Silicon carbide substrate and method of manufacturing a silicon carbide substrate

Abstract

The present application provides a silicon carbide substrate and a silicon carbide substrate preparation method. The silicon carbide substrate has a modification layer distributed between a carbon surface and a silicon surface. The modification layer includes one or more intermediate layers. The intermediate layers are arranged in sequence along the vertical direction of the carbon surface. The intermediate layer orthographic projection on the plane of the carbon surface is an intermediate projection. The edge profile of the intermediate projection and the edge of the carbon surface form a peripheral region surrounding the intermediate projection. The silicon carbide substrate preparation method includes: adjusting the action position of a modification device to a processing surface domain in the silicon carbide substrate, so that the action position falls in one of the intermediate surface domains of the processing surface domain at least once, or falls in multiple intermediate surface domains of the processing surface domain respectively multiple times; driving the silicon carbide substrate to move relative to the modification device parallel to the carbon surface, so that the action position generates multiple modification points in one of the intermediate surface domains of step A, or generates multiple modification points in multiple intermediate surface domains of step A respectively.

Description

Technical Field

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

[0002] Silicon carbide substrates are important components for the preparation of various semiconductor devices. Due to epitaxy, etching and other process treatments, silicon carbide substrates will bend and deform, which will affect the performance of semiconductor devices. The curved silicon carbide substrate is bowl-shaped or inverted bowl-shaped. The surface state of the silicon carbide substrate is usually measured by BOW (bowness). The absolute value of BOW indicates the degree of curvature of the silicon carbide substrate, and the positive or negative BOW value indicates the curvature direction of the silicon carbide substrate. The current silicon carbide substrate shaping methods in the industry include back thinning and high-temperature annealing. Back thinning can only shape the curvature of positively curved silicon carbide substrates to the negative direction, and cannot shape the curvature of negatively curved silicon carbide substrates to the positive direction. High-temperature annealing causes lattice relaxation and rearrangement inside the silicon carbide substrate, but is accompanied by obvious movement of doping atoms, which affects 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 shaping of the curvature toward a positive change and shaping of the curvature toward a negative change.

[0004] The silicon carbide substrate of the present invention includes a carbon surface and a silicon surface arranged in back-to-back relation, and has a modified layer distributed between the carbon surface and the silicon surface. The modified layer includes one or more intermediate layers, and the multiple intermediate layers are arranged in sequence along the vertical direction of the carbon surface. The figure of the intermediate layer projected onto the plane where the carbon surface is located is the intermediate projection, and the outline of the intermediate projection and the edge of the carbon surface form a peripheral area surrounding the intermediate projection.

[0005] With such a configuration, the silicon carbide substrate of the present invention is compatible with shaping modes in which the curvature changes toward positive and negative changes. During the epitaxy of the silicon carbide substrate and subsequent device production, the surface state and curvature change trend of the silicon carbide substrate can be adjusted by back-removing the carbon surface of the silicon carbide substrate. Under the action of the intermediate layer and under the treatment of simply receiving back-removal, the silicon carbide substrate exhibits a surface state with a negative curvature. Because the intermediate layer is simultaneously thinned as the back-removal is performed, the effect of the intermediate layer on the silicon carbide substrate to cause the silicon carbide substrate to exhibit a negative curvature surface gradually weakens during the period when the intermediate layer is gradually thinned and has not yet been completely removed, and the surface shape of the silicon carbide substrate thus exhibits a positive curvature change. After the intermediate layer is completely removed, the silicon carbide substrate exhibits a negative curvature change as the back-removal continues. By simply adjusting the back-removal thickness, the curvature change trend of the silicon carbide substrate can be selectively controlled. By determining the appropriate back-removal thickness, the silicon carbide substrate can be shaped toward a positive curvature change or a negative curvature change.

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

[0007] With this arrangement, the silicon carbide substrate has deformation tendencies in different bending directions under the action of the intermediate layer and the peripheral layer. During the epitaxy of the silicon carbide substrate and subsequent device production, the carbon surface of the silicon carbide substrate can be back-removed to adjust the surface state and curvature change trend of the silicon carbide substrate. The distances from the intermediate layer and the peripheral layer to the carbon surface are set differently, so adjusting the removal thickness can change the distribution and quantity ratio of the remaining intermediate layer and the remaining peripheral layer in the silicon carbide substrate, thereby adjusting the stress magnitude of the intermediate layer and the peripheral layer acting on the inside of the silicon carbide substrate, so as to selectively change the deformation direction and deformation amplitude of the silicon carbide substrate, making the silicon carbide substrate compatible with positive and negative curvature shaping.

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

[0009] In some embodiments, the number of modified layer groups is at least 2 and at most 5, and in each modified layer group, the number of modified layers is at least 2 and at most 16.

[0010] In some embodiments, the intermediate layers and the outer layers are alternately arranged layer by layer along the vertical direction of the carbon surface; or, the intermediate layers and the outer layers are alternately arranged 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 shape of the outer outline of the peripheral projection includes a circle and a polygon, and the shape of the inner edge of the peripheral projection includes a circle and a polygon.

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

[0013] In some embodiments, the distance between any two adjacent modified layers in the vertical direction of the carbon surface is not less than 5 and no more than 50 .

[0014] In some embodiments, the modified layer has scattered modified points within its surface area, and the distance between any two modified points is not less than 100 and no more than 1000 In each modified layer, the modified points are arranged in an array, concentric circles, or radial spokes.

