A controllable crack silicon carbide laser lift-off method

Abstract

The present application relates to a controllable crack silicon carbide laser stripping method, which comprises the following steps: first focusing a pulsed laser on a preset stripping surface inside a silicon carbide ingot, and repeatedly performing at least two laser scans along a preset laser scanning path, at least one laser parameter of the at least two laser scans is regulated so that the modified point spacing decreases with the number of scans, to sequentially form a plurality of discrete modified points and a plurality of continuous modified points on the preset stripping surface, an overlapping area is formed between at least two adjacent continuous modified points on the same laser scanning line, and then a crack extending along the cleavage surface of the silicon carbide ingot and passing through the discrete modified points and adjacent laser scanning lines is formed in the overlapping area, and then the silicon carbide ingot is stripped along the preset stripping surface to obtain a wafer and a remaining ingot. The present application has the advantages of uniform and consistent modification depth, improved wafer surface quality, stable and controllable process, and adaptation to large-scale production.

Description

Technical Field

[0001] This invention relates to the technical field of semiconductor device processing, and in particular to a method for laser ablation of silicon carbide with controllable cracks. Background Technology

[0002] Silicon carbide, as a third-generation semiconductor material, possesses characteristics such as high breakdown electric field, high thermal conductivity, and excellent chemical stability, making it promising for applications in new energy vehicles, rail transportation, and 5G communications. However, silicon carbide is extremely hard and brittle. Traditional methods such as mechanical cutting and wire sawing suffer from high material loss, low processing efficiency, and susceptibility to microcracks and edge chipping, making it difficult to meet the demands of large-scale production of large-size, high-quality silicon carbide substrates. The exfoliation process of silicon carbide ingots is a key factor restricting the efficiency and quality of substrate fabrication. Laser internal modification exfoliation technology, by focusing a laser beam inside the ingot to form a modification layer, typically uses single or cross-scanning to form a continuous modification layer. Then, mechanical force or ultrasonic methods are used to separate the ingot from the wafer. This technology offers advantages such as non-contact processing, low damage, and high processing efficiency, and has become an important development direction in this field.

[0003] Chinese patent CN115592255A discloses a method and apparatus for laser peeling off silicon carbide ingots. The method involves first focusing a laser on a preset plane inside the ingot, then performing secondary laser processing on the plane according to a set direction and scan line spacing to create multiple popping points, thus preparing a modified layer. The modified layer is then irradiated and heated using a xenon lamp. After heating, opposing tensile forces perpendicular to the end faces are applied to both ends of the ingot to peel the wafer off. This method prepares the modified layer through orthogonal cross-scanning, forming planar popping points at the scan intersections to reduce peeling tensile stress. After heating, a reverse tensile force is applied to achieve peeling. However, this method only reduces peeling stress through popping points, lacking an active control mechanism for the modification depth and a crack-guided design. The modified layer is susceptible to disordered diffusion due to material parameter fluctuations and beam drift, making it difficult to guarantee the consistency and stability of the peeling process.

[0004] Chinese Patent CN115555736B discloses a method and apparatus for laser stripping of silicon carbide ingots. The method first focuses an ultrashort pulse laser beam through the first end face of the silicon carbide ingot onto a predetermined depth layer. Above this depth layer, void modification and crack modification regions are generated, and the process scans to form void modification and crack modification layers. Next, a short pulse laser beam is focused through the second end face of the silicon carbide ingot onto the void modification region. The laser beam scatters and propagates within this region, causing heat from the short pulse laser beam to act on it, resulting in transverse outward growth of cracks within the crack modification region. The process scans the region to connect adjacent void modification regions through transverse growth. The above method uses a dual-end-face dual-laser staged processing method. It forms a void modification layer and a crack modification layer by using an ultra-short pulse laser, and then uses a short pulse laser to induce the crack to connect laterally to achieve peeling. However, the micro-voids only serve as a longitudinal buffer layer and are not an interception structure to constrain the lateral expansion of the modification lines. It also does not combine the anisotropy of silicon carbide cleavage surface to guide the crack in a directional manner. The uniformity of modification depth lacks active control, and there are still problems such as uncontrolled modification line path, uneven modification depth, and disordered crack extension.

