SiC SINGLE CRYSTAL WAFER, SiC SINGLE CRYSTAL INGOT, METHOD FOR PRODUCING SiC SINGLE CRYSTAL WAFER, METHOD FOR PRODUCING SiC SINGLE CRYSTAL INGOT, SiC SINGLE CRYSTAL INGOT PRODUCTION DEVICE, AND METHOD FOR FORMING FILM FORMED BY SiC EPITAXIAL GROWTH

Abstract

A SiC single crystal ingot according to the present disclosure has a diameter of not less than 4 inches, and has an area ratio of not more than 5% with respect to a surface of a solvent inclusion region observed in an image captured of the surface.

Description

SiC single crystal wafer, SiC single crystal ingot, SiC single crystal wafer manufacturing method, SiC single crystal ingot manufacturing method, SiC single crystal ingot manufacturing apparatus, and SiC epitaxial growth film forming method

[0001] The present invention relates to a SiC single crystal wafer, a SiC single crystal ingot, a method for manufacturing a SiC single crystal wafer, a method for manufacturing a SiC single crystal ingot, an apparatus for manufacturing a SiC single crystal ingot, and a method for forming a SiC epitaxially grown film.

[0002] In the growth of SiC single crystals using the solution method, silicon containing metal is typically melted in a carbon crucible, and then a pulling shaft with a seed crystal attached is brought into contact with the melt to crystallize it. However, depending on the growth environment, the solvent may be incorporated directly into the crystal (solvent inclusions). These solvent inclusions remain in a molten state in the high-temperature environment during growth, but solidify as cooling progresses after growth is completed. This generates strong stress, which can lead to problems with the crystallinity of the grown crystal.

[0003] Patent Document 1 discloses a technique for improving solvent inclusions in SiC single crystal growth using a solution method by controlling the growth interface to be concave and by directing the solvent flow in the vicinity of the growth interface from the center outward.

[0004] Patent Document 2 discloses a manufacturing apparatus that stores a SiC solution in a crucible having a lower storage chamber and an upper storage chamber with different diameters. The diameter ratio of the lower storage chamber to the upper storage chamber is adjusted to optimize the flow rate of the upward flow. Specifically, the ratio (diameter of the lower storage chamber) / (diameter of the upper storage chamber) is adjusted to 0.25 to 0.65.

[0005] JP 2014-19614 A Patent No. 5439353

[0006] The maximum diameter of the SiC single crystal for which improvement of solvent inclusions has been confirmed using the technology of Patent Document 1 is relatively small at 44.6 mm. Patent Document 2 does not mention solvent inclusions.

[0007] An example of a problem to be solved by the present disclosure is to improve solvent inclusions in SiC single crystals with large diameters compared to the prior art.

[0008] According to the present disclosure, there is provided a SiC single crystal wafer having a diameter of 4 inches or more, in which the area ratio of solvent inclusion regions to the surface observed in an image of the surface is 5% or less.

[0009] The present disclosure also provides a SiC single crystal ingot having a diameter of 4 inches or more, in which the area ratio of solvent inclusion regions to the surface observed in an image of the surface is 5% or less.

[0010] The present disclosure also provides a method for producing a SiC single crystal ingot, comprising a growth step of contacting a SiC seed crystal with a raw material solution containing Si and C to produce a growth layer of a SiC single crystal on a surface of the SiC seed crystal, wherein the standard deviation of the total thickness of the SiC seed crystal and the growth layer in an as-grown state obtained in the growth step, measured at 2 mm intervals from the center toward the periphery, is 300 μm or less.

[0011] According to the present disclosure, there is also provided a method for growing a SiC single crystal by contacting a SiC seed crystal with a raw material solution containing Si and C to produce a growth layer of a SiC single crystal on a surface of the SiC seed crystal, wherein the growth step comprises: a crucible having a solution containing space surrounded by a bottom, a sidewall, and an opening facing the bottom, the raw material solution being contained in the solution containing space; a chamber containing the crucible; a pulling shaft to which the SiC seed crystal having a diameter of 4 inches or more is attached; and a heater for heating the raw material solution contained in the crucible, wherein the solution containing space of the crucible has a first space and a second space having different diameters in a cross section perpendicular to a height direction from the bottom toward the opening, the first space and the second space being adjacent to each other and connected in the height direction, A method for manufacturing a SiC single crystal ingot is provided, in which the growth layer is produced using a manufacturing device in which the diameter of the cross section of the first space located on the bottom side is smaller than the diameter of the cross section of the second space located on the opening side.

[0012] The present disclosure also provides a method for producing a SiC single crystal wafer, comprising the steps of: producing a SiC single crystal ingot by the method for producing a SiC single crystal ingot; and slicing a SiC single crystal wafer from the SiC single crystal ingot.

[0013] The present disclosure also provides an apparatus for manufacturing a SiC single crystal ingot, comprising: a crucible having a solution containing space surrounded by a bottom, a sidewall, and an opening facing the bottom, the solution containing space containing a raw material solution containing Si and C; a chamber accommodating the crucible; a pulling shaft to which a SiC seed crystal having a diameter of 4 inches or more is attached; and a heater for heating the raw material solution contained in the crucible, wherein the solution containing space of the crucible has a first space and a second space having different diameters in a cross section perpendicular to a height direction from the bottom to the opening, the first space and the second space being connected side by side in the height direction, and the diameter in the cross section of the first space located on the bottom side is smaller than the diameter in the cross section of the second space located on the opening side.

[0014] According to one aspect of the present disclosure, a technique is provided for improving solvent inclusions in SiC single crystals with larger diameters compared to conventional techniques.

[0015] Fig. 1 is a diagram for explaining the characteristics of a SiC single crystal ingot. Fig. 2 is a flowchart showing an example of a method for manufacturing a SiC single crystal ingot. Fig. 3 is a diagram showing an outline of an example of a crystal growth apparatus. Fig. 4 is a flowchart showing an example of a method for manufacturing a SiC single crystal wafer. Fig. 5 is a diagram showing an outline of another example of a crystal growth apparatus. Fig. 6 is a diagram for explaining the effects achieved by using the crystal growth apparatus of Fig. 5. Fig. 7 is another diagram for explaining the characteristics of a SiC single crystal ingot.

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In this disclosure, the drawings relate to one or more embodiments. In all drawings, similar components are designated by similar reference numerals, and descriptions thereof will be omitted as appropriate.

[0017] <SiC single crystal wafer> The SiC single crystal wafer of this embodiment is manufactured by a "solution process." Although the SiC single crystal wafer of this embodiment is manufactured by a solution process, it has both of the following wafer features 1 and 2.

[0018] "Wafer feature 1": Diameter is 4 inches or more, preferably 6 inches or more or 8 inches or more. "Wafer feature 2": The area ratio of the solvent inclusion region observed in the image of the surface to the surface is 5% or less, preferably 1% or less.

[0019] The solvent inclusion region is a partial region within the region of the SiC single crystal wafer in the image, where solvent inclusions are present.

[0020] Thus, despite being produced by a solution method, the SiC single crystal wafer of the present embodiment has a relatively large diameter and exhibits sufficiently reduced solvent inclusions.

[0021] It should be noted that the SiC single crystal wafer of this embodiment is manufactured by a solution method and may therefore contain solvent inclusions. For this reason, the SiC single crystal wafer of this embodiment may further have the following features.

[0022] "Wafer characteristic 3": The area ratio of the solvent inclusion region observed in the image of the surface to the surface is 0.01% or more

[0023] Furthermore, the SiC single crystal wafer of this embodiment can further have the following wafer feature 4.

[0024] "Wafer characteristic 4" Thickness is 50 μm or more and 600 μm or less

[0025] Furthermore, the SiC single crystal wafer of this embodiment can further have the following wafer feature 5.

[0026] "Wafer Feature 5" The TSD (threading screw dislocation) density or BPD (basal plane dislocation) density at the center of the surface is 100 / cm ２ Preferably 50 or less per cm ２ Below, 20 pieces / cm ２or less than 10 pieces / cm ２ below

[0027] It is noted that both the TSD (threading screw dislocation) density and the BPD (basal plane dislocation) density may satisfy the above numerical ranges.

[0028] As will be explained in detail below, the SiC single crystal wafer of this embodiment is manufactured by slicing it from a grown SiC single crystal.

[0029] The "area ratios" shown in wafer features 2 and 3 are values ​​measured as follows. The "area ratios" shown in ingot features 2 and 3, which will be described later, are also values ​​measured in the same manner.

[0030] The area ratio can be calculated using the area measurement function of a digital microscope. An image of the entire crystal surface is obtained, the brightness of the entire crystal surface is expressed as 0 to 255, and areas below 100 are regarded as solvent inclusions and color-coded. The area of ​​the color-coded areas is then divided by the area of ​​the entire crystal surface to determine the area ratio of solvent inclusions.

[0031] Furthermore, the SiC single crystal wafer of this embodiment is preferably a crystal polytype represented by 4H—SiC and 6H—SiC. The SiC single crystal wafer of this embodiment may be an on-substrate whose surface is the (0001) or (000-1) plane, or an off-substrate whose surface is cut at an inclination of 0.5 to 5 degrees relative to the (0001) or (000-1) plane.

[0032] Furthermore, the SiC single crystal wafer of this embodiment can have at least one of the following wafer features 6 and 7. In addition to at least one of wafer features 6 and 7, the SiC single crystal wafer of this embodiment may or may not have at least one of wafer features 1 to 5.

[0033] "Wafer feature 6" Cr concentration per surface area is 1 × 10 １５ atoms / cm ２ The surface Cr concentration per area is 1 x 10 １３ atoms / cm ２ It may be 1×10 or less, １１ atoms / cm２ It may be 5×10 or less. １０ atoms / cm ２ It may be 1×10 or less, １０ atoms / cm ２ On the other hand, the lower limit is not particularly limited, but may be 0 atoms / cm ２ or more, and may be 1×10 ８ atoms / cm ２ It may be more than that.

[0034] The Cr concentration per area on the surface is a value measured on the surface of the SiC single crystal wafer using a total reflection X-ray fluorescence analyzer (TXRF). In this embodiment, the Cr concentration per area was measured using a total reflection X-ray fluorescence analyzer (TXRF-3800e, manufactured by Rigaku Corporation).

[0035] Due to these characteristics, when semiconductor devices are manufactured using the SiC single crystal wafer of this embodiment, it is possible to prevent the inside of semiconductor device manufacturing equipment from being contaminated with chromium.

[0036] For example, even when epitaxial film formation is performed on the SiC single crystal wafer of this embodiment, it is possible to prevent Cr from being mixed into the epitaxial film. Therefore, by performing epitaxial film formation of SiC on the SiC single crystal wafer of this embodiment, it is possible to prevent Cr from being mixed into the epitaxial film. １５ atoms / cm ３ A SiC wafer having the following SiC epitaxially grown film can be obtained.

