributed micropores and nano crack grids are formed, the brittle structure of the modified layer is optimized, the thickness tolerance range of the modified layer is within +/-10%, and the parallelism deviation range of the plane of the modified layer and the main crystal plane of the wafer is less than or equal to 0.5 degrees.

The ultraviolet laser adopts an ultraviolet laser as a light source, the ultraviolet laser adopts a DPSS Q-switched laser light source, the working wavelength range of the ultraviolet laser is 300nm to 380nm, the pulse energy range of the ultraviolet laser is 1mJ to 3mJ, and the pulse width range of the ultraviolet laser is 10ns to 30ns;

When the ultraviolet laser performs single-circle annular cutting along the side face of the silicon carbide wafer, a coaxial vision positioning system is adopted to integrate a high-resolution CCD camera, the resolution range of the CCD camera is 3um to 10um, the CCD camera is combined with a dynamic compensation algorithm, the cutting position of the side face of the wafer is monitored in real time, the path deviation caused by wafer warping is corrected, and the concentricity error range of the annular opening groove is ensured to be less than or equal to 5um.

Further, the width of the annular open groove is controlled to be 10-35 um, and the cutting speed of the ultraviolet laser is in the range of 30-100 mm/s.

Further, the diameter range of the miniature ultrasonic probe is 40-60 um, the tip end of the miniature ultrasonic probe is integrated with a conical diffuser, the diffusion angle range of the conical diffuser is 50-70 degrees, and ultrasonic energy is directionally focused at the bottom of the annular open groove.

Further, the miniature ultrasonic probe is embedded into the bottom of the annular opening groove by adopting a six-axis robot at an angle of inclination ranging from 20 degrees to 40 degrees, and the embedding depth of the miniature ultrasonic probe is 70um to 100um.

Further, when the miniature ultrasonic probe is used for carrying out ultrasonic crack initiation in the initial stage, low-frequency continuous ultrasonic laser crack initiation with the frequency range of 50kHz to 60kHz and the power range of 2W to 4W is adopted;

When the ultrasonic driving crack is extended along the plane of the modified layer at 360 degrees in the extension stage, high-frequency pulse ultrasonic with the frequency range of 70kHz to 90kHz, the duty ratio range of 30 to 50 percent and the peak power range of 7 to 10W is adopted, and the pulse shock wave is utilized to accelerate the crack to extend along the plane of the modified layer at 360 degrees.

Further, when the ultrasonic probe is used for carrying out the initial stage ultrasonic crack initiation, the low-frequency continuous ultrasonic laser crack initiation with the frequency range of 50kHz to 60kHz and the power range of 20W to 40W is adopted;

when the ultrasonic driving crack is extended along the plane of the modified layer by 360 degrees in the extension stage, high-frequency pulse ultrasonic with the frequency range of 70kHz to 90kHz and the power range of 70W to 100W is adopted, and the crack is accelerated to be extended along the plane of the modified layer by 360 degrees by utilizing pulse shock waves.

Compared with the prior art, the invention has the following beneficial effects:

1. the near infrared femtosecond laser is utilized to construct the modified layer, the ultraviolet annular side cutting and the liquid guide ultrasonic collaborative expansion stripping are carried out, the non-hot melting modification technology is combined with the ultraviolet cutting technology with low thermal influence, the sheet yield is obviously improved, the fragmentation risk is reduced, the problems of surface damage and microcracks caused by high-energy laser and mechanical stress in the traditional technology are avoided, and the integrity of the functional layer of the device is ensured.

2. Based on the accurate positioning of the modified layer and the dynamic compensation of the ultraviolet cutting path, the stable expansion of cracks along a preset path is realized by combining a collaborative expansion mechanism of liquid guide ultrasonic, and the separation surface reaches high flatness and low roughness, thereby meeting the severe requirements of a power device on the surface quality of a substrate.

3. The automatic processing of the large-size silicon carbide wafer is supported, the efficiency is optimized through a three-axis linkage process, the processing period is obviously shortened, and the method is suitable for the large-scale production requirement of the high-performance semiconductor substrate in the fields of new energy automobiles, 5G communication and the like.