[0005] Chinese Patent CN107262945B discloses a method for generating wafers, capable of efficiently generating wafers from ingots. The wafer generation method generates wafers from SiC ingots, and includes a first refining layer formation step and a second refining layer formation step. Chinese Patent CN107464778B discloses a wafer generation method for generating SiC wafers from single-crystal SiC ingots, and this wafer generation method includes: a peeling surface formation step, forming a peeling surface composed of a refining layer, cracks, and a bonding layer; and a wafer peeling step, peeling a portion of the ingot using the peeling surface as an interface to generate a wafer. Although the two methods mentioned above involve forming discrete modified points inside the material and then forming a continuous modified layer, or constraining crack propagation through multiple connecting layers, neither of them combines the anisotropic characteristics of silicon carbide cleavage planes to conduct directional guidance and precise control of cracks. They rely solely on passive structures or process parameters to constrain crack direction, which cannot achieve coordinated and precise control of modified line propagation and crack propagation. This makes it difficult to fundamentally solve the core problems such as inconsistent modified depth, disordered upward extension of cracks to the near-surface region of the ingot, resulting in residual damage marks on the wafer surface after subsequent grinding and low product qualification rate.

[0006] In summary, existing laser ablation technology for silicon carbide ingots still has the following problems: 1) Poor consistency of modification depth: It is easily affected by factors such as fluctuations in the refractive index of silicon carbide materials, uneven distribution of laser energy, and beam drift, resulting in significant differences in the laser modification depth in different regions of the ingot. Furthermore, there is a lack of effective depth interception and constraint mechanisms, which can easily lead to cracking, warping, and edge breakage during subsequent ablation, seriously affecting the yield of finished products; 2) Disorderly crack propagation: Laser-induced microcracks tend to extend irregularly along cleavage planes, making it impossible to achieve directional and controllable propagation. Some cracks may extend upwards to the near-surface area of ​​the ingot, which may result in damage marks on the wafer even after grinding to the specified thickness, directly causing the product to be unqualified; 3) Insufficient utilization of crystal orientation and cleavage plane features: The anisotropic characteristics of silicon carbide crystal orientation and cleavage planes are not combined to guide the cracks in a directional manner. Cracks tend to deviate from the preset modification layer path, further aggravating the problems of uneven modification depth and uncontrolled cracking, making it difficult to achieve high-quality and highly consistent ingot ablation. Therefore, there is an urgent need to develop a laser ablation method that can achieve precise interception of modified silicon carbide ingots and directional crack propagation, so as to significantly improve the ablation quality and yield of silicon carbide ingots. Summary of the Invention

[0007] The problem to be solved by the present invention is to provide a controllable crack laser ablation method for silicon carbide, which addresses the above-mentioned shortcomings of the prior art. It solves the problems of poor uniformity of modification depth, high disorder of crack propagation, and insufficient utilization of crystal orientation and cleavage plane features in the existing methods. It can achieve precise interception of modification depth and directional crack propagation, and has the advantages of uniform modification depth, improved wafer surface quality, stable and controllable process, and adaptability to large-scale production.

[0008] The above-mentioned objective of this invention is achieved through the following technical solutions:

[0009] A controllable crack-forming silicon carbide laser ablation method includes the following steps: first, a pulsed laser is focused on a preset ablation surface inside a silicon carbide ingot, and at least two laser scans are repeated along a preset laser scanning path. At least one laser parameter of the at least two laser scans is adjusted such that the spacing between the modified particles decreases with the number of scans, thereby sequentially forming multiple discrete modified particles and multiple continuous modified particles on the preset ablation surface. An overlapping region is formed between at least two adjacent continuous modified particles on the same laser scanning line. Then, a crack is formed in the overlapping region, extending two-dimensionally along the cleavage plane of the silicon carbide ingot and passing through the discrete modified particles and adjacent laser scanning lines. Finally, the silicon carbide ingot is ablated along the preset ablation surface to obtain a wafer and a remaining ingot.