[0037] "Wafer characteristic 7" Cr concentration per volume is 1×10 １６ atoms / cm ３ The Cr concentration per volume is 1 x 10 １７ atoms / cm ３ It may be 5×10 or more. １７ atoms / cm ３ On the other hand, the upper limit is not particularly limited, but is not particularly limited to 1×10 ２０ atoms / cm ３ It may be 1×10 or less, １９ atoms / cm ３ It may be the following:

[0038] The Cr concentration per volume is a value measured at one point in the center of the SiC single crystal wafer by secondary ion mass spectrometry (SIMS). The Cr concentration per volume in this embodiment was measured in dynamic SIMS mode using a secondary ion mass spectrometer (IMS-7F, CAMECA).

[0039] As mentioned above, from the perspective of semiconductor device manufacturing, the less chromium there is in the SiC single crystal wafer, the better; however, there are cases in which trace amounts of chromium are incorporated into the crystal due to the solvent used in the solution method.

[0040] <SiC Single Crystal Ingot> The SiC single crystal ingot of this embodiment is produced by the “solution method.” Although the SiC single crystal ingot of this embodiment is produced by the solution method, it has both of the following ingot characteristics 1 and 2.

[0041] "Ingot feature 1": Diameter is 4 inches or more, preferably 6 inches or more or 8 inches or more. "Ingot feature 2": The area ratio of the solvent inclusion region observed in an image of the surface (growth surface) to the surface is 5% or less, preferably 1% or less.

[0042] Here, ingot feature 1 will be described. Ingot feature 1 means that any of the cross sections perpendicular to the pulling direction (long axis direction) has a diameter of 4 inches or more, preferably 6 inches or more or 8 inches or more. It is sufficient that any of the cross sections perpendicular to the pulling direction (long axis direction) satisfy the "diameter of 4 inches or more, preferably 6 inches or more or 8 inches or more" requirement, and it is not necessary for all cross sections to necessarily satisfy the "diameter of 4 inches or more, preferably 6 inches or more or 8 inches or more" requirement.

[0043] Thus, the SiC single crystal ingot of this embodiment is produced by a solution method, and yet has a relatively large diameter, and solvent inclusions are sufficiently reduced.

[0044] Since the SiC single crystal ingot of this embodiment is produced by a solution method, it may contain solvent inclusions. For this reason, the SiC single crystal ingot of this embodiment may further have the following ingot feature 3.

[0045] "Ingot characteristic 3": The area ratio of the solvent inclusion region observed in the image of the surface (growth surface) to the surface is 0.01% or more

[0046] Furthermore, the SiC single crystal ingot of this embodiment may further have the following ingot feature 4.

[0047] "Ingot characteristic 4" Thickness is 1 mm or more

[0048] Since the solution method allows continuous crystal growth and allows the ingot to be thick, the thickness of the ingot is preferably 10 mm or more, 5 cm or more, 10 cm or more, or 20 cm or more.

[0049] Although the SiC single crystal ingot of this embodiment has a sufficient thickness of 1 mm or more, as shown in ingot feature 2, the solvent inclusion region on the growth surface is sufficiently small.

[0050] Furthermore, the SiC single crystal ingot of this embodiment may further have the following ingot feature 5.

[0051] "Ingot Feature 5": The standard deviation of thickness measured at 2 mm intervals from the center to the periphery of the surface (growth surface) in the as-grown state is 300 μm or less

[0052] Ingot feature 5 will be described with reference to Fig. 1. Fig. 1 shows a stack of a seed crystal 10 and a growth layer 20. In this embodiment, the growth layer 20 is produced by bringing a raw material solution into contact with the planar surface G of the seed crystal 10 to grow a SiC single crystal.

[0053] The as-grown state is the state obtained by crystal growth, and the growth surface F has not been subjected to processing such as polishing.

[0054] As shown in FIG. 1 , the SiC single crystal ingot (growth layer 20) having the ingot feature 5 has a thickness t １ ~t ｎ The standard deviation is 300 μm or less.

[0055] When the surface G of the seed crystal 10 is flat (planar), the thickness t １ ~t ｎ The smaller the variation in thickness t １ ~t ｎ The smaller the standard deviation of ( ), the closer the growth surface F is to a flat surface.

[0056] Furthermore, the SiC single crystal ingot of this embodiment may further have the following ingot feature 6.

[0057] "Ingot Feature 6" The standard deviation of the total thickness of the seed crystal and the as-grown growth layer measured at 2 mm intervals from the center of the surface (growth surface) to the periphery is 300 μm or less.

[0058] Ingot feature 6 will be explained using Fig. 7. Fig. 7 shows a stack of a seed crystal 10 and a growth layer 20 (hereinafter, sometimes referred to as a "grown crystal"). The "total thickness of the seed crystal 10 and the growth layer 20 in the as-grown state" can be said to be the thickness of the grown crystal in the as-grown state.

[0059] As shown in FIG. 7 , the SiC single crystal ingot having the ingot feature 6 has a thickness t′ of the grown crystal measured at 2 mm intervals from the center C of the surface (growth surface) toward the periphery P. １ ~t' ｎ The standard deviation is 300 μm or less.

[0060] When the surface of the seed crystal 10 opposite to the surface in contact with the growth layer 20 is a plane (flat), the above t' １ ~t' ｎ The smaller the variation in (t' １ ~t' ｎ The smaller the standard deviation of ( ), the closer the growth surface F is to a flat surface.

[0061] Furthermore, the SiC single crystal ingot of this embodiment may further have the following ingot feature 7.

[0062] "Ingot characteristic 7" In the as-grown state, the surface (growth surface) is flat or concave.

[0063] "Flat" is defined as a standard deviation of the thickness of the grown crystal, as defined in ingot feature 6, of 50 μm or less. Note that, when the seed crystal 10 is removed, "flat" is defined as a standard deviation of the thickness of the growth layer 20, as defined in ingot feature 5, of 50 μm or less.

[0064] The "concave" does not correspond to the flat defined above, and is the thickness t' of the grown crystal at the center C of the surface (growth surface). １ is the thickness t' of the grown crystal at the outer periphery P ｎ In addition, when the seed crystal 10 is removed, the "concave" does not correspond to the flatness defined above, and the thickness t １ is the thickness t of the growth layer 20 at the periphery P ｎ is defined as being smaller than

[0065] The concave SiC single crystal ingot of this embodiment can further include at least one of the above-described ingot features 5 and 6. An SiC single crystal ingot that includes at least one of ingot features 5 and 6 and has a concave surface (growth surface) can be said to have a gently concave surface (growth surface) that is closer to a plane (flat).

[0066] The SiC single crystal ingot of this embodiment, which has ingot feature 7, satisfies the following condition: (total thickness of the seed crystal and the outer periphery of the as-grown growth layer) ≥ (total thickness of the seed crystal and the center of the as-grown growth layer).

[0067] When the seed crystal 10 is removed, the SiC single crystal ingot of this embodiment having the ingot feature 7 satisfies the following condition: (thickness of the outer periphery of the as-grown growth layer) ≥ (thickness of the center of the as-grown growth layer).

[0068] Furthermore, the SiC single crystal ingot of this embodiment may further have the following ingot feature 8.

[0069] "Ingot characteristic 8" The TSD (threading screw dislocation) density or BPD (basal plane dislocation) density at the center of the surface is 100 / cm ２ Preferably 50 or less per cm ２ Below, 20 pieces / cm ２ or less than 10 pieces / cm ２ below

[0070] It is noted that both the TSD (threading screw dislocation) density and the BPD (basal plane dislocation) density may satisfy the above numerical ranges.

[0071] The SiC single crystal ingot of this embodiment may be of a crystal polytype typified by 4H—SiC and 6H—SiC. The SiC single crystal ingot of this embodiment may have a surface that is a (0001) plane or a (000-1) plane, or may have a surface that is cut at an angle of 0.5 to 5 degrees relative to the (0001) plane or the (000-1) plane.

[0072] As will be described in detail in the following examples, the inventors have newly discovered that solvent inclusions can be reduced by growing the growth layer 20 while maintaining the growth surface F in a state closer to a plane (closer to flatness). It is difficult to maintain a perfectly flat growth surface F during the growth of the growth layer 20, and some regions may become tilted, recessed, or convex. By reducing the extent of this, solvent inclusions can be reduced. Furthermore, while it is preferable to make the growth surface F of the growth layer 20 as flat as possible, if unevenness is formed, solvent inclusions can be reduced by making it concave.

[0073] The SiC single crystal ingot of this embodiment has a thickness t' of the grown crystal measured at 2 mm intervals from the center C of the surface (growth surface F) toward the periphery P in the as-grown state. １ ~t' ｎ The standard deviation of the thickness t of the growth layer measured at 2 mm intervals from the center C of the surface (growth surface F) toward the periphery P of the SiC single crystal ingot in the as-grown state is sufficiently reduced to 300 μm or less. １ ~tｎ The standard deviation is sufficiently reduced to 300 μm or less.

[0074] 1, the SiC single crystal ingot of this embodiment may have a seed crystal 10 and a growth layer 20 in contact with the seed crystal 10. Alternatively, although not shown, the SiC single crystal ingot of this embodiment may be one obtained by removing the seed crystal 10 from a layered structure (grown crystal) of the seed crystal 10 and the growth layer 20 as shown in FIG.

[0075] Furthermore, the SiC single crystal ingot of this embodiment can have at least one of the following ingot features 9 and 10. The SiC single crystal ingot of this embodiment may or may not have at least one of ingot features 1 to 8 in addition to at least one of ingot features 9 and 10.

[0076] "Ingot feature 9" The Cr concentration per area of ​​the surface of the growth layer 20 is 1 × 10 １５ atoms / cm ２ The Cr concentration per surface area is 1 x 10 １３ atoms / cm ２ It may be 1×10 or less, １１ atoms / cm ２ It may be 5×10 or less. １０ atoms / cm ２ It may be 1×10 or less, １０ atoms / cm ２ On the other hand, the lower limit is not particularly limited, but may be 0 atoms / cm ２ or more, and may be 1×10 ８ atoms / cm ２ It may be more than that.

[0077] It can be seen that a SiC single crystal wafer cut from a SiC single crystal ingot has wafer feature 6 and therefore has ingot feature 9.

[0078] "Ingot feature 10" Cr concentration per volume of growth layer 20 is 1 × 10 １６ atoms / cm ３ The Cr concentration per volume is 1 x 10 １７ atoms / cm３ It may be 5×10 or more. １７ atoms / cm ３ On the other hand, the upper limit is not particularly limited, but is not particularly limited to 1×10 ２０ atoms / cm ３ It may be 1×10 or less, １９ atoms / cm ３ It may be the following:

[0079] It can be seen that a SiC single crystal wafer cut from a SiC single crystal ingot has wafer feature 7 and therefore has ingot feature 10.