Drawings

FIG. 1 is a process flow diagram of a method of the present invention for circulating ultrasonic medium-assisted ultrasonic stripping of silicon carbide;

FIG. 2 is a side view of a liquid-wrapped ultrasound probe of the present invention;

FIG. 3 is a machined side view of a single ultrasonic probe of the present invention;

Fig. 4 is an ultrasound probe of the present invention when filled with liquid.

The reference numerals illustrate 1-silicon carbide wafer, 2-modified layer, 3-annular open slot, 4-liquid wrapped ultrasonic probe, 5-conical diffuser, 6-single ultrasonic probe, 7-suspension, 8-rubber sleeve.

Detailed Description

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

Example 1

In the embodiment, an n-type silicon carbide wafer with the thickness of 300um and the specification of 6 inches is selected, and the method for stripping silicon carbide by using the circulating ultrasonic medium assisted ultrasonic waves provided by the invention is adopted for flaking processing.

Referring to fig. 1 to 4, a method for stripping silicon carbide by using circulating ultrasonic medium assisted ultrasonic waves comprises the following specific steps:

S1, combining an aspheric lens and a self-adaptive optical module to cooperatively focus, compressing near infrared femtosecond laser to a diffraction limit and focusing the near infrared femtosecond laser to 300um in a silicon carbide wafer, enabling a laser focus to be parallel to the surface of the silicon carbide wafer, controlling the laser to form a continuous brittle modified layer with the thickness of 100um in the silicon carbide wafer in a layer-by-layer scanning mode, and regulating and controlling the void ratio of the modified layer through an energy density gradient to generate a uniform micropore and crack network.

S2, sleeving a rubber sleeve on the periphery of the ultrasonic probe, starting ultrasonic, simultaneously starting a microfluidic system to inject suspension into the rubber sleeve, enabling the suspension to wrap the ultrasonic probe to form a stable liquid film, transmitting vibration energy through the liquid film, performing ultrasonic crack initiation through an initial stage, performing ultrasonic driving crack propagation along the plane of the modified layer by 360 degrees through an expansion stage, monitoring the propagation speed and path precision in real time, immediately stopping ultrasonic driving after an acoustic emission sensor captures a crack closing signal, and removing the ultrasonic probe together with the rubber sleeve.

Before step S2 is executed, a single-ring annular cutting is performed along the side surface of the silicon carbide wafer by using ultraviolet laser, a narrow slit of 15um to 30um penetrates through the modified layer at a depth of 80um to 120um and extends to a substrate at a depth of 10um to 30um, a narrow slit annular opening groove is formed, and then a miniature ultrasonic probe is embedded into the bottom of the annular opening groove at an inclined angle.

S3, adsorbing the separated silicon carbide slices by using a vacuum chuck.

In step S1, as an alternative to this embodiment, a near infrared femtosecond laser is used, the wavelength of which is 1030nm, the pulse width is 400fs, the repetition frequency is 100kHz, the single pulse energy is 1.0uJ, the beam quality M ² is 1.2, the spot diameter is 4um, the laser energy density is graded from 0.8J/cm ^z at the top to 1.2J/cm ^z at the bottom in the modified layer thickness direction (Z axis direction), and the void fraction is regulated to 38%.

In the present example, the optical coherence tomography OCT verifies that the modified layer has a thickness tolerance of + -8%, a plane parallelism deviation of 0.3 DEG, a surface heat affected zone HAZ of 1.5um or less, and no microcracks penetrating through the functional layer.

The ultraviolet laser adopts an ultraviolet Q-switched laser, the wavelength of the ultraviolet Q-switched laser is 355nm, the pulse energy is 2mJ, the pulse width is 20ns, single-ring annular cutting is carried out at the speed of 50mm/s, the coaxial vision positioning system is adopted to dynamically compensate the wafer warpage at the resolution of 5um, the maximum compensation energy is 40um, an annular open slot with the width of 25um and the depth of 120um is formed, the ultraviolet Q-switched laser penetrates through the modified layer 100um and extends to the base material 20um, the width of a heat affected zone is 12um, and the residual stress release rate is 75%.