[0010] Specifically, in the "laser scanning" process of this invention,

[0011] The specific meaning of the "laser scanning path" refers to the trajectory that the laser scanning focus moves along when it moves on a preset peeling surface inside a silicon carbide ingot. The scanning trajectory segments that are spaced apart from each other are the laser scanning lines, which can be, for example, line-by-line scanning paths.

[0012] The specific meaning of "modified point" refers to the modified region formed after laser irradiation of the interior of silicon carbide ingot, with each laser pulse (series) corresponding to one modified point.

[0013] The term "cleavage plane" specifically refers to the plane where the atomic bonds in silicon carbide crystal are weakest, and the energy required to crack along this plane is the lowest. It is a naturally occurring, easily cracked crystal plane in silicon carbide, namely the (0001) plane, which is parallel to... Crystal orientation, and tilted near the surface of the silicon carbide ingot;

[0014] The term "crack" specifically refers to the fissures created when a laser pulse acts on the modified region of a silicon carbide ingot. Under the superposition of stress in the overlapping area of ​​adjacent continuous modified particles, these fissures can extend parallel to the silicon carbide ingot. The crystal orientation extends laterally and obliquely along the cleavage plane, eventually connecting multiple modified particles to form a continuous crack surface that extends in an approximately serrated orderly manner along the preset peeling surface, providing a separation basis for subsequent ingot peeling.

[0015] Furthermore, during the laser scanning process, the laser scanning path is controlled to be approximately perpendicular to the silicon carbide ingot. The crystal orientation, and the direction of the laser scanning path used to form continuous modified particles is the direction that can extend downward along the cleavage plane of the silicon carbide ingot to form cracks.

[0016] After the laser scanning is completed, because the laser scanning path is approximately perpendicular to the silicon carbide ingot... Crystal orientation, laser scanning lines and The angle between crystal orientations needs to be controlled within 80~90°, from parallel to the silicon carbide ingot. Looking at the crystal orientation, the modified particles on adjacent laser scanning lines are approximately at the same height on the cleavage plane. After extending laterally along the preset peeling surface, the modified particles pass through the adjacent laser scanning lines. Since the direction of the laser scanning path forms an acute angle with the cleavage plane, the anisotropic characteristics of the silicon carbide cleavage plane are used to guide the crack to extend downward along the cleavage plane through the pre-formed discrete modified particles, avoiding the disorderly upward propagation of the crack to the near-surface area of ​​the ingot. By adopting the above scheme, the orderly extension of the crack in each overlapping area is achieved, avoiding the disorderly extension of the crack deviating from the preset peeling surface (different breakpoints, lengths, and depths), ensuring that the crack always extends in two dimensions within the area where the preset peeling surface is located, realizing precise control of the modification depth, solving the problems of uneven modification depth and disordered crack extension in the existing technology, effectively reducing the damage residue in the near-surface area of ​​the ingot, and improving the surface quality of the wafer after peeling.

[0017] Furthermore, during the laser scanning process, the distance between the modified particles in at least two laser scans is controlled to be between 1 and 40 μm and decreases with the number of scans.

[0018] And / or, during the laser scanning process, the laser pulse width of at least two laser scans is controlled to increase with the number of scans. This allows different laser scans to sequentially achieve discrete modified particles that are separated and have uniform depth, as well as continuous modified particles that can overlap and are interconnected, ultimately forming a continuous modified layer with stable and uniform depth through crack propagation.

[0019] Furthermore, during the laser scanning process, the laser pulse width of at least two laser scans is controlled to be between 0.0001 and 30 ns and increases with the number of scans.

[0020] And / or, during the laser scanning process, the energy of the laser single pulse for at least two laser scans is controlled to decrease with the number of scans. This ensures the formation of effective and stable discrete modified particles within the silicon carbide ingot, providing a basis for subsequent interception of crack depth through modification.

