SiC crystals with optimal lattice plane orientation for reducing cracks and their manufacturing method

Abstract

To provide a single crystal 4H-SiC semi-product having a specific orientation of a crystal structure that is set so as to reduce or eliminate the generation of a crack during a mechanical treatment, and a manufacturing method of the same.SOLUTION: A single crystal 4H-SiC semi-product has a longitudinal axis and a side face that is parallel to the longitudinal axis and at least partly curved. In the longitudinal axis of a crystal structure of the 4H-SiC semi-product, a line segment that has a form represented by a formula 1 and crosses at least a minimum predetermined number of a parallel cleavage plane per unit length is oriented at each position of the side face of the semi-product. This line segment is defined by a plane contacting the side face at one point of the position.SELECTED DRAWING: Figure 9B

Description

[Technical field]

[0001] The present invention relates to bulk SiC single crystals having a particular crystal structure orientation to reduce or eliminate the occurrence of cracks and fissures during machining, and methods for producing single crystal SiC semi-finished products having such orientation. [Background technology]

[0002] Silicon carbide (SiC) substrates are commonly used in the manufacture of electronic components for a wide range of applications, such as power electronics, radio frequency and optoelectronic applications. SiC substrates are generally produced from bulk SiC single crystals, which can be grown by standard methods such as physical vapor deposition (PVD) and suitable source materials. In this case, SiC substrates are produced from the grown crystal by cutting wafers with a wire saw and then polishing the wafer surface in multiple polishing steps. In a subsequent epitaxy process, thin single crystalline layers of semiconductor materials (e.g., SiC, GaN) are deposited on the SiC substrate. The properties of these epitaxial layers, and of the components made therefrom, depend crucially on the quality of the underlying SiC substrate.

[0003] A standard method for producing SiC crystals by physical vapor deposition is described in US Pat. No. 8,865,324. The bulk SiC crystal produced in this way is then oriented, for example by X-ray irradiation, so that the crystal structure has the necessary orientation for further mechanical processing. By way of example, the desired substrate diameter is then set in the monocrystalline SiC semi-finished product by various surface treatment steps of the bulk SiC crystal, for example by grinding, one or more orientation flats (OF) are ground on its lateral sides, and the front surface of the so-treated crystal cylinder is prepared for wafer division processing, for example by wire sawing. As shown in FIG. 1, the SiC semi-finished product 100 resulting from such mechanical processing of the bulk SiC crystal is an oriented cylinder with a diameter equal to the diameter of the future substrate wafer, with one or two orientation flats 110 (or notches) defined on the lateral cylindrical faces 130, and with parallel flat front surfaces 120a, 120b.

[0004] The SiC semi-finished product 100 is then divided into individual original single crystal SiC substrates, for example using a wire sawing process. After quality control, the single crystal SiC substrates are subjected to further mechanical processing. As an example, the following processing sequence can be used: After the edge mechanical processing, a single or multi-step grinding or polishing process is performed to remove the destruction layer generated during the substrate separation process and to gradually reduce the roughness of the substrate. Then, a chemical mechanical polishing process (CMP) is applied to one or both sides of the substrate to finish the respective surfaces.

[0005] SiC single crystals, and substrates made therefrom, are known to exhibit high brittleness (or low ductility, respectively). During the multi-step mechanical processing of the bulk SiC crystals and SiC substrates described above, these crystals and substrates are subjected to large mechanical forces. In particular, for example 4H-SiC, the shape

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[0008] In the mechanical processing of single crystal SiC semi-finished cylinders, setting the outer diameter by grinding is the most critical processing step since most of the forces acting by the grinding tool, e.g. a grinding wheel, are applied perpendicular to the cylinder outer diameter.

[0009] In the mechanical processing of single crystal SiC substrates, both the steps of machining as well as the grinding of the substrate edge are of crucial importance. For example, when chamfering the substrate edge, a radial force is applied to the substrate outer diameter by the cup grinding wheel. During grinding, in which the substrate is guided into rotor disks, a radial force likewise acts on the substrate outer diameter from these rotor disks.

[0010] As a result, special attention must be paid to the high brittleness of SiC material combined with the presence of cleavage lattice planes during mechanical processing of the respective bulk crystals and substrates.

[0011] So far, existing prior art techniques have not addressed the anisotropy of the mechanical properties of the SiC crystal lattice, and so in practice it has generally been accepted that there will always be some waste of bulk crystals and substrates due to cracks that develop during mechanical processing, which in turn negatively impact the yield of the entire processing chain.

[0012] During the mechanical processing of the SiC semi-finished cylinder's periphery, the occurrence of cracks and fissures can be reduced within certain limits, if not completely eliminated, by adjusting the parameters of the mechanical processing step itself, such as the applied force and the grinding speed. However, this has a negative effect on other processing parameters, such as an increase in processing duration and costs. Breaks or cracks during mechanical processing of the raw SiC substrate obtained after cutting the SiC semi-finished cylinder with a wire saw (e.g. during edge chamfering, mechanical grinding, mechanical or chemical-mechanical polishing, etc.) can also be reduced by adjusting the processing parameters, but cannot be completely avoided. Such adjustments also have a negative effect on other processing parameters, such as a significant increase in the duration of the mechanical processing of the substrate.