[0080] Such a SiC single crystal wafer sliced ​​from the SiC single crystal ingot of this embodiment has wafer features 1 and 2 described above, and can further have wafer features 3 to 7 described above.

[0081] <Method for Manufacturing SiC Single Crystal Ingot> Next, a method for manufacturing a SiC single crystal ingot according to this embodiment having the above-described features will be described. As shown in Fig. 2, the method for manufacturing a SiC single crystal ingot according to this embodiment includes a growing step S10.

[0082] In the growth step S10, a growth layer of a SiC single crystal is produced by a solution method. That is, in the growth step S10, a SiC seed crystal is brought into contact with a raw material solution containing Si and C, and a growth layer of a SiC single crystal is produced on the surface of the seed crystal. The front and back surfaces of the seed crystal are flat. The front surface of the seed crystal is the surface that contacts the growth layer. The back surface of the seed crystal is the surface opposite to the surface that contacts the growth layer. The surface of the seed crystal that contacts the raw material solution (the surface that contacts the growth layer) is a carbon surface ((000-1) plane), and it is preferable that the error from the (000-1) plane is ±0.1° or less. The TTV (Total Thickness Variation) of the seed crystal is preferably 10 μm or less. The micropipe density is 0.1 pieces / cm. ２ It is preferable that the thickness is equal to or less than 1 mm. In the growth step S10, a growth layer having a thickness of 1 mm or more can be generated. Note that the TTV is a value obtained by subtracting the highest point from the lowest point from the back surface of the wafer when the back surface of the wafer serving as a seed crystal is entirely attached to a flat chuck surface, and means the thickness variation based on the back surface of the wafer.

[0083] In the growth step S10, the growth layer is grown while maintaining the growth surface (the surface in contact with the raw material solution) of the growth layer in a nearly planar state (closer to flattening). For example, in the as-grown SiC single crystal ingot obtained in the growth step S10, the growth layer is grown so that the standard deviation of the thickness of the grown crystal measured at 2 mm intervals from the center of the surface (growth surface) toward the periphery is 300 μm or less. Alternatively, in the as-grown SiC single crystal ingot obtained in the growth step S10, the growth layer is grown so that the standard deviation of the thickness of the growth layer measured at 2 mm intervals from the center of the surface (growth surface) toward the periphery is 300 μm or less. Note that the growth layer may be grown to satisfy both of these requirements. These features have been described above as ingot features 5 and 6, and therefore will not be described here.

[0084] The method for producing a SiC single crystal ingot according to this embodiment employs any one of growth methods 1 to 3 described below in the growth step S10 to achieve the growth of the characteristic growth layer described above.

[0085] "Growth Method 1" Growth method 1 uses a seed crystal with a flat surface and increases the uniformity of the temperature distribution at the interface between the raw material solution and the growth layer (or the seed crystal without the growth layer), thereby achieving "growing the growth layer while maintaining the growth surface of the growth layer in a state closer to a plane (closer to flattening)."

[0086] Specifically, in the growth step S10, the temperature of the raw material solution at the interface between the raw material solution and the seed crystal or the growth layer, where the temperature of a portion facing the center of the seed crystal or the growth layer is defined as a first temperature and the temperature of a portion facing the periphery of the seed crystal or the growth layer is defined as a second temperature, is set so that the absolute value of the value obtained by dividing the "temperature difference between the first temperature and the second temperature" by the "distance between the center and the periphery" is 0.1 K / cm or less.

[0087] The uniformity of the temperature distribution described above can be achieved by adjusting the heater placement position, number of heaters, heater shape, etc. Although it is difficult to confirm whether the temperature distribution conditions described above are satisfied during the growth of a growth layer, it is possible to confirm that the temperature distribution conditions described above are satisfied by a thermal fluid simulation described below. The inventors have confirmed that when the growth step S10 is performed with a heater configuration that satisfies the temperature distribution conditions described above by a thermal fluid simulation described below, a SiC single crystal ingot having the ingot characteristics described above can be manufactured. Note that the heater configuration (heater placement position, number of heaters, heater shape, etc.) is not limited as long as the temperature distribution conditions described above are satisfied in the thermal fluid simulation described below.

[0088] Other configurations in the growth method 1, i.e., other than the above-mentioned features, can be made using widely known techniques. An example will be described below, but the present invention is not limited to this.

[0089] Figure 3 is a diagram showing an overview of a crystal growth apparatus 1 that can be used in the growth step S10. The crystal growth apparatus 1 has a crucible 3, a pulling shaft 7, and heaters 4 (side heater 4a and bottom heater 4b in Figure 3). A SiC single crystal is produced by growing a crystal while contacting a SiC seed crystal 9 from above with a raw material solution 5 containing Si and C. Note that the figure shows a typical configuration of the heater 4. The heater 4 is configured to satisfy the above-mentioned temperature distribution conditions based on a simulation described below.

[0090] 3 has a raw material solution 5 containing Si and C inside a crucible 3, and a pulling shaft 7 is capable of rotating a seed crystal 9 attached to the tip thereof with its long axis serving as the rotation axis. The centers of the crucible 3 and the pulling shaft 7 do not necessarily have to coincide, but it is preferable that they do, and it is more preferable that the center of the crucible 3, the rotation axis of the crucible 3, the center of the pulling shaft 7, and the rotation axis of the pulling shaft 7 all coincide.

[0091] The crucible 3 is preferably a graphite crucible made of graphite, which can supply carbon to the raw material solution 5. However, crucibles other than graphite crucibles can be used as long as they can add hydrocarbon gas or a solid carbon source. To ensure a uniform composition of the raw material solution 5, it is preferable to rotate the crucible 3, and it is more preferable to use the center of the crucible 3 as the rotation axis. The rotation speed of the crucible 3 is preferably 5 to 50 rpm, more preferably 20 to 40 rpm. Setting the rotation speed within the above range enables efficient crystal growth without placing excessive strain on the apparatus. Alternatively, the crucible 3 may be rotated while periodically reversing its rotation direction between forward and reverse directions. The crucible 3 is housed in a chamber (not shown).

[0092] The raw material solution 5 is heated by a heater 4 provided around the crucible 3 to maintain a molten state. The heater 4 may be an induction heating type or a resistance heating type. The temperature inside the crucible 3 is preferably 1700 to 2100°C. The temperature inside the crucible 3 is obtained by measuring the surface of the raw material solution 5 or its vicinity, or the crucible 3, with a non-contact thermometer (manufactured by Chino, IR-CZH7 type).

[0093] The silicon source for the raw material solution can be metal silicon, silicon alloy, silicon compound, etc. The carbon source for the raw material solution can be solid carbon sources such as graphite, glassy carbon, silicon carbide, etc., or hydrocarbon gases such as methane, ethane, propane, acetylene, etc.

[0094] The source solution 5 is not particularly limited as long as it contains Si and C and is suitable for growing SiC crystals. However, it is preferable to use a solution in which C is dissolved in a Si solvent to which an additive element has been added. The silicon alloy or silicon compound used as the silicon source for the source solution can be an alloy or compound of Si and at least one additive element selected from Ti, Cr, Sc, Ni, Al, Co, Mn, Mg, Ge, As, P, N, O, Dy, Y, Nb, Nd, and Fe. In particular, a Si-Cr alloy containing 20 to 60 mol% Cr is preferably used as the solvent, due to its high carbon solubility, low vapor pressure, and chemical stability. Furthermore, when the aforementioned conductive impurities are added to the SiC single crystal, it is preferable to supply a material containing the desired element into the source solution 5.

[0095] It is preferable to create an inert atmosphere by circulating an inert gas such as a rare gas inside the crystal growth apparatus 1. The pressure is not particularly limited, but may be about atmospheric pressure (approximately 100 kPa). Furthermore, when supplying conductive impurities into the grown SiC single crystal, a gas that serves as a supply source of the conductive impurities may be added to create a mixed gas atmosphere.

[0096] The pulling shaft 7 adjusts the position of the seed crystal 9 to grow a SiC single crystal on the surface of the seed crystal 9. The diameter of the SiC single crystal may be approximately the same as that of the seed crystal 9, or the crystal may be grown so that its diameter is larger than that of the seed crystal 9. The angle by which the diameter of the grown crystal is enlarged is preferably 35 to 90 degrees, more preferably 60 to 90 degrees, and even more preferably 78 to 90 degrees. By forming a meniscus on the side surface of the seed crystal 9, the diameter of the grown crystal can be enlarged to be larger than that of the seed crystal 9. Specifically, by lowering the temperature of the solution around the seed crystal and increasing the carbon supersaturation, the growth rate toward the side surface of the seed crystal is increased, thereby enlarging the crystal diameter. A substrate holder for holding the seed crystal 9 is provided at the tip of the pulling shaft 7. The substrate holder has a diameter of 4 inches or more, preferably 6 inches or more or 8 inches or more. Such a large-diameter substrate holder can hold a large-diameter seed crystal 9. For example, the substrate holder can hold a seed crystal 9 having a diameter of 4 inches or more, preferably 6 inches or more or 8 inches or more. By using a seed crystal 9 with a large diameter, a grown crystal with a large diameter can be obtained.

[0097] In the method for producing a SiC single crystal ingot of this embodiment, when the seed crystal 9 is brought into contact with the raw material solution 5, a melt-back process may be performed in which the silicon carbide seed crystal 9 is brought into contact with the raw material solution 5 whose concentration is not saturated, and a portion of the seed crystal 9 is dissolved, and then a SiC single crystal may be grown on the seed crystal 9.

[0098] In the melt-back process, the seed crystal 9 dissolves because the carbon concentration of the raw material solution 5 is unsaturated. In the melt-back process, the surface irregularities of the seed crystal 9 disappear, and the lower surface of the seed crystal 9 becomes smooth. Note that, to prevent the entire seed crystal 9 from dissolving in the melt-back process, the immersion time of the seed crystal 9 is adjusted to a time during which only a portion of the seed crystal 9 dissolves, taking into account the dissolution rate. Thereafter, the raw material solution 5 is made supersaturated near the seed crystal 9, thereby growing a silicon carbide single crystal on the seed crystal 9.

