Laser processing device, silicon carbide ingot cutting method, and laser processing system

Abstract

The invention discloses a laser processing device, a silicon carbide crystal ingot cutting method and a laser processing system. The laser processing device comprises a laser used for emitting Gaussian beams with preset laser parameters; the beam shaping element is used for shaping the Gaussian beam into a linear beam; and the scanning mechanism is used for focusing the linear light beam and cutting the silicon carbide crystal ingot by utilizing the focused linear light beam according to a preset cutting path and a preset cutting speed. Compared with the focused Gaussian beam, the focused linear beam has a small spot size in the direction of the optical axis, which means that the action depth of the focused linear beam in the silicon carbide crystal ingot is shallower, so that the length of the growth area of the microcracks generated in the direction of the optical axis in the machining process is reduced, and the machining precision is improved. And therefore, the roughness generated on the surface of the silicon carbide wafer is reduced, and the quality of the silicon carbide wafer is improved.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to a laser processing device, a method for cutting a silicon carbide ingot, and a laser processing system. Background Art

[0002] With the rapid development of the global semiconductor industry, silicon carbide (SiC) has become a key material for manufacturing high-performance electronic devices due to its excellent physical and chemical properties. The production cost of silicon carbide is very high. In order to reduce the cost, a large silicon carbide ingot needs to be cut into as many thin silicon carbide wafers as possible. However, silicon carbide is extremely hard and brittle, making it very difficult to cut.

[0003] At present, laser cutting technology is usually used to cut silicon carbide ingots (also known as slicing). In the process of cutting silicon carbide ingots using laser cutting technology, although laser cutting technology has many advantages, it will inevitably produce a certain degree of roughness on the surface of the silicon carbide wafer, thereby reducing the quality of the silicon carbide wafer. Summary of the invention

[0004] In view of this, the present application provides a laser processing device, a method for cutting a silicon carbide ingot, and a laser processing system, which can reduce the roughness generated on the surface of the silicon carbide wafer, thereby improving the quality of the silicon carbide wafer.

[0005] In a first aspect, an embodiment of the present application provides a laser processing device, comprising: a laser for emitting a Gaussian beam having preset laser parameters; a beam shaping element for shaping the Gaussian beam into a linear beam; a scanning mechanism for focusing the linear beam, and using the focused linear beam to cut a silicon carbide ingot at a preset cutting path and a preset cutting speed, wherein the focused linear beam has a smaller spot size along the optical axis than the focused Gaussian beam.

[0006] In some embodiments, compared with a focused Gaussian beam, the focused linear beam has a larger spot size in a first direction perpendicular to a preset cutting path, and the direction of the optical axis is perpendicular to the first direction.

[0007] In some embodiments, the beam shaping element comprises a diffractive optical element or a spatial light modulator.

[0008] In some embodiments, the laser processing device also includes: a controller for controlling the laser to emit a Gaussian beam with preset laser parameters, and controlling a scanning mechanism so that the focused linear beam cuts the silicon carbide ingot at a preset cutting path and a preset cutting speed.

[0009] In some embodiments, the laser processing device also includes: a controller, a scanning mechanism including a focusing optical element and a three-axis translation stage for carrying a silicon carbide ingot, the focusing optical element is used to focus the linear light beam to obtain a focused linear light beam, and the controller controls the movement of the three-axis translation stage to make the focused linear light beam move on the silicon carbide ingot at a preset cutting path and a preset cutting speed.

[0010] In some embodiments, the laser processing device also includes: a controller, the scanning mechanism includes a focusing optical element and a galvanometer group, the focusing optical element is used to focus the linear light beam to obtain a focused linear light beam, and the controller controls the deflection angle of the galvanometer group to make the focused linear light beam move on the silicon carbide ingot at a preset cutting path and a preset cutting speed.

[0011] In some embodiments, the preset cutting speed is 15 mm / s to 50 mm / s, and the spacing between adjacent laser processing lines in the preset cutting path is 20 μm to 50 μm.

[0012] In some embodiments, the laser comprises a femtosecond laser, and the preset laser parameters comprise: a pulse width of 190 fs to 350 fs, a repetition frequency of 50 KHz to 500 KHz, and an average power of 0.75 W to 1.5 W.

[0013] In a second aspect, a method for cutting a silicon carbide ingot is provided, which includes: controlling a laser processing device to output a focused linear beam with preset laser parameters; controlling the focused linear beam to move on the silicon carbide ingot at a preset cutting path and a preset cutting speed, and modifying the interior of the silicon carbide ingot to complete the cutting of the silicon carbide ingot, wherein the focused linear beam has a small spot size along the direction of the optical axis compared to a focused Gaussian beam.

[0014] In some embodiments, compared with a focused Gaussian beam, the focused linear beam has a larger spot size in a first direction perpendicular to a preset cutting path, and the direction of the optical axis is perpendicular to the first direction.

[0015] In some embodiments, the spacing between adjacent laser processing lines in a preset cutting path is 20 μm to 50 μm, the preset cutting speed is 15 mm / s to 50 mm / s, and the preset laser parameters include a pulse width of 190 fs to 350 fs, a repetition frequency of 50 KHz to 500 KHz, and an average power of 0.75 W to 1.5 W.

[0016] In a third aspect, a laser processing system is provided, comprising: a memory and a processor, wherein the memory stores executable code, and the processor is configured to execute the executable code to implement the method for cutting a silicon carbide ingot as described in any embodiment of the second aspect.