[0013] Several solutions have been attempted to reduce the amount of defective SiC semi-finished cylinders and substrates.

[0014] For example, DE 10 2009 048 868 A1 describes a method for thermal post-treatment of SiC crystals, which makes it possible to reduce the stresses in the crystal and therefore also to reduce the susceptibility of the SiC crystal to cracking.

[0015] CN Patent No. 110067020 describes a treatment to reduce the inherent stress in the crystals already during manufacture, which should make them less susceptible to cracking.

[0016] However, none of these prior art methods take into account the special requirements regarding crystal orientation that are imposed on the processing of single crystal SiC semi-finished products or substrates due to the anisotropy of their mechanical properties. Furthermore, the influence of crystal orientation on the susceptibility of SiC semi-finished products and / or SiC substrates is not taken into account in these prior art methods. Both methods describe a reduction in internal stresses and therefore a general reduction in cracks due to a reduction in crystal stresses.

[0017] However, no solution is disclosed for reducing the occurrence of cracks, which during mechanical processing may appear in low or even stress-free SiC semi-finished products or SiC substrates depending on the applied mechanical forces.

[0018] Therefore, there is a need for a solution that allows for efficiently reducing the amount of defective SiC semi-finished products and / or respective SiC substrates caused by crack generation during mechanical processing, while improving the quality and yield of the SiC semi-finished products and the respective SiC substrates, without significantly increasing the overall cost and time of the mechanical processing. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] U.S. Pat. No. 8,865,324 [Patent Document 2] DE 102009048868 A1 [Patent Document 3] Chinese Patent No. 110067020 Summary of the Invention [Problem to be solved by the invention]

[0020] The present invention has been made in consideration of the shortcomings and drawbacks of the prior art, and its object is to provide a single crystal 4H—SiC semi-finished product having improved mechanical robustness against forces applied during mechanical processing of the outer surface of the 4H—SiC single crystal, and a method for producing such a single crystal 4H—SiC semi-finished product. [Means for solving the problem]

[0021] This object is solved by the subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0022] A single crystal 4H—SiC semi-finished product having improved mechanical robustness against cleavage is provided, the 4H—SiC semi-finished product having a longitudinal axis and at least partially curved sides parallel to the longitudinal axis, the crystal structure of the 4H—SiC semi-finished product having a crystalline structure that at each location on the side of the semi-finished product relative to the longitudinal axis:

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[0024] According to another result,

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[0026] Another result showed that the principal axis of the basal plane of the 4H-SiC crystal structure is

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[0031] According to another outcome, the single crystal 4H—SiC semi-finished product further comprises first and second front faces, one or both of the first and second front faces being perpendicular to the longitudinal axis, or the first front face being perpendicular to the longitudinal axis and the second front face being perpendicular to the longitudinal axis.

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[0033] In another outcome, the at least partially curved side has a curvature that defines a cylindrical surface, the longitudinal axis having an axis of symmetry of the cylindrical surface, the cylindrical surface having an outer diameter that substantially corresponds to a given diameter of a substrate wafer obtained by slicing the 4H—SiC semi-finished product, and / or the outer diameter of the cylindrical surface is 150.0 mm±0.5 mm, or 200.0 mm±0.5 mm, and / or the height of the single crystal 4H—SiC semi-finished product is greater than 20 mm, or preferably greater than 15 mm, and / or the single crystal 4H—SiC semi-finished product has a thickness of 1×10 18 cm -3 The 4H-SiC semi-finished products having greater nitrogen doping and / or single crystal have an orientation flat, or notch, having a length of 47.5 mm±1.0 mm.

[0034] The invention also provides a method for producing a single crystal 4H—SiC semi-finished product with improved mechanical robustness against cleavage, the single crystal 4H—SiC semi-finished product having a longitudinal axis and at least partially curved side surfaces parallel to said longitudinal axis, the method comprising:

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[0036] In another work, a given orientation of the 4H-SiC crystal structure is

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[0038] In another embodiment, the method includes:

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[0040] According to another result, the process of setting the predetermined orientation of the 4H-SiC crystal structure relative to the longitudinal axis of the 4H-SiC semi-finished product includes the steps of spatially orienting a 4H-SiC single crystal relative to the alignment axis such that the orientation of the 4H-SiC crystal structure is set at a predetermined tilt in direction and amount of the

[0001] axis of the 4H-SiC crystal structure relative to the alignment axis, and machining an outer surface of the spatially oriented 4H-SiC single crystal relative to the alignment axis to form at least one of at least partially curved side surfaces substantially parallel to the alignment axis and at least one front surface substantially perpendicular to the alignment axis, wherein the longitudinal axis of the 4H-SiC semi-finished product coincides with the alignment axis of the spatially oriented 4H-SiC single crystal.

