Silicon carbide substrate and preparation method thereof

Abstract

The invention provides a silicon carbide substrate and a silicon carbide substrate preparation method, the silicon carbide substrate is internally provided with a modification layer distributed between a carbon surface and a silicon surface, the modification layer comprises one or more intermediate layers, the plurality of intermediate layers are sequentially arranged along the vertical direction of the carbon surface, the pattern of the orthographic projection of the intermediate layer on the plane where the carbon surface is located is an intermediate projection, and a peripheral area surrounding the middle projection is formed between the outline of the middle projection and the edge of the carbon surface. The preparation method of the silicon carbide substrate comprises the following steps: adjusting the acting position of a modified device to a processing surface domain in the silicon carbide substrate, so that the acting position falls in one middle surface domain of the processing surface domain at least once or falls in a plurality of middle surface domains of the processing surface domain for multiple times; and driving the silicon carbide substrate to move parallel to the carbon surface relative to the modified device, so that the action position generates a plurality of modified points in one of the middle surface regions in the step A, or generates a plurality of modified points in the plurality of middle surface regions in the step A respectively.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device production, and particularly relates to a silicon carbide substrate and a method for preparing the silicon carbide substrate. Background Art

[0002] The silicon carbide substrate is an important component for preparing various semiconductor devices. The silicon carbide substrate will undergo bending deformation due to processes such as epitaxy and etching, thereby affecting the performance of semiconductor devices. The bent silicon carbide substrate is in a bowl shape or an inverted bowl shape. Usually, the surface shape state of the silicon carbide substrate is measured by BOW (bending degree). The absolute value of BOW represents the bending degree of the silicon carbide substrate, and the positive or negative value of the BOW value represents the bending direction of the silicon carbide substrate. Currently, the shaping means for silicon carbide substrates in the industry include back thinning and high-temperature annealing. Back thinning can only perform negative shaping of the curvature for a positively bent silicon carbide substrate and cannot perform positive shaping of the curvature for a negatively bent silicon carbide substrate. High-temperature annealing causes lattice relaxation and rearrangement inside the silicon carbide substrate, but it will be accompanied by obvious movement of doped atoms, thereby affecting the product performance. Summary of the Invention

[0003] In view of this, the present invention provides a silicon carbide substrate and a method for preparing the silicon carbide substrate that are compatible with positive curvature change shaping and negative curvature change shaping.

[0004] The silicon carbide substrate of the present invention includes a carbon surface and a silicon surface arranged opposite to each other, and has a modified layer distributed between the carbon surface and the silicon surface inside. The modified layer includes one or more intermediate layers. The multiple intermediate layers are arranged in sequence along the vertical direction of the carbon surface. The figure of the intermediate layer projected orthographically onto the plane where the carbon surface is located is the intermediate projection. An outer region surrounding the intermediate projection is formed between the contour of the intermediate projection and the edge of the carbon surface.

[0005] With such a setting, the silicon carbide substrate of the present invention is compatible with positive and negative curvature change shaping modes. During the epitaxy of the silicon carbide substrate and subsequent device production, the surface shape state and curvature change trend of the silicon carbide substrate can be adjusted by removing material from the back of the carbon surface of the silicon carbide substrate. Under the action of the intermediate layer and simply receiving the treatment of back material removal, the silicon carbide substrate shows a surface shape state with a negative curvature. Since the intermediate layer is thinned synchronously with the back material removal, during the period when the intermediate layer is gradually thinned and not completely removed, the role of the intermediate layer in promoting the silicon carbide substrate to present a negative curvature surface shape gradually weakens, and the surface shape of the silicon carbide substrate thus shows a positive curvature change. After the intermediate layer is completely removed, the silicon carbide substrate shows a negative curvature change as the back material removal continues. By simply adjusting the thickness of the back material removal, the curvature change trend of the silicon carbide substrate can be selectively controlled. By determining an appropriate back material removal thickness, the silicon carbide substrate can achieve positive curvature change shaping or negative curvature change shaping.

[0006] In some embodiments, the modified layer further includes at least one peripheral layer. The pattern of the peripheral layer projected orthogonally onto the plane where the carbon surface is located is the peripheral projection. The peripheral projection is located within the peripheral region and surrounds the middle projection. Along the vertical direction of the carbon surface, the middle layer and the peripheral layer are arranged in a staggered manner.

[0007] With such an arrangement, the silicon carbide substrate has deformation trends in different bending directions under the action of the middle layer and the peripheral layer respectively. During the epitaxy of the silicon carbide substrate and subsequent device production, the back material of the carbon surface of the silicon carbide substrate can be removed to adjust the surface shape state and the curvature change trend of the silicon carbide substrate. The distances from the middle layer and the peripheral layer to the carbon surface are set differently. Therefore, by adjusting the removed material thickness, the distribution and the proportion of the remaining middle layer and the remaining peripheral layer in the silicon carbide substrate can be changed, so as to adjust the stress magnitudes acting on the inside of the silicon carbide substrate by the middle layer and the peripheral layer respectively, and selectively change the deformation direction and the deformation amplitude of the silicon carbide substrate, so that the silicon carbide substrate is compatible with the positive and negative curvature shaping.

[0008] In some embodiments, the modified layer forms a plurality of modified layer groups arranged repeatedly along the vertical direction of the carbon surface. Each modified layer group includes at least one middle layer and at least one peripheral layer.

[0009] In some embodiments, the minimum number of the modified layer groups is 2 groups and the maximum number is 5 groups. In each modified layer group, the minimum number of the modified layers is 2 layers and the maximum number is 16 layers.

[0010] In some embodiments, the middle layer and the peripheral layer are arranged alternately layer by layer along the vertical direction of the carbon surface; or, the middle layer and the peripheral layer are arranged alternately in groups along the vertical direction of the carbon surface.

[0011] In some embodiments, the shape of the middle projection includes a circle and a polygon. The outer contour shape of the peripheral projection includes a circle and a polygon. The inner edge shape of the peripheral projection includes a circle and a polygon.

[0012] In some embodiments, the patterns of the modified layer projected orthogonally onto the plane where the carbon surface is located are all centrosymmetric figures, and the symmetry centers of the centrosymmetric figures are all located on the axis of the silicon carbide substrate.

[0013] In some embodiments, along the vertical direction of the carbon surface, the distance between any two adjacent modified layers is not less than 5 and not more than 50 .

[0014] In some embodiments, there are point-like modified points scattered within the area range of the modified layer. The distance between any two modified points is not less than 100 and not more than 1000 , and within each modified layer, the modified points are arranged in an array, or in a concentric circle, or in a radial spoke pattern.

[0015] In some embodiments, the distance between the modification layer closest to the carbon surface and the carbon surface is , and the distance between the modification layer farthest from the carbon surface and the carbon surface is , 10 ≤ ≤100 , 50 ≤ ≤250 .

[0016] In some embodiments, the maximum radial dimension of the intermediate layer is , the minimum radial dimension of the inner edge of the outer layer is , the maximum radial dimension of the outer edge of the outer layer is , the outer peripheral surface diameter of the silicon carbide substrate is , 0.1 ≤ ≤0.8, 0.2 ≤ ≤0.5, 0.2 ≤ ≤0.8.

