A method for producing a silicon carbide wafer

Abstract

The present application provides a method for producing silicon carbide wafer, which adds a step of immersing the silicon carbide wafer in a chemical solution to corrode the modified layer interface of the silicon carbide wafer after the silicon carbide wafer is peeled from a silicon carbide ingot and before the silicon carbide wafer is ground. By using the chemical solution to corrode the modified layer interface of the silicon carbide wafer, the defects such as residual stress, dislocation and crack generated in the peeling step of the silicon carbide wafer can be removed. Then the modified layer interface of the silicon carbide wafer is ground. Since there is no or less residual stress on the modified layer interface of the silicon carbide wafer at this time, the phenomenon that the extrusion of the grinding process increases the residual stress and causes the crack to continue to grow can be slowed down, so that less material can be ground to completely remove the damage layer, the loss of the ingot is reduced, and the quality of the wafer is improved. Moreover, the difficulty of subsequent grinding is reduced, and the grinding efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide ingot technology, and more particularly to a method for producing silicon carbide wafers. Background Technology

[0002] Silicon carbide (SiC) is a third-generation semiconductor material developed after silicon, germanium, and arsenic. It possesses advantages such as a wide bandgap, good thermal conductivity, and high carrier mobility, making it a core material for manufacturing wide-bandgap semiconductor devices. It also has broad application prospects in high-temperature resistant, radiation-resistant, high-frequency, high-power devices. Silicon carbide wafers for forming devices are typically produced by wire cutting, slicing silicon carbide ingots at a specific offset angle. In this wire cutting process, diamond wire with a diameter of approximately 100–300 μm is fed in a certain direction to obtain silicon carbide wafers. However, after slicing the silicon carbide ingot using wire cutting, the front and back sides of the wafers need to be ground, resulting in a waste of 70–80% of the silicon carbide ingot, leading to poor economic efficiency. Furthermore, due to the high Mohs hardness of silicon carbide ingots, wire cutting causes severe wear on the diamond wire and is time-consuming, resulting in poor productivity.

[0003] Laser cutting is a novel method for producing silicon carbide wafers, potentially replacing the traditional diamond wire cutting method. This method focuses a laser beam of wavelength transparent to a silicon carbide ingot onto the interior of the ingot. Through scanning irradiation, a high-density modified layer and cracks are formed on a cutting surface at a predetermined depth parallel to the silicon carbide ingot's base plane. Then, external force is applied to separate the modified layer and cracks along the cutting surface, yielding a silicon carbide wafer. This method offers low cutting loss and high processing efficiency. However, the laser processing causes localized plastic deformation due to temperature gradients, resulting in high-density dislocations and significant residual stress in the modified layer and crack growth areas. In the subsequent grinding process, the large residual stress at the modified layer interface promotes further crack growth into the material, requiring more material to be ground to completely remove the damaged layer, resulting in significant material loss. Summary of the Invention

[0004] This invention provides a method for generating silicon carbide wafers, which reduces the phenomenon that the residual stress caused by the extrusion of the grinding process increases and thus causes cracks to continue to grow. This allows for the complete removal of the damaged layer with less material, reducing ingot loss and improving wafer quality.

[0005] This invention provides a method for generating a silicon carbide wafer, comprising: providing a silicon carbide ingot to be cut; forming a modified layer at a predetermined depth on the silicon carbide ingot using a laser stealth processing technology; peeling off a portion of the silicon carbide ingot using a rotation or stretching method, with the modified layer as an interface, to form a silicon carbide wafer; immersing the silicon carbide wafer in a chemical solution to etch the modified layer interface of the silicon carbide wafer; and grinding the modified layer interface of the silicon carbide wafer.

[0006] In the above-described scheme, after the silicon carbide wafer is separated from the silicon carbide ingot and before grinding, a step is added to immerse the silicon carbide wafer in a chemical solution to etch the modified layer interface. This etching removes residual stress, dislocations, and cracks generated during the wafer separation process. Subsequent grinding of the modified layer interface, where there is little or no residual stress, prevents defects from multiplying during grinding, mitigating the stress buildup and crack propagation caused by the grinding process. This allows for complete removal of the damaged layer with less material, reducing ingot loss and improving wafer quality. Furthermore, the smoother surface of the modified layer after chemical etching reduces the difficulty of subsequent grinding and increases grinding efficiency.

