Laser processing device

Abstract

The utility model discloses a laser processing device. 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 utility model relates to laser technology field, concretely relates to a laser processing device. BACKGROUND

[0002] In today's rapid development of global semiconductor industry, silicon carbide (Silicon Carbide, SiC) with its outstanding physical and chemical properties, become the key material for manufacturing high performance electronic devices. The production cost of silicon carbide is very high, in order to reduce the cost, need to cut a large silicon carbide crystal into as many thin silicon carbide wafers as possible, but the hardness of silicon carbide is extremely high, and also has the brittleness of crystal, very difficult to cut.

[0003] At present, laser cutting technology is usually used to cut (also called slicing) silicon carbide crystal. In the process of cutting silicon carbide crystal by laser cutting technology, although laser cutting technology has many advantages, but it is inevitable that a certain degree of roughness will be produced on the surface of silicon carbide wafer, thereby reducing the quality of silicon carbide wafer. UTILITY MODEL CONTENT

[0004] Therefore, the utility model provides a kind of laser processing device, roughness produced on the surface of silicon carbide wafer can be reduced, thereby improving the quality of silicon carbide wafer.

[0005] The utility model embodiment provides a kind of laser processing device, it includes: laser, for emitting Gaussian beam with preset laser parameter;Beam shaping element, for shaping Gaussian beam into linear beam;Scanning mechanism, for focusing linear beam, and using the linear beam after focusing, with preset cutting path and preset cutting speed, to the silicon carbide crystal for cutting, wherein, compared with the Gaussian beam after focusing, the linear beam after focusing has small spot size in the direction of optical axis.

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

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

[0008] In some embodiments, the laser processing device further includes: controller, for controlling laser to emit Gaussian beam with preset laser parameter, and controlling scanning mechanism, to make the linear beam after focusing cut silicon carbide crystal with preset cutting path and preset cutting speed.

[0009] In some embodiments, the laser processing device further comprises a controller, the scanning mechanism comprises a focusing optical element and a three-axis displacement table for carrying the silicon carbide crystal ingot, the focusing optical element is used for focusing the linear light beam to obtain a focused linear light beam, and the controller controls the three-axis displacement table to move so that the focused linear light beam moves on the silicon carbide crystal ingot at a preset cutting path and a preset cutting speed.

[0010] In some embodiments, the laser processing device further comprises a controller, the scanning mechanism comprises a focusing optical element and a galvanometer group, the focusing optical element is used for focusing the linear light beam to obtain a focused linear light beam, and the controller controls the deflection angle of the galvanometer group so that the focused linear light beam moves on the silicon carbide crystal ingot at a preset cutting path and a preset cutting speed.

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

[0012] In some embodiments, the preset cutting speed is 25mm / s, and the spacing between adjacent laser processing lines in the preset cutting path is 30μm.

[0013] In some embodiments, the laser comprises a femtosecond laser, and the preset laser parameters comprise a pulse width of 190fs to 350fs, a repetition frequency of 50KHz to 500KHz, and an average power of 0.75W to 1.5W.

[0014] In some embodiments, the preset laser parameters comprise a repetition frequency of 100KHz, an average power of 1W, and a pulse width of 300fs.

[0015] In the laser processing scheme provided by the utility model, the focused linear light beam is used to cut the silicon carbide crystal ingot at a preset cutting path and a preset cutting speed, compared with the focused Gaussian light beam, the spot size of the focused linear light beam in the direction of the optical axis is smaller, which means that the action depth of the focused linear light beam in the silicon carbide crystal ingot is shallower, thereby reducing the length of the growth area of the microcracks generated in the processing process in the direction of the optical axis, and further reducing the roughness generated on the surface of the silicon carbide wafer, thus improving the quality of the silicon carbide wafer. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the structure schematic view of the laser processing device provided by an embodiment of the utility model.

[0017] Figure 2 is the structure schematic view of the laser processing device provided by another embodiment of the utility model.

[0018] Figure 3 is a structural schematic diagram of a diffractive optical element provided by an embodiment of the present application.

[0019] Figure 4 is a schematic diagram of light field distribution of a linear light beam in XY plane provided by an embodiment of the present application.

[0020] Figure 5 is a schematic diagram of light field distribution of a Gaussian light beam in XY plane provided by an embodiment of the present application.

[0021] Figure 6 is a schematic diagram of light spot of a Gaussian light beam and a linear light beam in XY plane of a silicon carbide ingot provided by an embodiment of the present application.

[0022] Figure 7 is a schematic diagram of light spot of a Gaussian light beam and a linear light beam in YZ plane of a silicon carbide ingot provided by an embodiment of the present application.

[0023] Figure 8 is a schematic diagram of a cutting path of a linear light beam in XY plane of a silicon carbide ingot provided by an embodiment of the present application.