[0041] In another result, the process of setting a predetermined orientation of the 4H-SiC crystal structure includes orienting a basal plane of the 4H-SiC crystal structure to an initial orientation; orienting the basal plane from the initial orientation to the first orientation; and orienting the 4H-SiC crystal structure to the first orientation.

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[0045] In another outcome, the first tilt angle is 4° and has a tolerance of ±0.5°, and / or the second tilt angle intersects a line segment.

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[0048] According to another result, the process of setting the predetermined orientation of the 4H-SiC crystal structure includes the steps of orienting a basal plane of the 4H-SiC crystal structure to an initial orientation, rotating the basal plane clockwise about the initial orientation by a predetermined rotation angle, and aligning the rotated basal plane with the 4H-SiC crystal structure.

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[0050] According to another result, the process of setting the predetermined orientation of the 4H-SiC crystal structure includes the steps of orienting a basal plane of the 4H-SiC crystal structure to an initial orientation, rotating the basal plane counterclockwise about the initial orientation by a predetermined rotation angle, and aligning the rotated basal plane with the 4H-SiC crystal structure.

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[0052] According to another outcome, the predetermined rotation angle is 0.33° or a value within the range 0.22° to 2.19°, and / or the third tilt angle is 4° with a tolerance of ±0.5°.

[0053] According to another outcome, a process for setting a predetermined orientation of a 4H—SiC crystal structure is performed on an original 4H—SiC single crystal, including performing angular measurements of the 4H—SiC crystal structure to determine the orientation of a principal axis of the basal plane, and a 4H—SiC semi-finished product is obtained after the setting process on the original 4H—SiC single crystal is completed by performing the following steps: machining at least one front surface along said initial orientation; and machining an at least partially curved surface transverse to said initial orientation.

[0054] The accompanying drawings are incorporated in and form a part of this specification for the purpose of explaining the principles of the invention, and are not to be construed as limiting the invention to only the illustrated and described examples of how the invention can be made and used.

[0055] Further features and advantages will become apparent from the following more detailed description of the invention, as illustrated in the accompanying drawings. [Brief description of the drawings]

[0056] FIG. 1 is a schematic perspective view of a single crystal SiC semi-finished product. [Figure 2] Schematic diagram of the on-axis orientation (as viewed from the top, front) of a conventional 4H-SiC semi-finished product or substrate, where the basal plane (0001) is parallel to the front surface and the crystallographic direction

[0001] is at a 0° inclination with respect to the cylindrical symmetry axis C.

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[0001] direction on the plane of FIG. 2. [Figure 3B]

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[0001] crystallographic direction are initially tilted by a tilt angle δ of 4°.

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[0057] Since atomic scale is discussed in this application, it should be noted that the dimensions and relative angles shown in the figures are for purposes of understanding only and are not drawn to scale.

[0058] 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. The present invention may, however, 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 numbers refer to like elements throughout.

[0059] The principle underlying the present invention is based on the inventors' realization that by establishing a given crystal structure orientation with respect to external reference surfaces (e.g., front facet and / or side faces) of the SiC crystal and / or SiC substrate that improves the mechanical robustness of the SiC crystal and substrate without affecting the quality of the epitaxial layers grown on the single crystal SiC substrate, the occurrence of cracks or fissures in the SiC crystal and substrate during respective mechanical processing can be significantly reduced or even eliminated.

[0060] As such, the present invention achieves optimal orientation of the lattice planes of the SiC crystal and substrate, which ensures higher mechanical robustness and improved yields in mechanical processing.

[0061] In SiC crystals, cracks and fissures can affect the shape of 4H-SiC single crystals.

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[0064] For example, FIG. 2 illustrates the geometry of a polar 4H—SiC semi-finished product 200 (or a 4H—SiC substrate) having an on-axis crystal orientation.

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[0087] Basal plane (0001)

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[0001] of the respective crystals are inclined at an inclination angle δ of 4° (±0.5°) with respect to the central axis C of the 4H—SiC substrate.

[0096] As mentioned above, the basal plane (0001)

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[0001] is also reflected in the crystal orientation of some cleavage planes. For example, the 0001-0001 orientation depicted in Figure 2 for an on-axis orientation is

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[0102] A similar situation occurs with a single crystal 4H—SiC semi-finished product 400 having a standard 4° off-axis orientation, as shown in Figures 4A-4B.

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[0001] orientation, and cleavage plane

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[0109] FIG. 4B shows

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[0123] However, 4H-SiC semi-finished products or 4H-SiC substrates with on-axis or 4° off-axis orientations may experience deformation of the above-mentioned cleavage planes during mechanical processing, especially when radial mechanical forces are applied in the regions where the cleavage planes intersect with the respective cylindrical planes aligned with the symmetry axis C.

