Laser slicing method and device for silicon carbide ingot

Abstract

The present invention provides a laser slicing method and apparatus for silicon carbide ingots. The laser slicing method first focuses an ultrashort pulse laser beam at a set depth layer of the silicon carbide ingot, generates a cavity-modification formation region and a crack-modification formation region above the set depth layer, and scans to form the cavity-modification layer and the crack-modification layer. The focus of the short pulse laser beam is then moved a certain distance above the set depth layer, allowing the short pulse laser beam to pass through the crack-modification formation region and then focus on the cavity-modification formation region, where it scatters and propagates, causing cracks within the crack-modification formation region to grow laterally outward. The laser scans the cavity-modification layer so that cracks within any adjacent cavity-modification formation regions are connected by lateral growth. This method reduces the amount and length of cracks in the modified layer extending longitudinally along the silicon carbide ingot, increases the number and length of lateral crack growth, reduces cutting loss, and reduces waste.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide ingots, and in particular to a laser slicing method and a device for silicon carbide ingots. Background Art

[0002] Among third-generation semiconductor materials, SiC (silicon carbide) features a wide bandgap, high breakdown electric field, high saturated electron drift velocity, and high thermal conductivity. It can be used in high-voltage environments exceeding 1200 volts, offering significant advantages in harsh environments. SiC substrate processing technology is a crucial foundation for device fabrication, and the quality and precision of its surface processing directly impact the quality of epitaxial thin films and the performance of its devices. Therefore, its applications require wafer surfaces to be ultra-smooth, defect-free, and damage-free, with surface roughness values reaching below the nanometer level.

[0003] However, SiC wafer processing is extremely difficult due to its high hardness, brittleness, excellent wear resistance, and extremely stable chemical properties. Ultra-precision machining of SiC single wafers involves the following steps: directional cutting, grinding (rough grinding and fine grinding), polishing (mechanical polishing), and ultra-precision polishing (chemical mechanical polishing).

[0004] Traditionally, sawing involves slicing SiC ingots along a specific orientation into thin wafers. Slicing SiC ingots into wafers with minimal warpage, uniform thickness, and low shear loss is crucial for subsequent grinding and polishing. Compared to traditional internal and external sawing, multi-wire sawing offers advantages such as high cutting speed, high machining precision, high efficiency, and a long lifespan, making it widely used for efficient wafer cutting. The multi-wire sawing process slices the ingot along a specific crystal orientation into flat, uniformly thick wafers no thicker than 1 mm, facilitating subsequent grinding. The basic principle is that a high-quality steel wire moves back and forth at high speed across the ingot surface. Diamond particles in the cutting fluid attached to the wire create intense friction against the ingot, causing the material to break and fall off the substrate, achieving the desired cutting effect. However, the disadvantage is high cutting wear. Due to the extreme hardness of silicon carbide, sawing it is challenging and subject to significant wear. The high cost and complex machining process contribute to the high cost of silicon carbide substrates, limiting their widespread application. In addition, the larger the chip size, the more difficult the corresponding crystal growth and processing technology is, while the manufacturing efficiency of downstream devices is higher and the unit cost is lower.

[0005] There is a technology in the prior art that uses lasers to cut silicon ingots. However, on the one hand, compared with silicon ingots, silicon carbide ingots are more hard, more brittle, more wear-resistant, and have extremely stable chemical properties. The existing laser cutting process cannot cut very thin wafers from silicon carbide ingots. On the other hand, in the existing laser cutting process of silicon ingots, laser modification is first used to form a modified layer at a certain thickness in the silicon ingot, and then the laser is used to heat the modified layer to make the cracks in the modified layer grow and spread, and then peeling is performed. In this process, the modified layer formed by laser modification is relatively thick. When the laser is subsequently used to heat the modified layer, the laser focus is focused on the modified layer. The height difference of the laser focus fluctuates greatly, and the focusing position of the laser focus is not well designed, causing the cracks in the modified layer to extend longer and more along the longitudinal direction of the silicon ingot, resulting in a large amount of cutting loss and a large amount of waste. Summary of the Invention

[0006] The present invention provides a laser slicing method and device for silicon carbide ingots, which reduces the amount and length of cracks in the modified layer extending longitudinally along the silicon carbide ingot, increases the number and length of transverse crack growth, reduces cutting loss thickness, and reduces waste.

[0007] In a first aspect, the present invention provides a laser slicing method for a silicon carbide ingot, the laser slicing method comprising:

[0008] Focusing the ultrashort pulse laser beam at a set depth layer position of the silicon carbide ingot to be cut, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position, respectively; wherein the cavity modification forming region is located between the set depth layer position and the crack modification forming region;

[0009] Controlling the focus of an ultrashort pulse laser beam to scan a set depth layer of the silicon carbide ingot to form a cavity modified layer and a crack modified layer above the set depth layer, respectively; wherein the cavity modified layer is composed of a plurality of cavity modified forming regions, the crack modified layer is composed of a plurality of crack modified forming regions, and the cavity modified layer is located between the set depth layer and the crack modified layer;

[0010] After passing through the crack modification area, the short pulse laser beam is focused on the cavity modification area and scattered in the cavity modification area, causing the cracks in the cavity modification area to grow laterally outward.

[0011] Controlling the focus of the short pulse laser beam to scan the void modified layer so that cracks in any adjacent void modified areas in the void modified layer are connected together by lateral growth;

[0012] A portion of the silicon carbide ingot is peeled off with the void modified layer as the interface to produce a silicon carbide wafer.

[0013] In the above-described scheme, an ultrashort pulse laser is first used to focus the ultrashort pulse laser beam at a predetermined depth level of the silicon carbide ingot, thereby generating a cavity-forming region and a crack-forming region above the predetermined depth level. The focus of the ultrashort pulse laser beam is then controlled to scan across the predetermined depth level of the silicon carbide ingot to form the cavity-forming layer and the crack-forming region. After the ultrashort pulse laser stealth cutting process, a short pulse laser with a slightly wider pulse width is used to move the focus of the short pulse laser beam to a position above the predetermined depth level by a certain range. After the short pulse laser beam passes through the crack-forming region, it is focused on the cavity-forming region and scattered and propagates within the cavity-forming region. This allows the heat of the short pulse laser beam to act primarily on the cavity-forming region, causing cracks within the crack-forming region to grow laterally outward. The focus of the short pulse laser beam is then controlled to scan across the cavity-forming layer, so that cracks within any adjacent cavity-forming regions within the cavity-forming layer are connected by lateral growth.