[0021] Furthermore, during the laser scanning process, the laser single pulse energy of at least two laser scans is controlled to be between 10 and 150 μJ and decreases with the number of scans.

[0022] The decreasing / increasing methods can be linear decreasing / increasing with the number of scans, step decreasing / increasing, or curve decreasing / increasing.

[0023] Furthermore, the method includes the following steps:

[0024] S1 focuses the first pulse laser onto a preset peeling surface inside a silicon carbide ingot and performs a first laser scan along a preset laser scanning path to form multiple discrete modified points on the preset peeling surface, thereby obtaining a modified depth interception layer.

[0025] S2 focuses the second pulse laser onto a preset peeling surface inside the silicon carbide ingot and performs a second laser scan along a preset laser scanning path, decreasing the spacing between modified particles to form multiple continuous modified particles on the preset peeling surface. An overlapping region is formed between at least two adjacent continuous modified particles on the same laser scanning line, and a crack is formed in the overlapping region that extends two-dimensionally along the cleavage surface of the silicon carbide ingot and passes through the discrete modified particles and adjacent laser scanning lines, thus obtaining a continuous modified layer.

[0026] S3 peels off the silicon carbide ingot along the preset peeling surface to obtain a wafer and the remaining ingot.

[0027] In this process, while keeping the laser scanning path unchanged, based on the orientation constraints of the laser processing direction and the crystal orientation / cleavage plane, the discrete modified points formed by S1 are independent and have uniform depth. The modified depth interception layer formed by them can limit the modified depth of the second pulse laser, so that the modified depth of the silicon carbide ingot remains uniform and consistent, improving the uniformity and stability of peeling. S2 performs laser scanning along the downward extension direction of the cleavage plane, which can make the laser-induced microcracks extend downward in an orderly manner along the cleavage plane, avoiding the cracks from extending upward to the near-surface area of ​​the silicon carbide ingot and causing residual damage. This ensures that the wafer is free of residue after grinding to the specified thickness, improving the product qualification rate.

[0028] Preferably, in S1, the laser parameters of the first laser scan satisfy at least one of the following conditions:

[0029] Laser wavelength: 500~1100nm;

[0030] Modified particle spacing: 10~40μm

[0031] Pulse width: 0.0001~20ns;

[0032] Focal spot diameter: 0.5~3.0μm;

[0033] Numerical aperture (NA) of the condenser lens: 0.4~0.9.

[0034] More preferably, in S1, the laser parameters of the first laser scan satisfy at least one of the following conditions:

[0035] Laser wavelength: 500~1100nm;

[0036] Modified particle spacing: 10~30μm

[0037] Single pulse energy: 30~150μJ;

[0038] Pulse width: 0.0001~5ns;

[0039] Focal spot diameter: 1.5~2μm;

[0040] Numerical aperture (NA) of the condenser lens: 0.6~0.8.

[0041] Preferably, in S2, the laser parameters of the second laser scan satisfy at least one of the following conditions:

[0042] Laser wavelength: 500~1100nm;

[0043] Modified particle spacing: 1~10μm

[0044] Pulse width: 5~30ns;

[0045] Focal spot diameter: 0.5~3.0μm;

[0046] Numerical aperture (NA) of the condenser lens: 0.4~0.9.

[0047] More preferably, in S2, the laser parameters of the second laser scan satisfy at least one of the following conditions:

[0048] Laser wavelength: 500~1100nm;

[0049] Modified particle spacing: 2~8μm

[0050] Single pulse energy: 10~100μJ;

[0051] Pulse width: 15~20ns;

[0052] Focal spot diameter: 1.5~2μm;

[0053] Numerical aperture (NA) of the condenser lens: 0.6~0.8.