[0017] The method for preparing a silicon carbide substrate according to the present invention includes the following steps:

[0018] Step A, adjust the action position of the modification device to the processing area in the silicon carbide substrate, so that the action position falls within at least one intermediate area of the processing area, or falls within multiple intermediate areas of the processing area respectively for multiple times;

[0019] Step B, drive the silicon carbide substrate to move relative to the modification device parallel to the carbon surface, so that multiple modified points are generated within one of the intermediate areas in Step A, or multiple modified points are generated within multiple intermediate areas in Step A respectively;

[0020] The processing area is located between the carbon surface and the silicon surface. The pattern of the intermediate area projected orthogonally onto the carbon surface is the intermediate projection. An outer area surrounding the intermediate projection is formed between the contour of the intermediate projection and the edge of the carbon surface. Multiple intermediate areas are arranged in sequence along the vertical direction of the carbon surface.

[0021] The method for preparing a silicon carbide substrate according to the present invention can improve the yield of the silicon carbide substrate and avoid obvious movement of doped atoms in the substrate.

[0022] In some embodiments, the method for preparing a silicon carbide substrate further includes the following steps:

[0023] Step C, transfer the action position of the modification device along the vertical direction of the carbon surface, so that the action position falls within at least one outer area of the processing area, or falls within multiple outer areas of the processing area respectively for multiple times;

[0024] Step D: Drive the silicon carbide substrate to move relative to the modification device parallel to the carbon surface, so that multiple modification points are generated in one of the peripheral surface regions in Step C, or multiple modification points are respectively generated in multiple peripheral surface regions in Step C;

[0025] The pattern of the peripheral surface region projected orthogonally onto the carbon surface is the peripheral projection. The peripheral projection is located within the peripheral region and surrounds the middle projection. Along the vertical direction of the carbon surface, multiple peripheral surface regions are arranged in sequence, and the middle surface region and the peripheral surface regions are misaligned.

[0026] In some embodiments, in Step A, making the action position fall within at least one of the middle surface regions of the processing surface region, or falling within multiple middle surface regions of the processing surface region respectively multiple times includes:

[0027] Step A1: Control the action position of the modification device to move closer to the carbon surface, and transfer from one of the peripheral surface regions to one of the middle surface regions;

[0028] Step A2: Control the action position of the modification device to migrate closer to the carbon surface, and migrate from one of the middle surface regions to another middle surface region;

[0029] In Step C, transferring the action position of the modification device along the vertical direction of the carbon surface includes:

[0030] Step C1: Control the action position of the modification device to move closer to the carbon surface, and transfer from one of the middle surface regions to one of the peripheral surface regions;

[0031] Step C2: Control the action position of the modification device to migrate closer to the carbon surface, and migrate from one of the peripheral surface regions to another peripheral surface region.

[0032] In some embodiments, Step A1 includes: Along the direction perpendicular to the carbon surface, the action position transfers a distance and reaches an adjacent middle surface region, 5 ≤ ≤ 50 ;

[0033] Step A2 includes: Along the direction perpendicular to the carbon surface, the action position migrates a distance and reaches another adjacent middle surface region;

[0034] Step C1 includes: Along the direction perpendicular to the carbon surface, the action position transfers a distance and reaches an adjacent peripheral surface region;

[0035] Step C2 includes: Along the direction perpendicular to the carbon surface, the action position migrates from one of the peripheral surface regions reach another adjacent peripheral surface region after a certain distance.

[0036] In some embodiments, steps A, B, C, and D are executed repeatedly for several times.

[0037] In some embodiments, the method for preparing a silicon carbide substrate further includes:

[0038] Step E1: First, adjust the action position of the modified device to the first processing surface region within the silicon carbide substrate. The first processing surface region is the one that is the farthest from the carbon surface among multiple processing surface regions, and the distance from the first processing surface region to the carbon surface is , 50 ≤ ≤ 250 ;

[0039] Step E2: Drive the silicon carbide substrate to move parallel to the carbon surface relative to the modified device, and first generate multiple modified points within the first processing surface region in step E1 at the action position, so that the first modified layer is formed in the first processing surface region relative to other processing surface regions first.

[0040] In some embodiments, the method for preparing a silicon carbide substrate further includes the following steps:

[0041] Step F: Fix the silicon carbide substrate on the modified processing stage, with the silicon surface facing the modified processing stage and the carbon surface facing away from the modified processing stage;

[0042] Step B includes: Step B1: Drive the modified processing stage to move relative to the modified device along a direction parallel to the carbon surface;

[0043] Step D includes: Step D1: Drive the modified processing stage to move relative to the modified device along a direction parallel to the carbon surface.

[0044] In some embodiments, the method for preparing a silicon carbide substrate further includes:

[0045] Step G: The modified processing stage applies an adsorption force to the silicon surface to make the silicon surface fit with the plane of the modified processing stage.

[0046] In some embodiments, step B includes:

[0047] Step B2: Drive the silicon carbide substrate and the modified device to make relative intermittent movements along a direction parallel to the carbon surface. The step distance of the relative intermittent movement is , 100 ≤ ≤ 1000 ;

[0048] Step D includes:

[0049] Step D2: Drive the silicon carbide substrate and the modified device to move relatively intermittently in a direction parallel to the carbon plane, and the step distance of the relative intermittent movement is , 100 ≤ ≤ 1000 .

[0050] In some embodiments, the intermediate plane region and the multiple modified points generated in the intermediate plane region form an intermediate layer, and the multiple modified points are arranged in a radial spoke pattern within the intermediate plane region; Step B further includes:

[0051] Step B3: Drive the silicon carbide substrate to translate relative to the modified device along the first radial direction of the carbon plane, so that the acting position forms a first line segment trajectory passing through the symmetry center of the intermediate plane region, and the first line segment trajectory equally divides the intermediate plane region;

[0052] Step B4: With the axis of the silicon carbide substrate as the rotation center, drive the silicon carbide substrate to rotate a preset angular range, and keep the orientation of the carbon plane unchanged;

[0053] Step B5: Drive the silicon carbide substrate to translate relative to the modified device along the second radial direction of the carbon plane, so that the acting position forms a second line segment trajectory passing through the symmetry center of the intermediate plane region, and the second line segment trajectory equally divides the intermediate plane region.

[0054] In some embodiments, the peripheral plane region and the multiple modified points generated in the peripheral plane region form a peripheral layer, and the multiple modified points are arranged in a radial spoke pattern within the peripheral plane region; Step D further includes:

[0055] Step D3: Drive the silicon carbide substrate to translate relative to the modified device along the third radial direction of the carbon plane, so that the acting position forms a third line segment trajectory passing through the symmetry center of the peripheral plane region, and the third line segment trajectory equally divides the peripheral plane region;

[0056] Step D4: With the axis of the silicon carbide substrate as the rotation center, drive the silicon carbide substrate to rotate a preset angular range, and keep the orientation of the carbon plane unchanged;

[0057] Step D5: Drive the silicon carbide substrate to translate relative to the modified device along the fourth radial direction of the carbon plane, so that the acting position forms a fourth line segment trajectory passing through the symmetry center of the peripheral plane region, and the fourth line segment trajectory equally divides the peripheral plane region.