[0007] In one specific implementation, the chemical solution is a strong alkaline solution, which facilitates the preparation of the chemical solution.

[0008] In one specific embodiment, the strong alkaline solution is a potassium hydroxide solution, a sodium hydroxide solution, or a mixture of potassium hydroxide and sodium hydroxide, which simplifies the difficulty of obtaining the strong alkaline solution.

[0009] In one specific embodiment, the strong alkaline solution is a potassium hydroxide solution or a mixture of potassium hydroxide and sodium hydroxide, wherein the mass fraction of the potassium hydroxide solution is 20% to 40%, which improves the removal effect of residual stress, dislocations and cracks generated during the silicon carbide wafer stripping step.

[0010] In one specific embodiment, the strong alkaline solution is a sodium hydroxide solution or a mixture of potassium hydroxide and sodium hydroxide, wherein the mass fraction of the sodium hydroxide solution is 20% to 40%, which improves the removal effect of residual stress, dislocations and cracks generated during the silicon carbide wafer stripping step.

[0011] In one specific implementation, the chemical solution is a strong acid solution, which facilitates the preparation of the chemical solution.

[0012] In one specific embodiment, the strong acid solution is a hydrofluoric acid solution, a nitric acid solution, or a mixture of hydrofluoric acid and nitric acid, which simplifies the difficulty of obtaining a strong alkali solution.

[0013] In one specific embodiment, the strong acid solution is a hydrofluoric acid solution or a mixture of hydrofluoric acid and nitric acid, with the mass fraction of the hydrofluoric acid solution being 35% to 40%, which improves the removal effect of residual stress, dislocations, cracks, and other defects generated during the silicon carbide wafer stripping step.

[0014] In one specific embodiment, the strong acid solution is a hydrofluoric acid solution or a mixture of hydrofluoric acid and nitric acid, with the nitric acid solution having a mass fraction of 60% to 70%, which improves the removal effect of residual stress, dislocations, cracks, and other defects generated during the silicon carbide wafer stripping step.

[0015] In one specific implementation, forming a modified layer at a predetermined depth in a silicon carbide ingot using laser stealth processing includes: providing a laser beam with an energy density greater than the silicon carbide ablation threshold; focusing the laser beam at the predetermined depth within the silicon carbide ingot and scanning within the predetermined depth, causing the single-crystal silicon carbide at the depth to decompose into silicon and carbon, thereby forming the modified layer at the predetermined depth. By decomposing the silicon carbide at the interface of the modified layer into silicon and carbon, the difficulty of subsequent chemical etching of the modified layer interface is reduced. Attached Figure Description

[0016] Figure 1 A flowchart illustrating a method for generating a silicon carbide wafer according to an embodiment of the present invention;

[0017] Figure 2 A flowchart illustrating another method for generating silicon carbide wafers according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] To facilitate understanding of the silicon carbide wafer fabrication method provided in this embodiment of the invention, the application scenario of this method is first described below. This method is applied to the process of cutting silicon carbide wafers from silicon carbide ingots and processing them into silicon carbide wafers that meet the requirements. The method for fabricating silicon carbide wafers will now be described in detail with reference to the accompanying drawings.

[0020] refer to Figure 1 and Figure 2 The method for generating silicon carbide wafers provided in this embodiment of the invention includes:

[0021] Step 10: Provide silicon carbide ingots to be cut;

[0022] Step 20: Using laser stealth processing technology, a modified layer is formed at a set depth in the silicon carbide ingot;

[0023] Step 30: Using rotation or stretching, with the modified layer as the interface, a portion of the silicon carbide ingot is peeled off to form a silicon carbide wafer;

[0024] Step 40: Immerse the silicon carbide wafer in a chemical solution to etch the interface of the modified layer of the silicon carbide wafer;

[0025] Step 50: Grind the interface of the modified layer of the silicon carbide wafer.

