SiC substrate and SiC composite substrate

Abstract

The present invention provides a SiC substrate capable of reducing cracking and cracking during substrate processing. The SiC substrate is provided with a biaxially oriented SiC layer, and when the entire region of an XRT image obtained by X-ray topography (XRT) measurement of the biaxially oriented SiC layer is divided into a lattice shape in which a region having a longitudinal direction of 4 mm * a transverse direction of 4 mm * a depth of 28 [mu] m is given per lattice, X (cm / cm < 3 >) represents the average volume density of basal plane dislocations (BPD) per lattice, and X (cm / cm < 3 >) represents the average volume density of the basal plane dislocations (BPD) per lattice. There are no continuous 10 cells or more on one vertical and horizontal straight line in a region that reaches 5X (cm / cm < 3 >) or more per cell.

Description

Technical Field

[0001] This invention relates to SiC substrates and SiC composite substrates. Background Technology

[0002] Silicon carbide (SiC) has attracted considerable attention as a wide-bandgap material capable of controlling high voltage and high power with low loss. In particular, in recent years, power semiconductor devices using SiC materials (SiC power devices) have demonstrated superior miniaturization, low power consumption, and high efficiency compared to power devices using Si semiconductors, thus promising applications in a wide variety of fields. For example, by employing SiC power devices, the efficiency of converters, inverters, and on-board chargers used in electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) can be improved through miniaturization. Therefore, the development of SiC wafers, which form the core of SiC power devices, is of great interest.

[0003] To fabricate SiC power devices, SiC single crystals need to be epitaxially grown on a SiC single crystal substrate. The resulting SiC single crystal substrate contains a large number of dislocations, which are broadly classified into three types: basal plane dislocations (BPD), screw dislocations (TSD), and edge dislocations (TED). Within these dislocations, basal plane dislocations can transfer to the epitaxially grown film. If they exist in the driving region of the device, they can expand into stacking defects due to current flow, adversely affecting the reliability of the SiC device. Regarding these dislocations, Patent Document 1 (Japanese Patent No. 6192948) discloses a SiC single crystal with regions biased towards edge dislocations and regions biased towards basal plane dislocations. It describes how such a SiC single crystal can suppress characteristic degradation caused by specific types of dislocations. Patent document 2 (Japanese Patent No. 5750363) discloses a SiC single crystal with a volume density of 3700 cm³ / cm² for dislocations (mainly basal dislocations and through-type edge dislocations) having Burgs vectors in the {0001} plane direction. 3 The following is a region with low dislocation density. Furthermore, it is known that cracking or fissures occur during the processing of SiC single-crystal substrates. In this regard, Non-Patent Literature 1 (Y. Qiusheng, C. Senkai and P. Jisheng, “Surface and subsurface cracks characteristics of single crystal SiC wafer in surface machining,” AIP Conference Proceedings 1653, 020091 (2015)) describes various processing methods performed on single-crystal SiC wafers and the analysis of the crack characteristics generated on the wafer surface as a result.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6192948

[0007] Patent Document 2: Japanese Patent No. 5750363

[0008] Non-patent literature

[0009] Non-patent document 1: Y.Qiusheng, C.Senkai and P.Jisheng, "Surface and subsurfacecracks characteristics of single crystal SiC wafer in surface machining," AIPConference Proceedings 1653,020091(2015) Summary of the Invention

[0010] According to the disclosure in Non-Patent Document 1, SiC is extremely hard and difficult to process. The reduced yield caused by cracking and fissures during wafer grinding, polishing, and cutting is a problem. The direct cause is unclear, but it may be related to deformation within the crystal, such as plastic deformation caused by dislocations. In this regard, the dislocation bias distribution in SiC single crystals disclosed in Patent Documents 1 and 2 is considered to easily lead to cracking and fissures during substrate processing such as grinding, polishing, and cutting of SiC substrates.

[0011] The inventors of this invention have recently come to the following insight: by using a biaxially oriented SiC layer with a large number of BPDs in a small area (i.e., a uniform distribution of BPDs) on a SiC substrate, the deformation within the crystals of the SiC substrate is reduced, which can reduce cracking and fissures during substrate processing such as grinding, polishing, and cutting.

[0012] Therefore, the object of the present invention is to provide a SiC substrate that can reduce cracking and fissures during substrate processing.

[0013] According to the present invention, the following solution is provided.

[0014] [Option 1]

[0015] A SiC substrate having a biaxially oriented SiC layer.

[0016] The SiC substrate is characterized in that...

[0017] In the XRT image obtained by X-ray morphology (XRT) measurement of the biaxially oriented SiC layer, the entire XRT image area is divided into a lattice with each cell being 4 mm x 4 mm x 28 μm deep. The average volume density of basal dislocations (BPDs) in each cell is set as X (cm / cm²). 3 When ), each grid reaches 5X (cm / cm) 3 The above areas do not have more than 10 consecutive grids on either a vertical or horizontal straight line.

[0018] [Scheme 2]

[0019] The SiC substrate according to Scheme 1 is characterized in that...

[0020] In the XRT image, each frame reaches 3X (cm / cm) 3 The above areas do not have more than 5 consecutive squares on either a vertical or horizontal straight line.

[0021] [Option 3]

[0022] The SiC substrate according to scheme 1 or 2 is characterized in that,

[0023] When the entire XRT image is divided into a grid of 4mm x 4mm sections, and the average number density of spiral dislocations (TSDs) in each section is set to Y ( / cm²),... 2 When ), each grid reaches 2Y ( / cm) 2 The above areas do not have more than 10 consecutive grids on either a vertical or horizontal straight line.

[0024] [Option 4]

[0025] The SiC substrate according to any one of claims 1 to 3 is characterized in that,

[0026] When the entire XRT image is divided into a grid of 4mm x 4mm sections, and the average number density of edge dislocations (TED) in each section is set to Z ( / cm²),... 2 When ), each grid reaches 2Z ( / cm) 2 The above areas do not have more than 10 consecutive grids on either a vertical or horizontal straight line.

[0027] [Option 5]

[0028] The SiC substrate according to any one of claims 1 to 4 is characterized in that,

[0029] X is 200–5000 cm / cm 3 .

