Silicon carbide crystal substrate having an optimal crystal plane orientation for reducing cracks and method for producing the same

Abstract

The present invention relates to a silicon carbide crystal substrate having an optimal crystal plane orientation for reducing cracks and a method for producing the same, and in particular provides a single-crystal 4H-SiC semi-finished product in which a specific orientation of its crystal structure is set to reduce or even eliminate the occurrence of cracks or fissures during machining and a method for producing the same. The single-crystal 4H-SiC substrate having a longitudinal axis and at least partially curved side surfaces parallel to the longitudinal axis is characterized in that the crystal structure of the 4H-SiC substrate is oriented with respect to the longitudinal axis such that at each position on the side surface of the semi-finished product there is a line segment that intersects at least a predetermined minimum number of parallel cleavage planes of the {1010} type per unit length, wherein the line segment is defined by a plane tangent to the side surface at the position.

Description

Technical Field

[0001] The present invention relates to bulk single-crystalline silicon carbide (SiC) having a specific crystal structure orientation for reducing or eliminating the occurrence of cracks or fissures during machining, and to a method for producing a single-crystalline SiC substrate having such an orientation. Background Art

[0002] Silicon carbide (SiC) substrates are commonly used for the production of electronic components with a wide range of applications, such as power electronics, radio frequency, and optoelectronic applications. They are typically produced from bulk SiC single crystals, which can be grown using standard methods (e.g., physical vapor deposition (PVT)) and suitable source materials. The SiC substrates are then produced from the grown crystals by cutting the wafers using a wire saw and then refining the wafer surfaces in a multi-stage polishing step. In the subsequent epitaxial process, a single-crystalline thin layer of a semiconductor material (e.g., SiC, GaN (gallium nitride)) is then deposited onto the SiC substrate. The properties of these epitaxial layers and the properties of the components made therefrom mainly depend on the quality of the underlying SiC substrate.

[0003] A standard method for producing SiC crystals by physical vapor deposition is described in patent US 8,865,324 B2. The bulk SiC crystals produced by this method are then oriented, for example, using X-ray radiation, such that the crystal structure has the orientation required for further machining. For example, by various surface treatment steps of the bulk SiC crystal (e.g., by grinding), the desired substrate diameter is then set on the single-crystalline SiC semi-finished product, one or more orientation planes (OF) are ground on its side surface, and the front surface of the machined crystal cylinder is prepared for the wafer separation process (e.g., wire saw). As Figure 1 shown, the SiC semi-finished product 100 produced by such machining of the bulk SiC crystal is an oriented cylinder having a diameter equal to the diameter of the future substrate wafer, and the cylinder has one or two orientation planes 110 (or notches) defined on the side surface 130 of the cylinder and has parallel and flat front surfaces 120a, 120b.

[0004] The SiC semi-finished product 100 is then divided into individual raw single-crystalline SiC substrates, for example, using a wire saw process. After quality control, the single-crystalline SiC substrates will undergo further machining. For example, the following machining sequence can be used. After machining of the edges, a single-stage or multi-stage grinding or polishing process is performed to remove the (one or more) damaged layers formed during the substrate separation process and gradually reduce the substrate roughness. Then a chemical mechanical polishing process (CMP) is applied on one or both sides of the substrate to finally finish the corresponding (one or more) surfaces.

[0005] Known single-crystalline SiC and substrates made therefrom exhibit high brittleness (or correspondingly low ductility). During the multi-stage machining of bulk SiC crystals and the above SiC substrates, they are subjected to significant mechanical forces. In particular, cracks or fissures can easily form along preferred crystal cleavage planes (for example, in the case of 4H-SiC, for type and type), and cause damage or destruction of SiC semi-finished cylinders and / or substrates. In particular, in mechanical processes where mechanical forces are applied radially (i.e., perpendicular to the outer diameter), the increased likelihood of cracking along the cleavage plane results in cracks in the crystals and substrates, leading to an undesired reduction in yield.

[0006] In the machining of single-crystalline SiC semi-finished cylinders, setting the outer diameter by grinding is the most critical process step because the large forces exerted by the grinding tool (such as a grinding wheel) are applied perpendicular to the outer diameter of the cylinder.

[0007] In the machining of single-crystalline SiC substrates, both the steps of machining the substrate edge and polishing are crucial. For example, when chamfering the substrate edge, a cup-shaped grinding wheel is used to apply a radial force to the outer diameter of the substrate. During polishing where the substrate is guided in a rotor disk, radial forces are similarly applied by these rotor disks to the outer diameter of the substrate.

[0008] Therefore, special attention must be paid to the high brittleness of the SiC material and the cleavage crystal planes present during the machining of the corresponding bulk crystals and substrates.

[0009] So far, the prior art has not solved the problem of the anisotropy of the mechanical properties of the SiC lattice, which is why in practice a certain amount of waste of bulk crystals or substrates caused by cracks occurring during machining is always generally accepted. However, these have a negative impact on the yield of the entire process chain.

[0010] When machining the outer periphery of a SiC semi-finished cylinder, by adjusting the parameters of the machining step itself (such as the applied force or grinding speed), the occurrence of cracks or fissures can be reduced within certain limits, but they cannot be completely eliminated. However, this has a negative impact on other process parameters, such as an increase in the process duration and cost. Fracture or cracking during the machining of the original SiC substrate obtained after wire sawing of a SiC semi-finished cylinder (such as during edge chamfering, mechanical grinding, mechanical or chemical mechanical polishing, etc.) can also be reduced by adjusting the process parameters, but cannot be completely avoided. Such adjustments also have an adverse effect on other process parameters, such as a significant increase in the duration of substrate machining.

[0011] Some solutions have been attempted to reduce the amount of defective SiC semi-finished cylinders and substrates.

[0012] For example, patent application DE102009048868 describes a thermal post-treatment method for SiC crystals, which allows for reducing the stress in the crystals and thus also reducing the sensitivity of the SiC crystals to cracking.

[0013] Patent CN110067020A describes a method for reducing the inherent stress within a crystal that already exists during production, which in turn should reduce the sensitivity of the crystal to cracking.

[0014] However, none of these prior art methods take into account the specific requirements regarding the crystal orientation for the machining of single-crystalline SiC semi-finished products or substrates due to the anisotropy of the mechanical properties of single-crystalline SiC semi-finished products or substrates. In addition, these prior art methods do not consider the influence of the crystal orientation on the cracking sensitivity of SiC semi-finished products and / or SiC substrates. Both methods describe a reduction in internal stress and, therefore, a general reduction in cracks due to the reduction of crystal stress.

[0015] However, no solution for reducing the occurrence of cracks is disclosed. Depending on the mechanical forces applied, cracks may even occur on low-stress or stress-free SiC semi-finished products or SiC substrates during mechanical machining.

[0016] Therefore, there is a need for a solution that allows for effectively reducing the amount of defective SiC semi-finished products and / or SiC substrates resulting from the occurrence of cracks during their mechanical machining, without significantly increasing the overall cost and time of mechanical machining, while improving the quality and yield of SiC semi-finished products and SiC substrates. Summary of the Invention

[0017] The present invention has been made in view of the deficiencies and disadvantages of the prior art, and the object of the present invention is to provide a single-crystalline 4H-SiC substrate and a method for producing such a single-crystalline 4H-SiC substrate, which has improved mechanical robustness against the forces applied during the production and / or mechanical machining of the outer surface of the 4H-SiC substrate.

[0018] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the present invention are the subject matter of the dependent claims.

[0019] A single-crystalline 4H-SiC substrate having improved cleavage-resistant mechanical robustness, wherein the 4H-SiC substrate having a substrate axis and at least partially curved side surfaces parallel to the substrate axis is characterized in that the crystal structure of the 4H-SiC substrate lattice is oriented with respect to the substrate axis such that at each position on the substrate side surface there is a line segment that has at least a predetermined minimum number per unit length of The parallel cleavage planes of the type intersect, wherein the line segment is defined by a plane tangent to the side surface at the position.

[0020] According to a further improvement, a predetermined minimum number per unit length of the parallel cleavage planes of the type is at least 1000 planes per millimeter; and / or the longitudinal axis is the axis of symmetry of a cylinder defined by the curved portion of the at least partially curved side surface of the 4H-SiC substrate.

[0021] According to a further improvement, the main axis of the basal plane of the 4H-SiC crystal structure is inclined at a first inclination angle relative to the substrate axis towards the direction, and / or the first inclination angle is 4°, with a tolerance of ±0.5°; and / or the main axis of the basal plane of the 4H-SiC crystal structure is inclined at a second inclination angle relative to the substrate axis towards the direction, wherein the second inclination angle is estimated based on the distance between the parallel cleavage planes of the type, thereby producing the at least predetermined minimum number per unit length of the parallel cleavage planes of the type that intersect the line segment, and / or the second inclination angle is a value selected from the interval [0.015°; 0.153°] or preferably 0.023°.

[0022] According to a further improvement, the single-crystal 4H-SiC substrate further includes a first front surface and a second front surface; wherein the first front surface and the second front surface are respectively perpendicular to the at least partially curved side surface of the 4H-SiC substrate, and / or one or both of the first front surface and the second front surface are perpendicular to the substrate axis.