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[0125] As illustrated in Fig. 5, during mechanical processing of a monocrystalline SiC semi-finished product (or substrate), it can be assumed in a first approximation that the tool used during mechanical processing, such as grinding, exerts a mechanical force F along line segment L (force line) on the surface of the monocrystalline body, and that this force propagates radially towards the monocrystalline body. The determining factor in terms of cleavability is the strength of the force acting inwardly on the monocrystalline SiC semi-finished product, i.e. the radial component F of the total force F. rad The tangential force component (F tang ) can be neglected for the purpose of evaluating their influence on cleavage. The length of the line segment L is approximately the length of the contact area with the respective processing tool, such as the thickness h of the grinding wheel, as illustrated in FIG. 6. In fact, during machining, the mechanical forces are not applied along a single line segment L of length h, but rather in a very narrow area of ​​the same h. This narrow area can be considered as being formed by a series of parallel line segments. The conditions for achieving the reduction of cleavage along the line segments according to the principles of the invention described below thus become applicable to each of these individual line segments.

[0126] To evaluate the effect of the radial mechanical force applied inwardly to the cleavage plane at the contact area, both the contact area as well as the actual length of the line segment L along which the mechanical force is actually applied are taken into account. The length h of the line segment L and / or the narrow area is essentially determined by the thickness h of the processing tool.

[0127] During mechanical processing of SiC semi-finished products with the standard 4° off-axis orientation described above with reference to Figures 4A-4B or with an on-axis orientation as illustrated in Figure 2, a radial force is applied laterally at several positions along the circumference of the crystal cylindrical face, for example by a grinding wheel. The effect of the applied force on whether the crystal will crack or not depends strongly on the position / region along the cylindrical circumference where this force is applied. As illustrated in Figures 7 and 8, the following extreme situations can be characterized with respect to different cleavage plane orientations related to the region of application of the radial force:

[0128] Figure 7 shows the direction

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[0138] Figure 8 is here

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[0147] shape

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[0153] From the above, the cleavage plane

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[0156] The present invention relates to a method for determining the crystal cleavage plane, i.e., the cleavage plane, for a 4H-SiC semi-finished product having an off-axis orientation, such as the 4° off-axis orientation described above.

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[0158] In the following, for ease of explanation, the principle of the present invention will be described as follows:

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[0160] The principle underlying the present invention is to provide a method for the epitaxy of a 4H-SiC substrate by setting a specific crystal orientation of the 4H-SiC crystal structure on a 4H-SiC semi-finished product (or a 4H-SiC substrate) so that the 4H-SiC crystal structure is aligned in the plane of the 4H-SiC substrate, while maintaining the advantages that the off-axis orientation of the direction of

[0001] brings to the epitaxy quality of the respective 4H-SiC substrate.

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[0162] To reduce or avoid the formation of cracks on 4H-SiC semi-finished products with a 4° off-orientation (4°±0.5°), the present invention provides a specific orientation of the crystal structure on the 4H-SiC semi-finished product (or 4H-SiC substrate) for each exterior surface, such as one or both of the side and / or front surfaces of the 4H-SiC semi-finished product. The onset of cracks occurs when the radial force applied during mechanical processing breaks down at least a predetermined minimum number of parallel cleavage planes per unit length of the force line segment L.

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[0165] cleavage plane

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[0169] Number of parallel cleavage planes per unit length of a line of force

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[0173] The present invention provides improved mechanical robustness of the underlying 4H-SiC crystal structure, more specifically the cleavage planes.

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[0175] 9A-9B illustrate a schematic representation of a 4H—SiC preform 500 according to one exemplary embodiment, in which the spatial orientation of the 4H—SiC crystal structure relative to a longitudinal axis C of the 4H—SiC preform 500 (or relative to one or both of its front ends 520 a, 520 b and / or side surfaces 530) is oriented in a direction according to a first tilt angle δ1 (e.g., δ1=4°±0.5° depicted in FIG. 9A ).

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[0181] Thus, the radial force applied during the grinding process, as described above with reference to FIG. 4B, may result in only one or a small number of cleavage planes at a particular location.

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[0183] moreover,

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[0185] 10A-10B illustrate a 4H-SiC preform 600 having another predetermined orientation for improved mechanical robustness, according to another exemplary embodiment. In this configuration, the 4H-SiC preform has a predetermined spatial orientation relative to the longitudinal axis C (or relative to one or both of the front end faces 620a, 620b and / or side faces 630 of the 4H-SiC preform 600), thereby providing an off-axis orientation in the

[0001] direction and an orientation according to a first tilt angle δ1 (e.g., δ1=4°±0.5° depicted in FIG. 10A ).

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[0191] The second tilt angle δ2 is

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[0194] Both exemplary embodiments provide multiple equal parallel cleavage planes per unit length of the force line L to reduce or even eliminate cracking.