[0014] Compared to existing laser-cutting silicon ingot processes, the ultrashort-pulse laser employed in this process can generate a void-modification region and a crack-modification region above the predetermined depth layer at the focal point of the ultrashort-pulse laser beam. Through scanning, these regions form a void-modification layer and a crack-modification layer, respectively, further refining and differentiating the modified layers used in existing techniques. Subsequently, when a short-pulse laser beam is employed, the short-pulse laser beam is focused on the void-modification region. The short-pulse laser beam's focal point is positioned above the ultrashort-pulse laser beam's focal point, rather than at the same depth as in existing techniques. This allows the short-pulse laser beam to penetrate the crack-modification region and then focus on the void-modification region. The short-pulse laser beam then scatters and propagates within the void-modification region, causing cracks within the void-modification region to grow laterally outward. Furthermore, through scanning, cracks within any adjacent void-modification regions within the void-modification layer are connected through lateral growth. Moreover, in the process of the short pulse laser beam passing through the crack modification forming area and focusing on the void modification forming area to heat the void modification forming area, since the crack modification forming area can block the growth of the crack, the length of the upward growth of the crack in the void modification forming area can be limited to the interval below the crack modification forming area, and the length of the longitudinal growth of the crack can be limited to a smaller height range, which is convenient for improving the efficiency of crack extension, while also minimizing the extent of longitudinal extension of the crack and minimizing the amount of slice loss. That is, by subdividing the modified layer into the void modification layer and the crack modification layer, and then focusing the short pulse laser beam on the void modification layer, the focus position of the short pulse laser beam is more accurately and reasonably designed, not only making the upper and lower height difference of the focus of the short pulse laser beam fluctuate less (because the upper and lower height difference of the void modification forming area must be smaller than the upper and lower height difference of the modified layer composed of the crack modification forming area and the void modification forming area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the void modification layer, through the crack modification layer thereon. The formation area blocks the vertical upward growth of cracks in the void modification formation area, limits the length of the vertical growth of the cracks to a smaller height range, optimizes the focusing position of the short pulse laser beam, reduces the amount and length of the cracks in the modified layer extending longitudinally along the silicon carbide ingot, and thus applies more laser energy to the lateral outward growth of the cracks, which can increase the number and length of lateral crack growth, can cut thinner silicon carbide wafers, and also reduce the cutting loss thickness. More silicon carbide wafers can be cut from the same silicon carbide ingot, reducing waste.

[0015] In a specific embodiment, the ultrashort pulse laser beam is a sub-picosecond pulse width laser beam, a picosecond pulse width laser beam or a femtosecond pulse width laser beam, which facilitates the generation of a better void modification forming area and a crack modification forming area above the focus of the ultrashort pulse laser beam.

[0016] In a specific embodiment, the pulse width of the ultrashort pulse laser beam is 243fs-900fs, and the wavelength of the ultrashort pulse laser beam is 500-1100nm, which further improves the modification effect of the cavity modification forming area and the crack modification forming area generated above the focus of the ultrashort pulse laser beam.

[0017] In a specific embodiment, the short pulse laser beam is a sub-nanosecond laser beam, which increases the number and length of lateral crack growth.

[0018] In a specific embodiment, the pulse width of the short pulse laser beam is 500ps-1ns, and the wavelength of the short pulse laser beam is 500-1100nm, which is convenient for better reducing the amount and length of cracks in the modified layer extending longitudinally along the silicon carbide ingot, thereby applying more laser energy to the lateral outward growth of the cracks, increasing the number of lateral crack growth and the length of crack growth.

[0019] In a specific embodiment, the focusing point of the short pulse laser beam is 1-4.5 μm higher than the focusing point of the ultrashort pulse laser beam, thereby better optimizing the focusing position of the short pulse laser beam.

[0020] In a specific embodiment, after a short pulse laser beam passes through the crack modification forming area, it is focused on the void modification forming area and scattered and propagated in the void modification forming area, so that the cracks in the void modification forming area grow laterally outward, including: adjusting the polarization state of the short pulse laser beam so that the electron propagation direction expands along the silicon carbide lattice direction of the silicon carbide ingot, forming a 3-5° laterally growing crack, so as to better reduce the amount and length of the cracks in the modified layer along the longitudinal expansion of the silicon carbide ingot, thereby applying more laser energy to the lateral outward growth of the cracks, increasing the number of lateral crack growths and the crack growth length.

[0021] In one specific embodiment, controlling the focus of an ultrashort pulse laser beam to scan a set depth layer of a silicon carbide ingot includes: controlling the focus of the ultrashort pulse laser beam to scan a plurality of parallel first cutting paths at the set depth layer of the silicon carbide ingot, wherein the interval between any two adjacent first cutting paths is 10-25 μm. Controlling the focus of a short pulse laser beam to scan a void-modified layer includes: controlling the focus of the short pulse laser beam to scan a plurality of parallel second cutting paths at the void-modified layer, wherein each second cutting path is directly above a first cutting path, thereby facilitating setting an appropriate width of the silicon carbide explosion point interval and simplifying the scanning difficulty.

[0022] In a specific embodiment, controlling the focus of a short pulse laser beam to scan a plurality of parallel second cutting paths in the void modification layer includes: controlling the focus of the short pulse laser beam to scan at each second cutting path for a number of times greater than or equal to three times, achieving connection of burst point cracks by using a short pulse laser beam for multiple processing and continuous heat injection, increasing the amount and length of lateral crack growth in the crack modification formation area, and making the cracks extending from adjacent second cutting paths connect together faster, thereby facilitating the separation of the silicon carbide ingot into multiple silicon carbide wafers through implicit crack induction growth.

[0023] In a second aspect, the present invention further provides a laser slicing device for silicon carbide ingots, the laser slicing device comprising: a stage, an ultrashort pulse laser system, a first scanning system, a short pulse laser system, a second scanning system, and a separation system. The stage is used to hold the silicon carbide ingot to be cut thereon. The ultrashort pulse laser system is used to provide an ultrashort pulse laser beam and focus the ultrashort pulse laser beam at a set depth layer position of the silicon carbide ingot to be cut, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position, respectively; wherein the cavity modification forming region is located between the set depth layer position and the crack modification forming region. The first scanning system is used to control the focus of the ultrashort pulse laser beam to scan the set depth layer of the silicon carbide ingot, so as to form a cavity modification layer and a crack modification layer above the set depth layer, respectively; wherein the cavity modification layer is composed of multiple cavity modification formation regions, and the crack modification layer is composed of multiple crack modification formation regions, and the cavity modification layer is located between the set depth layer and the crack modification layer. The short pulse laser system is used to provide a short pulse laser beam. The short pulse laser system is also used to focus the short pulse laser beam on the cavity modification formation region after passing it through the crack modification formation region, and scatter and propagate in the cavity modification formation region, so that the cracks in the cavity modification formation region grow laterally outward. The second scanning system is used to control the focus of the short pulse laser beam to scan the cavity modification layer, so that the cracks in any adjacent cavity modification formation regions in the cavity modification layer are connected together through lateral growth. The separation system is used to peel off a portion of the silicon carbide ingot using the cavity modification layer as the interface to produce a silicon carbide wafer.