[0030] [Option 6]

[0031] The SiC substrate according to any one of claims 1 to 5 is characterized in that,

[0032] The rare earth element concentration of the biaxially oriented SiC layer is 2.0 × 10⁻⁶. 14 ~5.0×10 15 atoms / cm 3 .

[0033] [Option 7]

[0034] A SiC composite substrate, characterized in that it comprises:

[0035] SiC single crystal substrate; and

[0036] The SiC substrate described in any one of Schemes 1 to 6 on the SiC single crystal substrate. Attached Figure Description

[0037] Figure 1 This is a longitudinal cross-sectional view of the SiC composite substrate 10.

[0038] Figure 2 This is a manufacturing process diagram of the SiC composite substrate 10.

[0039] Figure 3 This is a conceptual diagram showing the configuration of an aerosol deposition (AD) device 50.

[0040] Figure 4 For the sample in Example 1, based on the XRT image, 5X (cm / cm) was achieved for each grid. 3 This is a diagram showing the analysis of the area above and its display as blacked-out squares. Detailed Implementation

[0041] SiC substrate

[0042] The SiC substrate of the present invention has a biaxially oriented SiC layer. In the XRT image obtained by X-ray morphology (XRT) measurement of the biaxially oriented SiC layer, if the entire XRT image area is divided into a lattice with each cell being 4 mm x 4 mm x 28 μm deep, the average volume density of basal dislocations (BPDs) in each cell is set as X (cm / cm²). 3 At this point, in the biaxially oriented SiC layer, each cell reaches 5X (cm / cm). 3The areas described above do not have more than 10 consecutive squares on either a vertical or horizontal straight line. It should be noted that "no more than 10 consecutive squares on either a vertical or horizontal straight line" only counts the number of consecutive squares on a vertical straight line and a horizontal straight line, not on a diagonal straight line. By using a biaxially oriented SiC layer with a large number of BPDs (i.e., uniform BPD distribution) in such a SiC substrate, the deformation within the crystal structure of the SiC substrate is reduced, thus decreasing cracking and fissures during substrate processing such as grinding, polishing, and cutting.

[0043] As mentioned above, SiC is extremely hard and difficult to process, and the resulting cracks and fissures during wafer grinding, polishing, and cutting contribute to reduced yield. In this regard, the dislocation bias distribution within the SiC substrate easily leads to cracks and fissures during substrate processing such as grinding, polishing, and cutting. According to the present invention, this problem can be effectively eliminated. Therefore, the yield during SiC substrate manufacturing can be improved.

[0044] Regarding the biaxially oriented SiC layer of the SiC substrate of the present invention, when the XRT image obtained by XRT measurement is divided into a grid with each grid having a vertical dimension of 4 mm, a horizontal dimension of 4 mm, and a depth of 28 μm, the average value of the BPD volume density of each grid is set as X (cm / cm²). 3 When ), each grid reaches 5X (cm / cm) 3 The area described above has no more than 10 consecutive frames on each of its horizontal and vertical straight lines, preferably no more than 5 consecutive frames, and more preferably no more than 2 consecutive frames. Furthermore, in the aforementioned XRT image, it is preferable that each frame reaches 3X (cm / cm). 3 The areas described above have no more than 5 consecutive cells on each of a straight line (both longitudinal and transverse), more preferably no more than 4 consecutive cells, and even more preferably no more than 3 consecutive cells. By reducing the number of areas with a high concentration of BPDs in this way, cracking and breakage during substrate processing can be reduced more effectively. Furthermore, the average volume density X of each BPD cell is preferably 200–5000 cm³ / cm². 3 .

[0045] Regarding biaxially oriented SiC layers, in XRT images obtained through XRT measurements, the entire XRT image area is divided into a grid of 4mm x 4mm sections. The average TSD number density of each section is set as Y ( / cm²). 2 When ), it is preferable to achieve 2Y ( / cm) per grid. 2The areas described above have no more than 10 consecutive cells on each of the horizontal and vertical straight lines, more preferably no more than 6 consecutive cells. By reducing the number of areas with extremely high TSD density in this way, cracking and fissures during substrate processing can be reduced more effectively. In addition, the average value Y of the TSD number density per cell is preferably 100 to 800 / cm². 2 .

[0046] Regarding biaxially oriented SiC layers, in XRT images obtained through XRT measurements, the entire XRT image area is divided into a grid of 4mm x 4mm sections. The average number density of TEDs in each section is set as Z ( / cm²). 2 When ), it is preferable to achieve 2Z ( / cm) per grid. 2 The areas described above have no more than 10 consecutive cells on each of the horizontal and vertical straight lines, and more preferably no more than 4 consecutive cells. By reducing the number of areas with a high density of TEDs, cracking and fissures during substrate processing can be reduced more effectively. Furthermore, the average value Z of the TED density per cell is preferably 1000–8000 / cm². 2 .

[0047] The SiC substrate and even the biaxially oriented SiC layer may have an off-angle. In this case, the off-angle is preferably 0.1 to 12° with respect to the

[0001] axis of the SiC substrate and even the biaxially oriented SiC layer, and more preferably 1 to 5°.

[0048] The biaxially oriented SiC layer preferably contains rare earth elements. Examples of rare earth elements include: Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and combinations thereof. From the viewpoint of reducing cracking and fissures, Y is the preferred rare earth element.

[0049] When the biaxially oriented SiC layer contains rare earth elements, the preferred rare earth element concentration in the biaxially oriented SiC layer is 2.0 × 10⁻⁶. 14 ~5.0×10 15 atoms / cm 3 More preferably 5.0×10 14 ~2.0×10 15 atoms / cm 3 By adjusting the concentration of rare earth elements within the aforementioned range, it is possible to effectively fabricate biaxially oriented SiC layers with a high number of biaxially oriented phases (BPDs) and fewer regions.