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[0196] Similar improvements in mechanical robustness against cleaving are also achieved in 4H—SiC substrates or wafers having the same spatial orientation of the 4H—SiC crystal structure described above with reference to FIGS. 9A-9B and 10A-10B.

[0197] The predetermined orientation of the 4H-SiC crystal structure can be set in the 4H-SiC semi-finished product by the methods described below.

[0198] In the original 4H—SiC crystal (pretreated 4H—SiC crystal) obtained after crystal growth and / or a first rough mechanical treatment, the lattice planes and the reference plane (e.g., one of the treated front facets or cylindrical faces) are not yet aligned with each other with the required precise orientation as in the final 4H—SiC semi-finished product.

[0199] For this reason, at the beginning of the mechanical processing, the raw 4H-SiC crystal (or the pre-processed 4H-SiC crystal) is aligned on one side of its front facet (the Si side (0001) or the C side (0002)).

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[0202] In a subsequent step, the so-oriented raw SiC crystal (or pre-treated SiC single crystal) is orientated using a goniometer to obtain the desired 4° off-axis orientation of the basal plane, which is required for good quality epitaxy of future SiC substrates.

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[0204] The outer diameter of the cylinder is then set to the diameter of the future substrate, for example by a grinding process. The diameter setting process is one of the most critical steps with regard to crack development, as explained above. During this setting process, it is ensured that the previously goniometer adjusted orientation of the grating planes relative to the cylindrical surface is transferred accurately. Furthermore, primary or secondary orientation flats and / or notches can be ground during this processing step. The desired orientation of the grating planes relative to the cylindrical surface is subsequently checked / controlled using an X-ray device before any further processing.

[0205] After processing of the outer diameter and / or orientation flat and controlling the desired orientation of the lattice planes relative to the cylindrical plane, processing is performed to define the front end face of the SiC single crystal, thereby resulting in a final SiC semi-finished product having an outer shape similar to that shown in FIG.

[0206] Lattice surfaces that improve mechanical robustness, such as the predetermined orientation depicted in FIGS. 9A-9B or 10A-10B

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[0208] According to a first orientation processing sequence for setting a predetermined orientation of the SiC crystal structure of 4H-SiC semi-finished product 500 as illustrated in Figures 9A-9B, the original or pre-processed 4H-SiC crystal is spatially oriented such that the basal plane is initially aligned with an initial orientation in which the basal plane is substantially perpendicular to the direction of central alignment axis C (which corresponds to the direction of the future cylindrical side surface 530 of the final 4H-SiC semi-finished product 500). In a subsequent step, the basal plane is aligned with

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[0213] According to an alternative second orientation process sequence for setting a predetermined orientation of the SiC crystal structure in a 4H-SiC semi-finished product 600 as shown in Figures 10A-10B, the basal plane is also first oriented to an initial orientation perpendicular to the direction of the central axis C (which direction coincides with the direction of the future cylindrical side surface 630).

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[0217] In the above-mentioned first and second orientation treatment sequences, the value of the first tilt angle is preferably 4°±0.5°, this ±0.5° error being related to the permissible tolerance of the value of the first tilt angle, which still allows to obtain the desired improvement of the epitaxy properties of the respective semiconductor substrate. The value of the second tilt angle δ2 is preferably 0.023°. However, any value within the range of 0.015°-0.153° may be used for the second tilt angle δ2, which provides the desired effect of the orientation on the mechanical robustness. In particular, the value of the second tilt angle δ2 to be used can be estimated based on the distance between the cleavage planes of the 4H-SiC lattice that are equivalently parallel and whose cleavage action is intended to be minimized, and with reference to at least the predetermined minimum number of intersecting cleavage planes per unit length of the above-mentioned line of force segments.

[0218] According to a third orientation sequence for setting another predetermined orientation that improves mechanical robustness, the basal plane is first aligned to an initial orientation perpendicular to the direction of the central axis C, i.e., to the direction of the future cylindrical side surface. The basal plane is then rotated clockwise around this initial orientation by a predetermined rotation angle. The predetermined rotation angle is 0.33° or a value in the range 0.22°-2.19°. In a subsequent step, the basal plane is aligned to the 4H-SiC crystal structure.

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[0220] Alternatively, a fourth orientation sequence can be used, in which the basal planes are also first aligned with an initial orientation perpendicular to the direction of the central axis C, i.e., to the direction of the future cylindrical side faces. The basal planes are then rotated counterclockwise around this initial orientation by a predetermined rotation angle. The predetermined rotation angle is preferably 0.33°, but may be any value in the range 0.22°-2.19° to achieve the desired effect of orientation on mechanical robustness. In a subsequent step, the basal planes are aligned with the 4H-SiC crystal structure.

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[0222] After the crystal orientation of the original SiC crystal (or preprocessed SiC crystal) has been aligned by any of the orientation processing sequences described above, one or more external reference surfaces of the final 4H—SiC semi-finished product may be machined relative to the alignment axis C. For example, an at least partially curved side surface may be machined on the oriented original or preprocessed 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 may be machined in a direction perpendicular to the C-axis.

