Method and device for laser stripping of silicon carbide ingot

Abstract

The present invention provides a method and apparatus for laser stripping a silicon carbide ingot. The method first transmits an ultrashort pulse laser beam through the first end face of the silicon carbide ingot and focuses it on a set depth layer of the ingot. A cavity-modified region and a crack-modified region are generated above the set depth layer, respectively, and scanned to form the cavity-modified layer and the crack-modified layer. A short pulse laser beam then transmits the second end face of the silicon carbide ingot and focuses it on the cavity-modified region. The beam scatters and propagates within the cavity-modified region, causing the heat from the short pulse laser beam to act on the cavity-modified region, causing cracks within the crack-modified region to grow laterally outward. Scanning is then performed to connect cracks within adjacent cavity-modified regions within the cavity-modified layer through lateral growth. This reduces the amount and length of cracks in the modified layer extending longitudinally along the silicon carbide ingot, increases the number and length of lateral crack growth, reduces cutting loss, and reduces waste.

Description

Technical Field

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

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

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

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

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

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

[0007] In a first aspect, the present invention provides a method for laser stripping a silicon carbide ingot, wherein the silicon carbide ingot to be cut has a first end face and a second end face opposite to each other. The method for laser stripping the silicon carbide ingot comprises:

[0008] After passing an ultrashort pulse laser beam through a first end face of the silicon carbide ingot to be cut, the ultrashort pulse laser beam is focused at a set depth layer position of the silicon carbide ingot to generate a cavity modification forming region and a crack modification forming region above the set depth layer position, respectively; wherein the cavity modification forming region is located between the set depth layer position and the crack modification forming region;

[0009] After controlling the ultrashort pulse laser beam to pass through the first end face, the laser beam is focused on a set depth layer of the silicon carbide ingot and scanned at the set depth layer to form a cavity modification layer and a crack modification layer above the set depth layer, respectively; wherein the cavity modification layer is composed of a plurality of cavity modification forming regions, the crack modification layer is composed of a plurality of crack modification forming regions, and the cavity modification layer is located between the set depth layer and the crack modification layer;

[0010] After passing a short pulse laser beam through the second end face of the silicon carbide ingot, the beam is focused on the void modification forming region and scattered and propagated in the void modification forming region, causing cracks in the void modification forming region to grow laterally outward;

[0011] After controlling the short pulse laser beam to pass through the second end face, the laser beam is focused on the void modified layer and scanned at a set depth layer so that cracks in any adjacent void modified areas in the void modified layer are connected together by lateral growth;

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

[0013] In the above-described scheme, an ultrashort pulse laser is first used to transmit the ultrashort pulse laser beam through the first end face of the silicon carbide ingot and then focus it at a set depth layer position of the silicon carbide ingot to generate a cavity-modified formation region and a crack-modified formation region above the set depth layer position, respectively. The focus of the ultrashort pulse laser beam is then controlled to scan the set depth layer of the silicon carbide ingot to form the cavity-modified layer and the crack-modified layer. After ultrashort pulse laser stealth cutting, a short pulse laser with a slightly wider pulse width is then used to transmit the short pulse laser beam through the second end face of the silicon carbide ingot and then focus it at the cavity-modified formation region. The short pulse laser beam is then scattered and propagated in the cavity-modified formation region, so that the heat of the short pulse laser beam is primarily applied to the cavity-modified formation region, causing cracks in the crack-modified formation region to grow laterally outward. The focus of the short pulse laser beam is then controlled to scan the cavity-modified layer so that cracks in any adjacent cavity-modified formation regions in the cavity-modified layer are connected by lateral growth.

[0014] Compared to existing laser silicon ingot cutting processes, the ultrashort pulse laser used in this process can, after penetrating the first end face of the silicon carbide ingot, generate a void-modified region and a crack-modified region above the predetermined depth layer at the focus of the ultrashort pulse laser beam. Scanning then forms the void-modified layer and the crack-modified layer, respectively, refining and differentiating the modified layers in the prior art. Subsequently, when a short-pulse laser beam is used, it is focused on the void-modified region after penetrating the second end face of the silicon carbide ingot. The focus of the short-pulse laser beam is above the focus of the ultrashort pulse laser beam, rather than at the same depth as in the prior art. This allows the laser to scatter and propagate within the void-modified region, causing cracks within the void-modified region to grow laterally outward. Furthermore, scanning allows cracks within any adjacent void-modified regions in the void-modified layer to connect through lateral growth. Because the short-pulse laser beam enters the cavity-modifying region of the silicon carbide ingot through the second end face, it does not need to pass through the crack-modifying region above the cavity-modifying region. This prevents cracks in the crack-modifying region from scattering the short-pulse laser beam, improves laser energy concentration, and thereby improves heating efficiency and crack extension efficiency in the cavity-modifying region. Furthermore, during the process of focusing the short-pulse laser beam on the cavity-modifying region and heating the cavity-modifying region, the crack-modifying region blocks crack growth, thereby limiting the upward growth length of the crack in the cavity-modifying region to a region below the crack-modifying region. This limits the longitudinal growth length of the crack to a smaller height range, thereby improving crack extension efficiency, minimizing the longitudinal extension of the crack, and minimizing slice loss. That is, by subdividing the modified layer into a void modified layer and a crack modified layer, and then making the short pulse laser beam pass through the second end face of the silicon carbide ingot and focus on the void modified layer, the focus position of the short pulse laser beam is designed more accurately and reasonably, not only making the upper and lower height difference of the focus of the short pulse laser beam fluctuate less (because the upper and lower height difference of the void modified forming area must be smaller than the upper and lower height difference of the modified layer composed of the crack modified forming area and the void modified forming area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the void modified layer, through The crack modification forming area thereon blocks the cracks in the void modification forming area from growing vertically upward, limits the length of the cracks growing vertically to a smaller height range, optimizes the focusing position of the short-pulse laser beam, reduces the amount and length of cracks in the modified layer extending longitudinally along the silicon carbide ingot, and thus directs more laser energy to the lateral outward growth of the cracks, thereby increasing the number and length of lateral crack growth, enabling the cutting of thinner silicon carbide wafers, and reducing the cutting loss thickness. More silicon carbide wafers can be cut from the same silicon carbide ingot, reducing waste.

[0015] In a specific embodiment, the thickness of the silicon carbide ingot to be cut is not more than 5 mm, and the depth layer is set to be between 2 and 3 mm from the first end face and the second end face, taking into account the difficulty and energy loss of focusing on the cavity modification formation area after passing through the second end face of the silicon carbide ingot, thereby preventing large energy loss.

[0016] In a specific embodiment, the pulse width of the short pulse laser beam is greater than 50ns, and the wavelength of the short pulse laser beam is 500-1100nm, which is convenient for better reducing the amount and length of cracks in the modified layer along the longitudinal extension of the silicon carbide ingot, thereby applying more laser energy to the lateral outward growth of the cracks, increasing the number of lateral crack growth and the length of crack growth.

[0017] In a specific embodiment, the pulse width of the ultrashort pulse laser beam is 243fs-900fs, and the wavelength of the ultrashort pulse laser beam is 500-1100nm, which further improves the modification effect of the cavity modification forming area and the crack modification forming area generated above the focus of the ultrashort pulse laser beam.