[0024] In the above-described scheme, an ultrashort pulse laser is first used to focus the ultrashort pulse laser beam at a predetermined depth level of the silicon carbide ingot, thereby generating a cavity-forming region and a crack-forming region above the predetermined depth level. The focus of the ultrashort pulse laser beam is then controlled to scan across the predetermined depth level of the silicon carbide ingot to form the cavity-forming layer and the crack-forming region. After the ultrashort pulse laser stealth cutting process, a short pulse laser with a slightly wider pulse width is used to move the focus of the short pulse laser beam to a position above the predetermined depth level by a certain range. After the short pulse laser beam passes through the crack-forming region, it is focused on the cavity-forming region and scattered and propagates within the cavity-forming region. This allows the heat of the short pulse laser beam to act primarily on the cavity-forming region, causing cracks within the crack-forming region to grow laterally outward. The focus of the short pulse laser beam is then controlled to scan across the cavity-forming layer, so that cracks within any adjacent cavity-forming regions within the cavity-forming layer are connected by lateral growth.

[0025] Compared to existing laser-cutting silicon ingot processes, the ultrashort-pulse laser employed in this process can generate a void-modification region and a crack-modification region above the predetermined depth layer at the focal point of the ultrashort-pulse laser beam. Through scanning, these regions form a void-modification layer and a crack-modification layer, respectively, further refining and differentiating the modified layers used in existing techniques. Subsequently, when a short-pulse laser beam is employed, the short-pulse laser beam is focused on the void-modification region. The short-pulse laser beam's focal point is positioned above the ultrashort-pulse laser beam's focal point, rather than at the same depth as in existing techniques. This allows the short-pulse laser beam to penetrate the crack-modification region and then focus on the void-modification region. The short-pulse laser beam then scatters and propagates within the void-modification region, causing cracks within the void-modification region to grow laterally outward. Furthermore, through scanning, cracks within any adjacent void-modification regions within the void-modification layer are connected through lateral growth. Moreover, in the process of the short pulse laser beam passing through the crack modification forming area and focusing on the void modification forming area to heat the void modification forming area, since the crack modification forming area can block the growth of the crack, the length of the upward growth of the crack in the void modification forming area can be limited to the interval below the crack modification forming area, and the length of the longitudinal growth of the crack can be limited to a smaller height range, which is convenient for improving the efficiency of crack extension, while also minimizing the extent of longitudinal extension of the crack and minimizing the amount of slice loss. That is, by subdividing the modified layer into the void modification layer and the crack modification layer, and then focusing the short pulse laser beam on the void modification layer, the focus position of the short pulse laser beam is more accurately and reasonably designed, not only making the upper and lower height difference of the focus of the short pulse laser beam fluctuate less (because the upper and lower height difference of the void modification forming area must be smaller than the upper and lower height difference of the modified layer composed of the crack modification forming area and the void modification forming area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the void modification layer, through the crack modification layer thereon. The formation area blocks the vertical upward growth of cracks in the void modification formation area, limits the length of the vertical growth of the cracks to a smaller height range, optimizes the focusing position of the short pulse laser beam, reduces the amount and length of the cracks in the modified layer extending longitudinally along the silicon carbide ingot, and thus applies more laser energy to the lateral outward growth of the cracks, which can increase the number and length of lateral crack growth, can cut thinner silicon carbide wafers, and also reduce the cutting loss thickness. More silicon carbide wafers can be cut from the same silicon carbide ingot, reducing waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A flow chart of a laser slicing method for a silicon carbide ingot provided in an embodiment of the present invention;

[0027] Figures 2 to 7The present invention provides a schematic cross-sectional view of the various steps of a laser slicing method for a silicon carbide ingot, wherein: Figure 3 This is an actual sample image of a cavity-forming region and a crack-forming region processed by an ultrashort pulse laser beam according to an embodiment of the present invention. Figure 6 A schematic diagram of the laser scattering effect when a short-pulse laser beam provided by an embodiment of the present invention acts on a cavity modification and formation region;

[0028] Figure 8 A schematic structural diagram of a laser slicing device for silicon carbide ingots provided in an embodiment of the present invention;

[0029] Figure 9 Based on Figure 8 A flow chart of a method for laser slicing a silicon carbide ingot and a laser slicing device for silicon carbide ingots is provided.

[0030] Reference numerals:

[0031] 10-Silicon carbide ingot 21-Set depth layer 22-Void modified layer 23-Crack modified layer DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] To facilitate understanding of the laser slicing method for silicon carbide ingots provided in an embodiment of the present invention, the following first describes an application scenario of the laser slicing method provided in an embodiment of the present invention. This laser slicing method is applied to the process of separating silicon carbide wafers from a silicon carbide ingot. The following describes the laser slicing method for silicon carbide ingots in detail with reference to the accompanying drawings.

[0034] refer to Figures 1 to 7 The laser slicing method of a silicon carbide ingot provided in an embodiment of the present invention includes:

[0035] Step 10: Focusing the ultrashort pulse laser beam at a predetermined depth layer 21 of the silicon carbide ingot 10 to be cut, thereby generating a cavity modification forming region and a crack modification forming region above the predetermined depth layer 21; wherein the cavity modification forming region is located between the predetermined depth layer 21 and the crack modification forming region;

[0036] Step 20: Controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide ingot 10 to form a cavity modified layer 22 and a crack modified layer 23 above the set depth layer 21, respectively; wherein the cavity modified layer 22 is composed of a plurality of cavity modified forming regions, and the crack modified layer 23 is composed of a plurality of crack modified forming regions, and the cavity modified layer 22 is located between the set depth layer 21 and the crack modified layer 23;

[0037] Step 30: After passing through the crack modification area, the short pulse laser beam is focused on the cavity modification area and scattered in the cavity modification area, causing the cracks in the cavity modification area to grow laterally outward.

[0038] Step 40: Control the focus of the short pulse laser beam to scan the void modified layer 22 so that cracks in any adjacent void modified areas in the void modified layer 22 are connected together by lateral growth;

[0039] Step 50: Using the void modified layer 22 as an interface, a portion of the silicon carbide ingot 10 is peeled off to generate a silicon carbide wafer.