[0017] In the laser processing scheme provided in the present application, a focused linear beam is used to cut a silicon carbide ingot with a preset cutting path and a preset cutting speed. Compared with a focused Gaussian beam, the spot size of the focused linear beam along the optical axis is smaller, which means that the focused linear beam has a shallower effective depth inside the silicon carbide ingot, thereby reducing the length of the growth area of ​​microcracks generated along the optical axis during the processing, thereby reducing the roughness generated on the surface of the silicon carbide wafer, thereby improving the quality of the silicon carbide wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a laser processing device provided in one embodiment of the present application.

[0019] Figure 2 It is a schematic structural diagram of a laser processing device provided in another embodiment of the present application.

[0020] Figure 3 It is a schematic diagram of the structure of a diffractive optical element provided in one embodiment of the present application.

[0021] Figure 4 It is a schematic diagram of the light field distribution of a linear light beam in the XY plane provided by an embodiment of the present application.

[0022] Figure 5 It is a schematic diagram of the light field distribution of a Gaussian beam in the XY plane provided by an embodiment of the present application.

[0023] Figure 6 It is a schematic diagram of the light spots of a Gaussian beam and a linear beam in the XY plane of a silicon carbide ingot provided in an embodiment of the present application.

[0024] Figure 7 It is a schematic diagram of the light spots of a Gaussian beam and a linear beam in the YZ plane of a silicon carbide ingot provided in an embodiment of the present application.

[0025] Figure 8 It is a schematic diagram of a cutting path of a linear light beam on the XY plane of a silicon carbide ingot provided in an embodiment of the present application.

[0026] Fig. 9 This is a confocal microscope morphology profile diagram of the surface roughness of a silicon carbide wafer provided in one embodiment of the present application.

[0027] Fig.10 This is a confocal microscope image of a silicon carbide wafer provided in an embodiment of the present application.

[0028] Fig.11 It is a schematic flow chart of a method for cutting a silicon carbide ingot provided in one embodiment of the present application.

[0029] Fig.12 It is a schematic diagram of the structure of a silicon carbide ingot cutting system provided in one embodiment of the present application.

[0030] Fig.13 is a block diagram of a laser processing system provided in one embodiment of the present application. DETAILED DESCRIPTION

[0031] The exemplary embodiments will be described in detail below, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are only examples of devices and methods consistent with some aspects of the present application as detailed in the attached claims.

[0032] The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms, unless otherwise clearly indicated below.

[0033] At present, there are still some technical difficulties in the laser cutting technology of silicon carbide ingots that have not been completely overcome. For example, the range of laser-induced microcracks is too large or the thickness of the chemical decomposition layer of silicon carbide under the action of laser is difficult to control. This will cause a certain degree of roughness on the surface of the silicon carbide wafer, thereby reducing the quality of the silicon carbide wafer.

[0034] However, it should be noted that the present application is not limited to the cutting of silicon carbide ingots, but is also applicable to the cutting of other brittle and hard inorganic non-metallic materials or semiconductor materials, such as glass and silicon wafers. These materials will encounter similar problems as the cutting of silicon carbide ingots during the cutting process, such as the large range of laser-induced microcracks or the difficulty in controlling the thickness of the chemical decomposition layer of silicon carbide under the action of laser. Therefore, the solution proposed in this application has a wide range of applicability and can provide technical support for the precision cutting of a variety of hard and brittle materials.

[0035] For ease of understanding, the generation of microcracks and the generation of chemical decomposition layers will be briefly introduced below.

[0036] The laser is focused inside the silicon carbide. Due to the accumulation of heat, a gradient heat-affected zone is formed inside the silicon carbide. The thermal stress on the silicon carbide in the heat-affected zone is different. Therefore, microcracks are formed due to uneven force.

[0037] Chemical decomposition layers usually refer to chemical changes in silicon carbide under laser irradiation, resulting in the decomposition of the material into new phases of its constituent elements or compounds. For example, laser-induced phase separation can cause silicon carbide to decompose into amorphous silicon and amorphous carbon, or even further transform into multilayer graphene. The formation of such decomposition layers usually involves the interaction of the laser with the material, such as a high-power laser beam focused on the surface of the material, resulting in rapid heating and phase change in the local area.

[0038] The formation of a chemically decomposed layer may also be accompanied by the generation of microcracks, which can form within the material, affecting its integrity and mechanical properties.

[0039] Research has found that the laser spot shape and laser heat diffusion may cause microcracks to spread around, resulting in a certain degree of roughness on the surface of the silicon carbide wafer, which in turn affects the quality of the silicon carbide wafer. Therefore, in order to prevent the microcracks from spreading around, the generation of microcracks should be concentrated on the laser scanning path (i.e., the cutting path described below) as much as possible. However, faced with a variety of spot shapes and laser parameter choices, which spot shape beam and which laser parameter laser to use for cutting silicon carbide ingots has become a key factor in determining the cutting effect.

[0040] After a series of further experimental explorations and theoretical studies, it was found that the use of a linear beam to cut silicon carbide ingots can effectively control the growth of microcracks and accurately control the thickness of the chemical decomposition layer under the action of the laser. This is due to the spot size of the focused linear beam along different axial directions. For example, the focused linear beam has a small spot size (also known as focal depth) along the direction of the optical axis, thereby reducing the length of the growth area of ​​the microcracks generated along the direction of the optical axis during the processing. For another example, the focused linear beam has a large spot size in the direction perpendicular to the cutting path, that is, the spacing between adjacent laser processing lines in the cutting path is increased, thereby reducing the influence of thermal stress and thermal shock waves during multi-pulse deposition. Therefore, the growth area of ​​the microcracks is better controlled, and the thickness of the chemical decomposition layer under the action of the laser is also effectively controlled.