[0015] In some embodiments, the distance between the nearest modified layer to the carbon face is , and the distance between the farthest modified layer to the carbon face 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 peripheral layer is , the maximum radial dimension of the outer edge of the peripheral 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 of the present application comprises the following steps:

[0018] Step A, adjusting the action position of the modification device to a processing surface domain within the silicon carbide substrate, so that the action position falls within one of the intermediate surface domains of the processing surface domain at least once, or falls within multiple intermediate surface domains of the processing surface domain respectively multiple times;

[0019] Step B, moving the silicon carbide substrate relative to the modification device parallel to the carbon face, so that the action position generates multiple modification points within one of the intermediate surface domains of Step A, or generates multiple modification points within multiple intermediate surface domains of Step A respectively;

[0020] The processing surface domain is located between the carbon face and the silicon face, the intermediate projection is the projection of the intermediate surface domain onto the carbon face, the edge profile of the intermediate projection and the edge of the carbon face form a peripheral region surrounding the intermediate projection, and the multiple intermediate surface domains are arranged in sequence along the vertical direction of the carbon face.

[0021] The method for preparing a silicon carbide substrate of the present application can improve the yield of the silicon carbide substrate and avoid the occurrence of significant movement of doped atoms within the substrate.

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

[0023] Step C, shifting the action position of the modification device along the vertical direction of the carbon face, so that the action position falls within one of the peripheral surface domains of the processing surface domain at least once, or falls within multiple peripheral surface domains of the processing surface domain respectively multiple times;

[0024] Step D, moving the silicon carbide substrate relative to the modification device parallel to the carbon face to cause the action position to generate multiple modification points in one of the peripheral face regions of step C, or to generate multiple modification points in multiple peripheral face regions of step C, respectively;

[0025] The pattern of the peripheral face region orthogonally projected on the carbon face is a peripheral projection, the peripheral projection is located in the peripheral region and surrounds the central projection, multiple peripheral face regions are arranged in sequence along the vertical direction of the carbon face, and the central face region and the peripheral face region are distributed in a staggered manner.

[0026] In some embodiments, in step A, the action position falls in one of the central face regions of the processing face region at least once, or falls in multiple central face regions of the processing face region multiple times, respectively, including:

[0027] Step A1, controlling the action position of the modification device to make a transfer movement close to the carbon face, and transferring from one of the peripheral face regions to one of the central face regions;

[0028] Step A2, controlling the action position of the modification device to make a migration movement close to the carbon face, and migrating from one of the central face regions to another central face region;

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

[0030] Step C1, controlling the action position of the modification device to make a transfer movement close to the carbon face, and transferring from one of the central face regions to one of the peripheral face regions;

[0031] Step C2, controlling the action position of the modification device to make a migration movement close to the carbon face, and migrating from one of the peripheral face regions to another peripheral face region.

[0032] In some embodiments, step A1 includes: transferring the action position from one of the peripheral face regions to the adjacent one of the central face regions along the direction perpendicular to the carbon face by a distance of 5 ≤ ≤50 ;

[0033] Step A2 includes: migrating the action position from one of the central face regions to the adjacent another central face region along the direction perpendicular to the carbon face by a distance of ;

[0034] Step C1 includes: transferring the action position from one of the central face regions to the adjacent one of the peripheral face regions along the direction perpendicular to the carbon face by a distance of ;

[0035] Step C2 includes: migrating the action position from one of the peripheral face regions to another peripheral face region along the direction perpendicular to the carbon face by a distance of The distance from the other peripheral face domain that arrives later.

[0036] In some embodiments, the steps A, B, C and D are repeated several times.

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

[0038] Step E1, the action position of the modification device is first adjusted to a first processing face domain in the silicon carbide substrate, the first processing face domain is the one farthest from the carbon face among the plurality of processing face domains, and the distance from the first processing face domain to the carbon face is , 50 ≤ ≤250 ;

[0039] Step E2, the silicon carbide substrate is driven to move relative to the modification device parallel to the carbon face, and a plurality of modification points are first generated in the first processing face domain in step E1, so that the first processing face domain first forms a first modification layer relative to the other processing face domains.

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

[0041] Step F, the silicon carbide substrate is fixedly placed on the modification processing platform, and the silicon face is directed towards the modification processing platform and the carbon face is directed away from the modification processing platform;

[0042] Step B comprises: Step B1, driving the modification processing platform to move relative to the modification device in a direction parallel to the carbon face;

[0043] Step D comprises: Step D1, driving the modification processing platform to move relative to the modification device in a direction parallel to the carbon face.

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

[0045] Step G, the modification processing platform applies an adsorption force to the silicon face, so that the silicon face is flatly attached to the modification processing platform.

[0046] In some embodiments, step B comprises:

[0047] Step B2, driving the silicon carbide substrate and the modification device to move relative to each other intermittently in a direction parallel to the carbon face, and the step distance of the relative intermittent movement is , 100 ≤ ≤1000 ;

[0048] Step D comprises:

[0049] Step D2: driving the silicon carbide substrate and the modified device to move relative to each other in a direction parallel to the carbon surface, with a step length of relative intermittent movement of , 100 ≤ ≤1000 .

[0050] In some embodiments, the intermediate surface region and the plurality of modified points generated in the intermediate surface region form an intermediate layer, and the plurality of modified points are arranged in a radially spoke-like pattern within the intermediate surface region; step B further comprises:

[0051] Step B3, driving the silicon carbide substrate to translate relative to the modification device along a first radial direction of the carbon surface so that the action position forms a first line segment trajectory passing through the symmetry center of the middle surface area, and the first line segment trajectory equally divides the middle surface area;

[0052] Step B4: rotating the silicon carbide substrate by a preset angle with the axis of the silicon carbide substrate as the rotation center, while keeping the carbon surface orientation unchanged;

[0053] Step B5: driving the silicon carbide substrate to translate relative to the modification device along the second radial direction of the carbon surface so that the action position forms a second line segment trajectory passing through the symmetry center of the middle surface area, and the second line segment trajectory equally divides the middle surface area.

