A low-loss laser slicing method for silicon carbide ingots

Abstract

This invention discloses a low-loss laser slicing method for silicon carbide ingots, relating to the fields of laser manufacturing and semiconductor technology. The method includes a first scan: setting the pulsed laser energy to a first preset energy level, forming a first type of pit at the focal point inside the SiC ingot, and inducing cracks around the first type of pit, thus forming a modified layer inside the SiC ingot; a second scan: setting the pulsed laser energy to a second preset energy level, forming a second type of pit at the focal point inside the SiC ingot. If cracks formed in the first scan exist near the focal point, they can be further propagated; if no cracks formed in the first scan exist near the focal point, no new cracks are generated; thus forming a uniform modified layer. This invention reduces material loss and improves slicing efficiency through a second pulsed laser scan, avoiding the problems of ineffective modified layer formation in some areas and excessively deep modified layers in others due to the optical inhomogeneities of the silicon carbide ingot during a single laser scan.

Description

Technical Field

[0001] This invention belongs to the fields of laser manufacturing and semiconductor technology, and in particular to a low-loss laser slicing method for silicon carbide ingots. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Silicon carbide (SiC), a typical third-generation semiconductor material, possesses excellent physical properties such as a wide bandgap, high thermal conductivity, strong breakdown electric field, and high electron saturation velocity. It is an ideal material for fabricating power electronic devices, high-frequency microwave devices, and optoelectronic devices, and can be widely used in industries such as 5G, high-speed rail, automobiles, energy, and consumer electronics. SiC substrates are typically 400 to 600 micrometers thick and are obtained by slicing SiC ingots. SiC has a Mohs hardness of 9.2-9.4, far exceeding that of single-crystal silicon, making it more difficult to process, requiring longer processing times, and resulting in a significantly higher cost—approximately 20 times that of single-crystal silicon.

[0004] Currently, the main method for cutting SiC single crystal ingots in China is diamond wire cutting, which also includes free abrasive cutting and electrical discharge machining (EDM). Diamond wire cutting involves bonding diamond abrasive to a metal wire, which then moves with the wire to cut the ingot. Diamond wire cutting is extremely inefficient; for example, cutting a 6-inch SiC ingot takes 110-120 hours, with a total thickness change (TTV) of approximately 100 μm and a material loss rate of 40%-50%. Furthermore, cutting process parameters, bonded abrasive size, workpiece feed motion, and wire speed all affect the cutting accuracy, leading to severe surface damage to the wafer, increased processing difficulty, and reduced yield, seriously hindering the development of the SiC industry. Therefore, exploring high-efficiency, high-quality processing technologies to solve the SiC ingot processing challenges, reduce material loss during SiC substrate slicing, and shorten processing time are crucial for reducing the cost of SiC devices and promoting the development and application of the SiC industry.

[0005] Laser processing technology uses a focused laser beam as a "processing tool" to irradiate the surface or interior of a material. Part of the light energy is absorbed by the material, causing localized heating, melting, and vaporization of the target material. Ultimately, the material detaches from the "ablation zone" in gaseous or plasma form, completing the processing. Laser processing is a non-contact technology, with no "tool" wear and no "cutting force" acting on the workpiece. It boasts advantages such as high processing efficiency, ease of automation, good adaptability, and environmental friendliness, and holds promise for breakthroughs in the quality, precision, and efficiency of SiC ingot slicing. In 2010, the German company Siltectra developed a complete SiC ingot "cold cutting" process, winning a top 100 European and world technology research award in 2015. In 2018, it was acquired by the global semiconductor giant Infineon, completing the upgrade of its ingot cutting equipment. In 2015, Disco Corporation of Japan entered the field of ultrafast laser cutting of SiC single crystal ingots. In 2018, it developed the "KABRA" (Key Amorphous-Black Repetitive Absorption) technology and launched ultrafast laser cutting equipment for SiC ingots, increasing slicing efficiency by 92% and controlling losses to around 100 micrometers. This technology has been applied in the industry. In China, Han's Semiconductor Equipment Technology Co., Ltd. launched a SiC ingot laser cutting equipment in May 2022, filling a gap in the domestic market.