[0026] In the above scheme, after the silicon carbide wafer is peeled from the silicon carbide ingot and before grinding, a step is added to immerse the silicon carbide wafer in a chemical solution to etch the modified layer interface of the silicon carbide wafer. Etching the modified layer interface with a chemical solution removes residual stress, dislocations, cracks, and other defects generated during the wafer peeling process. Then, grinding the modified layer interface of the silicon carbide wafer is performed. Since there is no residual stress or very little residual stress on the modified layer interface at this point, the pressure from the grinding process can be reduced, thus mitigating the increase in residual stress and preventing crack propagation. This avoids the proliferation of defects during the grinding process, allowing for the complete removal of the damaged layer with less material, reducing ingot loss, and improving wafer quality. Furthermore, the modified layer interface etched with a chemical solution has better flatness, reducing the difficulty of subsequent grinding and improving grinding efficiency. The following is a detailed description of each step with reference to the accompanying drawings.

[0027] First, refer to Figure 1 Provide silicon carbide ingots to be cut, the shape of which can be prismatic or cylindrical.

[0028] Next, as Figure 1 and Figure 2As shown, a laser stealth processing technique is used to form a modified layer at a predetermined depth on a silicon carbide ingot. Specifically, a laser beam is passed through the end face of the silicon carbide ingot and focused at the predetermined depth. The beam then scans at this depth, forming the modified layer. The predetermined depth is specifically related to the thickness of the silicon carbide wafer to be cut. Furthermore, the modified layer can be parallel to the base surface of the entire silicon carbide ingot to minimize waste.

[0029] In the specific application of laser stealth processing to form a modified layer at a predetermined depth in a silicon carbide ingot, a laser beam is first provided. The laser energy density of this beam is greater than the silicon carbide ablation threshold. The laser energy density is related to the crystal state of the modified layer after modification; that is, different laser energy densities can produce monocrystalline silicon or amorphous silicon at the predetermined depth. Then, the laser beam is focused on the predetermined depth within the silicon carbide ingot. When the laser energy density at the focal point exceeds the silicon carbide ablation threshold, the material temperature rises sharply, and the silicon carbide decomposes under high temperature conditions, generating amorphous silicon, monocrystalline silicon, or a mixture of both, as well as carbon. The specific type of amorphous silicon or monocrystalline silicon is determined by the laser energy density; higher laser energy generates monocrystalline silicon, while lower laser energy generates amorphous silicon. Furthermore, the laser beam is focused and scanned at the predetermined depth, causing the monocrystalline silicon carbide at the predetermined depth to decompose into silicon and carbon, thus forming the modified layer at the predetermined depth. By decomposing the silicon carbide at the interface of the modified layer into silicon and carbon, the difficulty of subsequent chemical etching of the modified layer interface is reduced. Unlike silicon carbide, the modified layer formed after modification has high corrosion resistance. The amorphous silicon and monocrystalline silicon at the modified layer location can be etched by strong alkaline solutions (such as potassium hydroxide or sodium hydroxide solutions) or strong acid solutions (hydrofluoric acid or nitric acid) to remove residual stress on the modified layer interface.

[0030] Specifically, the laser stealth processing technology shown below can be used to form a modified layer at a set depth in a silicon carbide ingot.

[0031] The focus of an ultrashort pulse laser beam is focused on a predetermined depth layer position of a silicon carbide ingot to generate a void modification formation region and a crack modification formation region above the predetermined depth layer position, respectively; wherein, the void modification formation region is located between the predetermined depth layer position and the crack modification formation region.

[0032] The focus of the ultrashort pulse laser beam is controlled to scan at a set depth layer of the silicon carbide ingot, so as to form a void modification layer and a crack modification layer above the set depth layer. The void modification layer is composed of multiple void modification forming regions, and the crack modification layer is composed of multiple crack modification forming regions. The void modification layer is located between the set depth layer and the crack modification layer.