[0023] In a further improvement, the at least partially curved side surface has a curved portion that defines a cylindrical surface using the substrate axis, and the curved portion has its axis of symmetry, wherein the outer diameter of the cylindrical surface substantially corresponds to a given diameter of a substrate wafer obtained by slicing the 4H-SiC substrate, and / or the outer diameter of the cylindrical surface is 150.0 mm ± 0.5 mm, 200.0 mm ± 0.5 mm or 250.0 mm ± 0.5 mm; and / or the thickness of the single-crystal 4H-SiC substrate is greater than 250 μm, or preferably greater than 325 μm, and / or the nitrogen doping of the single-crystal 4H-SiC substrate is greater than 1×10 18 cm -3 and / or the single-crystal 4H-SiC substrate has a notch or an orientation plane with a length of 47.5 mm ± 1.0 mm.

[0024] The present invention also provides a method for producing a single-crystalline 4H-SiC substrate having improved anti-cleavage mechanical robustness, the single-crystalline 4H-SiC substrate having a substrate axis and at least partially curved side surfaces parallel to the substrate axis, the method comprising: performing a process of setting a predetermined orientation of the 4H-SiC crystal structure on the 4H-SiC substrate relative to the substrate axis such that at each position on the side surface of the 4H-SiC substrate there is a line segment that intersects at least a predetermined minimum number of parallel cleavage planes of a type, wherein the line segment is defined by a plane tangent to the side surface at that position.

[0025] In a further improvement, the predetermined orientation of the 4H-SiC crystal structure is such that the predetermined minimum number of parallel cleavage planes of a type per unit length is at least 1000 planes per millimeter of line segment length.

[0026] In a further improvement, the method further comprises estimating the predetermined orientation in order to produce at least the predetermined minimum number of parallel cleavage planes of a type that intersect the line segment.

[0027] According to a further improvement, the process of setting the predetermined orientation of the 4H-SiC crystal structure on the 4H-SiC substrate comprises: providing a single-crystalline 4H-SiC semi-finished product for producing at least one original 4H-SiC substrate, wherein the 4H-SiC semi-finished product has been set with the predetermined orientation of the 4H-SiC crystal structure relative to the substrate axis of the 4H-SiC semi-finished product and the reference surface of the single-crystalline 4H-SiC semi-finished product; mounting the 4H-SiC semi-finished product having the reference surface onto a support surface; and cutting the mounted 4H-SiC semi-finished product in a direction transverse to or parallel to the support surface to obtain at least one original 4H-SiC substrate.

[0028] In a further improvement, the process of setting the predetermined orientation of the 4H-SiC crystal structure on the 4H-SiC substrate comprises: providing a single-crystalline 4H-SiC semi-finished product for producing at least one original 4H-SiC substrate; spatially orienting the 4H-SiC crystal structure by tilting the

[0001] axis of the basal plane relative to a predetermined alignment axis in a predetermined direction and amount; and after spatially orienting the 4H-SiC crystal structure, cutting the 4H-SiC semi-finished product in a direction substantially transverse to the predetermined alignment axis to obtain at least one original 4H-SiC substrate.

[0029] According to a further improvement, the method further includes: determining, by performing an angle measurement, the crystal orientation of the 4H-SiC crystal structure in the original 4H-SiC substrate relative to the front surface of the original 4H-SiC substrate; if the determined crystal orientation deviates from a predetermined orientation relative to the substrate axis of the original 4H-SiC substrate, spatially orienting the original 4H-SiC substrate such that the

[0001] axis of the basal plane in the 4H-SiC crystal structure is tilted in a direction and by an amount predetermined relative to a predetermined alignment axis, and spatially orienting the crystal orientation of the 4H-SiC crystal structure; machining the outer surface of the spatially oriented 4H-SiC single crystal wafer with reference to the alignment axis to form at least one of the following: the at least partially curved side surface substantially parallel to the alignment axis, and at least one front surface substantially orthogonal to the alignment axis; wherein the substrate axis of the machined 4H-SiC substrate substantially corresponds to or is parallel to the alignment axis for the spatial orientation of the 4H-SiC crystal structure.

[0030] In a further improvement, spatially orienting the 4H-SiC crystal structure at the predetermined tilt angle includes: orienting the basal plane of the 4H-SiC crystal structure in an initial orientation; tilting the basal plane from the initial orientation to a first orientation at a first tilt angle in a direction of the 4H-SiC crystal structure; and tilting the basal plane from the first orientation to a second orientation at a second tilt angle in a direction of the 4H-SiC crystal structure or in a direction of; wherein in the initial orientation, the basal plane is substantially perpendicular to the predetermined alignment axis. direction by the first tilt angle from the initial orientation to the first orientation; and tilting the basal plane from the first orientation to the second orientation at the second tilt angle in a direction of the 4H-SiC crystal structure or in a direction of; wherein in the initial orientation, the basal plane is substantially perpendicular to the predetermined alignment axis. direction or direction; wherein in the initial orientation, the basal plane is substantially perpendicular to the predetermined alignment axis.

[0031] According to a further improvement, the first tilt angle is 4°, with a tolerance of ±0.5°; and / or wherein the second tilt angle is estimated based on the distance between the parallel cleavage planes of the type, thereby producing at least the predetermined minimum number of parallel cleavage planes of the type per unit length intersecting the line segment, and / or the second tilt angle is a value selected from the interval [0.015°; 0.153°] or preferably 0.023°; and / or the orientation of the 4H-SiC crystal structure tilted at the first tilt angle and / or the second tilt angle is verified by angle measurement. type of the parallel cleavage planes to estimate the second tilt angle, thereby producing at least the predetermined minimum number of parallel cleavage planes of the type per unit length intersecting the line segment, and / or the second tilt angle is a value selected from the interval [0.015°; 0.153°] or preferably 0.023°; and / or the orientation of the 4H-SiC crystal structure tilted at the first tilt angle and / or the second tilt angle is verified by angle measurement. type of parallel cleavage planes, and / or the second tilt angle is a value selected from the interval [0.015°; 0.153°] or preferably 0.023°; and / or the orientation of the 4H-SiC crystal structure tilted at the first tilt angle and / or the second tilt angle is verified by angle measurement.

[0032] According to a further improvement, the spatial orientation process includes: orienting the basal plane of the 4H-SiC crystal structure in an initial orientation; rotating the basal plane around the initial orientation in a clockwise direction by a predetermined rotation angle; tilting the rotated basal plane at a third tilt angle in a direction of the 4H-SiC crystal structure; and wherein in the initial orientation, the basal plane is substantially perpendicular to the alignment axis. direction at the third tilt angle; and wherein in the initial orientation, the basal plane is substantially perpendicular to the alignment axis.

[0033] According to a further improvement, the spatial orientation process includes: orienting the basal plane of the 4H-SiC crystal structure in an initial orientation; rotating the basal plane counterclockwise by a predetermined rotation angle about the initial orientation; tilting the rotated basal plane by a third tilt angle towards the direction of the 4H-SiC crystal structure; and wherein in the initial orientation, the basal plane is substantially perpendicular to the alignment axis.

[0034] In a further improvement, the predetermined rotation angle is 0.33° or a value within the range of [0.22°, 2.19°], and / or the third tilt angle is 4°, with a tolerance of ±0.5°; and / or the orientation of the 4H-SiC crystal structure after rotating the predetermined rotation angle and / or tilting the third tilt angle is verified by angle measurement.

[0035] To explain the principles of the present invention, the drawings are incorporated and form a part of the specification. The drawings should not be construed as limiting the present invention to the examples shown and described of how the present invention can be obtained and used. Description of the Drawings

[0036] Further features and advantages will become apparent from the following and more detailed description of the present invention as shown in the drawings, wherein:

[0037] Figure 1 is a schematic perspective view of a single-crystal SiC semi-finished product;

[0038] Figure 2 is a schematic view of a conventional 4H-SiC semi-finished product or substrate with an on-axis orientation (viewed from the top, front), wherein the basal plane (0001) is parallel to the front and the crystal orientation

[0001] is inclined 0° relative to the cylindrical symmetry axis C; two sets of cleavage planes of the type and type are depicted, the and crystal planes, the and crystal planes;

[0039] Figure 3A is a schematic top view (viewed from the front) of a conventional 4H-SiC substrate with an off-axis orientation of a standard 4°, wherein the basal plane (0001) of the 4H-SiC crystal is tilted by an angle δ of 4° towards the direction relative to the front of the 4H-SiC substrate; the short arrow in the inset depicts the Figure 2 vector component of the

[0001] direction on the plane of;

[0040] Figure 3B is Figure 3AThe schematic side view of the 4H-SiC substrate shown when viewed from the side containing the crystal orientation, and depicts the basal plane (0001) and the corresponding

[0001] axis tilted by an angle δ of 4° towards the direction (i.e., towards the direction parallel to the main plane OF in Figure 3A );

[0041] Figure 4A is a schematic side view of a 4H-SiC semi-finished product with a standard deviation of 4° in orientation when viewed from the side containing the crystal orientation (i.e., one side of the main plane OF), and depicts the basal plane (0001) and the corresponding

[0001] crystal orientation tilted by an inclination angle δ of 4° towards the initial direction;

[0042] Figure 4B is another schematic side view of the 4H-SiC semi-finished product shown in when viewed from the side opposite to the initial Figure 4A direction, and depicts the cleavage plane parallel to the central symmetry axis C of the 4H-SiC cylinder;

[0043] Figure 5 is a top view depicting the component of the mechanical force F applied to the side of the 4H-SiC semi-finished product (or substrate) by the grinding wheel;

[0044] Figure 6 is a side view depicting the radial mechanical force applied to the 4H-SiC semi-finished product (or substrate) by the grinding wheel;

[0045] Figure 7 is another schematic side view of the 4H-SiC semi-finished product with a standard deviation of 4° in orientation when viewed from the direction (i.e., viewed from one side of the main plane OF), and depicts the intersection of the force line segment L with the crystal plane ;