[0058] In some embodiments, the intermediate plane region and the multiple modified points generated in the intermediate plane region form an intermediate layer, and the multiple modified points are arranged in concentric circles within the intermediate plane region; Step B further includes:

[0059] Step B6: Drive the silicon carbide substrate to rotate around the axis for at least one week, so that the acting position forms a first circular ring trajectory around the axis of the silicon carbide substrate;

[0060] Step B7: Drive the silicon carbide substrate to displace in a direction parallel to the carbon surface to change the distance from the acting position to the axis of the silicon carbide substrate;

[0061] Step B8: Drive the silicon carbide substrate to rotate around the axis for at least one week so that the acting position forms a second circular ring trajectory around the axis of the silicon carbide substrate.

[0062] In some embodiments, the peripheral surface region and the multiple modified points generated in the peripheral surface region form a peripheral layer, and the multiple modified points are arranged in concentric circles within the peripheral surface region; Step D further includes:

[0063] Step D6: Drive the silicon carbide substrate to rotate around the axis for at least one week so that the acting position forms a third circular ring trajectory around the axis of the silicon carbide substrate;

[0064] Step D7: Drive the silicon carbide substrate to displace in a direction parallel to the carbon surface to change the distance from the acting position to the axis of the silicon carbide substrate;

[0065] Step D8: Drive the silicon carbide substrate to rotate around the axis for at least one week so that the acting position forms a fourth circular ring trajectory around the axis of the silicon carbide substrate.

[0066] In some embodiments, the modification device is a laser generator and the acting position is the laser focus;

[0067] Step A includes: Step A3: Adjust the laser focus of the laser generator so that the laser focus falls on the middle surface region inside the silicon carbide substrate;

[0068] Step C includes: Step C3: Adjust the laser focus of the laser generator so that the laser focus transfers from one middle surface region to one peripheral surface region along the vertical direction of the carbon surface.

[0069] Compared with the prior art, regardless of whether the silicon carbide substrate is in a positive curvature surface type or a negative curvature surface type in the initial state, an ideal shaping effect can be obtained through back material removal. Only by adjusting the material removal thickness during back material removal can the silicon carbide substrate be deformed positively or negatively. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a cross-sectional view of the silicon carbide substrate according to Embodiment 1 of the present invention;

[0071] Figure 2 It is a schematic diagram of the intermediate layer of the silicon carbide substrate according to Embodiment 2 of the present invention;

[0072] Figure 3 It is a schematic diagram of the intermediate layer of the silicon carbide substrate according to Embodiment 3 of the present invention;

[0073] Figure 4Schematic diagram of the intermediate layer of the silicon carbide substrate according to the fourth embodiment of the present invention;

[0074] Figure 5 Schematic diagram of the peripheral layer of the silicon carbide substrate according to the fifth embodiment of the present invention;

[0075] Figure 6 Schematic diagram of the peripheral layer of the silicon carbide substrate according to the sixth embodiment of the present invention;

[0076] Figure 7 First shaping analysis schematic diagram of the silicon carbide substrate of the present invention;

[0077] Figure 8 Second shaping analysis schematic diagram of the silicon carbide substrate of the present invention;

[0078] Figure 9 Third shaping analysis schematic diagram of the silicon carbide substrate of the present invention.

[0079] Reference numerals: 100, silicon carbide substrate; 11, silicon surface; 12, carbon surface; 13, modified layer; 130, modified layer group; 131, intermediate layer; 132, peripheral layer. Detailed implementation manners

[0080] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0081] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0082] The present invention provides a silicon carbide substrate 100 that is compatible with two shaping modes, namely, the positive change of curvature and the negative change of curvature. The present invention also provides a method for preparing the silicon carbide substrate 100 that can obtain the silicon carbide substrate 100 of the present invention. Being compatible with the positive change of curvature and the negative change of curvature means that: it is allowed that the BOW (bending degree) value of the silicon carbide substrate 100 increases to achieve the positive change of curvature, and it is also allowed that the BOW value decreases to achieve the negative change of curvature. Among them, the positive change includes the cases where the BOW value is negative and the numerical value increases, the BOW value changes from negative to positive, and the BOW value is positive and the numerical value increases; the negative change includes the cases where the BOW value is negative and the numerical value decreases, the BOW value changes from positive to negative, and the BOW value is positive and the numerical value decreases.

[0083] Adjusting the surface shape of the silicon carbide substrate 100 is called shaping. Shaping is achieved by removing material from the back of the silicon carbide substrate 100. Different back material removal thicknesses produce different shaping effects. By simply adjusting the material removal thickness of the back material removal, the curvature of the silicon carbide substrate 100 can be changed in the positive or negative direction.

[0084] Refer to Figure 1 , there is a modified layer 13 distributed between the carbon surface 12 and the silicon surface 11 inside the silicon carbide substrate 100 of the present invention. The carbon surface 12 and the silicon surface 11 are respectively two parallel end faces of the silicon carbide substrate 100. The modified layer 13 is a lamellar region inside the silicon carbide substrate 100. The modified layer 13 is parallel to the carbon surface 12 and the silicon surface 11 and has lattice distortion inside. Therefore, the modified layer 13 will exert a stress effect on the entire silicon carbide substrate 100. This stress effect causes the silicon carbide substrate 100 to exhibit a certain degree of bending, and the shape of the modified layer 13 will cause the direction of the stress received by the silicon carbide substrate 100 to change. Therefore, different shapes of the modified layer 13 will make the silicon carbide substrate 100 exhibit different surface shapes.

[0085] In some embodiments, there are point-dispersed modified points within the surface area of the modified layer 13. The means for obtaining the modified layer 13 includes irradiating the inside of the silicon carbide substrate 100 with the laser generated by a laser generator. Through the energy in the laser, lattice distortion occurs at the irradiated position inside the silicon carbide substrate 100, and the irradiated position forms a modified point. By changing the irradiated position, multiple modified points are obtained, and the processing surface area where the multiple modified points are located forms the modified layer 13. Specifically, in order to obtain the lamellar modified layer 13, first, the laser generator needs to be adjusted so that the laser focus falls on the processing surface area inside the silicon carbide substrate 100. The processing surface area is a lamellar area artificially determined inside the silicon carbide substrate 100 in advance. Then, the position of the laser focus is moved within the same processing surface area, so that multiple modified points are obtained within the same processing surface area. After several irradiations, a modified layer 13 is formed in this processing surface area. Optionally, within the surface area of any modified layer 13, the distance between any two adjacent modified points is not less than 100 and not greater than 1000 With such a setting, it is possible to avoid cracks caused by too small a distance between the modified particles in the modified layer 13, and the modification effect of the modified layer 13 can also be ensured.

[0086] It can be understood that in other embodiments, the means of obtaining the modified layer 13 is not limited to irradiating the inside of the silicon carbide substrate 100 with a laser. Any means of obtaining modified particles in the processing area without damaging the structure of the silicon carbide substrate 100 can be used to obtain the modified layer 13.