[0054] In summary, the beneficial technical effects of the present invention are as follows:

[0055] 1. Because this invention employs at least two laser scans, and the spacing between modified particles decreases with the number of scans, discrete modified particles are first constructed with a larger spacing to form a modified depth interception layer, and then continuous modified particles are formed with a smaller spacing. Cracks are induced to extend two-dimensionally along the cleavage plane in the overlapping area, which effectively limits the depth range of subsequent modified processing. This significantly reduces the difference in modified depth caused by factors such as material refractive index fluctuations and laser energy drift, achieving the effect of uniform modified depth of the entire ingot and a significant reduction in processing defects such as cracks and warping during the peeling process.

[0056] 2. In this invention, it is preferable to use a laser scanning path that is approximately perpendicular to... The laser scanning direction used to form continuous modified particles extends downward along the cleavage plane. By fully utilizing the anisotropic characteristics of the silicon carbide cleavage plane, the laser-induced microcracks are guided to extend downward in an orderly manner along the cleavage plane, avoiding the disorderly upward movement of cracks into the near-surface area of ​​the ingot. As a result, the wafer is ground to the specified thickness without any residual damage marks on the surface and the product qualification rate is significantly improved.

[0057] 3. The method of the present invention first forms a discrete modified point interception layer with a first modified laser with narrow pulse width, high single pulse energy, and large spacing, and then forms a continuous modified layer along the same path with a second modified laser with wide pulse width, low single pulse energy, and small spacing, and directionally guides the crack to propagate downward. This achieves dual control of "discrete point depth constraint + directional propagation of cleavage surface", which greatly reduces the sensitivity of the process to laser parameter drift and environmental fluctuations. As a result, it achieves a comprehensive effect of high process stability, adaptability to large-scale and efficient peeling of large-size silicon carbide ingots, and reduced production costs. Attached Figure Description

[0058] Figure 1 This is a flowchart of the method provided in Embodiment 1 of the present invention.

[0059] Figure 2 It is the silicon carbide ingot of Embodiment 3 of the present invention. A schematic diagram of the connection relationship between crystal orientations and cleavage planes.

[0060] Figure 3 This is a schematic diagram showing the connection relationship between silicon carbide ingots, discrete modified particles, and cracks formed by continuous modified particles under different laser scanning directions in Embodiment 3 of the present invention.

[0061] Figure 4 These are surface morphology diagrams of the continuous modified layers in Embodiments 6, 8, and Comparative Examples 1-2 of the present invention.

[0062] Figure 5 These are surface morphology diagrams of the wafer and remaining ingot in Embodiment 6 of the present invention. Detailed Implementation

[0063] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0064] Example

[0065] Example 1: Refer to Figure 1This invention discloses a controllable crack-forming silicon carbide laser ablation method, comprising the following steps: first, focusing a pulsed laser onto a preset ablation surface inside a silicon carbide ingot, and repeating at least two laser scans along a preset laser scanning path; at least one laser parameter of the at least two laser scans is adjusted such that the spacing between the modified particles decreases with the number of scans, thereby sequentially forming multiple discrete modified particles and multiple continuous modified particles on the preset ablation surface; an overlapping region is formed between at least two adjacent continuous modified particles on the same laser scanning line; and then a crack is formed in the overlapping region, extending two-dimensionally along the cleavage plane of the silicon carbide ingot and passing through the discrete modified particles and adjacent laser scanning lines; and then peeling the silicon carbide ingot along the preset ablation surface to obtain a wafer and the remaining ingot.

[0066] Example 2: This is a controlled crack laser ablation method for silicon carbide disclosed in this invention. The difference from Example 1 is that it includes the following steps:

[0067] S1 focuses the first pulse laser onto the preset peeling surface inside the silicon carbide ingot and performs the first laser scan along the preset laser scanning path to form multiple discrete modified points on the preset peeling surface, thereby obtaining a modified depth interception layer.

[0068] S2 focuses the second pulse laser onto the preset peeling surface inside the silicon carbide ingot and performs a second laser scan along the preset laser scanning path, decreasing the spacing between modified particles to form multiple continuous modified particles on the preset peeling surface. An overlapping area is formed between at least two adjacent continuous modified particles on the same laser scanning line, and a crack is formed in the overlapping area that extends two-dimensionally along the cleavage surface of the silicon carbide ingot and passes through discrete modified particles and adjacent laser scanning lines, thus obtaining a continuous modified layer.