[0040] In the above scheme, an ultrashort pulse laser is first used to focus the ultrashort pulse laser beam on the set depth layer 21 position of the silicon carbide ingot 10 to generate a cavity modification forming region and a crack modification forming region above the set depth layer 21 position, and the focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10 to form a cavity modification layer 22 and a crack modification layer 23. After ultrashort pulse laser stealth cutting processing, a short pulse laser with a slightly wider pulse width is used to move the focus of the short pulse laser beam to a certain range above the set depth layer 21, so that the short pulse laser beam passes through the crack modification forming area and is focused on the cavity modification forming area, and is scattered and propagated in the cavity modification forming area, so that the heat of the short pulse laser beam mainly acts on the cavity modification forming area, causing the cracks in the crack modification forming area to grow laterally outward, and the focus of the short pulse laser beam is controlled to scan the cavity modification layer 22, so that the cracks in any adjacent cavity modification forming areas in the cavity modification layer 22 are connected together through lateral growth.

[0041] Compared to existing laser cutting processes for silicon ingots, the ultrashort pulse laser used in this process can generate a void-modification region and a crack-modification region above a predetermined depth layer 21, where the ultrashort pulse laser beam is focused. Through scanning, void-modification layer 22 and crack-modification layer 23 are formed, respectively, thus refining and differentiating the modified layers in the prior art. Subsequently, when a short-pulse laser beam is used, the short-pulse laser beam is focused on the void-modification region. The short-pulse laser beam is focused above the ultrashort pulse laser beam, rather than at the same depth as in the prior art. This allows the short-pulse laser beam to penetrate the crack-modification region and then focus on the void-modification region. The short-pulse laser beam then scatters and propagates within the void-modification region, causing cracks within the void-modification region to grow laterally outward. Furthermore, through scanning, cracks within any adjacent void-modification regions in void-modification layer 22 are connected through lateral growth. Moreover, in the process of the short pulse laser beam passing through the crack modification forming area and focusing on the void modification forming area to heat the void modification forming area, since the crack modification forming area can block the growth of the crack, the upward growth length of the crack in the void modification forming area can be limited to the interval below the crack modification forming area, and the longitudinal growth length of the crack can be limited to a smaller height range, which is convenient for improving the efficiency of crack extension, while also minimizing the degree of longitudinal extension of the crack and minimizing the slice loss. That is, by subdividing the modified layer into a cavity modified layer 22 and a crack modified layer 23, and then focusing the short pulse laser beam on the cavity modified layer 22, the focus position of the short pulse laser beam is designed more accurately and reasonably, not only making the vertical height difference of the focus of the short pulse laser beam fluctuate less (because the vertical height difference of the cavity modified forming area must be smaller than the vertical height difference of the modified layer composed of the crack modified forming area and the cavity modified forming area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the cavity modified layer 22, through the crack thereon. The modified formation region blocks the vertical upward growth of cracks within the void modification formation region, confining the length of the vertical crack growth to a smaller height range, optimizing the focus position of the short-pulse laser beam, and reducing the amount and length of cracks in the modified layer extending longitudinally along the silicon carbide ingot 10. This allows more laser energy to be applied to the lateral outward growth of the cracks, increasing the number and length of lateral crack growth, enabling the cutting of thinner silicon carbide wafers, and reducing cutting loss thickness. More silicon carbide wafers can be cut from the same silicon carbide ingot 10, reducing waste. The following describes each of the above steps in detail with reference to the accompanying drawings.

[0042] First, refer to Figure 1 、 Figure 2 and Figure 3The focus of the ultrashort pulse laser beam is focused on the set depth layer 21 position of the silicon carbide ingot 10 to be cut, so as to generate a cavity modification formation region and a crack modification formation region above the set depth layer 21 position, respectively, wherein the cavity modification formation region is located between the set depth layer 21 position and the crack modification formation region. The intensity at the focal volume of the ultrashort pulse laser beam causes nonlinear absorption of laser energy by the material through multiphoton ionization, tunnel ionization, and avalanche ionization. Due to nonlinear absorption, a microscopic highly excited plasma is generated at the focal position. The microscopic size of the laser will vary when acting on different crystal materials, ranging from nanometers to submicron sizes. Therefore, no large-scale material damage will occur in the direction of laser incidence.

[0043] The depth layer 21 set during the processing is specifically related to the thickness of the peeled wafer, peeling loss thickness, etc. The focus of the ultrashort pulse laser beam can be accurately focused on the set depth layer 21 position of the silicon carbide ingot 10 by a three-axis galvanometer, an altimeter, etc.

[0044] like Figures 2 to 4 As shown in FIG, the crack modification forming area and the cavity modification forming area generated above the set depth layer 21 occupy a certain thickness space. The size of the crack modification forming area and the cavity modification forming area is related to the energy of the ultrashort pulse laser beam. The size of the crack modification forming area and the cavity modification forming area increases with the increase of laser energy. Figures 2 to 4 As shown, the cavity modification forming region can be located in the region 1-5um above the focus of the ultrashort pulse laser beam, and the crack modification forming region can be located in the region 10-30um above the cavity modification forming region, so that the cavity modification forming region and the crack modification forming region are in different depth layers, and the cavity modification layer 22 and the crack modification layer 23 can be clearly distinguished.

[0045] When selecting an ultrashort pulse laser beam, the ultrashort pulse laser beam can be a sub-picosecond pulse width laser beam, a picosecond pulse width laser beam, or a femtosecond pulse width laser beam, facilitating the generation of a more effective void modification and crack modification region above the focal point of the ultrashort pulse laser beam. For example, the pulse width of the ultrashort pulse laser beam can be any value between 243 fs and 900 fs, further enhancing the modification effect of the void modification and crack modification regions generated above the focal point of the ultrashort pulse laser beam. In a more preferred embodiment, the wavelength of the ultrashort pulse laser beam can be controlled to be between 500 and 1100 nm. Specifically, the wavelength of the ultrashort pulse laser beam can be any value between 500 and 1100 nm, such as 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or 1100 nm. This facilitates the generation of a more effective void modification and crack modification region above the focal point of the ultrashort pulse laser beam.

[0046] Next, refer to Figure 1 and Figure 4 , controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide ingot 10, so as to form a cavity modification layer 22 and a crack modification layer 23 above the position of the set depth layer 21, respectively; wherein, the cavity modification layer 22 is composed of multiple cavity modification forming regions, the crack modification layer 23 is composed of multiple crack modification forming regions, and the cavity modification layer 22 is located between the set depth layer 21 and the crack modification layer 23.