[0223] In this way, a predetermined orientation of the basal plane (0001) and other lattice planes of the 4H—SiC structure can be precisely set relative to at least one reference plane of the 4H—SiC semi-finished product, i.e., one or both of the curved side faces and / or its front face.

[0224] The diameter of the curved side can be set to substantially match the intended diameter of the substrate wafer to be sliced ​​from the 4H-SiC semi-finished product. In particular, the technique of the present invention can be applied to improve the mechanical robustness of 4H-SiC semi-finished products having an outer diameter of 150.0 mm ± 0.5 mm, 200.0 mm ± 0.5 mm, or 250 mm ± 0.5 mm, and the 4H-SiC substrates obtained therefrom. The ± 0.5 mm error in the outer diameter corresponds to the tolerance associated with standard grinding processes. However, depending on the technique used to set the side of the 4H-SiC semi-finished product and / or to adjust the outer diameter, the diameter tolerance can be greater or less than 0.5 mm.

[0225] Furthermore, the techniques of the present invention can be applied to improve the mechanical robustness of 4H—SiC semi-finished products having heights in the direction of the longitudinal axis C greater than 20 mm, or preferably greater than 15 mm. However, the present invention is also applicable to 4H—SiC semi-finished products or original 4H—SiC crystals of any height, which has been preselected to result in a desired number of 4H—SiC substrate slices.

[0226] The set of SiC semi-finished products with a predetermined orientation of the 4H-SiC lattice for improved mechanical robustness can then be separated into substrate wafers using commonly known wafer separation processes such as multi-wire sawing with 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 referencing one of the reference planes of the SiC semi-finished products during the separation process.

[0227] An alternative exemplary embodiment for supporting a SiC workpiece during wafer separation processing and transferring a predetermined orientation of the underlying 4H-SiC lattice to a SiC substrate is illustrated in FIGS.

[0228] 11 illustrates an arrangement in which the crystal orientation of a single crystal SiC semi-finished product 700, such as any of the single crystal SiC semi-finished products 500, 600 described above, is transferred to a SiC substrate 740 via a cylindrical side surface 730. In the case of a splitting process in which the support of the single crystal SiC semi-finished product 700 to be processed is performed by supporting the cylindrical side surface 730, the cylindrical side surface 730 requires precise alignment to the orientation of the SiC lattice planes. In this splitting method, the orientation of the lattice planes is thus transferred via the respective orientation to the cylindrical side surface 730.

[0229] FIG. 12 illustrates a configuration in which the monocrystalline SiC semifinished product 700 is supported on one of its front faces 720b. In the case of separation processes in which the support of the monocrystalline SiC semifinished product to be processed is performed by supporting the front face, the front face requires a precise alignment with respect to the orientation of the lattice planes. In these separation methods, the orientation of the lattice planes of the SiC is transferred by the alignment of one of the cylindrical front faces 720b with respect to the lattice planes. In this case, the orientation of the lattice planes with respect to the front face 720b for the support is preferably measured using X-ray photography set up with a goniometer and is precisely transferred during mechanical processing, for example using a grinding process. In order to precisely transfer the predetermined orientation of the 4H-SiC lattice planes to the substrate wafer 740, one of the following basic conditions must be met by the monocrystalline SiC semifinished product 700:

[0230] At least one of both front end faces 720a and / or 720b (the reference plane) is oriented perpendicular to the side surface 730 of the cylinder, i.e. the grating orientation is precisely transferred via one of the reference planes. - Both front end faces 720a, 720b (reference faces) are oriented perpendicular to the cylindrical side face 730, i.e. the grating orientation can be accurately transferred via both reference faces. - one of the front end faces 720a or 720b (the reference face) is oriented exactly perpendicular to the cylindrical side face 730, and the second front end face 720b or 720a is oriented in the direction

[0231]

number

[0232] In conclusion, the present invention makes it possible to reduce the occurrence of cracks during mechanical processing of 4H-SiC single crystals and / or 4H-SiC substrates by setting an optimal orientation of the preferred cleavage planes relative to the side surfaces and / or one or both front surfaces of the SiC semi-finished product (or 4H-SiC substrate) such that a radial mechanical force applied to a given area is always distributed over at least a predetermined minimum number of preferred cleavage planes, regardless of the position around the circumference of the SiC semi-finished product to which the mechanical force is applied.

[0233] As a result, this optimal orientation of the 4H-SiC crystal structure makes it possible to achieve a higher mechanical robustness during mechanical processing of the bulk SiC crystal and the SiC substrate and thus a higher yield of single crystal semi-finished and final products without compromising the epitaxy quality of the future substrate and without a significant increase in the cost and / or time of the respective mechanical processing.