[0046] Figure 8 is now another schematic side view of the 4H-SiC semi-finished product shown in when viewed along the Figure 7 direction, and depicts the intersection of another force line segment L with the crystal plane ;

[0047] Figure 9A is a schematic side view of a 4H-SiC semi-finished product with a predetermined crystal orientation according to an exemplary embodiment (viewed along the direction), wherein the basal plane (0001) is tilted by a first inclination angle δ1 towards the direction and additionally tilted counterclockwise towards tilted at a second tilt angle δ2 in the direction; also depicted is an exemplary force line segment L along which a radial force can be applied to the side surface of the 4H-SiC semi-finished product during machining;

[0048] Figure 9B is Figure 9A Another schematic side view of the 4H-SiC semi-finished product shown, and depicting the tilting of the basal plane (0001) and the cleavage plane due to tilting the second tilt angle δ2 of (viewed from the direction);

[0049] Figure 10A is a schematic side view of a 4H-SiC semi-finished product having a predetermined crystal orientation according to another exemplary embodiment (viewed along the direction), wherein the basal plane (0001) is tilted at a first tilt angle δ1 towards the direction and at a second tilt angle δ2 towards the direction;

[0050] Figure 10B is Figure 10A Another schematic side view of the 4H-SiC semi-finished product (or substrate) shown (viewed along the direction), and depicting the tilting of the basal plane (0001) and the cleavage plane due to tilting the second tilt angle δ2 ;

[0051] Figure 11 Schematically shows a support structure for a single-crystal SiC semi-finished product according to an embodiment, which is used to transfer a preset crystal orientation from the SiC semi-finished product to individual SiC wafers during a wafer separation process by referring to the cylindrical side surface of the SiC semi-finished product;

[0052] Figure 12 Schematically shows another support structure for a single-crystal SiC semi-finished product according to an embodiment, which is used to transfer a preset crystal orientation from the SiC semi-finished product to individual SiC wafers during a wafer separation process by referring to one of the front sides of the SiC semi-finished product;

[0053] Figure 13A is a schematic side view of a 4H-SiC substrate having a predetermined crystal orientation for improving mechanical robustness according to an exemplary embodiment (viewed from the side in the direction), and the predetermined crystal orientation is similar to the predetermined crystal orientation of the 4H-SiC semi-finished product depicted in Figure 9A - Figure 9B ; and

[0054] Figure 13B is Figure 13AAnother schematic side view of the 4H-SiC substrate as shown, and depicting the inclination of the basal plane (0001) and the cleavage plane due to the inclination of the second inclination angle δ2 from direction of observation).

[0055] It should be noted that since this application will discuss the atomic scale, the dimensions and relative angles shown in the drawings are for illustrative purposes only and are not drawn to scale. Detailed Description

[0056] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

[0057] The basic principle of the present invention is that the inventors have recognized that by setting a given orientation of the crystal structure relative to an external reference surface (such as the front and / or side surfaces) of the SiC crystal and / or the SiC substrate, cracks or fissures that occur in the SiC crystal and substrate during various mechanical processes can be significantly reduced or even eliminated, which improves their mechanical robustness without affecting the quality of the epitaxial layer to be grown on the single-crystal SiC substrate.

[0058] Therefore, the present invention provides an optimal orientation of the crystal planes for the SiC crystal and substrate, which ensures higher mechanical robustness and increased yield in machining.

[0059] In SiC crystals, cracks or fissures are prone to form along preferred cleavage planes (such as the type and type of crystal planes for 4H-SiC single crystals), resulting in damage or destruction of the single-crystal SiC semi-finished products and final products. In particular, during the rapid application of mechanical force along the radial direction (i.e., perpendicular to the side surface of the SiC crystal cylinder), the higher sensitivity to cracking along the cleavage plane can cause cracking of the SiC crystal and substrate, leading to an undesired corresponding reduction in yield.

[0060] For example, Figure 2 depicts the orientation of the type and type of cleavage planes of the polar 4H-SiC semi-finished product 200 (or 4H-SiC substrate) having an on-axis crystal orientation. In Figure 2In the shown axial orientation, the basal plane (0001) of the 4H-SiC crystal structure is parallel to one of the front faces 220 of the cylinder, and thus, the crystallographic direction

[0001] forms an angle of 0° with the longitudinal axis C of the 4H-SiC cylinder 200. The longitudinal axis C mentioned hereinafter is defined as the symmetry axis of the cylindrical surface defined by the curved side surface of the 4H-SiC semi-finished product or the 4H-SiC substrate. Figure 2 shows the Si side (0001) of the polar 4H-SiC semi-finished product or substrate when observed from the corresponding front face 220 (e.g., Figure 1 the front face 120a in . The main orientation plane (OF) is defined in the crystallographic direction . A secondary plane in the crystallographic direction can be provided selectively. A notch (i.e., a lateral indentation in the substrate wafer for precise positioning in a semiconductor manufacturing plant) can be provided in the Figure 2 direction instead of the main plane OF. Furthermore, depicts two types of cleavage planes, which show three symmetry-equivalent crystal planes of the type and three symmetry-equivalent crystal planes of the and crystal plane and are included in the type. The type specifies the set of crystal planes that can be obtained by symmetry operations from the plane, which describes the ideal crystal structure of SiC (point group 6nn), and thus, includes the planes type and type, all cleavage planes intersect the front face of the Si side (0001) of the 4H-SiC semi-finished product 200 and the opposite C side (not shown) at an angle of 90°. and type cleavage planes also intersect the side surface of the 4H-SiC semi-finished product 200 at right angles, which means that the 4H-SiC semi-finished product 200 will be prone to cracking when a radial force is applied along the depicted cleavage planes.

[0061] are depicted in Figure 3A and Figure 3B in 001 . An example of a 4H-SiC substrate 300 having an off-axis orientation of 4° from the standard basal plane (0001) in the direction. This orientation of 4° has become the standard orientation for 4H-SiC substrates used in the prior art because it allows for optimal quality in epitaxial layers grown thereon and in subsequently processed components. Figure 3A Depicted is a standard 4° off-axis orientation of a 4H-SiC substrate 300 when viewed from the top, front side (ie, from the Si side (0001)), showing the crystal direction and along the front side 320a The inclination of the axis is given by Figure 3A The short arrows in the illustration of , depict the vector component along the

[0001] axis of the front face 320a. The principal plane is generally defined as indicating Directions, although markers can be used Direction notch instead. Can also be provided in Direction of the secondary plane. Figure 3B yes Figure 3A The 4H-SiC substrate 300 depicted in FIG. Side view when viewed from the direction (one side of the principal plane OF). Figure 3B It can be seen that the basal plane (0001) of the 4H-SiC crystal faces the crystal direction The plane parallel to the front surface 320 a is tilted, and the corresponding crystal axis

[0001] is tilted at a tilt angle δ of 4° (+ / −0.5°) relative to the central axis C of the 4H—SiC substrate.

[0062] As mentioned above, the base plane (0001) faces The 4° tilt in the direction allows for optimal step flow during epitaxy, thus ensuring the best quality of the epilayers subsequently grown on the 4° off-axis substrate. This tilt of the basal plane (0001) and the main axis

[0001] is also reflected in the crystal orientation of some cleavage planes. For example, in the case of an on-axis orientation Figure 2 Depicted in Type and Five of the six cleavage planes of the type are no longer orthogonal to the front side 320a, 320b of the 4H-SiC substrate having an off-axis orientation of 4°, and therefore no longer intersect the cylinder side surface 330 at a right angle. Still intersecting the front side 320a, 320b of the 4H-SiC substrate 300 at an angle of 90°, and remaining parallel to the longitudinal axis C. On the other hand, the cleavage plane The largest change in crystal orientation relative to the front side 320a is shown.

[0063] A similar situation occurs in a single-crystalline 4H-SiC semi-finished product 400 with an off-axis orientation of a standard 4°, for example as Figure 4A - Figure 4B shown in. Figure 4A Shows a side view of the 4H-SiC semi-finished product 400 viewed from the direction (i.e., from one side of the main plane OF), and depicts the crystal orientations and with respect to the front face 420a (on the Si side (0001)) and the central axis C of the cylinder, as well as the cleavage plane tilt. As can be seen from Figure 4A , the cleavage plane no longer intersects the front face 420a at a right angle and, therefore, it is no longer aligned parallel to the central axis C, but rather exhibits a 4° tilt with respect to the central axis C due to the 4° off-axis orientation of the basal plane (0001) and the corresponding

[0001] crystal axis. On the other hand, the direction remains transverse to the central axis C.

[0064] Figure 4B Shows the Figure 4A 4H-SiC semi-finished product shown in now viewed from a direction 90° to the crystal orientation (i.e., from the side opposite to the direction in front of the tilted basal plane (0001)). As can be seen from Figure 4B , the direction remains transverse to the central axis C of the 4H-SiC semi-finished product 400, and the cleavage plane is the only crystal plane that does not change its orientation as the basal plane (0001) tilts 4° towards the direction. Therefore, the cleavage plane continues to intersect the front face 420a (and 420b) at a right angle and remains parallel to the central axis C of the cylinder. The crystal orientation is no longer perpendicular to the central axis C because it tilts 4° downward with respect to the front face 420a (which is shown in Figure 4B by the vertical shift of the symbol representing the tail of the vector in the direction). The intersection of the parallel basal plane (0001) with the side face 430 of the 4H-SiC semi-finished product 400 is represented by a horizontal line in Figure 4B . Except for the plane, all other remaining corresponding -type and -type cleavage planes change their orientation with respect to the front face 420a after the 4° tilt of the basal plane (0001), and the corresponding tilt angles fall between the maximum 4° change exhibited by the cleavage plane and the zero change of the cleavage plane .