[0047] The method for controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide ingot 10 can be implemented in a variety of ways to form a void modified layer 22 and a crack modified layer 23 within the silicon carbide ingot 10, respectively. The voids in the void modified layer 22 are modified to form a region-by-region gap covering the void modified layer 22, and the cracks in the crack modified layer 23 are modified to form a region-by-region gap covering the crack modified layer 23. For example, a spiral scanning method can be implemented, or a parallel scanning method can be implemented to form multiple cutting lanes. Exemplarily, the focus of the ultrashort pulse laser beam can be controlled to scan multiple parallel first cutting paths at a set depth layer 21 of the silicon carbide ingot 10, and the interval between any two adjacent first cutting paths can be 10-25um. Specifically, the interval between any two adjacent first cutting paths can be any value between 10-25um, such as 10um, 15um, 20um, 25um, etc. Considering that the size of the void modification forming area is smaller than the size of the crack modification forming area and the crack growth range is lower, the spacing between adjacent void modification forming areas is appropriately reduced, which simplifies the difficulty of subsequent cracks growing laterally and connecting together, facilitates setting the silicon carbide explosion point interval of appropriate width, improves slicing efficiency, and simplifies scanning difficulty.

[0048] Next, refer to Figure 1 、 Figure 5 、 Figure 6 and Figure 7 After passing through the crack-modification region, a short-pulse laser beam is focused on the cavity-modification region and scattered and propagated within the cavity-modification region, causing cracks within the cavity-modification region to grow laterally outward. The pulse width of the short-pulse laser beam is greater than that of the ultrashort-pulse laser beam, and its pulse width does not reach nanosecond pulse width, but rather is within the sub-nanosecond wavelength range of picoseconds. Specifically, the short-pulse laser beam shifts upward relative to the focal point of the ultrashort-pulse laser beam. Thus, after passing through the crack-modification region, the short-pulse laser beam is focused on the cavity-modification region. The focal point of the short-pulse laser beam shifts upward by a certain amount relative to the focal point of the ultrashort-pulse laser beam. After impacting the cavity-modification region, the short-pulse laser beam utilizes the self-scattering properties of free ions after passing through the crack-modification region to create a scattering pattern of the laser light at the focused spot within the cavity-modification region. The laser light then scatters and propagates within the cavity-modification region, driving crack growth within the cavity-modification region.

[0049] In the early laser processing process, 10 -15 The laser energy with a pulse width of the order of s is absorbed inside the material. For different materials (conductors, semiconductors, insulators, etc.), its essence is that the laser introduces a non-equilibrium free electron distribution, and the energy is transferred through the interaction between electrons, lattices and phonons. Then the plasma is heated in sub-picoseconds (10 -9 s) range, accompanied by the inherent evaporation and melting process. The speed of energy transfer between the lattice and the material is related to the intrinsic properties of the material. As the laser energy continues to act, the material begins to change its phase at this stage. After that, shock radiation is generated. The time span of this process is relatively long (usually occurs in 10 -12 s to 10 -3 During the time between s and 10s, the thermal effects of the material gradually become dominant, generating a thermal front and an evaporation front, which in turn leads to a gradual increase in the reverse thrust, accompanied by a weaker secondary radiation process. The processing method described in this patent is based on the initial stage of the material's thermal effects, resulting in a cumulative thermal effect.

[0050] In addition, when a short-pulse laser beam passes through the crack modification formation area, the beam widens, jitters, and bends due to the modification of the material. However, since the crack modification formation area and the cavity modification formation area are close to each other, most of the laser light can still act on the cavity modification formation area. Although the focused spot flickers and drifts, the coherence of the laser beam deteriorates. However, the laser light after the phase change can self-scatter in the cavity modification formation area, radiating electron waves in all directions as the electromagnetic wave vibrates. The multi-directionally scattered laser light at the laser focus also causes the surrounding materials to be ionized and absorbed to form a high-energy, high-pressure area, further causing the cavity area to explode and grow under the action of the laser. Under the control of the laser polarization direction, the cracks grow in an orderly manner along the direction of the silicon carbide lattice, and the wafer is finally peeled off with the connection of the cracks in all the cutting paths.

[0051] The aforementioned void-modified region is actually a modified region where voids have not yet formed. When a focused short-pulse laser beam that can penetrate the material is subsequently loaded, when the photon energy of the short-pulse laser beam is focused on the material and the photon energy is high enough, the laser photons may directly break the chemical bonds of the sample, causing the volume of the local area to rapidly expand and explode. A sufficiently long short pulse width allows the photon energy to be immediately coupled to the silicon carbide lattice after being transferred to electrons. The photon energy will be converted into heat energy, causing the sample temperature to rise. When the temperature rises, the physical and chemical properties of the sample further change, the optical system coefficients change, and stress is generated within the sample. As the pulse width increases, the stress continues to accumulate, breaking the chemical bonds in the void-modified region created by the previous ultrashort pulse laser beam. The cracks formed between the carbon and silicon elements are further guided to radiate outward.

[0052] It's important to explain that the longer pulse width of a short-pulse laser beam compared to an ultrashort-pulse laser beam is intended to increase the light dwell time, generating a greater thermal effect and thus extending the crack's growth. After multiple, continuous short-pulse laser irradiations—which can range from 1-3 to 3-5 times—the crack can grow horizontally to over 200 microns. Growth will vary depending on the material, type of material, doping, and laser parameters such as power, pulse width, and wavelength.

[0053] When a short-pulse laser beam is selected, the short-pulse laser beam can be a sub-nanosecond laser beam to increase the amount and length of lateral crack growth. For example, the pulse width of the short-pulse laser beam can be any value between 500ps and 1ns, which is convenient for better reducing the amount and length of cracks in the modified layer that extend longitudinally along the silicon carbide ingot 10, thereby directing more laser energy to the lateral outward growth of the cracks, increasing the amount and length of lateral crack growth. In a more preferred embodiment, the wavelength of the short-pulse laser beam can be 500-1100nm. Specifically, the wavelength of the short-pulse laser beam can be any value between 500-1100nm, such as 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, etc. This is convenient for better reducing the amount and length of cracks in the modified layer that extend longitudinally along the silicon carbide ingot 10, thereby directing more laser energy to the lateral outward growth of the cracks, increasing the amount and length of lateral crack growth.

[0054] When focusing the short-pulse laser beam on the void-modification formation region, a more optimal approach is to focus the short-pulse laser beam at a position 1-4.5 μm higher than the ultrashort-pulse laser beam's focus, thereby further optimizing the short-pulse laser beam's focus position. Of course, any approach that focuses the short-pulse laser beam on the void-modification formation region is within the scope of protection of this patent.