[0099] The method for performing the melt-back step is not particularly limited. However, when the crucible 3 is made of graphite and carbon is supplied from the crucible 3 to the raw material solution 5, a method of contacting a seed crystal with the raw material solution 5 at temperature T1 during the temperature rise is considered. Since the dissolution of carbon from the crucible 3 is slow and the carbon concentration of the raw material solution is always unsaturated during the temperature rise, when the seed crystal is contacted, carbon dissolves from the crucible 3 and SiC dissolves from the seed crystal at the same time. Thereafter, by raising the temperature from temperature T1 to temperature T2 and maintaining it for a certain period of time to stabilize, carbon dissolves sufficiently from the crucible 3, and the carbon concentration in the raw material solution becomes saturated, allowing a silicon carbide single crystal to grow on the seed crystal at temperature T2. The temperature T1 during the melt-back step of the raw material solution 5 is preferably 1420°C or higher and 2100°C or lower, and more preferably 1500°C or higher and 2000°C or lower. Furthermore, the temperature T2 in the crystal growth step is preferably higher than T1, and T2-T1 may be 5°C or higher, 50°C or higher, 100°C or higher, or 200°C or lower.

[0100] Alternatively, when the crucible 3 is made of a material other than graphite, the amount of carbon source at the time of charging can be reduced, the melt-back step can be performed in a state where the raw material solution 5 is undersaturated, and then the carbon source can be supplied to the raw material solution 5 to increase the carbon concentration and perform the crystal growth step.

[0101] In the melt-back process, the lower surface of the seed crystal 9 is smoothed, resulting in good morphology in the subsequent crystal growth process.

[0102] The seed crystal 9 may be a crystal polymorph typified by 4H—SiC and 6H—SiC. The seed crystal 9 may be an on-substrate whose surface is a (000-1) plane, or an off-substrate whose surface is cut at an inclination of 0.5 to 5 degrees relative to the (000-1) plane. The angle between the surface of the seed crystal 9 and the (000-1) plane is called the off-angle. The step flow direction is the direction in which steps progress. For example, if the off-angle is formed toward the [11-20] direction, the step flow direction is the [11-20] direction. Regarding the off-angle, reference may be made to Figure 20 in WO 2014 / 034080, a patent document. The thickness of the seed crystal 9 is not particularly limited, but is typically 0.1 mm or greater.

[0103] At least the raw material solution 5 in contact with the crystal growth surface of the seed crystal 9 must be in a supersaturated state. Methods for achieving a supersaturated state of the solute C include a cooling method in which a seed crystal substrate is immersed in a SiC solution of saturated concentration and then cooled to achieve a supersaturated state, and a temperature difference method in which a seed crystal substrate is immersed in a SiC solution having a temperature gradient and SiC crystals are crystallized in the low-temperature portion.

[0104] When the temperature difference method is used, only the vicinity of the seed crystal 9 is brought into a supersaturated state by controlling the heating of the heater 4 or by cooling using the seed crystal 9, and the pulling shaft 7 brings the seed crystal 9 into contact with the raw material solution 5 and pulls it up, whereby SiC crystals are precipitated on the crystal growth surface of the seed crystal 9.

[0105] When the cooling method is used, the entire raw material solution 5 becomes supersaturated, and therefore, crystal growth can also be achieved by rotating the pulling shaft 7 while the seed crystal 9 is immersed in the raw material solution 5.

[0106] The seed crystal 9 may be fixed, but is preferably rotated in a plane parallel to the surface of the raw material solution 5. When the seed crystal 9 is rotated, the rotation speed is preferably 20 to 300 rpm, and more preferably 20 to 150 rpm. By setting the rotation speed within the above range, efficient crystal growth is possible without placing an excessive burden on the apparatus.

[0107] The seed crystal 9 is preferably rotated in a cycle of periodically repeating forward and reverse rotation, with the cycle being approximately 30 seconds to 5 minutes. By periodically switching the rotation direction, the flow of the raw material solution on the growth surface of the seed crystal during crystal growth can be controlled.

[0108] The seed crystal 9, which is an off-substrate, can be cut out so as to have a predetermined off-angle with respect to the (000-1) plane. In particular, it is preferable that the off-angle be in the range of 0.5 to 5 degrees from the

[0001] direction to the [11-20] direction. The seed crystal 9 is attached to the pulling shaft 7 so that the off-angled plane serves as the crystal growth surface and is brought into contact with the raw material solution 5.

[0109] "Growth Method 2" Growth Method 2 uses a distinctive SiC single crystal ingot manufacturing apparatus (crystal growth apparatus) to achieve "growing a growth layer while maintaining the growth surface of the growth layer in a state closer to a plane (closer to flatness)."

[0110] FIG. 5 shows a schematic diagram of an example of a crystal growth apparatus 1 used in growth method 2. The illustrated crystal growth apparatus 1 differs from the crystal growth apparatus 1 described with reference to FIG. 3 in the configuration of the crucible 3. The crystal growth apparatus 1 used in growth method 2 can have the same configuration as the crystal growth apparatus 1 described with reference to FIG. 3, except for the configuration of the crucible 3. Furthermore, widely known techniques can be adopted for the configuration other than the crystal growth apparatus 1 of growth method 2. An example of this is as described for growth method 1. The configuration of the crucible 3 will be described in detail below.

[0111] As shown in Figure 5, the crucible 3 has a solution containing space 3-4 surrounded by a bottom 3-1, a sidewall 3-2, and an opening 3-3. The opening 3-3 faces the bottom 3-1. A raw material solution 5 is contained in the solution containing space 3-4. The opening 3-3 is open and not partitioned. A pulling shaft 7 inserts a seed crystal 9 into the crucible 3 through the opening 3-3. The planar shapes of the bottom 3-1 and the opening 3-3 are, for example, circular, but may be other shapes.

[0112] The solution storage space 3-4 has a first space 3-4-1 and a second space 3-4-2. The first space 3-4-1 and the second space 3-4-2 have different diameters in a cross section perpendicular to the height direction from the bottom 3-1 to the opening 3-3 (hereinafter, sometimes referred to as the "cross section"). The first space 3-4-1 and the second space 3-4-2 are connected side by side in the height direction from the bottom 3-1 to the opening 3-3. The first space 3-4-1 is located on the bottom 3-1 side. The second space 3-4-2 is located on the opening 3-3 side. The cross-sectional shapes of the first space 3-4-1 and the second space 3-4-2 are, for example, circular, but may be other shapes. The sidewall of the first space 3-4-1 may be perpendicular to the bottom 3-1 or may be inclined. If the sidewall is inclined, the diameter of the cross section of the first space 3-4-1 may be an average value. In addition, when the second space 3-4-2 is inclined, the diameter of the cross section can be set to an average value.

[0113] In FIG. 5, the diameter of the first space 3-4-1 in the cross section is D １ The diameter of the second space 3-4-2 in the cross section is D ２ As shown in the figure, the diameter D of the first space 3-4-1 is １ is the diameter D of the second space 3-4-2 ２ is smaller than.

[0114] (The diameter D of the first space 3-4-1 in the cross section １ ) / (diameter D of the second space 3-4-2 in the cross section ２ ) may be 0.30 or more and 0.90 or less, preferably 0.65 or more and 0.90 or less, and more preferably 0.65 or more and 0.76 or less. By satisfying this condition, as shown in the following examples, the growth layer can be grown while maintaining the growth surface of the growth layer in a state closer to a plane (closer to flatness), and as a result, solvent inclusions can be reduced.

[0115] In addition, (the height H of the first space 3-4-1 in the height direction) １ ) / (height H of the raw material solution 5 contained in the second space 3-4-2 in the height direction ２) is 0.2 or more and 0.8 or less. The height direction is the direction from the bottom 3-1 toward the opening 3-3. With this configuration, it is possible to generate a "desired flow of the raw material solution 5 in the solution containing space 3-4," which will be described later with reference to FIG. 6.

[0116] The diameter D of the first space 3-4-1 in the cross section １ is the diameter d of the seed crystal 9 (SiC seed crystal) １ When a "desired flow of the raw material solution 5 in the solution containing space 3-4" is generated, which will be described later with reference to FIG. １ and diameter d １ If the above relationship is satisfied, it becomes possible to feed the raw material solution 5 substantially uniformly onto the entire surface of the seed crystal 9. As a result, it is possible to grow the growth layer while maintaining the growth surface of the growth layer in a state closer to a plane (closer to flattening).

[0117] Here, an example of the effects achieved by using the crucible 3 as described above will be described with reference to FIG.

[0118] The shapes of the crucibles 3 in Figures 6(A) to 6(E) are different from each other. Figures 6(B) to 6(E) are crucibles 3 having a first space 3-4-1 and a second space 3-4-2 with different diameters. Figure 6(A) is a crucible 3 that does not have a first space 3-4-1 and a second space 3-4-2 with different diameters. The crucibles 3 in Figures 6(B) to 6(E) are different from each other in the diameter of the first space 3-4-1. The diameter of the first space 3-4-1 decreases in the order of Figure 6(B) → Figure 6(C) → Figure 6(D) → Figure 6(E).

[0119] It is assumed that the solute is transported to the outer periphery of the solvent by rotating the crucible 3 during crystal growth. In the case of the crucible 3 shown in Figure 6(A), this phenomenon causes the degree of supersaturation on the outer periphery to be higher than that on the central portion. This state is shown by the use of black and white shading. The darker areas indicate areas with a higher degree of supersaturation. As a result of more solute being supplied to the outer periphery of the seed crystal 9, crystal growth on the outer periphery is promoted more than that on the central portion, resulting in a concave crystal.

[0120] Next, consider the case where a first space 3-4-1 with a reduced diameter is provided on the bottom side of the crucible 3, as shown in Figures 6(B) to 6(E). In this case, too, it is assumed that the solute is carried to the outer periphery of the solvent by centrifugal force during crystal growth. However, if a first space 3-4-1 with a reduced diameter is provided on the bottom side of the crucible 3, the movement of the solute toward the outer periphery can be limited to the side wall of the first space 3-4-1. In other words, the movement of the solute toward the outer periphery of the crucible 3 can be prevented.

[0121] As shown in Figures 6(B) to 6(E), the larger the diameter of the first space 3-4-1, the more solute is transported to the outer periphery, and the higher the degree of supersaturation on the outer periphery. As a result, crystal growth on the outer periphery is promoted more than that on the central side, making it easier to obtain concave crystals. As shown in Figures 6(B) to 6(E), the smaller the diameter of the first space 3-4-1, the more solute is transported to the central side, and the higher the degree of supersaturation on the central side. As a result, crystal growth on the central side is promoted more than that on the outer periphery, making it easier to obtain convex crystals. By adjusting the diameter of the first space 3-4-1 to an appropriate size, the same amount of solute is transported to the central and outer periphery, and the degree of supersaturation on the central and outer periphery sides becomes equal. As a result, crystal growth on the outer periphery and the central side becomes equal, resulting in flatter crystals.

[0122] As described above, the diameter of the first space 3-4-1 is preferably larger than the diameter of the seed crystal 9. If the diameter of the first space 3-4-1 is smaller than the diameter of the seed crystal 9, it becomes difficult to supply the solute to the outer periphery of the seed crystal 9, as shown in FIG. 6(E). As a result, more solute is supplied to the center, making it easier to obtain a convex crystal. By making the diameter of the first space 3-4-1 larger than the diameter of the seed crystal 9, such a disadvantage can be suppressed.