[0065] However, whether it is an on-axis orientation or an off-axis orientation of 4°, the 4H-SiC semi-finished product or the 4H-SiC substrate is still prone to cracking during machining, especially when a radial mechanical force is applied in the region where the cleavage plane intersects its corresponding cylindrical surface with the symmetry axis C aligned, just like the cleavage plane in the above case.

[0066] As Figure 5 shown, during the machining of a single-crystal SiC semi-finished product (or substrate), it can be assumed that, in a first approximation, the tool used during machining (e.g., grinding) applies a mechanical force F along a line segment L (force line segment) on the surface of the single crystal, and the mechanical force F propagates radially into the single crystal. The decisive factor for the cleavage aspect is the intensity of the force applied inwardly to the single-crystal SiC semi-finished product (i.e., the radial component F rad ) of the total force F. The tangential force component (F tang ) that may occur during machining can be ignored for evaluating its effect on cleavage. The length of the line segment L is approximately the length of the contact region with the corresponding machining tool, such as the thickness h of the grinding wheel, as Figure 6 shown. In fact, during machining, the mechanical force is not applied along a single line segment L of length h, but is applied over a very narrow region having the same h. This narrow region can be regarded as being formed by a series of parallel line segments. The conditions for reducing cleavage along the line segment implemented according to the principles of the present invention (to be explained below) can be applied to each of these individual lines.

[0067] To evaluate the influence of the radial mechanical force applied inwardly to the cleavage plane in the contact region, the contact region and the actual length of the (one or more) line segments L where the mechanical force is actually applied are considered. The length of the line segment L and / or the length h of the narrow region is mainly determined by the thickness h of the machining tool.

[0068] During the machining of a SiC semi-finished product having an off-axis orientation of 4° with the standard shown in Figure 4A - Figure 4B or an on-axis orientation as shown in Figure 2 , for example, the radial force is applied laterally along the outer periphery of the crystal cylindrical surface at multiple positions by a grinding wheel. The influence of the applied force on the development or non-development of cracks on the crystal highly depends on the position / region where the force is applied along the cylinder periphery. The following extreme cases can be distinguished regarding the orientation of different cleavage planes relative to the application region of the radial force, as Figure 7 and Figure 8 shown.

[0069] Figure 7 shows when from the direction Another schematic side view of a 4H-SiC semi-finished product 400 with an off-axis orientation of 4° standard when observed (i.e., observed from the main plane OF), and which represents the cleavage plane intersects the force line segment L along which a mechanical force is applied (where h represents the thickness of the grinding wheel). As Figure 7 shown, the inventors have recognized that because the cleavage plane is oriented off-axis at a standard 4° and is not parallel to the cylinder axis C and thus not transverse to the front face 420a of the 4H-SiC semi-finished product 400, so in a first approximation, for example, the radial force applied by the grinding wheel in the direction along the line segment L is applied not only on one plane but also simultaneously on a plurality of parallel cleavage planes that intersect the side surface of the 4H-SiC semi-finished product 400 at the force line segment L of length h Based on the atomic distances in the 4H-SiC crystal structure, it is estimated that the radial force actuated along the line segment L is distributed over a plurality of equivalent, parallel type cleavage planes, for example, up to 2.6×10 5 planes per millimeter in the case of the off-axis orientation of 4° shown This means that the force applied to each individual cleavage plane is greatly reduced, and thus the risk of cracks propagating within the individual parallel cleavage planes can be significantly reduced.

[0070] Figure 8 is Figure 7 Another schematic side view of the 4H-SiC semi-finished product 400 shown now observed from the side opposite to the direction, and shows another extreme case that occurs when the radial force is applied along the line segment L parallel to the C axis and towards direction. As Figure 8 shown, the inventors have recognized that the cleavage plane is oriented at a right angle relative to the front face 420a of the 4H-SiC semi-finished product 400 and along a line parallel to the central axis C, intersecting the cylinder side surface 430 from the bottom front face 420b up to the upper front face 420a. In this case, in a first approximation, the radial force is applied by the grinding wheel along the line segment L in the direction but this radial force can only be distributed over a single or very few parallel cleavage planes Therefore, since in this case, contrary to the case of the cleavage plane Figure 7 shown in the applied force is not distributed over a large number of cleavage planes so the maximum force applied during machining is actually applied to a single or reduced number of cleavage planes This results in a very high probability of cracking and easily causes the single-crystal SiC semi-finished product 400 to break during machining.

[0071] Because the basal plane (0001) is inclined by 4° in the direction and all other remaining cleavage planes of the type and type are not parallel to the C-axis, and exhibit a behavior in terms of the robustness to cleavage that lies between the two extreme cases described above for the cleavage planes and .

[0072] As can be seen from the above, so far, the cleavage plane remains the most sensitive cleavage plane to cracks and fissures during machining, so the possibility of cracks appearing along these cleavage planes is very high. Therefore, the inventors have realized that the standard 4° off-axis orientation of 4H-SiC semi-finished products for different purposes of improving the epitaxial quality of materials to be grown on 4H-SiC substrates in the prior art may bring beneficial and surprising effects in reducing cleavage along certain crystal orientations, but this positive effect is not achieved at every position around the periphery of the cylindrical surface of the 4H-SiC semi-finished product or 4H-SiC semi-substrate, especially at the position where the cleavage plane intersects the outer cylindrical surface.

[0073] The present invention provides a method, a single-crystal 4H-SiC substrate, and a semi-finished product, which solve the problems related to cracks / fissures formed along crystal cleavage planes, i.e., cleavage planes in the case of 4H-SiC substrates and semi-finished products with an off-axis orientation (such as the above-mentioned 4° off-axis orientation).

[0074] Hereinafter, for simplicity, the principle of the present invention will be described for the case of a 4H-SiC semi-finished product with a 4° off-axis orientation in the direction. However, the present invention can be applied to variants of single-crystal SiC semi-finished products (or substrates) other than 4H-SiC, and / or other single-crystal semiconductor materials with other off-axis orientations and having preferred cleavage planes that are transverse to the front orientation of the bulk crystal and / or substrate.

[0075] The basic principle of the present invention is that by setting a specific crystal orientation of the 4H-SiC crystal structure on the 4H-SiC semi-finished product (or 4H-SiC substrate), the sensitivity of the 4H-SiC crystal structure to cracking along the preferred cleavage plane (such as the plane ) can be reduced or even prevented, while maintaining the benefits brought by the off-axis orientation of the

[0001] direction to the epitaxial quality of the corresponding 4H-SiC substrate.

[0076] ​​​​In order to reduce or avoid the formation of cracks on a 4H-SiC semi-finished product having an off-axis orientation of 4° (4° ± 0.5°), the present invention sets a specific orientation of the crystal structure on the 4H-SiC semi-finished product (or 4H-SiC substrate) relative to the corresponding (one or more) outer surfaces (such as the side surface and / or one or two front surfaces of the 4H-SiC semi-finished product). For cleavage planes meeting the conditions, the occurrence of cracks can be reduced or even avoided, and the conditions are that the orientation is such that the radial force applied during machining is distributed on at least a predetermined minimum number of parallel cleavage planes per unit length of the force line segment L and independently of the position around the outer circumference of the 4H-SiC semi-finished product.

[0077] The minimum number of cleavage planes on the force line segment L per unit length can be estimated based on the atomic distances in the 4H-SiC lattice. The inventors have found that the occurrence of cracks / cracks can be reduced by a minimum number of 1000 equivalent parallel cleavage planes per millimeter of the force line segment L. The preferred number of intersecting planes corresponds to 1500 equivalent parallel cleavage planes per millimeter of the force line segment length. Further estimation shows that for any number of intersecting cleavage planes up to a maximum number of 10000 equivalent parallel cleavage planes per millimeter of the force line segment, the required increase in anti-cleavage robustness can be achieved without affecting the epitaxial characteristics of the SiC semi-finished product or substrate deviated from 4°.

[0078] The distribution of the applied mechanical force on a large number of parallel cleavage planes per unit length of the force line segment allows reducing the probability of cracking. However, since the number of cleavage planes intersecting the force line segment L is closely related to their inclination relative to the front surface of the cylinder, it is desirable to keep the inclination of the cleavage planes as low as possible so as not to have a negative impact on the quality of epitaxial growth on the final substrate and thus not to have a negative impact on the number of planes intersecting the force line segment, while still achieving the expected effect of improving the anti-cleavage robustness of the 4H-SiC semi-finished product and the substrate made therefrom.

[0079] Figure 9A - Figure 9B and Figure 10A - Figure 10B show exemplary embodiments of a 4H-SiC semi-finished product having a predetermined orientation of a basic 4H-SiC crystal structure with improved mechanical robustness according to the present invention, and more specifically, the cleavage planes . Figure 9A - Figure 9B and Figure 10A - Figure 10B The relative dimensions and angles used are only for facilitating understanding and are not drawn to scale. These exemplary predetermined orientations are also applicable to 4H-SiC substrates.