[0055] In addition, the polarization state of the short-pulse laser beam can be simultaneously controlled to control the diffusion direction of the explosion energy in the void-modified region, and crack growth at a certain angle at the explosion point of the short-pulse laser beam can be achieved. After the short-pulse laser beam passes through the crack-modified region, it is focused on the void-modified region and scattered and propagated in the void-modified region, causing the cracks in the void-modified region to grow laterally outward. By adjusting the polarization state of the short-pulse laser beam, the electron propagation direction can be extended along the silicon carbide lattice direction of the silicon carbide ingot 10, forming a 3-5° lateral growth crack. This can further reduce the amount and length of cracks in the modified layer that extend longitudinally along the silicon carbide ingot 10, thereby directing more laser energy to the lateral outward growth of the cracks, increasing the number and length of lateral crack growth. For example, the polarization state of the short-pulse laser beam can be adjusted to ensure that the growth direction of the lateral growth crack has an angle of 3-5° relative to the cutting path direction.

[0056] Next, refer to Figure 1 、 Figure 5 and Figure 7, control the focus of the short pulse laser beam to scan the void modification layer 22, so that the cracks in any adjacent void modification forming areas in the void modification layer 22 are connected together through lateral growth. The specific way of controlling the focus of the short pulse laser beam to scan the void modification layer 22 is related to the way of controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21. For example, when the way of controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 adopts a spiral scanning way, the way of controlling the focus of the short pulse laser beam to scan the void modification layer 22 is also a spiral scanning way. When the way of controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 adopts a method of multiple parallel first cutting paths, the way of controlling the focus of the second short pulse laser beam to scan the void modification layer 22 can be specifically: controlling the focus of the short pulse laser beam to scan multiple parallel second cutting paths in the void modification layer 22, and each second cutting path is located directly above a first cutting path, thereby simplifying the scanning difficulty.

[0057] In addition, when controlling the focus of the short pulse laser beam to scan multiple parallel second cutting paths in the void modification layer 22, the focus of the short pulse laser beam can be controlled to scan at each second cutting path for more than or equal to three times. By using the short pulse laser beam for multiple processing and continuous heat injection, the explosion point crack connection is achieved, the amount and length of the lateral growth of the crack in the crack modification formation area are increased, and the cracks extending from adjacent second cutting paths are connected together faster, which facilitates the realization of the implicit crack induced growth method to achieve the purpose of separating the silicon carbide ingot 10 into multiple silicon carbide wafers.

[0058] Next, refer to Figure 1 The silicon carbide ingot 10 is partially peeled off with the void modified layer 22 as the interface to generate a silicon carbide wafer. Specifically, the silicon carbide wafer can be peeled off with the void modified layer 22 as the interface by stretching, rotating, or other methods to peel the wafer above the void modified layer 22 from the silicon carbide ingot 10.

[0059] In addition, the following method can also be used to peel off a portion of the silicon carbide ingot 10 with the cavity modified layer 22 as the interface to generate a wafer. A diamond wire saw is used to perform wire cutting on the cavity modified layer, and a portion of the silicon carbide ingot is peeled off with the cavity modified layer as the interface to generate a silicon carbide wafer. By first focusing the laser beam at a predetermined depth layer from the inside of the silicon carbide ingot and scanning, a cavity modified layer is formed at the predetermined depth layer position. In the process of forming the cavity modified layer, the energy density at the laser focus exceeds the silicon carbide ablation threshold, the material temperature rises suddenly, and the silicon carbide decomposes under high temperature conditions to generate amorphous silicon or single crystal silicon or a mixture of the two and carbon. The specific amorphous silicon and single crystal silicon are determined by the laser energy density. When the laser energy is large, single crystal silicon is generated, and when the laser energy is small, amorphous silicon is generated. Thereafter, a diamond wire saw is used to perform wire cutting on the cavity modified layer, and a portion of the silicon carbide ingot is peeled off with the cavity modified layer as the interface to generate a silicon carbide wafer. Since the materials of the void modification layer are single crystal silicon, amorphous silicon and carbon, their hardness is much lower than that of silicon carbide. In the process of wire cutting the void modification layer with a diamond wire saw, the wear of the diamond wire saw can be reduced, thereby reducing the loss of the diamond wire saw and reducing the difficulty of wire cutting. Therefore, a thinner diamond wire saw can be selected to reduce the loss of silicon carbide ingots and improve the slicing output rate of silicon carbide ingots. At the same time, the diamond wire saw cutting method is not easy to cause the silicon carbide wafer to break due to uneven force. That is, compared with the laser cutting + mechanical stripping method, the present application uses a diamond wire saw to cut the void modification layer and peel off the silicon carbide wafer from the modified silicon carbide ingot without the need for mechanical stripping. This can avoid the phenomenon that the silicon carbide wafer may break due to uneven force during the mechanical stripping process, thereby improving the product yield and stripping efficiency.

[0060] After the silicon carbide wafer is stripped from the silicon carbide ingot and before it is ground, a step can be added in which the silicon carbide wafer is immersed in a chemical solution to etch the interface of the modified layer of the silicon carbide wafer. By using the chemical solution to etch the interface of the modified layer of the silicon carbide wafer, defects such as residual stress, dislocations, and cracks generated during the silicon carbide wafer stripping step can be removed. The interface of the modified layer of the silicon carbide wafer is then ground. Since there is no or little residual stress on the interface of the modified layer of the silicon carbide wafer at this time, the increase in defects during the grinding process is avoided. The phenomenon that the extrusion during the grinding process increases residual stress and thus causes continued crack growth can be slowed down. As a result, less material can be ground to completely remove the damaged layer, reducing ingot loss and improving wafer quality. In addition, the interface of the modified layer after chemical solution etching is more flat, which can reduce the difficulty of subsequent grinding and improve grinding efficiency.

[0061] In the various embodiments shown above, an ultrashort pulse laser is first used to focus the ultrashort pulse laser beam on a set depth layer 21 position of the silicon carbide ingot 10 to generate a cavity modification forming region and a crack modification forming region above the set depth layer 21 position, respectively, and the focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10 to form a cavity modification layer 22 and a crack modification layer 23. After ultrashort pulse laser stealth cutting processing, a short pulse laser with a slightly wider pulse width is used to move the focus of the short pulse laser beam to a certain range above the set depth layer 21, so that the short pulse laser beam passes through the crack modification forming area and is focused on the cavity modification forming area, and is scattered and propagated in the cavity modification forming area, so that the heat of the short pulse laser beam mainly acts on the cavity modification forming area, causing the cracks in the crack modification forming area to grow laterally outward, and the focus of the short pulse laser beam is controlled to scan the cavity modification layer 22, so that the cracks in any adjacent cavity modification forming areas in the cavity modification layer 22 are connected together through lateral growth.