[0054] In some embodiments, the peripheral surface region and the plurality of modified points generated in the peripheral surface region form a peripheral layer, and the plurality of modified points are arranged in a radially spoke pattern within the peripheral surface region; step D further comprises:

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

[0056] Step D4: rotating the silicon carbide substrate by a preset angle with the axis of the silicon carbide substrate as the rotation center, while keeping the carbon surface orientation unchanged;

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

[0058] In some embodiments, the intermediate surface region and the plurality of modified points generated in the intermediate surface region form an intermediate layer, and the plurality of modified points are arranged in concentric circles within the intermediate surface region; step B further comprises:

[0059] Step B6, driving the silicon carbide substrate to rotate around the axis for at least one revolution, so that the action position forms a first circular track around the axis of the silicon carbide substrate;

[0060] Step B7: driving the silicon carbide substrate to move in a direction parallel to the carbon surface to change the distance between the action position and the axis of the silicon carbide substrate;

[0061] Step B8: driving the silicon carbide substrate to rotate around the axis for at least one revolution, so that the action position forms a second circular orbit around the axis of the silicon carbide substrate.

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

[0063] Step D6, driving the silicon carbide substrate to rotate around the axis for at least one revolution, so that the action position forms a third circular orbit around the axis of the silicon carbide substrate;

[0064] Step D7: driving the silicon carbide substrate to move in a direction parallel to the carbon surface to change the distance between the action position and the axis of the silicon carbide substrate;

[0065] Step D8: driving the silicon carbide substrate to rotate around the axis for at least one revolution, so that the action position forms a fourth circular orbit around the axis of the silicon carbide substrate.

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

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

[0068] Step C includes: Step C3, adjusting the laser focus of the laser generator so that the laser focus is transferred from one of the middle surface areas to one of the peripheral surface areas along the vertical direction of the carbon surface.

[0069] Compared with the prior art, the silicon carbide substrate of the present invention can achieve an ideal shaping effect by back-removing material in its initial state, regardless of whether it has a positive or negative curvature surface. The silicon carbide substrate can be deformed positively or negatively by simply adjusting the thickness of the back-removal material. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0071] Figure 2 Schematic diagram of the middle layer of the silicon carbide substrate according to the second embodiment of the present invention;

[0072] Figure 3 Schematic diagram of the middle layer of the silicon carbide substrate according to the third embodiment of the present invention;

[0073] Figure 4Schematic diagram of an intermediate layer of a silicon carbide substrate according to a 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 This is a schematic diagram of the first shaping analysis of the silicon carbide substrate of the present invention;

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

[0078] Figure 9 Schematic diagram of the third shaping analysis 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 DESCRIPTION

[0080] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

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

[0082] The present invention provides a silicon carbide substrate 100 that is compatible with two shaping modes: positive curvature change and negative curvature change, and also provides a method for preparing the silicon carbide substrate 100 that can obtain the silicon carbide substrate 100 of the present invention. Compatibility with positive curvature change and negative curvature change means that the BOW (bowness) value of the silicon carbide substrate 100 is allowed to increase to achieve a positive curvature change, and the BOW value is allowed to decrease to achieve a negative curvature change. Positive change includes the situation where the BOW value is negative and the value increases, the BOW value changes from negative to positive, and the BOW value is positive and the value increases; negative change includes the situation where the BOW value is negative and the value decreases, the BOW value changes from positive to negative, and the BOW value is positive and the 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 removal thicknesses produce different shaping effects. By simply adjusting the back removal thickness, the curvature of the silicon carbide substrate 100 can be changed to a positive or negative direction.

[0084] See Figure 1 The silicon carbide substrate 100 of the present invention has a modified layer 13 distributed between the carbon surface 12 and the silicon surface 11. The carbon surface 12 and the silicon surface 11 are two mutually parallel end surfaces 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 an internal lattice distortion. Therefore, the modified layer 13 will exert stress on the entire silicon carbide substrate 100. This stress causes the silicon carbide substrate 100 to exhibit a certain degree of bending. The shape of the modified layer 13 will cause the direction of the stress on the silicon carbide substrate 100 to change. Therefore, modified layers 13 of different shapes will cause the silicon carbide substrate 100 to exhibit different surface shapes.

[0085] In some embodiments, the modified layer 13 has modified points that are dispersed within its surface area. The means for obtaining the modified layer 13 includes irradiating the interior of the silicon carbide substrate 100 with laser light generated by a laser generator, causing lattice distortion at the irradiated position within the silicon carbide substrate 100 through the energy in the laser light, and forming modified points at the position irradiated by the laser. Multiple modified points are obtained by changing the position irradiated by the laser, and the processing surface area where the multiple modified points are located forms the modified layer 13. Specifically, in order to obtain a lamellar modified layer 13, it is first necessary to adjust the laser generator so that the laser focus falls on the processing surface area within the silicon carbide substrate 100. The processing surface area is a lamellar area that is artificially determined in advance within the silicon carbide substrate 100. Then, the position of the laser focus is moved within the same processing surface area, thereby obtaining multiple modified points within the same processing surface area. After several irradiations, the processing surface area forms a modified layer 13. Optionally, within the surface area of ​​any modified layer 13, the distance between any two adjacent modified points is not less than 100 and no more than 1000 Such an arrangement can avoid cracks caused by too small a distance between the modified points in the modified layer 13 , and can also ensure the modification effect of the modified layer 13 .

[0086] It is understood that, in other embodiments, the means of obtaining the modified layer 13 is not limited to using laser irradiation to the interior of the silicon carbide substrate 100 . Any means of obtaining modified points within the processing surface area without destroying 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 there are multiple intermediate layers 131, the multiple intermediate layers 131 are arranged sequentially along a direction perpendicular to the carbon surface 12, and each intermediate layer 131 is parallel to the carbon surface 12 and the silicon surface 11. The direction perpendicular to the carbon surface 12 is also the axial direction of the silicon carbide substrate 100. The shape of the intermediate layer 131 is specifically such that when the intermediate layer 131 is projected onto the carbon surface 12 to form an intermediate projection, a peripheral 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 peripheral region. Optionally, in some embodiments, the modified layer 13 in the silicon carbide substrate 100 is entirely composed of intermediate layers 131. The number of intermediate layers 131 can be one or more, and the shapes and sizes of the multiple intermediate layers 131 can be the same or different. The following describes the mechanism by which this embodiment achieves compatibility of the silicon carbide substrate 100 with both positive and negative curvature changes.