[0080] Figure 9A - Figure 9B Schematically shows a 4H-SiC semi-finished product 500 according to an exemplary embodiment, wherein the spatial orientation of the 4H-SiC crystal structure relative to the longitudinal axis C of the 4H-SiC semi-finished product 500 (or relative to one or both of its front surfaces 520a, 520b and / or side surfaces 530), except that the basal plane (0001) faces the direction with a first tilt angle δ1 (e.g., δ1 = 4° ± 0.5°, as Figure 9A shown), an off-axis orientation, further includes an inclination of the basal plane (0001) towards the direction with a non-zero second tilt angle δ2, as Figure 9B shown. Thus, not only is the cleavage plane tilted by the tilt angle δ1 with respect to the central axis C of the 4H-SiC semi-finished product 500 (as Figure 9A shown), but also the cleavage plane is tilted by the tilt angle δ2 with respect to the central axis C (as Figure 9B shown). Therefore, assuming that a radial force is applied by a machining tool along a line segment L of length h on the curved side surface 530 (the line segment L is defined as a line segment on a plane tangent to the side surface 530 in the contact area), regardless of the position of the line segment L along the outer circumference of the 4H-SiC semi-finished product 500 (i.e., the area where the radial force is applied), there are always multiple types of parallel cleavage planes intersecting the force line segment L per unit length.

[0081] Therefore, the situation where the radial force applied during the grinding process is applied to a single or only a few cleavage planes as described above (e.g., the above reference Figure 4B described) does not occur in the 4H-SiC semi-finished product 500 with the above-mentioned predetermined orientation.

[0082] In addition, by estimating the value of the second tilt angle δ2, cracks can be significantly reduced or even avoided in a controlled manner during the machining of the 4H-SiC semi-finished product 500 or a 4H-SiC substrate having the same predetermined orientation, wherein the second tilt angle δ2 generates at least a predetermined minimum number of types of intersecting parallel cleavage planes per unit length of the line segment, and the radial force applied per unit plane at the second tilt angle δ2 becomes lower than the given cleavage property threshold of a specific cleavage plane.

[0083] Figure 10A - Figure 10BSchematically shown is a 4H-SiC semi-finished product 600 having another predetermined orientation for improving mechanical robustness according to another exemplary embodiment. In this configuration, the 4H-SiC crystal structure has a predetermined spatial orientation with respect to the longitudinal axis C (or with respect to one or both of the front faces 620a, 620b of the 4H-SiC semi-finished product 600 and / or the side surfaces 630), such that in addition to the off-axis orientation of the

[0001] direction and the corresponding basal plane (0001) towards the direction at a first tilt angle δ1 (e.g., δ1 = 4° ± 0.5°, as Figure 10A shown), it also includes an inclination of the basal plane (0001) towards the direction at a non-zero second tilt angle δ2, as Figure 10B shown. In this spatial orientation, the cleavage plane is then inclined at an angle δ2 with respect to the central axis C of the 4H-SiC semi-finished product 600. Thus, similar to the Figure 9A - Figure 9B embodiment, any force segment L parallel to the central axis C on the side surface 630 will intersect at least a predetermined minimum number of type of parallel cleavage planes per unit length of the force segment L, regardless of the position on the side surface 630 that defines the segment L, and thus, regardless of the position where the radial force is applied during the grinding process. Also in this case, the value of the second tilt angle δ2 can be estimated in order to achieve at least a predetermined minimum number of type of intersecting parallel cleavage planes per unit length of the segment, at which the radial force of each cleavage plane becomes lower than a given cleavage threshold.

[0084] The second tilt angle δ2 can be estimated based on the known distance between two equivalent parallel cleavage planes of the type (e.g., the plane), and / or by considering parameters of the mechanical process (e.g., the height h of the grinding tool in the contact area, the force and grinding speed usually applied, etc.), and / or the known cleavage threshold of a specific type of cleavage plane. Alternatively, the second tilt angle δ2 can be determined and adjusted experimentally.

[0085] Two exemplary embodiments share the following principle of the present invention: distributing the external mechanical force over a plurality of equivalent parallel cleavage planes per unit length of the force segment L to reduce or even eliminate the occurrence of cracks, regardless of the position around the entire periphery of the SiC semi-finished product to which such external mechanical force is to be applied.

[0086] In 4H-SiC substrates or wafers having the same spatial orientation of the 4H-SiC crystal structure as described with reference to Figure 9A - Figure 9B and Figure 10A - Figure 10B above, a similar improvement in cleavage-resistant mechanical robustness is also achieved.

[0087] A predetermined orientation of the 4H-SiC crystal structure can be set on a 4H-SiC semi-finished product by the following method.

[0088] In the original 4H-SiC crystal obtained after crystal growth and / or the first rough machining (pre-machined 4H-SiC crystal), the crystal plane and the reference surface (e.g., one of the machined front faces or the cylindrical surface) are not yet aligned with the exact orientation required between each other, just as in the final 4H-SiC semi-finished product.

[0089] For this reason, at the start of machining, the original 4H-SiC crystal (or pre-machined 4H-SiC crystal) is mounted on a goniometer and / or a holder with one of its front faces (Si side (0001) or C side ) and glued or bonded thereto in order to accurately set the crystal orientation for machining. For such an orientation, a commercial X-ray device can be used, and with this device, the orientation of the crystal plane can be accurately determined and aligned. Thus, in order to set an off-axis orientation of 4°, in the first step, the original crystal orientation is adjusted with a goniometer in the X-ray device such that the basal plane (0001) (or plane) is accurately oriented in a direction orthogonal to the future cylindrical surface (i.e., the

[0001] axis is aligned with the C axis), and the future cylindrical surface will be defined in the subsequent machining (e.g., by a grinding process).

[0090] In a subsequent step, the thus-oriented original SiC crystal (or pre-machined SiC single crystal) is tilted by 4° (+ / -0.5°) in the direction using a goniometer in order to provide the required 4° off-axis orientation of the basal plane as required for high-quality epitaxy of the future SiC substrate. After this positioning, the crystal plane is oriented as shown in and Figure 4A and Figure 4B . In this case, the angle between the

[0001] axis of the basal plane and the future cylinder axis C is 4° (+ / -0.5°).

[0091] Thereafter, the outer diameter of the cylinder is set to the diameter of the future substrate, for example, by a grinding process. As described above, the diameter setting process is one of the most critical steps regarding crack occurrence. During this setting process, it can be ensured that the previously goniometer-adjusted orientation of the crystal plane relative to the cylindrical surface is accurately transferred. In addition, the main plane or secondary plane of the orientation and / or the notch can be ground during this process step. Subsequently, before any further machining, the required orientation of the crystal plane relative to the cylindrical surface is checked / controlled using an X-ray device.

[0092] After treatment of the outer diameter and / or the orientation plane and control of the desired orientation of the crystal plane relative to the cylindrical surface, a process for defining the front face of the SiC single crystal is carried out, resulting in a final SiC semi-finished product whose external shape resembles Figure 1 the shape shown in

[0093] To set the crystal plane with a predetermined spatial orientation for enhanced mechanical robustness (e.g., Figure 9A - Figure 9B or Figure 10A - Figure 10B the predetermined orientation shown), the raw SiC crystal (or pre-processed SiC crystal) is subjected to a process for setting the desired predetermined orientation, which process includes spatially orienting the raw (or pre-processed) SiC crystal, for example, by using any one of the following sequences of orientation processes. Preferably, each step of the orientation process sequence is carried out using a goniometer and commercial X-ray equipment to ensure precise orientation in each step of the process sequence.

[0094] As Figure 9A - Figure 9B shown, according to a first orientation process sequence for setting the predetermined orientation of the SiC crystal structure in the 4H-SiC semi-finished product 500, the raw or pre-processed 4H-SiC crystal is spatially oriented such that the basal plane is first aligned with the initial orientation, in which the basal plane is substantially perpendicular to the direction of the alignment central axis C (corresponding to the future cylindrical side surface direction of the final 4H-SiC semi-finished product 500). In a subsequent step, by tilting the 4H-SiC crystal by the same amount δ1 in the direction, the basal plane is tilted from the initial orientation by a first tilt angle δ1 in the direction and becomes the first orientation. Then the thus-oriented SiC crystal is tilted by a second tilt angle δ2 in the direction, which causes the basal plane (0001) to be tilted from the first orientation to the second orientation by the second tilt angle δ2 by tilting in the direction.

[0095] As Figure 10A - Figure 10B shown, according to an alternative second orientation process sequence for setting the predetermined orientation of the SiC crystal structure in the 4H-SiC semi-finished product 600, the basal plane is also first oriented to an initial orientation perpendicular to the direction of the central axis C (which corresponds to the direction of the future cylindrical side surface 630). Then the basal plane is tilted from the initial orientation by a first tilt angle δ1 in the direction and becomes the first orientation. Then the thus-oriented raw or pre-processed SiC crystal is tilted by a second tilt angle δ2 in the direction such that the basal plane (0001) is tilted from the first orientation to the second orientation by an additional tilt angle δ2 by tilting in the direction.

[0096] In the above first orientation process sequence and second orientation process sequence, the value of the first tilt angle is preferably 4° ± 0.5°, where the error of ±0.5° is associated with the acceptable tolerance of the value of the first tilt angle that still allows the desired improvement in the epitaxial characteristics of each semiconductor substrate to be obtained. The value of the second tilt angle δ2 is preferably 0.023°. However, any value within the range [0.015°; 0.153°] can be used for the second tilt angle δ2, at which the desired orientation effect on mechanical robustness can be achieved. In particular, the value of the second tilt angle δ2 to be used can be estimated based on the distance between the equivalent parallel cleavage planes of the 4H-SiC lattice and with reference to at least a predetermined minimum number of intersecting cleavage planes on the force line segment per unit length as described above, and the cleavage effect of these cleavage planes is intended to be minimized.