[0041] Combine the following Figure 1 and 2 , the laser processing device provided in the embodiment of the present application is illustrated in more detail.

[0042] like Figure 1 and 2As shown, the laser processing device includes a laser 110, a beam shaping element 170 and a scanning mechanism arranged in sequence on an optical path. The laser 110 is used to emit a Gaussian beam with preset laser parameters, the beam shaping element 170 is used to shape the Gaussian beam emitted by the laser 110 into a linear beam, and the scanning mechanism is used to focus the linear beam, and use the focused linear beam to cut the silicon carbide ingot 190 at a preset cutting path and a preset cutting speed.

[0043] by Figure 1 and 2 As an example, the specific composition details of the scanning mechanism are shown.

[0044] In one example, if Figure 1 As shown, the scanning mechanism includes a focusing optical element 186 and a three-axis translation stage 187 for carrying the silicon carbide ingot 190. In addition, the scanning mechanism may also include other elements, for example, a reflector 181, a lens group (including a lens 182 and a lens 183, which form a 4f system) and a dichroic mirror 185, which are located between the focusing optical element 186 and the optical shaping element 170 and are arranged in sequence on the optical path. The three-axis translation stage 187 is located after the focusing optical element 186. However, it should be noted that the specific composition of the scanning mechanism is not limited to the above-mentioned elements, and those skilled in the art can select and adjust the composition of the scanning mechanism according to actual application requirements.

[0045] The reflector 181 is used to reflect the linear light beam obtained after being shaped by the beam shaping element 170 to the lens group; the lens group is used to shrink the linear light beam and perform spatial filtering; the dichroic mirror 185 is used to reflect the linear light beam to the focusing optical element 186 (for example, an objective lens); the focusing optical element 186 is used to focus the linear light beam into the interior of the silicon carbide ingot 190.

[0046] On this basis, the laser processing device further includes: a controller 109 and a charge-coupled device (CCD) 184 located after a dichroic mirror 185. The dichroic mirror 185 is also used to allow the imaging light source of the CCD 184 to enter the focusing optical element 186; the CCD 184 is used to perform imaging detection on the implementation process of the laser processing through the dichroic mirror 185; the controller 109 is used to control the repetition frequency, pulse width, pulse energy and other parameters of the Gaussian light beam emitted by the laser 110, and is also used to control the movement of the three-axis translation stage 187, and control the imaging of the CCD 184.

[0047] The controller 109 controls the movement of the three-axis translation stage 187 so that the linear light beam obtained after being focused by the focusing optical element 186 moves on the silicon carbide ingot 190 at a preset cutting path and a preset cutting speed. The preset cutting speed is 15 mm / s to 50 mm / s. Preferably, the preset cutting speed is 25 mm / s.

[0048] The controller 109 controls the three-axis translation stage 187 to achieve sub-micron level precise position adjustment, thereby improving cutting accuracy.

[0049] In another example, if Figure 2 As shown, the scanning mechanism includes a focusing optical element 188 and a galvanometer group (which includes a galvanometer 1871 and a galvanometer 1872). In addition, the scanning mechanism may also include other elements, for example, a reflector 181 located between the beam shaping element 170 and the galvanometer group and arranged in sequence on the optical path, a lens group (which includes a lens 182 and a lens 183, which form a 4f system), a dichroic mirror 185 and a reflector 186, and a three-axis translation stage 189 located after the focusing optical element 188 and used to carry the silicon carbide ingot 190. The focusing optical element 188 is located between the galvanometer group and the three-axis translation stage 189. However, it should be noted that the specific composition of the scanning mechanism is not limited to the above-mentioned elements, and those skilled in the art can select and adjust the composition of the scanning mechanism according to actual application requirements.

[0050] The reflector 181 is used to reflect the linear light beam obtained after being shaped by the beam shaping element 170 to the lens group; the lens group is used to shrink and spatially filter the linear light beam; the dichroic mirror 185 is used to reflect the linear light beam to the reflector 186; the reflector 186 is used to reflect the linear light beam to the galvanometer group; the galvanometer group is used to reflect the linear light beam to the focusing optical element 188 (for example, an objective lens); the focusing optical element 188 is used to focus the linear light beam into the interior of the silicon carbide ingot 190.

[0051] On this basis, the laser processing device further includes: a controller 109 and a CCD 184 located after a dichroic mirror 185. The dichroic mirror 185 is also used to allow the imaging light source of the CCD 184 to enter the focusing optical element 188; the CCD 184 is used to perform imaging detection on the implementation process of the laser processing through the dichroic mirror 185; the controller 109 is used to control the repetition frequency, pulse width, pulse energy and other parameters of the Gaussian light beam emitted by the laser 110, and is also used to control the deflection angle of the galvanometer group, and control the imaging of the CCD 184.

[0052] The controller 109 controls the deflection angle of the galvanometer group so that the linear light beam obtained after focusing by the focusing optical element 188 moves on the silicon carbide ingot 190 at a preset cutting path and a preset cutting speed. The preset cutting speed is 15 mm / s to 50 mm / s. Preferably, the preset cutting speed is 25 mm / s.

[0053] The controller 109 controls the galvanometer group to achieve high-speed and high-precision light beam scanning, and then cooperates with the objective lens to focus the light field, thereby improving the cutting efficiency and cutting accuracy.