[0050] The biaxially oriented SiC layer is preferably oriented along both the c-axis and a-axis. Furthermore, the SiC substrate is preferably composed of a biaxially oriented SiC layer. The biaxially oriented SiC layer can be oriented along both the c-axis and a-axis, and can be a single crystal, a polycrystalline SiC, or a mosaic crystal. Mosaic crystal refers to a collection of crystals without distinct grain boundaries, where the orientation of the crystals differs slightly from one or both of the c-axis and a-axis. The method for evaluating the orientation is not particularly limited; for example, known analytical methods such as EBSD (Electron Back Scatter Diffraction Patterns) and X-ray pole figures can be used. For example, when using EBSD, the inverse pole figure mapping of the surface (plate surface) or a cross-section orthogonal to the plate surface of the biaxially oriented SiC layer is measured. In the obtained inverse pole figure mapping, a biaxial orientation along the approximate normal direction and the approximate plate surface direction can be defined when the following four conditions (A) to (D) are met: (A) a specific orientation (first axis) along the approximate normal direction of the plate surface; (B) a specific orientation (second axis) along a direction orthogonal to the first axis and generally within the plate surface; (C) the tilt angle relative to the first axis is distributed within ±10°; and (D) the tilt angle relative to the second axis is distributed within ±10°. In other words, when the above four conditions are met, it is determined that the orientation is biaxial along the c-axis and a-axis. For example, if the approximate normal direction of the plate surface is oriented along the c-axis, the orientation along the specific orientation (e.g., the a-axis) orthogonal to the c-axis in the direction generally within the plate surface is sufficient. The biaxial orientation of the SiC layer can be biaxial along the approximate normal direction and the approximate in-plane direction; however, it is preferable that the approximate normal direction is oriented along the c-axis. When the tilt angle distribution in the approximate normal direction and / or approximate in-plane direction is small, the mosaicism of the biaxially oriented SiC layer decreases, and the closer it is to zero, the closer it is to a single crystal. Therefore, from the viewpoint of the crystallinity of the biaxially oriented SiC layer, the tilt angle distribution is preferably small in both the approximate normal direction and the approximate in-plane direction, for example, more preferably ±5° or less, and even more preferably ±3° or less.

[0051] SiC composite substrate

[0052] The SiC substrate of the present invention is preferably in the form of a SiC composite substrate. That is, according to a preferred embodiment of the present invention, a SiC composite substrate comprising a SiC single-crystal substrate and the aforementioned SiC substrate on the SiC single-crystal substrate is provided. In this way, by having a SiC composite substrate having a SiC substrate with a small area of ​​BPD (i.e., uniform distribution of BPD), cracking and fissures during substrate processing can be reduced.

[0053] Typically, the SiC single-crystal substrate is a layer composed of SiC single crystals and has a crystal growth surface. The SiC single-crystal substrate preferably has an off-center angle. The polytype, off-center angle, and polarity of the SiC single crystal are not particularly limited; the polytype is preferably 4H or 6H, the off-center angle is preferably 0.1–12° relative to the

[0001] axis of the single-crystal SiC, and the polarity can be either the Si plane or the C plane. More preferably, the polytype is 4H, the off-center angle is 1–5° relative to the

[0001] axis of the single-crystal SiC, and the polarity can be either the Si plane or the C plane.

[0054] The SiC substrate of this invention can be a freestanding substrate containing only a biaxially oriented SiC layer, or a SiC composite substrate accompanied by a SiC single-crystal substrate. Therefore, the biaxially oriented SiC layer can be ultimately separated from the SiC single-crystal substrate as needed. Separation of the SiC single-crystal substrate can be performed using known methods and is not particularly limited. Examples include: methods for separating the biaxially oriented SiC layer using a wire saw, methods for separating the biaxially oriented SiC layer using electrical discharge machining, and methods for separating the biaxially oriented SiC layer using a laser. Furthermore, in the case where the biaxially oriented SiC layer is epitaxially grown on the SiC single-crystal substrate, the biaxially oriented SiC layer can be placed on another support substrate after separating the SiC single-crystal substrate. The material of the other support substrate is not particularly limited; an ideal material can be selected from the viewpoint of material properties. Examples, from the viewpoint of thermal conductivity, include: metal substrates such as Cu, ceramic substrates such as SiC and AlN, etc.

[0055] Manufacturing method of SiC composite substrate

[0056] The SiC composite substrate of the present invention can be readily manufactured as follows: (a) forming a predetermined orientation precursor layer on a SiC single-crystal substrate; (b) heat-treating the orientation precursor layer on the SiC single-crystal substrate to transform at least a portion of it near the SiC single-crystal substrate into a SiC substrate (biaxially oriented SiC layer); and (c) performing grinding, polishing, or other processing to expose the surface of the biaxially oriented SiC layer. However, the manufacturing method of the SiC composite substrate is not limited, as long as a SiC substrate with a small area of ​​biaxially oriented SiC layer and a high number of dislocation distributions (BPDs) as described above can be obtained. For example, a vapor phase method such as CVD or sublimation can be used, or a liquid phase method such as a solution method can be used. To obtain a biaxially oriented SiC layer with uniformly controlled dislocation distribution, as described later, it is preferable to control the amount of rare earth elements added during the formation of the orientation precursor layer, the film formation conditions (carrier gas flow rate, nozzle size) during the formation of the orientation precursor layer, and the heat treatment conditions of the orientation precursor layer. According to such a manufacturing method, it is possible to produce SiC substrates with a large number of BPDs and a small number of biaxially oriented SiC layers, thereby effectively reducing cracking and fissures during the processing of SiC substrates and SiC composite substrates using such SiC substrates.

[0057] The preferred manufacturing method for SiC composite substrates will be described below. Figure 1 This is a longitudinal cross-sectional view of the SiC composite substrate 10 (a cross-sectional view of the SiC composite substrate 10 when it is longitudinally cut along a surface including the central axis of the SiC composite substrate 10). Figure 2 This is a manufacturing process diagram of the SiC composite substrate 10.

[0058] like Figure 1 As shown, the SiC composite substrate 10 of this embodiment includes: a SiC single crystal substrate 20, and a SiC substrate 30 on the SiC single crystal substrate (corresponding to the SiC substrate of the present invention).

[0059] (a) Formation process of orientation precursor layer

[0060] like Figure 2 As shown in (a), the orientation precursor layer 40 becomes a SiC substrate (biaxially oriented SiC layer) 30 through a heat treatment described later. In the formation process of the orientation precursor layer 40, the orientation precursor layer 40 is formed on the crystal growth surface of the SiC single crystal substrate 20.