[0006] The inventors discovered that existing laser slicing technologies all employ a single-scan approach, meaning that the same laser pulse parameters and a fixed laser irradiation point spacing are used to complete one scan of the SiC ingot. A modified layer is formed at the laser incident focal point before the surface wafer is separated from the ingot. While increasing processing efficiency with this technology can be achieved by increasing laser pulse energy and irradiation point spacing, increasing laser pulse energy can lead to deeper cracks in the crystal along the laser incident direction, resulting in subsurface damage in the processed SiC wafer. This requires further polishing to remove the damaged layer, undoubtedly increasing material loss and reducing efficiency. Conversely, decreasing laser pulse energy and shortening the irradiation point spacing can reduce material loss during processing, but this reduces processing efficiency and increases the likelihood of incomplete modified layer formation preventing effective wafer separation from the ingot. Therefore, it is necessary to optimize parameters such as laser pulse energy, irradiation point spacing, and processing speed to achieve a balance between processing efficiency and material loss.

[0007] The inventors also discovered that achieving perfectly uniform optical homogeneity (such as uneven defect density) in SiC ingots during growth is difficult, especially as ingot size increases, this inhomogeneity becomes more pronounced. While these inhomogeneities typically do not affect the performance of the final SiC device, they significantly impact crack initiation and propagation during laser slicing, making it difficult for the processing system to consistently maintain an optimal balance between processing efficiency and material loss. In practice, methods such as appropriately increasing laser pulse energy and shortening the irradiation point spacing are commonly used to ensure effective wafer separation, which inevitably leads to increased material loss. Summary of the Invention

[0008] The purpose of this invention is to provide a low-loss laser slicing method for silicon carbide ingots. By using pulsed laser for secondary scanning, the material loss during laser slicing is reduced and the slicing efficiency is improved. This method avoids problems such as the inability to effectively form a modified layer in some areas and the excessive depth of the modified layer in some areas due to optical inhomogeneities of silicon carbide ingots (such as uneven defect density) during a single laser scan.

[0009] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0010] This invention relates to a low-loss laser slicing method for silicon carbide ingots, comprising the following steps:

[0011] First scan: The pulsed laser beam is focused at a set depth inside the SiC ingot to be sliced, and the energy of the pulsed laser is set to the first set energy, so that the first type of pit is formed at the focal point inside the SiC ingot, and cracks are generated around the first type of pit. The moving speed of the SiC ingot relative to the laser beam is controlled so that the laser forms a modified layer inside the SiC ingot.

[0012] Second scan: The pulsed laser beam is focused at the same depth inside the SiC ingot to be sliced ​​as in the first scan. The energy of the pulsed laser is set to a second preset energy, causing a second type of pit to form at the focal point inside the SiC ingot. At the same time, if there are cracks formed in the first scan near the focal point, the cracks can be further extended. If there are no cracks formed in the first scan near the focal point, no new cracks will be generated. The moving speed of the SiC ingot relative to the laser beam is controlled to form a uniform modified layer.

[0013] The area of ​​the second type of pit is smaller than that of the first type of pit.

[0014] Preferably, in the first scan, the first set energy of the pulsed laser is set to 5-100 μJ; in the second scan, the second set energy of the pulsed laser is set to 1-20 μJ, and the second set energy is less than the first set energy.

[0015] Preferably, in both the first and second scans, the SiC ingot is controlled to move relative to the laser beam in the X and Y directions of the plane defined by the SiC ingot.

[0016] Preferably, in the first scan, the SiC ingot is controlled to move at a speed of 10-1000 mm / s along the X-axis and the distance between adjacent pulsed laser irradiation points is 10-100 μm; the distance between adjacent irradiation points along the Y-axis is 50-500 μm.