[0018] In a specific embodiment, after a short pulse laser beam passes through the second end face, it is focused on the void modification forming area and scattered and propagated in the void modification forming area, so that the cracks in the void modification forming area grow laterally outward, including: adjusting the polarization state of the short pulse laser beam so that the electron propagation direction expands along the silicon carbide lattice direction of the silicon carbide ingot, forming a 3-5° laterally growing crack, so as to better reduce the amount and length of the cracks in the modified layer along the longitudinal expansion of the silicon carbide ingot, thereby applying more laser energy to the lateral outward growth of the cracks, increasing the number of lateral crack growth and the crack growth length.

[0019] In one specific embodiment, controlling the focus of an ultrashort pulse laser beam to scan a set depth layer of a silicon carbide ingot includes: controlling the focus of the ultrashort pulse laser beam to scan a plurality of parallel first cutting paths at the set depth layer of the silicon carbide ingot, wherein the interval between any two adjacent first cutting paths is 10-25 μm. Controlling the focus of a short pulse laser beam to scan a void-modified layer includes: controlling the focus of the short pulse laser beam to scan a plurality of parallel second cutting paths at the void-modified layer, wherein each second cutting path is directly above a first cutting path, thereby facilitating setting an appropriate width of the silicon carbide explosion point interval and simplifying the scanning difficulty.

[0020] In a specific embodiment, controlling the focus of a short pulse laser beam to scan a plurality of parallel second cutting paths in the void modification layer includes: controlling the focus of the short pulse laser beam to scan at each second cutting path for a number of times greater than or equal to three times, achieving connection of burst point cracks by using a short pulse laser beam for multiple processing and continuous heat injection, increasing the amount and length of lateral crack growth in the crack modification formation area, and making the cracks extending from adjacent second cutting paths connect together faster, thereby facilitating the separation of the silicon carbide ingot into multiple silicon carbide wafers through implicit crack induction growth.

[0021] In a second aspect, the present invention also provides a device for laser stripping of a silicon carbide ingot, wherein the silicon carbide ingot to be cut has a first end face and a second end face relative to each other. The device for laser stripping of a silicon carbide ingot comprises: a stage, an ultrashort pulse laser system, a first scanning system, a short pulse laser system, a second scanning system and a stripping system. The stage is used to fix the silicon carbide ingot to be cut. The ultrashort pulse laser system is used to focus an ultrashort pulse laser beam on a set depth layer position of the silicon carbide ingot after passing it through the first end face of the silicon carbide ingot to be cut, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position, respectively; wherein the cavity modification forming region is located between the set depth layer position and the crack modification forming region. The first scanning system is used to control an ultrashort pulse laser beam to pass through the first end face, focus on a set depth layer of the silicon carbide ingot, and scan through the set depth layer to form a void modification layer and a crack modification layer above the set depth layer, respectively. The void modification layer is composed of multiple void modification formation regions, and the crack modification layer is composed of multiple crack modification formation regions, with the void modification layer located between the set depth layer and the crack modification layer. The short pulse laser system is used to control a short pulse laser beam to pass through the second end face of the silicon carbide ingot, focus on the void modification formation region, and scatter and propagate within the void modification formation region, causing cracks within the void modification formation region to grow laterally outward. The second scanning system is used to control a short pulse laser beam to pass through the second end face, focus on the void modification layer, and scan through the set depth layer, so that cracks within any adjacent void modification formation regions in the void modification layer are connected by lateral growth. The stripping system is used to strip a portion of the silicon carbide ingot using the void modification layer as an interface to produce a silicon carbide wafer.

[0022] In the above-described scheme, an ultrashort pulse laser is first used to transmit the ultrashort pulse laser beam through the first end face of the silicon carbide ingot and then focus it at a set depth layer position of the silicon carbide ingot to generate a cavity-modified formation region and a crack-modified formation region above the set depth layer position, respectively. The focus of the ultrashort pulse laser beam is then controlled to scan the set depth layer of the silicon carbide ingot to form the cavity-modified layer and the crack-modified layer. After ultrashort pulse laser stealth cutting, a short pulse laser with a slightly wider pulse width is then used to transmit the short pulse laser beam through the second end face of the silicon carbide ingot and then focus it at the cavity-modified formation region. The short pulse laser beam is then scattered and propagated in the cavity-modified formation region, so that the heat of the short pulse laser beam is primarily applied to the cavity-modified formation region, causing cracks in the crack-modified formation region to grow laterally outward. The focus of the short pulse laser beam is then controlled to scan the cavity-modified layer so that cracks in any adjacent cavity-modified formation regions in the cavity-modified layer are connected by lateral growth.

[0023] Compared to existing laser silicon ingot cutting processes, the ultrashort pulse laser used in this process can, after penetrating the first end face of the silicon carbide ingot, generate a void-modified region and a crack-modified region above the predetermined depth layer at the focus of the ultrashort pulse laser beam. Scanning then forms the void-modified layer and the crack-modified layer, respectively, refining and differentiating the modified layers in the prior art. Subsequently, when a short-pulse laser beam is used, it is focused on the void-modified region after penetrating the second end face of the silicon carbide ingot. The focus of the short-pulse laser beam is above the focus of the ultrashort pulse laser beam, rather than at the same depth as in the prior art. This allows the laser to scatter and propagate within the void-modified region, causing cracks within the void-modified region to grow laterally outward. Furthermore, scanning allows cracks within any adjacent void-modified regions in the void-modified layer to connect through lateral growth. Because the short-pulse laser beam enters the cavity-modifying region of the silicon carbide ingot through the second end face, it does not need to pass through the crack-modifying region above the cavity-modifying region. This prevents cracks in the crack-modifying region from scattering the short-pulse laser beam, improves laser energy concentration, and thereby improves heating efficiency and crack extension efficiency in the cavity-modifying region. Furthermore, during the process of focusing the short-pulse laser beam on the cavity-modifying region and heating the cavity-modifying region, the crack-modifying region blocks crack growth, thereby limiting the upward growth length of the crack in the cavity-modifying region to a region below the crack-modifying region. This limits the longitudinal growth length of the crack to a smaller height range, thereby improving crack extension efficiency, minimizing the longitudinal extension of the crack, and minimizing slice loss. That is, by subdividing the modified layer into a void modified layer and a crack modified layer, and then making the short pulse laser beam pass through the second end face of the silicon carbide ingot and focus on the void modified layer, the focus position of the short pulse laser beam is designed more accurately and reasonably, not only making the upper and lower height difference of the focus of the short pulse laser beam fluctuate less (because the upper and lower height difference of the void modified forming area must be smaller than the upper and lower height difference of the modified layer composed of the crack modified forming area and the void modified forming area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the void modified layer, through The crack modification forming area thereon blocks the cracks in the void modification forming area from growing vertically upward, limits the length of the cracks growing vertically to a smaller height range, optimizes the focusing position of the short-pulse laser beam, reduces the amount and length of cracks in the modified layer extending longitudinally along the silicon carbide ingot, and thus directs more laser energy to the lateral outward growth of the cracks, thereby increasing the number and length of lateral crack growth, enabling the cutting of thinner silicon carbide wafers, and reducing the cutting loss thickness. More silicon carbide wafers can be cut from the same silicon carbide ingot, reducing waste.