[0024] Figure 9 is a topographic profile of a confocal microscope surface roughness of a silicon carbide wafer provided by an embodiment of the present application.

[0025] Figure 10 is a confocal microscope imaging diagram of a silicon carbide wafer provided by an embodiment of the present application.

[0026] Figure 11 is a flowchart of a cutting method of a silicon carbide ingot provided by an embodiment of the present application.

[0027] Figure 12 is a structural schematic diagram of a cutting system of a silicon carbide ingot provided by an embodiment of the present application.

[0028] Figure 13 is a block diagram of a laser processing system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0029] The exemplary embodiments will be described in detail below with reference to the drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise described. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0030] The terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used in this application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0031] At present, there are still some technical difficulties in the laser cutting technology of silicon carbide ingots, for example, the range of laser-induced micro-cracks is too large or the thickness of the chemical decomposition layer of silicon carbide under the action of laser is difficult to control, etc., 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.

[0032] However, it should be noted that the present application is not limited to the cutting of silicon carbide ingots, but also applies to the cutting of other brittle and hard inorganic non-metallic materials or semiconductor materials, such as glass and silicon wafers, etc. These materials will encounter similar problems in the cutting process as silicon carbide ingots, such as the range of laser-induced micro-cracks being too large or the thickness of the chemical decomposition layer of silicon carbide under the action of laser being difficult to control, etc. Therefore, the solution proposed in the present application has wide applicability and can provide technical support for the precision cutting of various hard and brittle materials.

[0033] For ease of understanding, the generation of micro-cracks and the generation of chemical decomposition layer will be briefly introduced below.

[0034] The laser is focused inside the silicon carbide, and due to the accumulation of heat, a gradient thermal affected zone is formed inside the silicon carbide. In the thermal affected zone, the thermal stress on the silicon carbide is different, so uneven stress will form micro-cracks.

[0035] The chemical decomposition layer usually refers to the chemical change of silicon carbide under laser irradiation, which leads to the decomposition of the material into its constituent elements or new phases of compounds. For example, laser-induced phase separation can cause silicon carbide to decompose into amorphous silicon and amorphous carbon, and even further transform into multi-layer graphene. The formation of such decomposition layer usually involves the interaction of laser and material, such as high-power laser beam focused on the surface of the material, leading to rapid heating and phase change in the local area.

[0036] The formation of chemical decomposition layer may also be accompanied by the generation of micro-cracks, which can form inside the material, affecting the integrity and mechanical properties of the material.

[0037] It is found through research that the spot shape of the laser and the heat diffusion of the laser can both cause the micro-cracks to spread in all directions, thereby causing a certain degree of roughness to appear on the surface of the silicon carbide wafer, and further affecting the quality of the silicon carbide wafer. Therefore, in order to avoid the spread of micro-cracks, the generation of micro-cracks should be concentrated on the laser scanning path (i.e., the cutting path described below) as much as possible. However, in the face of numerous choices of spot shapes and laser parameters, which spot shape of the light beam and which laser parameter of the laser to use for cutting the silicon carbide ingot becomes a key factor in determining the cutting effect.

[0038] Through further series of experimental exploration and theoretical research, it is found that using a linear light beam to cut the silicon carbide ingot can effectively control the growth of micro-cracks 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 light beam along different axes, for example, the focused linear light beam has a small spot size (also known as focal depth) along the optical axis, thereby reducing the length of the growth area of the micro-cracks generated along the optical axis in the processing process, and for another example, the focused linear light 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 in the multi-pulse deposition process. Therefore, the growth area of the micro-cracks is better controlled, and at the same time the thickness of the chemical decomposition layer under the action of the laser is also effectively controlled.

[0039] The laser processing device provided by the embodiment of the present application will be described in more detail below in combination with Figure 1 and 2 .

[0040] As shown in Figure 1 and 2 , the laser processing device comprises 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 light beam with preset laser parameters, the beam shaping element 170 is used to shape the Gaussian light beam emitted by the laser 110 into a linear light beam, and the scanning mechanism is used to focus the linear light beam and cut the silicon carbide ingot 190 with a preset cutting path and a preset cutting speed using the focused linear light beam.

[0041] For example, the specific composition details of the scanning mechanism are shown. Figure 1 and 2 .

[0042] In an example, as shown in Figure 1 , the scanning mechanism comprises a scanning mirror 120 and a focusing lens 130.As shown, the scanning mechanism includes a condensing optical element 186 and a three-axis displacement table 187 for carrying the silicon carbide crystal ingot 190. In addition, the scanning mechanism can also include other elements, for example, a mirror 181 located between the condensing optical element 186 and the optical shaping element 170 and arranged in sequence on the optical path, a lens group (which includes a lens 182 and a lens 183, which constitutes a 4f system), and a dichroic mirror 185. The three-axis displacement table 187 is located behind the condensing 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 the actual application requirements.