[0088] The silicon carbide substrate 100 exhibits a negative curvature (i.e., a negative BOW value) solely under the effect of the backside stripping process. Furthermore, the silicon carbide substrate 100 exhibits a negative curvature solely under the stress of the intermediate layer 131. The greater the thickness of the intermediate layer 131, the more pronounced the negative curvature. During the backside stripping process, not only does the thickness of the silicon carbide substrate 100 itself decrease, but the thickness of the intermediate layer 131 also continuously decreases. Therefore, while the intermediate layer 131 is being thinned but not yet completely removed, the deformation effect of the intermediate layer 131 on the negative curvature of the silicon carbide substrate 100 gradually weakens. As a result, the curvature of the silicon carbide substrate 100 exhibits a positive change, specifically, a negative and gradually increasing BOW value. After the intermediate layer 131 is completely removed, the silicon carbide substrate 100 is subjected solely to the backside stripping process. Therefore, the silicon carbide substrate 100 exhibits a negative curvature change after the intermediate layer 131 is removed. Therefore, the curvature variation trend of the silicon carbide substrate 100 can be controlled by simply adjusting the thickness of the back surface removal.

[0089] In other embodiments, the silicon carbide substrate 100 further includes at least one peripheral layer 132, with the intermediate layer 131 and the peripheral layer 132 being staggered along a direction perpendicular to the carbon surface 12. When there are multiple peripheral layers 132, the multiple peripheral layers 132 are sequentially arranged along a direction perpendicular to the carbon surface 12, and each peripheral layer 132 is parallel to the carbon surface 12 and the silicon surface 11. The shapes and sizes of the multiple peripheral layers 132 can be the same or different. Specifically, no intermediate layer 131 and no peripheral layer 132 are located at the same height. When a 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 through one intermediate layer 131 or one peripheral layer 132, and does not cut through both the intermediate layer 131 and the peripheral layer 132. The shape of the peripheral layer 132 is such that when the peripheral layer 132 is projected onto the carbon surface 12 to form a peripheral projection, the peripheral projection is located within the peripheral region 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 curvature changes.

[0090] The silicon carbide substrate 100 exhibits a surface state with positive curvature simply under the stress of the outer layer 132. The thicker the outer layer 132 is, the more significant the positive curvature is. 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. Due to the differentiated settings of the distances from the intermediate layer 131 and the outer layer 132 to the carbon surface 12, and the differentiated settings of the distances from the intermediate layer 131 and the outer layer 132 to the silicon surface 11, during the back-side material removal process, the distribution and quantity ratio of the remaining intermediate layer 131 and the remaining outer layer 132 in the silicon carbide substrate 100 can be changed by adjusting the material removal thickness, and the stress magnitudes of the intermediate layer 131 and the outer layer 132 acting on the silicon carbide substrate 100 can be adjusted, thereby changing the direction and magnitude of the resultant force of the modified layer 13 on the silicon carbide substrate 100. In this way, the deformation direction and deformation amplitude of the silicon carbide substrate 100 can be selectively changed. The deformation direction and deformation amplitude of the silicon carbide substrate 100 both fall within the scope of the curvature change trend of the silicon carbide substrate 100.

[0091] See Figure 1In some embodiments, the modified layer group 13 forms a plurality of modified layer groups 130 repeatedly arranged along a direction perpendicular to the carbon surface 12. Each modified layer group 130 includes at least one intermediate layer 131 and at least one peripheral layer 132. This arrangement allows a silicon carbide substrate 100 to be reshaped multiple times by backside removal until the final surface shape of the silicon carbide substrate 100 meets production requirements. For example, during the back-removal process, if the removal thickness is incorrectly set or a processing error occurs during the back-removal process, the actual removal thickness may not match the selected removal thickness, resulting in an error in thinning the intermediate layer 131 or the peripheral layer 132 in the current modified layer group 130 closest to the carbon surface 12, thereby causing the surface correction effect of the silicon carbide substrate 100 to be unsatisfactory. In this way, the back-removal of the silicon carbide substrate 100 can be continued and the current modified layer group 130 closest to the carbon surface 12 can be removed, so that the intermediate layer 131 or the peripheral layer 132 of the next modified layer group 130 can be thinned. In other words, providing multiple modified layer groups 130 can provide more opportunities for reshaping using the back-removal method.

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

[0093] See Figure 1 In some embodiments, the intermediate layers 131 and the peripheral layers 132 are alternately arranged layer by layer along the vertical direction of the carbon surface 12; in some embodiments not shown in the figure, the intermediate layers 131 and the peripheral layers 132 are alternately arranged in groups along the vertical direction of the carbon surface 12, that is, a plurality of intermediate layers 131 constitute an intermediate modified group, and a plurality of peripheral layers 132 constitute a peripheral modified group. The intermediate modified groups and the peripheral modified groups are alternately arranged along the vertical direction of the carbon surface 12. In each intermediate modified group, a plurality of intermediate layers 131 are sequentially arranged along the vertical direction of the carbon surface 12, and in each peripheral modified group, a plurality of peripheral layers 132 are sequentially arranged along the vertical direction of the carbon surface 12. Optionally, regardless of whether the intermediate layers 131 and the peripheral layers 132 are alternately arranged layer by layer or in groups, the distance between any two adjacent modified layers 13 is not less than 5 and no more than 50 Such an arrangement can avoid cracks caused by the interaction between two adjacent modified layers 13 due to the small distance between the modified layers 13, and can also ensure that the number of modified layers 13 is sufficient.