[0097] According to a third orientation process sequence for setting another predetermined orientation for improving mechanical robustness, the basal plane is first aligned to an initial orientation that is perpendicular to the direction of the central axis C, i.e., the direction of the future cylindrical side surface. Then the basal plane is rotated by a predetermined rotation angle in the clockwise direction about this initial orientation. The predetermined rotation angle is 0.33° or a value within the range [0.22°; 2.19°]. In a subsequent step, the basal plane is further tilted by a third tilt angle δ3 in the direction of the 4H-SiC crystal structure. The third tilt angle is preferably 4°, with a tolerance of ±0.5°.

[0098] Alternatively, a fourth orientation process sequence can be used, in which the basal plane is also first aligned to an initial orientation that is perpendicular to the direction of the central axis C, i.e., the direction of the future cylindrical side surface. Then the basal plane is rotated by a predetermined rotation angle in the counterclockwise direction about this initial orientation. The predetermined rotation angle is preferably 0.33°, but can also be any value within the range [0.22°; 2.19°] to obtain the desired orientation effect on mechanical robustness. In a subsequent step, the basal plane is further tilted by the third tilt angle δ3 in the direction of the 4H-SiC crystal structure, preferably tilted by 4° ± 0.5°. In the direction, preferably tilted by 4° ± 0.5°.

[0099] After the crystal orientation of the original SiC crystal (or pre-processed SiC crystal) has been aligned by any of the above orientation process sequences, one or more external reference surfaces of the final 4H-SiC semi-finished product can be machined with reference to the alignment axis C. For example, at least a partially curved side surface can be machined on the oriented original or pre-processed SiC crystal in a direction parallel to the alignment axis C. Additionally or alternatively, one or two front surfaces of the final 4H-SiC semi-finished product can be machined in a direction orthogonal to the C axis.

[0100] Thus, the predetermined orientation of the basal plane (0001) and other crystal planes of the 4H-SiC structure can be accurately set relative to at least one reference surface of the 4H-SiC semi-finished product, namely the curved side surface and / or one or both of its front surfaces.

[0101] The diameter of the curved side surface can be set to substantially correspond to the expected diameter of the substrate wafer to be sliced from the 4H-SiC semi-finished product. In particular, the techniques of the present invention can be applied to improve the mechanical robustness of 4H-SiC semi-finished products with an outer diameter of 150.0 mm ± 0.5 mm, 200.0 mm ± 0.5 mm, or 250.0 mm ± 0.5 mm and 4H-SiC substrates obtained therefrom. The error of ±0.5 mm in the outer diameter corresponds to the tolerance associated with the standard grinding process. However, the diameter tolerance can be higher or lower than 0.5 mm, depending specifically on the techniques used to set the side surface of the 4H-SiC semi-finished product and / or adjust its outer diameter.

[0102] Furthermore, the techniques of the present invention can be applied to improve the mechanical robustness of 4H-SiC semi-finished products with a height greater than 20 mm, or preferably greater than 15 mm, in the direction of the longitudinal axis C. However, the present invention is also applicable to 4H-SiC semi-finished products or raw 4H-SiC crystals with a preselected height to produce a desired number of 4H-SiC substrate slices.

[0103] Subsequently, the SiC semi-finished product provided with the predetermined orientation of the 4H-SiC lattice for improving mechanical robustness can be divided into substrate wafers using well-known wafer separation processes (such as multi-wire sawing using diamond-based slurries, wire-based spark erosion, or other alternative separation processes). This predetermined orientation of the 4H-SiC lattice can be transferred to the substrate wafers by referring to any reference surface of the SiC semi-finished product during the separation process.

[0104] Alternative exemplary embodiments for supporting the SiC semi-finished product during the wafer separation process and transferring the predetermined orientation of the underlying 4H-SiC lattice to the SiC substrate are described in Figure 11 and Figure 12 shown.

[0105] Figure 11 A configuration is shown in which the transfer of the crystal orientation of the single-crystal SiC semi-finished product 700 (such as any one of the single-crystal SiC semi-finished products 500 and 600 described above) to the SiC substrate 740 is performed through the cylindrical side surface 730. In the case of a separation process in which the support of the single-crystal SiC semi-finished product 700 to be processed is achieved by the support of the cylindrical side surface 730, the cylindrical side surface 730 needs to be accurately aligned with respect to the orientation of the SiC crystal plane. Therefore, in this separation method, the orientation of the crystal plane is transferred by their respective alignment with respect to the cylindrical side surface 730.

[0106] Figure 12 shows a configuration in which a single-crystalline SiC semi-finished product 700 is supported on one of the front sides 720b. In the case of a separation process in which the support of the single-crystalline SiC semi-finished product to be processed is achieved by the support of the front side, the front side needs to be accurately aligned with respect to the orientation of the crystal plane. In these separation methods, the orientation of the SiC crystal plane is transferred by the alignment of one of the cylindrical front sides 720b with respect to the crystal plane. In this case, the orientation of the crystal plane with respect to the front side 720b used for support is preferably measured using a radiographic method, set using a goniometer, and accurately transferred during machining, for example, using a grinding process. In order to accurately transfer the predetermined orientation of the 4H-SiC crystal plane into the substrate wafer 740, the single-crystalline SiC semi-finished product 700 should satisfy one of the following basic conditions:

[0107] · At least one of the two front sides 720a and / or 720b (reference surfaces) is oriented at a right angle with respect to the cylindrical side surface 730, that is, the lattice orientation is accurately transferred through one of the reference surfaces;

[0108] · Both of the two front sides 720a and 720b (reference surfaces) are oriented at a right angle with respect to the cylindrical side surface 730, that is, the lattice orientation can be accurately transferred through the two reference surfaces;

[0109] · One of the front sides 720a or 720b (reference surface) is accurately oriented at a right angle with respect to the cylindrical side surface 730, while the second front side 720b or 720a is oriented such that the measurement in the direction shows that the total thickness variation (TTV) of the second front side with respect to the first front side is between 40 μm and 340 μm, that is, the lattice orientation can be accurately transferred through the two reference surfaces, where one front side is accurately oriented and the other front side is within the expected orientation.

[0110] However, even when producing individual 4H-SiC substrates or wafers 740 from the 4H-SiC semi-finished product 700 that satisfies any of the above ideal transfer conditions, the 4H-SiC substrate or wafer 740 may not be accurately cut parallel to one or both of the end faces 720a and 720b of the 4H-SiC semi-finished product 700 and / or perpendicular to the curved side surface 730. For example, when using a diamond-based wire saw, the saw wire may deviate during the cutting process, resulting in the individual substrates 740 possibly obtaining a wedge shape and / or possibly exhibiting significant thickness irregularities. Similar geometric deformations can also be observed on substrates obtained using other conventional separation processes.

[0111] Since the top and bottom surfaces of the original substrate 740 obtained from the SiC semi-finished product 700 using conventional separation methods are not entirely planar and / or parallel to each other, the orientation of the 4H-SiC lattice with respect to one or both front sides of the original 4H-SiC substrate 740 is not accurately transferred from the 4H-SiC semi-finished product 700 during the slicing process.

[0112] This geometric deformation of the sliced 4H-SiC substrate 740 is typically corrected by flattening the top and bottom surfaces using polishing and / or grinding processes. However, even in this case, the orientation of the 4H-SiC lattice with respect to the substrate reference surfaces (i.e., the side surfaces, top surface, and / or bottom surface) will no longer correspond to the predetermined orientation of the 4H-SiC crystal structure preset in the 4H-SiC semi-finished product 700.

[0113] For example, in a conventional process for grinding the front side of a SiC substrate, the original substrate 740 obtained after slicing is mounted on the mounting surface of a holder (e.g., a chuck) with one of its front sides, and the opposite top surface is ground without any further substrate alignment. Thus, the ground top front side of the 4H-SiC substrate 740 becomes a plane parallel to the support surface, and thus the orientation of the 4H-SiC lattice with respect to the bottom surface of the substrate mounted on the chuck is reproduced on the ground top surface of the substrate. Therefore, depending on the degree of deviation of the front side mounted on the chuck from the plane orthogonal to the symmetry axis C of the 4H-SiC semi-finished product 700, the orientation of the 4H-SiC crystal structure in the 4H-SiC substrate with respect to the ground top surface, and thus the orientation of the 4H-SiC cleavage plane with respect to the ground top surface, may exhibit a significant deviation from the predetermined orientation set in the 4H-SiC semi-finished product 700. In the case where the 4H-SiC substrate 740 is then turned to grind the previously mounted face on the chuck, the second front side will now be set parallel to the first ground face now mounted on the chuck, and the orientation of the basal plane and the 4H-SiC cleavage plane with respect to the second front side will also not match the predetermined orientation set in the 4H-SiC semi-finished product 700. Since the predetermined orientation of the SiC crystal structure for increasing mechanical robustness according to the present invention with respect to one or both front sides of the 4H-SiC substrate 740 may no longer exist after grinding, cracks and / or fissures may further occur during the final machining (e.g., grinding with a cup wheel) of the 4H-SiC substrate edge.

[0114] Similar problems can occur during the polishing of a 4H-SiC substrate 740 by a conventional polishing process, in which the substrate is machined with a rotor disk that applies a radial force to the substrate to remove material from both sides of the substrate. Cracks / fractures on the 4H-SiC substrate 740 may also occur during the polishing of the substrate if the 4H-SiC substrate 740 does not have a front side parallel to the plane and / or if the orientation of the lattice cleavage plane relative thereto does not correspond to a predetermined orientation for improving mechanical robustness.