[0062] Compared to existing laser cutting processes for silicon ingots, the ultrashort pulse laser used in this process can generate a void-modification region and a crack-modification region above a predetermined depth layer 21, where the ultrashort pulse laser beam is focused. Through scanning, void-modification layer 22 and crack-modification layer 23 are formed, respectively, thus refining and differentiating the modified layers in the prior art. Subsequently, when a short-pulse laser beam is used, the short-pulse laser beam is focused on the void-modification region. The short-pulse laser beam is focused above the ultrashort pulse laser beam, rather than at the same depth as in the prior art. This allows the short-pulse laser beam to penetrate the crack-modification region and then focus on the void-modification region. The short-pulse laser beam then scatters and propagates within the void-modification region, causing cracks within the void-modification region to grow laterally outward. Furthermore, through scanning, cracks within any adjacent void-modification regions in void-modification layer 22 are connected through lateral growth. Moreover, in the process of the short pulse laser beam passing through the crack modification forming area and focusing on the void modification forming area to heat the void modification forming area, since the crack modification forming area can block the growth of the crack, the upward growth length of the crack in the void modification forming area can be limited to the interval below the crack modification forming area, and the longitudinal growth length of the crack can be limited to a smaller height range, which is convenient for improving the efficiency of crack extension, while also minimizing the degree of longitudinal extension of the crack and minimizing the slice loss. That is, by subdividing the modified layer into a cavity modified layer 22 and a crack modified layer 23, and then focusing the short pulse laser beam on the cavity modified layer 22, the focus position of the short pulse laser beam is designed more accurately and reasonably, not only making the vertical height difference of the focus of the short pulse laser beam fluctuate less (because the vertical height difference of the cavity modified forming area must be smaller than the vertical height difference of the modified layer composed of the crack modified forming area and the cavity modified forming area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the cavity modified layer 22, through the crack thereon. The modified forming area blocks the vertical upward growth of cracks in the void modified forming area, limits the length of the vertical growth of the cracks to a smaller height range, optimizes the focusing position of the short pulse laser beam, reduces the amount and length of the cracks in the modified layer extending longitudinally along the silicon carbide ingot 10, and thus applies more laser energy to the lateral outward growth of the cracks, which can increase the number and length of lateral crack growth, can cut thinner silicon carbide wafers, and also reduce the cutting loss thickness. The same silicon carbide ingot 10 can cut more silicon carbide wafers, reducing waste.

[0063] In addition, the embodiment of the present invention also provides a laser slicing device for silicon carbide ingots, referring to Figures 1 to 8The laser slicing device includes: a stage, an ultrashort pulse laser system, a first scanning system, a short pulse laser system, a second scanning system, and a separation system. The stage is used to hold the silicon carbide ingot 10 to be cut thereon. The ultrashort pulse laser system is used to provide an ultrashort pulse laser beam and focus the ultrashort pulse laser beam on a set depth layer 21 of the silicon carbide ingot 10 to be cut, so as to generate a cavity modification formation region and a crack modification formation region above the set depth layer 21, respectively; wherein the cavity modification formation region is located between the set depth layer 21 and the crack modification formation region. The first scanning system is used to control the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide ingot 10, thereby forming a void modification layer 22 and a crack modification layer 23 above the set depth layer 21, respectively. The void modification layer 22 is composed of multiple void modification formation regions, and the crack modification layer 23 is composed of multiple crack modification formation regions, with the void modification layer 22 located between the set depth layer 21 and the crack modification layer 23. The short pulse laser system is used to provide a short pulse laser beam. The short pulse laser system is also used to focus the short pulse laser beam on the void modification formation region after passing the short pulse laser beam through the crack modification formation region, and scatter and propagate in the void modification formation region, causing cracks in the void modification formation region to grow laterally outward. The second scanning system is used to control the focus of the short pulse laser beam to scan the void modification layer 22, so that cracks in any adjacent void modification formation regions in the void modification layer 22 are connected by lateral growth. The separation system is used to peel off a portion of the silicon carbide ingot 10 using the void modified layer 22 as an interface to generate a silicon carbide wafer.

[0064] like Figure 8 In the laser slicing device for a silicon carbide ingot shown, the first scanning system and the second scanning system can be realized by a three-axis motion table, and the stage is fixed on the three-axis motion table. The ultrashort pulse laser system and the short pulse laser system can respectively use different lasers, and different laser systems can share some optical devices, and optical switches are set on different optical paths for switching. Among them, the parameter setting method of the ultrashort pulse laser beam provided by the above-mentioned ultrashort pulse laser system can refer to the description of the relevant part of the laser slicing method of the aforementioned silicon carbide ingot 10, and will not be repeated here. The parameter setting method of the short pulse laser beam provided by the above-mentioned short pulse laser system can refer to the description of the relevant part of the laser slicing method of the aforementioned silicon carbide ingot 10, and will not be repeated here. Reference Figure 8 , CCD cameras and light sources can also be set on different laser systems to observe the processing position in real time.

[0065] like Figure 9 Based on Figure 8 The laser slicing operation flow chart of the laser slicing device for silicon carbide ingot is shown. Figure 9 The operation flow shown can complete all the operation steps of any of the laser slicing methods shown above.

[0066] In the above scheme, an ultrashort pulse laser is first used to focus the ultrashort pulse laser beam on the set depth layer 21 position of the silicon carbide ingot 10 to generate a cavity modification forming region and a crack modification forming region above the set depth layer 21 position, and the focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10 to form a cavity modification layer 22 and a crack modification layer 23. After ultrashort pulse laser stealth cutting processing, a short pulse laser with a slightly wider pulse width is used to move the focus of the short pulse laser beam to a certain range above the set depth layer 21, so that the short pulse laser beam passes through the crack modification forming area and is focused on the cavity modification forming area, and is scattered and propagated in the cavity modification forming area, so that the heat of the short pulse laser beam mainly acts on the cavity modification forming area, causing the cracks in the crack modification forming area to grow laterally outward, and the focus of the short pulse laser beam is controlled to scan the cavity modification layer 22, so that the cracks in any adjacent cavity modification forming areas in the cavity modification layer 22 are connected together through lateral growth.