The micro ultrasonic probe with the diameter of 50um is controlled by a six-axis robot, the diffusion angle of the conical diffuser is 60 degrees, the conical diffuser is embedded into the depth of the bottom of the annular opening groove at an inclined angle of 30 degrees, meanwhile, the micro-fluidic system is injected into deionized water-based suspension liquid at the speed of 1.2uL/min to form an 8um thick liquid film, 50kHz continuous ultrasonic is used in the initial stage, 3W power laser crack initiation takes 1.2 seconds, 80kHz pulse ultrasonic is used in the expansion stage, the duty cycle is 40%, the peak power is 8W, the crack is driven to expand at the speed of 1.5mm/s along the plane of the modified layer at 360 degrees, the acoustic emission sensor captures 100kHz closed signals in real time, and the ultrasonic sensor is automatically terminated after the response time is 8 ms.

In the step S3, the roughness Ra of the separation surface is 45nm by a white light interferometer, and the scanning electron microscope SEM shows that no microcrack, namely edge collapse, is generated, and the electrical performance qualification rate of the device reaches 98.5%.

The embodiment realizes the indexes of 92% yield, heat affected zone less than or equal to 1.5um and crack path deviation less than or equal to 10um, is obviously superior to the traditional process, and verifies the technical advantages of the invention in the aspects of inhibiting heat damage, improving surface quality and controlling an expansion path.

The method realizes high-precision nondestructive separation of the silicon carbide thin sheet through a three-section type cooperative process chain, builds a non-hot-melt brittle modified layer inside the silicon carbide wafer by near infrared femtosecond laser, forms a pore-controllable microcrack network by ultra-short pulse and self-adaptive optical focusing technology, breaks through the heat accumulation defect of the traditional high-energy laser, avoids the damage of a surface functional layer, secondly, utilizes the short wavelength characteristic of ultraviolet laser to implement annular side cutting, forms a narrow-slit annular open slot by processing with low thermal influence, precisely releases residual stress and builds a crack directional expansion boundary, obviously reduces the failure risk of a thermally induced structure compared with the traditional infrared laser technology, and finally, introduces a liquid-wrapped miniature ultrasonic probe, drives cracks to uniformly expand along the plane of the modified layer by liquid film lubrication and ultrasonic energy dynamic regulation and control, and thoroughly solves the problems of random bifurcation and edge collapse caused by stress concentration in traditional mechanical stripping by combining the acoustic emission real-time monitoring technology.

Example two

S1, combining an aspheric lens and a self-adaptive optical module to cooperatively focus, compressing near infrared femtosecond laser to a diffraction limit and focusing the near infrared femtosecond laser to 300um in a silicon carbide wafer, enabling a laser focus to be parallel to the surface of the silicon carbide wafer, controlling the laser to form a continuous brittle modified layer with the thickness of 100um in the silicon carbide wafer in a layer-by-layer scanning mode, and regulating and controlling the void ratio of the modified layer through an energy density gradient to generate a uniform micropore and crack network.

S2, sleeving a rubber sleeve on the periphery of the ultrasonic probe, starting ultrasonic, simultaneously starting a microfluidic system to inject suspension into the rubber sleeve, enabling the suspension to wrap the ultrasonic probe to form a stable liquid film, transmitting vibration energy through the liquid film, performing ultrasonic crack initiation through an initial stage, performing ultrasonic driving crack propagation along the plane of the modified layer by 360 degrees through an expansion stage, monitoring the propagation speed and path precision in real time, immediately stopping ultrasonic driving after an acoustic emission sensor captures a crack closing signal, and removing the ultrasonic probe together with the rubber sleeve.

And (2) when the ultrasonic is started in the step (S2), a plurality of ultrasonic probes are circumferentially distributed on the modified layer, and the distance between every two adjacent ultrasonic probes is 10mm-100mm.

S3, adsorbing the separated silicon carbide slices by using a vacuum chuck.

In step S1, as an alternative to this embodiment, a near infrared femtosecond laser is used, the wavelength of which is 1030nm, the pulse width is 400fs, the repetition frequency is 100kHz, the single pulse energy is 1.0uJ, the beam quality M ² is 1.2, the spot diameter is 4um, the laser energy density is graded from 0.8J/cm ^z at the top to 1.2J/cm ^z at the bottom in the modified layer thickness direction (Z axis direction), and the void fraction is regulated to 38%.