[0123] As explained above, when using the crystal growth apparatus 1 for growth method 2, the shape of the resulting crystal can be adjusted by adjusting the diameter of the first space 3-4-1. That is, by decreasing the diameter of the first space 3-4-1, the crystal shape can be changed from concave to flat to convex.

[0124] "Growth Method 3" Growth Method 3 combines Growth Method 1 and Growth Method 2. That is, in Growth Method 3, a crystal is grown using the crystal growth apparatus 1 described in Growth Method 2. Furthermore, in Growth Method 3, as described in Growth Method 1, when the temperature of the raw material solution at the interface between the raw material solution and the seed crystal or the growth layer, where the temperature of a portion facing the center of the seed crystal or the growth layer is defined as a first temperature and the temperature of a portion facing the periphery of the seed crystal or the growth layer is defined as a second temperature, the absolute value of the value obtained by dividing the "temperature difference between the first temperature and the second temperature" by the "distance between the center and the periphery" is 0.1 K / cm or less.

[0125] <Method for Manufacturing SiC Single Crystal Wafer> As shown in FIG. 4, the method for manufacturing a SiC single crystal wafer according to this embodiment includes a growth step S10 and a slicing step S11.

[0126] The growing step S10 is as described in the method for manufacturing a SiC single crystal ingot. The growing step S10 produces the SiC single crystal ingot of the present embodiment described above.

[0127] In the slicing step S11, SiC single crystal wafers are sliced ​​from the SiC single crystal ingot produced in the growth step S10. Through these steps, the SiC single crystal wafers of the present embodiment described above are produced. There are no particular restrictions on the method for slicing SiC single crystal wafers from the SiC single crystal ingot, and widely known techniques such as wire saw cutting and laser cutting can be employed.

[0128] <Method for forming an epitaxially grown SiC film> The method for forming an SiC film includes a step of epitaxially growing an SiC film on a characteristic SiC single crystal wafer. The SiC single crystal wafer includes at least one of the wafer characteristics 1 to 7 described above. For example, the SiC single crystal wafer has a Cr concentration per surface area of ​​1×10 １５ atoms / cm ２ Furthermore, the SiC single crystal wafer may have a diameter of 4 inches or more and a Cr concentration per volume of 1×10 １６ atoms / cm ３ In this case, the Cr concentration per volume in the SiC epitaxially grown film may be 1×10 １５ atoms / cm３ The characteristics of the SiC single crystal exemplified here are merely examples, and the SiC single crystal may have other characteristics described above as characteristics 1 to 7. The method for forming a SiC epitaxially grown film of this embodiment can be realized by utilizing widely known techniques, except for the use of such characteristic SiC single crystal.

[0129] <<Examples>> "Confirmation of the Effects of Growth Method 1" In order to confirm the effects of the above-described growth method 1, SiC single crystal ingots of Examples 1 to 3 and Comparative Example 1 were produced as follows.

[0130] Example 1 The lower end surface is a (000-1) plane, the error from the (000-1) plane is ±0.1° or less, the thickness is about 500 μm, the total thickness is 7 μm or less, and the micropipe density is 0.07 pieces / cm ２ A disk-shaped 6-inch 4H—SiC single crystal (seed crystal) shown below was attached to a graphite pulling shaft. A mixed raw material of silicon and chromium (40 mol % chromium) was prepared in a graphite crucible placed in the center of a furnace equipped with side and bottom heaters as shown in Figure 3, and heated using the heater. By holding Si—Cr as a molten liquid, a Si—Cr—C solution in which graphite was dissolved was prepared from the graphite crucible.

[0131] The atmospheric gas was helium gas, and the pressure was 1 atmosphere. When the temperature of the radiation thermometer installed below the crucible axis, measuring the temperature of the crucible bottom, reached 2050°C, the seed crystal attached to the pulling axis was brought into contact with the solution, and crystal growth on the seed crystal was allowed to proceed. During growth, the pulling axis and the crucible axis were rotated synchronously with each other at a period of 82 seconds so that the rotation directions were opposite to each other. Furthermore, to achieve both control of the crystal growth rate and control of the meniscus shape, the position of the pulling axis was adjusted during growth so that crystal growth proceeded in the thickness direction. After 100 hours, the crystal was pulled out of the solution, and the furnace was cooled. A 4H—SiC grown crystal with an average thickness of 10 mm was formed on the seed crystal, and a SiC single crystal ingot was obtained. SiC single crystal wafers were obtained by slicing this SiC single crystal ingot to the desired thickness.

[0132] A thermal fluid simulation was performed on the temperature distribution in the solution during crystal growth, and the state in which the temperature distribution reached a steady state was evaluated. As a result, "when the temperature of the raw material solution at the interface between the raw material solution and the seed crystal or the growth layer, where the temperature of a point facing the center of the seed crystal or the growth layer is defined as a first temperature and the temperature of a point facing the periphery of the seed crystal or the growth layer is defined as a second temperature, the "temperature difference between the first temperature and the second temperature" was -0.4 K, and the value obtained by dividing this by the "distance between the center and the periphery" was -0.052 K / cm.

[0133] Here, we will explain the thermal fluid simulation method, which has been confirmed to have a high correlation with actual experimental results.

[0134] The temperature distribution inside the growth furnace was analyzed using simulation software (COMSOL Multiphysics, COMSOL). The analytical model was two-dimensionally symmetric, and a thermal fluid simulation was performed taking into account heat conduction, radiation, and convection. The calculation was performed time-dependently and was terminated when the temperature reached a steady state.

[0135] The obtained ingot was sliced, and after cutting out a 20 mm square piece from the center of the growth surface, the (0001) plane side was polished, and the dislocation density was measured after KOH etching. The etching temperature was 510°C and the treatment time was 10 minutes. A digital microscope was used to observe the etch pits. The type of dislocation was determined based on the shape of the etch pits. As a result, the TSD (threading screw dislocation) density was 7 / cm. ２ , BPD (basal plane dislocation) density is 8 / cm ２ It was.

[0136] Example 2 Crystal growth was performed in the same manner as in Example 1, except that the output balance between the side heater and the bottom heater was changed. As a result, the "temperature difference between the first temperature and the second temperature" was -0.1 K, and the value obtained by dividing the "temperature difference between the center and the outer periphery" by the "distance between the center and the outer periphery" was -0.013 K / cm. The thickness of the grown crystal was 10 mm.

[0137] The dislocation density was measured using the same method as in Example 1. As a result, the TSD (threading screw dislocation) density was 6 / cm ２ , BPD (basal plane dislocation) density is 9 / cm２ It was.

[0138] Example 3 Crystal growth was performed in the same manner as in Example 2, except that the meniscus height was lower than in Example 2 and the growth time was longer. As a result, the "temperature difference between the first and second temperatures" was -0.1 K, and the value divided by the "distance between the center and the outer periphery" was -0.013 K / cm. The diameter of the grown crystal expanded to 8 inches, and the thickness of the grown crystal was 13 mm. Note that although the grown crystal was grown so that its diameter expanded, the thermal fluid simulation evaluated a state in which the temperature distribution had reached a steady state, and therefore the evaluation was performed with the same diameter as the seed crystal.

[0139] The dislocation density was measured using the same method as in Example 1. As a result, the TSD (threading screw dislocation) density was 9 / cm ２ , BPD (basal plane dislocation) density is 11 / cm ２ It was.

[0140] Comparative Example 1 Crystal growth was performed in the same manner as in Example 1, except that the output balance between the side heater and the bottom heater was changed. As a result, the "temperature difference between the first temperature and the second temperature" was 1.1 K, and the value obtained by dividing it by the "distance between the center and the outer periphery" was 0.14 K / cm.

[0141] <Comparative Results> Details will be described later, but Table 1 shows the evaluation results for Examples 1 to 3 and Comparative Example 1. The seed crystals used were all the same, 6 inches. The diameter of the grown crystals was 6 inches or more in all of Examples 1 to 3 and Comparative Example 1, and the diameter of the grown crystal in Example 3 reached 8 inches.

[0142]

[0143] "ΔT and ΔT per unit length" ΔT and ΔT per unit length in Table 1 are the results of comparing the differences in heating conditions in Examples 1 to 3 and Comparative Example 1.

[0144] ΔT is the temperature difference between the first temperature and the second temperature calculated in the above-mentioned simulation. The first temperature is the temperature of the raw material solution at the interface between the raw material solution and the seed crystal or the growth layer, and is the temperature of a location facing the center of the seed crystal or the growth layer. The second temperature is the temperature of the raw material solution at the interface between the raw material solution and the seed crystal or the growth layer, and is the temperature of a location facing the outer periphery of the seed crystal or the growth layer. In Examples 1 to 3, the absolute values ​​of ΔT are 0.4 K or less, which is smaller than that of Comparative Example 1.

[0145] ΔT per unit length is a value obtained by dividing "ΔT" by "the distance between the center and the outer periphery." In Examples 1 to 3, the absolute values ​​of ΔT per unit length are 0.1 K / cm or less, which is smaller than that of Comparative Example 1.

[0146] "Interface Shape, Standard Deviation of Growth Thickness, and Standard Deviation of Grown Crystal Thickness" The interface shape is the shape of the surface (growth surface) of the growth layer at the interface between the growth layer and the raw material solution. Specifically, the growth surface of the as-grown growth layer (SiC single crystal ingot) was evaluated.

[0147] The standard deviation of the growth thickness is the "standard deviation of the growth layer thickness" measured at 2 mm intervals from the center to the periphery of the surface of the as-grown growth layer.

[0148] The standard deviation of the grown crystal thickness is the "standard deviation of the grown crystal thickness" measured at 2 mm intervals from the center to the periphery of the surface of the grown crystal (a laminate of a seed crystal and a growth layer) in the as-grown state.

[0149] In Examples 1 to 3, in which the "absolute value of ΔT" and the "absolute value of ΔT per unit length" were made sufficiently small to enhance the uniformity of the temperature distribution at the interface between the raw material solution and the growth layer (or the seed crystal in the absence of a growth layer), the interface shape was flat. In Examples 1 to 3, the standard deviations of the growth thickness and the grown crystal thickness were small, at 200 μm or less.

[0150] On the other hand, in Comparative Example 1, in which the "absolute value of ΔT" and the "absolute value of ΔT per unit length" were relatively large and the uniformity of the temperature distribution was not improved, the interface shape was concave. In Comparative Example 1, the standard deviation of the growth thickness and the standard deviation of the grown crystal thickness were large, at 300 μm or more.