[0043] The mirror 181 is used to reflect the linear light beam obtained after the beam shaping element 170 to the lens group; the lens group is used to shrink the beam and perform spatial filtering on the linear light beam; the dichroic mirror 185 is used to reflect the linear light beam to the condensing optical element 186 (for example, an objective lens); and the condensing optical element 186 is used to focus the linear light beam into the interior of the silicon carbide crystal ingot 190.

[0044] On this basis, the laser processing device further includes a controller 109 and a charge-coupled device (CCD) 184 located behind the dichroic mirror 185. The dichroic mirror 185 is also used to make the imaging light source of the CCD 184 enter the condensing optical element 186; the CCD 184 is used to image and detect the implementation process of the laser processing through the dichroic mirror 185; and the controller 109 is used to control the repetition frequency, pulse width, and pulse energy of the Gaussian light beam emitted by the laser 110, and is also used to control the movement of the three-axis displacement table 187 and the imaging of the CCD 184.

[0045] The controller 109 controls the movement of the three-axis displacement table 187, so that the linear light beam focused by the condensing optical element 186 moves on the silicon carbide crystal ingot 190 at a preset cutting speed and a preset cutting path. The preset cutting speed is 15 mm / s to 50 mm / s, and preferably, the preset cutting speed is 25 mm / s.

[0046] The controller 109 controls the three-axis displacement table 187 to achieve sub-micron level accurate position adjustment, thereby improving the cutting accuracy.

[0047] In another example, as Figure 2As shown, the scanning mechanism includes a condensing optical element 188 and a galvanometer set (which includes a galvanometer 1871 and a galvanometer 1872). In addition, the scanning mechanism can also include other elements, for example, a mirror 181 located between the beam shaping element 170 and the galvanometer set and arranged in sequence on the light path, a lens set (which includes a lens 182 and a lens 183, which constitutes a 4f system), a dichroic mirror 185 and a mirror 186, and a three-axis displacement table 189 located behind the condensing optical element 188 and used to carry the silicon carbide crystal ingot 190. The condensing optical element 188 is located between the galvanometer set and the three-axis displacement table 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 the actual application requirements.

[0048] The mirror 181 is used to reflect the linear light beam obtained after the beam shaping element 170 to the lens set; the lens set 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 mirror 186; the mirror 186 is used to reflect the linear light beam to the galvanometer set; the galvanometer set is used to reflect the linear light beam to the condensing optical element 188 (for example, an objective lens); and the condensing optical element 188 is used to focus the linear light beam to the inside of the silicon carbide crystal ingot 190.

[0049] On this basis, the laser processing device further includes a controller 109 and a CCD 184 located behind the dichroic mirror 185. The dichroic mirror 185 is also used to make the imaging light source of the CCD 184 enter the condensing optical element 188; the CCD 184 is used to image and detect the implementation process of the laser processing through the dichroic mirror 185; and the controller 109 is used to control the repetition frequency, pulse width and pulse energy of the Gaussian light beam emitted by the laser 110, and is also used to control the deflection angle of the galvanometer set and the imaging of the CCD 184.

[0050] The controller 109 controls the deflection angle of the galvanometer set, so that the linear light beam obtained after being focused by the condensing optical element 188 moves on the silicon carbide crystal ingot 190 at a preset cutting speed and a preset cutting path. The preset cutting speed is 15 mm / s to 50 mm / s, and preferably, the preset cutting speed is 25 mm / s.

[0051] The controller 109 controls the galvanometer set to realize high-speed and high-precision beam scanning, and cooperates with the objective lens to focus the light field, thereby improving the cutting efficiency and cutting precision.

[0052] It should be understood that, Figure 2 The dashed line in the above figure outlines the complete area that can be covered by the linear light beam under the deflection action of the galvanometer set. The dashed line is in the direction of the arrow in the figure. Figure 2The dashed line indicates the maximum range that the linear beam can reach under the control of the galvanometer group, that is, the dashed line indicates the complete spatial range that the linear beam can reach under the dynamic deflection of the galvanometer group. Figure 2 The dashed line indicates the maximum range that the linear beam can reach under the control of the galvanometer group, that is, the dashed line indicates the complete spatial range that the linear beam can reach under the dynamic deflection of the galvanometer group.

[0053] It should be noted that, Figure 1 and 2 The elements that can be controlled by the controller 109 are only schematically represented by the thick black lines therein, and those skilled in the art can select and adjust the elements that can be controlled by the controller 109 according to actual application requirements, for example, in Figure 2 , the controller 109 can also control the movement of the three-axis displacement table 189, that is, the galvanometer group and the three-axis displacement table 189 work together to move the focused linear beam on the silicon carbide ingot 190 at a preset cutting path and a preset cutting speed.