[0033] By focusing the short-pulse laser beam on the crack modification formation region, scattering perpendicular to the direction of the short-pulse laser beam is generated, causing the cracks in the crack modification formation region to grow laterally outward.

[0034] The focus of the short-pulse laser beam is controlled to scan the crack-modified layer, so that cracks in any adjacent crack-modified formation regions in the crack-modified layer are connected together through lateral growth.

[0035] In the above scheme, an ultrashort pulse laser is first used, with the focal point of the ultrashort pulse laser beam focused at a predetermined depth layer position on the silicon carbide ingot. This creates void modification and crack modification formation regions above the predetermined depth layer position. The focal point of the ultrashort pulse laser beam is controlled to scan within the predetermined depth layer of the silicon carbide ingot, forming void modification and crack modification layers. After ultrashort pulse laser hidden cutting, a short pulse laser is used, with the focal point of the short pulse laser beam moved a certain range above the predetermined depth layer. This allows the focal point of the short pulse laser beam to be focused on the crack modification formation region, so that the heat of the short pulse laser beam mainly acts on the crack modification formation region, producing scattering perpendicular to the direction of the short pulse laser beam. This causes cracks within the crack modification formation region to grow laterally outward. The focal point of the short pulse laser beam is controlled to scan within the crack modification layer, so that cracks in any adjacent crack modification formation regions within the crack modification layer can be connected together through lateral growth.

[0036] Compared to existing laser-cut silicon ingot processes, this new method utilizes an ultrashort pulse laser. This laser can create void and crack modification regions above the focal point of the ultrashort pulse laser beam at a predetermined depth. Scanning then forms separate void and crack modification layers, refining and differentiating the modification layers compared to existing technologies. Furthermore, when using a short pulse laser beam, the focal point is focused on the crack modification region. This short pulse laser focal point is positioned above the ultrashort pulse laser beam focal point, rather than at the same depth as in existing technologies. This generates scattering perpendicular to the short pulse laser beam direction, causing cracks within the crack modification region to grow laterally outwards. Scanning further allows any adjacent cracks within the crack modification region to connect laterally through this lateral growth. This involves refining the modified layer into a void modified layer and a crack modified layer. Then, a short-pulse laser beam is focused on the crack modified layer. The focal point of the short-pulse laser beam is designed more accurately and rationally, resulting in smaller fluctuations in the vertical height difference of the focal point (since the vertical height difference of the crack modified layer is always smaller than the vertical height difference of the modified layer formed by the crack and void modified layers). Furthermore, optimizing the focal point of the short-pulse laser beam from the modified layer to the crack modified layer reduces the amount and length of cracks extending longitudinally along the silicon carbide ingot within the modified layer. This allows more laser energy to be applied to the transverse outward growth of cracks, increasing the number and length of transverse cracks. This enables the cutting of thinner silicon carbide wafers and reduces cutting loss. More silicon carbide wafers can be cut from the same ingot, reducing waste.

[0037] Of course, other laser stealth processing techniques can also be used to form a modified layer at a predetermined depth in a silicon carbide ingot. For example, the following process can also be used to form a modified layer at a predetermined depth in a silicon carbide ingot.

[0038] Step 1: A first laser beam is used to illuminate the silicon carbide ingot from the side, forming a heated optical path at a predetermined depth within the silicon carbide ingot, so that the silicon carbide material on the optical path has a gradually decreasing longitudinal temperature gradient along the propagation direction of the optical path.

[0039] Step 2: A second laser beam is incident from the end face of the silicon carbide ingot and focused on the optical path at a set depth layer position to form a burst point, so as to modify the silicon carbide material on the optical path;

[0040] Step 3: Control the focus of the second laser beam to scan along the propagation direction of the optical path or in the opposite direction of the propagation direction, so as to perform detonation modification on the silicon carbide material at other positions of the optical path to form a cutting path; and the longitudinal temperature gradient can induce cracks at each detonation point to grow in the optical path along a direction parallel to the optical path.