[0151] "Regarding the area ratio of solvent inclusions and their determination" The area ratio of solvent inclusions is the area ratio of the solvent inclusion region to the growth surface observed in an image taken of the surface of the growth layer of an as-grown SiC single crystal ingot.

[0152] To calculate the area ratio, a digital microscope (Keyence Corporation, VHX-8000) and its accompanying software were used with an area measurement function. Using coaxial illumination and a magnification of 20x, multiple images were overlaid with some overlapping to obtain an image of the entire crystal surface. The brightness of the entire crystal surface was expressed as 0 to 255, and areas below 100 were considered to be solvent inclusions and were color-coded. The noise in the color-coded areas was removed using a 3 x 3 median filter, after which the area was measured. The area ratio of solvent inclusions was calculated by dividing the obtained area by the area of ​​the entire crystal surface.

[0153] In Examples 1 to 3, in which the temperature distribution at the interface between the raw material solution and the growth layer (or the seed crystal without the growth layer) was made more uniform and the growth layer was grown while maintaining the growth surface of the growth layer in a more planar state (more flat), the area ratio was sufficiently small, at 5% or less, preferably 1% or less, i.e., the solvent inclusions were sufficiently reduced.

[0154] On the other hand, in Comparative Example 1, in which the growth layer was not grown while maintaining the growth surface of the growth layer in a more planar state (a more flat state), the area ratio was as large as more than 5%, meaning that the solvent inclusions were not reduced.

[0155] From the above, it can be seen that growing a growth layer while maintaining a growth surface that is closer to a plane (closer to flattening) is effective in reducing solvent inclusions.

[0156] "TSD (Threading Screw Dislocation) Density and BPD (Basal Plane Dislocation) Density" In Examples 1 to 3, in which the growth layer was grown while increasing the uniformity of the temperature distribution at the interface between the raw material solution and the growth layer (or the seed crystal without the growth layer) and maintaining the growth surface of the growth layer in a state closer to a plane (closer to flattening), the TSD (Threading Screw Dislocation) density and BPD (Basal Plane Dislocation) density in the central part of the growth surface were very small. In other words, the dislocation defect density was sufficiently reduced.

[0157] "Confirmation of Effects of Growth Methods 2 and 3" In order to confirm the effects of the above-described growth methods 2 and 3, SiC single crystal ingots of Examples 4 to 7 were produced as follows.

[0158] Example 4 A SiC single crystal ingot was produced using a crystal growth apparatus 1 as shown in Figure 5, which satisfied the following conditions. A crystal was grown in the same manner as in Example 1, except that the crystal growth apparatus was different. The diameter D of the first space 3-4-1 in the cross section was １ Diameter D of the second space 3-4-2 in the above cross section is 200 mm ２ Diameter D is 250 mm １ / Diameter D ２ 0.8 Height H of the first space 3-4-1 in the height direction １ The height H of the raw material solution 5 contained in the second space 3-4-2 in the height direction is 25 mm. ２ is 20 mm

[0159] Example 5 A SiC single crystal ingot was produced in the same manner as in Example 4, except that a crystal growth apparatus 1 as shown in Figure 5 was used, which satisfied the following conditions: The diameter D of the first space 3-4-1 in the cross section １ Diameter D of the second space 3-4-2 in the above cross section is 180 mm ２ Diameter D is 250 mm １ / Diameter D ２ 0.72 Height H of the first space 3-4-1 in the height direction １ The height H of the raw material solution 5 contained in the second space 3-4-2 in the height direction is 25 mm. ２ is 20 mm

[0160] Example 6 A SiC single crystal ingot was produced in the same manner as in Example 4, except that a crystal growth apparatus 1 as shown in Figure 5 was used, which satisfied the following conditions: The diameter D of the first space 3-4-1 in the cross section １ Diameter D of the second space 3-4-2 in the cross section is 150 mm ２ Diameter D is 250 mm １ / Diameter D ２ 0.6 Height H of the first space 3-4-1 in the height direction １ The height H of the raw material solution 5 contained in the second space 3-4-2 in the height direction is 25 mm. ２ is 20 mm

[0161] Example 7 A SiC single crystal ingot was produced in the same manner as in Example 4, except that a crystal growth apparatus 1 as shown in Figure 5 was used, which satisfied the following conditions: The diameter D of the first space 3-4-1 in the cross section １ Diameter D of the second space 3-4-2 in the cross section is 120 mm ２ Diameter D is 250 mm １ / Diameter D ２ 0.4 Height H of the first space 3-4-1 in the height direction １ The height H of the raw material solution 5 contained in the second space 3-4-2 in the height direction is 25 mm. ２ is 20 mm

[0162] In Examples 4 to 7, the diameter D of the first space 3-4-1 in the cross section is １ , and diameter D １ / Diameter D ２ are different from each other, and other conditions are the same.

[0163] The evaluation results of Examples 4 to 7 are shown in Table 2.

[0164]

[0165] The "diameter of the lower crucible" in the table is the diameter D of the first space 3-4-1 in the cross section. １ The "lower diameter / upper diameter" in the table is the diameter D １ / Diameter D ２ is.

[0166] "Interface Shape, Standard Deviation of Growth Thickness, and Standard Deviation of Grown Crystal Thickness" The interface shape is the shape of the surface (growth surface) of the growth layer at the interface between the growth layer and the raw material solution. Specifically, the growth surface of the as-grown growth layer (SiC single crystal ingot) was evaluated.

[0167] "Gentle concave" refers to a state in which a concave formed on the entire surface of the growth layer is observed. In a gentle concave, no locally occurring concave is observed on a portion of the surface of the growth layer. "Flat" refers to a state in which the standard deviation of the grown crystal thickness is 50 μm or less. "Gentle convex" refers to a state in which a convex formed on the entire surface of the growth layer is observed. In other words, in a gentle convex, no locally occurring convex is observed on a portion of the surface of the growth layer. "Locally centrally convex" refers to a state in which a locally occurring convex is observed on a portion of the surface of the growth layer.

[0168] The standard deviation of the growth thickness is the "standard deviation of the growth layer thickness" measured at 2 mm intervals from the center to the periphery of the surface of the as-grown growth layer.

[0169] The standard deviation of the grown crystal thickness is the "standard deviation of the grown crystal thickness" measured at 2 mm intervals from the center to the periphery of the surface of the grown crystal (a laminate of a seed crystal and a growth layer) in the as-grown state.

[0170] "Regarding the area ratio of solvent inclusions" The area ratio of solvent inclusions is the area ratio of the solvent inclusion region to the growth surface, as observed in an image of the surface of the growth layer of an as-grown SiC single crystal ingot. It was calculated using the same method as in Examples 1 to 3 and Comparative Example 1.

[0171] "Discussion" In Examples 4 to 7, in which SiC single crystal ingots were produced using the characteristic crystal growth apparatus 1 shown in Figure 5, the standard deviation of the growth thickness and the standard deviation of the grown crystal thickness were both 300 µm or less, which was sufficiently smaller than that of Comparative Example 1. Furthermore, in all of Examples 4 to 7, in which the growth layer was grown while maintaining the growth surface in a state closer to a plane (closer to flatness), the area ratio of solvent inclusions was 5% or less, which was sufficiently smaller than that of Comparative Example 1.

[0172] Also, the diameter D １ / Diameter D ２ In Examples 4 and 5, in which the value was adjusted to 0.65 or more and 0.90 or less, the standard deviation of the growth thickness and the standard deviation of the grown crystal thickness were both 200 μm or less, which was sufficiently smaller than those in Examples 6 and 7, which did not satisfy this condition. That is, in Examples 4 and 5, the growth layer was grown while maintaining the growth surface in a state closer to a plane (closer to flatness) than in Examples 6 and 7. Furthermore, in both of Examples 4 and 5, the area ratio of solvent inclusions was 1% or less, which was sufficiently smaller than those in Examples 6 and 7.

[0173] Also, the diameter D １ / Diameter D ２ In Example 5, in which the value of ρ was adjusted to 0.65 or more and 0.76 or less, the standard deviation of the growth thickness and the standard deviation of the grown crystal thickness were both 100 μm or less, specifically 50 μm or less, more specifically 20 μm or less, which were sufficiently smaller than those in Examples 4, 6, and 7, which did not satisfy this condition. That is, in Example 5, the growth layer was grown while maintaining the growth surface in a state closer to a plane (closer to flatness) than those in Examples 2, 6, and 7. Furthermore, in Example 5, the area ratio of solvent inclusions was 0.5% or less, specifically 0.25% or less, more specifically 0.15% or less, which was sufficiently smaller than those in Examples 4, 6, and 7.

[0174] Furthermore, from Table 2, the interface shapes of Examples 4 to 7 have diameters D １ / Diameter D ２ It can be seen that the diameter changes in a certain order with respect to the change of １ / Diameter D ２By adjusting the diameter D to 0.65 or more and 0.76 or less, the interface shape can be made flat. １ / Diameter D ２ By making the diameter D larger than 0.76, the interface shape can be made concave. １ / Diameter D ２ The interface shape can be made convex by making the value of ρ smaller than 0.65. The reason for this is believed to be due to the phenomenon explained with reference to FIG.

[0175] It is noted that a comparison between "Example 5" and "Examples 4, 6, and 7" shows that solvent inclusions can be further reduced by flattening the interface shape. Also, a comparison between "Example 4" and "Examples 6 and 7" shows that solvent inclusions can be further reduced by making the interface shape concave than by making the interface shape convex.

[0176] The ΔT and ΔT per unit length of Example 5 were calculated using the same methods as in Examples 1 to 3 and Comparative Example 1. ΔT was 0.7, and ΔT per unit length was 0.092 K / cm. That is, Example 5 corresponds to the above-mentioned growth method 3. This result shows that solvent inclusions can also be reduced in growth method 3, which is a combination of growth methods 1 and 2.

[0177] Example 8 A SiC single crystal ingot was produced in the same manner as in Example 1, except that the seed crystal was 6 inches and the seed crystal attached to the pulling shaft was brought into contact with the solution when the temperature on the radiation thermometer reached 2070°C. A grown crystal of 4H—SiC with an average thickness of 2 mm was formed on the seed crystal, and a SiC single crystal ingot was obtained.

[0178] A thermal fluid simulation was performed on the temperature distribution in the solution during crystal growth, and the state in which the temperature distribution reached a steady state was evaluated. When the "temperature of the raw material solution at the interface between the raw material solution and the seed crystal or the growth layer, the temperature of a portion facing the center of the seed crystal or the growth layer, was defined as a first temperature" and the "temperature of a portion facing the periphery of the seed crystal or the growth layer, the temperature difference between the first temperature and the second temperature" was −0.05 K, and the value obtained by dividing this by the "distance between the center and the periphery" was −0.007 K / cm.