[0054] It should be understood that Figure 2 The dotted line in the figure outlines the complete area that the linear beam can cover under the deflection of the galvanometer group. Figure 2 The maximum range that a linear beam can reach under the control of the galvanometer group is marked in Figure 2 The figure shows the complete spatial range that a linear beam can reach under the dynamic deflection of the galvanometer group.

[0055] It should be noted that Figure 1 and 2 The black thick lines are used schematically to represent the elements that the controller 109 can control. Those skilled in the art can select and adjust the elements that the controller 109 can control according to actual application requirements. For example, Figure 2 In the embodiment, the controller 109 can also control the movement of the three-axis translation stage 189, that is, the galvanometer group and the three-axis translation stage 189 work together to move the focused linear light beam on the silicon carbide ingot 190 at a preset cutting path and a preset cutting speed.

[0056] The focusing optical element 186 or 188 is not limited to the objective lens mentioned above, but may also be other elements with focusing function. Those skilled in the art may make different choices according to actual application requirements.

[0057] It should be understood that the reference to A being before or after B in this document means that A is before or after B along the propagation direction of light.

[0058] The process of shaping a Gaussian beam into a linear beam is described in detail below.

[0059] In one example, when the beam shaping element 170 is a diffractive optical element (DOE), Figure 1 and 2As shown, the laser processing device further includes: an angle stabilization component 120, a power adjustment component 130, a beam expander 140, a reflector 150, and a quarter wave plate 160, which are located between the laser 110 and the beam shaping element 170 and are arranged in sequence on the optical path. The angle stabilization component 120 is used to maintain the directional stability of the Gaussian beam during the collimation process, that is, to control the angle stability of the laser to ensure the collimation of the output optical path; the power adjustment component 130 is used to maintain the stability of the laser power; the beam expander 140 is used to expand the spot of the Gaussian beam emitted by the laser 110 to a preset multiple, for example, 3 to 10 times; the reflector 150 is used to reflect the Gaussian beam expanded by the beam expander 140 to the quarter wave plate 160; the quarter wave plate 160 is used to adjust the polarization state of the Gaussian beam to circularly polarized light.

[0060] The reason why a 1 / 4 wave plate 160 is arranged in front of the beam shaping element 170 is that the diffractive optical element is a diffractive optical element that realizes convergence or divergence of a light beam in a single direction based on the polarization state of the incident light. The rotation direction of the polarization state of the outgoing light of the diffractive optical element is opposite to the rotation direction of the polarization state of the incident light of the diffractive optical element. By controlling the polarization state of the incident light, the energy distribution of the converging light spot and the diverging light spot can be adjusted. Therefore, the polarization state of the incident light is controlled by the 1 / 4 wave plate 160.

[0061] like Figure 3 As shown, it shows a structural schematic diagram of a diffractive optical element, which is a diffraction device with a flat plate structure. The diffraction angle of the device is sinθ=λ / p, where θ is the diffraction angle, λ is the wavelength, and p is the period along the radial direction. The diffractive optical element has a continuously changing periodic structure, which makes it have a spherical aberration-free characteristic. Therefore, all light rays passing through the effective aperture are diffracted at different periodic positions on the x-axis, so that the light rays on the same x-axis line can be accurately converged to the same point and finally focused into a linear light beam, which is a vertical line perpendicular to the x-axis.

[0062] Diffractive optical elements modulate Gaussian beams using periodic microstructure patterns. These microstructure patterns can be convex or concave, and the phase change is achieved by changing the path length of the Gaussian beam when it passes through the material, thereby achieving a linear beam output.

[0063] The use of diffractive optical elements can realize the conversion between converging lenses and diverging lenses by adjusting the polarization state of the incident light. It has no physical bumps and is easier to integrate. Therefore, it has greater application prospects.

[0064] In another example, when the beam shaping element 170 is a spatial light modulator (SLM), it is not necessary to set Figure 1 and 2In other words, the laser processing device further includes: an angle stabilizing component 120, a power regulating component 130, a beam expander 140, and a reflector 150, which are located between the laser 110 and the beam shaping component 170 and are sequentially arranged on the optical path. In addition, in addition to controlling the above-mentioned components, the controller 109 also controls the spatial light modulator.

[0065] The spatial light modulator is a programmable beam shaping device. When the Gaussian beam emitted from the laser 110 passes through the target surface of the spatial light modulator, the liquid crystal layer changes the deflection direction of the liquid crystal molecules under the control of the electric field, thereby modulating the phase of the Gaussian beam. Subsequently, the controller 109 precisely controls the electric field so that the Gaussian beam is loaded with preset phase information, and finally realizes the output of a linear beam.

[0066] Before the electric field is precisely controlled, the computer generates a holographic phase map of the linear light beam using the GCS algorithm (Gerchberg-Saxton (GS) algorithm), and the spatial light modulator loads the holographic phase map of the linear light beam generated by the computer. When the controller 109 precisely controls the electric field, the Gaussian light beam is loaded with the preset phase information provided by the holographic phase map of the linear light beam, thereby finally realizing the output of the linear light beam.

[0067] The basic principle of the GCS algorithm is to solve the unknown phase distribution through iteration. In the Fraunhofer diffraction and lens focusing model, there is a reversible transformation relationship between the incident light field and the outgoing light field. The specific steps of the GCS algorithm are as follows.

[0068] Initialization: Randomly initialize the phase of the incident light field and synthesize the incident light field using the known amplitude distribution of the incident light field.

[0069] Forward transformation: The synthesized incident light field is diffracted by Fraunhofer and the phase of the outgoing light field is calculated.