[0024] In a specific embodiment, the ultrashort pulse laser system and the short pulse laser system are both arranged above the stage. The device for laser stripping of silicon carbide ingots also includes: a clamping and flipping mechanism, which is used to clamp and flip the silicon carbide ingot held on the stage so that the first end face or the second end face of the silicon carbide ingot faces upward. When the ultrashort pulse laser system and the short pulse laser system are both arranged above the stage, a clamping and flipping mechanism can be additionally provided. After the ultrashort pulse laser beam emitted by the ultrashort pulse laser system passes through the first end face of the silicon carbide ingot to generate a crack modification layer and a void modification layer in the silicon carbide ingot, the silicon carbide ingot is flipped by the clamping and flipping mechanism so that the second end face of the silicon carbide ingot faces upward, so that the short pulse laser beam emitted by the short pulse laser system can pass through the second end face of the silicon carbide ingot and focus on the void modification formation area to perform crack expansion and extension, thereby improving the efficiency of automated operation.

[0025] In a specific embodiment, the stage fixes the silicon carbide ingot by clamping the side wall of the silicon carbide ingot to be cut, so that the first end face and the second end face of the silicon carbide ingot are not blocked. The ultrashort pulse laser system and the short pulse laser system are respectively arranged above and below the stage. The stage is fixed by clamping the side wall of the silicon carbide ingot, so that the first end face and the second end face of the silicon carbide ingot are not blocked by the stage. Furthermore, the ultrashort pulse laser system can be arranged on the side of the first end face of the silicon carbide ingot, so that the ultrashort pulse laser beam it emits passes through the first end face to process the interior of the silicon carbide ingot. The short pulse laser system can be arranged on the side of the second end face of the silicon carbide ingot, so that the short pulse laser beam it emits passes through the second end face to process the interior of the silicon carbide ingot without flipping the silicon carbide ingot. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figures 2 to 6 The present invention provides a schematic cross-sectional view of the various steps of a method for laser stripping of a silicon carbide ingot, wherein: Figure 3 An actual sample image of a cavity-forming region and a crack-forming region processed using an ultrashort pulse laser beam according to an embodiment of the present invention;

[0028] Figure 7 A schematic structural diagram of a device for laser stripping of a silicon carbide ingot provided in an embodiment of the present invention;

[0029] Figure 8 Based on Figure 7 An apparatus for laser stripping of a silicon carbide ingot, and a flow chart for laser stripping of a silicon carbide ingot;

[0030] Figure 9 A schematic structural diagram of another device for laser stripping of a silicon carbide ingot provided in an embodiment of the present invention;

[0031] Figure 10 Based on Figure 9 The provided device for laser stripping of silicon carbide ingots shows a schematic diagram of optical path transmission when an ultrashort pulse laser beam and a short pulse laser beam are working separately.

[0032] Reference numerals:

[0033] 10-Silicon carbide ingot 21-Set depth layer 22-Void modified layer 23-Crack modified layer DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0035] In order to facilitate understanding of the method for laser stripping of silicon carbide ingots provided by an embodiment of the present invention, the following first describes the application scenario of the method for laser stripping of silicon carbide ingots provided by an embodiment of the present invention. The method for laser stripping of silicon carbide ingots is applied in the process of stripping silicon carbide wafers from silicon carbide ingots, wherein the silicon carbide ingot to be cut is in the shape of a prism or a cylinder, having a first end face and a second end face relative to each other, wherein the first end face can be the front of the silicon carbide ingot, and the second end face is the back of the silicon carbide ingot; the first end face can also be the back of the silicon carbide ingot, and the second end face is the front of the silicon carbide ingot. The following is a detailed description of the method for laser stripping of silicon carbide ingots in conjunction with the accompanying drawings.

[0036] refer to Figures 1 to 5 The method for laser stripping of a silicon carbide ingot provided by an embodiment of the present invention includes:

[0037] Step 10: After transmitting an ultrashort pulse laser beam through the first end face of the silicon carbide ingot 10 to be cut, the ultrashort pulse laser beam is focused at a predetermined depth layer 21 of the silicon carbide ingot 10 to generate a cavity modification forming region and a crack modification forming region above the predetermined depth layer 21, respectively; wherein the cavity modification forming region is located between the predetermined depth layer 21 and the crack modification forming region;

[0038] Step 20: After the ultrashort pulse laser beam passes through the first end face, it is focused on a set depth layer 21 of the silicon carbide ingot 10 and scanned at the set depth layer 21 to form a cavity modified layer 22 and a crack modified layer 23 above the set depth layer 21, respectively; wherein the cavity modified layer 22 is composed of a plurality of cavity modified forming regions, and the crack modified layer 23 is composed of a plurality of crack modified forming regions, and the cavity modified layer 22 is located between the set depth layer 21 and the crack modified layer 23;

[0039] Step 30: After passing through the second end face of the silicon carbide ingot 10, the short pulse laser beam is focused on the cavity modification forming region and scattered and propagated in the cavity modification forming region, causing cracks in the cavity modification forming region to grow laterally outward.

[0040] Step 40: After the short pulse laser beam passes through the second end face, it is focused on the void modified layer 22 and scanned at the set depth layer 21, so that cracks in any adjacent void modified areas in the void modified layer 22 are connected together by lateral growth;

[0041] Step 50: Using the void modified layer 22 as an interface, a portion of the silicon carbide ingot 10 is peeled off to generate a silicon carbide wafer.

[0042] In the above scheme, an ultrashort pulse laser is first used. After the ultrashort pulse laser beam passes through the first end face of the silicon carbide ingot 10, it is focused on the set depth layer 21 position of the silicon carbide ingot 10 to generate a cavity modification forming region and a crack modification forming region above the set depth layer 21 position, respectively. The focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10 to form a cavity modification layer 22 and a crack modification layer 23. After ultrashort pulse laser stealth cutting processing, a short pulse laser with a slightly wider pulse width is used to focus the short pulse laser beam on the cavity modification forming area after passing through the second end face of the silicon carbide ingot 10, and scatter and propagate in the cavity modification forming area, so that the heat of the short pulse laser beam mainly acts on the cavity modification forming area, causing the cracks in the crack modification forming area to grow laterally outward, and the focus of the short pulse laser beam is controlled to scan the cavity modification layer 22, so that the cracks in any adjacent cavity modification forming areas in the cavity modification layer 22 are connected together through lateral growth.