[0087] In some embodiments, the modified layer 13 includes at least one intermediate layer 131. When the number of intermediate layers 131 is multiple, the multiple intermediate layers 131 are arranged in sequence along the vertical direction of the carbon surface 12, and each intermediate layer 131 is parallel to the carbon surface 12 and the silicon surface 11. The vertical direction of the carbon surface 12 is also the axial direction of the silicon carbide substrate 100. The shape of the intermediate layer 131 is specifically as follows: when the intermediate layer 131 projects orthogonally onto the carbon surface 12 to form an intermediate projection, an outer region is formed between the edge contour of the intermediate projection and the edge of the carbon surface 12, and the intermediate projection is surrounded by the outer region. Optionally, in some embodiments, the modified layer 13 in the silicon carbide substrate 100 is entirely the intermediate layer 131. The number of intermediate layers 131 can be one or multiple, and the shapes and sizes of the multiple intermediate layers 131 can be the same or different. The mechanism of the silicon carbide substrate 100 achieving positive and negative curvature changes is introduced below.

[0088] The silicon carbide substrate 100 shows a surface shape state with a negative curvature (i.e., the BOW value is negative) under the action of only back material removal treatment, and the silicon carbide substrate 100 shows a surface shape state with a negative curvature under the stress of the intermediate layer 131 alone. The greater the thickness of the intermediate layer 131, the more significant the surface shape state with a negative curvature. During the back material removal process, not only the thickness of the silicon carbide substrate 100 itself decreases, but also the thickness of the intermediate layer 131 continuously decreases. Therefore, during the period when the intermediate layer 131 is thinned and not completely removed, the deformation effect of the intermediate layer 131 promoting the silicon carbide substrate 100 to present a negative curvature surface shape gradually weakens. Therefore, the surface shape of the silicon carbide substrate 100 shows a positive curvature change, specifically, the BOW value is negative and gradually increases; after the intermediate layer 131 is completely removed, the silicon carbide substrate 100 is only affected by the back material removal treatment. Therefore, the silicon carbide substrate 100 shows a negative curvature change after the intermediate layer 131 is removed. Therefore, by simply adjusting the material removal thickness of the back material removal, the curvature change trend of the silicon carbide substrate 100 can be controlled.

[0089] In other embodiments, the silicon carbide substrate 100 further includes at least one peripheral layer 132, and the intermediate layer 131 and the peripheral layer 132 are staggered along the vertical direction of the carbon surface 12. When the number of the peripheral layers 132 is multiple, the multiple peripheral layers 132 are arranged in sequence along the vertical direction of the carbon surface 12 and each peripheral layer 132 is parallel to the carbon surface 12 and the silicon surface 11, and the shapes and sizes of the multiple peripheral layers 132 can be the same or different. Specifically, any intermediate layer 131 and any peripheral layer 132 are not at the same height position, and when the cutting plane perpendicular to the axial direction of the silicon carbide substrate 100 continuously moves along the axial direction of the silicon carbide substrate 100, the cutting plane only cuts one intermediate layer 131 or one peripheral layer 132, and does not cut the intermediate layer 131 and the peripheral layer 132 at the same time. The shape of the peripheral layer 132 is as follows: when the peripheral layer 132 is projected onto the carbon surface 12 and forms a peripheral projection, the peripheral projection is located in the peripheral area and surrounds the intermediate projection. The following describes the mechanism by which the present embodiment enables the silicon carbide substrate 100 to accommodate both positive and negative changes in curvature.

[0090] The silicon carbide substrate 100 simply exhibits a surface state with positive curvature under the stress of the outer layer 132. The greater the thickness of the outer layer 132, the more significant the surface state with positive curvature. Therefore, the silicon carbide substrate 100 has deformation tendencies in different bending directions under the action of the intermediate layer 131 and the outer layer 132. Since the distances from the middle layer 131 and the outer layer 132 to the carbon surface 12 and the distances from the middle layer 131 and the outer layer 132 to the silicon surface 11 are set differently, during the back-removal process, the distribution and quantity ratio of the remaining middle layer 131 and the remaining outer layer 132 in the silicon carbide substrate 100 can be changed by adjusting the removal thickness, and the stress magnitudes of the middle layer 131 and the outer layer 132 acting on the silicon carbide substrate 100 can be adjusted respectively, thereby changing the direction and magnitude of the combined force of the modified layer 13 on the silicon carbide substrate 100, thereby selectively changing the deformation direction and deformation amplitude of the silicon carbide substrate 100, and the deformation direction and deformation amplitude of the silicon carbide substrate 100 both belong to the category of the curvature change trend of the silicon carbide substrate 100.

[0091] See also Figure 1, in some embodiments, the modified layer 13 is grouped to form a plurality of modified layer groups 130 arranged repeatedly in the vertical direction of the carbon surface 12. Each modified layer group 130 includes at least one intermediate layer 131 and at least one peripheral layer 132. With such an arrangement, a silicon carbide substrate 100 can be repeatedly shaped by means of back material removal until the final surface profile of the silicon carbide substrate 100 meets the production requirements. For example, during the back material removal process, if the set value of the material removal thickness is incorrect or there is a processing error during back material removal, resulting in a mismatch between the actual material removal thickness and the selected material removal thickness, causing a situation where the intermediate layer 131 or the peripheral layer 132 is thinned incorrectly in the current modified layer group 130 closest to the carbon surface 12, and thus the surface profile correction effect of the silicon carbide substrate 100 is not ideal, the silicon carbide substrate 100 can be continuously subjected to back material removal and the current modified layer group 130 closest to the carbon surface 12 can be removed. Then, the intermediate layer 131 or the peripheral layer 132 of the next modified layer group 130 can be thinned. In other words, setting a plurality of modified layer groups 130 can provide more opportunities for shaping by means of back material removal.

[0092] Optionally, the number of the modified layer groups 130 is at least 2 groups and at most 5 groups. In each modified layer group 130, the number of the modified layers 13 is at least 2 layers and at most 16 layers.

[0093] Refer to Figure 1 , in some embodiments, the intermediate layer 131 and the peripheral layer 132 are arranged alternately layer by layer in the vertical direction of the carbon surface 12; in some embodiments not shown in the figure, the intermediate layer 131 and the peripheral layer 132 are arranged alternately in groups in the vertical direction of the carbon surface 12, that is, several intermediate layers 131 form an intermediate modification group, and several peripheral layers 132 form a peripheral modification group. The intermediate modification group and the peripheral modification group are arranged alternately in the vertical direction of the carbon surface 12. In each group of intermediate modification groups, a plurality of intermediate layers 131 are arranged in sequence in the vertical direction of the carbon surface 12, and in each group of peripheral modification groups, a plurality of peripheral layers 132 are arranged in sequence in the vertical direction of the carbon surface 12. Optionally, whether the intermediate layer 131 and the peripheral layer 132 are arranged alternately layer by layer or alternately in groups, the distance between any two adjacent modified layers 13 is not less than 5 and not greater than 50 . With such an arrangement, it is possible to avoid cracks caused by the interaction between two adjacent modified layers 13 due to too small a distance between the modified layers 13, and it is also possible to ensure that the number of the modified layers 13 is sufficient.