[0067] Compared to existing laser cutting processes for silicon ingots, the ultrashort pulse laser used in this process can generate a void-modification region and a crack-modification region above a predetermined depth layer 21, where the ultrashort pulse laser beam is focused. Through scanning, void-modification layer 22 and crack-modification layer 23 are formed, respectively, thus refining and differentiating the modified layers in the prior art. Subsequently, when a short-pulse laser beam is used, the short-pulse laser beam is focused on the void-modification region. The short-pulse laser beam is focused above the ultrashort pulse laser beam, rather than at the same depth as in the prior art. This allows the short-pulse laser beam to penetrate the crack-modification region and then focus on the void-modification region. The short-pulse laser beam then scatters and propagates within the void-modification region, causing cracks within the void-modification region to grow laterally outward. Furthermore, through scanning, cracks within any adjacent void-modification regions in void-modification layer 22 are connected through lateral growth. Moreover, in the process of the short pulse laser beam passing through the crack modification forming area and focusing on the void modification forming area to heat the void modification forming area, since the crack modification forming area can block the growth of the crack, the upward growth length of the crack in the void modification forming area can be limited to the interval below the crack modification forming area, and the longitudinal growth length of the crack can be limited to a smaller height range, which is convenient for improving the efficiency of crack extension, while also minimizing the degree of longitudinal extension of the crack and minimizing the slice loss. That is, by subdividing the modified layer into a cavity modified layer 22 and a crack modified layer 23, and then focusing the short pulse laser beam on the cavity modified layer 22, the focus position of the short pulse laser beam is designed more accurately and reasonably, not only making the vertical height difference of the focus of the short pulse laser beam fluctuate less (because the vertical height difference of the cavity modified forming area must be smaller than the vertical height difference of the modified layer composed of the crack modified forming area and the cavity modified forming area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the cavity modified layer 22, through the crack thereon. The modified forming area blocks the vertical upward growth of cracks in the void modified forming area, limits the length of the vertical growth of the cracks to a smaller height range, optimizes the focusing position of the short pulse laser beam, reduces the amount and length of the cracks in the modified layer extending longitudinally along the silicon carbide ingot 10, and thus applies more laser energy to the lateral outward growth of the cracks, which can increase the number and length of lateral crack growth, can cut thinner silicon carbide wafers, and also reduce the cutting loss thickness. The same silicon carbide ingot 10 can cut more silicon carbide wafers, reducing waste.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A laser slicing method for silicon carbide ingots, characterized in that: include: Focusing the ultrashort pulse laser beam at a set depth layer position of the silicon carbide ingot to be cut, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position, respectively; wherein the cavity modification forming region is located between the set depth layer position and the crack modification forming region; Controlling the focus of the ultrashort pulse laser beam to scan a set depth layer of the silicon carbide ingot to form a void modified layer and a crack modified layer above the set depth layer, respectively; wherein the void modified layer is composed of a plurality of the void modified forming regions, the crack modified layer is composed of a plurality of the crack modified forming regions, and the void modified layer is located between the set depth layer and the crack modified layer; After passing a short pulse laser beam through the crack modification forming region, the short pulse laser beam is focused on the cavity modification forming region and scattered and propagated in the cavity modification forming region, so that the cracks in the cavity modification forming region grow laterally outward; Controlling the focus of the short pulse laser beam to scan the void modified layer so that cracks in any adjacent void modified regions of the void modified layer are connected together by lateral growth; A portion of the silicon carbide ingot is peeled off with the cavity reformed layer as an interface to generate a silicon carbide wafer.

2. The laser slicing method according to claim 1, wherein: The ultrashort pulse laser beam is a sub-picosecond pulse width laser beam, a picosecond pulse width laser beam or a femtosecond pulse width laser beam.

3. The laser slicing method according to claim 2, wherein: The pulse width of the ultrashort pulse laser beam is 243fs-900fs, and the wavelength of the ultrashort pulse laser beam is 500-1100nm.

4. The laser slicing method according to claim 1, wherein: The short pulse laser beam is a sub-nanosecond laser beam.

5. The laser slicing method according to claim 4, wherein: The pulse width of the short pulse laser beam is 500 ps-1 ns, and the wavelength of the short pulse laser beam is 500-1100 nm.

6. The laser slicing method according to claim 1, wherein: The focusing point of the short pulse laser beam is 1-4.5 μm higher than the focusing point of the ultrashort pulse laser beam.

7. The laser slicing method according to claim 1, wherein: After passing the short pulse laser beam through the crack modification forming area, the short pulse laser beam is focused on the cavity modification forming area, and scattered and propagated in the cavity modification forming area, so that the cracks in the cavity modification forming area grow laterally outward, including: The polarization state of the short pulse laser beam is adjusted so that the electron propagation direction extends along the silicon carbide lattice direction of the silicon carbide ingot, forming a 3-5° transverse growth crack.

8. The laser slicing method according to claim 1, wherein: Controlling the focus of the ultrashort pulse laser beam to scan the silicon carbide ingot at a set depth layer includes: Controlling the focus of the ultrashort pulse laser beam to scan a plurality of parallel first cutting lines at a set depth layer of the silicon carbide ingot, wherein the interval between any two adjacent first cutting lines is 10-25 μm; The controlling the focus of the short pulse laser beam to scan the cavity modified layer comprises: The focus of the short pulse laser beam is controlled to scan a plurality of parallel second cutting streets in the cavity modified layer, and each second cutting street is located directly above one of the first cutting streets.

9. The laser slicing method according to claim 8, wherein: The controlling the focus of the short pulse laser beam to scan a plurality of parallel second cutting paths in the cavity modified layer comprises: The focus of the short pulse laser beam is controlled to scan at each second cutting street for a number of times greater than or equal to three times.

10. A laser slicing device for silicon carbide ingots, characterized in that: include: a stage for holding the silicon carbide ingot to be cut thereon; An ultrashort pulse laser system is used to provide an ultrashort pulse laser beam and focus the ultrashort pulse laser beam at a set depth layer position of the silicon carbide ingot to be cut, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position, respectively; a first scanning system, configured to control the focus of the ultrashort pulse laser beam to scan a set depth layer of the silicon carbide ingot, so as to form a void modified layer and a crack modified layer above the set depth layer, respectively; wherein the void modified layer is composed of a plurality of the void modified forming regions, the crack modified layer is composed of a plurality of the crack modified forming regions, and the void modified layer is located between the set depth layer and the crack modified layer; a short-pulse laser system for providing a short-pulse laser beam having a pulse width greater than that of the ultrashort-pulse laser beam; and for focusing the short-pulse laser beam on the cavity-modification-forming region after passing it through the crack-modification-forming region, and scattering and propagating the short-pulse laser beam in the cavity-modification-forming region to cause the cracks in the cavity-modification-forming region to grow laterally outward. a second scanning system for controlling the focus of the short pulse laser beam to scan the void modified layer so that cracks in any adjacent void modified regions of the void modified layer are connected together by lateral growth; The separation system is used to peel off a part of the silicon carbide ingot using the cavity modified layer as an interface to generate a silicon carbide wafer.

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