[0043] Compared to existing laser cutting processes for silicon ingots, the ultrashort pulse laser used in this method can, after penetrating the first end face of the silicon carbide ingot 10, generate a void-modified region and a crack-modified region above a predetermined depth layer 21 at the focus of the ultrashort pulse laser beam. Scanning then forms a void-modified layer 22 and a crack-modified layer 23, respectively, thus refining and differentiating the modified layers in the prior art. Subsequently, when a short pulse laser beam is used, the short pulse laser beam is focused on the void-modified region after penetrating the second end face of the silicon carbide ingot 10. The focus of the short pulse laser beam is above the focus of the ultrashort pulse laser beam, rather than at the same depth as in the prior art. This allows the laser to scatter and propagate within the void-modified region, causing cracks within the void-modified region to grow laterally outward. Furthermore, scanning allows cracks within any adjacent void-modified regions in the void-modified layer 22 to connect through lateral growth. Since the short-pulse laser beam is incident on the cavity-modified region of the silicon carbide ingot 10 through the second end face, it does not need to pass through the crack-modified region above the cavity-modified region. This prevents the cracks in the crack-modified region from scattering the short-pulse laser beam, improves the laser energy concentration, and thus improves the heating efficiency and crack extension efficiency of the cavity-modified region. Moreover, during the process of focusing the short-pulse laser beam on the cavity-modified region and heating the cavity-modified region, the crack-modified region can block the growth of cracks, thereby limiting the upward growth length of cracks in the cavity-modified region to a range below the crack-modified region. This limits the longitudinal growth length of the crack to a smaller height range, thereby improving the efficiency of crack extension and minimizing the longitudinal extension of the crack, thereby minimizing the amount of slice loss.That is, by subdividing the modified layer into a void modified layer 22 and a crack modified layer 23, the short pulse laser beam is then focused on the void modified layer 22 after passing through the second end face of the silicon carbide ingot 10, and the focus position of the short pulse laser beam is designed more accurately and reasonably, not only making the vertical height difference of the focus of the short pulse laser beam fluctuate less (because the vertical height difference of the void modified formation area must be smaller than the vertical height difference of the modified layer composed of the crack modified formation area and the void modified formation area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the void modified layer 22. The crack-modified region above the modified layer blocks the vertical upward growth of cracks within the void-modified region, limiting the length of the vertical crack growth to a smaller height range. This optimizes the focus of the short-pulse laser beam and reduces the amount and length of cracks in the modified layer extending longitudinally along the silicon carbide ingot 10. This allows more laser energy to be applied to the lateral outward growth of the cracks, increasing the number and length of lateral crack growth, enabling thinner silicon carbide wafers to be cut, while also reducing cutting loss. More silicon carbide wafers can be cut from the same silicon carbide ingot 10, reducing waste. The following describes each of the above steps in detail with reference to the accompanying figures.

[0044] First, refer to Figure 1 、 Figure 2 and Figure 3 After passing an ultrashort pulse laser beam through the first end face of the silicon carbide ingot 10 to be cut, it is focused on the set depth layer 21 of the silicon carbide ingot 10 to generate a cavity modification formation region and a crack modification formation region above the set depth layer 21, respectively; wherein the cavity modification formation region is located between the set depth layer 21 and the crack modification formation region. The intensity at the focal volume of the ultrashort pulse laser beam causes nonlinear absorption of laser energy by the material through multiphoton ionization, tunnel ionization, and avalanche ionization. Due to nonlinear absorption, a microscopic, highly excited plasma is generated at the focal position. The microscopic size of the laser will vary when acting on different crystal materials, ranging from nanometers to submicron sizes. Therefore, no large-scale material damage will occur in the direction of laser incidence.

[0045] The depth layer 21 set during the processing is specifically related to the thickness of the peeled wafer, peeling loss thickness, etc. The focus of the ultrashort pulse laser beam can be accurately focused on the set depth layer 21 position of the silicon carbide ingot 10 by a three-axis galvanometer, an altimeter, etc.

[0046] like Figures 2 to 4As shown in FIG, the crack modification forming area and the cavity modification forming area generated above the set depth layer 21 occupy a certain thickness space. The size of the crack modification forming area and the cavity modification forming area is related to the energy of the ultrashort pulse laser beam. The size of the crack modification forming area and the cavity modification forming area increases with the increase of laser energy. Figures 2 to 4 As shown, the cavity modification forming region can be located in the region 1-5um above the focus of the ultrashort pulse laser beam, and the crack modification forming region can be located in the region 10-30um above the cavity modification forming region, so that the cavity modification forming region and the crack modification forming region are in different depth layers, and the cavity modification layer 22 and the crack modification layer 23 can be clearly distinguished.

[0047] When selecting an ultrashort pulse laser beam, the ultrashort pulse laser beam can be a sub-picosecond pulse width laser beam, a picosecond pulse width laser beam, or a femtosecond pulse width laser beam, facilitating the generation of a more effective void modification and crack modification region above the focal point of the ultrashort pulse laser beam. For example, the pulse width of the ultrashort pulse laser beam can be any value between 243 fs and 900 fs, further enhancing the modification effect of the void modification and crack modification regions generated above the focal point of the ultrashort pulse laser beam. In a more preferred embodiment, the wavelength of the ultrashort pulse laser beam can be controlled to be between 500 and 1100 nm. Specifically, the wavelength of the ultrashort pulse laser beam can be any value between 500 and 1100 nm, such as 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or 1100 nm. This facilitates the generation of a more effective void modification and crack modification region above the focal point of the ultrashort pulse laser beam.

[0048] In addition, in a more preferred embodiment, the thickness of the silicon carbide ingot 10 to be cut can be no more than 5 mm, and the distance between the set depth layer 21 and the first end face and the second end face is set to be between 2 and 3 mm. As a result, when the ultrashort pulse laser beam is focused on the set depth layer 21, the transmission path length within the silicon carbide ingot 10 is between 2 and 3 mm; it is also possible that when the short pulse laser beam is focused on the cavity modification formation area through the second end face, the transmission path length within the silicon carbide ingot 10 is also between 2 and 3 mm. Taking into account the difficulty of focusing the short pulse laser beam on the cavity modification formation area after passing through the second end face of the silicon carbide ingot 10 and the energy dissipation, large energy dissipation is prevented. That is, when the thickness of the silicon carbide ingot 10 to be cut is greater than 5 mm, the thicker silicon carbide ingot 10 can be cut into multiple thinner silicon carbide ingots 10 by multiple cutting. Afterwards, the method described in this application is used to slice silicon carbide wafers that meet the requirements from the thinner silicon carbide ingot 10 .

[0049] Next, refer to Figure 1 and Figure 4 , controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide ingot 10, so as to form a cavity modification layer 22 and a crack modification layer 23 above the position of the set depth layer 21, respectively; wherein, the cavity modification layer 22 is composed of multiple cavity modification forming regions, the crack modification layer 23 is composed of multiple crack modification forming regions, and the cavity modification layer 22 is located between the set depth layer 21 and the crack modification layer 23.

[0050] The method for controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 of the silicon carbide ingot 10 can be implemented in a variety of ways to form a void modified layer 22 and a crack modified layer 23 within the silicon carbide ingot 10, respectively. The voids in the void modified layer 22 are modified to form a region-by-region gap covering the void modified layer 22, and the cracks in the crack modified layer 23 are modified to form a region-by-region gap covering the crack modified layer 23. For example, a spiral scanning method can be implemented, or a parallel scanning method can be implemented to form multiple cutting lanes. Exemplarily, the focus of the ultrashort pulse laser beam can be controlled to scan multiple parallel first cutting paths at a set depth layer 21 of the silicon carbide ingot 10, and the interval between any two adjacent first cutting paths can be 10-25um. Specifically, the interval between any two adjacent first cutting paths can be any value between 10-25um, such as 10um, 15um, 20um, 25um, etc. Considering that the size of the void modification forming area is smaller than the size of the crack modification forming area and the crack growth range is lower, the spacing between adjacent void modification forming areas is appropriately reduced, which simplifies the difficulty of subsequent cracks growing laterally and connecting together, facilitates setting the silicon carbide explosion point interval of appropriate width, improves slicing efficiency, and simplifies scanning difficulty.