[0054] The condensing optical element 186 or 188 is not limited to the above-mentioned objective lens, but can also be other elements with focusing function, and those skilled in the art can make different selections according to actual application requirements.

[0055] It should be understood that the A mentioned herein before or after B means that A is before or after B along the direction of light propagation.

[0056] The process of shaping the Gaussian beam into a linear beam will be described in detail below.

[0057] In an example, in the case of the beam shaping element 170 being a diffractive optical element (DOE), as shown in Figure 1 and 2 , the laser processing device further comprises an angle stabilization assembly 120, a power adjustment assembly 130, a beam expander 140, a mirror 150 and a 1 / 4 wave plate 160 arranged in sequence on the optical path between the laser 110 and the beam shaping element 170. The angle stabilization assembly 120 is used to maintain the directional stability of the Gaussian beam during collimation, that is, to control the angle stability of the laser to ensure the collimation of the output light path; the power adjustment assembly 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 mirror 150 is used to reflect the Gaussian beam expanded by the beam expander 140 to the 1 / 4 wave plate 160; the 1 / 4 wave plate 160 is used to adjust the polarization state of the Gaussian beam to circularly polarized light.

[0058] The reason for setting the 1 / 4 wave plate 160 in front of the beam shaping element 170 is that the diffractive optical element is a diffractive optical element that realizes the convergence or divergence of the light beam in a single direction based on the polarization state of the incident light. The handedness of the polarization state of the outgoing light of the diffractive optical element is opposite to the handedness 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 convergent and divergent light spots can be adjusted. Therefore, the polarization state of the incident light is controlled by the 1 / 4 wave plate 160.

[0059] As shown in FIG. 1, a schematic diagram of a diffractive optical element is shown. The diffractive optical element is a diffractive device with a flat plate structure. The diffraction angle of the device is sin θ = λ / p, where θ is the diffraction angle, λ is the wavelength, and p is the period in the radial direction. The diffractive optical element has a continuously varying period structure, so it has an aplanatic characteristic. Therefore, all light rays passing through the effective aperture are diffracted at different period positions on the x-axis, so that the light rays on the same x-axis can be precisely converged to the same point, and finally focused into a linear beam. This linear beam is a vertical line perpendicular to the x-axis. Figure 3

[0060] The diffractive optical element modulates the Gaussian beam using the microstructure pattern of the period structure. These microstructure patterns can be convex or concave, and the phase change is achieved by changing the path length of the Gaussian beam passing through the material, so that the output of the linear beam can be achieved.

[0061] Using the diffractive optical element, the conversion of the convergent lens and the divergent lens can be realized by adjusting the polarization state of the incident light, and there is no physical concave-convex structure, which is easier to integrate, so it has greater application prospects.

[0062] In another example, when the beam shaping element 170 is a spatial light modulator (SLM), the 1 / 4 wave plate 160 in Figure 1 and 2 may not be set, that is, the laser processing device further includes an angle stabilization assembly 120, a power adjustment assembly 130, a beam expander 140, and a mirror 150 arranged in sequence in the optical path between the laser 110 and the beam shaping element 170. In addition, the controller 109 controls not only the above-mentioned elements, but also the spatial light modulator.

[0063] 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 adjusts the electric field so that the Gaussian beam loads the preset phase information, and finally realizes the output of the linear beam. ​

[0064] Before the electric field is precisely regulated, the computer generates the holographic phase pattern of the linear light beam by using the Graph Cuts algorithm (GCS), the spatial light modulator loads the holographic phase pattern of the linear light beam generated by the computer, and when the controller 109 precisely regulates the electric field, the Gaussian light beam loads the preset phase information provided by the holographic phase pattern of the linear light beam, and finally realizes the output of the linear light beam.

[0065] The basic principle of the GCS algorithm is to solve the unknown phase distribution by iteration. In the Fraunhofer diffraction and lens focusing model, there is a reversible transformation relationship between the incident light field and the exit light field. The specific steps of the GCS algorithm are as follows.

[0066] 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.

[0067] Forward transformation: synthesize the incident light field by Fraunhofer diffraction, and calculate the phase of the exit light field.

[0068] Inverse transformation: synthesize a new incident light field using the calculated phase of the exit light field and the known amplitude distribution of the exit light field.

[0069] Iterate the above forward transformation and inverse transformation process until the light field tends to be stable and the loss function (the mean square error of the calculated amplitude distribution of the exit light field and the known amplitude distribution of the exit light field) reaches the minimum, and the holographic phase pattern of the linear light beam is obtained.

[0070] The spatial light modulator can improve the utilization rate of laser energy and improve the uniformity of the laser, thereby enhancing the stability of the processing technology. At the same time, when the experimental linear light beam scans the silicon carbide crystal ingot, the beam shaping result can be controlled in real time by GCS, without the need to replace the optical path, so the operation is more flexible and the application range is also more extensive.

