A method and apparatus for laser delaminating a silicon carbide ingot

Abstract

The application discloses a method and device for laser stripping silicon carbide ingots. First, the laser focal point is aimed at a preset plane inside the ingot, and the laser is processed on the preset plane in a set direction and scanning line interval to form a plurality of explosion points on the plane to prepare a modified layer. Then, the modified layer is irradiated and heated by a xenon lamp. After the heating is completed, a pulling force opposite in direction and perpendicular to the end surface is applied to the two ends of the ingot to strip the wafer from the silicon carbide ingot. The application greatly reduces the pulling stress required for stripping, improves the stability of stripping, and at the same time, makes the wafer form a relatively flat stripping surface, reduces the roughness of the stripping surface, reduces the material loss of subsequent grinding, improves the silicon carbide stripping efficiency, and reduces the production cost.

Description

Technical Field

[0001] This invention belongs to the field of crystal processing technology, and in particular relates to a method and apparatus for laser stripping of silicon carbide ingots. Background Technology

[0002] Silicon carbide (SiC) microcrystals are third-generation wide-bandgap semiconductor materials, possessing excellent properties such as high thermal conductivity, high breakdown voltage, extremely high carrier mobility, and high chemical stability. They are ideal materials for fabricating high-frequency, high-power electronic and optoelectronic devices that operate under high-temperature and high-radiation conditions. However, due to SiC's extremely high hardness, advanced cutting techniques are required to obtain qualified semiconductor wafers. To obtain thinner wafers, the traditional processing method involves using a wire saw to cut cylinders into slices, followed by grinding to reduce the thickness to a specific level. However, this method wastes a significant amount of material; a considerable portion of the wafer (70-80%) is ground away during the grinding process, resulting in material loss. Furthermore, for a material like silicon carbide with a Mohs hardness of 9.5, the wire saw method is not only inefficient but also causes environmental pollution and tool wear, hindering the development of the silicon carbide industry.

[0003] With the development of the semiconductor industry and the increasing awareness of energy conservation and environmental protection, laser lift-off technology has begun to be applied to silicon carbide wafer lift-off. Ultrafast lasers have advantages such as short pulse duration, high peak energy, and low thermal effect, enabling non-contact processing of materials. Laser lift-off technology includes two processes: laser modification of the material's interior and lift-off. First, a modified layer is formed by laser irradiation inside the material. This modified layer includes the laser-irradiated area and cracks. Then, force is applied to the modified layer, causing the cracks to propagate and the wafer to be lifted off the ingot along the cracks.

[0004] Due to the high hardness of silicon carbide, the tensile stress required for peeling is large, often necessitating alternative methods. For example, existing cold split peeling technology requires a laser to be focused internally to form a modified layer, followed by bonding the SiC ingot containing the modified layer to a sacrificial layer of a high-expansion-coefficient material (such as PDMS). The sacrificial layer is then cooled, and peeling is achieved through cooling stress. After peeling, a chemical solution is needed to separate the sacrificial layer from the SiC wafer. This method is inefficient and causes chemical pollution. Another wafer manufacturing method utilizes a combination of laser treatment and temperature-induced stress. Laser irradiation creates a defect layer inside the solid, causing the temperature of the target separation layer to differ from the original solid temperature, achieving self-separation of the target separation layer. However, simple heating methods cannot guarantee the uniformity and stability of the modified layer stress. Liquid nitrogen is also used for cooling separation, but the additional consumables increase production costs, and introducing cooling equipment further complicates the production process.

[0005] Given the shortcomings of existing separation technologies, there is an urgent need to design a separation method that has low peeling stress, stable peeling, and low material loss. Summary of the Invention

[0006] This invention provides a method and apparatus for laser stripping of silicon carbide ingots. By controlling the spacing and mode of laser scanning, a modified layer containing burst points is prepared. Compared with the modified layer formed by conventional laser processing, this invention enables the laser-modified region to form a loosely bonded, easily breakable brittle integral layered structure, which greatly reduces the tensile stress required for stripping and improves the stability of stripping. At the same time, it makes the wafer form a relatively flat stripping surface, reduces the roughness of the stripping surface, reduces the material loss of subsequent grinding, improves the silicon carbide stripping efficiency, and also reduces the production cost.

[0007] The technical solution of the present invention is as follows:

[0008] A method for laser ablation of silicon carbide ingots includes the following steps:

[0009] S1. Focus the laser beam on a preset plane at a preset depth inside the silicon carbide ingot;

[0010] S2. The laser beam is directed to scan the preset plane in a line scanning manner, according to the pre-set first scanning direction and a scanning line spacing of 10-50um, so that the scanning path covers the entire preset plane, and the first scan is completed.

[0011] S3. Change only the scanning direction of the laser beam, and make the laser beam scan the preset plane again in a second scanning direction that is perpendicular to the first scanning direction, so that the scanning path covers the entire preset plane again, and the second scan is completed.

[0012] S4. After laser processing is completed, multiple planar burst points are formed at the intersections of the first and second scanning paths, thereby preparing a loosely structured modified layer.