[0051] Next, refer to Figure 1 、 Figure 5 and Figure 6After passing through the second end face of the silicon carbide ingot 10, the short-pulse laser beam is focused on the cavity-modifying region and scattered and propagated within the cavity-modifying region, causing cracks within the cavity-modifying region to grow laterally outward. The pulse width of the short-pulse laser beam is greater than that of the ultrashort-pulse laser beam, and the pulse width of the short-pulse laser beam does not reach the nanosecond pulse width, but rather is at a sub-nanosecond wavelength level on the picosecond scale. That is, the focus position of the short-pulse laser beam is shifted upward relative to the focal point of the ultrashort-pulse laser beam. Furthermore, the short-pulse laser beam is incident on the cavity-modifying region within the silicon carbide ingot 10 from the second end face, without having to pass through the crack-modifying region above the cavity-modifying region. This prevents cracks within the crack-modifying region from scattering the short-pulse laser beam, improves laser energy concentration, and thereby enhances heating efficiency and crack extension efficiency within the cavity-modifying region. By using a short pulse laser beam in the cavity modification forming area, the laser self-scattering of free ions after the laser passes through the crack modification area is utilized to realize the scattering characteristics of the focused focal spot of the laser in the cavity modification forming area, and the laser scatters and propagates in the cavity modification forming area, driving the crack growth in the cavity modification forming area.

[0052] In the early laser processing process, 10 -15 The laser energy with a pulse width of the order of s is absorbed inside the material. For different materials (conductors, semiconductors, insulators, etc.), its essence is that the laser introduces a non-equilibrium free electron distribution, and the energy is transferred through the interaction between electrons, lattices and phonons. Then the plasma is heated in sub-picoseconds (10 -9 s) range, accompanied by the inherent evaporation and melting process. The speed of energy transfer between the lattice and the material is related to the intrinsic properties of the material. As the laser energy continues to act, the material begins to change its phase at this stage. After that, shock radiation is generated. The time span of this process is relatively long (usually occurs in 10 -12 s to 10 -3 During the time between s and 10s, the thermal effects of the material gradually become dominant, generating a thermal front and an evaporation front, which in turn leads to a gradual increase in the reverse thrust, accompanied by a weaker secondary radiation process. The processing method described in this patent is based on the initial stage of the material's thermal effects, resulting in a cumulative thermal effect.

[0053] The aforementioned void-modified region is actually a modified region where voids have not yet formed. When a focused short-pulse laser beam that can penetrate the material is subsequently loaded, when the photon energy of the short-pulse laser beam is focused on the material and the photon energy is high enough, the laser photons may directly break the chemical bonds of the sample, causing the volume of the local area to rapidly expand and explode. A sufficiently long short pulse width allows the photon energy to be immediately coupled to the silicon carbide lattice after being transferred to electrons. The photon energy will be converted into heat energy, causing the sample temperature to rise. When the temperature rises, the physical and chemical properties of the sample further change, the optical system coefficients change, and stress is generated within the sample. As the pulse width increases, the stress continues to accumulate, breaking the chemical bonds in the void-modified region created by the previous ultrashort pulse laser beam. The cracks formed between the carbon and silicon elements are further guided to radiate outward.

[0054] It's important to explain that the longer pulse width of a short-pulse laser beam compared to an ultrashort-pulse laser beam is intended to increase the light dwell time, generating a greater thermal effect and thus extending the crack's growth. After multiple, continuous short-pulse laser irradiations—which can range from 1-3 to 3-5 times—the crack can grow horizontally to over 200 microns. Growth will vary depending on the material, type of material, doping, and laser parameters such as power, pulse width, and wavelength.

[0055] When selecting a short-pulse laser beam, the short-pulse laser beam can be a sub-nanosecond laser beam to increase the amount and length of lateral crack growth. For example, the pulse width of the short-pulse laser beam can be any value greater than 50ns, which is convenient for better reducing the amount and length of cracks in the modified layer that extend longitudinally along the silicon carbide ingot 10, thereby directing more laser energy to the lateral outward growth of the cracks, increasing the amount of lateral crack growth and the length of crack growth. In a more preferred embodiment, the wavelength of the short-pulse laser beam can be 500-1100nm. Specifically, the wavelength of the short-pulse laser beam can be any value between 500-1100nm, such as 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, etc. This is convenient for better reducing the amount and length of cracks in the modified layer that extend longitudinally along the silicon carbide ingot 10, thereby directing more laser energy to the lateral outward growth of the cracks, increasing the amount of lateral crack growth and the length of crack growth.

[0056] When focusing the short-pulse laser beam on the void-modification formation region, a more optimal approach is to focus the short-pulse laser beam at a position 1-4.5 μm higher than the ultrashort-pulse laser beam's focus, thereby further optimizing the short-pulse laser beam's focus position. Of course, any approach that focuses the short-pulse laser beam on the void-modification formation region is within the scope of protection of this patent.

[0057] In addition, the polarization state of the short-pulse laser beam can be simultaneously controlled to control the diffusion direction of the explosion energy in the void-modified region, and crack growth at a certain angle at the explosion point of the short-pulse laser beam can be achieved. During the process of focusing the short-pulse laser beam through the second end face of the silicon carbide ingot 10 on the void-modified region and scattering and propagating in the void-modified region, causing cracks in the void-modified region to grow laterally outward, the polarization state of the short-pulse laser beam can be adjusted so that the electron propagation direction extends along the silicon carbide lattice direction of the silicon carbide ingot 10, forming a 3-5° lateral growth crack. This can further reduce the amount and length of cracks in the modified layer that extend longitudinally along the silicon carbide ingot 10, thereby directing more laser energy to the lateral outward growth of the cracks, increasing the number and length of lateral crack growth. For example, the polarization state of the short-pulse laser beam can be adjusted so that the growth direction of the lateral growth crack has an angle of 3-5° relative to the cutting path direction.

[0058] Next, refer to Figure 1 、 Figure 5 and Figure 6 , after controlling the short pulse laser beam to pass through the second end face, it is focused on the void modification layer 22 and scanned at the set depth layer 21, so that the cracks in any adjacent void modification forming areas in the void modification layer 22 are connected together by lateral growth. The specific method of controlling the focus of the short pulse laser beam to scan the void modification layer 22 is related to the method of controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21. For example, when the method of controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 adopts a spiral scanning method, the method of controlling the focus of the short pulse laser beam to scan the void modification layer 22 is also a spiral scanning method. When the method of controlling the focus of the ultrashort pulse laser beam to scan the set depth layer 21 adopts a method of multiple parallel first cutting paths, the method of controlling the focus of the second short pulse laser beam to scan the void modification layer 22 can be specifically: controlling the focus of the short pulse laser beam to scan multiple parallel second cutting paths in the void modification layer 22, and each second cutting path is located directly above a first cutting path, thereby simplifying the scanning difficulty.

[0059] In addition, when controlling the focus of the short pulse laser beam to scan multiple parallel second cutting paths in the void modification layer 22, the focus of the short pulse laser beam can be controlled to scan at each second cutting path for more than or equal to three times. By using the short pulse laser beam for multiple processing and continuous heat injection, the explosion point crack connection is achieved, the amount and length of the lateral growth of the crack in the crack modification formation area are increased, and the cracks extending from adjacent second cutting paths are connected together faster, which facilitates the realization of the implicit crack induced growth method to achieve the purpose of separating the silicon carbide ingot 10 into multiple silicon carbide wafers.

[0060] Next, refer to Figure 1 The silicon carbide ingot 10 is partially peeled off with the void modified layer 22 as the interface to generate a silicon carbide wafer. Specifically, the silicon carbide wafer can be peeled off with the void modified layer 22 as the interface by stretching, rotating, or other methods to peel the wafer above the void modified layer 22 from the silicon carbide ingot 10.