[0094] Furthermore, in some embodiments, the shape of the intermediate projection includes a circle and a polygon, and the surface shape of the intermediate layer 131 can be a circle or a polygon, such as Figure 3~Figure 4The 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 may be a circle or a polygon, as shown Figure 5~Figure 6 As shown. Preferably, the orthographic projection of each modified layer 13, including the intermediate layer 131 and the peripheral layer 132, onto the carbon surface 12 is a centrally symmetrical pattern, with the center of symmetry of each centrally symmetrical pattern located on the axis of the silicon carbide substrate 100. With this arrangement, the forces exerted by the intermediate layer 131 and the peripheral layer 132 on the interior of the silicon carbide substrate 100 are symmetrically distributed about the axis of the silicon carbide substrate 100, resulting in the overall shape of the silicon carbide substrate 100 being closer to a standard solid of revolution.

[0095] Furthermore, in some embodiments, within any modified layer 13 , the modified points are arranged in an array, a concentric circle, or a radial spoke arrangement. Figure 2 The middle layer 131 in which the modified points are arranged in concentric circles is shown. Figure 3 and Figure 4 The diagram illustrates an intermediate layer 131 with modified points arranged in a radial pattern. An array arrangement specifically refers to a plurality of modified points arranged in rows and columns perpendicular to each other; a concentric circle arrangement specifically refers to a plurality of modified points located in a plurality of concentric rings centered about the axis of the silicon carbide substrate 100; and a radial-spoke arrangement specifically refers to a plurality of modified points located in a plurality of radial segments, which are rotationally symmetrically distributed about the axis of the silicon carbide substrate 100.

[0096] Furthermore, in some embodiments, the distance between the modified layer 13 closest to the carbon surface 12 and the carbon surface 12 is The distance between the modified layer 13 farthest from the carbon surface 12 and the carbon surface 12 is , of which 10 ≤ ≤100 , 50 ≤ ≤250 In this way, 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 If the thickness is too small, the modified layer 13 closest to the carbon surface 12 may crack. If the distance between the modified layer 13 farthest from the carbon surface 12 and the carbon surface 12 is too large, the number of modified layers 13 in the silicon carbide substrate 100 will be reduced. If the size is too small, the amount of the modified layer 13 in the silicon carbide substrate 100 will be reduced; If the stress is too large, the stress exerted by the modified layer 13 on the silicon carbide substrate 100 will be weak or even disappear, and it will be difficult for the modified layer 13 to exert its influence on the surface shape.

[0097] Furthermore, in some embodiments, the maximum radial dimension of the intermediate layer 131 is , the minimum radial dimension of the inner edge of the outer layer 132 is The maximum radial dimension of the outer edge of the outer layer 132 is The outer diameter 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 middle layer 131 and the minimum radial dimension of the inner edge of the outer layer 132 Refers to the diameter of the inscribed circle of the inner contour of the outer layer 132, the maximum radial dimension of the outer edge of the outer layer 132 It refers to the diameter of the circumscribed circle of the outer contour of the outer layer 132. With this configuration, the intermediate layer 131 has a negative impact on the surface shape of the silicon carbide substrate 100, while the outer layer 132 has a positive impact on the surface shape of the silicon carbide substrate 100. The effects of the intermediate layer 131 and the outer layer 132 on the surface shape of the silicon carbide substrate 100 are significantly different.

[0098] The following describes a method for preparing a silicon carbide substrate 100 according to the present invention. The method comprises the following steps:

[0099] Step A: adjusting the action position of the modifying device to the processing surface area in the silicon carbide substrate 100 so that the action position falls within one of the middle surface areas of the processing surface area at least once, or falls within multiple middle surface areas of the processing surface area multiple times;

[0100] Step B: driving the silicon carbide substrate 100 to move relative to the modification device parallel to the carbon surface 12, so that the action position generates multiple modified points in one of the middle surface areas of step A, or generates multiple modified points in multiple middle surface areas of step A;

[0101] The processing surface domain is an artificially determined layer area located between the carbon surface 12 and the silicon surface 11. There are multiple processing surface domains, and the multiple processing surface domains are arranged in sequence along the vertical direction of the carbon surface 12. The processing surface domain includes at least one or more intermediate surface domains, and the intermediate surface domains are used to form the intermediate layer 131. In some embodiments, the processing surface domain also includes at least one peripheral surface domain for forming the peripheral layer 132. Along the vertical direction of the carbon surface 12, multiple peripheral surface domains are arranged in sequence, and the intermediate surface domains are staggered with the peripheral surface domains. The intermediate surface domains and the peripheral surface domains are alternately arranged layer by layer along the vertical direction of the carbon surface 12, or the intermediate surface domains and the peripheral surface domains are alternately arranged in groups along the vertical direction of the carbon surface 12. The figure of the middle surface area projected onto the carbon surface 12 is the middle projection, and the outline of the middle projection and the edge of the carbon surface 12 form a peripheral area surrounding the middle projection. Multiple middle surface areas are arranged in sequence along the vertical direction of the carbon surface 12. The middle surface area and the multiple modified points in the middle surface area form a modified layer 13, and the peripheral surface area and the multiple modified points in the peripheral surface area form a peripheral layer 132.

[0102] Specifically, the modification device can be a laser generator, and the modification device's action position is the laser focus of the laser generator. Laser light is emitted from the carbon surface 12 of the silicon carbide substrate 100 into the silicon carbide substrate 100, and the locations where the laser focus acts on the processing surface area form modified points. The modified points and the processing surface area form a modified layer. The processing surface area defines the distribution range of the modified points within the plane of the processing surface area, that is, the modified points will not exceed the processing surface area. Specifically, the modified points located in the middle surface area do not exceed the outer contour of the middle surface area, and the modified points located in the outer surface area do not exceed the inner and outer contours of the outer surface area.