[0070] Inverse transformation: Use the calculated phase of the outgoing light field and the known amplitude distribution of the outgoing light field to synthesize the new incident light field.

[0071] The above forward transformation and reverse transformation processes are iterated until the light field tends to be stable and the loss function (the mean square error between the calculated amplitude distribution of the output light field and the known amplitude distribution of the output light field) is minimized, and the holographic phase map of the linear light beam is obtained.

[0072] The spatial light modulator can improve the laser energy utilization rate and improve the laser uniformity, thereby enhancing the stability of the processing technology. At the same time, when the experimental linear beam is scanning the silicon carbide ingot, the beam shaping result can be controlled in real time through GCS without changing the optical path. Therefore, the operation is more flexible and the scope of application is wider.

[0073] The beam shaping element 170 is not limited to the diffractive optical element or spatial light modulator mentioned above, but may also be other elements with shaping functions. Those skilled in the art may make different choices according to actual application requirements.

[0074] However, it should be noted that the specific composition of the above-mentioned laser processing device is not limited to Figure 1 and 2 The above-listed components are shown in the figure. Those skilled in the art can select and adjust the composition of the laser processing device according to actual application requirements. For example, more reflectors or fewer reflectors can be used. In addition, the order of the components included in the laser processing device is not fixed. Those skilled in the art can select and adjust the components according to actual application requirements. Figure 1 and 2 Adjust the order of components shown in the figure.

[0075] The arrangement of the angle stabilizing component 120 and the power regulating component 130 can make the output of the laser parameters more stable, so as to ensure the stable generation of micro cracks inside the subsequent silicon carbide ingot.

[0076] The angle stabilization component 120 may include a deflecting mirror and a closed-loop controller. The closed-loop controller is an electronic system for continuously monitoring the deviation between the laser beam and the target position and controlling the deflecting mirror to adjust to maintain the stability of the laser beam. However, the embodiment of the present application does not limit the specific composition of the angle stabilization component, and those skilled in the art may make different choices according to actual application requirements.

[0077] The power regulating component 130 may include a laser power controller or an optical power regulator / limiter, etc. Those skilled in the art may make different choices according to actual application requirements.

[0078] Combine the following Figures 4 to 7 , a linear beam and a Gaussian beam are compared to better explain why using a linear beam to cut SiC ingots can improve the quality of SiC wafers.

[0079] like Figure 4 and 5As shown, it shows the light field distribution of the linear beam before focusing and the Gaussian beam before focusing on the XY plane. It can be seen that along the Y-axis direction (i.e., the first direction), the linear beam has a larger spot size than the Gaussian beam, and along the X-axis direction, the linear beam has a smaller spot size than the Gaussian beam. That is to say, compared with the Gaussian beam, the linear beam is elongated in the Y-axis direction and compressed in the X-axis direction, and the elongation degree on the Y-axis is much greater than the compression degree on the X-axis. Therefore, in the XY plane perpendicular to the optical axis, the linear beam has a larger light field area than the Gaussian beam. Compared with the Gaussian beam, the spot size of the linear beam in the Y-axis direction increases by 140% to 160%.

[0080] like Figure 6 As shown, it shows the spots of the focused linear beam and the focused Gaussian beam on the XY plane of the silicon carbide ingot 190. The spot size of the linear beam shown by the black ellipse along the Y-axis direction is much larger than the spot size of the Gaussian beam shown by the gray circle along the Y-axis direction.

[0081] like Figure 7 As shown in FIG. 1 , it shows the spots of the focused linear beam and the focused Gaussian beam on the YZ plane of the silicon carbide ingot 190. Along the Z-axis direction, that is, along the direction of the optical axis, the linear beam shown by the black ellipse has a smaller spot size than the Gaussian beam shown by the gray ellipse. Compared with the focused Gaussian beam, the spot size of the focused linear beam along the Z-axis direction is reduced by 20% to 30%.

[0082] After the Gaussian beam is tightly focused by the high numerical aperture focusing optical element 186 or 188 (e.g., objective lens), the spot size inside the silicon carbide ingot 190 is relatively long. However, after the linear beam is tightly focused by the same high numerical aperture focusing optical element, the spot size inside the silicon carbide ingot 190 is relatively short.

[0083] But it should be noted that Figure 4 and 6 This is just a schematic illustration of a possible form of the linear beam. By adjusting the beam shaping element 170, the linear beam can be elongated in the X-axis direction and compressed in the Y-axis direction. In other words, as long as the linear beam has a larger spot size in the first direction perpendicular to the preset cutting path than the Gaussian beam, the preset cutting path is as follows: Figure 6 As shown by the arrow line in the figure, the first direction refers to the vertical direction. Figure 6 In the figure, the first direction refers to the Y-axis direction. However, the first direction can be either the Y-axis direction or the X-axis direction, as long as it is perpendicular to the preset cutting path, and the present application does not make any specific limitation on this. Figure 6This is only a schematic illustration of a possible implementation in which the linear beam is perpendicular to the preset cutting path. In fact, the linear beam may also intersect with the preset cutting path, but it does not have to be perpendicular, as long as the linear beam has a larger spot size in the first direction than the Gaussian beam. When the linear beam intersects with the preset cutting path and is not perpendicular, the spot size of the linear beam in the first direction refers to the projection size of the linear beam in the first direction; when the linear beam intersects with the preset cutting path and is perpendicular, the spot size of the linear beam in the first direction refers to the actual size of the linear beam in the first direction.