[0061] In addition, the following method can also be used to peel off a portion of the silicon carbide ingot 10 with the cavity modified layer 22 as the interface to generate a wafer. A diamond wire saw is used to perform wire cutting on the cavity modified layer, and a portion of the silicon carbide ingot is peeled off with the cavity modified layer as the interface to generate a silicon carbide wafer. By first focusing the laser beam at a predetermined depth layer from the inside of the silicon carbide ingot and scanning, a cavity modified layer is formed at the predetermined depth layer position. In the process of forming the cavity modified layer, the energy density at the laser focus exceeds the silicon carbide ablation threshold, the material temperature rises suddenly, and the silicon carbide decomposes under high temperature conditions to generate amorphous silicon or single crystal silicon or a mixture of the two and carbon. The specific amorphous silicon and single crystal silicon are determined by the laser energy density. When the laser energy is large, single crystal silicon is generated, and when the laser energy is small, amorphous silicon is generated. Thereafter, a diamond wire saw is used to perform wire cutting on the cavity modified layer, and a portion of the silicon carbide ingot is peeled off with the cavity modified layer as the interface to generate a silicon carbide wafer. Since the materials of the void modification layer are single crystal silicon, amorphous silicon and carbon, their hardness is much lower than that of silicon carbide. In the process of wire cutting the void modification layer with a diamond wire saw, the wear of the diamond wire saw can be reduced, thereby reducing the loss of the diamond wire saw and reducing the difficulty of wire cutting. Therefore, a thinner diamond wire saw can be selected to reduce the loss of silicon carbide ingots and improve the slicing output rate of silicon carbide ingots. At the same time, the diamond wire saw cutting method is not easy to cause the silicon carbide wafer to break due to uneven force. That is, compared with the laser cutting + mechanical stripping method, the present application uses a diamond wire saw to cut the void modification layer and peel off the silicon carbide wafer from the modified silicon carbide ingot without the need for mechanical stripping. This can avoid the phenomenon that the silicon carbide wafer may break due to uneven force during the mechanical stripping process, thereby improving the product yield and stripping efficiency.

[0062] After the silicon carbide wafer is stripped from the silicon carbide ingot and before it is ground, a step can be added in which the silicon carbide wafer is immersed in a chemical solution to etch the interface of the modified layer of the silicon carbide wafer. By using the chemical solution to etch the interface of the modified layer of the silicon carbide wafer, defects such as residual stress, dislocations, and cracks generated during the silicon carbide wafer stripping step can be removed. The interface of the modified layer of the silicon carbide wafer is then ground. Since there is no or little residual stress on the interface of the modified layer of the silicon carbide wafer at this time, the increase in defects during the grinding process is avoided. The phenomenon that the extrusion during the grinding process increases residual stress and thus causes continued crack growth can be slowed down. As a result, less material can be ground to completely remove the damaged layer, reducing ingot loss and improving wafer quality. In addition, the interface of the modified layer after chemical solution etching is more flat, which can reduce the difficulty of subsequent grinding and improve grinding efficiency.

[0063] In the various embodiments shown above, an ultrashort pulse laser is first used. After the ultrashort pulse laser beam passes through the first end face of the silicon carbide ingot 10, it is focused on the set depth layer 21 position of the silicon carbide ingot 10 to generate a cavity modification forming region and a crack modification forming region above the set depth layer 21 position, respectively, and the focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10 to form a cavity modification layer 22 and a crack modification layer 23. After ultrashort pulse laser stealth cutting processing, a short pulse laser with a slightly wider pulse width is used to focus the short pulse laser beam on the cavity modification forming area after passing through the second end face of the silicon carbide ingot 10, and scatter and propagate in the cavity modification forming area, so that the heat of the short pulse laser beam mainly acts on the cavity modification forming area, causing the cracks in the crack modification forming area to grow laterally outward, and the focus of the short pulse laser beam is controlled to scan the cavity modification layer 22, so that the cracks in any adjacent cavity modification forming areas in the cavity modification layer 22 are connected together through lateral growth.

[0064] Compared to existing laser cutting processes for silicon ingots, the ultrashort pulse laser used in this method can, after penetrating the first end face of the silicon carbide ingot 10, generate a void-modified region and a crack-modified region above a predetermined depth layer 21 at the focus of the ultrashort pulse laser beam. Scanning then forms a void-modified layer 22 and a crack-modified layer 23, respectively, thus refining and differentiating the modified layers in the prior art. Subsequently, when a short pulse laser beam is used, the short pulse laser beam is focused on the void-modified region after penetrating the second end face of the silicon carbide ingot 10. The focus of the short pulse laser beam is above the focus of the ultrashort pulse laser beam, rather than at the same depth as in the prior art. This allows the laser to scatter and propagate within the void-modified region, causing cracks within the void-modified region to grow laterally outward. Furthermore, scanning allows cracks within any adjacent void-modified regions in the void-modified layer 22 to connect through lateral growth. Since the short-pulse laser beam is incident on the cavity-modified region of the silicon carbide ingot 10 through the second end face, it does not need to pass through the crack-modified region above the cavity-modified region. This prevents the cracks in the crack-modified region from scattering the short-pulse laser beam, improves the laser energy concentration, and thus improves the heating efficiency and crack extension efficiency of the cavity-modified region. Moreover, during the process of focusing the short-pulse laser beam on the cavity-modified region and heating the cavity-modified region, the crack-modified region can block the growth of cracks, thereby limiting the upward growth length of cracks in the cavity-modified region to a range below the crack-modified region. This limits the longitudinal growth length of the crack to a smaller height range, thereby improving the efficiency of crack extension and minimizing the longitudinal extension of the crack, thereby minimizing the amount of slice loss.That is, by subdividing the modified layer into a void modified layer 22 and a crack modified layer 23, the short pulse laser beam is then focused on the void modified layer 22 after passing through the second end face of the silicon carbide ingot 10, and the focus position of the short pulse laser beam is designed more accurately and reasonably, not only making the vertical height difference of the focus of the short pulse laser beam fluctuate less (because the vertical height difference of the void modified formation area must be smaller than the vertical height difference of the modified layer composed of the crack modified formation area and the void modified formation area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the void modified layer 22. The crack modification forming area thereon blocks the vertical upward growth of cracks in the void modification forming area, limits the length of the vertical growth of the cracks to a smaller height range, optimizes the focusing position of the short pulse laser beam, reduces the amount and length of the cracks in the modified layer extending longitudinally along the silicon carbide ingot 10, and thus applies more laser energy to the lateral outward growth of the cracks, thereby increasing the number and length of lateral crack growth, and being able to cut thinner silicon carbide wafers, while also reducing the cutting loss thickness. More silicon carbide wafers can be cut from the same silicon carbide ingot 10, reducing waste.