[0071] The beam shaping element 170 is not limited to the above-mentioned diffractive optical element or spatial light modulator, but can also be other elements with shaping function. Those skilled in the art can make different choices according to actual application needs.

[0072] However, it should be noted that the specific composition of the above-mentioned laser processing device is not limited to the above-mentioned elements shown in Figure 1 and 2 Those skilled in the art can select and adjust the composition of the laser processing device according to actual application needs, for example, more mirrors or fewer mirrors. In addition, the order of the elements included in the laser processing device is not fixed, and those skilled in the art can adjust the order of the elements according to actual application needs, for example, Figure 1 and2 The order of the elements shown in the middle is adjusted.

[0073] The arrangement of the angle stabilizing assembly 120 and the power adjusting assembly 130 can make the output of the laser parameters more stable, so as to ensure the stable generation of the internal micro-cracks of the subsequent silicon carbide ingot.

[0074] The angle stabilizing assembly 120 can include a deflecting mirror and a closed-loop controller, which is an electronic system for continuously monitoring the deviation of the laser beam from the target position and controlling the deflecting mirror to adjust to keep the laser beam stable. However, the specific composition of the angle stabilizing assembly is not limited in the embodiments of the present application, and those skilled in the art can make different selections according to the actual application requirements.

[0075] The power adjusting assembly 130 can include a laser power controller or an optical power adjuster / limiter, etc., and those skilled in the art can make different selections according to the actual application requirements.

[0076] The following will be combined Figures 4 to 7 to compare the linear light beam and the Gaussian light beam, so as to better explain why the linear light beam is used for cutting the silicon carbide ingot to improve the quality of the silicon carbide wafer.

[0077] As shown in Figure 4 and 5 , which respectively show the light field distribution of the linear light beam before focusing and the Gaussian light beam before focusing in the XY plane, it can be seen that, along the Y-axis direction (i.e., the first direction), the linear light beam has a larger spot size than the Gaussian light beam, and along the X-axis direction, the linear light beam has a smaller spot size than the Gaussian light beam. That is, compared with the Gaussian light beam, the linear light beam is elongated in the Y-axis direction and compressed in the X-axis direction, and the elongation degree in the Y-axis direction is much greater than the compression degree in the X-axis direction, so that in the XY plane perpendicular to the optical axis, the linear light beam has a larger light field area than the Gaussian light beam. Compared with the Gaussian light beam, the spot size of the linear light beam in the Y-axis direction is increased by 140% to 160%.

[0078] As shown in Figure 6 , which shows the spot of the linear light beam after focusing and the Gaussian light beam after focusing in the XY plane of the silicon carbide ingot 190, the spot size of the linear light beam shown by the black oval along the Y-axis direction is much larger than the spot size of the Gaussian light beam shown by the gray circle along the Y-axis direction.

[0079] As shown in Figure 7As shown in FIG. 6, it shows the spot of the focused linear beam and the focused Gaussian beam on the YZ plane of the silicon carbide ingot 190. The linear beam shown by the black ellipse has a smaller spot size along the Z axis direction, i.e., along the direction of the optical axis, compared with the Gaussian beam shown by the gray ellipse. The spot size of the focused linear beam along the Z axis direction is reduced by 20% to 30% compared with the focused Gaussian beam.

[0080] After the Gaussian beam is tightly focused by the high numerical aperture condensing optical element 186 or 188 (e.g., an objective lens), the spot size inside the silicon carbide ingot 190 is relatively long. After the linear beam is tightly focused by the same high numerical aperture condensing optical element, the spot size inside the silicon carbide ingot 190 is relatively short.

[0081] However, it should be noted that, Figure 4 and 6 Only one possible shape of the linear beam is shown schematically. By adjusting the beam shaping element 170, the linear beam can also be elongated in the X axis direction and compressed in the Y axis direction. That is, as long as the linear beam has a larger spot size in the first direction perpendicular to the preset cutting path compared with the Gaussian beam. The preset cutting path is shown by the arrow line in Figure 6 , the first direction refers to the vertical direction, and Figure 6 , 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, which is not limited in the utility model. Figure 6 Only one possible implementation in which the linear beam is perpendicular to the preset cutting path is shown schematically. In fact, the linear beam can 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 compared with 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.

[0082] On the one hand, since the focused linear beam has a smaller spot size in the direction of the optical axis than the focused Gaussian beam, it means that the focused linear beam has a shallower action depth inside the silicon carbide ingot 190, that is, the thickness of the micro-crack-containing loss layer is thinner, which not only reduces the length of the micro-crack growth area generated in the processing process in the direction of the optical axis, thereby more accurately controlling the micro-crack growth area, but also effectively controls the chemical decomposition layer thickness 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 micro-crack-containing loss layer, 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 in the multi-pulse deposition process, thereby more accurately controlling the micro-crack growth area, and effectively controlling the chemical decomposition layer thickness under the action of the laser.