In the present example, the optical coherence tomography OCT verifies that the modified layer has a thickness tolerance of + -8%, a plane parallelism deviation of 0.3 DEG, a surface heat affected zone HAZ of 1.5um or less, and no microcracks penetrating through the functional layer.

The pulse width of the ultrasonic probe is 200ps, the speed is 100-500mm/s, the pulse energy is 5uJ, and when the ultrasonic probe is used for carrying out initial stage ultrasonic crack initiation, the ultrasonic probe is used for carrying out low-frequency continuous ultrasonic laser crack initiation, the frequency range is 50kHz to 60kHz, and the power range is 20W to 40W;

when the ultrasonic driving crack is extended along the plane of the modified layer by 360 degrees in the extension stage, high-frequency pulse ultrasonic with the frequency range of 70kHz to 90kHz and the power range of 70W to 100W is adopted, and the crack is accelerated to be extended along the plane of the modified layer by 360 degrees by utilizing pulse shock waves.

According to the embodiment, the non-hot-melt brittle modified layer is built in the wafer through the near-infrared femtosecond laser, a micro-crack network with controllable gaps is formed through the ultra-short pulse and the self-adaptive optical focusing technology, the defect of heat accumulation of the traditional high-energy laser is overcome, the functional damage is avoided, the ultrasonic probe wrapped by liquid is utilized, the cracks are driven to uniformly spread along the plane of the modified layer through liquid film lubrication and ultrasonic energy dynamic adjustment, and stripping can be performed under the condition that slotting is not needed.

The suspension according to the invention may be pure water, pure oil, ethanol, or a mixture of pure water and starch, metal powder or non-metal powder, or a mixture of pure oil and starch, metal powder or non-metal powder, or a mixture of ethanol and starch, metal powder or non-metal powder.

Comparative example one

The preparation method of the reference example is characterized in that the conventional high-energy laser modification combined with mechanical stripping technology is adopted to treat an n-type silicon carbide wafer with the thickness of 300 mu mn and the specification of 6 inches. YAG solid laser is used for full thickness modification processing, the laser wavelength is 1064 nm, the pulse width is 100ns, the energy density is set to be 1X 10 ⁸ W/cm < 2 >, and a pore layer is formed inside a wafer through high-energy laser. The detection result shows that the laser processing leads to the surface heat affected zone width reaching 50 mu m, penetrating microcracks appear below the functional layer, the density reaches 110 strips/cm < 2 >, and the insulating performance of the device is seriously damaged. The sheet was then separated directly by applying 200N tension in the vertical direction via a vacuum chuck using a mechanical peel process. In the peeling process, large-area fragmentation occurs in the edge area of the sheet due to uneven stress distribution, and statistics shows that the fragmentation rate reaches 42%, and the final yield is only 58%. The morphology of the separation surface is observed by a scanning electron microscope, the surface roughness Ra is up to 2.3 mu m, the maximum length of the edge collapse defect is up to 500 mu m, and the local area of the device gate oxide layer is broken due to stress concentration. The electrical performance test shows that the leakage current of the device is increased by 10 times compared with the embodiment due to the penetration of microcracks and surface damage, and the threshold voltage drift exceeds 15%. Defect analysis shows that the heat accumulation effect of high-energy laser causes amorphous transformation of silicon carbide crystal lattice, the brittle structure of modified layer is uneven, cracks randomly branch and spread during mechanical stripping, and meanwhile, the stress guiding mechanism is absent, and the thin sheet bears asymmetric load in the separation process, so that uncontrollable fracture is finally initiated. This comparative example demonstrates the fundamental shortcomings of the conventional process in thermal damage control, stress matching, and extended path planning.