[0017] Preferably, in the second scan, the SiC ingot is controlled to move at a speed of 5-500 mm / s along the X-axis, which is less than the speed of movement along the X-axis in the first scan; the distance between adjacent pulsed laser irradiation points is 5-50 μm, which is less than the distance between irradiation points in the first scan; and the distance between adjacent irradiation points along the Y-axis is 25-100 μm, which is less than the distance between adjacent irradiation points along the Y-axis in the first scan.

[0018] Preferably, in the first and second scans, the pulse width of the pulsed laser is between 100 fs and 1 ns.

[0019] Preferably, in the first and second scans, the pulse repetition frequency of the pulsed laser is between 1k and 100kHz.

[0020] Preferably, after the first and second scans are completed, a uniform and fragile modified layer has been formed inside the SiC ingot. Applying external force causes the modified layer to completely break, thus completely separating the SiC wafer on the surface from the SiC ingot below.

[0021] Preferred options also include:

[0022] A silicon carbide ingot laser slicing system was constructed, comprising a SiC ingot to be sliced, a laser output unit, a displacement platform unit, and an electromechanical control unit. The laser output unit includes a pulsed laser, a regulating optical path, and a focusing device, specifically comprising:

[0023] Set the positions of the pulsed laser, adjusting optical path, and concentrator in the laser output unit as required. Use the pulsed laser to output pulsed laser, use the adjusting optical path to shape the beam and adjust the pulsed laser energy, and use the concentrator to precisely focus the pulsed laser at a specific depth inside the SiC ingot.

[0024] The displacement platform unit is set at a predetermined distance below the condenser, and the displacement platform unit has at least three-axis displacement adjustment functions: X, Y, and Z.

[0025] The electromechanical control unit is connected to the adjustment optical path to achieve laser shaping control and energy control; the electromechanical control unit is connected to the condenser to achieve focus control; the electromechanical control unit is connected to the displacement platform to achieve position and speed control of the displacement platform.

[0026] The SiC ingot to be sliced ​​is fixed on a displacement platform.

[0027] Preferably, the method of applying external force to completely fracture the modified layer is to apply tensile force or ultrasonic vibration.

[0028] The present invention has the following beneficial effects:

[0029] This invention proposes a low-loss laser slicing method for silicon carbide ingots. It is a method that reduces material loss during laser slicing and improves slicing efficiency by using a pulsed laser for secondary scanning. This invention can avoid problems such as the inability to effectively form a modified layer in some areas and the excessive depth of the modified layer in some areas due to optical inhomogeneities of silicon carbide ingots (such as uneven defect density) during a single laser scanning process.

[0030] In the first scanning process of this invention, a high-energy pulsed laser is used to control the displacement platform unit to move at a relatively fast speed, forming a modified layer inside the silicon carbide ingot. In the second scanning process, a low-energy pulsed laser is used to control the displacement platform unit to move at a slower speed, promoting further propagation of cracks in the modified layer inside the silicon carbide. This approach ensures that the silicon carbide slices can be effectively separated from the ingot while keeping material loss at a low level and improving processing efficiency.

[0031] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the crack propagation in a SiC ingot after the first scan.

[0034] Figure 2 This is a schematic diagram of the crack propagation in the SiC ingot after the second scan.

[0035] Figure 3 This is a schematic diagram of the system architecture for implementing laser slicing according to the present invention;

[0036] Figure 4 This is a schematic diagram of the first scanning process;

[0037] Figure 5 This is a schematic diagram of the second scanning process;

[0038] Figure 6a This is a photograph of the upper surface of the SiC sample after laser slicing and peeling;

[0039] Figure 6b This is a photograph of the lower surface of the SiC sample after laser slicing and peeling.

[0040] The attached diagram lists the components represented by each number as follows:

[0041] The components include a SiC ingot to be sliced ​​100, a laser output unit 200, a displacement platform unit 300, an electromechanical control unit 400, a pulsed laser 201, an adjustment optical path 202, a concentrator 203, and a pulsed laser 204. Detailed Implementation

[0042] 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.