[0065] In addition, an embodiment of the present invention further provides a device for laser stripping of a silicon carbide ingot, wherein the silicon carbide ingot 10 to be cut has a first end face and a second end face relative to each other. The device for laser stripping of a silicon carbide ingot comprises: a stage, an ultrashort pulse laser system, a first scanning system, a short pulse laser system, a second scanning system and a stripping system. The stage is used to fix the silicon carbide ingot 10 to be cut. The ultrashort pulse laser system is used to focus the ultrashort pulse laser beam on the set depth layer 21 position of the silicon carbide ingot 10 after passing it through the first end face of the silicon carbide ingot 10 to be cut, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer 21 position, respectively; wherein the cavity modification forming region is located between the set depth layer 21 position and the crack modification forming region. The first scanning system is used to control the ultrashort pulse laser beam to pass through the first end face, focus on a set depth layer 21 of the silicon carbide ingot 10, and scan the set depth layer 21 to form a void modification layer 22 and a crack modification layer 23 above the set depth layer 21, respectively. The void modification layer 22 is composed of multiple void modification formation regions, and the crack modification layer 23 is composed of multiple crack modification formation regions, with the void modification layer 22 located between the set depth layer 21 and the crack modification layer 23. The short pulse laser system is used to control the short pulse laser beam to pass through the second end face of the silicon carbide ingot 10, focus on the void modification formation region, and scatter and propagate in the void modification formation region, causing cracks in the void modification formation region to grow laterally outward. The second scanning system is used to control the short pulse laser beam to pass through the second end face, focus on the void modification layer 22, and scan the set depth layer 21, so that cracks in any adjacent void modification formation regions in the void modification layer 22 are connected by lateral growth. The stripping system is used to strip a portion of the silicon carbide ingot 10 using the void modified layer 22 as an interface to generate a silicon carbide wafer.

[0066] like Figure 7 and Figure 9 The different types of devices for laser stripping of silicon carbide ingots shown, the first scanning system and the second scanning system can be realized by a three-axis motion table, and the stage is fixed on the three-axis motion table. The ultrashort pulse laser system and the short pulse laser system can use different lasers respectively. Among them, the parameter setting method of the ultrashort pulse laser beam provided by the above-mentioned ultrashort pulse laser system can refer to the description of the relevant part of the aforementioned method for laser stripping of silicon carbide ingots, and will not be repeated here. The parameter setting method of the short pulse laser beam provided by the above-mentioned short pulse laser system can refer to the description of the relevant part of the aforementioned method for laser stripping of silicon carbide ingots, and will not be repeated here. Reference Figure 8 , CCD cameras and light sources can also be set on different laser systems to observe the processing position in real time.

[0067] refer to Figure 7, the ultrashort pulse laser system and the short pulse laser system can both be set above the stage. Figure 7 As shown, at this time, the device for laser stripping of the silicon carbide ingot may further include: a clamping and flipping mechanism, which is used to clamp and flip the silicon carbide ingot 10 held on the stage so that the first end face or the second end face of the silicon carbide ingot 10 faces upward. When both the ultrashort pulse laser system and the short pulse laser system are arranged above the stage, a clamping and flipping mechanism may be additionally provided. After the ultrashort pulse laser beam emitted by the ultrashort pulse laser system passes through the first end face of the silicon carbide ingot 10 and generates a crack modified layer 23 and a void modified layer 22 in the silicon carbide ingot 10, the silicon carbide ingot 10 is flipped by the clamping and flipping mechanism so that the second end face of the silicon carbide ingot 10 faces upward. Afterwards, the short pulse laser system adopts a galvanometer focusing method, and uses a telecentric flat field lens with a long focal depth as a focusing lens. The lens with a long focal depth can make a large amount of energy act on the position of the cavity modification and formation area with a larger focus, that is, by making the short pulse laser beam emitted by the short pulse laser system pass through the second end face of the silicon carbide ingot 10 and focus on the cavity modification and formation area, so that more thermal effects are generated at this position, the crack grows longer, and the crack expands and extends. After multiple continuous irradiation of short pulse laser, which can be 3 to 5 times here, the crack can grow more than 200 microns in the horizontal direction. The growth will be different depending on the material, material type, doping injection situation, different laser parameters, power pulse width, wavelength, etc. In the above manner, the efficiency of automated operation can be improved. Figure 8 Based on Figure 7 The laser slicing operation flow chart of the device for laser stripping silicon carbide ingot is shown. Figure 8 The operation flow shown can complete all the operation steps of any of the laser slicing methods shown above.

[0068] At this time, the focal position of the ultrashort pulse laser beam and the focal position of the short pulse laser beam can be determined as follows. Based on the actual processing position H and the law of refraction, when the laser head NA = 0.42, the incident angle of the laser when passing through the laser head is:

[0069] U1=sin(0.42)*180 / π=24.83°

[0070] The laser is refracted when passing through the sample surface, and its refraction angle is:

[0071] U2=sin(0.42 / 2.6)*180 / π=9.3°

[0072] Therefore, the magnification of the distance of the laser in the medium is:

[0073] A=tan(π*24.83 / 180) / tan(π*9.3 / 180)=2.83

[0074] So when the laser is focused on a certain position H inside the sample, the distance the laser head moves along the Z axis is:

[0075] L=H / 2.83

[0076] refer to Figure 9 and Figure 10 The stage can fix the silicon carbide ingot 10 by clamping the side wall of the silicon carbide ingot 10 to be cut, so that the first end face and the second end face of the silicon carbide ingot 10 are not blocked. Figure 9 and Figure 10 As shown, the ultrashort pulse laser system and the short pulse laser system can be respectively arranged above and below the stage. At this time, the stage is fixed by clamping the side wall of the silicon carbide ingot 10, so that the first end face and the second end face of the silicon carbide ingot 10 are not blocked by the stage. Furthermore, the ultrashort pulse laser system can be arranged on the side of the first end face of the silicon carbide ingot 10, so that the ultrashort pulse laser beam it emits passes through the first end face to process the inside of the silicon carbide ingot 10. The short pulse laser system can be arranged on the side of the second end face of the silicon carbide ingot 10, so that the short pulse laser beam it emits passes through the second end face to process the inside of the silicon carbide ingot 10 without flipping the silicon carbide ingot 10. When specifically set up, as Figure 9 and Figure 10 As shown, the ultrashort pulse laser system can be arranged above the stage, and the short pulse laser system can be arranged below the stage. Of course, the ultrashort pulse laser system can also be arranged below the stage, and the short pulse laser system can be arranged above the stage.

[0077] When implementing it specifically, Figure 9 and Figure 10 As shown, a through hole can be opened under the stage. After the ultrashort pulse laser beam is processed along the cutting path, another short pulse laser beam will be delayed by one position and quickly triggered according to the position trigger mode. Each point will emit 3-5 pulses to act on the cavity modification formation area formed after the previous ultrashort pulse processing for crack expansion. This method can save more processing time. The processing positions of the two laser beams, Z1 axis and Z2 axis, are processed as a whole and can move at the same time. The position of the two axes is mainly to ensure that the ultrashort pulse laser and the short pulse laser are focused on the position below (1-3um) and above (3-5um) the set target silicon carbide wafer height respectively. This method can quickly process the ingot to achieve the growth connection of the cracks inside the ingot.

[0078] In the various embodiments shown above, an ultrashort pulse laser is first used. After the ultrashort pulse laser beam passes through the first end face of the silicon carbide ingot 10, it is focused on the set depth layer 21 position of the silicon carbide ingot 10 to generate a cavity modification forming region and a crack modification forming region above the set depth layer 21 position, respectively, and the focus of the ultrashort pulse laser beam is controlled to scan the set depth layer 21 of the silicon carbide ingot 10 to form a cavity modification layer 22 and a crack modification layer 23. After ultrashort pulse laser stealth cutting processing, a short pulse laser with a slightly wider pulse width is used to focus the short pulse laser beam on the cavity modification forming area after passing through the second end face of the silicon carbide ingot 10, and scatter and propagate in the cavity modification forming area, so that the heat of the short pulse laser beam mainly acts on the cavity modification forming area, causing the cracks in the crack modification forming area to grow laterally outward, and the focus of the short pulse laser beam is controlled to scan the cavity modification layer 22, so that the cracks in any adjacent cavity modification forming areas in the cavity modification layer 22 are connected together through lateral growth.