Comparative example two

The preparation method of the reference example is characterized in that an n-type silicon carbide wafer with the thickness of 300 mu mn and the specification of 6 inches is processed by adopting an infrared laser lateral cutting and liquid film-free ultrasonic expansion process. Firstly, a CO ₂ laser is adopted for side cutting processing, the laser wavelength is 10.6 mu m, the average power is 50W, the pulse width is 200ns, and the annular open groove with the width of 50 mu m is formed by cutting at the speed of 30 mm/s. The infrared laser heat effect is obvious, the width of a heat affected zone of a cutting area reaches 80 mu m, the local temperature of the edge of a groove exceeds 1800 ℃ to induce graphitization of silicon carbide, the brittle structure of the modified layer is damaged, and the residual stress release rate is less than 40%. Then a single ultrasonic probe (with the diameter of 60 mu m and no conical diffuser) is directly inserted into the tank bottom, 60 kHz continuous ultrasonic vibration is applied, the power is 10W, the crack propagation resistance is increased due to lack of liquid film lubrication and energy directional transmission, the initial cracking time is prolonged to 5 seconds, and the expansion speed fluctuation range is 0.2-3mm/s. The acoustic emission sensor detects a crack closure signal with a response time exceeding 50ms, resulting in crack overdrowing to a substrate depth of 30 μm and path deviations of up to 50 μm. After peeling, the edge of the sheet is broken and missing at multiple positions, the maximum length is 200 mu m, a scanning electron microscope shows that a thermal microcrack network exists on a separation surface, the density is 75 strips/cm < 2 >, and the surface roughness Ra=1.8 mu m. The electrical performance test shows that the leakage current of the device is increased by 6 times compared with the embodiment, and the threshold voltage is shifted by 12%. Defect analysis shows that the high heat input of infrared laser results in lattice reconstruction failure of the modified layer, weakens crack guiding effect, has no reduction of ultrasonic energy transfer efficiency caused by liquid film cooling and lubrication, and local temperature rise induces secondary thermal stress to aggravate crack propagation instability. The final yield is only 65%, and the negative influence of the heat damage defect and the liquid film deletion of the infrared laser technology on the ultrasonic expansion mechanism is verified.

The foregoing detailed description is directed to embodiments of the invention which are not intended to limit the scope of the invention, but rather to cover all modifications and variations within the scope of the invention.

Claims (8)

1. A method for stripping silicon carbide by using circulating ultrasonic medium assisted ultrasonic wave is characterized by comprising the following steps:

S1, combining an aspheric lens and a self-adaptive optical module to cooperatively focus, compressing near infrared femtosecond laser to a diffraction limit and focusing the near infrared femtosecond laser to 300um in a silicon carbide wafer, enabling a laser focus to be parallel to the surface of the silicon carbide wafer, controlling the laser to form a continuous brittle modified layer with the thickness of 100um in the silicon carbide wafer in a layer-by-layer scanning mode, and regulating and controlling the void ratio of the modified layer through an energy density gradient to generate a uniform micropore and crack network;

S2, performing single-circle annular cutting along the side surface of the silicon carbide wafer by utilizing ultraviolet laser, penetrating the modified layer by a narrow slit of 15um to 30um to a depth of 80um to 120um, extending to a substrate depth of 10um to 30um to form a narrow slit annular opening groove, embedding a miniature ultrasonic probe into the bottom of the annular opening groove at an inclined angle, sleeving a rubber sleeve on the periphery of the ultrasonic probe, starting ultrasonic, simultaneously starting a microfluidic system to inject suspension liquid into the rubber sleeve, enabling the suspension liquid to wrap the ultrasonic probe to form a stable liquid film, transmitting vibration energy through the liquid film, performing ultrasonic crack initiation through an initial stage, performing ultrasonic driving crack propagation along the plane of the modified layer by 360 degrees through an expansion stage, monitoring propagation speed and path precision in real time, immediately stopping ultrasonic driving after an acoustic emission sensor captures a crack closing signal, and removing the ultrasonic probe together with the rubber sleeve;

S3, adsorbing the separated silicon carbide slices by using a vacuum chuck;

The ultraviolet laser adopts an ultraviolet laser as a light source, the ultraviolet laser adopts a DPSS Q-switched laser light source, the working wavelength range of the ultraviolet laser is 300nm to 380nm, the pulse energy range of the ultraviolet laser is 1mJ to 3mJ, and the pulse width range of the ultraviolet laser is 10ns to 30ns;

When the ultraviolet laser performs single-circle annular cutting along the side face of the silicon carbide wafer, a coaxial vision positioning system is adopted to integrate a high-resolution CCD camera, the resolution range of the CCD camera is 3um to 10um, the CCD camera is combined with a dynamic compensation algorithm, the cutting position of the side face of the wafer is monitored in real time, the path deviation caused by wafer warping is corrected, and the concentricity error range of the annular opening groove is ensured to be less than or equal to 5um.