[0041] Step 4: Following the method in Step 1, move the first laser beam to form another new heating optical path at other locations within the silicon carbide ingot at a predetermined depth layer;

[0042] Step 5: Following the methods in Step 2 and Step 3, focus the second laser beam on the new optical path and perform bursting and scanning on the new optical path to form a cutting path at the new optical path position;

[0043] Step Six: Following the methods in Steps Four and Five, multiple cleavage channels are formed at a predetermined depth within the silicon carbide ingot; and cracks on adjacent cleavage channels can grow and connect together in a direction perpendicular to the optical path to form a modified layer at the predetermined depth.

[0044] By employing a first laser beam incident from the side of a silicon carbide ingot and forming a heated optical path at a predetermined depth, while a second laser beam is focused on the optical path formed by the first laser beam and scans for crack points along this path, the gradually decreasing longitudinal temperature gradient within the optical path formed by the first laser beam can be utilized to induce cracks at each crack point to grow in a direction parallel to the optical path. This increases the length of cracks growing in the direction parallel to the optical path at the crack point, facilitating the rapid extension and connection of cracks between adjacent crack points on the same cutting track, thus simplifying the process of connecting cracks at adjacent crack points on the same cutting track. In application, the spacing between different crack points on the same cutting track can be appropriately widened, allowing for scanning of cutting tracks of the same length using fewer crack points, thereby improving scanning efficiency. In the stripping method described in this application, the first laser beam and the second laser beam can be applied simultaneously. The first laser beam is incident from the side of the silicon carbide ingot and is mainly used to form a heating optical path at a set depth layer position on the silicon carbide ingot. Utilizing the law that the energy of the laser beam gradually decreases as the silicon carbide material absorbs energy during propagation within the silicon carbide ingot, the silicon carbide material on the optical path has a gradually decreasing longitudinal temperature gradient along the propagation direction of the optical path. The second laser beam is incident from the end face of the silicon carbide ingot to perform a stealth cutting process on the silicon carbide material on the optical path. During this process, the longitudinal temperature gradient on the optical path can induce cracks at each burst point to grow in a direction parallel to the optical path within the optical path, increasing the length of the cracks at the burst point growing in the direction parallel to the optical path. This allows cracks between two adjacent burst points on the same cutting path to extend and connect quickly, thereby simplifying the difficulty of connecting cracks between adjacent burst points on the same cutting path. Because the two laser beams operate simultaneously, and the first laser beam does not require a multi-point scanning process, the equipment complexity of the first laser beam system can be simplified. The second laser beam can appropriately widen the spacing between different points on the same cutting path, thus allowing the same length of cutting path to be scanned with fewer points, improving scanning efficiency, increasing processing efficiency, and saving processing costs. During the formation of a complete modified layer on a silicon carbide ingot, the first laser beam only needs to move multiple times to form multiple heating optical paths, eliminating the need for a multi-point scanning process and further simplifying the equipment complexity of the first laser beam system.

[0045] The first laser beam can be a parallel beam or a Bessel beam. The light intensity on the cross-section of the optical path can undulate in a wave-like manner from the center of the first laser beam to its edge, thereby creating a transverse temperature gradient with fluctuating temperature on the cross-section of the optical path. This transverse temperature gradient can induce cracks generated at each burst point to grow laterally within the optical path in a direction perpendicular to the optical path. By using a Bessel beam as the first laser beam, not only can the cross-sectional size of the first laser beam be reduced, making it easier to form a better-distributed longitudinal temperature gradient in an optical path with a smaller cross-section, but also the characteristic of the Bessel beam—that the light intensity on the beam cross-section fluctuates in a wave-like manner from the center to the edge of the first laser beam—can be utilized to form a transverse temperature gradient with fluctuating temperature on the cross-section of the optical path. This transverse temperature gradient can induce cracks generated at each burst point to grow laterally within the optical path in a direction perpendicular to the optical path, increasing the length of the cracks at the burst point growing in the direction perpendicular to the optical path. This facilitates the rapid transverse growth and connection of cracks on adjacent cutting paths, thereby appropriately widening the spacing between adjacent cutting paths. Within a silicon carbide ingot of the same size, the formation of the modification layer can be completed by emitting fewer optical paths, improving processing efficiency.