[0013] S5. Use a xenon lamp as a heat source to irradiate and heat the modified layer for 1-2 hours;

[0014] S6. After heating is complete, apply opposite pulling forces perpendicular to the end face of the silicon carbide ingot at the top and bottom ends to peel the wafer off the silicon carbide ingot.

[0015] This invention first uses a laser with a scanning line spacing of 10-50µm for secondary processing to form a loosely bonded, easily separable, brittle, layered structure within the ingot. This helps reduce the tensile stress during wafer peeling and improves the peeling effect of silicon carbide wafers. After the modified layer is formed, a high-power xenon lamp is used to irradiate and heat the modified layer for 1-2 hours. The large xenon lamp spot effectively covers the entire processing area, achieving uniform heating of the modified area and ensuring uniform stress distribution within the modified layer, allowing initial cracks to further propagate. Finally, applying opposing tensile forces at both ends of the ingot achieves wafer peeling. The method of this invention is simple and feasible, producing a smooth peeled wafer surface with reliable quality.

[0016] In this invention, the smaller the line spacing of the laser scan, the denser the multiple burst points formed at the overlap of two laser scans. Cracks extend and overlap around these burst points, forming a relatively fragile modified zone, which is beneficial for subsequent peeling work. This reduces the peeling tensile stress required to peel the wafer and lowers the roughness of the unpolished surface of the wafer after peeling. To improve the peeling effect, this invention designs a line spacing range of 10-50 μm. The reason is that the typical laser pulse width is around 10 μm. If the line spacing is less than 10 μm, due to the inherent pulse width of the laser beam, the two lines will generally overlap when the line spacing is less than a certain width, wasting scanning energy and potentially causing ablation, affecting the peeling effect. Conversely, if the line spacing exceeds 50 μm, the burst points formed by the modified layer will be relatively loose, resulting in excessive peeling tensile stress, which also affects the peeling effect. It should be noted that this is only a preferred method; the operator can set the scanning line spacing according to the actual ideal peeling tensile stress.

[0017] The present invention sets the time for irradiating and heating the modified layer with a xenon lamp to 1-2 hours. This is based on ensuring uniform heating of the modified layer within a certain time range while avoiding excessive heat generation due to prolonged heating, thus reducing energy consumption. This time range can be set according to actual conditions; this is merely a preferred example.

[0018] Furthermore, the preset depth refers to the distance between the preset plane and the top surface of the silicon carbide ingot. The preset depth typically ranges from 300 to 1000 μm. Since the target thickness of the wafer is typically 50 μm to 150 μm, the specific preset depth can be set according to actual production needs and is not limited here. However, the preset depth of the material must be greater than the target thickness of the wafer to be peeled off.

[0019] Furthermore, the preset depth exceeds the thickness of the wafer obtained by stripping by at least 100 μm.

[0020] The preset depth is guaranteed to exceed the required wafer thickness by at least 100µm. The purpose of this design is to ensure that the top of the ingot has a certain thickness to withstand the force from above during the peeling process, thereby ensuring the stability of the wafer during peeling.

[0021] Furthermore, the scanning angle range of the first scanning direction relative to the preset plane is 0-360 degrees.

[0022] The laser beam can start scanning in any direction on a preset plane, as long as the first scanning direction and the second scanning direction remain perpendicular to each other.

[0023] Furthermore, the laser beam spot is one of the following: Gaussian spot, square flat-top spot, circular flat-top spot, elliptical flat-top spot, or rhomboid flat-top spot.

[0024] Furthermore, the wavelength of the laser beam is 150nm-1030nm, the pulse width is 1-15ps, and the repetition frequency is 1-10KHz.

[0025] Furthermore, the xenon lamp is a cylindrical short-arc xenon lamp with an internal filter, the wavelength range of the output light is 400-600nm, the spot size is 70-150mm, and the power is greater than 10kW.

[0026] The present invention also provides an apparatus for laser stripping silicon carbide ingots, for performing the above-mentioned laser stripping method for silicon carbide ingots, the apparatus comprising an ultrafast laser, an attenuator, an aperture, a beam expander, an objective lens, a CCD camera, a moving work platform, and a xenon lamp.

[0027] The silicon carbide ingot is fixedly placed on the mobile working platform. The ultrafast laser outputs a Gaussian laser beam, which enters the objective lens after being transmitted through an attenuator, an aperture, and a beam expander. The objective lens focuses the laser beam onto a preset plane at a preset depth inside the silicon carbide ingot. At the same time, the CCD camera is used to adjust and correct the position of the focus.

[0028] After focusing is complete, the moving work platform moves the silicon carbide ingot in the X / Y / Z three-dimensional directions so that the laser beam can complete the scanning and processing on the preset plane of the silicon carbide ingot.

[0029] After the scanning process is completed, the external xenon lamp is moved directly above the silicon carbide ingot so that the xenon lamp can irradiate and heat the modified layer formed by the scanning process.

[0030] After heating, a substrate is attached to the top surface of the silicon carbide ingot, and the substrate is pulled to peel the wafer off the silicon carbide ingot.

[0031] Furthermore, the substrate is bonded to the top surface of the silicon carbide ingot using epoxy resin.