[0069] S3 peels off the silicon carbide ingot along the preset peeling surface to obtain the wafer and the remaining ingot.

[0070] Example 3: This invention discloses a controllable crack laser ablation method for silicon carbide, which differs from Example 2 in that, in S1 and S2, the laser scanning paths for the first and second laser scans are the same, and the laser scanning path is controlled to be approximately perpendicular to the silicon carbide ingot. The crystal orientation, and the direction of the laser scanning path used to form continuous modified particles is the direction that can extend downward along the cleavage plane of the silicon carbide ingot to form cracks.

[0071] Reference Figure 2 and Figure 3 The specific implementation principle of this invention is as follows:

[0072] 1) In S1, a first pulse laser is used to scan along a preset stripping path, forming multiple sets of discrete modified particles with uniform depth and separation within the silicon carbide ingot. These discrete modified particles are located perpendicular to the... The directional arrangement of the crystals together forms a modification depth interception layer, which limits the depth range of subsequent modification processing and ensures that the modification depth of the entire ingot is uniform.

[0073] 2) In S2, a second pulse laser is used to perform a second scan along the same preset peeling path to reduce the spacing between modified points, so that at least two adjacent continuous modified points are connected to each other, i.e., points are connected to form a line, forming a continuous modified layer; at the same time, by controlling the processing direction, the crack can extend laterally and obliquely downward along the cleavage plane, guiding the laser-induced microcracks to extend in an orderly two-dimensional manner along the cleavage plane, avoiding the disorderly extension of cracks or upward penetration into the near-surface area of ​​the ingot, thus realizing the controllable peeling of silicon carbide ingots;

[0074] 3) The interception effect of the first pulse laser: The large spacing between the modified points processed by the first pulse laser can ensure that the processing depth of each point is basically consistent and does not interfere with each other. These discrete modified points with uniform depth serve as a modified depth interception layer, which can effectively constrain the modified depth of the second pulse laser, accurately control the formation position and thickness of the continuous modified layer, and ensure the uniformity and consistency of the continuous modified layer on the entire wafer, making the subsequent wafer stripping process more controllable and stable.

[0075] 4) Orientation constraints of processing direction and crystal orientation / cleavage plane: the scanning paths of the first and second pulse lasers are approximately perpendicular to the crystal orientation / cleavage plane. The crystal orientation, and the second pulse laser must be processed along the direction extending downwards from the cleavage plane (i.e., path ②); among which,

[0076] If along with Laser scanning path processing with crystal orientation parallel, starting from a direction parallel to the silicon carbide ingot. Looking at the crystal orientation, the modified particles on adjacent laser scanning lines are located on different cleavage planes. After these modified particles extend obliquely along their respective cleavage planes, they are difficult to connect with each other to form a two-dimensional continuous crack, which ultimately leads to adverse effects such as peeling failure, uneven thickness, or increased removal amount.

[0077] If the laser scanning path (i.e., path ①) is used for processing, the crack induced by the second pulse laser will extend upwards disorderly under the anisotropy of the cleavage plane. The crack located above the modification depth interception layer will shield the depth constraint effect of the modification depth interception layer and eventually extend to the near-surface area of ​​the silicon carbide ingot, resulting in disordered crack extension and uncontrolled modification depth. This will cause damage marks after the wafer is ground after peeling, which will greatly reduce the product qualification rate.

[0078] If the laser scanning path (i.e., path ②) forms an acute angle with the cleavage plane, only by adopting the path setting and processing direction of this embodiment can the crack extend downward along the cleavage plane and pass through the pre-formed discrete modification points. This will not interfere with the depth interception effect of the modification depth interception layer, ensuring that the crack is two-dimensionally connected in the entire preset peeling surface area, while avoiding the crack from damaging the near-surface of the ingot. This ensures the orderliness and controllability of the modification depth, preventing the crack from extending upward to the near-surface of the ingot and causing damage. Ultimately, a silicon carbide wafer with good uniformity and no surface damage is obtained, improving the surface quality and yield of the wafer after grinding.