[0043] Please see Figure 1-5 As shown, this invention provides a low-loss laser slicing method for silicon carbide ingots, comprising the following steps:

[0044] First scan: The pulsed laser beam is focused at a set depth inside the SiC ingot to be sliced, and the energy of the pulsed laser is set to the first set energy, so that the first type of pit is formed at the focal point inside the SiC ingot, and cracks are generated around the first type of pit. The moving speed of the SiC ingot relative to the laser beam is controlled so that the laser forms a modified layer inside the SiC ingot.

[0045] Second scan: The pulsed laser beam is focused at the same depth inside the SiC ingot to be sliced ​​as in the first scan. The energy of the pulsed laser is set to a second preset energy, causing a second type of pit to form at the focal point inside the SiC ingot. At the same time, if there are cracks formed in the first scan near the focal point, the cracks can be further extended. If there are no cracks formed in the first scan near the focal point, no new cracks will be generated. The moving speed of the SiC ingot relative to the laser beam is controlled to form a uniform modified layer.

[0046] The area of ​​the second type of pit is smaller than that of the first type of pit.

[0047] Furthermore, in the first scan, the first set energy of the pulsed laser is set to 5-100 μJ; in the second scan, the second set energy of the pulsed laser is set to 1-20 μJ, and the second set energy is less than the first set energy.

[0048] Furthermore, in both the first and second scans, the SiC ingot is controlled to move relative to the laser beam in the X and Y directions of the plane defined by the SiC ingot.

[0049] Furthermore, in the first scan, the SiC ingot was controlled to move at a speed of 10-1000 mm / s along the X-axis and the distance between adjacent pulsed laser irradiation points was 10-100 μm; the distance between adjacent irradiation points along the Y-axis was 50-500 μm.

[0050] Furthermore, in the second scan, the SiC ingot is controlled to move at a speed of 5-500 mm / s along the X-axis, which is less than the speed of movement along the X-axis in the first scan; the distance between adjacent pulsed laser irradiation points is controlled at 5-50 μm, which is less than the distance between irradiation points in the first scan; and the distance between adjacent irradiation points along the Y-axis is controlled at 25-100 μm, which is less than the distance between adjacent irradiation points along the Y-axis in the first scan.

[0051] Furthermore, in the first and second scans, the pulse width of the pulsed laser is between 100 fs and 1 ns.

[0052] Furthermore, in the first and second scans, the pulse repetition frequency of the pulsed laser is between 1k and 100kHz.

[0053] Furthermore, after completing the first and second scans, a uniform and fragile modified layer has been formed inside the SiC ingot. Applying external force causes the modified layer to completely break, thus completely separating the SiC wafer on the surface from the SiC ingot below.

[0054] Furthermore, it also includes:

[0055] A silicon carbide ingot laser slicing system was constructed, comprising a SiC ingot to be sliced, a laser output unit, a displacement platform unit, and an electromechanical control unit. The laser output unit includes a pulsed laser, a regulating optical path, and a focusing device, specifically comprising:

[0056] Set the positions of the pulsed laser, adjusting optical path, and concentrator in the laser output unit as required. Use the pulsed laser to output pulsed laser, use the adjusting optical path to shape the beam and adjust the pulsed laser energy, and use the concentrator to precisely focus the pulsed laser at a specific depth inside the SiC ingot.

[0057] The displacement platform unit is set at a predetermined distance below the condenser, and the displacement platform unit has at least three-axis displacement adjustment functions: X, Y, and Z.

[0058] The electromechanical control unit is connected to the adjustment optical path to achieve laser shaping control and energy control; the electromechanical control unit is connected to the condenser to achieve focus control; the electromechanical control unit is connected to the displacement platform to achieve position and speed control of the displacement platform.

[0059] The SiC ingot to be sliced ​​is fixed on a displacement platform.

[0060] Furthermore, the way to apply external force to completely fracture the modified layer is by applying tension or ultrasonic vibration.