[0083] In addition, since the spot size of the linear beam along the Y-axis direction is much larger than that of the Gaussian beam along the Y-axis direction, the spacing between adjacent laser processing lines also increases accordingly, that is, the laser processing line length becomes longer, which means that the number of laser actions on the silicon carbide ingot 190 (i.e., the number of scans) is reduced, which reduces the influence of thermal stress and thermal shock in the multi-pulse deposition process, thereby more accurately controlling the micro-crack growth area, and effectively controlling the chemical decomposition layer thickness under the action of the laser.

[0084] The above mainly describes the advantages of the linear beam from the perspective of cutting quality, and the superiority of the linear beam will be comprehensively described from the two dimensions of cutting quality and cutting efficiency.

[0085] When using laser cutting technology to cut the silicon carbide ingot, although the laser cutting technology brings many significant advantages, it is a challenge to realize the dual improvement of the cutting efficiency of the silicon carbide ingot and the cutting quality of the silicon carbide ingot. On the one hand, efficiency and quality often restrict each other, and a proper balance point needs to be found between the two; on the other hand, since the silicon carbide ingot is both hard and fragile, ensuring that it is efficient and maintains high quality during the cutting process further increases the difficulty of this challenge.

[0086] In the current laser cutting technology, in order to improve the cutting efficiency of the silicon carbide crystal ingot, a multi-focus beam, a flat-top beam or a Bessel beam and other beam technologies are usually used. Although these beams can improve the cutting efficiency to a certain extent, they cannot always ensure the cutting quality because some technical difficulties in the laser cutting technology of the silicon carbide crystal ingot have not been completely overcome, for example, the problem that the range of laser-induced micro-cracks 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 play a role in improving the cutting efficiency, further technical breakthroughs and optimization are still needed to ensure the cutting quality.

[0087] In the face of such challenges, the laser processing scheme proposed in the present 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, as discussed in detail above. In addition, the focused linear beam also has a larger spot size along the Y-axis direction compared with the focused Gaussian beam, which allows the spacing between adjacent laser processing lines to be increased, thereby significantly improving the cutting efficiency, that is, the slicing efficiency. Therefore, the efficiency and quality of the silicon carbide crystal ingot processing are improved.

[0088] Therefore, in the laser processing scheme of the present application, the linear beam is used for cutting the silicon carbide crystal ingot, which not only reduces the roughness on the surface of the silicon carbide wafer, thereby improving the quality of the silicon carbide wafer, but also improves the cutting efficiency.

[0089] The above is a description from the perspective of the linear beam as to why the laser processing scheme of the present application can improve the quality of the silicon carbide wafer. The selection of the light source will be described below.

[0090] In order to more effectively control the growth area of the micro-cracks, a specific light source can be selected, for example, the type of laser 110 is selected as a femtosecond laser. The heat-affected zone generated by the femtosecond laser when processing the silicon carbide crystal ingot 190 is small, so outside the laser action area, micro-cracks are almost not formed, thereby accurately controlling the growth of micro-cracks.

[0091] The femtosecond laser includes the following laser parameters: a repetition frequency of 0 to 2 MHz, an average power of 0 to 20 W and a pulse width of 50 fs to 10 ps. When 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.

[0092] Since the pulse width (e.g., 300 fs) of 190 fs to 350 fs is less than the time (1 ps to 100 ps) of lattice vibration, the energy deposition of a single pulse ends before the lattice vibration, thereby greatly reducing the generation of thermal effects. In addition, the repetition frequency (e.g., 100 KHz) of 50 KHz to 500 KHz cooperates with the preset cutting speed (e.g., 25 mm / s) of 15 mm / s to 50 mm / s, which can also greatly reduce the thermal effects caused by the accumulation of multiple pulses. The reduction of thermal effects means that the growth of microcracks can be precisely controlled.

[0093] When cutting the silicon carbide ingot 190, the spacing between adjacent laser processing lines is also considered due to the thermal diffusion area caused by the femtosecond laser pulses generated by the femtosecond laser. The spacing between adjacent laser processing lines is greater than the size of the thermal diffusion area caused by the femtosecond laser pulses, thereby reducing the superposition effect of the thermal diffusion area, and thus precisely controlling the growth of microcracks. As shown in Figure 8 , the spacing d between adjacent laser processing lines 210 is 20 μm to 50 μm, preferably, the spacing d between adjacent laser processing lines 210 is 30 μm.

[0094] When the focused linear beam moves on the silicon carbide ingot 190 at the preset cutting path and the preset cutting speed, the inside 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 the separation of the silicon carbide wafer, and cooperates with the subsequent auxiliary wafering process to successfully cut the silicon carbide wafer from the silicon carbide ingot 190, obtaining a silicon carbide wafer as shown in Figure 9 and 10 .