[0179] The solvent inclusion ratio was determined in the same manner as in Example 1. As a result, no inclusions were observed within the wafer surface, resulting in a ratio of 0%.

[0180] The dislocation density was measured using the same method as in Example 1. As a result, the TSD (threading screw dislocation) density was 5 / cm ２ , BPD (basal plane dislocation) density is 5 / cm ２ It was.

[0181] A wafer with a thickness of 500 μm was cut out from the growth layer, and the surface of the wafer was analyzed for Cr concentration using a total reflection X-ray fluorescence analyzer (TXRF, Rigaku TXRF-3800e). １０ atoms / cm ２ This value met the acceptance criteria for the equipment that performs epitaxial film formation on the wafer. Therefore, if epitaxial film formation of SiC is performed on this wafer, the Cr concentration per volume will be 1×10 １５ atoms / cm ３ An epitaxially grown SiC film can be obtained as follows.

[0182] A wafer with a thickness of 500 μm was cut out from the growth layer, and one point at the center of the wafer was measured by secondary ion mass spectrometry (SIMS, CAMECA IMS-7F, measurement conditions: primary ion species Cs+, primary ion energy 15.0 keV). As a result, 1×10 １７ atoms / cm ３ of Cr was detected.

[0183] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0184] A part or all of the above-described embodiments can be described as, but not limited to, the following supplementary notes.

[0185] 1. A SiC single crystal ingot having a diameter of 4 inches or more, wherein the area ratio of solvent inclusion regions to the surface observed in an image of the surface is 5% or less. 2. A SiC single crystal ingot according to 1, wherein the area ratio is 0.01% or more and 1% or less. 3. A SiC single crystal ingot according to 1 or 2, wherein the diameter is 6 inches or more. 4. A SiC single crystal ingot according to any one of 1 to 3, wherein the thickness is 1 mm or more. 5. A SiC single crystal ingot according to any one of 1 to 4, wherein the standard deviation of thickness measured at 2 mm intervals from the center of the surface toward the periphery in an as-grown state is 300 μm or less. 6. A SiC single crystal ingot according to any one of 1 to 5, wherein the surface is flat or concave in an as-grown state. 7. 7. An SiC single crystal ingot according to any one of 1 to 6, comprising a seed crystal and a growth layer in contact with the seed crystal, wherein the surface of the seed crystal opposite to the surface in contact with the growth layer is flat, and wherein the standard deviation of the total thickness of the seed crystal and the growth layer in an as-grown state, measured at 2 mm intervals from the center toward the periphery, is 300 μm or less. 8. An SiC single crystal ingot according to 7, wherein the surface of the growth layer in an as-grown state is flat or concave. 9. An SiC single crystal ingot according to 8, wherein (total thickness of the seed crystal and the outer periphery of the growth layer in an as-grown state)≧(total thickness of the seed crystal and the central part of the growth layer in an as-grown state) is satisfied. 10. An SiC single crystal ingot according to 8, wherein the TSD (threading screw dislocation) density or BPD (basal plane dislocation) density in the central part of the surface is 100 / cm ２ 10-1. The SiC single crystal ingot according to any one of 1 to 6, wherein the Cr concentration per surface area is 1×10 １５ atoms / cm ２ 10-2. The SiC single crystal ingot according to any one of 1 to 10, wherein the Cr concentration per volume is 1×10 １６ atoms / cm ３ 10-3. The SiC single crystal ingot according to 10-1, wherein the Cr concentration per surface area is 1×10 １５ atoms / cm ２ 10-4. A SiC single crystal ingot having a Cr concentration of 1×10 or less per volume.１６ atoms / cm ３ 10-3. 11. A SiC single crystal wafer having a diameter of 4 inches or more, wherein the area ratio of solvent inclusion regions to the surface observed in an image of the surface is 5% or less. 12. A SiC single crystal wafer according to 11, wherein the area ratio is 0.01% or more and 1% or less. 13. A SiC single crystal wafer according to 11 or 12, having a diameter of 6 inches or more. 14. A SiC single crystal wafer having a TSD (threading screw dislocation) density or BPD (basal plane dislocation) density in the central part of the surface of 100 / cm ２ 14-1. A SiC single crystal wafer according to any one of 11 to 13, wherein the Cr concentration per surface area is 1×10 １５ atoms / cm ２ 14. The SiC single crystal wafer according to any one of 11 to 14, wherein the Cr concentration per volume is 1×10 １６ atoms / cm ３ 14-3. A SiC single crystal wafer having a surface area of ​​1×10 １５ atoms / cm ２ SiC single crystal wafers having a Cr concentration of 1×10 or less per volume. １６ atoms / cm ３The SiC single crystal wafer according to 14-3 above. 15. A method for producing a SiC single crystal ingot, comprising a growth step of contacting a SiC seed crystal with a raw material solution containing Si and C to produce a growth layer of SiC single crystal on the surface of the SiC seed crystal, wherein the standard deviation of the total thickness of the SiC seed crystal and the growth layer in an as-grown state obtained in the growth step, measured at 2 mm intervals from the center toward the periphery, is 300 μm or less. 16. A method for producing a SiC single crystal ingot according to 15, wherein the growth step produces the growth layer having a thickness of 1 mm or more. 17. 17. The method for producing a SiC single crystal ingot according to 15 or 16, wherein, when a first temperature is a temperature of the raw material solution at an interface between the raw material solution and the SiC seed crystal or the growth layer, and a second temperature is a temperature of the SiC seed crystal or a location facing the periphery of the growth layer, in the growth step, the absolute value of a value obtained by dividing the temperature difference between the first temperature and the second temperature by the distance between the center and the periphery is 0.1 K / cm or less. 18. The method for producing a SiC single crystal ingot according to any of 15 to 17, wherein the surface of the seed crystal is flat. 19. a growth step of contacting a SiC seed crystal with a raw material solution containing Si and C to produce a growth layer of a SiC single crystal on a surface of the SiC seed crystal, wherein the growth step comprises: a crucible having a solution containing space surrounded by a bottom, a sidewall, and an opening facing the bottom, the raw material solution being contained in the solution containing space; a chamber containing the crucible; a pulling shaft to which the SiC seed crystal having a diameter of 4 inches or more is attached; and a heater for heating the raw material solution contained in the crucible, wherein the solution containing space of the crucible has a first space and a second space having different diameters in a cross section perpendicular to a height direction from the bottom to the opening, the first space and the second space being adjacent to each other and connected in the height direction, A method for manufacturing a SiC single crystal ingot, which produces the growth layer using a manufacturing device in which the diameter of the cross section of the first space located on the bottom side is smaller than the diameter of the cross section of the second space located on the opening side.20. The method for producing a SiC single crystal ingot according to item 19, wherein (diameter of the first space in the cross section) / (diameter of the second space in the cross section) is 0.65 or more and 0.90 or less. 21. The method for producing a SiC single crystal ingot according to item 19 or 20, wherein (diameter of the first space in the cross section) / (diameter of the second space in the cross section) is 0.65 or more and 0.76 or less. 22. The method for producing a SiC single crystal ingot according to any of items 19 to 21, wherein the diameter of the first space in the cross section is larger than the diameter of the SiC seed crystal. 23. The method for producing a SiC single crystal ingot according to any of items 19 to 22, wherein the crucible is rotatable. 24. The method for producing a SiC single crystal ingot according to any of items 19 to 23, wherein (height of the first space in the height direction) / (height of the second space in the height direction) is 0.2 or more and 0.8 or less. 25. 26. A method for producing a SiC single crystal ingot according to any one of 19 to 24, wherein the diameter of the SiC seed crystal is 6 inches or more. 26. A method for producing a SiC single crystal ingot according to any one of 19 to 25, wherein the standard deviation of the total thickness of the SiC seed crystal and the growth layer in an as-grown state obtained in the growth step, measured at 2 mm intervals from the center toward the periphery, is 300 μm or less. 27. A method for producing a SiC single crystal ingot according to any one of 19 to 26, wherein the growth step produces the growth layer having a thickness of 1 mm or more. 28. 28. The method for producing a SiC single crystal ingot according to any one of 19 to 27, wherein, regarding the temperature of the raw material solution at the interface between the raw material solution and the SiC seed crystal or the growth layer, when a temperature of a portion facing the center of the SiC seed crystal or the growth layer is a first temperature and a temperature of a portion facing the periphery of the SiC seed crystal or the growth layer is a second temperature, in the growth step, the absolute value of a temperature difference between the first temperature and the second temperature divided by the distance between the center and the periphery is 0.1 K / cm or less. 29. The method for producing a SiC single crystal ingot according to any one of 19 to 28, wherein the surface of the SiC seed crystal is flat.30. A method for producing a SiC single crystal wafer, comprising: producing a SiC single crystal ingot by the method for producing a SiC single crystal ingot according to any one of 15 to 29; and slicing a SiC single crystal wafer from the SiC single crystal ingot. 31. An apparatus for manufacturing a SiC single crystal ingot, comprising: a crucible having a solution containing space surrounded by a bottom, a sidewall, and an opening facing the bottom, the solution containing space containing a raw material solution containing Si and C; a chamber accommodating the crucible; a pulling shaft to which a SiC seed crystal having a diameter of 4 inches or more is attached; and a heater for heating the raw material solution contained in the crucible, wherein the solution containing space of the crucible has a first space and a second space having different diameters in a cross section perpendicular to a height direction from the bottom to the opening, the first space and the second space being connected side by side in the height direction, and the diameter in the cross section of the first space located on the bottom side being smaller than the diameter in the cross section of the second space located on the opening side. 33. The apparatus for producing a SiC single crystal ingot according to 31, wherein (diameter of the first space in the cross section) / (diameter of the second space in the cross section) is 0.65 or more and 0.90 or less. 34. The apparatus for producing a SiC single crystal ingot according to any of 31 to 33, wherein the diameter of the first space in the cross section is larger than the diameter of the SiC seed crystal. 35. The apparatus for producing a SiC single crystal ingot according to any of 31 to 34, wherein the crucible is rotatable. 36. The apparatus for producing a SiC single crystal ingot according to any of 31 to 35, wherein (height of the first space in the height direction) / (height of the raw material solution contained in the second space in the height direction) is 0.2 or more and 0.8 or less. 37. 37. The SiC single crystal ingot manufacturing apparatus according to any one of 31 to 36, wherein the diameter of the SiC seed crystal is 6 inches or more. 38. The Cr concentration per surface area is 1×10 １５ atoms / cm ２39. A method for forming a SiC epitaxially grown film, comprising the step of epitaxially growing a SiC film on a SiC single crystal wafer having a Cr concentration per volume of 1×10 １５ atoms / cm ３ 40. The method for forming a SiC epitaxially grown film according to 38, wherein the SiC single crystal wafer has a diameter of 4 inches or more and a Cr concentration per volume of 1×10 １６ atoms / cm ３ 40. The method for forming a SiC epitaxially grown film according to 38 or 39.