[0061] The orientation precursor layer 40 can be formed using known methods. Examples of methods for forming the orientation precursor layer 40 include solid-state film formation methods such as AD (aerosol deposition) and HPPD (high-speed plasma particle deposition), sputtering, evaporation, sublimation, various CVD (chemical vapor deposition) methods, and liquid-state film formation methods such as solution growth. Alternatively, the orientation precursor layer 40 can be formed directly on the SiC single-crystal substrate 20. For CVD methods, examples include thermal CVD, plasma CVD, spray CVD, and MO (metal-organic) CVD. Furthermore, the orientation precursor layer 40 can be a polycrystalline material pre-fabricated by sublimation, various CVD methods, sintering, etc., and can be placed on the SiC single-crystal substrate 20. Alternatively, a pre-fabricated shape of the orientation precursor layer 40 can be prepared and then placed on the SiC single-crystal substrate 20. Such an orientation precursor layer 40 can be a cast body made by casting molding or a pressed powder made by pressure molding such as uniaxial pressing.

[0062] When forming the orientation precursor layer 40, it is preferable to include a rare earth compound in the raw material of the orientation precursor layer 40. This allows for control of the concentration of the rare earth compound in the biaxially oriented SiC layer, thereby effectively controlling the distribution of dislocations in the biaxially oriented SiC layer. The rare earth compound is not particularly limited, and examples include oxides, nitrides, carbides, and fluorides of at least one of the 17 rare earth elements mentioned above. Oxides of rare earth elements are preferred, and oxides of Y (yttrium oxide) are more preferred. Furthermore, the distribution of dislocations in the biaxially oriented SiC layer can be effectively controlled by adjusting the flow rate of the carrier gas (e.g., N2) used during the formation of the orientation precursor layer 40.

[0063] It should be noted that in methods for directly forming the orientation precursor layer 40 on the SiC single crystal substrate 20, when using various CVD methods, sublimation methods, solution growth methods, etc., epitaxial growth sometimes occurs on the SiC single crystal substrate 20 without the heat treatment process described later, forming the SiC substrate 30 in a film form. However, the orientation precursor layer 40 is in an unoriented state during formation, i.e., it is amorphous or unoriented polycrystalline. It is preferable to orient it using a SiC single crystal as a seed crystal in a subsequent heat treatment process. This can effectively reduce crystallization defects reaching the surface of the SiC substrate 30. The reason for this is not yet clear, but it is believed that the rearrangement of the crystal structure of the temporarily formed solid phase orientation precursor layer using a SiC single crystal as a seed crystal is effective in eliminating crystallization defects. Therefore, when using various CVD methods, sublimation methods, solution growth methods, etc., it is preferable to select conditions where epitaxial growth does not occur during the formation process of the orientation precursor layer 40.

[0064] However, methods that directly form the alignment precursor layer 40 on the SiC single-crystal substrate 20 using the AD method or various CVD methods are preferred, as are methods that place a separately fabricated polycrystalline material on the SiC single-crystal substrate 20 using sublimation, various CVD methods, sintering, etc. By using these methods, the alignment precursor layer 40 can be formed in a relatively short time. The AD method does not require a high-vacuum process and has a relatively fast film formation speed, making it particularly preferred. In methods using pre-fabricated polycrystalline materials as the alignment precursor layer 40, the surface of the polycrystalline material needs to be sufficiently smoothed beforehand to improve the adhesion between the polycrystalline material and the SiC single-crystal substrate 20. Therefore, from a cost perspective, the method of directly forming the alignment precursor layer 40 is preferred. Additionally, the method of placing a pre-fabricated molded body on the SiC single-crystal substrate 20 is also preferred as a simple method; however, since the alignment precursor layer 40 is composed of powder, a sintering process is required in the heat treatment step described later. Either method can use known conditions; however, the following describes the method of directly forming the orientation precursor layer 40 on the SiC single crystal substrate 20 using the AD method or the thermal CVD method, and the method of placing the pre-made molded body on the SiC single crystal substrate 20.

[0065] Algebraic deposition (AD) is a technique that aerosolizes particulate matter or particulate feedstock by mixing it with a gas, and then ejects the aerosol at high speed from a nozzle to impact a substrate to form a film. It is characterized by its ability to form films at room temperature. An example of a film-forming apparatus (AD apparatus) used in such an AD method is shown below. Figure 3 . Figure 3The AD device 50 shown is configured as an apparatus used in the AD process to spray raw material powder onto a substrate in an atmosphere with a pressure lower than atmospheric pressure. The AD device 50 includes: an aerosol generation unit 52 that generates an aerosol containing raw material components; and a film formation unit 60 that sprays the raw material powder onto a SiC single-crystal substrate 20 to form a film containing the raw material components. The aerosol generation unit 52 includes: an aerosol generation chamber 53 that collects the raw material powder and receives a carrier gas supplied from a gas cylinder (not shown) to generate an aerosol; a raw material supply pipe 54 that supplies the generated aerosol to the film formation unit 60; and a vibration exciter 55 that vibrates the aerosol generation chamber 53 and the aerosol therein at a vibration frequency of 10–100 Hz. Examples of carrier gases include N2. Furthermore, in order to effectively control the distribution of dislocation density in the biaxially oriented SiC layer, it is preferable to control the flow rate of the carrier gas, which is preferably 2.0 to 6.5 L / min, or 4.0 to 6.5 L / min. The film-forming section 60 includes: a film-forming chamber 62 in which aerosol is sprayed onto the SiC single-crystal substrate 20; a substrate holder 64 disposed inside the film-forming chamber 62 and fixing the SiC single-crystal substrate 20; and an X-Y stage 63 that moves the substrate holder 64 in the X-axis to Y-axis direction. Additionally, the film-forming section 60 includes: a spray nozzle 66 with a slit 67 formed at its tip to spray aerosol onto the SiC single-crystal substrate 20; and a vacuum pump 68 that depressurizes the film-forming chamber 62. The spray nozzle 66 is mounted at the tip of the raw material supply pipe 54.

[0066] Regarding the Alignment and Adsorption (AD) method, it is known that there are cases where pores are generated in the film depending on the film formation conditions, or where the film becomes a pressed powder body. For example, it is easily affected by factors such as the impact velocity of the raw material powder toward the substrate, the particle size of the raw material powder, the agglomeration state of the raw material powder in the aerosol, and the spraying rate per unit time. Regarding the impact velocity of the raw material powder toward the substrate, it is affected by factors such as the differential pressure between the film formation chamber 62 and the spray nozzle 66, and the opening area of ​​the spray nozzle. Therefore, in order to obtain a dense orientation precursor layer, it is necessary to appropriately control these factors. In particular, in order to effectively control the distribution of dislocation density in the biaxially oriented SiC layer, it is preferable to control, for example, the opening area (nozzle size) of the spray nozzle.