[0061] Example 1:

[0062] A low-loss laser slicing method for silicon carbide ingots employs a two-stage scanning approach. In the first scan, a pulsed laser beam is focused at a predetermined depth within the SiC ingot to be sliced. The pulsed laser is output at a relatively high energy level, and a displacement platform unit is controlled to move at a relatively high speed, allowing the laser to form a modified layer within the SiC ingot. In the second scan, the pulsed laser beam is focused at the same depth within the SiC ingot to be sliced. The pulsed laser is output at a relatively low energy level, and the displacement platform unit is controlled to move at a slower speed, allowing the cracks in the modified layer to further expand, forming a uniform modified layer.

[0063] During the first scan, the pulsed laser energy should be sufficient to form a pit at the focal point inside SiC and generate cracks around the pit. The laser pulse width to achieve this effect is 100 fs to 1 ns and the pulse energy is 5 to 100 μJ.

[0064] During the first scan, the control displacement platform unit moves at a relatively fast speed, with a pulse repetition frequency of 1k-100kHz. The moving speed of the displacement platform in the X-axis direction is 10-1000mm / s, and the spacing between adjacent pulse laser irradiation points is 10-100μm. The spacing between adjacent irradiation points in the Y-axis direction is determined by the step distance of the displacement platform along the Y-axis direction, with a step distance of 50-500μm.

[0065] During the first scan: the pulsed laser is set to output at a relatively high energy, which should ensure that the pulsed laser energy is sufficient to form a pit at the focal point inside SiC and generate cracks around the pit; the displacement platform unit is controlled to move at a relatively fast speed in the X and Y axes, so that the laser forms a modified layer at a certain set depth (Z-axis direction) inside the SiC ingot.

[0066] After the first scan, the crack morphology of the modified layer inside SiC is as follows: Figure 1 As shown, due to the difficulty in achieving completely uniform optical homogeneity during SiC growth (such as uneven defect density), the morphology and size of cracks are also uneven.

[0067] During the second scan, the pulsed laser energy is controlled to form a small pit at the focal point inside SiC. If there is a crack formed in the first scan near the focal point, the crack can be further extended; if there is no crack formed in the first scan near the focal point, no new crack will be generated. The pulse width to achieve this effect is 100 fs to 1 ns, and the pulse energy is 1 to 20 μJ, which is less than the pulse energy of the first scan.

[0068] During the second scan, the control displacement platform unit moves at a slower speed, with a pulse repetition frequency of 1k-100kHz. The X-axis displacement platform moving speed is 5-500mm / s, which is less than the moving speed during the first scan. The spacing between adjacent pulse laser irradiation points is 5-50μm, which is less than the spacing between irradiation points during the first scan. The spacing between adjacent irradiation points in the Y-axis direction is determined by the step distance of the displacement platform along the Y-axis direction, which is 25-100μm, which is less than the step distance during the first scan.

[0069] During the second scan: the pulsed laser is set to output at a lower energy level. The energy of the pulsed laser should be controlled so that a small pit can be formed at the focal point inside the SiC. If there is a crack formed in the first scan near the focal point, the crack can be further extended; if there is no crack formed in the first scan near the focal point, no new crack will be generated. The displacement platform is controlled to move slowly in the X and Y planes so that the laser forms a uniform modified layer at the same depth (same Z-axis position) inside the SiC ingot.

[0070] After the second scan, the crack morphology of the modified layer inside SiC is as follows: Figure 2 As shown, the non-uniform cracks generated after the first scan were expanded, forming uniform and intersecting cracks.

[0071] After two scans, a uniform and fragile modified layer has formed inside the silicon ingot. The modified layer can be completely broken by applying tension or ultrasonic vibration, thus completely separating the SiC wafer on the surface from the ingot below.

[0072] like Figure 3 As shown, the equipment required to complete this cutting process includes: a SiC ingot 100 to be sliced, a laser output unit 200, a displacement platform unit 300, and an electromechanical control unit 400.