[0186] This application claims priority based on Japanese Patent Application No. 2024-088677, filed May 31, 2024, and Japanese Patent Application No. 2025-008021, filed January 20, 2025, the disclosures of which are incorporated herein in their entireties.

[0187] 1 Crystal growth apparatus 3 Crucible 3-1 3-2 3-3 3-4 3-4-1 3-4-2 4 Heater 5 Raw material solution 6 Radiation thermometer 7 Pulling shaft 9 Seed crystal 10 Seed crystal 20 Growth layer

Claims

1. A SiC single crystal ingot having a diameter of 4 inches or more, in which the area ratio of solvent inclusion regions to the surface as observed in an image of the surface is 5% or less.

2. The SiC single crystal ingot according to claim 1, wherein the area ratio is 0.01% or more and 1% or less.

3. The SiC single crystal ingot according to claim 1 or 2, having a diameter of 6 inches or more.

4. The SiC single crystal ingot according to any one of claims 1 to 3, having a thickness of 1 mm or more.

5. A SiC single crystal ingot according to any one of claims 1 to 4, wherein the standard deviation of thickness measured at 2 mm intervals from the center of the surface toward the periphery in an as-grown state is 300 µm or less.

6. A SiC single crystal ingot according to any one of claims 1 to 5, wherein the surface in the as-grown state is flat or concave.

7. A SiC single crystal ingot according to any one of claims 1 to 6, comprising a seed crystal and a growth layer in contact with the seed crystal, wherein the surface of the seed crystal opposite to the surface in contact with the growth layer is flat, and the standard deviation of the combined thickness of the seed crystal and the growth layer in an as-grown state measured at 2 mm intervals from the center toward the periphery is 300 μm or less.

8. The SiC single crystal ingot according to claim 7, wherein the surface of the growth layer in the as-grown state is flat or concave.

9. The SiC single crystal ingot according to claim 8, wherein the total thickness of the seed crystal and the outer periphery of the growth layer in an as-grown state is greater than or equal to the total thickness of the seed crystal and the central portion of the growth layer in an as-grown state.

10. The TSD (threading screw dislocation) density or BPD (basal plane dislocation) density at the center of the surface is 100 / cm ２ 10. The SiC single crystal ingot according to claim 1, wherein:

11. Cr concentration per surface area is 1 x 10 １５ atoms / cm ２ 11. The SiC single crystal ingot according to claim 1, wherein:

12. Cr concentration per volume is 1 x 10 １６ atoms / cm ３ The SiC single crystal ingot according to claim 11.

13. The Cr concentration per surface area is 1 x 10 １５ atoms / cm ２ The following SiC single crystal ingot:

14. Cr concentration per volume is 1 x 10 １６ atoms / cm ３ The SiC single crystal ingot according to claim 13.

15. A SiC single crystal wafer having a diameter of 4 inches or more, wherein the area ratio of solvent inclusion regions to the surface as observed in an image of the surface is 5% or less.

16. The SiC single crystal wafer according to claim 15, wherein said area ratio is not less than 0.01% and not more than 1%.

17. The SiC single crystal wafer according to claim 15 or 16, having a diameter of 6 inches or more.

18. The TSD (threading screw dislocation) density or BPD (basal plane dislocation) density at the center of the surface is 100 / cm ２ 18. The SiC single crystal wafer according to any one of claims 15 to 17, wherein:

19. The Cr concentration per surface area is 1 x 10 １５ atoms / cm ２ 19. The SiC single crystal wafer according to any one of claims 15 to 18, wherein:

20. Cr concentration per volume is 1 x 10 １６ atoms / cm ３ The SiC single crystal wafer according to claim 19.

21. The Cr concentration per surface area is 1 x 10 １５ atoms / cm ２ The following SiC single crystal wafer:

22. Cr concentration per volume is 1 x 10 １６ atoms / cm ３ The SiC single crystal wafer according to claim 21.

23. A method for producing a SiC single crystal ingot, comprising a growth step of contacting a SiC seed crystal with a raw material solution containing Si and C to form a SiC single crystal growth layer on the surface of the SiC seed crystal, wherein the standard deviation of the total thickness of the SiC seed crystal and the as-grown growth layer obtained in the growth step, measured at 2 mm intervals from the center to the periphery, is 300 μm or less.

24. The method for producing a SiC single crystal ingot according to claim 23, wherein the growth step produces a growth layer having a thickness of 1 mm or more.

25. A method for producing a SiC single crystal ingot as described in claim 23 or 24, wherein, when the temperature of the raw material solution at the interface between the raw material solution and the SiC seed crystal or the growth layer is defined as a first temperature at a point facing the center of the SiC seed crystal or the growth layer and a second temperature at a point facing the periphery of the SiC seed crystal or the growth layer, in the growth process, the absolute value of the value obtained by dividing the temperature difference between the first temperature and the second temperature by the distance between the center and the periphery is 0.1 K / cm or less.

26. A method for producing a SiC single crystal ingot according to any one of claims 23 to 25, wherein the surface of the SiC seed crystal is flat.

27. A method for growing a SiC single crystal comprising: a growth step of contacting a SiC seed crystal with a raw material solution containing Si and C to produce a growth layer of a SiC single crystal on a surface of the SiC seed crystal; wherein the growth step comprises: a crucible having a solution containing space surrounded by a bottom, a sidewall, and an opening facing the bottom, the raw material solution being contained in the solution containing space; a chamber containing the crucible; a pulling shaft to which the SiC seed crystal having a diameter of 4 inches or more is attached; and a heater for heating the raw material solution contained in the crucible; wherein the solution containing space of the crucible has a first space and a second space having different diameters in a cross section perpendicular to the height direction from the bottom to the opening, the first space and the second space being connected side by side in the height direction; A method for manufacturing a SiC single crystal ingot, which produces the growth layer using a manufacturing device in which the diameter of the cross section of the first space located on the bottom side is smaller than the diameter of the cross section of the second space located on the opening side.

28. A method for producing a SiC single crystal ingot as described in claim 27, wherein (diameter of the first space at the cross section) / (diameter of the second space at the cross section) is 0.65 or more and 0.90 or less.

29. A method for producing a SiC single crystal ingot as described in claim 27 or 28, wherein (diameter of the first space at the cross section) / (diameter of the second space at the cross section) is 0.65 or more and 0.76 or less.

30. A method for producing a SiC single crystal ingot according to any one of claims 27 to 29, wherein the diameter of the first space in the cross section is larger than the diameter of the SiC seed crystal.

31. A method for producing a SiC single crystal ingot according to any one of claims 27 to 30, wherein the crucible is rotatable.

32. A method for producing a SiC single crystal ingot described in any one of claims 27 to 31, wherein (height of the first space in the vertical direction) / (height of the raw material solution contained in the second space in the vertical direction) is 0.2 or more and 0.8 or less.

33. A method for producing a SiC single crystal ingot according to any one of claims 27 to 32, wherein the diameter of the SiC seed crystal is 6 inches or more.

34. A method for producing a SiC single crystal ingot according to any one of claims 27 to 33, wherein the standard deviation of the total thickness of the SiC seed crystal and the as-grown growth layer obtained in the growth step, measured at 2 mm intervals from the center toward the periphery, is 300 μm or less.

35. A method for producing a SiC single crystal ingot according to any one of claims 27 to 34, wherein the growth step produces a growth layer having a thickness of 1 mm or more.

36. A method for producing a SiC single crystal ingot according to any one of claims 27 to 35, wherein, when the temperature of the raw material solution at the interface between the raw material solution and the SiC seed crystal or the growth layer is a first temperature at a point facing the center of the SiC seed crystal or the growth layer and a second temperature at a point facing the periphery of the SiC seed crystal or the growth layer, in the growth process, the absolute value of the value obtained by dividing the temperature difference between the first temperature and the second temperature by the distance between the center and the periphery is 0.1 K / cm or less.

37. A method for producing a SiC single crystal ingot according to any one of claims 27 to 36, wherein the surface of the SiC seed crystal is flat.

38. A method for producing a SiC single crystal wafer, comprising the steps of: producing a SiC single crystal ingot by the method for producing a SiC single crystal ingot according to any one of claims 23 to 37; and slicing a SiC single crystal wafer from the SiC single crystal ingot.

39. An apparatus for manufacturing a SiC single crystal ingot, comprising: a crucible having a solution storage space surrounded by a bottom, a sidewall, and an opening facing the bottom, the solution storage space storing a raw material solution containing Si and C; a chamber accommodating the crucible; a pulling shaft to which a SiC seed crystal having a diameter of 4 inches or more is attached; and a heater for heating the raw material solution stored in the crucible, wherein the solution storage space of the crucible has a first space and a second space having different diameters in a cross section perpendicular to a height direction from the bottom to the opening, the first space and the second space being connected side by side in the height direction, and the diameter in the cross section of the first space located on the bottom side being smaller than the diameter in the cross section of the second space located on the opening side.

40. A SiC single crystal ingot manufacturing apparatus as described in claim 39, wherein (diameter of the first space at the cross section) / (diameter of the second space at the cross section) is 0.65 or more and 0.90 or less.

41. An apparatus for producing a SiC single crystal ingot as described in claim 39 or 40, wherein (diameter of the first space at the cross section) / (diameter of the second space at the cross section) is 0.65 or more and 0.76 or less.

42. An apparatus for producing a SiC single crystal ingot according to any one of claims 39 to 41, wherein the diameter of the first space in the cross section is larger than the diameter of the SiC seed crystal.

43. An apparatus for producing a SiC single crystal ingot according to any one of claims 39 to 42, wherein the crucible is rotatable.

44. A SiC single crystal ingot manufacturing apparatus described in any one of claims 39 to 43, wherein (height of the first space in the vertical direction) / (height of the raw material solution contained in the second space in the vertical direction) is 0.2 or more and 0.8 or less.

45. An apparatus for producing a SiC single crystal ingot according to any one of claims 39 to 44, wherein the diameter of the SiC seed crystal is 6 inches or more.

46. ​​The Cr concentration per surface area is 1 x 10 １５ atoms / cm ２ 1. A method for forming a SiC epitaxially grown film, comprising the steps of: forming a SiC epitaxial film on a SiC single crystal wafer having:

47. The Cr concentration per volume in the SiC epitaxially grown film is 1×10 １５ atoms / cm ３ 47. The method for forming a SiC epitaxially grown film according to claim 46, wherein:

48. The diameter of the SiC single crystal wafer is 4 inches or more, and the Cr concentration per volume is 1×10 １６ atoms / cm ３ 48. The method for forming an SiC epitaxially grown film according to claim 46 or 47.

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