[0032] Furthermore, a mechanical gripper is provided, which is used to attach the substrate to the top surface of the silicon carbide ingot, and the mechanical gripper pulls the substrate to peel the wafer off the silicon carbide ingot.

[0033] Here, because the moving work platform exerts a fixed downward pull on the bottom of the silicon carbide ingot, by attaching a substrate to the surface of the silicon carbide ingot and pulling the substrate upward with a mechanical gripper, an upward pull is applied to the top of the silicon carbide ingot. The silicon carbide ingot is subjected to a pull in the opposite direction and perpendicular to its end face, so the wafer can be peeled off from the silicon carbide ingot.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) Compared with the wire saw processing technology, the present invention processes the preset plane of the ingot by scanning with a laser beam, so that the stripped wafer forms a relatively flat stripping surface, reducing the roughness of the stripping surface and reducing the material loss of subsequent grinding.

[0036] (2) Existing laser peeling is prone to uneven stress, which seriously affects the yield. However, the present invention forms burst points by performing secondary cross laser scanning at a certain range of scanning line spacing. The cracks formed by the burst points expand and overlap to form a loosely bonded, easily broken, brittle overall peeling layer, which reduces the peeling tensile stress of the wafer.

[0037] (3) Using a xenon lamp as a heat source, its light spot can effectively cover the preset plane. The xenon lamp can uniformly heat the modified layer so that the internal stress distribution of the modified layer is uniform. The tensile stress caused by the temperature difference can further reduce the generation of cracks, form a good peeling effect, and improve the stability of peeling. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the apparatus for laser stripping silicon carbide ingots according to the present invention;

[0039] Figure 2 This is a schematic diagram of a laser beam illuminating a pre-defined plane of a silicon carbide ingot;

[0040] Figure 3 This is the path diagram for the first laser scan;

[0041] Figure 4 This is a path diagram of the laser performing the second scan;

[0042] Figure 5 This is a schematic diagram showing multiple burst points formed on a preset plane after secondary laser processing;

[0043] Figure 6 This is a schematic diagram of a xenon lamp illuminating a modified layer.

[0044] Figure 7 This is a schematic diagram of a substrate being attached to the top of a silicon carbide ingot;

[0045] Figure 8 This is a schematic diagram of the preset plane formed when the scan line spacing is 50μm;

[0046] Figure 9 This is a schematic diagram of the modified layer formed when the scan line spacing is 50 μm;

[0047] Figure 10 This is a schematic diagram of the peeling surface after a silicon carbide ingot peels off a wafer when the scan line spacing is 50 μm.

[0048] Figure 11 This is a schematic diagram of the preset plane formed when the scan line spacing is 30μm;

[0049] Figure 12 This is a schematic diagram of the modified layer formed when the scan line spacing is 30 μm;

[0050] Figure 13 This is a schematic diagram of the peeling surface after a silicon carbide ingot peels off a wafer when the scan line spacing is 30μm.

[0051] Figure 14 This is a schematic diagram of the preset plane formed when the scan line spacing is 10μm;

[0052] Figure 15 This is a schematic diagram of the modified layer formed when the scan line spacing is 10 μm;

[0053] Figure 16 This is a schematic diagram of the peeling surface after a silicon carbide ingot peels off a wafer when the scan line spacing is 10μm.

[0054] Figure 17 This is a schematic diagram of the preset plane formed when the scan line spacing is 60μm;

[0055] Figure 18 This is a schematic diagram of the modified layer formed when the scan line spacing is 60 μm;

[0056] Figure 19 This is a schematic diagram of the preset plane formed when the scan line spacing is 8μm;

[0057] Figure 20 This is a schematic diagram of the modified layer formed when the scan line spacing is 8μm;

[0058] Figure 21 This is a schematic diagram of the peeled surface of a silicon carbide ingot after peeling off a wafer when the scan line spacing is 8μm.

[0059] In the figure: 1. Ultrafast laser, 2. Attenuator, 3. Aperture, 4. Beam expander, 5. Objective lens, 6. CCD camera, 7. Moving work platform, 8. Xenon lamp, 9. Silicon carbide ingot, 10. Modified layer, 11. Substrate. Detailed Implementation

[0060] The accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0061] Example 1:

[0062] like Figures 1-7 As shown, a device for laser stripping of silicon carbide ingots consists of an ultrafast laser 1, an attenuator 2, an aperture 3, a beam expander 4, an objective lens 5, a CCD camera 6, and a moving work platform 7, and is also equipped with an external xenon lamp 8.

[0063] The silicon carbide ingot 9 is fixedly placed on the mobile working platform 7. The ultrafast laser 1 outputs a Gaussian laser beam, which enters the objective lens 5 after being transmitted through the attenuator 2, aperture 3, and beam expander 4. The objective lens 5 focuses the laser beam onto a preset plane at a preset depth inside the silicon carbide ingot 9. At the same time, the CCD camera 6 is used to adjust and correct the position of the focus.

[0064] After focusing is complete, the mobile work platform 7 moves the silicon carbide ingot 9 in the X / Y / Z three-dimensional directions so that the laser beam can complete the scanning and processing on the preset plane of the silicon carbide ingot 9.