2. The method for ultrasonic-assisted stripping of silicon carbide by circulating ultrasonic medium according to claim 1, characterized in that in step S2, a plurality of ultrasonic probes are circumferentially distributed on the modified layer, and the interval between every two adjacent ultrasonic probes is 10mm-100mm.

3. The method for ultrasonic-assisted stripping of silicon carbide by circulating ultrasonic medium according to claim 1, wherein the near infrared femtosecond laser in the step S1 adopts a femtosecond fiber laser as a light source, wherein the wavelength range of the femtosecond fiber laser is 1000nm to 1100nm, the pulse width range is 300fs to 500fs, the repetition frequency range is 50kHz to 200kHz, and the diameter range of a focused light spot is less than 5um;

The energy density gradually changes from 0.8J/cm ^z at the top to 1.2J/cm ^z at the bottom in the thickness direction of the modified layer, silicon carbide crystal lattice directional dissociation is induced, uniformly distributed micropores and nano crack grids are formed, the brittle structure of the modified layer is optimized, the thickness tolerance range of the modified layer is within +/-10%, and the parallelism deviation range of the plane of the modified layer and the main crystal plane of the wafer is less than or equal to 0.5 degrees.

4. The method for ultrasonic-assisted stripping of silicon carbide by circulating ultrasonic media according to claim 1, wherein the width of the annular open groove is controlled to be 10-35 um, and the cutting speed of the ultraviolet laser is in the range of 30-100 mm/s.

5. The method for ultrasonic stripping silicon carbide assisted by circulating ultrasonic media according to claim 1, wherein the diameter of the miniature ultrasonic probe ranges from 40um to 60um, the tip of the miniature ultrasonic probe is integrated with a conical diffuser, the diffusion angle of the conical diffuser ranges from 50 degrees to 70 degrees, and ultrasonic energy is directionally focused at the bottom of the annular open groove.

6. The method for ultrasonic-assisted stripping of silicon carbide by circulating ultrasonic media according to claim 1, wherein the miniature ultrasonic probe is embedded into the bottom of the annular opening groove by adopting a six-axis robot at an angle of inclination ranging from 20 degrees to 40 degrees, and the embedding depth of the miniature ultrasonic probe is 70um to 100um.

7. The method for ultrasonic-assisted peeling of silicon carbide by using a circulating ultrasonic medium according to claim 1, wherein when the ultrasonic crack initiation at the initial stage is carried out by using the miniature ultrasonic probe, the crack initiation is carried out by using a low-frequency continuous ultrasonic laser with the frequency ranging from 50kHz to 60kHz and the power ranging from 2W to 4W;

When the ultrasonic driving crack is extended along the plane of the modified layer at 360 degrees in the extension stage, high-frequency pulse ultrasonic with the frequency range of 70kHz to 90kHz, the duty ratio range of 30 to 50 percent and the peak power range of 7 to 10W is adopted, and the pulse shock wave is utilized to accelerate the crack to extend along the plane of the modified layer at 360 degrees.

8. The method for ultrasonic-assisted peeling of silicon carbide by using a circulating ultrasonic medium according to claim 2, wherein when the ultrasonic probe is used for initial ultrasonic crack initiation, a low-frequency continuous ultrasonic laser crack initiation with a frequency range of 50kHz to 60kHz and a power range of 20W to 40W is adopted;

when the ultrasonic driving crack is extended along the plane of the modified layer by 360 degrees in the extension stage, high-frequency pulse ultrasonic with the frequency range of 70kHz to 90kHz and the power range of 70W to 100W is adopted, and the crack is accelerated to be extended along the plane of the modified layer by 360 degrees by utilizing pulse shock waves.