[0067] In the thermal CVD method, commercially available film-forming apparatus or other known film-forming apparatus can be used. The feed gas is not particularly limited; silicon tetrachloride (SiCl4) gas or silane (SiH4) gas can be used as the Si supply source, and methane (CH4) gas or propane (C3H8) gas can be used as the C supply source. The film-forming temperature is preferably 1000–2200°C, more preferably 1100–2000°C, and even more preferably 1200–1900°C.

[0068] It is known that when a film is formed on a SiC single-crystal substrate 20 using thermal CVD, epitaxial growth sometimes occurs on the SiC single-crystal substrate 20 to form a SiC substrate 30. However, the orientation precursor layer 40 is in an unoriented state during its fabrication, i.e., it is amorphous or non-oriented polycrystalline. It is preferable to allow it to undergo crystal rearrangement using the SiC single crystal as a seed crystal during the heat treatment process. To form an amorphous or polycrystalline layer on a SiC single crystal using thermal CVD, it is known that the film formation temperature, the gas flow rates of the Si source and C source and their ratio, and the film formation pressure all have an impact. The film formation temperature has a significant impact; from the viewpoint of forming an amorphous or polycrystalline layer, a lower film formation temperature is preferred, preferably less than 1700°C, more preferably less than 1500°C, and even more preferably less than 1400°C. However, if the film formation temperature is too low, the film formation rate itself decreases; therefore, from the viewpoint of film formation rate, a higher film formation temperature is preferred.

[0069] When using a pre-made molded body as the orientation precursor layer 40, the raw material powder of the orientation precursor can be molded to produce it. For example, when using compression molding, the orientation precursor layer 40 is a compression molded body. The compression molded body can be produced by compression molding the raw material powder of the orientation precursor based on a known method, for example, by placing the raw material powder into a mold at a pressure of preferably 100 to 400 kgf / cm³. 2 More preferably 150–300 kgf / cm² 2 The material can be manufactured by pressing under pressure. Furthermore, the molding method is not particularly limited; besides pressing, casting, extrusion, casting, scraping, and any combination thereof can be used. For example, when using casting, it is preferable to add appropriate additives such as binders, plasticizers, dispersants, and dispersion media to the raw material powder to form a slurry, which is then extruded through a narrow, slit-shaped nozzle and molded into a sheet. The thickness of the sheet is not limited, but from an operational point of view, 5 to 500 μm is preferred. Additionally, if a thicker orientation precursor layer is required, multiple sheets can be stacked and used at the desired thickness. These sheets are then subjected to heat treatment on the SiC single-crystal substrate 20 to transform the portion near the SiC single-crystal substrate 20 into a SiC substrate 30. In this method, the sheet needs to be sintered in the heat treatment process described later. It is preferable to form the SiC substrate 30 after sintering the sheet and integrating it as a polycrystalline material with the SiC single-crystal substrate 20. Without sintering the molded body, epitaxial growth using SiC single crystals as seed crystals may not occur sufficiently. Therefore, in addition to SiC raw materials, the molded body may also contain additives such as sintering aids.

[0070] (b) Heat treatment process

[0071] like Figure 2 As shown in (b), in the heat treatment process, a stack on which the orientation precursor layer 40 is stacked or placed is heat-treated to form the SiC substrate 30. Regarding the heat treatment method, there are no particular limitations as long as epitaxial growth with the SiC single crystal substrate 20 as a seed crystal occurs; it can be carried out in known heat treatment furnaces such as tubular furnaces or hot plates. Furthermore, not only can these atmospheric pressure (non-pressurized) heat treatments be used, but also pressurized heat treatments such as hot pressing and HIP, as well as combinations of atmospheric pressure and pressurized heat treatments, can be used. The heat treatment atmosphere can be selected from vacuum, nitrogen, inactive gases, and combinations thereof. The heat treatment temperature is preferably 1700–2700°C. By increasing the temperature, the orientation precursor layer 40 can easily grow along the c-axis and a-axis orientation edges with the SiC single crystal substrate 20 as a seed crystal. Therefore, the heat treatment temperature is preferably 1700°C or higher, more preferably 1800°C or higher, even more preferably 1900°C or higher, and particularly preferably 2200°C or higher. On the other hand, if the temperature is too high, some of the SiC may disappear due to sublimation, or the SiC may undergo plastic deformation, resulting in warping or other defects. Therefore, the heat treatment temperature is preferably below 2700°C, and more preferably below 2500°C. However, the heat treatment conditions affect the concentration of rare earth elements in the biaxially oriented SiC layer and the distribution of dislocation density in the biaxially oriented SiC layer. Therefore, it is preferable to appropriately control these conditions (e.g., the heat treatment temperature). From this perspective, the heat treatment temperature is preferably 2200–2600°C, more preferably 2390–2500°C, further preferably 2400–2500°C, and particularly preferably 2400–2450°C. In addition, the holding time is preferably 2–30 hours, more preferably 4–20 hours. Furthermore, the heat treatment can be performed in multiple stages. Even in this case, the heat treatment temperature and the total holding time are preferably within the above ranges. Moreover, the heat treatment temperature and holding time are also related to the thickness of the SiC substrate 30 produced during epitaxial growth and can be adjusted appropriately.

[0072] However, when using a pre-formed molded body as the orientation precursor layer 40, it needs to be sintered in a heat treatment process, preferably high-temperature atmospheric pressure sintering, hot pressing, HIP, or a combination thereof. For example, when using hot pressing, the surface pressure is preferably 50 kgf / cm². 2 The above, more preferably 100 kgf / cm 2 The above is further preferred to be 200 kgf / cm². 2There are no specific upper limits for the above. Similarly, regarding the firing temperature, there are no particular limitations as long as sintering and epitaxial growth occur. However, firing conditions affect the concentration of rare earth elements in the biaxially oriented SiC layer and the distribution of dislocations in the biaxially oriented SiC layer; therefore, it is preferable to appropriately control these conditions (e.g., firing temperature, holding time). From this perspective, the firing temperature is preferably 1700–2700°C. Furthermore, the holding time is preferably 2–18 hours. The atmosphere during firing can be selected from vacuum, nitrogen, an inert gas atmosphere, or a mixture of nitrogen and inert gases. Also, as mentioned above, firing can be carried out in multiple stages, and the firing temperature and total holding time are preferably within the above ranges. The SiC powder constituting the raw material can be composed of at least one of α-SiC and β-SiC, preferably β-SiC. The SiC powder is preferably composed of SiC particles having a volume-based D50 particle size of 0.01–100 μm.