[0065] After the scanning process is completed, the external xenon lamp 8 is moved directly above the silicon carbide ingot 9 so that the xenon lamp 8 can irradiate and heat the modified layer 10 formed by the scanning process.

[0066] After heating, an epoxy resin substrate 11 is attached to the top surface of the silicon carbide ingot 9, and the substrate 11 is pulled to peel the wafer off the silicon carbide ingot 9.

[0067] The xenon lamp 8 can be raised, lowered, and moved laterally via a two-dimensional lifting and moving frame (not shown in the figure) so that the xenon lamp 8 can be moved directly above the silicon carbide ingot 9.

[0068] The device also includes a mechanical gripper (not shown in the figure), which attaches the substrate 11 to the top surface of the silicon carbide ingot 9 and pulls the substrate 11 to peel the wafer off the silicon carbide ingot 9.

[0069] The specific method for achieving wafer stripping using the aforementioned laser stripping device for silicon carbide ingot 9 is as follows:

[0070] S1. Place the silicon carbide ingot 9 on the mobile work platform 7, and start the ultrafast laser 1 so that the focus of the laser beam is aligned with a preset plane at a preset depth inside the silicon carbide ingot 9 (see...). Figure 2 );

[0071] S2. Set the laser beam parameters, and make the laser beam scan the preset plane in a line scanning manner according to the pre-set first scanning direction and a scanning line spacing of 10-50um. Control the trajectory of the moving work platform 7 to realize the movement of the silicon carbide ingot 9 in the X / Y / Z three-dimensional directions, so that the laser scanning path covers the entire preset plane, and complete the first scan (see...). Figure 3 );

[0072] S3. Maintaining the same laser beam parameters, only change the scanning direction of the laser beam, causing the laser beam to scan the preset plane again in a second scanning direction perpendicular to the first scanning direction. Similarly, control the moving work platform 7 to move the silicon carbide ingot 9 so that the laser scanning path covers the entire preset plane again, completing the second scan (see...). Figure 4 );

[0073] S4. After laser processing is completed, multiple planar burst points are formed at the intersections of the first and second scanning paths (see...). Figure 5 In this way, a loosely structured modified layer 10 was prepared;

[0074] S5. Using xenon lamp 8 as a heat source, irradiate and heat the modified layer 10 for 1-2 hours (see...). Figure 6 );

[0075] S6. After heating is completed, since the moving work platform 7 exerts a fixed downward pull on the bottom of the silicon carbide ingot 9, by attaching a substrate 11 to the surface of the silicon carbide ingot 9 and pulling the substrate 11 upward, an upward pull is applied to the top of the silicon carbide ingot 9. The silicon carbide ingot 9 is subjected to a pull in the opposite direction and perpendicular to its end face, so the wafer can be peeled off from the silicon carbide ingot 9.

[0076] In this embodiment, the ultrafast laser 1 is a PHAROS solid-state laser manufactured by LIGHT CONVERSION in Lithuania, which has good beam quality and stable oscillation, with pulse width, wavelength, and repetition frequency of 1-15 ps, 150-1030 nm, and 1-200 MHz, respectively. The objective lens 5 is a 50x near-infrared objective lens (PAL-50-NIR-HR-LC00) manufactured by Sigma Opto-Electronics in Japan. The moving work platform 7 is a three-axis precision electric moving work platform (X / Y / Z). The moving work platform 7 is controlled by a host computer to move along a set trajectory, realizing the movement of the sample in the X / Y / Z dimensions to complete the laser scanning.

[0077] In this embodiment, the preset depth refers to the distance between the preset plane and the top surface of the silicon carbide ingot 9, and the preset depth generally ranges from 300 to 1000 μm. Since the target thickness of the wafer generally ranges from 50 μm to 150 μm, the specific preset depth can be set according to actual production needs and is not limited here. However, the preset depth of the material must be greater than the target thickness of the wafer to be peeled. The preset depth set in this invention exceeds the thickness of the peeled wafer by at least 100 μm. The purpose of this design is to ensure that the top of the ingot has a certain thickness to withstand the force from above during peeling, thus ensuring stability during wafer peeling. For example, when the target thickness of the wafer is 150 μm, the preset depth can be set to 300 μm, thus ensuring a 150 μm thickness between the top surface of the wafer to be peeled and the top surface of the ingot, which is reasonable. The range of the preset depth set above can be designed according to the specific required wafer thickness and is not limited.

[0078] In this embodiment, the scanning line spacing is 10-50 μm. A smaller laser scanning line spacing results in a denser network of burst points at the overlap of two laser scans. Cracks extend and overlap around these burst points, forming a more fragile modified zone, which is beneficial for subsequent peeling. This reduces the peeling tensile stress required to peel the wafer and lowers the roughness of the unpolished surface of the wafer after peeling. To improve the peeling effect, this invention designs a line spacing range of 10-50 μm because: Generally, the laser pulse width is around 10 μm. If the line spacing is less than 10 μm, due to the inherent pulse width of the laser beam, the two lines will overlap when the line spacing is less than a certain width, wasting scanning energy and potentially causing ablation, affecting the peeling effect. Conversely, if the line spacing exceeds 50 μm, the burst points formed by the modified layer 10 will be relatively loose, resulting in excessive peeling tensile stress, also affecting the peeling effect. It should be noted that this is only a preferred method; the operator can set the scanning line spacing according to the actual ideal peeling tensile stress.