[0095] Figure 10 The surface morphology of the silicon carbide wafer is shown; Figure 9 The roughness of the silicon carbide wafer is shown in the form of a color image. In the color image, the height difference of the wafer surface is generally represented by different color markers. The more the number of different color markers, the greater the height difference of the wafer surface, that is, the more uneven the surface.

[0096] In Figure 9 , the number of markers M red and markers M blue is not large, indicating that the surface of the silicon carbide wafer is relatively flat, that is, the surface roughness is good.

[0097] In addition, when the focused linear light beam moves on the silicon carbide crystal ingot 190, the focused linear light beam can not only modify the cutting path being traveled, but also has a pre-modification effect on the adjacent cutting path perpendicular to the cutting path being traveled, which makes the growth of micro-cracks more uniform and controllable, thereby reducing the difficulty of the subsequent cleaving process, and further improving the quality of the silicon carbide wafer.

[0098] Therefore, in the laser processing scheme of the utility model, the femtosecond laser with preset laser parameters is adopted, and the silicon carbide crystal ingot is cut in combination with the preset cutting speed and the spacing between the laser processing lines, which can also reduce the roughness generated on the surface of the silicon carbide wafer, thereby improving the quality of the silicon carbide wafer.

[0099] In summary, whether linear light spot or femtosecond laser is adopted, the micro-cracks are concentrated on the cutting path as much as possible, so that the micro-cracks will not expand to the surrounding due to the heat diffusion of the laser, thereby accurately controlling the growth of the micro-cracks.

[0100] In the utility model, the laser light field is regulated and controlled through the optical shaping element, so that the laser loads preset information after passing through the optical shaping element, and a linear light beam is obtained, and then the linear light beam is focused in the silicon carbide crystal ingot through the condensing optical element to cut the silicon carbide crystal ingot. Through the angle control (i.e. collimation) of the linear light beam, power control and light field regulation, the micro-cracks in the silicon carbide crystal ingot are stably generated, and in cooperation with the subsequent auxiliary cleaving process, a high-quality silicon carbide wafer is obtained.

[0101] The device embodiment of the utility model is described in detail above, and the method embodiment of the utility model is described in detail below. Figures 1 to 10 Figure 11 The device embodiment of the utility model is described in detail above, and the method embodiment of the utility model is described in detail below.

[0102] Figure 11 It is a flowchart of the cutting method of the silicon carbide crystal ingot provided by an embodiment of the utility model. 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 previous device embodiment. The cutting method includes the following contents.

[0103] S1110: control the laser processing device to output the focused linear light beam with preset laser parameters.

[0104] The laser processing device includes the elements shown in the device embodiment. Figure 1 or Figure 2 The controller controls the laser to emit a Gaussian light beam with preset laser parameters, and the Gaussian light beam is shaped into a linear light beam with preset laser parameters after being transmitted to the optical shaping element. Then, the linear light beam is focused through the condensing optical element to obtain the focused linear light beam.​

[0105] 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.

[0106] S1120: controlling the focused linear light beam to move on the silicon carbide crystal ingot at a preset cutting path and a preset cutting speed, and modifying the inside of the silicon carbide crystal ingot to complete the cutting of the silicon carbide crystal ingot.

[0107] The controller controls the scanning mechanism to make the focused linear light beam move on the silicon carbide crystal ingot at a preset cutting path and a preset cutting speed, and modify the inside of the silicon carbide crystal ingot in the process of moving of the focused linear light beam to complete the cutting of the silicon carbide crystal ingot.

[0108] The distance 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.

[0109] Compared with the focused Gaussian light beam, the focused linear light beam has a small spot size in the direction of the optical axis and a large spot size in the first direction perpendicular to the preset cutting path, and the direction of the optical axis is perpendicular to the first direction.

[0110] In the cutting scheme of the silicon carbide crystal ingot, the controller controls the laser processing device to output the focused linear light beam with preset laser parameters, and controls the focused linear light beam to move on the silicon carbide crystal ingot at a preset cutting path and a preset cutting speed, and modify the inside of the silicon carbide crystal ingot to complete the cutting of the silicon carbide crystal ingot. Compared with the focused Gaussian light beam, the focused linear light beam has a small spot size in the direction of the optical axis, which means that the focused linear light beam has a shallow depth of action in the inside of the silicon carbide crystal ingot, thereby reducing the length of the growth area of the micro-cracks generated in the processing process in the direction of the optical axis, and further reducing the roughness generated on the surface of the silicon carbide wafer, thereby improving the quality of the silicon carbide wafer.

[0111] The method embodiment of the utility model is described in detail above Figure 11 The system embodiment of the utility model is described in detail below Figure 12 It should be understood that the description of the method embodiment corresponds to the description of the system embodiment, and therefore, the parts not described in detail can be referred to the method embodiment.