[0073] During the heat treatment process, the crystals within the orientation precursor layer 40 preferably grow along the c-axis and a-axis orientation edges of the crystal growth surface of the SiC single crystal substrate 20. Therefore, the orientation precursor layer 40 gradually transforms into the SiC substrate 30 from the crystal growth surface. The SiC composite substrate with the generated SiC substrate 30 becomes a substrate with reduced cracking and fissures during substrate processing.

[0074] (c) Grinding and / or polishing processes

[0075] like Figure 2 As shown in (c), in the grinding process, the orientation precursor layer 40 remaining on the SiC substrate 30 after the heat treatment process is removed by grinding, exposing the surface of the SiC substrate 30, and the exposed surface is then ground and / or polished. Thus, the SiC composite substrate 10 is obtained.

[0076] It should be noted that the present invention is not limited to any of the above embodiments. Of course, it can be implemented in various ways as long as it falls within the technical scope of the present invention. For example, in the above embodiments, only one SiC substrate 30 is provided on the SiC single crystal substrate 20, but two or more layers can also be provided. Specifically, an orientation precursor layer 40 is stacked on the SiC substrate 30 of the SiC composite substrate 10. After heat treatment, grinding and / or polishing are performed sequentially, thereby allowing a second SiC substrate 30 to be provided on the SiC substrate 30.

[0077] Example

[0078] The invention will be further illustrated by the following examples. It should be noted that the following examples do not limit the scope of the invention in any way.

[0079] Example 1

[0080] (1) Fabrication of the orientation precursor layer

[0081] A raw material powder comprising 90.8 wt% commercially available fine β-SiC powder (volume basis D50 particle size: 0.7 μm) and 9.2 wt% yttrium oxide powder (volume basis D50 particle size: 0.1 μm) was prepared. These raw material powders were ball-milled in ethanol for 24 hours using SiC balls and then dried to obtain a mixed powder. As a SiC single crystal layer, a commercially available SiC single crystal substrate (n-type 4H-SiC, approximately 150 mm (6 inches) in diameter, Si face, (0001) face, 4° offset angle, 0.35 mm thickness, non-orientation flat) was prepared. Figure 3 In the AD device 50 shown, mixed powder is sprayed onto a SiC single crystal substrate to form an AD film (orientation precursor layer).

[0082] The AD film formation conditions are as follows. First, the carrier gas is set to N2, and the flow rate is set to 4.0 L / min. Film formation is performed using a ceramic nozzle with a slit formed with a long side of 5 mm × a short side of 0.4 mm. Regarding the nozzle scanning conditions, a scanning process is repeatedly performed: moving 155 mm in a forward direction perpendicular to the long side of the slit at a scanning speed of 0.5 mm / s, moving 5 mm in the direction of the long side of the slit, moving 155 mm in a return direction perpendicular to the long side of the slit, and moving 5 mm in the direction of the long side of the slit in the opposite direction to the initial position. At the moment when moving 155 mm from the initial position in the direction of the long side of the slit, scanning in the opposite direction is performed, returning to the initial position. This cycle is counted as one cycle, and it is repeated 4000 times. The thickness of the AD film formed in this way is approximately 400 μm.

[0083] (2) Heat treatment of the orientation precursor layer

[0084] The SiC single-crystal substrate with the AD film forming the orientation precursor layer is removed from the AD device and annealed at 2400°C for 10 hours in an argon atmosphere. That is, the orientation precursor layer is heat-treated to form a heat-treated layer.

[0085] (3) Grinding

[0086] (3-1) Surface grinding

[0087] The (0001) surface of the SiC single crystal substrate with the heat treatment layer is ground to a specified thickness using a grinding device (diamond wheel with a grit size of 1000 to 6000) and set as the target thickness and surface condition.

[0088] (3-2) Backside grinding

[0089] The (000-1) surface of a SiC single crystal substrate with a heat-treated layer is ground to a specified thickness using a grinding device (diamond wheel with a grit size of 1000-6000). This thickness and surface condition are then defined as the target thickness. Thus, the SiC substrate is obtained.

[0090] (4) Evaluation related to suppressing cracking and crack initiation after processing

[0091] Using an industrial microscope (Nikon ECLIPSE LV150N), the magnification of the eyepiece was set to 10x and the magnification of the objective lens was set to 5x. The entire surface of the SiC substrate obtained in (3) above was observed in polarized mode and differential interference mode. If cracks or fissures were found, the substrate was considered to have cracks or fissures. At this time, only cases where the length of the cracks or fissures was 100 μm or more were counted as cracks or fissures. The number of SiC substrates with cracks or fissures of 100 μm or more in length among 100 SiC substrates produced under the same conditions as the SiC substrates produced as described above was determined, and the occurrence rate P of cracks and fissures was calculated. C (%). By calculating P C The yield of the substrate was evaluated. The results are shown in Table 1.

[0092] (5) Grinding

[0093] (5-1) Surface grinding

[0094] The (0001) surface of the SiC substrate obtained in (3) above is ground with diamond abrasive and then chemical mechanical polishing (CMP) is performed to achieve the target thickness and surface condition.

[0095] (5-2) Backside grinding

[0096] The (000-1) surface of the SiC substrate obtained in (3) above is ground with diamond abrasive grains to determine the target thickness and surface condition.

[0097] (6) Evaluation of biaxial orientation of heat-treated layer

[0098] Using the EBSD (Electron Back Scatter Diffraction Patterns) method, the inverse pole figure mapping of the surface (plate surface) and the cross section orthogonal to the plate surface of the heat-treated layer obtained in (3) above was measured under the conditions shown below. As a result, the tilt angle distribution is less than 0.01° in both the approximate normal direction and the approximate plate surface direction. Therefore, it is determined that the heat-treated layer is a biaxially oriented SiC layer oriented along the c-axis and a-axis.