[0046] Next, refer to Figure 1 and Figure 2 By using rotation or stretching methods, with the modified layer as the interface, a portion of the silicon carbide ingot is peeled off to form a silicon carbide wafer.

[0047] Specifically, a portion of a silicon carbide ingot can be peeled off using a modified layer as an interface, forming a silicon carbide wafer. In practice, the silicon carbide ingot above the modified layer can be fixed, while the silicon carbide ingot below the modified layer can rotate clockwise or counterclockwise; alternatively, the silicon carbide ingot above the modified layer can rotate clockwise, while the silicon carbide ingot below the modified layer rotates counterclockwise. This allows for opposite rotation between the silicon carbide ingots above and below the modified layer, generating torsional stress within the silicon carbide ingot. Because the material at the modified layer location has been modified and exhibits crack propagation, the torsional stress intensity at the modified layer interface is lower than at other locations, thus enabling the peeling off of a portion of the silicon carbide ingot using the modified layer as an interface to form a silicon carbide wafer.

[0048] Alternatively, a stretching method can be used, with the modified layer as the interface, to peel off a portion of the silicon carbide ingot to form a silicon carbide wafer. In this process, the silicon carbide ingot below the modified layer can be fixed, and the upper end face of the ingot can be stretched, generating tensile stress within the ingot. Because the material at the modified layer location has already been modified and exhibits crack propagation, the tensile stress intensity at the modified layer interface is lower than at other locations, thus enabling the peeling off of a portion of the silicon carbide ingot using the modified layer as the interface to form a silicon carbide wafer.

[0049] Next, continue to refer to Figure 1 and Figure 2 The process involves immersing the silicon carbide wafer in a chemical solution to etch the modified layer interface. After the silicon carbide wafer is separated from the ingot and before grinding, this step of immersing it in a chemical solution to etch the modified layer interface removes residual stress, dislocations, and cracks generated during the wafer separation process. Subsequent grinding of the modified layer interface, where there is little or no residual stress, mitigates the stress buildup caused by grinding, preventing further crack growth and thus reducing the need for material removal. This allows for more material to be removed, minimizing ingot loss and improving wafer quality. Furthermore, the chemically etched modified layer interface exhibits better smoothness, reducing the difficulty of subsequent grinding and increasing grinding efficiency.

[0050] It needs to be explained that when the silicon carbide ingot to be cut is a single, complete silicon carbide ingot, both the upper and lower surfaces of the ingot are unmodified single-crystal silicon carbide structures. In this case, the silicon carbide wafer peeled off in the first cut has only one end face as a modified layer interface, and only the modified layer interface on the silicon carbide wafer needs to be chemically etched. However, if the provided silicon nitride ingot to be cut has already been cut into one or more silicon carbide wafers or blocks, at least one of the upper and lower surfaces of the silicon carbide ingot is a modified layer interface, meaning that at least one of the upper and lower surfaces of the silicon carbide ingot is no longer an unmodified single-crystal silicon carbide structure. In this case, the silicon carbide wafer peeled off may not have a modified layer interface on either the upper or lower surface, and both need to be chemically etched.

[0051] When preparing the above-mentioned chemical solution, the chemical solution can be a strong alkaline solution, which is convenient to obtain. Specifically, when choosing a strong alkaline solution, it can be a potassium hydroxide solution, a sodium hydroxide solution, or a mixture of potassium hydroxide and sodium hydroxide, simplifying the process of obtaining the strong alkaline solution.

[0052] When the strong alkaline solution is a potassium hydroxide solution or a mixture of potassium hydroxide and sodium hydroxide, the mass fraction of the potassium hydroxide solution can be 20% to 40%. Specifically, the mass fraction of the potassium hydroxide solution can be any value between 20% and 40%, such as 20%, 25%, 30%, 35%, or 40%, to improve the removal effect of residual stress, dislocations, cracks, and other defects generated during the silicon carbide wafer stripping step.