[0094] Furthermore, in some embodiments, the shape of the intermediate projection includes a circle and a polygon. The surface area shape of the intermediate layer 131 can be a circle or a polygon, such as Figures 3 to 4As shown; the outer contour shape and the inner contour shape of the peripheral projection include a circle and a polygon. The inner contour shape and the outer contour shape of the peripheral layer 132 can be a circle or a polygon, such as Figures 5 to 6 As shown. Preferably, the orthographic projection of each modified layer 13 including the intermediate layer 131 and the peripheral layer 132 on the carbon surface 12 is a centrosymmetric figure, and the symmetry centers of the centrosymmetric figures are all located on the axis of the silicon carbide substrate 100. With such a setting, the forces exerted by the intermediate layer 131 and the peripheral layer 132 on the inside of the silicon carbide substrate 100 are symmetrically distributed about the axis of the silicon carbide substrate 100, so that the overall shape of the silicon carbide substrate 100 is closer to a standard of a surface of revolution.

[0095] Furthermore, in some embodiments, within any one modified layer 13, the modified particles are arranged in an array, in concentric circles, or in radial spokes. Figure 2 Schematically shows the intermediate layer 131 with the modified particles arranged in concentric circles, Figure 3 and Figure 4 Schematically shows the intermediate layer 131 with the modified particles arranged in radial spokes. The array arrangement specifically means that: a plurality of modified particles are arranged in rows and columns and the rows and columns are perpendicular to each other; the concentric circle arrangement specifically means that: a plurality of modified particles are respectively located on a plurality of concentric circular rings, and the plurality of concentric circular rings are centered on the axis of the silicon carbide substrate 100; the radial spoke arrangement specifically means that: a plurality of modified particles are respectively located on a plurality of radial spoke line segments, and the plurality of radial spoke line segments are rotationally symmetrically distributed with the axis of the silicon carbide substrate 100 as the center of symmetry.

[0096] Furthermore, in some embodiments, the distance between the modified layer 13 closest to the carbon surface 12 and the carbon surface 12 is and the distance between the modified layer 13 farthest from the carbon surface 12 and the carbon surface 12 is , where 10 ≤ ≤100 , 50 ≤ ≤250 . With such a setting, the distance between the modified layer 13 closest to the carbon surface 12 and the carbon surface 12 is appropriate, and the distance between the modified layer 13 farthest from the carbon surface 12 and the carbon surface 12 is appropriate. Specifically, if the distance between the modified layer 13 closest to the carbon surface 12 and the carbon surface 12 is too small, the modified layer 13 closest to the carbon surface 12 may crack. If it is too large, the number of modified layers 13 in the silicon carbide substrate 100 will be reduced; if the distance between the modified layer 13 farthest from the carbon surface 12 and the carbon surface 12 is too small, the number of modified layers 13 in the silicon carbide substrate 100 will be reduced; if If it is too large, the stress exerted by the modified layer 13 on the silicon carbide substrate 100 is weak or even disappears, making it difficult to exert the influence of the modified layer 13 on the surface profile.

[0097] Further, in some embodiments, the maximum radial dimension of the intermediate layer 131 is and the minimum radial dimension of the inner edge of the peripheral layer 132 is and the maximum radial dimension of the outer edge of the peripheral layer 132 is and the diameter of the outer peripheral surface of the silicon carbide substrate 100 is 0.1 ≤ ≤ 0.8, 0.2 ≤ ≤ 0.5, 0.2 ≤ ≤ 0.8. Among them, the maximum radial dimension of the intermediate layer 131 refers to the diameter of the circumscribed circle of the intermediate layer 131, and the minimum radial dimension of the inner edge of the peripheral layer 132 refers to the diameter of the inscribed circle of the inner contour of the peripheral layer 132, and the maximum radial dimension of the outer edge of the peripheral layer 132 refers to the diameter of the circumscribed circle of the outer contour of the peripheral layer 132. With such a setting, the influence of the intermediate layer 131 on the surface profile of the silicon carbide substrate 100 is a negative curvature, and the influence of the peripheral layer 132 on the surface profile of the silicon carbide substrate 100 is a positive curvature. The comparison of the influence effects of the intermediate layer 131 and the peripheral layer 132 on the surface profile of the silicon carbide substrate 100 is significant.

[0098] The following introduces the preparation method of the silicon carbide substrate 100 of the present invention. This method includes the following steps:

[0099] Step A: Adjust the action position of the modification device to the processing area within the silicon carbide substrate 100 so that the action position falls within at least one intermediate area of the processing area in sequence, or falls within multiple intermediate areas of the processing area separately and multiple times;

[0100] Step B: Drive the silicon carbide substrate 100 to move parallel to the carbon surface 12 relative to the modification device so that multiple modification points are generated within one intermediate area in Step A, or multiple modification points are generated within multiple intermediate areas in Step A respectively;

[0101] The processed region is an artificially determined lamellar region located between the carbon surface 12 and the silicon surface 11. The number of processed regions is multiple, and the multiple processed regions are arranged in sequence along the vertical direction of the carbon surface 12. The processed region includes at least one or more intermediate regions, and the intermediate regions are used to form the intermediate layer 131. In some embodiments, the processed region further includes at least one peripheral region for forming the peripheral layer 132. Along the vertical direction of the carbon surface 12, the multiple peripheral regions are arranged in sequence, and the intermediate region and the peripheral region are arranged in a staggered manner. The intermediate region and the peripheral region are arranged alternately layer by layer along the vertical direction of the carbon surface 12, or the intermediate region and the peripheral region are arranged alternately in groups along the vertical direction of the carbon surface 12. The figure of the intermediate region projected orthogonally onto the carbon surface 12 is the intermediate projection, and an outer peripheral region surrounding the intermediate projection is formed between the contour of the intermediate projection and the edge of the carbon surface 12. The multiple intermediate regions are arranged in sequence along the vertical direction of the carbon surface 12. The intermediate region and the multiple modified points within the intermediate region form the modified layer 13, and the peripheral region and the multiple modified points within the peripheral region form the peripheral layer 132.

[0102] Specifically, the modification device can be a laser generator. The action position of the modification device is the laser focus of the laser generator. The laser enters the silicon carbide substrate 100 from the carbon surface 12 of the silicon carbide substrate 100, and the position where the processed region is affected by the laser focus forms modified points. The modified points and the processed region form the modified layer. The processed region defines the distribution range of the modified points in the plane where the processed region is located, that is, the modified points will not exceed the processed region. Specifically, the modified points located in the intermediate region do not exceed the outer contour of the intermediate region, and the modified points located in the peripheral region do not exceed the inner contour and the outer contour of the peripheral region.

[0103] In step A, when the action position falls on one of the intermediate regions of the processed region once, after step B is executed, one intermediate region where the action position has fallen forms an intermediate layer 131; when the action position falls on multiple intermediate regions of the processed region respectively multiple times, after step B is executed, the multiple intermediate regions where the action position has fallen respectively form multiple intermediate layers 131. Step B aims to make the action position make short stops at multiple stop positions within the intermediate region respectively. These stop positions finally form multiple modified points respectively. The action position moves from one stop position to another as the silicon carbide substrate 100 moves relative to the modification device parallel to the carbon surface 12. The multiple stop positions within the intermediate region can specifically be arranged in an array, in a concentric circle arrangement, or in a radial spoke arrangement. It should be noted that if the number of intermediate layers 131 is multiple, only when the action position makes short stops at all the stop positions within one intermediate region, then the action position migrates from the current intermediate region and falls on another intermediate region, that is, only after one intermediate layer 131 is formed, will the action position migrate to another intermediate region to process a new intermediate layer 131.