[0084] On the one hand, since the focused linear beam has a smaller spot size than the focused Gaussian beam in the direction of the optical axis, this means that the action depth of the focused linear beam inside the silicon carbide ingot 190 is shallower, that is, the thickness of the loss layer where the microcracks are located is thinner, which not only reduces the length of the growth area of ​​the microcracks generated along the direction of the optical axis during the processing, thereby more accurately controlling the growth area of ​​the microcracks, but also effectively controls the thickness of the chemical decomposition layer under the action of the laser, and can also improve the utilization rate of the silicon carbide ingot, because the thinner the thickness of the loss layer where the microcracks are located, the more silicon carbide wafers can be cut from a whole silicon carbide ingot. On the other hand, since the linear beam has a larger light field area than the Gaussian beam in the XY plane perpendicular to the optical axis, the energy density of the linear beam is relatively low under the same laser parameter conditions, which helps to reduce the influence of thermal stress and thermal shock waves in the multi-pulse deposition process, thereby more accurately controlling the growth area of ​​the microcracks, and effectively controlling the thickness of the chemical decomposition layer under the action of the laser.

[0085] In addition, since the spot size of the linear light beam along the Y-axis direction is much larger than the spot size of the Gaussian light beam along the Y-axis direction, the interval between adjacent laser processing lines is correspondingly increased, that is, the laser processing line length is lengthened, which means that the number of times the laser acts on the silicon carbide ingot 190 (that is, the number of scans) is reduced, which reduces the influence of thermal stress and thermal shock waves during the multi-pulse deposition process, thereby more accurately controlling the growth area of ​​microcracks, and at the same time, the thickness of the chemical decomposition layer under the action of the laser is also effectively controlled.

[0086] The above mainly describes the advantages of linear beams from the perspective of cutting quality. The following will comprehensively explain the superiority of linear beams from the two dimensions of cutting quality and cutting efficiency.

[0087] When using laser cutting technology to cut silicon carbide ingots, although laser cutting technology brings many significant advantages, it is a challenge to achieve both the cutting efficiency and the cutting quality of silicon carbide ingots. On the one hand, efficiency and quality often restrict each other, and it is necessary to find a proper balance between the two; on the other hand, since silicon carbide ingots are both hard and fragile, ensuring that they are both efficient and maintain high quality during the cutting process increases the difficulty of this challenge.

[0088] In the current laser cutting technology, in order to improve the cutting efficiency of silicon carbide ingots, beam technologies such as multi-focus beams, flat-top beams or Bessel beams are usually used. Although these beams can improve the cutting efficiency to a certain extent, they cannot always ensure the cutting quality. This is because there are still some technical difficulties mentioned above that have not been completely overcome in the laser cutting technology of silicon carbide ingots. For example, the range of laser-induced microcracks is too large or the thickness of the chemical decomposition layer of silicon carbide under the action of laser is difficult to control, which will cause a certain degree of roughness on the surface of the silicon carbide wafer, thereby reducing the quality of the silicon carbide wafer. Therefore, although these beam technologies have played a role in improving cutting efficiency, further technical breakthroughs and optimization are still needed to ensure cutting quality.

[0089] Faced with such challenges, the laser processing solution proposed in this application uses a focused linear beam. Compared with the traditional focused Gaussian beam, the focused linear beam has a smaller spot size along the Z-axis direction, which helps to improve the cutting quality, which has been discussed in detail above. In addition, the focused linear beam also has a larger spot size along the Y-axis direction compared to the focused Gaussian beam, which increases the spacing between adjacent laser processing lines, thereby significantly improving the cutting efficiency, that is, the slicing efficiency. Therefore, it brings a double improvement in efficiency and quality to the processing of silicon carbide ingots.

[0090] Therefore, in the laser processing scheme of the present application, the use of a linear light beam to cut the silicon carbide ingot can not only reduce the roughness generated on the surface of the silicon carbide wafer, thereby improving the quality of the silicon carbide wafer, but also improve the cutting efficiency.

[0091] The above is a description from the perspective of a linear light beam of why the laser processing solution of the present application can improve the quality of silicon carbide wafers. The following will be described from the perspective of light source selection.

[0092] In order to more effectively control the growth area of ​​the microcracks, a specific light source may be selected, for example, a femtosecond laser may be selected as the type of laser 110. The heat-affected zone generated by the femtosecond laser when processing the silicon carbide ingot 190 is small, so microcracks are hardly formed outside the laser action area, thereby enabling precise control of the growth of the microcracks.

[0093] The femtosecond laser includes the following laser parameters: an adjustable repetition frequency of 0 to 2 MHz, an adjustable average power of 0 to 20 W, and an adjustable pulse width of 50 fs to 10 ps. During cutting, the focused linear beam has a pulse width of 190 fs to 350 fs, a repetition frequency of 50 KHz to 500 KHz, and an average power of 0.75 W to 1.5 W. Preferably, the pulse width is 300 fs, the repetition frequency is 100 KHz, and the average power is 1 W.

[0094] Since the pulse width of 190fs to 350fs (for example, 300fs) is less than the time of lattice vibration (1ps to 100ps), the energy deposition of a single pulse ends before the lattice vibration, thereby greatly reducing the generation of thermal effects. In addition, a repetition frequency of 50KHz to 500KHz (for example, 100KHz) combined with a preset cutting speed of 15mm / s to 50mm / s (for example, 25mm / s) can also greatly reduce the thermal effect caused by the accumulation of multiple pulses. The reduction of thermal effects means that the growth of microcracks can be precisely controlled.