[0053] In addition, when the strong alkaline solution is a sodium hydroxide solution or a mixture of potassium hydroxide and sodium hydroxide, the mass fraction of the sodium hydroxide solution can be 20% to 40%. Specifically, the mass fraction of the sodium hydroxide solution can be any value between 20% and 40%, such as 20%, 25%, 30%, 35%, and 40%, which improves the removal effect of residual stress, dislocations, cracks, and other defects generated during the silicon carbide wafer stripping step.

[0054] Of course, the chemical solutions mentioned above can also be strong acid solutions, which facilitates the preparation of chemical solutions. Specifically, when choosing a strong acid solution, it can be a hydrofluoric acid solution, a nitric acid solution, or a mixture of hydrofluoric acid and nitric acid, simplifying the preparation of strong alkali solutions.

[0055] When the strong acid solution is a hydrofluoric acid solution or a mixture of hydrofluoric acid and nitric acid, the mass fraction of the hydrofluoric acid solution can be 35% to 40%. Specifically, the mass fraction of the hydrofluoric acid solution can be any value between 35% and 40%, such as 35%, 36%, 37%, 38%, 39%, or 40%, to improve the removal effect of residual stress, dislocations, cracks, and other defects generated during the silicon carbide wafer stripping step.

[0056] In addition, when the strong acid solution is a hydrofluoric acid solution or a mixture of hydrofluoric acid and nitric acid, the mass fraction of the nitric acid solution can be 60% to 70%. Specifically, the mass fraction of the nitric acid solution can be any value between 60% and 70%, such as 60%, 62%, 64%, 66%, 68%, 70%, etc., which improves the removal effect of residual stress, dislocations and cracks generated in the silicon carbide wafer stripping step.

[0057] Next, refer to Figure 1 and Figure 2The interface of the modified layer on the silicon carbide wafer is ground. Alternatively, the chemically etched silicon carbide wafer can be cleaned first, followed by coarse grinding, fine grinding, and chemical polishing on both sides to completely remove the damaged layer at the interface of the upper and lower modified layers. This results in a silicon carbide wafer with no damaged layer or residual stress on the surface or subsurface, yielding a high-performance silicon carbide wafer. Because the modified layer interface of the silicon carbide wafer has little or no residual stress at this point, it mitigates the stress buildup caused by the grinding process, which can lead to increased residual stress and crack growth. This avoids defect proliferation during the grinding process, allowing for the removal of the damaged layer with less material, reducing ingot loss, and improving wafer quality. Furthermore, the smoothness of the modified layer interface after chemical etching is better, reducing the difficulty of subsequent grinding and improving grinding efficiency.

[0058] In the various embodiments described above, after the silicon carbide wafer is peeled from the silicon carbide ingot and before grinding the silicon carbide wafer, a step is added to immerse the silicon carbide wafer in a chemical solution to etch the modified layer interface of the silicon carbide wafer. By using a chemical solution to etch the modified layer interface of the silicon carbide wafer, defects such as residual stress, dislocations, and cracks generated during the silicon carbide wafer peeling step can be removed. Afterwards, the modified layer interface of the silicon carbide wafer is ground. Since there is no residual stress or very little residual stress on the modified layer interface at this point, the pressure from the grinding process can be reduced, which can increase residual stress and cause cracks to continue to grow. This avoids the proliferation of defects during the grinding process, thus allowing less material to be ground to completely remove the damaged layer, reducing ingot loss and improving wafer quality. Moreover, the modified layer interface after chemical etching has better flatness, which reduces the difficulty of subsequent grinding and improves grinding efficiency.