[0099] <EBSD Measurement Conditions>

[0100] • Measurement apparatus: SEM (Hitachi High Technology Co., Ltd. SU-5000) equipped with electron backscatter diffraction (EBSD) device (Oxford Instruments Nordlys Nano)

[0101] Accelerating voltage: 15kV

[0102] • Light spot intensity: 70

[0103] • Working distance: 22.5mm

[0104] • Step size: 0.5μm

[0105] • Sample tilt angle: 70°

[0106] • Measurement procedure: Aztec (version 3.3)

[0107] (7) X-ray morphology (XRT) determination of the heat-treated layer

[0108] Using the SiC substrate fabricated using (5) above as an evaluation sample, XRT images of the evaluation sample were obtained under the conditions shown below.

[0109] <XRT Measurement Conditions>

[0110] • Measurement apparatus: X-ray topography imaging system (XRTmicron manufactured by Rigaku Co., Ltd.)

[0111] • Observation mode: Reflection

[0112] • Diffraction plane: (11-28) plane

[0113] X-ray source: Cu, Kα

[0114] • Tube voltage / tube current: 40kV / 30mA

[0115] • Detector: XTOP CCD camera

[0116] • Shooting area: Entire sample surface

[0117] First, an evaluation related to basal plane dislocations (BPDs) was performed. The entire XRT image of the obtained sample surface was divided into a grid of regions, each 4 mm long × 4 mm wide × 28 μm deep. It should be noted that "depth" refers to the X-ray penetration depth. Within each divided region, the entire length of the BPD was measured using image processing software (Rigaku Corporation), and the volume density (cm³ / cm³) of each BPD was determined. 3Furthermore, the average volume density of the aforementioned region in the XRT image is calculated, thereby determining the average volume density X (cm / cm²) of each BPD. 3 In addition, the maximum number of consecutive cells C in each of the two vertical and horizontal lines was confirmed for regions where each cell reaches 5X or higher. 5X The maximum number of consecutive grids (C) in each grid region where each grid reaches 3X or higher, located on a straight line in both the horizontal and vertical directions. 3X (Grid). At this point, regarding C 5X and C 3X Only the number of consecutive squares along a vertical straight line and a horizontal straight line is counted; the number of consecutive squares along a diagonal straight line is not counted. The results are shown in Table 1. It should be noted that in the sample of Example 1, each square was counted according to the XRT image to achieve 5X (cm / cm). 3 The above area is analyzed and displayed as a blacked-out grid, as shown in the diagram. Figure 4 .Should Figure 4 The text also shows a connection to C. 5X The corresponding part A.

[0118] An evaluation related to screw dislocations (TSDs) was also conducted. The entire XRT image of the sample was divided into a grid of 4mm x 4mm sections. Within each section, the number of TSDs was measured using image processing software (Rigaku Corporation), and the TSD number density per grid section ( / cm²) was determined. 2 Furthermore, the average number density of the above-mentioned elements in the entire region of the XRT image is calculated, thereby determining the average number density Y ( / cm²) of TSD per cell. 2 In addition, the maximum number of consecutive cells C in each region where 2Y or higher is achieved was confirmed to be on a straight line in both the horizontal and vertical directions. 2Y (Grid). At this point, regarding C 2Y The number of consecutive squares along a vertical line and a horizontal line is counted only; the number of consecutive squares along a diagonal line is not counted. The results are shown in Table 1.

[0119] An evaluation related to edge dislocations (TEDs) was also conducted. The entire XRT image of the sample was divided into a grid of 4mm x 4mm sections. Within each section, the number of TEDs was measured using image processing software (Rigaku Corporation), and the TED density per grid section ( / cm²) was determined. 2Furthermore, the average number density of the above-mentioned number is calculated across the entire region of the XRT image, thereby determining the average number density Z ( / cm) of TED per cell. 2 In addition, the maximum number of consecutive cells C in each grid cell that reaches 2Z or higher on both the horizontal and vertical lines was confirmed. 2Z (Grid). At this point, regarding C 2Z The number of consecutive squares along a vertical line and a horizontal line is counted only; the number of consecutive squares along a diagonal line is not counted. The results are shown in Table 1.

[0120] (8) Rare earth element concentration in the heat treatment layer

[0121] The substrate, prepared in the same manner as (1) and (2) above, was ground in the same way as (3-1) above, and then cut into chips approximately 5mm long and 6mm wide, which were used as evaluation samples. Dynamic secondary ion mass analysis (D-SIMS) was performed on the ground surface (0001) of the evaluation sample. The rare earth element (Y in this example) was analyzed using an IMS-7f manufactured by CAMECA, with the primary ion species O2. + The measurement was performed using an accelerating voltage of 11.0 kV. This allowed for the determination of the rare earth element (Y) concentration C. RE (atoms / cm 3 The measurements were performed. The results are shown in Table 1.

[0122] Example 2

[0123] In (1) above, the flow rate of carrier gas N2 was set to 5.5 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0124] Example 3 (Compare)

[0125] In (1) above, the flow rate of carrier gas N2 was set to 3.5 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. It was confirmed that the obtained heat-treated layer was a biaxially oriented SiC layer. The results are shown in Table 1.