[0079] The present invention sets the irradiation heating time of the modified layer 10 by the xenon lamp 8 to 1-2 hours. This is based on ensuring uniform heating of the modified layer 10 within a certain time range, while avoiding excessive heat caused by excessive heating time, thus reducing energy consumption. This time range can be set according to actual conditions; this is just a preferred example.

[0080] In this embodiment, the scanning angle range of the first scanning direction relative to the preset plane is 0-360 degrees. That is, the laser beam in this invention can begin scanning in any direction on the preset plane, as long as the first scanning direction and the second scanning direction remain perpendicular to each other. It should be noted that the scanning direction described here refers to the direction of the starting point of the laser path on the preset plane when performing laser path opening scanning. For example, in... Figure 3 In the first scanning direction, the laser beam starts from the upper left corner of the preset plane and scans in a 180-degree direction, presenting a rectangular path for back-and-forth scanning, fully covering the preset plane according to the set scan line spacing; similarly, in Figure 4 In the second scan, the laser beam starts from the lower left corner of the preset plane and scans in a 270-degree direction, presenting a rectangular path for back-and-forth scanning. It fully covers the preset plane according to the set scan line spacing, ultimately forming an image on the preset plane as shown in the image. Figure 5 The preset area shown has multiple burst points.

[0081] In this embodiment, the laser beam spot can be one or more of the following: Gaussian spot, square flat-top spot, circular flat-top spot, elliptical flat-top spot, and rhomboid flat-top spot, or any combination thereof.

[0082] In this embodiment, the xenon lamp 8 is a cylindrical short-arc xenon lamp with a filter inside, the wavelength range of the output light is 400-600nm, the spot size is 70-150mm, and the power is greater than 10kW.

[0083] In this embodiment, the silicon carbide ingot 9 can be replaced with other widely used semiconductor substrate materials, such as silicon carbide, gallium nitride, silicon, or sapphire.

[0084] This invention first uses laser secondary processing at a predetermined scanning line spacing to form a loosely bonded, easily separable, brittle, layered structure within the material. This helps reduce the tensile stress during wafer peeling and improves the peeling effect of silicon carbide wafers. After the modified layer 10 is formed, a high-power xenon lamp 8 is used to irradiate and heat the modified layer 10. The xenon lamp 8 has a large spot size, which can effectively cover the entire processing area, achieving uniform heating of the modified area. This results in a uniform stress distribution within the modified layer 10, allowing the initial cracks to further propagate. Finally, applying opposing tensile forces at both ends of the ingot achieves wafer peeling. The method of this invention is simple and feasible, producing a smooth peeled wafer surface with reliable quality.

[0085] Example 2:

[0086] In this embodiment, the process parameters of the laser beam emitted by the ultrafast laser 1 are set as follows: single pulse energy 5.7 μJ, repetition frequency 1 kHz, scanning speed 2 mm / s, scanning spacing 50 μm, and pulse width 15 ps. The required wafer size to be peeled off is set to 5 mm x 5 mm.

[0087] The specific process of laser ablation of silicon carbide ingots is as follows:

[0088] S1. A silicon carbide ingot 9 is fixedly placed on the mobile work platform 7. The ultrafast laser 1 emits a laser beam and controls the mobile work platform 7 to move in the Z direction so that the height of the ingot changes and the focus of the laser beam is located on a preset plane with a depth of 300μm inside the silicon carbide ingot 9.

[0089] S2. Activate the ultrafast laser 1, and guide the laser beam in a line scan manner, pressing... Figure 3 The first scanning direction and 50µm scanning line spacing shown are used to scan the preset plane. The trajectory of the moving work platform 7 is controlled to move the silicon carbide ingot 9 in the X / Y / Z directions, so that the laser scanning path covers the entire preset plane, completing the first scan (see...). Figure 3 );

[0090] S3. Change the scanning direction of the laser beam, so that the laser beam follows... Figure 4 The second scanning direction shown performs a second scanning process on the preset plane. Similarly, the movement of the silicon carbide ingot 9 is controlled by the moving work platform 7 to ensure that the laser scanning path covers the entire preset plane again, completing the second scan (see...). Figure 4 );

[0091] S4. After laser processing is completed, multiple planar burst points are formed at the intersections of the first and second scanning paths (see...). Figure 8 In this way, a loosely structured modified layer 10 was prepared (see...). Figure 9 );

[0092] S5. Use a short-arc xenon lamp 8 with a power of 100kW and a spot size of 120mm to irradiate the modified layer 10 for 1 hour.

[0093] S6. A substrate 11 is adhered to the surface of a silicon carbide ingot 9 using epoxy resin. The substrate 11 is pulled to peel the wafer off the ingot, resulting in a peeled wafer. The peeled surface of the wafer is shown below. Figure 10 As shown.