[0059] 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 variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing silicon carbide wafers, characterized in that, include: Provide silicon carbide ingots to be cut; A modified layer is formed at a predetermined depth in the silicon carbide ingot using laser stealth processing technology. By using rotation or stretching, with the modified layer as the interface, a portion of the silicon carbide ingot is peeled off to form a silicon carbide wafer; The silicon carbide wafer is immersed in a chemical solution to etch the interface of the modified layer of the silicon carbide wafer. The interface of the modified layer of the silicon carbide wafer is polished; The process of forming a modified layer at a predetermined depth in the silicon carbide ingot using laser stealth processing includes: Step 1: A first laser beam is used to illuminate the silicon carbide ingot from the side, forming a heated optical path at a predetermined depth within the silicon carbide ingot, so that the silicon carbide material on the optical path has a gradually decreasing longitudinal temperature gradient along the propagation direction of the optical path. Step 2: A second laser beam is incident from the end face of the silicon carbide ingot and focused on the optical path at a set depth layer position to form a burst point, so as to modify the silicon carbide material on the optical path; Step 3: Control the focus of the second laser beam to scan along the propagation direction of the optical path or in the opposite direction of the propagation direction, so as to perform detonation modification on the silicon carbide material at other positions of the optical path to form a cutting path; and the longitudinal temperature gradient can induce cracks at each detonation point to grow in the optical path along a direction parallel to the optical path. Step 4: Following the method in Step 1, move the first laser beam to form another new heating optical path at other locations within the silicon carbide ingot at a predetermined depth layer; Step 5: Following the methods in Step 2 and Step 3, focus the second laser beam on the new optical path and perform bursting and scanning on the new optical path to form a cutting path at the new optical path position; Step Six: Following the methods in Steps Four and Five, multiple cleavage channels are formed at a predetermined depth in the silicon carbide ingot; and cracks on adjacent cleavage channels can grow and connect together in a direction perpendicular to the optical path to form a modified layer at the predetermined depth. Wherein, the first laser beam is a Bessel beam; the light intensity on the cross-section of the optical path fluctuates in a wave-like manner from the center position of the first laser beam to the edge position of the first laser beam, so as to form a transverse temperature gradient with fluctuating temperature on the cross-section of the optical path; and the transverse temperature gradient can induce the crack generated at each burst point to grow laterally in the optical path along a direction perpendicular to the optical path.

2. The generation method as described in claim 1, characterized in that, The chemical solution is a strong alkaline solution.

3. The generation method as described in claim 2, characterized in that, The strong alkaline solution is a potassium hydroxide solution, a sodium hydroxide solution, or a mixture of potassium hydroxide and sodium hydroxide.

4. The generation method as described in claim 3, characterized in that, The strong alkaline solution is a potassium hydroxide solution, or a mixture of potassium hydroxide and sodium hydroxide, wherein the mass fraction of the potassium hydroxide solution is 20% to 40%.

5. The generation method as described in claim 3, characterized in that, The strong alkaline solution is a sodium hydroxide solution or a mixture of potassium hydroxide and sodium hydroxide, wherein the mass fraction of the sodium hydroxide solution is 20% to 40%.

6. The generation method as described in claim 1, characterized in that, The chemical solution is a strong acid solution.

7. The generation method as described in claim 6, characterized in that, The strong acid solution is a hydrofluoric acid solution, a nitric acid solution, or a mixture of hydrofluoric acid and nitric acid.

8. The generation method as described in claim 7, characterized in that, The strong acid solution is a hydrofluoric acid solution or a mixture of hydrofluoric acid and nitric acid, wherein the mass fraction of the hydrofluoric acid solution is 35% to 40%.

9. The generation method as described in claim 7, characterized in that, The strong acid solution is a hydrofluoric acid solution or a mixture of hydrofluoric acid and nitric acid, wherein the nitric acid solution has a mass fraction of 60% to 70%.

10. The generation method as described in claim 1, characterized in that, The process of forming a modified layer at a predetermined depth on the silicon carbide ingot using laser stealth processing includes: A laser beam is provided, wherein the laser energy density of the laser beam is greater than the silicon carbide ablation threshold; The laser beam is focused onto a predetermined depth layer inside the silicon carbide ingot and scanned at the predetermined depth layer, causing the single-crystal silicon carbide at the predetermined depth layer to decompose into silicon and carbon, thereby forming a modified layer at the predetermined depth layer.

Images