[0234] While certain features of the above exemplary embodiments have been described using terms such as "downward" and "horizontal," these terms are used solely to facilitate the description of the respective features and their relative orientation 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 any particular spatial orientation. Furthermore, while the invention has been described above with respect to 4H-SiC crystals, the principles of the invention may also be advantageously applied to other modified SiC single crystals, and / or other semiconductor single crystals such as AlN and GaN. [Explanation of symbols]

[0235] C Geometric longitudinal axis L line segment h Height of the grinding wheel, length of the line segment L 100 SiC semi-finished products 110 Orientation Flat (OF) 120a, 120b Upper and lower front faces of the cylinder 130 Side cylindrical surface 200 SiC semi-finished product with axial orientation (conventional technology) 220 Front 230 Cylinder Side 240 Grinding Wheel 300 SiC substrate with 4° off-orientation (conventional technology) 320a, 320b Upper and lower front faces of the cylinder 330 Cylinder Side 400 SiC semi-finished product with 4° off-orientation (conventional technology) 420a, 420b Upper and lower front faces of the cylinder 430 Cylinder Side 500 SiC semi-finished products 520a, 520b Upper and lower front faces of the cylinder 530 Cylinder Side 600 SiC semi-finished products 620a, 620b Upper and lower front faces of the cylinder 630 Cylinder Side 700 Single crystal SiC semi-finished products 710 Support 720a, 720b, and 730 front and side faces 740 Substrate Wafer

Claims

1. 1. A single crystal 4H—SiC semi-finished product having improved mechanical robustness against cleaving, the semi-finished product having a longitudinal axis and at least partially curved sides parallel to the longitudinal axis; the single crystal 4H—SiC semi-finished product is an oriented crystal cylinder having a height along the longitudinal axis selected to obtain a desired number of single crystal 4H—SiC substrate slices; The crystal structure of the 4H—SiC semi-finished product has a structure in which, at each position on a side of the semi-finished product with respect to the longitudinal axis, [0010] shaped cleavage planes oriented such that there are at least a predetermined minimum number of lines intersecting the parallel cleavage planes per millimeter on the side surface; the line segment is defined by a plane that is tangent to the side surface at the location at a single point and is parallel to the longitudinal axis; a principal axis [0001] of a basal plane of the 4H—SiC crystal structure is tilted at a first angle relative to the longitudinal axis; [0025] It is inclined in the direction wherein the first tilt angle is 4° with a tolerance of ±0.5°; The principal axis [0001] of the basal plane of the 4H—SiC crystal structure is [0030] Direction or [0045] inclined at a second inclination angle in either direction; The second tilt angle is a value selected from the range of 0.015° to 0.153°, The above [0050] said predetermined minimum number of parallel cleavage planes of a feature is at least 1000 planes per millimeter of said line segment; Parallel cleavage planes intersecting the line segment [006] is less than 10,000 per millimeter of the length of the line segment, The above [0070] The cleavage surface having the shape of a cleavage surface [0080] ， [0090] , and [0010] A single crystal 4H-SiC semi-finished product comprising:

2. 2. The single crystal 4H-SiC semi-finished product of claim 1, wherein said longitudinal axis is the axis of symmetry of a cylinder defined by the curvature of said at least partially curved side surface of said 4H-SiC semi-finished product.

3. 3. The semi-finished single crystal 4H-SiC product of claim 1, wherein the second tilt angle is 0.023°.

4. further comprising first and second front surfaces; one or both of the first and second front surfaces are perpendicular to the longitudinal axis; or The first front surface is perpendicular to the longitudinal axis, and the second front surface is perpendicular to the longitudinal axis. ##EQU00011## 4. The single crystal 4H—SiC semi-finished product of claim 1, wherein the semi-finished product is oriented to obtain a total thickness variation of between 40 μm and 340 μm of the second front surface relative to the first front surface, measured along a direction.

5. 5. The single crystal 4H—SiC semi-finished product of claim 1, wherein the at least partially curved side has a curvature defining a cylindrical surface having an axis of symmetry about the longitudinal axis, the cylindrical surface having an outer diameter that substantially corresponds to a given diameter of a substrate wafer obtained by slicing the 4H—SiC semi-finished product.

6. 6. The single crystal 4H-SiC semi-finished product of claim 5, wherein 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.

7. 7. The method of claim 5, wherein the height of the single crystal 4H-SiC semi-finished product is greater than 20 mm.

8. The single crystal 4H—SiC semi-finished product is 1×10 １８ cm -３ A monocrystalline 4H-SiC semi-finished product according to any one of claims 5 to 7, having a higher nitrogen doping.

9. 9. The single crystal 4H-SiC semi-finished product of claim 5, wherein the single crystal 4H-SiC semi-finished product has an orientation flat or notch having a length of 47.5 mm±1.0 mm.