[0126] Example 4

[0127] In (1) above, the flow rate of carrier gas N2 was set to 6.5 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0128] Example 5

[0129] In (1) above, the flow rate of carrier gas N2 was set to 6.0 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0130] Example 6 (Compare)

[0131] In (1) above, a raw material powder containing 80.8 wt% fine β-SiC powder (volume basis D50 particle size: 0.7 μm) and 19.2 wt% yttrium oxide powder (volume basis D50 particle size: 0.1 μm) was used. The flow rate of carrier gas N2 was set to 2.0 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0132] Example 7

[0133] In (1) above, the flow rate of carrier gas N2 was set to 4.5 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0134] Example 8

[0135] In (1) above, the flow rate of carrier gas N2 was set to 5.0 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0136] Example 9 (Compare)

[0137] In (1) above, the flow rate of carrier gas N2 was set to 3.0 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0138] Example 10 (Compare)

[0139] In (1) above, the flow rate of carrier gas N2 was set to 2.5 L / min. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0140] Example 11

[0141] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 0.5 mm was used for film formation. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0142] Example 12

[0143] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 0.6 mm was used for film deposition. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0144] Example 13 (Compare)

[0145] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 0.9 mm was used for film formation. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0146] Example 14

[0147] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 0.2 mm was used for film deposition. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0148] Example 15

[0149] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 0.3 mm was used for film formation. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0150] Example 16 (Compare)

[0151] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 1.0 mm was used for film formation. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0152] Example 17

[0153] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 0.8 mm was used for film deposition. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0154] Example 18

[0155] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 0.7 mm was used for film deposition. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0156] Example 19 (Compare)

[0157] In (1) above, a ceramic nozzle with a slit having a long side of 5 mm and a short side of 1.1 mm was used for film deposition. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0158] Example 20 (Compare)

[0159] In (1) above, a raw material powder comprising 80.8 wt% fine β-SiC powder (volume basis D50 particle size: 0.7 μm) and 19.2 wt% yttrium oxide powder (volume basis D50 particle size: 0.1 μm) was used, and a ceramic nozzle with a slit formed on the long side of 5 mm × 1.2 mm was used for film formation. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0160] Example 21

[0161] In step (2) above, annealing was performed at 2410°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0162] Example 22

[0163] In step (2) above, annealing was performed at 2420°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0164] Example 23 (Compare)

[0165] In step (2) above, annealing was performed at 2370°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0166] Example 24

[0167] In step (2) above, annealing was performed at 2430°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0168] Example 25

[0169] In step (2) above, annealing was performed at 2440°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0170] Example 26 (Compare)

[0171] In (1) above, a raw material powder containing 94.9 wt% fine β-SiC powder (volume basis D50 particle size: 0.7 μm) and 5.1 wt% yttrium oxide powder (volume basis D50 particle size: 0.1 μm) was used. In (2) above, annealing was performed at 2460 °C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0172] Example 27

[0173] In step (2) above, annealing was performed at 2450°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0174] Example 28

[0175] In step (2) above, annealing was performed at 2390°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0176] Example 29 (Compare)

[0177] In step (2) above, annealing was performed at 2470°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0178] Example 30 (Compare)

[0179] In step (2) above, annealing was performed at 2480°C for 10 hours in an argon atmosphere. Otherwise, the SiC substrate was fabricated and evaluated in the same manner as in Example 1. The obtained heat-treated layer was confirmed to be a biaxially oriented SiC layer. The results are shown in Table 1.

[0180] Table 1

[0181] Table 1

[0182]

[0183] * indicates a comparison example.

[0184] X: Average volume density of BPD per cell (cm³ / cm³) 3 )

[0185] Y: Average number density of TSDs per cell ( / cm²) 2 )

[0186] Z: Average density of TEDs per cell ( / cm²) 2 )

[0187] C 3X The maximum number of consecutive cells (cells) where each cell reaches 3X or higher.

[0188] C 5X The maximum number of consecutive cells (cells) where each cell reaches 5X or higher.

[0189] C 2Y The maximum number of consecutive cells (cells) in an area where each cell reaches 2Y or higher.

[0190] C 2Z The maximum number of consecutive cells (cells) where each cell reaches 2Z or higher.

[0191] C RE Rare earth element concentration (×10) 15 atoms / cm 3 )

[0192] Pc: Percentage of cracks and fissures (%)

[0193] Although the reason is still uncertain, it is known that the distribution of BPDs can be controlled by the film formation conditions (carrier gas flow rate, etc.) and the concentration of rare earth elements in the SiC substrate during the AD process. Specifically, it is known that in the following SiC substrate, cracking or fissures during processing can be reduced. Regarding this SiC substrate, when the entire XRT image area of ​​the biaxially oriented SiC layer is divided into a grid of 4mm x 4mm x 28μm, and the average volume density of BPDs in each grid is set as X (cm / cm³),... 3 When ), each grid reaches 5X (cm / cm) 3 The area above ) does not have more than 10 consecutive grids on either a straight line (vertical or horizontal). Specifically, it can be seen that each grid reaches 3X (cm / cm). 3 In areas where there are no more than 5 consecutive grids on a straight line in either the longitudinal or transverse direction, cracking or fissures during processing can be effectively reduced.

Claims

1. A SiC substrate having a biaxially oriented SiC layer, The SiC substrate is characterized in that... In the XRT image obtained by X-ray morphology (XRT) measurement of the biaxially oriented SiC layer, the entire XRT image area is divided into a lattice with each cell being 4 mm x 4 mm x 28 μm deep. The average volume density of basal dislocations (BPDs) in each cell is set as X (cm / cm²). 3 When ), each grid reaches 5X (cm / cm) 3 The above areas do not have more than 10 consecutive grids on either a vertical or horizontal straight line.

2. The SiC substrate according to claim 1, characterized in that, In the XRT image, each frame reaches 3X (cm / cm) 3 The above areas do not have more than 5 consecutive squares on either a vertical or horizontal straight line.

3. The SiC substrate according to claim 1 or 2, characterized in that, When the entire XRT image is divided into a grid of 4mm x 4mm sections, and the average number density of spiral dislocations (TSDs) in each section is set to Y ( / cm²),... 2 When ), each grid reaches 2Y ( / cm) 2 The above areas do not have more than 10 consecutive grids on either a vertical or horizontal straight line.

4. The SiC substrate according to claim 1 or 2, characterized in that, When the entire XRT image is divided into a grid of 4mm x 4mm sections, and the average number density of edge dislocations (TED) in each section is set to Z ( / cm²),... 2 When ), each grid reaches 2Z ( / cm) 2 The above areas do not have more than 10 consecutive grids on either a vertical or horizontal straight line.

5. The SiC substrate according to claim 1 or 2, characterized in that, X is 200–5000 cm / cm 3 .

6. The SiC substrate according to claim 1 or 2, characterized in that, The rare earth element concentration of the biaxially oriented SiC layer is 2.0 × 10⁻⁶. 14 ~5.0×10 15 atoms / cm 3 .

7. A SiC composite substrate, characterized in that, have: SiC single crystal substrate; and The SiC substrate of claim 1 or 2 is described on the SiC single crystal substrate.

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