[0094] See Figures 8-10 In summary, when the two laser scans are spaced 50 μm apart, a burst point is formed at the overlap of the two scans. Cracks extend and overlap around this burst point, forming a relatively fragile modified layer 10, which is beneficial for subsequent peeling. The required peeling tensile stress of the wafer, measured using the above method, is 6.67 MPa, and the roughness of the unpolished peeled surface is measured to be 6.7 μm. Therefore, both the required tensile stress and roughness values ​​are very low, resulting in a good peeling effect.

[0095] Example 3:

[0096] This embodiment is similar to Embodiment 2, maintaining the same laser parameters and the required wafer size to be lifted, only changing the scan line spacing to 30μm. The specific process of laser lift-off of silicon carbide ingots is as follows:

[0097] S1. A silicon carbide ingot 9 is fixedly placed on the mobile work platform 7. The ultrafast laser 1 emits a laser beam and controls the mobile work platform 7 to move in the Z direction so that the height of the ingot changes and the focus of the laser beam is located on a preset plane with a depth of 300μm inside the silicon carbide ingot 9.

[0098] S2. Activate the ultrafast laser 1, and guide the laser beam in a line scan manner, pressing... Figure 3 The first scanning direction and the 30um scanning line spacing shown are used to scan and process the preset plane. The trajectory of the moving work platform is controlled to realize the movement of the silicon carbide ingot 9 in the three dimensions of X / Y / Z so that the scanning path of the laser covers the entire preset plane and completes the first scan.

[0099] S3. Change the scanning direction of the laser beam, so that the laser beam follows... Figure 4 The second scanning direction shown scans the preset plane again. Similarly, the movement of the silicon carbide ingot 9 is achieved by controlling the moving work platform 7 so that the laser scanning path covers the entire preset plane again, completing the second scan.

[0100] S4. After laser processing is completed, multiple planar burst points are formed at the intersections of the first and second scanning paths (see...). Figure 11 In this way, a loosely structured modified layer 10 was prepared (see...). Figure 12 );

[0101] S5. Use a short-arc xenon lamp 8 with a power of 100kW and a spot size of 120mm to irradiate the modified layer 10 for 1 hour.

[0102] S6. A substrate 11 is adhered to the surface of a silicon carbide ingot 9 using epoxy resin. The substrate 11 is pulled to peel the wafer off the ingot, resulting in a peeled wafer. The peeled surface of the wafer is shown below. Figure 13 As shown.

[0103] See Figures 11-13 In summary, when the two laser scans are spaced at the same interval of 30 μm, the number of burst points formed at the overlapping area is higher than that at 50 μm. The burst points formed by the cross-scan are relatively dense, resulting in a stronger crack propagation effect. The resulting modified layer 10 is more fragile and significantly narrower, which is beneficial for subsequent wafer peeling and roughness reduction. The required peeling tensile stress of the wafer was measured to be 4.93 MPa using the above method, and the roughness of the unpolished peeled surface was measured to be 3.8 μm. This embodiment reduces the required tensile stress and roughness values ​​compared to the 50 μm spacing in Example 2, resulting in better peeling performance.

[0104] Example 4:

[0105] This embodiment is similar to Embodiment 2, maintaining the same laser parameters and the required wafer size to be lifted, only changing the scan line spacing to 10μm. The specific process of laser lift-off of silicon carbide ingots is as follows:

[0106] S1. A silicon carbide ingot 9 is fixedly placed on the mobile work platform 7. The ultrafast laser 1 emits a laser beam and controls the mobile work platform 7 to move in the Z direction so that the height of the ingot changes and the focus of the laser beam is located on a preset plane with a depth of 300μm inside the silicon carbide ingot 9.

[0107] S2. Activate the ultrafast laser 1, and guide the laser beam in a line scan manner, pressing... Figure 3 The first scanning direction and the 10µm scanning line spacing shown are used to scan and process the preset plane. The trajectory of the moving work platform 7 is controlled to realize the movement of the silicon carbide ingot 9 in the three dimensions of X / Y / Z so that the scanning path of the laser covers the entire preset plane and completes the first scan.

[0108] S3. Change the scanning direction of the laser beam, so that the laser beam follows... Figure 4 The second scanning direction shown scans the preset plane again. Similarly, the movement of the silicon carbide ingot 9 is achieved by controlling the moving work platform 7 so that the laser scanning path covers the entire preset plane again, completing the second scan.

[0109] S4. After laser processing is completed, multiple planar burst points are formed at the intersections of the first and second scanning paths (see...). Figure 14 In this way, a loosely structured modified layer 10 was prepared (see...). Figure 15 );

[0110] S5. Use a short-arc xenon lamp with a power of 100kW and a spot size of 120mm to irradiate the modified layer for 1 hour.

[0111] S6. A substrate 11 is adhered to the surface of a silicon carbide ingot 9 using epoxy resin. The substrate 11 is pulled to peel the wafer off the ingot, resulting in a peeled wafer. The peeled surface of the wafer is shown below. Figure 16 As shown.