[0079] Examples 4-8: This invention discloses a controllable crack silicon carbide laser ablation method. The difference from Example 3 is that in S1 and S2, the laser parameters of the first laser scan meet the conditions in Table 1, and the laser parameters of the second laser scan meet the conditions in Table 2, so that the distance between the modified particles in the two laser scans is 1~40μm and decreases with the number of scans, the laser pulse width of the two laser scans is 0.0001~30ns and increases with the number of scans, and the laser single pulse energy of the two laser scans is 10~150μJ and decreases with the number of scans.

[0080] Table 1

[0081]

[0082] Table 2

[0083]

[0084] Comparative Example

[0085] Comparative Example 1: This is a controlled crack laser ablation method for silicon carbide disclosed in this invention. The difference from Example 6 is that in S1 and S2, the laser scanning paths for the first and second laser scans are the same, and the laser scanning path is controlled to be approximately perpendicular to the silicon carbide ingot. The crystal orientation, and the direction of the laser scanning path used to form continuous modified particles is the direction that can extend upward along the cleavage plane of the silicon carbide ingot to form cracks (i.e., path ①).

[0086] Comparative Example 2: This is a controlled crack laser ablation method for silicon carbide disclosed in this invention. The difference from Example 8 is that in S1 and S2, the laser scanning paths for the first and second laser scans are the same, and the laser scanning path is controlled to be approximately perpendicular to the silicon carbide ingot. The crystal orientation, and the direction of the laser scanning path used to form continuous modified particles is the direction that can extend upward along the cleavage plane of the silicon carbide ingot to form cracks (i.e., path ①).

[0087] Performance testing

[0088] Experimental Example 1: Microscopic image detection of the continuous modified layer was performed on the ingots obtained by S2 in Examples 6, 8, and Comparative Examples 1-2. The detection results are as follows: Figure 4 As shown.

[0089] from Figure 4 As can be seen, since Comparative Examples 1 and 2 are processed using path ①, their cracks extend upwards disorderly and directly into the ingot region above the modification depth interception layer. They are not effectively constrained by the modification depth interception layer, resulting in disordered crack extension, uncontrolled modification depth, and even the absence of continuous cracks. This can easily lead to damage marks on the wafers after peeling and grinding, significantly reducing the product qualification rate. In contrast, Examples 6 and 8 are processed using path ② of the present invention, where the cracks extend downwards stably along the cleavage plane and are always confined within the preset peeling surface range. The modification depth is uniform, and there is no phenomenon of disordered upward extension.

[0090] Experimental Example 2: Microscopic image inspection of the peeled surface was performed on the wafer and remaining ingot obtained in S3 of Example 6. The inspection results are as follows: Figure 5 As shown.

[0091] from Figure 5 It can be seen that Example 6 is based on approximately perpendicular to Laser scanning is performed along the crystal orientation, starting from the direction parallel to the silicon carbide ingot. Looking at the crystal orientation, the modified particles on adjacent laser scanning lines are approximately at the same height on the cleavage plane. After the modified particles extend laterally along the preset peeling surface, they pass through the adjacent laser scanning lines, ensuring that the crack is two-dimensionally connected throughout the entire preset peeling surface region.

[0092] Experimental Example 3: The apparent performance of the wafers obtained in S3 of Examples 4-8 and Comparative Examples 1-2 was tested, and the test results are shown in Table 3.