[0073] The laser output unit 200 includes a pulsed laser 201 for outputting pulsed laser light; an adjustment optical path 202 for beam shaping and adjusting the pulsed laser energy; and a concentrator 203 for precisely focusing the pulsed laser light 204 output by the laser onto a specific depth inside the SiC ingot 100.

[0074] The displacement platform unit 300 should include a combined displacement platform with at least X, Y, and Z axis adjustment functions.

[0075] The electromechanical control unit 400 is connected to the adjustment optical path 202 to realize laser shaping control and energy control; it is connected to the condenser 203 to realize focus control; and it is connected to the displacement platform 300 to realize the position, movement speed and other control of the displacement platform.

[0076] During the first scan, such as Figure 4 As shown:

[0077] The first step is to firmly fix the SiC ingot 100 to be processed onto the displacement platform 300. In this example, adsorption is used, but any method that achieves the same effect can be used.

[0078] The second step involves controlling the optical path 202 via the electromechanical control unit 400 to output the pulsed laser 204 at a relatively high energy level. This energy should be sufficient to create a pit at the focal point inside the SiC ingot 100 and generate cracks around the pit. In this example, the pulse energy is set to 10 microjoules; any pulse energy will achieve the same effect.

[0079] The third step involves controlling the concentrator 203 via the electromechanical control unit 400 to precisely focus the pulsed laser at a predetermined depth within the SiC ingot 100. In this example, the depth is set to 400 micrometers, but any depth below the ingot surface is acceptable.

[0080] The fourth step involves controlling the displacement platform unit 300 via the electromechanical control unit 400 to move rapidly within the X and Y planes, completing the scan and forming a modified layer inside the SiC ingot. In this example, the final effect achieved is a spacing of 50 micrometers between adjacent irradiation points on the X-axis and 200 micrometers between adjacent irradiation points on the Y-axis; any irradiation point spacing that achieves a similar effect is acceptable.

[0081] During the second scan, such as Figure 5 As shown:

[0082] The first step is to control the optical path 202 via the electromechanical control unit 400 to set the pulsed laser 204 to output at a relatively low energy. The pulsed laser energy should be controlled to form a small pit at the focal point inside the SiC. In this example, the pulse energy is set to 3 microjoules; any pulse energy that achieves the same effect is acceptable.

[0083] The second step involves controlling the concentrator 203 via the electromechanical control unit 400 to precisely focus the pulsed laser within the SiC ingot to the same depth as in the first scan. In this example, the depth setting is maintained at 400 micrometers; maintaining a similar depth as in the first scan is also acceptable.

[0084] The third step involves controlling the displacement platform unit 300 via the electromechanical control unit 400 to move at a relatively slow speed within the X and Y planes to complete the scanning process and form a uniform modified layer inside the SiC ingot. In this example, the final effect achieved is a spacing of 25 micrometers between adjacent irradiation points on the X-axis and 50 micrometers between adjacent irradiation points on the Y-axis; any irradiation point spacing that can achieve a similar effect is acceptable.

[0085] After two scans, a uniform and fragile modified layer has formed inside the silicon ingot. This modified layer can be completely broken by applying tensile force or ultrasonic vibration, thus completely separating the SiC wafer on the surface from the ingot below. The SiC sample after laser slicing is shown in Figure 6. Figure 6a This is a photograph of the upper surface of the SiC sample after laser slicing and peeling. Figure 6b This is a photograph of the lower surface of the SiC sample after laser slicing and peeling.