[0115] Therefore, due to the deviation of the front side of the substrate from the ideal plane-parallel orientation after the slicing process, cracks or fractures may occur during the machining of the 4H-SiC substrate 740, even if these 4H-SiC substrates 740 are obtained from 4H-SiC semi-finished products 700 having a predetermined cleavage plane orientation for improving the anti-cleavage mechanical robustness according to the present invention.

[0116] To compensate for this manufacturing-related deviation of the SiC lattice orientation in the SiC substrate 740 from the predetermined lattice orientation of the present invention, a predetermined orientation of the 4H-SiC crystal structure relative to an axis substantially orthogonal to one or both front sides of the final 4H-SiC substrate 800 can be set (or realigned) in the original 4H-SiC substrate 740 sliced from the 4H-SiC semi-finished product 700 by applying a pre-aligned planarization process, as will be described below.

[0117] Figure 13A and Figure 13B A finished 4H-SiC substrate 800 is depicted, which has a predetermined SiC crystal orientation set for improving the anti-cleavage mechanical robustness of the substrate, which substantially corresponds to the predetermined orientation described above with reference to Figure 9A - Figure 9B the 4H-SiC semi-finished product 500.

[0118] An accurate orientation of the 4H-SiC lattice in the 4H-SiC substrate 800 can be achieved using a process for setting the predetermined orientation such that at each position on the side surface of the final 4H-SiC substrate 800, there is a line segment (not shown) intersecting with at least a predetermined minimum number of type of parallel cleavage planes per unit length.

[0119] In the case where the original substrate 4H-SiC 740 is a single-crystal 4H-SiC semi-finished product 700 that has already been set with the required predetermined orientation (e.g., as described above with reference to Figure 9A - Figure 9B and Figure 10A - Figure 10BWhen the described 4H-SiC crystal semi-finished products 500 and 600 are fabricated, a predetermined orientation of the SiC lattice has been set relative to at least one reference surface of the 4H-SiC semi-finished product 700 (such as one or both of the cylindrical side surface 730 and / or the front surfaces 720a and 720b). Then, as Figure 11 and Figure 12 shown, during the slicing of the 4H-SiC semi-finished product 700, this relative orientation of the SiC lattice is transferred to the original 4H-SiC substrate 740 by using one of these reference surfaces. For example, in the configuration shown in Figure 11 , the reference surface for transferring the crystal orientation is the side surface 730 of the 4H-SiC semi-finished product 700. In the configuration shown in Figure 12 , one of the front surfaces 720a and 720b of the 4H-SiC semi-finished product 700 is used as the reference surface.

[0120] After slicing, a goniometer and X-ray measurements can then be used to determine the crystal orientation in the original 4H-SiC substrate 740 to determine whether the desired orientation according to the principles of the present invention has been accurately transferred. In the case of identifying a deviation from the desired orientation, the process of setting the predetermined orientation of the SiC crystal structure in the 4H-SiC substrate 800 can then include applying a pre-aligned planarization process to the original 4H-SiC substrate 740 to correct the orientation of the SiC lattice relative to the (one or more) front and / or side surfaces of the 4H-SiC substrate.

[0121] During the pre-aligned planarization process, the original 4H-SiC substrate 740 is spatially oriented relative to the planarization tool (or the reference alignment axis C) such that one or more crystal axes of the 4H-SiC lattice are aligned in a specific direction before planarization. Then, the front surface of the 4H-SiC substrate 740 can be planarized, for example, by grinding as described above, while maintaining the spatial orientation of the substrate 740 during the planarization step. As an addition or alternative to the (one or more) front surfaces, the side surface of the 4H-SiC substrate 740 can be shaped parallel to the reference alignment axis C and / or set to the desired substrate diameter in the spatially oriented 4H-SiC substrate 740.

[0122] The planarization process with pre-alignment is preferably carried out by mounting the 4H-SiC substrate 740 on a goniometer and measuring the crystal orientation of the corresponding 4H-SiC lattice, for example, by using X-ray radiation. Then, the original 4H-SiC substrate 740 is spatially oriented in a three-dimensional space to align the crystal axes and / or crystal planes of the SiC crystal with respect to the reference alignment direction C, such as the crystal axis

[0001] and / or the corresponding basal plane (0001). The reference alignment direction is preferably selected to be coincident or parallel with the axis C of the final 4H-SiC substrate 800, where the axis C is the symmetry axis of the cylindrical surface that includes at least a partially curved side surface 830 of the 4H-SiC substrate 800 after grinding, polishing, and / or other finishing processes for preparing the substrate 800 for layer deposition and manufacturing other electronic components.

[0123] The planarization process with pre-alignment of the original 4H-SiC substrate 740 can use any one of the first to fourth orientation process sequences for setting a predetermined orientation of the SiC lattice on the above-mentioned original (or pre-processed) 4H-SiC crystal semi-finished product. For example, when using the above-mentioned first orientation process sequence, the original 4H-SiC substrate 740 is spatially oriented such that the basal plane (0001) is first aligned with the initial orientation, in which the basal plane is substantially at a right angle to the reference alignment direction (i.e., the

[0001] axis substantially parallel to the reference alignment direction). Then, the 4H-SiC substrate 740 is tilted to make the basal plane tilt from the initial orientation by a first tilt angle δ1 in the direction to become the first orientation, thereby changing the orientation of all cleavage planes except the cleavage plane Then, the 4H-SiC substrate 740 is tilted to tilt the basal plane (0001) in the direction by a second tilt angle δ2 to become the second orientation, thereby changing the orientation of the cleavage plane This results in the 4H-SiC basal plane (0001) being located in a plane in the second orientation, which is tilted by the tilt angle δ1 with respect to the plane orthogonal to the reference alignment axis (e.g., with respect to the horizontal plane in the case of the vertical central axis C) in the direction of the axis from the initial orientation towards and tilted by the tilt angle δ2 in the direction of the axis from the same initial orientation towards Each step of the orientation process sequence is preferably accompanied by using a goniometer and X-ray radiation measurement to determine the crystal axis orientation and performing orientation adjustment if necessary to ensure accurate alignment of the lattice.

[0124] Once the original 4H-SiC substrate 740 is spatially oriented and the SiC lattice is accurately aligned relative to a reference alignment axis, one or both of the front faces 820a and 820b of the substrate 800 are planarized, for example by grinding along a plane transverse to the reference alignment axis, while maintaining the 4H-SiC crystal in a second orientation. This results in the planar front face 820a and / or 820b being substantially orthogonal to the symmetry axis C and the 4H-SiC crystal orientation being accurately set to a desired predetermined orientation relative to this face. Additionally or alternatively, the shape and / or diameter of the side surface in the original 4H-SiC substrate 740 after spatial orientation can be ground parallel to the reference alignment axis, such that the curved side surface 830 of the final 4H-SiC substrate 800 extends parallel to the symmetry axis C, as Figure 13A - Figure 13B shown.

[0125] Thus, the 4H-SiC substrate 800 obtained after a pre-aligned planarization process exhibits an accurate orientation of the 4H-SiC lattice relative to the substrate side surface 830 and / or one or both of the front faces 820a, 820b, which corresponds to a predetermined orientation that improves the cleavage-resistant mechanical robustness.

[0126] In an alternative embodiment, the process of setting a predetermined crystal orientation that improves mechanical robustness in the 4H-SiC substrate 800 can start from a single-crystal 4H-SiC semi-finished product (e.g., a 4H-SiC semi-finished product 100 having an on-axis orientation as Figure 2 shown) with a standard crystal orientation different from the predetermined orientation of the present invention. In this case, the process of setting a predetermined crystal orientation in the 4H-SiC substrate 800 includes: spatially orienting the 4H-SiC semi-finished product 100 relative to the reference alignment axis, for example using a goniometer and X-ray radiation measurement, such that the 4H-SiC lattice is oriented in a desired predetermined orientation with a

[0001] axis of the basal plane being predeterminedly tilted in a direction and amount relative to the reference alignment axis. This spatial orientation of the 4H-SiC semi-finished product 100 can be performed using any one of the first to fourth orientation process sequences described above for setting a predetermined orientation of the SiC lattice on the above-mentioned 4H-SiC crystal semi-finished products 500 or 600. However, in this embodiment, the original 4H-SiC substrate is obtained by directly cutting wafers from the spatially oriented 4H-SiC semi-finished product 100. In the case of starting from a conventional 4H-SiC semi-finished product 400 with a 4° off-axis orientation described above, the step of tilting the 4H-SiC semi-finished product by a first tilt angle of 4° in the Figure 4A - Figure 4B direction described in the above first and second orientation sequences can be omitted. direction described in the above first and second orientation sequences can be omitted.

[0127] Then, after spatially orienting the 4H-SiC crystal semi-finished product 100 or 400 in a direction substantially transverse to the reference alignment axis, which is selected to substantially correspond to or be parallel to the central axis C of the final 4H-SiC substrate 800, the 4H-SiC wafer is cut. Similar to the previous embodiments, a goniometer and X-ray measurements can also be used to determine the crystal orientation in the original 4H-SiC substrate obtained after slicing, to determine whether the desired orientation of the SiC lattice according to the principles of the present invention has been accurately transferred.

[0128] In the case where a deviation from the desired orientation is identified, the process of setting a predetermined orientation of the SiC crystal structure in the 4H-SiC substrate 800 may then include: applying a planarization process with the above-mentioned pre-alignment to correct the orientation of the SiC lattice relative to the (one or more) front and / or side surfaces of the 4H-SiC substrate. If no deviation from the desired orientation is detected and / or the deviation lies within a predetermined tolerance that is not expected to have a significant impact on the cleavage resistance robustness of the 4H-SiC substrate 800, the planarization process with pre-alignment is omitted.