[0093] Table 3

[0094]

[0095] As can be seen from Table 3, the wafers peeled off in Examples 4 to 8 have a smaller TTV on the peeled surface, higher surface flatness, and the amount removed (damaged layer thickness) is about 15 to 20 μm lower than that in the comparative examples. This can significantly reduce the risk of residual traces after wafer thinning and polishing, and improve the wafer processing qualification rate.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for laser ablation of silicon carbide with controllable cracks, characterized in that: The process includes the following steps: First, a pulsed laser is focused onto a preset peeling surface inside a silicon carbide ingot, and at least two laser scans are repeated along a preset laser scanning path. At least one laser parameter of the at least two laser scans is adjusted so that the spacing between the modified particles decreases with the number of scans, thereby sequentially forming multiple discrete modified particles and multiple continuous modified particles on the preset peeling surface. An overlapping region is formed between at least two adjacent continuous modified particles on the same laser scanning line. Then, a crack is formed in the overlapping region that extends two-dimensionally along the cleavage plane of the silicon carbide ingot and passes through the discrete modified particles and adjacent laser scanning lines. Finally, the silicon carbide ingot is peeled off along the preset peeling surface to obtain a wafer and the remaining ingot.

2. The method for laser ablation of silicon carbide with controllable cracks according to claim 1, characterized in that: During the laser scanning process, the laser scanning path is controlled to be approximately perpendicular to the silicon carbide ingot. The crystal orientation, and the direction of the laser scanning path used to form continuous modified particles is the direction that can extend downward along the cleavage plane of the silicon carbide ingot to form cracks.

3. The method for laser ablation of silicon carbide with controllable cracks according to claim 2, characterized in that: During the laser scanning process, the distance between the modified particles in at least two laser scans is controlled to be between 1 and 40 μm and decreases with the number of scans.

4. The method for laser ablation of silicon carbide with controllable cracks according to claim 2, characterized in that: During the laser scanning process, the laser pulse width for at least two laser scans increases with the number of scans.

5. The method for laser ablation of silicon carbide with controllable cracks according to claim 4, characterized in that: During the laser scanning process, the laser pulse width of at least two laser scans is controlled to be between 0.0001 and 30 ns and increases with the number of scans.

6. The method for laser ablation of silicon carbide with controllable cracks according to claim 2, characterized in that: During the laser scanning process, the energy of the laser single pulse for at least two laser scans decreases with the number of scans.

7. The method for laser ablation of silicon carbide with controllable cracks according to claim 6, characterized in that: During the laser scanning process, the laser single pulse energy of at least two laser scans is controlled to be between 10 and 150 μJ and decreases with the number of scans.

8. A method for laser ablation of silicon carbide with controllable cracks according to any one of claims 1 to 7, characterized in that: Includes the following steps, S1 focuses the first pulse laser onto a preset peeling surface inside a silicon carbide ingot and performs a first laser scan along a preset laser scanning path to form multiple discrete modified points on the preset peeling surface, thereby obtaining a modified depth interception layer. S2 focuses the second pulse laser onto a preset peeling surface inside the silicon carbide ingot and performs a second laser scan along a preset laser scanning path, decreasing the spacing between modified particles to form multiple continuous modified particles on the preset peeling surface. An overlapping region is formed between at least two adjacent continuous modified particles on the same laser scanning line, and a crack is formed in the overlapping region that extends two-dimensionally along the cleavage surface of the silicon carbide ingot and passes through the discrete modified particles and adjacent laser scanning lines, thus obtaining a continuous modified layer. S3 peels off the silicon carbide ingot along the preset peeling surface to obtain a wafer and the remaining ingot.

9. The method for laser ablation of silicon carbide with controllable cracks according to claim 8, characterized in that: In S1, the laser parameters of the first laser scan satisfy at least one of the following conditions: Laser wavelength: 500~1100nm; Modified particle spacing: 10~40μm Pulse width: 0.0001~20ns; Focal spot diameter: 0.5~3.0μm; Numerical aperture of the condenser lens: 0.4~0.

9.

10. The method for laser ablation of silicon carbide with controllable cracks according to claim 8, characterized in that: In S2, the laser parameters of the second laser scan satisfy at least one of the following conditions: Laser wavelength: 500~1100nm; Modified particle spacing: 1~10μm Pulse width: 5~30ns; Focal spot diameter: 0.5~3.0μm; Numerical aperture of the condenser lens: 0.4~0.9.

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