[0079] Compared to existing laser cutting processes for silicon ingots, the ultrashort pulse laser used in this method can, after penetrating the first end face of the silicon carbide ingot 10, generate a void-modified region and a crack-modified region above a predetermined depth layer 21 at the focus of the ultrashort pulse laser beam. Scanning then forms a void-modified layer 22 and a crack-modified layer 23, respectively, thus refining and differentiating the modified layers in the prior art. Subsequently, when a short pulse laser beam is used, the short pulse laser beam is focused on the void-modified region after penetrating the second end face of the silicon carbide ingot 10. The focus of the short pulse laser beam is above the focus of the ultrashort pulse laser beam, rather than at the same depth as in the prior art. This allows the laser to scatter and propagate within the void-modified region, causing cracks within the void-modified region to grow laterally outward. Furthermore, scanning allows cracks within any adjacent void-modified regions in the void-modified layer 22 to connect through lateral growth. Since the short-pulse laser beam is incident on the cavity-modified region of the silicon carbide ingot 10 through the second end face, it does not need to pass through the crack-modified region above the cavity-modified region. This prevents the cracks in the crack-modified region from scattering the short-pulse laser beam, improves the laser energy concentration, and thus improves the heating efficiency and crack extension efficiency of the cavity-modified region. Moreover, during the process of focusing the short-pulse laser beam on the cavity-modified region and heating the cavity-modified region, the crack-modified region can block the growth of cracks, thereby limiting the upward growth length of cracks in the cavity-modified region to a range below the crack-modified region. This limits the longitudinal growth length of the crack to a smaller height range, thereby improving the efficiency of crack extension and minimizing the longitudinal extension of the crack, thereby minimizing the amount of slice loss.That is, by subdividing the modified layer into a void modified layer 22 and a crack modified layer 23, the short pulse laser beam is then focused on the void modified layer 22 after passing through the second end face of the silicon carbide ingot 10, and the focus position of the short pulse laser beam is designed more accurately and reasonably, not only making the vertical height difference of the focus of the short pulse laser beam fluctuate less (because the vertical height difference of the void modified formation area must be smaller than the vertical height difference of the modified layer composed of the crack modified formation area and the void modified formation area), but also optimizing the focus of the short pulse laser beam on the modified layer to focus on the void modified layer 22. The crack modification forming area thereon blocks the vertical upward growth of cracks in the void modification forming area, limits the length of the vertical growth of the cracks to a smaller height range, optimizes the focusing position of the short pulse laser beam, reduces the amount and length of the cracks in the modified layer extending longitudinally along the silicon carbide ingot 10, and thus applies more laser energy to the lateral outward growth of the cracks, thereby increasing the number and length of lateral crack growth, and being able to cut thinner silicon carbide wafers, while also reducing the cutting loss thickness. More silicon carbide wafers can be cut from the same silicon carbide ingot 10, reducing waste.

[0080] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for laser stripping a silicon carbide ingot, wherein the silicon carbide ingot to be cut has a first end face and a second end face opposite to each other, characterized in that: The method comprises: After passing an ultrashort pulse laser beam through the first end face, the ultrashort pulse laser beam is focused at a set depth layer position of the silicon carbide ingot to be cut, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position, respectively; wherein the cavity modification forming region is located between the set depth layer position and the crack modification forming region; After controlling the ultrashort pulse laser beam to pass through the first end face, the ultrashort pulse laser beam is focused on a set depth layer of the silicon carbide ingot and scanned at the set depth layer to form a void modification layer and a crack modification layer above the position of the set depth layer, respectively; wherein the void modification layer is composed of a plurality of the void modification forming regions, the crack modification layer is composed of a plurality of the crack modification forming regions, and the void modification layer is located between the set depth layer and the crack modification layer; After passing through the second end face, the short pulse laser beam is focused on the cavity modification forming region and scattered and propagated in the cavity modification forming region, so that cracks in the cavity modification forming region grow outward in a transverse direction and the crack modification forming region blocks the vertical upward growth of cracks in the cavity modification forming region; After controlling the short pulse laser beam to pass through the second end face, the short pulse laser beam is focused on the void modified layer and scanned at the set depth layer, so that cracks in any adjacent void modified regions in the void modified layer are connected together by lateral growth; A portion of the silicon carbide ingot is peeled off with the cavity reformed layer as an interface to generate a silicon carbide wafer.

2. The method according to claim 1, wherein The thickness of the silicon carbide ingot to be cut is not greater than 5 mm, and the distances between the set depth layer and the first end face and the second end face are both between 2 and 3 mm.

3. The method according to claim 1, wherein The pulse width of the short pulse laser beam is greater than 50 ns, and the wavelength of the short pulse laser beam is 500-1100 nm.

4. The method according to claim 1, wherein The pulse width of the ultrashort pulse laser beam is 243fs-900fs, and the wavelength of the ultrashort pulse laser beam is 500-1100nm.

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

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

7. The method according to claim 6, wherein The controlling the focus of the short pulse laser beam to scan a plurality of parallel second cutting paths in the cavity modified layer comprises: The focus of the short pulse laser beam is controlled to scan at each second cutting street for a number of times greater than or equal to three times.

8. A device for laser stripping a silicon carbide ingot, wherein the silicon carbide ingot to be cut has a first end face and a second end face opposite to each other, characterized in that: The device comprises: A stage for fixing the silicon carbide ingot to be cut; an ultrashort pulse laser system, configured to focus an ultrashort pulse laser beam through the first end face and then focus the beam at a set depth layer position of the silicon carbide ingot to be cut, so as to generate a cavity modification forming region and a crack modification forming region above the set depth layer position, respectively; wherein the cavity modification forming region is located between the set depth layer position and the crack modification forming region; a first scanning system, configured to control the ultrashort pulse laser beam to focus on a set depth layer of the silicon carbide ingot after passing through the first end face and scan the set depth layer, so as to form a void modified layer and a crack modified layer above the position of the set depth layer, respectively; wherein the void modified layer is composed of a plurality of the void modified forming regions, the crack modified layer is composed of a plurality of the crack modified forming regions, and the void modified layer is located between the set depth layer and the crack modified layer; a short pulse laser system, configured to focus a short pulse laser beam on the cavity modification forming region after passing through the second end face, and scatter and propagate the short pulse laser beam in the cavity modification forming region, thereby causing cracks in the cavity modification forming region to grow laterally outward; a second scanning system for controlling the short pulse laser beam to focus on the void modified layer after passing through the second end surface and to scan at the set depth layer, so that cracks in any adjacent void modified areas in the void modified layer are connected together by lateral growth; The stripping system is used to strip a portion of the silicon carbide ingot using the cavity modified layer as an interface to generate a silicon carbide wafer.

9. The device according to claim 8, wherein The ultrashort pulse laser system and the short pulse laser system are both arranged above the stage; The device further includes a clamping and flipping mechanism, which is used to clamp and flip the silicon carbide ingot held on the stage so that the first end face or the second end face of the silicon carbide ingot faces upward.

10. The device according to claim 8, wherein The stage fixes the silicon carbide ingot by clamping the sidewall of the silicon carbide ingot to be cut, so that the first end surface and the second end surface of the silicon carbide ingot are not blocked; The ultrashort pulse laser system and the short pulse laser system are respectively arranged above and below the object stage.

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