[0104] In some embodiments, the method for preparing the silicon carbide substrate 100 further includes the following steps:

[0105] Step C: Transfer the action position of the modification device in the vertical direction of the carbon surface 12 so that the action position falls within at least one of the peripheral surface regions of the processing surface region, or falls within a plurality of peripheral surface regions of the processing surface region respectively multiple times;

[0106] Step D: Drive the silicon carbide substrate 100 to move relative to the modification device parallel to the carbon surface 12 so that multiple modification points are generated within one of the peripheral surface regions in Step C, or multiple modification points are respectively generated within a plurality of peripheral surface regions in Step C;

[0107] The pattern of the peripheral surface region projected orthogonally onto the carbon surface 12 is the peripheral projection, and the peripheral projection is located within the peripheral region and surrounds the intermediate projection.

[0108] In Step C, when the action position falls within one of the peripheral surface regions of the processing surface region once, after Step D is executed, one peripheral surface region where the action position has fallen forms one peripheral layer 132; when the action position falls within a plurality of peripheral surface regions of the processing surface region respectively multiple times, after Step D is executed, a plurality of peripheral surface regions where the action position has fallen respectively form a plurality of peripheral layers 132. Step C is intended to make the action position make short stops at multiple stop positions within the peripheral surface region respectively, and these stop positions finally respectively form multiple modification points. The action position moves from one stop position to another as the silicon carbide substrate 100 moves relative to the modification device parallel to the carbon surface 12. The multiple stop positions within the peripheral surface region may specifically be arranged in an array, in concentric circles, or in a radial spoke arrangement. It should be noted that if the number of peripheral layers 132 is multiple, only when the action position makes short stops at all the stop positions within one peripheral surface region, then the action position migrates from the current peripheral surface region and falls within another peripheral surface region, that is, only after one peripheral layer 132 is formed, will the action position migrate to another peripheral surface region to process a new peripheral layer 132.

[0109] In some embodiments, in Step A, making the action position fall within at least one of the intermediate surface regions of the processing surface region, or fall within a plurality of intermediate surface regions of the processing surface region respectively multiple times includes:

[0110] Step A1: Control the action position of the modification device to make a transfer movement close to the carbon surface 12, and transfer from one of the peripheral surface regions to one of the intermediate surface regions;

[0111] Step A2: Control the action position of the modification device to make a migration movement close to the carbon surface 12, and migrate from one of the intermediate surface regions to another intermediate surface region;

[0112] In step C, the operation position of the modification device is transferred in the vertical direction of the carbon surface 12, including:

[0113] Step C1: Control the operation position of the modification device to move closer to the carbon surface 12 and transfer from one intermediate surface region to one peripheral surface region;

[0114] Step C2: Control the operation position of the modification device to move closer to the carbon surface 12 and migrate from one peripheral surface region to another peripheral surface region.

[0115] The switching of the operation position between multiple intermediate surface regions and between multiple peripheral surface regions both belongs to the migration activity of the operation position of the modification device; the switching of the operation position from the intermediate surface region to the peripheral surface region and from the peripheral surface region to the intermediate surface region belongs to the transfer activity of the operation position of the modification device. Steps A1 and A2, steps C1 and C2 are all intended to define that: regardless of whether the operation position performs migration activity or transfer activity, the moving direction of the operation position is closer to the carbon surface 12.

[0116] Specifically, step A1 includes: along the direction perpendicular to the carbon surface 12, the operation position is transferred from one peripheral surface region by a distance and reaches an adjacent intermediate surface region, 5 ≤ ≤ 50 ;

[0117] Step A2 includes: along the direction perpendicular to the carbon surface 12, the operation position migrates from one intermediate surface region by a distance and reaches an adjacent other intermediate surface region;

[0118] Step C1 includes: along the direction perpendicular to the carbon surface 12, the operation position is transferred from one intermediate surface region by a distance and reaches an adjacent peripheral surface region;

[0119] Step C2 includes: along the direction perpendicular to the carbon surface 12, the operation position migrates from one peripheral surface region by a distance and reaches an adjacent other peripheral surface region;

[0120] The preparation method of the silicon carbide substrate 100 further includes:

[0121] Step E1: First, adjust the operation position of the modification device to the first processing surface region in the silicon carbide substrate 100. The first processing surface region is the one with the farthest distance from the carbon surface 12 among multiple processing surface regions, and the distance from the first processing surface region to the carbon surface 12 is , 50 ≤ ≤ 250 ;

[0122] Step E2: Drive the silicon carbide substrate 100 to move relative to the modification device parallel to the carbon surface 12, and first generate a plurality of modified points at the action position within the first processing surface area in Step E1, so that the first processing surface area forms a first modified layer 13 relative to other processing surface areas first.

[0123] The first processing surface area is the one that is the farthest from the carbon surface 12 among the plurality of processing surface areas. With such a setting, during the process of processing the modified layer 13, the action position first falls on the first processing surface area that is the farthest from the carbon surface 12. After the modified layer 13 is formed on the processing surface area that is the farthest from the carbon surface 12, the action position moves a distance in the vertical direction of the carbon surface 12 towards the carbon surface 12 so as to reach the processing surface area that is the second farthest from the carbon surface 12, and then the action position continues to move a distance in the vertical direction of the carbon surface 12 towards the carbon surface 12 so as to reach the processing surface area that is the third farthest from the carbon surface 12, and so on. By adopting the transfer method and migration method in which the action position moves upward close to the carbon surface 12, it can be ensured that when processing any modified layer 13, the influence of the laser action on the processing surface areas above the modified surface area being processed is limited.

[0124] In contrast, adopting the transfer and migration method in which the action position moves downward away from the carbon surface 12 has the following defects: The modified layer 13 above the modified surface area being processed will change the laser light path, making it difficult for the laser focus to accurately fall on the current modified surface area being processed.

[0125] In some embodiments, Steps A, B, C, and D are repeatedly executed several times. Thus, a plurality of modified layer groups 130 arranged in sequence in the vertical direction of the carbon surface 12 are obtained.

[0126] In some embodiments, the method for preparing the silicon carbide substrate 100 further includes the following steps:

[0127] Step F: Fix the silicon carbide substrate 100 on the modification processing stage, and make the silicon surface 11 face the modification processing stage and the carbon surface 12 face away from the modification processing stage;

[0128] Step G: The modification processing stage applies an adsorption force to the silicon surface 11 so that the silicon surface 11 fits with the plane of the modification processing stage;

[0129] Step B includes: Step B1: Drive the modification processing stage to move relative to the modification device along a direction parallel to the carbon surface 12;

[0130] Step D includes: Step D1: Drive the modification processing stage to move relative to the modification device along a direction parallel to the carbon surface 12.

[0131] Specifically, a negative pressure suction force of 20 to 100 kPa is applied to the silicon surface 11 by the processing stage. With such a setting, deformation of the silicon carbide substrate 100 can be avoided when irradiating and modifying the silicon carbide substrate 100 with the laser generator, thereby ensuring that the laser focus can accurately fall on each processing area.

[0132] In some embodiments, step B further includes:

[0133] Step B2, driving the silicon carbide substrate 100 and the modification device to make relative intermittent movement in a direction parallel to the carbon surface 12, and the step distance of the relative intermittent movement is , 100 ≤ ≤ 1000 ;

[0134] Step D further includes:

[0135] Step D2, driving the silicon carbide substrate 100 and the modification device to make relative intermittent movement in a direction parallel to the carbon surface 12, and the step distance of the relative intermittent movement is , 100 ≤ ≤ 1000 .