[0086] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0087] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-loss laser slicing method for silicon carbide ingots, characterized in that, Includes the following steps: First scan: The pulsed laser beam is focused at a set depth inside the SiC ingot to be sliced, and the energy of the pulsed laser is set to the first set energy, so that the first type of pit is formed at the focal point inside the SiC ingot, and cracks are generated around the first type of pit. The moving speed of the SiC ingot relative to the laser beam is controlled so that the laser forms a modified layer inside the SiC ingot. Second scan: The pulsed laser beam is focused at the same depth inside the SiC ingot to be sliced ​​as in the first scan. The energy of the pulsed laser is set to a second preset energy, causing a second type of pit to form at the focal point inside the SiC ingot. At the same time, if there are cracks formed in the first scan near the focal point, the cracks can be further extended. If there are no cracks formed in the first scan near the focal point, no new cracks will be generated. The moving speed of the SiC ingot relative to the laser beam is controlled to form a uniform modified layer. The area of ​​the second type of pit is smaller than that of the first type of pit.

2. The low-loss laser slicing method for silicon carbide ingots according to claim 1, characterized in that, In the first scan, the first set energy of the pulsed laser is set to 5-100 μJ; in the second scan, the second set energy of the pulsed laser is set to 1-20 μJ, and the second set energy is less than the first set energy.

3. The low-loss laser slicing method for silicon carbide ingots according to claim 1, characterized in that, In both the first and second scans, the SiC ingot was controlled to move relative to the laser beam in the X and Y directions of the plane defined by the SiC ingot.

4. The low-loss laser slicing method for silicon carbide ingots according to claim 3, characterized in that, In the first scan, the SiC ingot was controlled to move at a speed of 10-1000 mm / s along the X-axis and the distance between adjacent pulsed laser irradiation points was 10-100 μm; the distance between adjacent irradiation points along the Y-axis was 50-500 μm.

5. The low-loss laser slicing method for silicon carbide ingots according to claim 3, characterized in that, In the second scan, the SiC ingot is controlled to move at a speed of 5-500 mm / s along the X-axis, which is less than the speed of movement along the X-axis in the first scan, and the distance between adjacent pulsed laser irradiation points is controlled to be 5-50 μm, which is less than the distance between irradiation points in the first scan. The distance between adjacent irradiation points in the Y-axis direction is 25-100 μm, which is smaller than the distance between adjacent irradiation points in the Y-axis direction during the first scan.

6. The low-loss laser slicing method for silicon carbide ingots according to claim 1, characterized in that, In the first and second scans, the pulse width of the pulsed laser was between 100 fs and 1 ns.

7. The low-loss laser slicing method for silicon carbide ingots according to claim 1, characterized in that, In the first and second scans, the pulse repetition frequency of the pulsed laser was between 1k and 100kHz.

8. The low-loss laser slicing method for silicon carbide ingots according to claim 1, characterized in that, After the first and second scans are completed, a uniform and fragile modified layer has been formed inside the SiC ingot. Applying external force causes the modified layer to break completely, thus completely separating the SiC wafer on the surface from the SiC ingot below.

9. The low-loss laser slicing method for silicon carbide ingots according to claim 1, characterized in that, Also includes: A silicon carbide ingot laser slicing system was constructed, comprising a SiC ingot to be sliced, a laser output unit, a displacement platform unit, and an electromechanical control unit. The laser output unit includes a pulsed laser, a regulating optical path, and a focusing device, specifically comprising: Set the positions of the pulsed laser, adjusting optical path, and concentrator in the laser output unit as required. Use the pulsed laser to output pulsed laser, use the adjusting optical path to shape the beam and adjust the pulsed laser energy, and use the concentrator to precisely focus the pulsed laser at a specific depth inside the SiC ingot. The displacement platform unit is set at a predetermined distance below the condenser, and the displacement platform unit has at least three-axis displacement adjustment functions: X, Y, and Z. The electromechanical control unit is connected to the adjustment optical path to achieve laser shaping control and energy control; the electromechanical control unit is connected to the condenser to achieve focus control; the electromechanical control unit is connected to the displacement platform to achieve position and speed control of the displacement platform. The SiC ingot to be sliced ​​is fixed on a displacement platform.

10. The low-loss laser slicing method for silicon carbide ingots according to claim 8, characterized in that, The way to completely fracture the modified layer by applying external force is to apply tension or ultrasonic vibration.

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