[0095] When cutting the silicon carbide ingot 190, the distance between adjacent laser processing lines will also be considered because the femtosecond laser pulses generated by the femtosecond laser will generate a certain heat diffusion area. The distance between adjacent laser processing lines is made larger than the size of the heat diffusion area caused by the femtosecond laser pulse, thereby reducing the superposition effect of the heat diffusion area, and thus being able to accurately control the growth of microcracks. Figure 8 As shown, the interval d between adjacent laser processing lines 210 is 20 μm to 50 μm. Preferably, the interval d between adjacent laser processing lines 210 is 30 μm.

[0096] When the focused linear beam moves on the silicon carbide ingot 190 at a preset cutting path and a preset cutting speed, the interior of the silicon carbide ingot 190 is modified to form a silicon carbide modified layer 191. The silicon carbide modified layer 191 serves as the base point for separating the silicon carbide wafers, and in combination with the subsequent auxiliary splitting process, the silicon carbide wafer can be smoothly cut from the silicon carbide ingot 190 to obtain the following Fig. 9 and 10 The silicon carbide wafer shown.

[0097] Fig.10 shows the surface morphology of a silicon carbide wafer; Fig. 9 The roughness of the silicon carbide wafer is shown in the form of a color image. In a color image, different colored marks are generally used to indicate the height difference of the wafer surface. The more different colored marks there are, the greater the height difference of the wafer surface, that is, the more uneven the surface is.

[0098] exist Fig. 9 In the middle, mark M red and mark M blue The number is not large, indicating that the surface of the silicon carbide wafer is relatively flat, that is, its surface roughness is good.

[0099] In addition, when the focused linear light beam moves on the silicon carbide ingot 190, the focused linear light beam can not only modify the cutting path being traveled, but also produce a pre-modification effect on the adjacent cutting path perpendicular to the cutting path being traveled, which makes the growth of microcracks more uniform and controllable, thereby reducing the difficulty of the subsequent splitting process and improving the quality of the silicon carbide wafer.

[0100] Therefore, in the laser processing scheme of the present application, a femtosecond laser with preset laser parameters is used, combined with a preset cutting speed and the spacing between laser processing lines, to cut the silicon carbide ingot, which can also reduce the roughness generated on the surface of the silicon carbide wafer, thereby improving the quality of the silicon carbide wafer.

[0101] In summary, whether using a linear spot or a femtosecond laser, the purpose is to concentrate the microcracks on the cutting path as much as possible, so that the microcracks will not expand to the surrounding areas due to the heat diffusion of the laser, thereby being able to accurately control the growth of the microcracks.

[0102] In the present application, the laser light field is regulated by an optical shaping element, so that the laser is loaded with preset information after passing through the optical shaping element to obtain a linear beam, and then the linear beam is focused inside the silicon carbide ingot through a focusing optical element to cut the silicon carbide ingot. By controlling the angle (i.e., collimation) of the linear beam, power control, and light field regulation, microcracks inside the silicon carbide ingot are stably generated, and with the subsequent auxiliary splitting process, high-quality silicon carbide wafers are obtained.

[0103] Combination of the above Figures 1 to 10 , describes in detail the device embodiment of the present application, and the following is combined with Fig.11 , describe the method embodiments of the present application in detail.

[0104] Fig.11 1 is a flow chart of a method for cutting a silicon carbide ingot provided in an embodiment of the present application. The cutting method is executed by the controller 109 in the above device embodiment, and the parts not described in detail can be referred to the above device embodiment. The cutting method includes the following contents.

[0105] S1110: Control the laser processing device to output a focused linear light beam having preset laser parameters.

[0106] The laser processing device includes Figure 1 or Figure 2 The controller controls the laser to emit a Gaussian beam with preset laser parameters. After the Gaussian beam is transmitted to the optical shaping element, it is shaped into a linear beam with preset laser parameters. Then, the linear beam is focused by the focusing optical element to obtain a focused linear beam.

[0107] Preset laser parameters include pulse widths from 190fs to 350fs, repetition rates from 50KHz to 500KHz, and average powers from 0.75W to 1.5W.

[0108] S1120: Control the focused linear light beam to move on the silicon carbide ingot at a preset cutting path and a preset cutting speed, and modify the interior of the silicon carbide ingot to complete the cutting of the silicon carbide ingot.

[0109] The controller controls the scanning mechanism so that the focused linear light beam moves on the silicon carbide ingot at a preset cutting path and a preset cutting speed. During the movement of the focused linear light beam, the interior of the silicon carbide ingot is modified to complete the cutting of the silicon carbide ingot.

[0110] The spacing between adjacent laser processing lines in the preset cutting path is 20 μm to 50 μm, and the preset cutting speed is 15 mm / s to 50 mm / s.

[0111] Compared with the focused Gaussian beam, the focused linear beam has a small spot size along the direction of the optical axis and a large spot size in a first direction perpendicular to the preset cutting path, and the direction of the optical axis is perpendicular to the first direction.

[0112] In the cutting scheme of silicon carbide ingot provided in the present application, the controller controls the laser processing device to output a focused linear beam with preset laser parameters, and controls the focused linear beam to move on the silicon carbide ingot at a preset cutting path and a preset cutting speed, and modifies the inside of the silicon carbide ingot to complete the cutting of the silicon carbide ingot. Compared with the focused Gaussian beam, the spot size of the focused linear beam along the direction of the optical axis is smaller, which means that the action depth of the focused linear beam inside the silicon carbide ingot is shallower, thereby reducing the length of the growth area of ​​the microcracks generated along the direction of the optical axis during the processing, thereby reducing the roughness generated on the surface of the silicon carbide wafer, thereby improving the quality of the silicon carbide wafer.