[0136] By making the relative intermittent movement of the silicon carbide substrate 100 and the modification device in a direction parallel to the carbon surface 12, the acting position can make intermittent movement within the processing area. When the acting position stops, a modified point can be formed on the processing area. The intermittent movement can ensure that the modified points are scattered. The step distance of the intermittent movement of the acting position is , equal to the distance between any two adjacent modified points.

[0137] In some embodiments, the intermediate area and multiple modified points generated in the intermediate area form an intermediate layer 131, and the multiple modified points are arranged in a radial spoke pattern within the intermediate area; step B further includes:

[0138] Step B3, driving the silicon carbide substrate 100 to translate relative to the modification device along the first radial direction of the carbon surface 12, so that the acting position forms a first line segment trajectory passing through the center of symmetry of the intermediate area. The first line segment trajectory is perpendicularly intersecting the axis of the silicon carbide substrate 100 and equally divides the intermediate area;

[0139] Step B4, driving the silicon carbide substrate 100 to rotate a preset angular range with the axis of the silicon carbide substrate 100 as the rotation center, and keeping the orientation of the carbon surface 12 unchanged;

[0140] Step B5: Drive the silicon carbide substrate 100 to translate relative to the modification device along the second radial direction of the carbon surface 12, so that the acting position forms a second line segment trajectory passing through the symmetry center of the intermediate plane region. The second line segment trajectory perpendicularly intersects the axis of the silicon carbide substrate 100 and equally divides the intermediate plane region.

[0141] The first line segment trajectory and the second line segment trajectory are respectively two radial spoke line segments, and the intersection point of the two is located on the axis of the silicon carbide substrate 100. It can be understood that in order to form a plurality of modified points arranged in a radial spoke pattern within the intermediate plane region, the line segment trajectory passed by the acting position is not limited to the first line segment trajectory and the second line segment trajectory, and the line segment trajectory passed by the acting position perpendicularly intersects the axis of the silicon carbide substrate 100.

[0142] In some embodiments, the peripheral plane region and the plurality of modified points generated in the peripheral plane region form a peripheral layer 132, and the plurality of modified points are arranged in a radial spoke pattern within the peripheral plane region; Step D further includes:

[0143] Step D3: Drive the silicon carbide substrate 100 to translate relative to the modification device along the third radial direction of the carbon surface 12, so that the acting position forms a third line segment trajectory passing through the symmetry center of the peripheral plane region. The third line segment trajectory perpendicularly intersects the axis of the silicon carbide substrate 100 and equally divides the peripheral plane region;

[0144] Step D4: With the axis of the silicon carbide substrate 100 as the rotation center, drive the silicon carbide substrate 100 to rotate by a preset angular increment, and keep the orientation of the carbon surface 12 unchanged;

[0145] Step D5: Drive the silicon carbide substrate 100 to translate relative to the modification device along the fourth radial direction of the carbon surface 12, so that the acting position forms a fourth line segment trajectory passing through the symmetry center of the peripheral plane region. The fourth line segment trajectory perpendicularly intersects the axis of the silicon carbide substrate 100 and equally divides the peripheral plane region.

[0146] The third line segment trajectory and the fourth line segment trajectory are respectively two radial spoke line segments, and the intersection point of the two is located on the axis of the silicon carbide substrate 100. It can be understood that in order to form a plurality of modified points arranged in a radial spoke pattern within the peripheral plane region, the line segment trajectory passed by the acting position is not limited to the third line segment trajectory and the fourth line segment trajectory, and the line segment trajectory passed by the acting position perpendicularly intersects the axis of the silicon carbide substrate 100.

[0147] In some embodiments, the intermediate plane region and the plurality of modified points generated in the intermediate plane region form an intermediate layer 131, and the plurality of modified points are arranged in concentric circles within the intermediate plane region; Step B further includes:

[0148] Step B6: Drive the silicon carbide substrate 100 to rotate around the axis for at least one week, so that the acting position forms a first circular ring trajectory around the axis of the silicon carbide substrate 100;

[0149] Step B7: Drive the silicon carbide substrate 100 to displace in a direction parallel to the carbon plane 12 to change the distance from the acting position to the axis of the silicon carbide substrate 100;

[0150] Step B8: Drive the silicon carbide substrate 100 to rotate around the axis for at least one week so that the acting position forms a second circular ring trajectory around the axis of the silicon carbide substrate 100.

[0151] It can be understood that in order to form a plurality of modified points arranged in concentric circles in the middle plane region, the circular ring trajectories passed by the acting position are not limited to the first circular ring trajectory and the second circular ring trajectory, and other circular ring trajectories passed by the acting position are all axially centered on the axis of the silicon carbide substrate 100.

[0152] In some embodiments, the peripheral plane region and the plurality of modified points generated in the peripheral plane region form a peripheral layer 132, and the plurality of modified points are arranged in concentric circles in the peripheral plane region; Step D further includes:

[0153] Step D6: Drive the silicon carbide substrate 100 to rotate around the axis for at least one week so that the acting position forms a third circular ring trajectory around the axis of the silicon carbide substrate 100;

[0154] Step D7: Drive the silicon carbide substrate 100 to displace in a direction parallel to the carbon plane 12 to change the distance from the acting position to the axis of the silicon carbide substrate 100;

[0155] Step D8: Drive the silicon carbide substrate 100 to rotate around the axis for at least one week so that the acting position forms a fourth circular ring trajectory around the axis of the silicon carbide substrate 100.

[0156] It can be understood that in order to form a plurality of modified points arranged in concentric circles in the peripheral plane region, the circular ring trajectories passed by the acting position are not limited to the third circular ring trajectory and the fourth circular ring trajectory, and other circular ring trajectories passed by the acting position are all axially centered on the axis of the silicon carbide substrate 100.

[0157] In some embodiments, the modification device is a laser generator and the acting position is the laser focus;

[0158] Step A includes: Step A3: Adjust the laser focus of the laser generator so that the laser focus falls within the middle plane region inside the silicon carbide substrate 100;

[0159] Step C includes: Step C3: Adjust the laser focus of the laser generator so that the laser focus transfers from one middle plane region to one peripheral plane region along the vertical direction of the carbon plane 12.

[0160] The preparation method of the silicon carbide substrate 100 of the present invention can improve the yield rate of the silicon carbide substrate 100 and avoid obvious movement of doping atoms in the substrate.