[0103] In step A, if the active position lands once on one of the intermediate regions of the processing surface, then after step B is completed, the intermediate region where the active position landed forms an intermediate layer 131. If the active position lands multiple times on multiple intermediate regions of the processing surface, then after step B is completed, multiple intermediate layers 131 are formed in each of the multiple intermediate regions where the active position landed. Step B is intended to cause the active position to briefly land at multiple stopping positions within the intermediate region, ultimately forming multiple modified points at these stopping positions. The active position moves from one stopping position to another as the silicon carbide substrate 100 moves relative to the modified device parallel to the carbon surface 12. The multiple stopping positions within the intermediate region can be arranged in an array, concentric circles, or radial stripes. It should be noted that if there are multiple intermediate layers 131, the active position will only migrate from the current intermediate surface area and fall into another intermediate surface area after all the stop positions within an intermediate surface area are briefly stopped. That is, only after an intermediate layer 131 is formed, the active position will migrate to another intermediate surface area 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, shifting the action position of the modification device along the vertical direction of the carbon surface 12 so that the action position falls within one of the peripheral surface areas of the processing surface area at least once, or falls within multiple peripheral surface areas of the processing surface area multiple times;

[0106] Step D: driving the silicon carbide substrate 100 to move relative to the modification device parallel to the carbon surface 12, so that the action position generates multiple modified points in one of the peripheral surface areas of step C, or generates multiple modified points in multiple peripheral surface areas of step C;

[0107] The figure of the outer surface region being projected onto the carbon surface 12 is the outer projection, and the outer projection is located in the outer area and surrounds the middle projection.

[0108] In step C, if the active position lands once on one of the peripheral regions of the processing surface, then after step D is completed, the peripheral region where the active position landed forms a peripheral layer 132. If the active position lands multiple times on multiple peripheral regions of the processing surface, then after step D is completed, the multiple peripheral regions where the active position landed form multiple peripheral layers 132. Step C is intended to cause the active position to briefly land at multiple stopping positions within the peripheral region, ultimately forming multiple modified points at these stopping positions. The active position moves from one stopping position to another as the silicon carbide substrate 100 moves relative to the modification device parallel to the carbon surface 12. The multiple stopping positions within the peripheral region can be arranged in an array, concentric circles, or radial stripes. It should be noted that if there are multiple peripheral layers 132, the active position will only migrate from the current peripheral surface area and fall into another peripheral surface area after all the stop positions within a peripheral surface area are briefly stopped. That is, only after one peripheral layer 132 is formed, the active position will migrate to another peripheral surface area to process a new peripheral layer 132.

[0109] In some embodiments, in step A, causing the action position to fall within one of the intermediate areas of the processing area at least once, or to fall within multiple intermediate areas of the processing area multiple times, comprises:

[0110] Step A1, controlling the action position of the modification device to move closer to the carbon surface 12, and transferring from one of the peripheral surface areas to one of the middle surface areas;

[0111] Step A2: controlling the action position of the modification device to migrate close to the carbon surface 12 and migrate from one intermediate surface region to another intermediate surface region;

[0112] In step C, shifting the action position of the modification device along the vertical direction of the carbon surface 12 includes:

[0113] Step C1, controlling the action position of the modification device to move closer to the carbon surface 12, and to move from one of the middle surface areas to one of the peripheral surface areas;

[0114] Step C2: Control the action position of the modification device to migrate close to the carbon surface 12 and migrate from one peripheral surface area to another peripheral surface area.

[0115] Switching the active position between multiple intermediate surface regions and multiple peripheral surface regions constitutes migration of the active position of the modified device; switching the active position from the intermediate surface region to the peripheral surface region and vice versa constitutes transfer of the active position of the modified device. Steps A1 and A2, as well as steps C1 and C2, are intended to stipulate that, regardless of whether the active position is migrating or transferring, the direction of movement of the active position is toward the carbon surface 12.

[0116] Specifically, step A1 includes: along the direction perpendicular to the carbon surface 12, the action position is transferred from one of the peripheral surface areas After reaching an adjacent middle area, 5 ≤ ≤50 ;

[0117] Step A2 includes: moving the action position from one of the middle surface areas along the direction perpendicular to the carbon surface 12 After reaching the adjacent middle area;

[0118] Step C1 includes: moving the action position from one of the middle surface areas along the direction perpendicular to the carbon surface 12 After reaching a certain distance, it reaches an adjacent peripheral area;

[0119] Step C2 includes: moving the action position from one of the peripheral areas along the direction perpendicular to the carbon surface 12 After reaching the adjacent outer area;

[0120] The method for preparing the silicon carbide substrate 100 further includes:

[0121] Step E1: first adjust the working position of the modified device to the first processing area in the silicon carbide substrate 100. The first processing area is the one farthest from the carbon surface 12 among the multiple processing areas. The distance from the first processing area to the carbon surface 12 is , 50 ≤ ≤250 ;

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

[0123] The first processing surface area is the one farthest from the carbon surface 12 among the multiple processing surface areas. In this way, during the processing of the modified layer 13, the action position first falls on the first processing surface area farthest from the carbon surface 12. After the modified layer 13 is formed on the processing surface area farthest from the carbon surface 12, the action position moves toward the carbon surface 12 in the vertical direction of the carbon surface 12 by a distance of , thereby reaching the second-farthest processing area from the carbon surface 12, and then the action position continues to move toward the carbon surface 12 in the vertical direction of the carbon surface 12 , thereby reaching the processing surface area third farthest from the carbon surface 12, and so on. By adopting a transfer and migration method in which the action position is upwardly close to the carbon surface 12, it can be ensured that when processing any modified layer 13, the various processing surface areas located above the modified surface area being processed are limitedly affected by the laser action.

[0124] In contrast, the transfer and migration method of the action position downward away from the carbon surface 12 has the following defects: the modified layer 13 located 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 modified surface area currently being processed.

[0125] In some embodiments, step A, step B, step C, and step D are repeated several times to obtain a plurality of modified layer groups 130 sequentially arranged in a direction perpendicular to the carbon surface 12 .

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

[0127] Step F, placing the silicon carbide substrate 100 on a modification process carrier, with the silicon surface 11 facing the modification process carrier and the carbon surface 12 facing away from the modification process carrier;

[0128] Step G: The modification stage applies an adsorption force to the silicon surface 11 so that the silicon surface 11 is in contact with the surface of the modification stage;

[0129] Step B includes: step B1, driving the modification processing stage to move relative to the modification device in a direction parallel to the carbon surface 12;

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

[0131] Specifically, the processing stage applies a negative pressure suction force of 20-100 kPa to the silicon surface 11. This configuration can prevent deformation of the silicon carbide substrate 100 when the laser generator is used to irradiate and modify the silicon carbide substrate 100, thereby ensuring that the laser focus can be accurately placed on each processing surface area.