[0112] See Figures 14-16 In summary, when the two laser scans are spaced 10 μm apart, the linewidth and scanning spacing overlap, resulting in a high density of crack points formed by the cross-scanning. This damages the internal crystal structure of the silicon carbide ingot 9, further enhancing the crack propagation effect. The resulting modified layer 10 is very fragile, which is beneficial for subsequent wafer peeling and roughness reduction. The required peeling tensile stress for the wafer, measured using the above method, is 4.392 MPa, and the roughness of the unpolished peeled surface is measured to be 1.678 μm. This embodiment reduces both the required tensile stress and roughness compared to the 30 μm spacing in Example 3, resulting in a very good peeling effect.

[0113] Example 5:

[0114] This embodiment is similar to Embodiment 2, maintaining the same laser parameters and the required wafer size to be lifted, only changing the scan line spacing to 60μm. The specific process of laser lift-off of silicon carbide ingots is as follows:

[0115] S1. A silicon carbide ingot 9 is fixedly placed on the mobile work platform 7. The ultrafast laser 1 emits a laser beam and controls the mobile work platform 7 to move in the Z direction so that the height of the ingot changes and the focus of the laser beam is located on a preset plane with a depth of 300μm inside the silicon carbide ingot 9.

[0116] S2. Activate the ultrafast laser 1, and guide the laser beam in a line scan manner, pressing... Figure 3 The first scanning direction and the 60um scanning line spacing shown are used to scan and process the preset plane. The trajectory of the moving work platform 7 is controlled to realize the movement of the silicon carbide ingot 9 in the three dimensions of X / Y / Z so that the scanning path of the laser covers the entire preset plane and completes the first scan.

[0117] S3. Change the scanning direction of the laser beam, so that the laser beam follows... Figure 4The second scanning direction shown scans the preset plane again. Similarly, the movement of the silicon carbide ingot 9 is achieved by controlling the moving work platform 7 so that the laser scanning path covers the entire preset plane again, completing the second scan.

[0118] S4. After laser processing is completed, multiple planar burst points are formed at the intersections of the first and second scanning paths (see...). Figure 17 In this way, a loosely structured modified layer 10 was prepared (see...). Figure 18 );

[0119] S5. Use a short-arc xenon lamp 8 with a power of 100kW and a spot size of 120mm to irradiate the modified layer 10 for 1 hour.

[0120] S6. Use epoxy resin to attach a substrate 11 to the surface of silicon carbide ingot 9, pull the substrate 11 to peel the wafer off the ingot, and obtain the peeled wafer.

[0121] See Figure 17 and Figure 18 In summary, when the distance between two laser scans is the same and 60 μm, which is greater than 50 μm, the scanning distance is too large, resulting in looser burst points. Fewer cracks are observed inside the modified layer 10, and the cracks between the modified lines cannot effectively expand to form connections. The structure remains in its initial state, without causing structural damage and failing to provide favorable conditions for peeling, thus leading to a lower peeling success rate. The required peeling tensile stress of the wafer, measured using the above method, is 9.172 MPa, and the roughness of the unpolished peeled surface is measured to be 9.178 μm. The values ​​in this embodiment are significantly higher than the required tensile stress and roughness values ​​for the 50 μm spacing in Example 2. Furthermore, the height of the modified layer is also increased, resulting in a lower peeling success rate and an uneven peeled surface requiring subsequent polishing, leading to higher material consumption and production costs.

[0122] Example 6:

[0123] This embodiment is similar to Embodiment 2, maintaining the same laser parameters and the required wafer size to be lifted, only changing the scan line spacing to 8μm. The specific process of laser lift-off of silicon carbide ingots is as follows:

[0124] S1. A silicon carbide ingot 9 is fixedly placed on the mobile work platform 7. The ultrafast laser 1 emits a laser beam and controls the mobile work platform 7 to move in the Z direction so that the height of the ingot changes and the focus of the laser beam is located on a preset plane with a depth of 300μm inside the silicon carbide ingot 9.

[0125] S2. Activate the ultrafast laser 1, and guide the laser beam in a line scan manner, pressing... Figure 3The first scanning direction and the 8µm scanning line spacing shown are used to scan and process the preset plane. The trajectory of the moving work platform 7 is controlled to realize the movement of the silicon carbide ingot 9 in the three dimensions of X / Y / Z so that the scanning path of the laser covers the entire preset plane and completes the first scan.

[0126] S3. Change the scanning direction of the laser beam, so that the laser beam follows... Figure 4 The second scanning direction shown scans the preset plane again. Similarly, the movement of the silicon carbide ingot 9 is achieved by controlling the moving work platform 7 so that the laser scanning path covers the entire preset plane again, completing the second scan.

[0127] S4. After laser processing is completed, multiple planar burst points are formed at the intersections of the first and second scanning paths (see...). Figure 19 In this way, a loosely structured modified layer 10 was prepared (see...). Figure 20 );

[0128] S5. Use a short-arc xenon lamp 8 with a power of 100kW and a spot size of 120mm to irradiate the modified layer 10 for 1 hour.

[0129] S6. A substrate 11 is adhered to the surface of a silicon carbide ingot 9 using epoxy resin. The substrate 11 is pulled to peel the wafer off the ingot, resulting in a peeled wafer. The peeled surface of the wafer is shown below. Figure 21 As shown.