10. 1. A method for producing a single crystal 4H—SiC semi-finished product having improved mechanical robustness against cleaving, the single crystal 4H—SiC semi-finished product having a longitudinal axis and at least partially curved sides parallel to the longitudinal axis, the single crystal 4H—SiC semi-finished product being an oriented crystal cylinder having a height along the longitudinal axis selected to obtain a desired number of single crystal 4H—SiC substrate slices, the method comprising: At each position of the side of the 4H-SiC semi-finished product, ##EQU00012## performing a process to set a predetermined orientation of the 4H—SiC crystal structure relative to the longitudinal axis such that there are line segments on the side that intersect with at least a predetermined minimum number of parallel cleavage planes per millimeter of a shaped cleavage plane; the line segment is defined by a plane that is tangent to the side surface at the location at a single point and is parallel to the longitudinal axis; a principal axis [0001] of a basal plane of the 4H—SiC crystal structure is tilted at a first angle relative to the longitudinal axis; ##EQU00013## It is inclined in the direction wherein the first tilt angle is 4° with a tolerance of ±0.5°; The principal axis [0001] of the basal plane of the 4H—SiC crystal structure is ##EQU14## Direction or ##EQU00015## inclined at a second inclination angle in either direction; The second tilt angle is a value selected from the range of 0.015° to 0.153°, The predetermined orientation of the 4H—SiC crystal structure is ##EQU00016## said predetermined minimum number of parallel cleavage planes of a feature is such that there are at least 1000 planes per millimeter of said line segment; and Parallel cleavage planes intersecting the line segment ##EQU00017## is less than 10,000 per millimeter of the length of the line segment, The above [0018] The cleavage surface having the shape of a cleavage surface [0019] ， [0020] , and ##EQU00021## The method according to claim 1,

11. said treatment for setting said predetermined orientation of said 4H—SiC crystal structure relative to said longitudinal axis of said 4H—SiC semi-finished product further comprising: spatially orienting the 4H—SiC single crystal with respect to the alignment axis such that the orientation of the 4H—SiC crystal structure is set at a predetermined tilt in direction and amount of a principal axis [0001] of the basal plane of the 4H—SiC crystal structure with respect to the alignment axis; machining an outer surface of the spatially oriented 4H—SiC single crystal relative to the alignment axis; an at least partially curved side substantially parallel to the alignment axis; and At least one front surface substantially perpendicular to the alignment axis. and forming at least one of 11. The method of claim 10, wherein the longitudinal axis of the 4H-SiC semi-finished product coincides with the alignment axis of the spatially oriented 4H-SiC single crystal.

12. said treatment for setting a predetermined orientation of said 4H—SiC crystal structure further comprising: orienting a basal plane of the 4H—SiC crystal structure to an initial orientation; the basal plane from the initial orientation to a first orientation; [0022] tilting the optical axis in a first tilt angle direction; the basal plane from the first orientation to a second orientation; [0023] Direction or ##EQU00024## and tilting the second tilt angle in either direction, The method of claim 10, wherein in the initial orientation, the basal plane is substantially perpendicular to the longitudinal axis of the 4H—SiC semi-finished product.

13. 13. The method of claim 11 or 12, wherein the second tilt angle is 0.023°.

14. said treatment for setting said predetermined orientation of said 4H—SiC crystal structure further comprising: orienting a basal plane of the 4H—SiC crystal structure to an initial orientation that is perpendicular to the direction of the central axis C; rotating the base surface clockwise about the initial orientation by a predetermined rotation angle, the predetermined rotation angle being a value within the range 0.22° to 2.19°; The rotated basal plane of the 4H—SiC crystal structure [0025] and tilting the lens in a direction by a third tilt angle, the third tilt angle being 4° with a tolerance of ±0.5°; The method of claim 10, wherein in the initial orientation, the basal surface is substantially perpendicular to the longitudinal axis of the 4H—SiC semi-finished product.

15. said treatment for setting said predetermined orientation of said 4H—SiC crystal structure further comprising: orienting a basal plane of the 4H—SiC crystal structure to an initial orientation that is perpendicular to the direction of the central axis C; rotating the base surface counterclockwise about the initial orientation through a predetermined rotation angle, the predetermined rotation angle being a value within the range 0.22° to 2.19°; The rotated basal plane of the 4H—SiC crystal structure [0026] and tilting the lens in a direction by a third tilt angle, the third tilt angle being 4° with a tolerance of ±0.5°; The method of claim 10, wherein in the initial orientation, the basal surface is substantially perpendicular to the longitudinal axis of the 4H—SiC semi-finished product.

16. 16. The method of claim 14 or 15, wherein the predetermined rotation angle is 0.33°.

17. the process of establishing the predetermined orientation of the 4H—SiC crystal structure is performed on an original 4H—SiC single crystal, and includes performing an angular measurement of the 4H—SiC crystal structure to determine the orientation of the principal axis [0001] of the basal plane; After the setting step is completed for the raw 4H—SiC single crystal, the 4H—SiC semi-finished product has the following properties: machining at least one front surface in a direction perpendicular to the alignment axis; machining the at least partially curved surface in a direction parallel to an alignment axis; The method according to any one of claims 10 to 16, obtained by carrying out

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