[0129] In summary, by setting the optimal orientation of the preferred cleavage plane relative to the side surface and / or one or both front surfaces of the SiC semi-finished product or 4H-SiC substrate, the present invention allows for a reduction in the occurrence of cracks during the machining of the 4H-SiC single crystal and / or 4H-SiC substrate, such that the radial mechanical force applied during machining in a given area is always distributed over at least a predetermined minimum number of preferred cleavage planes, regardless of the position of the applied mechanical force on the periphery of the 4H-SiC semi-finished product or 4H-SiC substrate.

[0130] Thus, through this optimal orientation of the 4H-SiC crystal structure, higher mechanical robustness can be achieved during the machining of bulk SiC crystals and SiC substrates, and thus higher yields of single crystal semi-finished products and final products can be achieved, without reducing the epitaxial quality of future substrates and without significantly increasing the cost and / or time of the corresponding mechanical processes.

[0131] Although certain features of the above-described exemplary embodiments have been described using terms such as "downward", "top", "bottom", and "horizontal", these terms are used only for the convenience of describing the corresponding features and their relative orientations within the 4H-SiC single crystal and / or 4H-SiC substrate, and should not be construed as limiting the claimed invention or any of its components to a particular spatial orientation. Additionally, although the present invention has been described above with reference to 4H-SiC crystals, the principles of the present invention can also be advantageously applied to other variant SiC single crystals and / or other semiconductor single crystals, such as AlN and GaN.

[0132] Reference numerals

[0133] C Geometric longitudinal axis

[0134] L Line segment

[0135] h Grinding wheel height, length of line segment L

[0136] 100 SiC semi-finished product

[0137] 110 Orientation plane (OF)

[0138] 120a, 120b Upper and lower fronts of the cylinder

[0139] 130 Cylinder side surface

[0140] 200 SiC semi-finished product with on-axis orientation (prior art)

[0141] 220 Front face

[0142] 230 Cylinder side surface

[0143] 240 Grinding wheel

[0144] 300 SiC substrate with an orientation deviated by 4° (prior art)

[0145] 320a, 320b Upper and lower fronts of the cylinder

[0146] 330 Cylinder side surface

[0147] 400 SiC semi-finished product with an orientation deviated by 4° (prior art)

[0148] 420a, 420b Upper and lower fronts of the cylinder

[0149] 430 Cylinder side surface

[0150] 500 SiC semi-finished product

[0151] 520a, 520b Upper and lower fronts of the cylinder

[0152] 530 Cylinder side surface

[0153] 600 SiC semi-finished product

[0154] 620a, 620b Upper and lower fronts of the cylinder

[0155] 630 Cylinder side surface

[0156] 700 Single crystal SiC semi-finished product

[0157] 710 Bracket

[0158] The front and side surfaces of 720a, 720b and 730

[0159] 740 Substrate wafer

[0160] 800 Final 4H-SiC substrate

[0161] The upper front and lower front of the substrate of 820a, 820b

[0162] 830 Cylindrical side surface of the substrate

Claims

1. A method for producing a single crystal 4H-SiC substrate having improved cleavage mechanical robustness, the single crystal 4H-SiC substrate having a substrate axis and at least partially curved side surfaces parallel to the substrate axis, the method comprising: Performing a process of setting a predetermined orientation of the 4H-SiC crystal structure on the 4H-SiC substrate relative to the substrate axis such that at each position on the side surface of the 4H-SiC substrate there is a line segment that intersects at least a predetermined minimum number of parallel cleavage planes of the {1010} type per millimeter of line segment length, wherein the line segment is parallel to the substrate axis, The major axis of the basal plane of the 4H-SiC crystal structure is inclined at a first inclination angle relative to the substrate axis towards the [1120] direction, The first inclination angle is 4°, with a tolerance of ±0.5°; and The major axis of the basal plane of the 4H-SiC crystal structure is inclined at a second inclination angle relative to the substrate axis towards the [1100] direction or the [1100] direction, and The second inclination angle is a value selected from the range [0.015°; 0.153°] such that The predetermined orientation of the 4H-SiC crystal structure results in at least 1000 planes of the {1010} type of parallel cleavage planes per millimeter of line segment length, The number of parallel cleavage planes (1100) intersecting the line segment is less than 10000 parallel cleavage planes per millimeter of line segment length, and The value of the second inclination angle is estimated based on the distance between the parallel cleavage planes of the lattice of the 4H-SiC substrate and with reference to at least a predetermined minimum number of parallel cleavage planes per millimeter of line segment length, and the cleavage effect of these cleavage planes is intended to be minimized, wherein the method further comprises: After cutting the single crystal 4H-SiC substrate from a 4H-SiC semi-finished product, determining the crystal orientation of the 4H-SiC crystal structure in the 4H-SiC substrate relative to the front surface of the 4H-SiC substrate by performing an angular measurement, the 4H-SiC semi-finished product being an oriented crystal cylinder and having a selected height to produce a desired number of single crystal 4H-SiC substrate slices; If the determined crystal orientation deviates from the predetermined orientation relative to the substrate axis of the 4H-SiC substrate, spatially orienting the 4H-SiC substrate such that the major axis of the basal plane of the 4H-SiC crystal structure is inclined at the first inclination angle relative to the substrate axis towards the [1120] direction, and the major axis of the basal plane of the 4H-SiC crystal structure is inclined at the second inclination angle relative to the substrate axis towards the [1100] direction or towards the [1100] direction; Machining the outer surface of the spatially oriented 4H-SiC substrate with reference to an alignment axis to form at least one of the following: The at least partially curved side surface substantially parallel to the alignment axis, and At least one front surface substantially orthogonal to the alignment axis; Wherein, the substrate axis of the processed 4H-SiC substrate substantially corresponds to or is parallel to the alignment axis for the spatial orientation of the 4H-SiC crystal structure.

2. The method according to claim 1, wherein The process of setting the predetermined orientation of the 4H-SiC crystal structure on the 4H-SiC substrate includes: Providing a single-crystal 4H-SiC semi-finished product for producing at least one original 4H-SiC substrate therefrom, Wherein, the 4H-SiC semi-finished product has been set with the predetermined orientation of the 4H-SiC crystal structure relative to the substrate axis of the 4H-SiC semi-finished product and the reference surface of the single-crystal 4H-SiC semi-finished product; Mounting the 4H-SiC semi-finished product having the reference surface onto a support surface; and Cutting the mounted 4H-SiC semi-finished product in a direction transverse to or parallel to the support surface to obtain the at least one original 4H-SiC substrate.

3. The method according to claim 1, wherein The process of setting the predetermined orientation of the 4H-SiC crystal structure on the 4H-SiC substrate includes: Providing a single-crystal 4H-SiC semi-finished product for producing at least one original 4H-SiC substrate therefrom; Spatially orienting the 4H-SiC crystal structure by predetermining an inclination of the [0001] axis of the basal plane relative to a predetermined alignment axis in a direction and by an amount; and After spatially orienting the 4H-SiC crystal structure, cutting the 4H-SiC semi-finished product in a direction substantially transverse to the predetermined alignment axis to obtain the at least one original 4H-SiC substrate.

4. The method according to any one of claims 1 to 3, wherein Spatially orienting the 4H-SiC crystal structure with the predetermined inclination includes: Orienting the basal plane of the 4H-SiC crystal structure in an initial orientation; Tilting the basal plane from the initial orientation to a first orientation at the first tilt angle in the direction of the [1120] direction of the 4H-SiC crystal structure; and Tilting the basal plane from the first orientation to a second orientation at the second tilt angle in the direction of the [1100] direction or the [1100] direction of the 4H-SiC crystal structure; Wherein, in the initial orientation, the basal plane is substantially perpendicular to the predetermined alignment axis.

5. The method according to claim 4, wherein, The orientation of the 4H-SiC crystal structure tilted at the first tilt angle and / or the second tilt angle is verified by angle measurement.

6. The method according to any one of claims 1 to 3, wherein The process of the spatial orientation includes: Orienting the basal plane of the 4H-SiC crystal structure in an initial orientation; Rotating the basal plane about the initial orientation in a clockwise direction by a predetermined rotation angle; Tilting the rotated basal plane at a third tilt angle in the direction of the [1120] direction of the 4H-SiC crystal structure; and Wherein, in the initial orientation, the basal plane is substantially perpendicular to the alignment axis.

7. The method according to any one of claims 1 to 3, wherein, The process of the spatial orientation includes: Orienting the basal plane of the 4H-SiC crystal structure in an initial orientation; Rotating the basal plane about the initial orientation in a counterclockwise direction by a predetermined rotation angle; Tilting the rotated base plane towards the [1120] direction of the 4H-SiC crystal structure by a third tilt angle; and wherein, in the initial orientation, the base plane is substantially perpendicular to the alignment axis.

8. The method according to claim 6, wherein, the predetermined rotation angle is a value within the range of [0.22°, 2.19°], and the third tilt angle is 4°, with a tolerance of ±0.5°; and the orientation of the 4H-SiC crystal structure after rotating the predetermined rotation angle and / or tilting the third tilt angle is verified by angle measurement.

9. The method according to claim 7, wherein, the predetermined rotation angle is a value within the range of [0.22°, 2.19°], and the third tilt angle is 4°, with a tolerance of ±0.5°; and the orientation of the 4H-SiC crystal structure after rotating the predetermined rotation angle and / or tilting the third tilt angle is verified by angle measurement.

10. The method according to claim 8, wherein, The predetermined rotation angle is 0.33°.

11. The method according to claim 9, wherein, The predetermined rotation angle is 0.33°.

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