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

[0133] Step B2: driving the silicon carbide substrate 100 and the modified device to move relative to each other in a direction parallel to the carbon surface 12, with a step length of the relative intermittent movement being , 100 ≤ ≤1000 ;

[0134] Step D also includes:

[0135] Step D2: Drive the silicon carbide substrate 100 and the modified device to move relative to each other in a direction parallel to the carbon surface 12. The step length of the relative intermittent movement is , 100 ≤ ≤1000 .

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

[0137] In some embodiments, the intermediate surface region and the plurality of modified points generated in the intermediate surface region form an intermediate layer 131, and the plurality of modified points are arranged in a radially spoke-like pattern within the intermediate surface region; step B further includes:

[0138] Step B3: driving the silicon carbide substrate 100 to translate relative to the modifying device along a first radial direction of the carbon surface 12 so that the action position forms a first line segment trajectory passing through the symmetry center of the middle surface area, the first line segment trajectory perpendicularly intersecting the axis of the silicon carbide substrate 100 and equally dividing the middle surface area;

[0139] Step B4: rotating the silicon carbide substrate 100 by a preset angle with the axis of the silicon carbide substrate 100 as the rotation center, while keeping the direction of the carbon surface 12 unchanged;

[0140] Step B5: driving the silicon carbide substrate 100 to translate relative to the modified device along the second radial direction of the carbon surface 12 so that the action position forms a second line segment trajectory passing through the symmetry center of the middle surface area, and the second line segment trajectory intersects the axis of the silicon carbide substrate 100 perpendicularly and divides the middle surface area equally.

[0141] The first line segment trajectory and the second line segment trajectory are two radial line segments, respectively, and their intersection is located on the axis of the silicon carbide substrate 100. It can be understood that in order to form multiple modified points arranged in a radial pattern within the intermediate surface area, the line segment trajectory passed by the active position is not limited to the first line segment trajectory and the second line segment trajectory. The line segment trajectory passed by the active position is perpendicular to the axis of the silicon carbide substrate 100.

[0142] In some embodiments, the peripheral surface region and the plurality of modified points generated in the peripheral surface region form a peripheral layer 132, and the plurality of modified points are arranged in a radially spoke-like pattern within the peripheral surface region; step D further includes:

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

[0144] Step D4: rotating the silicon carbide substrate 100 by a predetermined angle with the axis of the silicon carbide substrate 100 as the rotation center, while keeping the orientation of the carbon surface 12 unchanged;

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

[0146] The third and fourth line segments are two radial line segments, respectively, whose intersection lies on the axis of the silicon carbide substrate 100. It will be appreciated that, in order to form multiple modified points arranged in a radial pattern within the peripheral surface, the line segments traversed by the active position are not limited to the third and fourth line segments; all line segments traversed by the active position intersect perpendicularly with the axis of the silicon carbide substrate 100.

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

[0148] Step B6: driving the silicon carbide substrate 100 to rotate around the axis for at least one revolution, so that the action position forms a first circular track around the axis of the silicon carbide substrate 100;

[0149] Step B7: driving the silicon carbide substrate 100 to move in a direction parallel to the carbon surface 12 to change the distance between the action position and the axis of the silicon carbide substrate 100;

[0150] Step B8: driving the silicon carbide substrate 100 to rotate around the axis for at least one revolution, so that the action position forms a second circular orbit around the axis of the silicon carbide substrate 100 .

[0151] It can be understood that in order to form multiple modified points arranged in concentric circles in the middle surface area, the circular trajectory passed by the action position is not limited to the first circular trajectory and the second circular trajectory, and the other circular trajectories passed by the action position are all centered on the axis of the silicon carbide substrate 100.

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

[0153] Step D6: driving the silicon carbide substrate 100 to rotate around the axis for at least one revolution, so that the action position forms a third circular orbit around the axis of the silicon carbide substrate 100;

[0154] Step D7: driving the silicon carbide substrate 100 to move in a direction parallel to the carbon surface 12 to change the distance between the action position and the axis of the silicon carbide substrate 100;

[0155] Step D8: driving the silicon carbide substrate 100 to rotate around the axis for at least one revolution, so that the action position forms a fourth circular orbit around the axis of the silicon carbide substrate 100 .

[0156] It can be understood that in order to form multiple modified points arranged in concentric circles within the outer surface area, the circular trajectory passed by the action position is not limited to the third circular trajectory and the fourth circular trajectory, and the other circular trajectories passed by the action position all have the axis of the silicon carbide substrate 100 as the axis.

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

[0158] Step A includes: step A3, adjusting the laser focus of the laser generator so that the laser focus falls on the middle surface area inside the silicon carbide substrate 100;

[0159] Step C includes: Step C3, adjusting the laser focus of the laser generator so that the laser focus is transferred from one of the middle surface areas to one of the peripheral surface areas along the vertical direction of the carbon surface 12.

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

[0161] See Figure 7 、 Figure 8 and Figure 9 The thickness of the silicon carbide substrate 100 is determined by Figure 7 、 Figure 8 and Figure 9 The distribution ratio of the middle layer 131 and the outer layer 132 is as follows: Figure 7 、 Figure 8 and Figure 9 The order of increasing; Figure 7 and Figure 8 In the state shown, the combined 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, the total force of the modified layer 13 acting on the silicon carbide substrate 100 is less than Figure 7 The resultant force of the modified layer 13 acting on the silicon carbide substrate 100 in the state is due to Figure 8 The silicon carbide substrate 100 is shown in FIG. Figure 7 The silicon carbide substrate 100 is shown to be further thinned, and the intermediate layer 131 closest to the back of the silicon carbide substrate 100 is cut thinner.