[0112] Figure 12Is the structure diagram of the cutting system of the silicon carbide ingot provided by an embodiment of the utility model. The cutting system 1200 can include: a first control module 1210 and a second control module 1220. The modules are introduced in detail below.

[0113] The first control module 1210 is used for controlling the laser processing device to output the focused linear light beam with the preset laser parameter.

[0114] The second control module 1220 is used for controlling the focused linear light beam to move on the silicon carbide ingot at the preset cutting path and the preset cutting speed, and modify the inside of the silicon carbide ingot, so as to complete the cutting of the silicon carbide ingot.

[0115] Figure 13 Is the block diagram of the laser processing system provided by an embodiment of the utility model. The laser processing system 1300 can be a computing device with computing function, for example. The laser processing system 1300 can include a memory 1310 and a processor 1320 (which can be understood as the controller 109 described above). The memory 1310 can be used for storing executable codes. The processor 1320 can be used for executing the executable codes stored in the memory 1310 to realize the steps in the various methods described above. In some embodiments, the laser processing system 1300 can also include a network interface 1330, and the data exchange between the processor 1320 and the external device can be realized through the network interface 1330.

[0116] In the above embodiments, all or part can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or part can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions according to the embodiments of the present application are generated. 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 one website, computer, server or data center to another website, computer, server or data center through wired (such as coaxial cable, optical fiber, digital subscriber line (Digital Subscriber Line, DSL)) or wireless (such as infrared, wireless, microwave, etc.) mode. The computer-readable storage medium can be any available medium that the computer can access or a data storage device such as a server, data center, etc. integrated with one or more available media. The available media can be magnetic media (such as floppy disk, hard disk, magnetic tape), optical media (such as digital video disc (Digital Video Disc, DVD)), or semiconductor media (such as solid state disk (Solid State Disk, SSD)) and the like.

[0117] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments of the present application can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0118] In the several embodiments provided by the present application, it should be understood that the disclosed system, device and method can be implemented by other ways. For example, the device embodiments described above are only schematic, for example, the division of units is only a logical function division, and other division manners can be used in actual implementation, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0119] The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may also be distributed to multiple network units. Part or all of the units can be selected to achieve the purpose of the embodiment of the present application according to actual needs.

[0120] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0121] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited to this. Any skilled person in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A laser processing apparatus characterized by comprising: The application relates to a laser cutting device for cutting a silicon carbide ingot, comprising: a laser for emitting a Gaussian beam with 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 cutting the silicon carbide ingot with the focused linear beam at a preset cutting path and a preset cutting speed, wherein the focused linear beam has a small spot size in the direction of an optical axis compared with the focused Gaussian beam.

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

3. The laser processing apparatus according to claim 1, characterized by The beam shaping element comprises a diffractive optical element or a spatial light modulator.

4. The laser processing apparatus according to any one of claims 1 to 3, characterized by The application further relates to a laser cutting device for cutting a silicon carbide ingot, further comprising: a controller for controlling the laser to emit the Gaussian beam with the preset laser parameters and controlling the scanning mechanism to make the focused linear beam cut the silicon carbide ingot at the preset cutting path and the preset cutting speed.

5. The laser processing apparatus according to any one of claims 1 to 3, characterized by The application further relates to a laser cutting device for cutting a silicon carbide ingot, wherein the scanning mechanism comprises a condensing optical element for focusing the linear beam to obtain the focused linear beam and a three-axis displacement table for carrying the silicon carbide ingot, and the controller controls the three-axis displacement table to move so that the focused linear beam moves on the silicon carbide ingot at the preset cutting path and the preset cutting speed. The application further relates to a laser cutting device for cutting a silicon carbide ingot, wherein the scanning mechanism comprises a condensing optical element for focusing the linear beam to obtain the focused linear beam and a galvanometer group, and the controller controls the deflection angle of the galvanometer group so that the focused linear beam moves on the silicon carbide ingot at the preset cutting path and the preset cutting speed.

6. The laser processing apparatus according to any one of claims 1 to 3, characterized by The preset cutting speed is 15 mm / s to 50 mm / s, and the interval between adjacent laser processing lines in the preset cutting path is 20 mu m to 50 mu m. The preset cutting speed is 25 mm / s, and the interval between adjacent laser processing lines in the preset cutting path is 30 mu m.

7. The laser processing apparatus according to any one of claims 1 to 3, characterized by 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.

8. The laser processing apparatus according to claim 7, characterized by The preset laser parameters comprise a repetition frequency of 100 KHz, an average power of 1 W, and a pulse width of 300 fs.

9. The laser processing apparatus according to any one of claims 1 to 3, characterized by, ​ 10. The laser processing apparatus according to claim 9, wherein ​

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