[0113] Combination of the above Fig.11 , describes the method embodiment of the present application in detail, and the following is combined with Fig.12 , describes in detail the system embodiment of the present application. It should be understood that the description of the method embodiment corresponds to the description of the system embodiment, so the parts not described in detail can refer to the previous method embodiment.

[0114] Fig.12 1 is a schematic diagram of the structure of a silicon carbide ingot cutting system provided in an embodiment of the present application. The cutting system 1200 may include: a first control module 1210 and a second control module 1220. These modules are described in detail below.

[0115] The first control module 1210 is used to control the laser processing device to output a focused linear beam with preset laser parameters.

[0116] The second control module 1220 is used to control the focused linear light beam to move on the silicon carbide ingot at a preset cutting path and a preset cutting speed, and to modify the interior of the silicon carbide ingot to complete the cutting of the silicon carbide ingot.

[0117] Fig.13 13 is a block diagram of a laser processing system provided in an embodiment of the present application. The laser processing system 1300 may be, for example, a computing device having computing functions. The laser processing system 1300 may include a memory 1310 and a processor 1320 (which may be understood as the controller 109 described above). The memory 1310 may be used to store executable code. The processor 1320 may be used to execute the executable code stored in the memory 1310 to implement the steps in the various methods described above. In some embodiments, the laser processing system 1300 may also include a network interface 1330, and data exchange between the processor 1320 and an external device may be implemented through the network interface 1330.

[0118] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any other combination. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loading and executing computer program instructions on a computer, the process or function according to the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network or other programmable devices. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from a website site, a computer, a server or a data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (Digital Subscriber Line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server, a data center, etc. that contains one or more available media integrations. The available media may be magnetic media (eg, floppy disks, hard disks, magnetic tapes), optical media (eg, digital video discs (DVD)), or semiconductor media (eg, solid state disks (SSD)).

[0119] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments of the present application can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0120] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0121] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0122] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0123] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A laser processing device, characterized in that: include: A laser, configured to emit a Gaussian beam having preset laser parameters; A beam shaping element, used for shaping the Gaussian beam into a linear beam; A scanning mechanism is used to focus the linear light beam and use the focused linear light beam to cut the silicon carbide ingot at a preset cutting path and a preset cutting speed. Compared with the focused Gaussian beam, the focused linear beam has a smaller spot size along the direction of the optical axis.

2. The laser processing device according to claim 1, characterized in that: Compared with the focused Gaussian beam, the focused linear beam has a large spot size in a first direction perpendicular to a preset cutting path, and the direction of the optical axis is perpendicular to the first direction.

3. The laser processing device according to claim 1, characterized in that: The beam shaping element includes a diffractive optical element or a spatial light modulator.

4. The laser processing device according to any one of claims 1 to 3, characterized in that: Also includes: a controller, configured to control the laser to emit the Gaussian beam having the preset laser parameters, and control the scanning mechanism so that the focused linear beam cuts the silicon carbide ingot at the preset cutting path and the preset cutting speed; and / or The laser processing device further includes: a controller, wherein the scanning mechanism includes a focusing optical element and a three-axis translation stage for carrying the silicon carbide ingot, the focusing optical element is used to focus the linear light beam to obtain the focused linear light beam, and the controller controls the three-axis translation stage to move so that the focused linear light beam moves on the silicon carbide ingot at the preset cutting path and the preset cutting speed; and / or The laser processing device also includes: a controller, wherein the scanning mechanism includes a focusing optical element and a galvanometer group, the focusing optical element is used to focus the linear light beam to obtain the focused linear light beam, and the controller controls the deflection angle of the galvanometer group to make the focused linear light beam move on the silicon carbide ingot along the preset cutting path and the preset cutting speed.

5. The laser processing device according to any one of claims 1 to 3, characterized in that: The preset cutting speed is 15 mm / s to 50 mm / s, and the spacing between adjacent laser processing lines in the preset cutting path is 20 μm to 50 μm.

6. The laser processing device according to any one of claims 1 to 3, characterized in that: The laser comprises a femtosecond laser, and the preset laser parameters comprise: a pulse width of 190 fs to 350 fs, a repetition frequency of 50 KHz to 500 KHz, and an average power of 0.75 W to 1.5 W.

7. A method for cutting a silicon carbide ingot, characterized in that: include: Controlling the laser processing device to output a focused linear beam having preset laser parameters; Controlling the focused linear light beam to move on the silicon carbide ingot at a preset cutting path and a preset cutting speed, and modifying the interior of the silicon carbide ingot to complete the cutting of the silicon carbide ingot, Compared with the focused Gaussian beam, the focused linear beam has a smaller spot size along the direction of the optical axis.

8. The cutting method according to claim 7, characterized in that: Compared with the focused Gaussian beam, the focused linear beam has a large spot size in a first direction perpendicular to a preset cutting path, and the direction of the optical axis is perpendicular to the first direction.

9. The cutting method according to claim 7 or 8, characterized in that: The spacing between adjacent laser processing lines in the preset cutting path is 20μm to 50μm, the preset cutting speed is 15mm / s to 50mm / s, and the preset laser parameters include a pulse width of 190fs to 350fs, a repetition frequency of 50KHz to 500KHz, and an average power of 0.75W to 1.5W.

10. A laser processing system comprising: A memory and a processor, wherein the memory stores executable codes, and the processor is configured to execute the executable codes to implement the method for cutting a silicon carbide ingot according to any one of claims 7 to 9.

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