[0162] The various technical features of the above-described embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0163] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. Any appropriate changes and modifications to the above embodiments fall within the scope of the present invention as long as they are within the spirit of the present invention.

Claims

1. A silicon carbide substrate comprising 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, wherein the modified layer includes one or more intermediate layers and at least one peripheral layer. When there are multiple intermediate layers, the multiple intermediate layers are sequentially arranged along the vertical direction of the carbon surface; when there are multiple peripheral layers, the multiple peripheral layers are sequentially arranged along the vertical direction of the carbon surface; Along the vertical direction of the carbon surface, the middle layer and the outer layer are staggered; The image of the intermediate layer projected onto the carbon surface is the intermediate projection, and the outline of the intermediate projection and the edge of the carbon surface form a peripheral area surrounding the intermediate projection. The pattern of the outer layer projected onto the carbon surface is a outer projection, and the outer projection is located in the outer region and surrounds the middle projection.

2. The silicon carbide substrate according to claim 1, wherein The modified layer forms a plurality of modified layer groups repeatedly arranged along a vertical direction of the carbon surface, and each of the modified layer groups includes at least one intermediate layer and at least one peripheral layer.

3. The silicon carbide substrate according to claim 1, wherein The intermediate layers and the outer layers are alternately arranged layer by layer along the vertical direction of the carbon surface; or, the intermediate layers and the outer layers are alternately arranged in groups along the vertical direction of the carbon surface.

4. The silicon carbide substrate according to claim 1, wherein 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 diameter of the silicon carbide substrate is , 0.1≤ ≤0.8,0.2≤ ≤0.5,0.2≤ ≤0.

8.

5. The silicon carbide substrate according to any one of claims 1 to 4, wherein In the vertical direction of the carbon surface, the distance between any two adjacent modified layers is not less than 5 and no more than 50 and / or, The modified layer has scattered modified points within its surface area, and the distance between any two modified points is not less than 100 and no more than 1000 , in each of the modified layers, the modified points are arranged in an array, concentric circles, or radial stripes; and / or, The distance between the modified layer closest to the carbon surface and the carbon surface is , the distance between the modified layer farthest from the carbon surface and the carbon surface is , 10 ≤ ≤100 , 50 ≤ ≤250 .

6. A method for preparing a silicon carbide substrate, the method being used to prepare the silicon carbide substrate according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: Step A, adjusting the action position of the modification device to the processing surface area in the silicon carbide substrate so that the action position falls within one of the middle surface areas of the processing surface area at least once, or falls within multiple middle surface areas of the processing surface area multiple times; Step B, driving the silicon carbide substrate to move relative to the modification device parallel to the carbon surface, so that the action position generates multiple modified points in one of the middle surface areas of step A, or generates multiple modified points in multiple middle surface areas of step A; The processing surface area is located between the carbon surface and the silicon surface. The figure of the intermediate surface area projected on the carbon surface is the intermediate projection. The outline of the intermediate projection and the edge of the carbon surface form a peripheral area surrounding the intermediate projection. Multiple intermediate surface areas are arranged in sequence along the vertical direction of the carbon surface. Step C, shifting the action position of the modification device along the vertical direction of the carbon surface so that the action position falls within one of the peripheral surface areas of the processing surface area at least once, or falls within multiple peripheral surface areas of the processing surface area multiple times; Step D: driving the silicon carbide substrate to move relative to the modification device parallel to the carbon surface, so that the action position generates multiple modified points in one of the peripheral surface areas of step C, or generates multiple modified points in multiple peripheral surface areas of step C; The figure of the outer surface area projected onto the carbon surface is the outer projection. The outer projection is located in the outer area and surrounds the middle projection. Along the vertical direction of the carbon surface, multiple outer surface areas are arranged in sequence, and the middle surface area and the outer surface area are staggered.

7. The method for preparing a silicon carbide substrate according to claim 6, wherein: In step A, making the action position fall within one of the middle surface areas of the processing surface area at least once, or making the action position fall within multiple middle surface areas of the processing surface area multiple times includes: Step A1, controlling the action position of the modification device to move closer to the carbon surface, and to move from one of the peripheral surface areas to one of the middle surface areas; Step A2, controlling the action position of the modified device to migrate close to the carbon surface, and migrate from one intermediate surface region to another intermediate surface region; In the step C, shifting the action position of the modification device along the vertical direction of the carbon surface includes: Step C1, controlling the action position of the modification device to move closer to the carbon surface, and to move from one of the middle surface areas to one of the peripheral surface areas; Step C2: Controlling the action position of the modification device to migrate closer to the carbon surface, and migrate from one peripheral surface area to another peripheral surface area.

8. The method for preparing a silicon carbide substrate according to claim 7, wherein: Step A1 includes: moving the action position from one of the middle surface areas in a direction perpendicular to the carbon surface After reaching the adjacent middle surface area, 5 ≤ ≤50 ; Step C1 includes: moving the action position from one of the middle surface areas in a direction perpendicular to the carbon surface After reaching a certain distance, it reaches an adjacent peripheral area; Step C2 includes: moving the action position from one of the peripheral areas along the direction perpendicular to the carbon surface distance and then reaches another adjacent outer surface area.

9. The method for preparing a silicon carbide substrate according to claim 6, wherein: Repeat step A, step B, step C, and step D several times.

10. The method for preparing a silicon carbide substrate according to any one of claims 6 to 9, wherein: The method for preparing a silicon carbide substrate further comprises: Step E1: first adjust the working position of the modified device to the first processing surface area in the silicon carbide substrate. The first processing surface area is the one farthest from the carbon surface among the multiple processing surface areas. The distance from the first processing surface area to the carbon surface is , 50 ≤ ≤250 ; Step E2: driving the silicon carbide substrate to move parallel to the carbon surface relative to the modification device, and first generating multiple modification points in the first processing surface area in step E1, so that the first processing surface area forms the first modification layer relative to other processing surface areas.

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