[0130] See Figures 19-21 In summary, when the two laser scans are spaced 8 μm apart (less than 10 μm), the scan spacing is smaller than the laser ablation linewidth, resulting in overlapping ablation areas. While the ablation points are densely packed, the excessively small spacing leads to severe internal ablation of the material, causing fractures in the cracked areas. Furthermore, the small spacing makes it easy for adjacent cracks to misalign and overlap, all of which are detrimental to subsequent peeling. The required peeling tensile stress for the wafer, measured using the above method, is 4.524 MPa, and the roughness of the unpolished peeled surface is measured to be 2.594 μm. Compared to the 10 μm spacing in Example 4, both the required tensile stress and roughness values ​​are increased. Therefore, an excessively low scan line spacing does not necessarily improve the peeling effect.

[0131] In summary, the 10-50µm line spacing range designed in this invention is reasonable. Within this range, relatively ideal peel tensile stress and peel roughness are obtained, resulting in better peel performance.

[0132] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for laser ablation of silicon carbide ingots, characterized in that, Includes the following steps: S1. Align the focus of the laser beam with a preset plane at a preset depth inside the silicon carbide ingot (9), where the preset depth refers to the distance between the preset plane and the top surface of the silicon carbide ingot (9). S2. The laser beam is made to scan the preset plane in a line scanning manner, according to the pre-set first scanning direction and the scanning line spacing of 10-50um, so that the scanning path covers the entire preset plane and the first scan is completed. The scanning angle range of the first scanning direction relative to the preset plane is 0-360 degrees. S3. Change only the scanning direction of the laser beam, and make the laser beam scan the preset plane again in a second scanning direction that is perpendicular to the first scanning direction, so that the scanning path covers the entire preset plane again, and the second scan is completed. S4. After laser processing is completed, multiple planar burst points are formed at multiple intersections of the first scanning path and the second scanning path, thereby preparing a loosely structured modified layer (10). S5. Use a xenon lamp (8) as a heat source to irradiate and heat the modified layer (10) for 1-2 hours; S6. After heating is completed, apply opposite pulling forces perpendicular to the end face of the silicon carbide ingot (9) to the top and bottom ends of the silicon carbide ingot (9) to peel the wafer off the silicon carbide ingot (9). The xenon lamp (8) is a cylindrical short-arc xenon lamp with a filter inside. The wavelength range of the output light is 400-600nm, the spot size is 70-150mm, and the power is greater than 10kW. The laser beam has a wavelength of 150nm-1030nm, a pulse width of 1-15ps, and a repetition frequency of 1-10KHz.

2. The method for laser ablation of silicon carbide ingots according to claim 1, characterized in that, The preset depth exceeds the thickness of the wafer obtained by stripping by at least 100 μm.

3. The method for laser ablation of silicon carbide ingots according to claim 1, characterized in that, The laser beam spot is one of the following: Gaussian spot, square flat-top spot, circular flat-top spot, elliptical flat-top spot, or rhomboid flat-top spot.

4. An apparatus for laser lift-off of silicon carbide ingots, used for performing the laser lift-off method for silicon carbide ingots as described in any one of claims 1-3, characterized in that, Includes an ultrafast laser (1), an attenuator (2), an aperture (3), a beam expander (4), an objective lens (5), a CCD camera (6), a mobile work platform (7), and a xenon lamp (8); The silicon carbide ingot (9) is fixedly placed on the mobile working platform (7). The ultrafast laser (1) outputs a Gaussian laser beam, which enters the objective lens (5) after being transmitted through the attenuator (2), aperture (3), and beam expander (4). The objective lens (5) focuses the laser beam onto a preset plane at a preset depth inside the silicon carbide ingot (9). At the same time, the CCD camera (6) is used to adjust and correct the position of the focus. The Gaussian laser beam has a wavelength of 150nm-1030nm, a pulse width of 1-15ps, and a repetition frequency of 1-10KHz. After focusing, the moving work platform (7) moves the silicon carbide ingot (9) in the X / Y / Z three-dimensional directions so that the laser beam completes the scanning processing on the preset plane of the silicon carbide ingot (9) according to steps S2-S4. After the scanning process is completed, the external xenon lamp (8) is moved directly above the silicon carbide ingot (9) so that the xenon lamp (8) can irradiate and heat the modified layer (10) formed by the scanning process. The xenon lamp (8) is a cylindrical short-arc xenon lamp with a filter inside. The wavelength range of the output light is 400-600nm, the spot size is 70-150mm, and the power is greater than 10kW. After heating, a substrate (11) is attached to the top surface of the silicon carbide ingot (9), and the substrate (11) is pulled to peel the wafer off the silicon carbide ingot (9).

5. The apparatus for laser lift-off of silicon carbide ingots according to claim 4, characterized in that, The substrate (11) is bonded to the top surface of the silicon carbide ingot (9) using epoxy resin.

6. The apparatus for laser lift-off of silicon carbide ingots according to claim 4, characterized in that, A mechanical gripper is provided to attach the substrate (11) to the top surface of the silicon carbide ingot (9) and pull the substrate (11) to peel the wafer off the silicon carbide ingot (9).

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