[0161] Refer to Figure 7 、 Figure 8 and Figure 9 , the thickness of the silicon carbide substrate 100 decreases in the order of Figure 7 、 Figure 8 and Figure 9 , and the distribution ratio of the intermediate layer 131 to the peripheral layer 132 increases in the order of Figure 7 、 Figure 8 and Figure 9 ; Figure 7 and Figure 8 In the state shown, the resultant force of the modified layer 13 acting on the silicon carbide substrate 100 makes the surface curvature of the silicon carbide substrate 100 positive; Figure 9 In the state shown, the resultant force of the modified layer 13 acting on the silicon carbide substrate 100 makes the surface curvature of the silicon carbide substrate 100 negative; the arrow directions F1, F2, and F3 respectively represent the directions of the resultant force of the modified layer 13 acting on the silicon carbide substrate 100, Figure 8 In the state of Figure 7 , the resultant force of the modified layer 13 acting on the silicon carbide substrate 100 is less than the resultant force of the modified layer 13 acting on the silicon carbide substrate 100 in the state of Figure 8 because the silicon carbide substrate 100 shown in Figure 7 is further thinned compared to the silicon carbide substrate 100 shown in

[0162] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0163] Those of ordinary skill in the art of this technology should recognize that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention. As long as it is within the spirit of the present invention, appropriate changes and variations made to the above embodiments fall within the scope of the present invention claimed.​​​​​​​

Claims

1. A silicon carbide substrate includes a carbon surface and a silicon surface disposed opposite to each other, characterized in that, The silicon carbide substrate has a modified layer distributed between the carbon surface and the silicon surface. The modified layer includes one or more intermediate layers, and a plurality of the intermediate layers are arranged in sequence along the vertical direction of the carbon surface. The pattern of the intermediate layer projected orthogonally onto the carbon surface is an intermediate projection, and a peripheral area surrounding the intermediate projection is formed between the contour of the intermediate projection and the edge of the carbon surface.

2. The silicon carbide substrate according to claim 1, wherein The modified layer further includes at least one peripheral layer. The pattern of the peripheral layer projected orthogonally onto the carbon surface is a peripheral projection. The peripheral projection is located within the peripheral area and surrounds the intermediate projection. Along the vertical direction of the carbon surface, the intermediate layer and the peripheral layer are staggeredly distributed.

3. The silicon carbide substrate according to claim 2, wherein The modified layer forms a plurality of modified layer groups arranged repeatedly along the vertical direction of the carbon surface. Each modified layer group includes at least one of the intermediate layers and at least one of the peripheral layers.

4. The silicon carbide substrate according to claim 2, characterized in that, The intermediate layer and the peripheral layer are arranged alternately layer by layer along the vertical direction of the carbon surface; or the intermediate layer and the peripheral layer are arranged alternately in groups along the vertical direction of the carbon surface.

5. The silicon carbide substrate according to claim 2, characterized in that, The maximum radial dimension of the intermediate layer is , the minimum radial dimension of the inner edge of the peripheral layer is , the maximum radial dimension of the outer edge of the peripheral layer is , the diameter of the outer peripheral surface of the silicon carbide substrate is , 0.1 ≤ ≤ 0.8, 0.2 ≤ ≤ 0.5, 0.2 ≤ ≤ 0.

8.

6. The silicon carbide substrate according to any one of claims 1 to 4, characterized in that, In the vertical direction of the carbon surface, the distance between any two adjacent modified layers is not less than 5 and not greater than 50 ; and / or, Within the area range of the modified layer, there are modified points scattered in a point-like manner, and the distance between any two of the modified points is not less than 100 and not greater than 1000 , within each of the modified layers, the modified points are arranged in an array, or in a concentric circle arrangement, or in a radial spoke arrangement; and / or, The distance between the modification layer closest to the carbon surface and the carbon surface is , and the distance between the modification layer farthest from the carbon surface and the carbon surface is , 10 ≤ ≤ 100 , 50 ≤ ≤ 250 .

7. A method for preparing a silicon carbide substrate, characterized in that, Comprising the following steps: Step A: Adjust the action position of the modified device to the processing area within the silicon carbide substrate, so that the action position falls within at least one of the intermediate areas of the processing area, or falls within a plurality of intermediate areas of the processing area respectively multiple times; Step B: Drive the silicon carbide substrate to move relative to the modified device parallel to the carbon surface, so that a plurality of modified points are generated at the action position within one of the intermediate areas in Step A, or a plurality of modified points are generated at the action position within a plurality of intermediate areas in Step A respectively; The processing area is located between the carbon surface and the silicon surface. The pattern of the intermediate area projected orthogonally onto the carbon surface is an intermediate projection. A peripheral area surrounding the intermediate projection is formed between the contour of the intermediate projection and the edge of the carbon surface. A plurality of intermediate areas are arranged in sequence along the vertical direction of the carbon surface.

8. The method for preparing a silicon carbide substrate according to claim 7, wherein The method for preparing the silicon carbide substrate further includes the following steps: Step C: Transfer the action position of the modified device along the vertical direction of the carbon surface, so that the action position falls within at least one of the peripheral areas of the processing area, or falls within a plurality of peripheral areas of the processing area respectively multiple times; Step D: Drive the silicon carbide substrate to move relative to the modified device parallel to the carbon surface, so that a plurality of modified points are generated at the action position within one of the peripheral areas in Step C, or a plurality of modified points are generated at the action position within a plurality of peripheral areas in Step C respectively; The pattern of the peripheral area projected orthogonally onto the carbon surface is a peripheral projection. The peripheral projection is located within the peripheral area and surrounds the intermediate projection. Along the vertical direction of the carbon surface, a plurality of peripheral areas are arranged in sequence, and the intermediate area and the peripheral area are staggeredly distributed.

9. The method for preparing a silicon carbide substrate according to claim 8, wherein In the step A, making the action position fall within at least one of the intermediate areas of the processing area, or falling within a plurality of intermediate areas of the processing area respectively multiple times includes: Step A1: Control the action position of the modified device to move closer to the carbon surface and transfer from one of the peripheral areas to one of the intermediate areas; Step A2: Control the action position of the modification device to move closer to the carbon surface and migrate from one intermediate surface region to another intermediate surface region; In the said Step C, transferring the action position of the modification device along the vertical direction of the carbon surface includes: Step C1: Control the action position of the modification device to move closer to the carbon surface and transfer from one intermediate surface region to one of the peripheral surface regions; Step C2: Control the action position of the modification device to move closer to the carbon surface and migrate from one peripheral surface region to another peripheral surface region.

10. The method for preparing a silicon carbide substrate according to claim 9, wherein Step A1 includes: migrating the acting position from one of the intermediate plane regions to another adjacent intermediate plane region along a direction perpendicular to the carbon plane after a distance of 5 ≤ ≤ 50 ; Step C1 includes: acting position transfers from one of the intermediate surface regions along a direction perpendicular to the carbon surface to an adjacent peripheral surface region after a distance. Step C2 includes: migrating the acting position along a direction perpendicular to the carbon surface from one of the peripheral surface regions to reach another adjacent peripheral surface region after a distance. ​ 11. The method for preparing a silicon carbide substrate according to claim 8, wherein Execute the said Step A, the said Step B, the said Step C and the said Step D repeatedly for several times.

12. The method for preparing a silicon carbide substrate according to any one of claims 7 to 11, wherein The method for preparing the silicon carbide substrate further includes: Step E1: First, adjust the acting position of the modified device to the first processing plane area within the silicon carbide substrate. The first processing plane area is the one that is the farthest from the carbon surface among multiple processing plane areas, and the distance from the first processing plane area to the carbon surface is , 50 ≤ ≤250 ; Step E2: Drive the silicon carbide substrate to move relative to the modification device parallel to the carbon surface, and first generate a plurality of modified points in the first processing surface region in Step E1 at the action position, so that the first processing surface region forms a first modified layer prior to other processing surface regions.

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